Publications by authors named "Karla Zadnik"

81 Publications

Uncorrected Refractive Error and Distance Visual Acuity in Children Aged 6 to 14 Years.

Optom Vis Sci 2021 Jan;98(1):3-12

College of Optometry, The Ohio State University, Columbus, Ohio.

Significance: This study presents the relationship between distance visual acuity and a range of uncorrected refractive errors, a complex association that is fundamental to clinical eye care and the identification of children needing refractive correction.

Purpose: This study aimed to analyze data from the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error Study to describe the relationship between distance uncorrected refractive error and visual acuity in children.

Methods: Subjects were 2212 children (51.2% female) 6 to 14 years of age (mean ± standard deviation, 10.2 ± 2.1 years) participating in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error Study between 2000 and 2010. Uncorrected distance visual acuity was measured using a high-contrast projected logMAR chart. Cycloplegic refractive error was measured using the Grand Seiko WR-5100K autorefractor. The ability of logMAR acuity to detect various categories of refractive error was examined using receiver operating characteristic curves.

Results: Isoacuity curves show that increasing myopic spherical refractive errors, increasing astigmatic refractive errors, or a combination of both reduces distance visual acuity. Visual acuity was reduced by approximately 0.5 minutes of MAR per 0.30 to 0.40 D of spherical refractive error and by approximately 0.5 minutes of MAR per 0.60 to 0.90 D of astigmatism. Higher uncorrected hyperopic refractive error had little effect on distance visual acuity. Receiver operating characteristic curve analysis suggests that a logMAR distance acuity of 0.20 to 0.32 provides the best balance between sensitivity and specificity for detecting refractive errors other than hyperopia. Distance acuity alone was ineffective for detecting hyperopic refractive errors.

Conclusions: Higher myopic and/or astigmatic refractive errors were associated with predictable reductions in uncorrected distance visual acuity. The reduction in acuity per diopter of cylindrical error was about half that for spherical myopic error. Although distance acuity may be a useful adjunct to the detection of myopic spherocylindrical refractive errors, accommodation presumably prevents acuity from assisting in the detection of hyperopia. Alternate procedures need to be used to detect hyperopia.
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http://dx.doi.org/10.1097/OPX.0000000000001630DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7789395PMC
January 2021

Myopia Prevention: Here Comes the Sun.

Authors:
Karla Zadnik

Ophthalmology 2020 11 5;127(11):1470-1471. Epub 2020 Aug 5.

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http://dx.doi.org/10.1016/j.ophtha.2020.05.016DOI Listing
November 2020

An Analysis of the Optometric Applicant Pool Relative to Matriculants.

Optom Vis Sci 2019 09;96(9):637-646

Southern College of Optometry, Memphis, Tennessee.

Significance: The interplay of applicants to optometry school and matriculants has not been explored systematically. It is vital that the profession examines these trends to ensure a viable pipeline of future doctors of optometry.

Purpose: The purpose of this study was to describe the demographics and academic qualifications of entering optometry classes from autumn 2010 through autumn 2018 of U.S.-based optometric institutions' application pool and matriculants (enrollees).

Methods: Data were gathered from reports generated from accredited schools and colleges of optometry in the United States and compiled by the Association of Schools and Colleges of Optometry (publicly available) and the Optometry Centralized Application Service. Metrics included the annual number of verified applicants, the annual number of matriculants, the home region of U.S.-based applicants, and the Optometry Admission Test (OAT) performance and grade point average of verified applicants.

Results: The number of verified applicants for autumn 2018 was 0.95% higher than that for autumn 2010, yet the number of matriculants in 2018 compared with 2010 increased by 11.2% with an applicant-to-matriculant ratio in 2010 of 1.53 compared with 1.39 in 2018. Grade point average and academic average OAT scores were stable from 2010 to 2018. The ratios of verified applicants with an academic average OAT score of at least 300 to matriculants were 0.87 for autumn 2018 and 0.92 for autumn 2010. The ratios of verified applicants with a grade point average of at least 3.00 to matriculants were 1.13 for autumn 2018 and 1.23 for autumn 2015.

