Publications by authors named "Bruce J W Evans"

60 Publications

Referrals from community optometrists to the hospital eye service in England.

Ophthalmic Physiol Opt 2020 Dec 22. Epub 2020 Dec 22.

Division of Optometry and Visual Sciences, School of Health Sciences, City, University of London, London, UK.

Purpose: In the UK, most referrals to the hospital eye service (HES) originate from community optometrists (CO). This audit investigates the quality of referrals, replies, and communication between CO and the HES.

Methods: Optometric referrals and replies were extracted from three practices in England. If no reply letter was found, the records were searched at each local HES unit, and additional replies or records copied. De-identified referrals, replies and records were audited by a panel against established standards to evaluate whether the referrals were necessary, accurate and directed to the appropriate professional. The referral rate (RR) and referral reply rate (RRR) were calculated.

Results: A total of 459 de-identified referrals were extracted. The RR ranged from 3.6%-8.7%. The proportion of referred patients who were seen in the HES unit was 63%-76%. From the CO perspective, the proportion of referrals for which they received replies ranged from 26%-49%. Adjusting the number of referrals for cases when it would be reasonable to expect an HES reply, RRR becomes 38%-62%. Patients received a copy of the reply in 3%-21% of cases. Referrals were made to the appropriate service in over 95% of cases, were judged necessary in 93%-97% and were accurate in 81%-98% of cases. The referral reply addressed the reason for the referral in 93%-97% and was meaningful in 94%-99% of cases. The most common conditions referred were glaucoma, cataract, anterior segment lesions, and neurological/ocular motor anomalies. The CO/HES dyad (pairing) in the area with the lowest average household income had the highest RR.

Conclusions: In contrast with the Royal College of Ophthalmologists/College of Optometrists joint statement on sharing patient information, CO referrals often do not elicit a reply to the referring CO. Replies from the HES to COs are important for patient care, benefitting patients and clinicians, and minimising unnecessary HES appointments.
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http://dx.doi.org/10.1111/opo.12772DOI Listing
December 2020

Investigation of the efficacy of an online tool for improving the diagnosis of macular lesions imaged by optical coherence tomography.

J Optom 2020 Oct 29. Epub 2020 Oct 29.

Optometrist, Brooks and Wardman, Nottingham, UK.

Purpose: Optical coherence tomography (OCT) is a non-invasive method for diagnosis and monitoring of retinal (typically, macular) conditions. The unfamiliar nature of OCT images can present considerable challenges for some community optometrists. The purpose of this research is to develop and assess the efficacy of a novel internet resource designed to assist optometrists in using OCT for diagnosis of macular disease and patient management.

Methods: An online tool (OCTAID) has been designed to assist practitioners in the diagnosis of macular lesions detected by OCT. The effectiveness of OCTAID was evaluated in a randomised controlled trial comparing two groups of practitioners who underwent an online assessment (using clinical vignettes) based on OCT images, before (exam 1) and after (exam 2) an educational intervention. Participants' answers were validated against experts' classifications (the reference standard). OCTAID was randomly allocated as the educational intervention for one group with the control group receiving an intervention of standard OCT educational material. The participants were community optometrists.

Results: Random allocation resulted in 53 optometrists receiving OCTAID and 65 receiving the control intervention. Both groups performed similarly at baseline with no significant difference in mean exam 1 scores (p = 0.21). The primary outcome measure was mean improvement in exam score between the two exam modules. Participants who received OCTAID improved their exam score significantly more than those who received conventional educational materials (p = 0.005).

Conclusion: Use of OCTAID is associated with an improvement in the combined skill of OCT scan recognition and patient management decisions.
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http://dx.doi.org/10.1016/j.optom.2020.07.006DOI Listing
October 2020

Is reading rate in digital eyestrain influenced by binocular and accommodative anomalies?

J Optom 2020 Oct 25. Epub 2020 Oct 25.

Neville Chappell Research Clinic, Institute of Optometry, 56-62 Newington Causeway, London, SE1 6DS, UK; Division of Optometry & Visual Sciences, City, University of London, Northampton Square, London, EC1V 0HB, UK.

Introduction: Symptoms experienced when using digital devices are known as digital eyestrain (DES) or computer vision syndrome. They can be categorised as either external (associated with dry eye) or internal (related to refractive, accommodative or binocular vision anomalies). In a large cohort of adults with DES, we investigate the prevalence of binocular and accommodative anomalies, contrasting different diagnostic approaches, to evaluate potential mechanisms for the benefit from +0.75D addition lens that has been previously reported.

Methods: Participants (20-40y) were selected using the Computer Vision Syndrome Questionnaire (CVS-Q) tool as suffering with DES. A comprehensive eye examination was given to each participant, and this paper concentrates on "internal factors", detected with a refraction and comprehensive testing of binocular and accommodative functions. The effects of low-powered addition lenses (+0.50D, +0.75D, +1.25D; and plano controls) were assessed by double-masked testing with the Wilkins Rate of Reading Test (WRRT) and by subjective preference.

Results: As previously reported, most participants showed a subjective preference for one of the three convex lenses we used, with +0.75D chosen most frequently. Performance at the WRRT was significantly improved with +0.50D and +0.75D, but not +1.25D. Using a variety of diagnostic criteria, there were no strong associations between WRRT results or CVS-Q scores and any binocular or accommodation functions. The one finding of significance is that a disproportionate number of participants who benefited from adds had an eso-fixation disparity on the near Mallett unit, although this only affected 5% of the population.

Conclusions: DES is a collection of diverse symptoms that have a multifactorial aetiology. In the sample described here, binocular and accommodative anomalies do not seem to be a major cause of DES. Nevertheless, in view of the multifactorial aetiology it is recommended that patients with the symptoms of DES are assessed with a comprehensive eye examination. Patients with an esophoric fixation disparity on the near Mallett unit are particularly likely to benefit from near additions.
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http://dx.doi.org/10.1016/j.optom.2020.08.006DOI Listing
October 2020

Randomised controlled trial of corneal vs. scleral rigid gas permeable contact lenses for keratoconus and other ectatic corneal disorders.

Cont Lens Anterior Eye 2020 12 8;43(6):543-552. Epub 2020 Jan 8.

Institute of Optometry, 56-62 Newington Causeway, London, SE1 6DS, UK; London South Bank University, School of Health and Social Care, 103 Borough Rd, London, SE1 0AA, UK. Electronic address:

Purpose: To compare the comfort and visual performance of corneal rigid gas permeable contact lenses (CoL) and scleral rigid gas permeable contact lenses (SL) in participants with corneal ectasia, successfully wearing "habitual" CoL.

Methods: In a randomised controlled trial (RCT) with a 2 × 2 crossover, 34 participants were recruited and randomised into two groups. Group 1 (sequence AB), were fitted in period 1, with new CoL and after a 4-week washout period, in which habitual CoL were worn, were fitted with and crossed-over to SL, period 2. Group 2 (sequence BA), were first fitted with SL in period 1 and after a washout period of 4 weeks, crossed-over to new CoL, period 2. The median lengths in weeks of Periods 1 and 2 were: 17.5 (IQR 12.4) and 14.5 (IQR 6.2) respectively. The outcome measures for visual performance were best corrected visual acuity and the contrast sensitivity function. Vision related quality of life (Qol) was assessed using the National Eye Institute Visual Function Questioannaire-25 and reported subjective perception of vision (SPV) and reported subjective perception of comfort (SPC) scores, recorded on a scale from 1-10. The final outcome measure was the selection of the preferred lens type at the completion of the RCT.

Results: For the 30 who completed the trial, significantly higher SPC scores were found for SL compared to CoL (p = 0.002). Significantly higher SPC scores for CoL were found in participants who selected CoL as their preferred lens for future use, compared to those who selected SL (p = 0.009). All other outcomes exhibited no significant difference between the experimental lenses. There was no significant difference (p=0.86) in the proportion preferring CoL (53%) and SL (47%).

Conclusion: Significantly better comfort was reported for SL compared with CoL. Significantly higher comfort in CoL was found in those who preferred CoL, than those who preferred SL. Successful CoL wearers whose SPC in CoL is <7 are likely to achieve better comfort with SL. On average, successful CoL wearers found SL more comfortable and there are unlikely to be any significant visual or visual Qol advantage or disadvantage in refitting successful CoL wearers with keratoconus and other corneal ectasia disorders, with SL and vice versa.
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http://dx.doi.org/10.1016/j.clae.2019.12.007DOI Listing
December 2020

Does an iPad fixation disparity test give equivalent results to the Mallett near fixation disparity test?

J Optom 2019 Oct - Dec;12(4):222-231. Epub 2019 Sep 7.

Division of Pharmacy and Optometry, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK; Institute of Optometry, 56-62 Newington Causeway, London SE1 6DS, UK.

Background: Various instruments have been developed to measure aligning prism, the prism that eliminates a fixation disparity (associated heterophoria). This includes the established Mallett near vision unit and recently developed Thomson Vision Toolbox on the iPad. With no previous research investigating the agreement between these instruments, practitioners may question if they can be used interchangeably.

Methods: 80 participants underwent near vision testing with the Mallett unit and iPad fixation disparity test. Data were analysed in four ways to investigate the agreement of the two instruments.

Results: Many participants reported no fixation disparity (horizontally 46.25%, vertically 82.5%), or non-significant aligning prism (horizontally 70%, vertically 97.5%), on both instruments. The iPad revealed a larger range of aligning prism results horizontally, 6Δ base out to 15Δ base in; the Mallett unit produced a larger range of results vertically, 1Δ base up to 3.5Δ base down. More participants required a significant aligning prism on the Mallett unit horizontally and vertically. Wilcoxon signed rank analysis found that the difference in aligning prism was not statistically significant (p=0.357 horizontally, p=0.236 vertically), but 95% limits of agreement revealed clinically significant differences between the instruments.

Conclusion: Although the measured differences between the instruments are not significant in a Wilcoxon analysis, a Bland & Altman approach shows them to be in some cases clinically unacceptable, therefore the instruments should not be used interchangeably. Previous research indicates that the Mallett unit performs reasonably well at detecting symptomatic individuals and determining a prismatic correction that is likely to be helpful. Further research is required to determine the performance of the iPad test in these functions and to assess the reproducibility of both instruments.
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http://dx.doi.org/10.1016/j.optom.2019.03.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6978586PMC
May 2020

Sources of error in clinical measurement of the amplitude of accommodation.

J Optom 2020 Jan - Mar;13(1):3-14. Epub 2019 Jul 11.

Institute of Optometry, 56-62 Newington Causeway, London SE1 6DS, UK; School of Health and Social Care, London South Bank University, 103 Borough Road, London SE1 0AA, UK; Division of Optometry and Visual Science, School of Health Sciences, City, University of London, Northampton Square, London EC1V 0HB, UK.

Measurement of the amplitude of accommodation is established as a procedure in a routine optometric eye examination. However, clinical methods of measurement of this basic optical function have several sources of error. They are numerous and diverse, and include depth of focus, reaction time, instrument design, specification of the measurement end-point, specification of the reference point of measurement, measurement conditions, consideration of refractive error, and psychological factors. Several of these sources of inaccuracy are composed of multiple sub-sources, and many of the sub-sources influence the common methods of measurement of amplitude of accommodation. Consideration of these sources of measurement error casts doubt on the reliability of the results of measurement, on the validity of established normative values that have been produced using these methods, and on the value of reports of the results of surgery designed to restore accommodation. Clinicians can reduce the effects of some of the sources of error by modifying techniques of measurement with existing methods, but a new method may further improve accuracy.
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http://dx.doi.org/10.1016/j.optom.2019.05.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6951837PMC
June 2020

The impact of orthokeratology lens wear on binocular vision and accommodation: A short-term prospective study.

Cont Lens Anterior Eye 2018 12 14;41(6):501-506. Epub 2018 Sep 14.

School of Optometry and Vision Science, UNSW, Sydney, NSW, 2052, Australia; Faculty of Health and Social Care, London South Bank University, London, United Kingdom.

Purpose: To investigate the effects of short-term orthokeratology (OK) on accommodation and binocular visual function in young adults.

Methods: Twenty-four myopes (18 to 38 years) were fitted with OK lenses in both eyes. Best corrected distance visual acuity (VA), subjective and objective refractions, corneal topography and a series of binocular vision tests were measured at baseline (BL) before lens wear and then repeated after 28 nights of OK. Data from 15 subjects who demonstrated successful OK lens fit are reported.

Results: Corneal flattening and hyperopic shifts in spherical equivalent refractive error (all p < 0.001) after 28 nights of OK indicated myopic correction. Improvement in best corrected distance VA was measured after OK (right eye p = 0.021; left eye p = 0.014). Although there was no significant change in mean distance and near phorias and stereoacuity scores after OK compared to BL, there was a significant reduction in standard deviation (SD) and range of data (distance p = 0.01; near p = 0.02; stereoacuity p < 0.001). While there appeared to be an improvement in distance accommodative facility after OK, this failed to reach statistical significance (p = 0.053). Furthermore, there was no change in AC/A gradients with ±1 D and ±2 D lenses after OK compared to BL.

Conclusions: Binocular vision remained unchanged after OK, although variability of phoria and stereoacuity measures reduced. This suggests that OK improves or maintains accommodative and binocular vision function in young adult myopes who achieve good vision with OK. Myopes with phorias outside normal ranges and/or poor distance accommodative facility may benefit most with OK, in binocular and accommodative function.
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http://dx.doi.org/10.1016/j.clae.2018.08.002DOI Listing
December 2018

A Review of Depth of Focus in Measurement of the Amplitude of Accommodation.

Vision (Basel) 2018 Sep 6;2(3). Epub 2018 Sep 6.

Institute of Optometry, 56-62 Newington Causeway, London SE1 6DS, UK.

The aim of this review is to investigate the role of depth of focus (DoF) as a potential confounding variable in the measurement of the amplitude of accommodation (AoA). The role of DoF in human vision is briefly summarised, and it is noted that the prevalent method of measuring AoA is the push-up method. Factors influencing the effect of DoF on the push-up and other methods of measuring AoA are reviewed in detail. DoF is shown to add substantial measurement error in the routine assessment of accommodation when the AoA is measured by methods involving subjective judgement of an object's clarity. Reliable compensation for this source of error is not realistically possible because of the complexity of the aetiology of DoF, and its inter-individual and intra-individual variation. The method of measurement also influences the extent of the error. It is concluded that methods of measurement of AoA that exclude DoF should be preferred.
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http://dx.doi.org/10.3390/vision2030037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835437PMC
September 2018

The relationship between unwarranted variation in optometric referrals and time since qualification.

Ophthalmic Physiol Opt 2018 09 2;38(5):550-561. Epub 2018 Sep 2.

School of Health and Social Care, London South Bank University, London, UK.

Purpose: To investigate variation in optometric referral decision-making and the influence of experience and continuing education and training (CET).

Methods: To gain insight into unwarranted variation in referral activity in the United Kingdom (UK): (1) triage data were audited to investigate source of referral, provisional diagnosis, and outcome; (2) an online system was developed to present two sets of 10 vignettes, designed to avoid prompting answers. Participating optometrists completed 10 pre-CET vignettes, recording their tests and management decisions. The main group of participants chose whatever CET they wished over a 6-month period and then completed another 10 post-CET vignettes. A second group of newly-qualified optometrists completed the vignettes before and after a CET course intervention, followed by a third group of pre-registered optometrists with an intervention of 6-months experience of their pre-registration year.

Results: The audit identified 1951 optometric referrals and 158 optometrists (211 referrals were from general medical practitioners), with 122 of the 158 optometrists making fewer than ten referrals. Two newly-qualified optometrists generated 12.5% of the total referrals in the audit (N = 2162). Many suspect glaucoma referrals were based on a single suspect measurement resulting in a high discharge rate after community review, as did referrals for certain fundus-related appearances for which no treatment was indicated. The intervention of gaining CET points appeared to have no significant impact (p = 0.37) on referral decision-making, although this part of the study was underpowered. Self-selection bias was confirmed in the main group. When the main group and newly-qualified practitioners were compared, the number of referrals was negatively associated with time since qualification (p = 0.005). When all 20 referral decisions were compared, all optometrists referring more than 10 vignette patients came from a group of newly-qualified practitioners up to 2 years post-qualification. Pre-registered optometrists generally referred more appropriately than newly-qualified. Upon qualification, there was a significant increase in the number of sight tests undertaken per day (p = <0.0005).

Conclusions: Gaining CET points alone is unlikely to significantly improve referral decision-making. Mentoring and targeted CET for the newly-qualified up to 2 years post-qualification should be considered. Ophthalmology replies to the referring newly-qualified optometrist are vital for moderating future referrals and developing clinical confidence.
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http://dx.doi.org/10.1111/opo.12580DOI Listing
September 2018

Coloured filters and visual stress.

Ophthalmic Physiol Opt 2018 03;38(2):203-204

Department of Vision and Hearing Sciences and Vision and Eye Research Unit, Anglia Ruskin University, Cambridge, UK.

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http://dx.doi.org/10.1111/opo.12432DOI Listing
March 2018

Reply to Letter to the Editor by Griffiths et al. commenting on Evans & Allen.

J Optom 2017 Jul - Sep;10(3):200-202. Epub 2017 May 9.

Department of Vision and Hearing Sciences and Vision and Eye Research Unit, Anglia Ruskin University, Cambridge, UK.

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http://dx.doi.org/10.1016/j.optom.2017.05.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5484782PMC
May 2017

Coloured filters and reading: reasons for an open mind.

Authors:
Bruce J W Evans

Ophthalmic Physiol Opt 2017 01 1;37(1):105-107. Epub 2016 Dec 1.

Neville Chappell Research Clinic, Institute of Optometry, London, UK.

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http://dx.doi.org/10.1111/opo.12330DOI Listing
January 2017

A Delphi study to develop practical diagnostic guidelines for visual stress (pattern-related visual stress).

J Optom 2017 Jul - Sep;10(3):161-168. Epub 2016 Nov 24.

University of Essex, Department of Psychology, Colchester, UK.

Purpose: Visual stress (VS) is characterised by symptoms of visual perceptual distortions and eyestrain when viewing text, symptoms that are alleviated by individually prescribed coloured filters. A recent review supports the existence of VS and its treatment, but noted that controversy remains, in part due to inconsistencies in the diagnosis of the condition. The present paper reviews the diagnostic criteria for VS in the literature and reports a Delphi analysis of the criteria currently used in clinical practice.

Methods: Twenty-six eyecare practitioners were invited to participate in a Delphi study. They were selected because they were frequent prescribers of precision tinted lenses. In the first round they were sent a list of the indicators for which there is literature to suggest a relevance in the diagnosis of VS. The practitioners were invited to rank the indicators and add any additional criteria they use in diagnosis. In the second round a revised list was circulated, including items added from the responses in the first round.

Results: The respondents included optometrists, orthoptists and opticians. In the first round the response rate was 85%. Ninety-one percent of those who participated in the first round also responded in the second round. Strong indicators in the second round included the symptom of words moving when reading, voluntary use of an overlay for a prolonged period, improved performance of ≥15% with an overlay on the Wilkins Rate of Reading test, and an abnormally high score on the Pattern Glare Test.

Conclusions: The strongest diagnostic criteria are combined in a diagnostic tool. This is proposed as a guide for clinical practice and further research.
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http://dx.doi.org/10.1016/j.optom.2016.08.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5484780PMC
March 2018

Does Gender Influence Colour Choice in the Treatment of Visual Stress?

PLoS One 2016 20;11(9):e0163326. Epub 2016 Sep 20.

Division of Optometry and Visual Science, School of Health Sciences, City, University of London, London, United Kingdom.

Purpose: Visual Stress (VS) is a condition in which words appear blurred, in motion, or otherwise distorted when reading. Some people diagnosed with VS find that viewing black text on white paper through coloured overlays or precision tinted lenses (PTLs) reduces symptoms attributed to VS. The aim of the present study is to determine whether the choice of colour of overlays or PTLs is influenced by a patient's gender.

Methods: Records of all patients attending a VS assessment in two optometry practices between 2009 and 2014 were reviewed retrospectively. Patients who reported a significant and consistent reduction in symptoms with either overlay and or PTL were included in the analysis. Overlays and PTLs were categorized as stereotypical male, female or neutral colours based on gender preferences as described in the literature. Chi-square analysis was carried out to determine whether gender (across all ages or within age groups) was associated with overlay or PTL colour choice.

Results: 279 patients (133 males and 146 females, mean age 17 years) consistently showed a reduction in symptoms with an overlay and were included. Chi-square analysis revealed no significant association between the colour of overlay chosen and male or female gender (Chi-square 0.788, p = 0.674). 244 patients (120 males and 124 females, mean age 24.5 years) consistently showed a reduction in symptoms with PTLs and were included. Chi-square analysis revealed a significant association between stereotypical male/female/neutral colours of PTLs chosen and male/female gender (Chi-square 6.46, p = 0.040). More males preferred stereotypical male colour PTLs including blue and green while more females preferred stereotypical female colour PTLs including pink and purple.

Conclusions: For some VS patients, the choice of PTL colour is influenced not only by the alleviation of symptoms but also by other non-visual factors such as gender.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5029909PMC
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0163326PLOS
August 2017

A systematic review of controlled trials on visual stress using Intuitive Overlays or the Intuitive Colorimeter.

J Optom 2016 Oct-Dec;9(4):205-18. Epub 2016 Jul 11.

Department of Vision and Hearing Sciences and Vision and Eye Research Unit, Anglia Ruskin University, Cambridge, UK.

Claims that coloured filters aid reading date back 200 years and remain controversial. Some claims, for example, that more than 10% of the general population and 50% of people with dyslexia would benefit from coloured filters lack sound evidence and face validity. Publications with such claims typically cite research using methods that have not been described in the scientific literature and lack a sound aetiological framework. Notwithstanding these criticisms, some researchers have used more rigorous selection criteria and methods of prescribing coloured filters that were developed at a UK Medical Research Council unit and which have been fully described in the scientific literature. We review this research and disconfirm many of the more extreme claims surrounding this topic. This literature indicates that a minority subset of dyslexics (circa 20%) may have a condition described as visual stress which most likely results from a hyperexcitability of the visual cortex. Visual stress is characterised by symptoms of visual perceptual distortions, headaches, and eyestrain when viewing repetitive patterns, including lines of text. This review indicates that visual stress is distinct from, although sometimes co-occurs with, dyslexia. Individually prescribed coloured filters have been shown to improve reading performance in people with visual stress, but are unlikely to influence the phonological and memory deficits associated with dyslexia and therefore are not a treatment for dyslexia. This review concludes that larger and rigorous randomised controlled trials of interventions for visual stress are required. Improvements in the diagnosis of the condition are also a priority.
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http://dx.doi.org/10.1016/j.optom.2016.04.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5030324PMC
April 2017

Sunglass Filter Transmission and Its Operational Effect in Solar Protection for Civilian Pilots.

Aerosp Med Hum Perform 2016 May;87(5):436-42

Introduction: The ocular effects of excess solar radiation exposure are well documented. Recent evidence suggests that ocular ultraviolet radiation (UVR) exposure to professional pilots may fall outside international guideline limits unless eye protection is used. Nonprescription sunglasses should be manufactured to meet either international or national standards. The mean increase in UVR and blue light hazards at altitude has been quantified and the aim of this research was to assess the effectiveness of typical pilot sunglasses in reducing UVR and blue light hazard exposure in flight.

Method: A series of sunglass filter transmittance measurements were taken from personal sunglasses (N = 20) used by pilots together with a series of new sunglasses (N = 18).

Results: All nonprescription sunglasses measured conformed to international standards for UVR transmittance and offered sufficient UVR protection for pilots. There was no difference between right and left lenses or between new and used sunglasses. All sunglasses offered sufficient attenuation to counter the mean increase in blue light exposure that pilots experience at altitude, although used sunglasses with scratched lenses were marginally less effective. One pair of prescription sunglasses offered insufficient UVR attenuation for some flights, but would have met requirements of international and national standards for UV-A transmittance. This was likely due to insufficient UVR blocking properties of the lens material.

Conclusions: Lenses manufactured to minimally comply with standards for UVR transmittance could result in excess UVR exposure to a pilot based on in-flight irradiance data; an additional requirement of less than 10% transmittance at 380 nm is recommended.
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http://dx.doi.org/10.3357/AMHP.4499.2016DOI Listing
May 2016

Occupational Ocular UV Exposure in Civilian Aircrew.

Aerosp Med Hum Perform 2016 Jan;87(1):32-9

Medical Division, UK Civil Aviation Authority, Safety Regulation Group, West Sussex, UK.

Introduction: Ultraviolet radiation (UVR) increases with altitude; however, there are a number of other factors which may influence ocular exposure during flight. The aim of this study was to assess ocular UVR exposure of pilots in airline and off-shore helicopter operations on different aircraft types and to compare with exposure in a typical office environment.

Method: In-flight data were captured on equipment including a CCD array spectroradiometer on five return sector European airline flights and one transatlantic flight from London Gatwick in addition to four helicopter flights from Aberdeen Dyce airport. Further data were collected in an office environment from three workstations during summer and winter months.

Results: A wide variation in ocular UVA dose was found during flights. The main factor influencing exposure was the UVR transmission of the windshield, which fell into two distinct profile types. In an aircraft with good UVA blocking properties, ocular exposure was found to be equivalent to office exposure and did not exceed international guideline limits regardless of external conditions or flight time. Most aircraft assessed had poor UVA blocking windshields which resulted in an ocular exposure to the unprotected eye in excess of international guideline limits (up to between 4.5 to 6.5 times greater during one flight). No significant UVB dose was found.

Discussion: Pilots should be warned of the potential high UVA exposure during flight and advised on the use of sunglasses. A windshield labeling system would allow the pilot to tailor their eye protection practices to that particular aircraft.
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http://dx.doi.org/10.3357/AMHP.4404.2016DOI Listing
January 2016

Solar Eye Protection Practices of Civilian Aircrew.

Aerosp Med Hum Perform 2015 Nov;86(11):953-61

Civil Aviation Authority, West Sussex, UK.

Introduction: There is good evidence that long term exposure to ultraviolet (UV) radiation increases the risk of cataracts. The 'blue light hazard' is considered a risk factor for retinal changes similar to those seen in macular degeneration. Previous studies ascertaining the prevalence of radiation related ocular disease in pilot cohorts have not considered use of solar eye protection. The aim of this study was to explore pilot use of sunglasses and other solar eye protection habits and to gain insight into the difficulties encountered managing sunlight on the flight deck. Additionally, the prevalence of radiation related ocular pathology in the study group was calculated.

Methods: A web based questionnaire was developed and administered to a large population of current UK professional pilots.

Results: There were 2917 respondents who completed the questionnaire, demonstrating a wide range of sunglass use during flight. A number of barriers to sunglass use were identified, the most prevalent being the requirement for corrective lenses to be used. Pilots most commonly increase sunglass use due to ocular health concerns. A high level of dissatisfaction with standard aircraft sun protection systems was reported. Long haul airline pilots were the highest users of nonstandard sunlight blocking strategies. No correlation between reported pathology and flying experience was found.

Discussion: The use of sunglasses during flight is complex; however, a number of practical recommendations can be made to increase the success for those pilots who wish to use sunglasses more. Aircraft manufacturers should consider how greater control of cockpit sunlight levels can be achieved.
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http://dx.doi.org/10.3357/AMHP.4357.2015DOI Listing
November 2015

Repeatability and comparison of clinical techniques for anterior chamber angle assessment.

Ophthalmic Physiol Opt 2015 Mar;35(2):170-8

Ophthalmology, St Thomas' Hospital, London, SE1 7EH, UK; Institute of Optometry, Neville Chappell Research Clinic, London, SE1 6DS, UK; London South Bank University, Faculty of Health and Social Care, London, SE1 0AA, UK.

Purpose: To assess the repeatability of gonioscopy, van Herick method and anterior segment Optical Coherence Tomography (AS-OCT) and determine the agreement between these techniques within a community optometry setting.

Methods: Gonioscopy, van Herick method and AS-OCT imaging were performed by an optometrist on two occasions, 1 month apart, on 80 subjects aged over 40 years recruited from community optometry practices. Anterior segment images were captured with a spectral domain OCT (Topcon 3D OCT-2000; wavelength 840 nm) set to the Anterior Segment (AS) mode. Eyes were graded as open or occludable for each method. AS-OCT images from both visits were graded by a second optometrist masked to the gonioscopy and van Herick method results, and the visit on which the images were acquired. Cohen's kappa (κ) was used to describe the intra-observer repeatability. Likelihood ratios, sensitivity and specificity of van Herick method and AS-OCT were calculated, using gonioscopy as the reference standard.

Results: Measurements were obtained from 80 eyes of 80 subjects. In four cases, AS-OCT images were un-gradable due to difficulty in locating the scleral spur. The repeatability of gonioscopy was fair κ = 0.29, while that of the van Herick method (κ = 0.54) and AS-OCT (κ = 0.47) were somewhat better. The van Herick method showed good sensitivity (visit 1: 75%, visit 2: 69%) and high specificity (visit 1: 88%, visit 2: 96%). The sensitivity of AS-OCT was fair (visit 1: 46%, visit 2: 25%), but specificity was high (visit 1: 87%. visit 2: 89%).

Conclusion: Intra-observer repeatability was better for van Herick method and for AS-OCT than for gonioscopy, despite the latter being considered the gold standard method. The van Herick method appeared to be more sensitive than AS-OCT when identifying eyes at risk of angle closure. A standalone anterior segment OCT with a longer wavelength laser could afford better visualisation of the angle, and might therefore be expected to enable the examiner to make more precise classifications. These instruments are not widely used by optometrists in clinical practice in the UK at present.
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http://dx.doi.org/10.1111/opo.12200DOI Listing
March 2015

Coloured filters may reduce symptoms of dyslexia in those with visual stress.

BMJ 2014 Sep 30;349:g5882. Epub 2014 Sep 30.

Department of Vision and Hearing Sciences and Vision and Eye Research Unit, Anglia Ruskin University, Cambridge CB1 1PT, UK.

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http://dx.doi.org/10.1136/bmj.g5882DOI Listing
September 2014

Manufacturer changes lead to clinically important differences between two editions of the TNO stereotest.

Ophthalmic Physiol Opt 2014 Mar 19;34(2):243-9. Epub 2013 Dec 19.

Damme Optometrie, Kesteren, The Netherlands; Department of Optometry, Hogeschool Utrecht, University of Applied Science, Utrecht, The Netherlands; City University London, London, UK.

Purpose: Stereoacuity tests used in clinical practice should be repeatable and reproducible. However, it has been observed in a clinical setting that new editions of the TNO stereotest appear to give different values from those obtained using previous versions. The purpose of the present research was to investigate this observation.

Methods: One hundred and twenty-one Dutch subjects, 88 (73%) females and 33 (27%) males, with an average age of 34.0 years (range 18-55) had their stereoacuity measured using two different versions of the TNO stereoacuity test (TNO 13 and TNO 15). The TNO was tested in a counterbalanced order so that consecutive subjects started with alternate editions to avoid bias.

Results: There was a significant difference (p < 0.001) between the median value for stereoacuity measured with TNO 13 (30 s of arc) and TNO 15 (60 s of arc). The bias between the two test versions was -0.23 Log arcseconds (95% limits of the differences: 0.15 to -0.60 Log arcseconds).

Conclusion: This study reveals that results obtained with two different editions of a commonplace stereoacuity test are not comparable. New versions come on the market at regular intervals and the assumption that they will give the same results as previous versions may not be valid. Besides the statistically significant difference between the TNO 13 and TNO 15, the Bland-Altman plot also showed a considerable bias and the 95% limits of the differences between the TNO 13 and TNO 15 are more than two steps on the Log arcsecond scale. This difference between two editions of the TNO stereotests is not clinically acceptable and therefore it is inappropriate to use the two versions of the test interchangeably. It is important in both research and clinical records to specify the edition of the TNO test used.
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http://dx.doi.org/10.1111/opo.12101DOI Listing
March 2014

A comparison of in-air and in-saline focimeter measurement of the back vertex power of spherical soft contact lenses.

Ophthalmic Physiol Opt 2012 Nov 7;32(6):508-17. Epub 2012 Sep 7.

Department of Optometry & Visual Science, City University, London, UK.

Purpose: To compare the repeatability and validity of measurements of the back vertex power (BVP) of spherical soft contact lenses made in-air using the method specified in the International Standard (ISO 18369-3:2006) with the corresponding values when BVP was calculated from measurements made using a wet cell and focimeter method that is not approved by this Standard.

Methods: The BVP of 20 hydrogel and 20 silicone hydrogel lenses, with labelled powers ranging from +8.00 to -12.00 D, were measured with a focimeter by two operators on two occasions in-air in accordance with the relevant International Standard. Equivalent sets of measurements were made with the lenses immersed in-saline within a wet cell and their BVPs in-air were calculated. The validity of each method was assessed by comparing their results with an instrument that used the Hartmann method.

Results: The reliability results were generally a little better for the in-saline measurements than for the in-air measurements, although all reliability data demonstrated absolute values of mean errors (inter-operator and inter-session) that were <0.05 D for hydrogel lenses and <0.07 D for silicone hydrogel lenses. The in-air 95% confidence intervals were <0.45 D and <0.40 D for hydrogel and silicone hydrogel lenses, respectively and in-saline <0.39 and <0.31 D for hydrogel and silicone hydrogel lenses, respectively. The validity data revealed a relationship between measurement error and BVP for the in-air data (the focimeter overestimates the power of high plus and high minus lenses compared with the Hartmann instrument) and possibly a more complex relationship for the in-saline data. The 95% limits of agreement indicate better agreement for the in-saline validity data (-0.55 to +0.48 D for hydrogel lenses and -0.42 to +0.54 D for silicone hydrogel lenses) than those obtained in-air (-0.64 to +0.68 D for hydrogel lenses and -0.57 to +0.44 D for silicone hydrogel lenses).

Conclusions: Using equipment readily available in a clinical setting, the wet cell method of measurement of the BVP of spherical soft contact lenses has been shown to provide results for reliability and validity that were at least as good as those obtained with the in-air method approved by the International Standard.
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http://dx.doi.org/10.1111/j.1475-1313.2012.00932.xDOI Listing
November 2012

The development & evaluation of two vision screening tools for correctable visual loss in older people.

Ophthalmic Physiol Opt 2012 Jul 1;32(4):332-48. Epub 2012 Jun 1.

Institute of Optometry, The Neville Chappell Research Clinic, Newington Causeway, London, UK.

Objectives: In the UK, 20-50% of older people have undetected reduced vision and in most cases this results from correctable problems (refractive error and cataract). Many older people are not availing themselves of state-funded community optometric care. We assessed the efficacy of two vision screening instruments at detecting correctable visual problems and investigated the effect of optometric intervention on quality of life.

Methods: A computerised vision screener (CVS) was developed and refined after a preliminary study of 180 older people to include tests of: monocular presenting distance high contrast and low contrast visual acuities (VAs), binocular near acuities, and monocular visual fields. The modified CVS and a flip-chart vision screener (FVS) were evaluated on a second sample of 200 people aged 65+ (mean age 77 years). All participants in both studies were given an optometric eye examination, including high and low contrast VAs, refraction, binocular vision tests, tonometry, automated perimetry, and dilated fundoscopy including cataract grading and ARM grading. The target conditions were significant gain in monocular distance VA or binocular near VA with new refractive correction, significant cataract, or macular degeneration at risk of rapid progression. The Low Vision Quality of Life Questionnaire (LVQoL) was administered before and up to 3 months after testing.

Results: For the CVS, the best sensitivity (80.3%, 95% CI 72.4-86.4; specificity 66.7%, 95% CI 55.6-76.1) was obtained for a screener test combination of a fail on high contrast VA (>0.19 LogMAR) OR low contrast VA (>0.39 LogMAR) OR near VA (>N11.9). A screener test combination of high contrast VA OR near VA gave sensitivity of 79.5% (71.5-85.7) and specificity 67.9% (57-77.3). For the FVS, the best sensitivity was obtained for a test combination of a fail on high contrast VA OR low contrast VA OR near VA (sensitivity 82%, 95% CI 74.2-87.8; specificity 61.5%, 95% CI 50.4-71.6). A screener test combination of low contrast VA alone gave sensitivity of 75.4% (67.1-82.2) and specificity 76.9% (66.4-84.9). Significant improvements in LVQoL were found, with a significant correlation between gain in VA with new spectacles and improvement in LVQoL.

Conclusions: The vision screeners are effective tools for detecting those with reduced vision. Further work is required to determine their effectiveness as a tool for encouraging older people to engage in regular eyecare.
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http://dx.doi.org/10.1111/j.1475-1313.2012.00919.xDOI Listing
July 2012

Civilian pilot exposure to ultraviolet and blue light and pilot use of sunglasses.

Aviat Space Environ Med 2011 Sep;82(9):895-900

Civil Aviation Authority, West Sussex, UK, and London South Bank University, London, UK.

Population and animal studies indicate that long-term exposure to short-wavelength visible light and ultraviolet (UV) radiation causes increased risk of certain ocular pathologies such as cataracts and maculopathy. The potential risk to flight crew is unknown. The UK Civil Aviation Authority (CAA) has issued guidance to pilots regarding sunglass selection; however, it is not known if this guidance is appropriate given pilots' unique occupational environment. A search and appraisal of the relevant literature was conducted which showed that within the airline pilot population, there is limited evidence of a higher prevalence of cataracts. There are no data of other known UV-related ocular pathology. There is some evidence of higher prevalence of skin melanomas. Studies measuring cockpit UV radiation levels are limited and leave unanswered questions regarding airline pilot exposure. Data from optical transmission of cockpit windshields demonstrates the UV blocking properties at sea level. No studies have addressed the occupational use of sunglasses in airline pilots. Although it is likely that an aircraft windshield effectively blocks UV-B, the intensity of UV-A and short wavelength blue light present within the cockpit at altitude is unknown. Pilots may be exposed to solar radiation for periods of many hours during flight where UV radiation is known to be significantly greater. Aircraft windshields should have a standard for optical transmission, particularly of short-wavelength radiation. Clear, untinted prescription glasses will offer some degree of UV protection; however, sunglasses will offer superior protection. Any sunglasses used should conform to a national standard.
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http://dx.doi.org/10.3357/asem.3034.2011DOI Listing
September 2011

Randomised controlled trial of intermittent photic stimulation for treating amblyopia in older children and adults.

Ophthalmic Physiol Opt 2011 Jan;31(1):56-68

Neville Chappell Research Clinic, Institute of Optometry, London, UK.

The treatment of amblyopia is reviewed and it is noted that in addition to conventional 'passive treatment' in children with occlusion, it has been argued that 'active treatment' may be effective in older children and adults. Intermittent photic stimulation (IPS) is one such active treatment. In Study 1, we report a clinical audit of 21 patients treated with IPS, which demonstrated that the maximum improvement is reached after 6 half hour sessions. Study 2 is a double-masked randomised controlled trial comparing IPS with a control treatment in 30 participants aged 10-57 years. Using a sensitive staircase measure of visual acuity (VA), the IPS group improved by about one line (p = 0.0053). The mean improvement was significantly greater (unpaired t-test, p = 0.022) in the IPS group (mean 0.096; S.E.M. 0.029) than in the control group (mean 0.019; S.E.M. 0.022). The improvement occurred in participants with strabismic amblyopia, but not in those with anisometropic amblyopia. Follow up data after about 1 year showed that VA had regressed to pre-treatment levels. The results are discussed within the context of another development in active amblyopia therapy, perceptual learning. The literature on this therapy reveals improvements in VA of about 2.5 lines in older children and adults with anisometropic amblyopia. It is concluded that perceptual learning is likely a better treatment option than IPS for anisometropic amblyopes, and probably also for strabismic amblyopes although a randomised controlled trial is required. It is noted that the existence of effective treatments for adults does not detract from the need to treat amblyopia in younger children.
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http://dx.doi.org/10.1111/j.1475-1313.2010.00801.xDOI Listing
January 2011

An exploration of the initial effects of stereoscopic displays on optometric parameters.

Ophthalmic Physiol Opt 2011 Jan;31(1):33-44

Department of Optometry, Utrecht University of Applied Science, Hogeschool Utrecht, Utrecht, the Netherlands.

Purpose: To compare the effect on optometric variables of reading text presented in 2-D and 3-D on two types of stereoscopic display.

Methods: This study measured changes in binocular visual acuity, fixation disparity, aligning prism, heterophoria, horizontal fusional reserves, prism facility and accommodation responses for near of subjects after completing ten consecutive reading tasks of 1 minute each. The tasks consisted of reading words on a polarized two-view (n = 39) and an auto-stereoscopic lenticular nine-view display (n = 19) with the text presented without or with stereoscopic disparity at 3 m. Performance was assessed by measuring reading speed and symptoms were rated by the Convergence Insufficiency Symptom Survey (CISS) questionnaire.

Results: With both types of display, CISS scores at least doubled immediately after subjects viewed the 3-D text image in an extreme stereoscopic condition compared to the 2-D condition (p < 0.001), while the mean reading speed slowed (p < 0.001). Mean changes in optometric test variables were not clinically or statistically significant (p values > 0.05). After the 3-D task one participant showed consistent clinically meaningful decreases in convergent fusional break and recovery points for both displays.

Conclusion: When healthy adult subjects with normal binocular vision viewed text images at 3 m in extreme 3-D display settings for a short period of time there were no clinically significant mean changes in optometric test variables compared with 2-D viewing.
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http://dx.doi.org/10.1111/j.1475-1313.2010.00804.xDOI Listing
January 2011

A comparison of standardised patients, record abstraction and clinical vignettes for the purpose of measuring clinical practice.

Ophthalmic Physiol Opt 2010 May;30(3):209-24

The Neville Chappell Research Clinic, The Institute of Optometry, Newington Causeway, London.

Background: A recent review found standardised patient (SP) methodology to be the gold standard method for evaluating clinical care. Alternative methods include record abstraction and computerised clinical vignettes. SPs were compared to clinical records and to computerised vignettes in order to assess whether record abstraction and vignettes are accurate measures of clinical care provided within optometry.

Methods: A total of 111 community optometrists in the south east of the UK consented to be visited by unannounced actors for an eye examination. The SPs received extensive training to enable accurate reporting of the content of the eye examinations using checklists. Clinical records were requested from optometrists who chose to receive feedback following the SP visits. The SP checklists were used as a guide to extract relevant information from the clinical records. An opportunity was made available to all UK qualified optometrists, through publicity in the College of Optometrists' monthly newsletter, the Association of Optometrists' monthly newsletter (Blink) and the UK optometry e-mail discussion list to complete three computerised clinical vignettes by performing a virtual eye examination using an on-line optometric record card. The average differences were calculated between the record abstraction and vignette results compared to the standardised patient encounter findings for different domains of an eye examination. Chi-square analyses were performed on the tests which were of the greatest clinical significance for each scenario.

Results: The average overall difference for information gathered from record abstraction compared to the standardised patient encounter ranged from +2 to -26% (positive values indicate items that were recorded on the clinical records but not reported by the SP). For history and symptoms, the average difference ranged from -9 to -26%; for the proportion of tests performed during the examination this value ranged from +2 to -24% and for management issues the difference ranged from -1 to -4%. The average overall difference for the vignette data compared to the standardised patient encounter ranged from 0 to +26% (positive values indicate items that were not carried out in a clinical setting, as recorded by the SP, but were described by optometrists who completed the vignette as tests they would have carried out). For history and symptoms, the average difference for the vignette data ranged from +2 to +26%; from 0 to +20% for tests performed during the eye examination and from 0 to +11% for management.

Conclusion: Different methods of measuring clinical care capture different elements of clinical practice and are prone to different biases. This three-way comparison indicates that clinical records tend to under-estimate actual care provided, while vignette scores tend to over-estimate clinical performance. Low participation rates mean that the participating optometrists could be described as a 'self-selected sample'. This is a limitation of the research and the conclusions should be considered with this in mind. The significance of these findings for future research and for litigation and disciplinary cases is discussed.
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http://dx.doi.org/10.1111/j.1475-1313.2010.00713.xDOI Listing
May 2010

Provision of NHS-funded spectacles in South London.

Ophthalmic Physiol Opt 2009 Nov 26;29(6):641-7. Epub 2009 Aug 26.

The Neville Chappell Research Clinic, The Institute of Optometry, 56-62 Newington Causeway, London.

Background: In the UK the National Health Service (NHS) funds primary eyecare in the form of General Ophthalmic Services (GOS) mostly via 'sight tests' with community optometrists. Eligible groups include those aged 60 years or more and many are also entitled to an NHS optical voucher to be used to fund spectacles. Only some optical practices provide spectacles whose cost is fully covered by the voucher value which we describe as voucher value spectacles (VVS). As part of a larger study investigating vision screening in the older population, we sought to investigate the proportion of practices that provide VVS.

Methods: A questionnaire was sent to all optical practices in South London and also a more national sample of optometrists using the UK optometry e-mail discussion list.

Results: All 75 respondents provide NHS sight tests. VVS were provided by 59% of the total sample (70% of the South London sample). For those who supply VVS, the number of frames that were provided for patients to choose from ranged from 1 to 100, with a median of 16.5. Of those practitioners who did not supply VVS, 13% provided spectacles whose lens cost was fully covered by the NHS Voucher.

Discussion: In South London nearly a third of the practices do not provide VVS and it has been suggested that this is because the voucher values are uneconomic. The limited availability of VVS may act as one of the barriers that result in so many older people in the UK having poor vision simply through lack of appropriate spectacles.
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http://dx.doi.org/10.1111/j.1475-1313.2009.00686.xDOI Listing
November 2009

Randomised controlled trial of the effects of two rigid gas permeable (RGP) contact lens materials and two surface cleaners on straylight values.

Ophthalmic Physiol Opt 2009 Sep;29(5):497-508

Department of Optometry, University of Applied Science, Hogeschool Utrecht, Utrecht, CJ, The Netherlands.

Purpose: In a double-masked randomized controlled crossover study we investigated both the retinal responses to straylight, and the effects of lens cleaners on straylight values, in two different RGP contact lens materials.

Methods: Thirty patients (20-59 years) wearing RGP lenses were refitted with new lenses made of Boston XO material in one eye and made of Comfort O2 (ONSI-56) material in the other eye. Reported wetting angles for the Boston XO material (103 degrees ) and for the ONSI-56 material (7.2 degrees ) were obtained by sessile drop measurements. After refitting, the study comprised three 5-week trial periods. In Period 1 half of the participants (Group A) wore Boston XO lenses in their right eye and Comfort O2 (ONSI-56) lenses in their left eye, and the other half (Group B) vice versa. In Period 2 Group A wore Comfort O2 (ONSI-56) lenses in their right eye and Boston XO lenses in their left, and Group B vice versa. All participants used Miraflow cleaner during periods 1 and 2. In Period 3, during which all participants used Boston cleaner, Group A wore Boston XO lenses in their right eye and Comfort O2 (ONSI-56) lenses in their left eye and Group B vice versa. Straylight data (log S) were obtained with and without contact lenses using the Oculus C-Quant straylight meter in all three periods. Central corneal thickness (CCT) was measured in the second and third periods.

Results: When not wearing lenses (n = 60 eyes) at the end of the second 5 week trial period straylight was measured twice with averages of 1.07 log S, and the corrected CCT measurements averaged 546 mum. Straylight values with Comfort O2 (ONSI-56) reached 1.15 log S at the end of both the second (n = 25 eyes) and third periods (n = 23 eyes). Straylight values with Boston XO were 1.17 log S (n = 26 eyes) at the end of the second period, and 1.16 log S (n = 25 eyes) at the end of the third period.

Conclusions: Existing RGP lens wearers refitted with new lenses with different contact angles, made of Boston XO and Comfort O2 (ONSI-56) showed, over three 5 week periods, relatively small increases in straylight, which were functionally comparable, irrespective of the type of lens material or lens cleaner used. At every visit, straylight values and CCTs returned to baseline levels after RGP lens removal, confirming that the straylight fluctuations were mainly due to scattering from the RGP lenses; or tear film interaction; or a combination of both.
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http://dx.doi.org/10.1111/j.1475-1313.2009.00660.xDOI Listing
September 2009

Investigation of the causes of non-tolerance to optometric prescriptions for spectacles.

Ophthalmic Physiol Opt 2010 Jan 3;30(1):1-11. Epub 2009 Aug 3.

Eyesite Optometrists, 142 Friar Street, Reading, Berkshire, UK.

Objectives: To study non-tolerance to spectacle prescriptions in a busy community optometric practice, with several practitioners.

Methods: A spectacle non-tolerance was defined in a pragmatic way, as a patient who had collected spectacles from the practice and subsequently returned because they were either having problems with, or were unable to wear, their new spectacles. Patients over 16 years of age, who met the above definition of non-tolerance were sequentially recruited over a 6 month period. Patients experiencing adaptation problems were first seen by a dispensing optician and any dispensing issues resolved. If the spectacle dispensing was felt to be correct, or if the non-tolerance persisted, then the patient was re-examined by an optometrist and the results analysed.

Results: Non-tolerance examinations accounted for 62 of the 3091 eye examinations during the study period. The average rate of non-tolerance, averaged across the practitioners, was 1.8%, varying from 1.3-3.3% for individual practitioners. Gender was not a factor in non-tolerance, however age was, with presbyopes accounting for 88.1%. The most common reasons for non-tolerance were, in order of decreasing frequency: prescription related (61.0%), dispensing related (22.0%), pathology (8.5%), data entry error (6.8%) and binocular vision anomalies (1.7%). Of prescription related errors, gauging the spherical element accounted for the majority of inaccuracies, followed by problems with the near/intermediate addition. In every case, the final prescription was within 1.00 D of the not tolerated, prescription; 84.4% were within +/-0.50 D.

Conclusions: Spectacle prescription non-tolerance forms a small, but important, form of adverse reaction in optometric clinics. Most non-tolerances can be resolved by small changes, within 0.50 D, to the prescription.
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http://dx.doi.org/10.1111/j.1475-1313.2009.00682.xDOI Listing
January 2010