Conclusions: Evidence supports the conclusion that the applicant pool has remained essentially flat for the last decade, whereas the number of matriculants has increased substantially; thus, the number of qualified applicants to matriculants has logically decreased. In the last 2 years, optometric programs have responded by decreasing their institution's number of matriculants to accommodate the national trends.
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http://dx.doi.org/10.1097/OPX.0000000000001424DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6727934PMC
September 2019

Intrastromal corneal ring segments for treating keratoconus.

Cochrane Database Syst Rev 2019 05 14;5:CD011150. Epub 2019 May 14.

College of Optometry, The Ohio State University, 338 West Tenth Avenue, Columbus, Ohio, USA, OH 43210.

Background: Keratoconus is a degenerative condition of the cornea that profoundly affects vision and vision-specific quality of life. The axial cornea thins and protrudes, resulting in irregularity and, eventually, scarring of the cornea. There are multiple options available for treating keratoconus. Intrastromal corneal ring segments are small, crescent-shaped plastic rings that are placed in the deep, peripheral corneal stroma in order to flatten the cornea. They are made of polymethylmethacrylate (PMMA). The procedure does not involve corneal tissue nor does it invade the central optical zone. Intrastromal corneal ring segments are approved for use when contact lenses or spectacles are no longer adequate.

Objectives: To evaluate the effectiveness and safety of intrastromal corneal ring segments as a treatment for keratoconus.

Search Methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2018, Issue 1); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature Database (LILACS); ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not implement any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 25 January 2018.

Selection Criteria: Two review authors independently assessed records from the electronic searches to identify randomized controlled trials (RCTs). Disagreements were resolved by discussion.

Data Collection And Analysis: We planned for two authors to independently review full-text reports, using standard methodological procedures expected by Cochrane.

Main Results: We found no RCTs comparing intrastromal corneal ring segments with spectacles or contact lenses.

Authors' Conclusions: In the absence of eligible RCTs to review, no conclusions can be drawn.
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http://dx.doi.org/10.1002/14651858.CD011150.pub2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6516208PMC
May 2019

Outdoor Activity Protects Against Childhood Myopia-Let the Sun Shine In.

JAMA Pediatr 2019 05;173(5):415-416

The Ohio State University College of Optometry, Columbus.

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http://dx.doi.org/10.1001/jamapediatrics.2019.0278DOI Listing
May 2019

The Response AC/A Ratio Before and After the Onset of Myopia.

Invest Ophthalmol Vis Sci 2017 03;58(3):1594-1602

The Ohio State University College of Optometry, Columbus, Ohio, United States.

Purpose: To investigate the ratio of accommodative convergence per diopter of accommodative response (AC/A ratio) before, during, and after myopia onset.

Methods: Subjects were 698 children aged 6 to 14 years who became myopic and 430 emmetropic children participating in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error. Refractive error was measured using cycloplegic autorefraction, near work by parent survey, and the AC/A ratio by simultaneously monitoring convergence and accommodative response. The response AC/A ratios of children who became myopic were compared with age-, sex-, and ethnicity-matched model estimates for emmetropic children from 5 years before through 5 years after the onset of myopia.

Results: The response AC/A ratio was not significantly different between the two groups 5 years before onset, then increased monotonically in children who became myopic until reaching a plateau at myopia onset of about 7 Δ/D compared to about 4 Δ/D for children who remained emmetropic (differences between groups significant at P < 0.01 from 4 years before onset through 5 years after onset). A higher AC/A ratio was associated with greater accommodative lag but not with the rate of myopia progression regardless of the level of near work.

Conclusions: An increasing AC/A ratio is an early sign of becoming myopic, is related to greater accommodative lag, but does not affect the rate of myopia progression. The association with accommodative lag suggests that the AC/A ratio increase is from greater neural effort needed per diopter of accommodation rather than change in the accommodative convergence crosslink gain relationship.
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http://dx.doi.org/10.1167/iovs.16-19093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5361580PMC
March 2017

The Effect of Age, Accommodation, and Refractive Error on the Adult Human Eye.

Optom Vis Sci 2016 Jan;93(1):3-11

*OD, PhD, FAAO †MCOptom, PhD, FAAO ‡PhD SUNY College of Optometry, New York, New York (KR); University of Houston College of Optometry, Houston, Texas (MAB); and The Ohio State University College of Optometry, Columbus, Ohio (LTS, KZ).

Purpose: To quantify changes in ocular dimensions associated with age, refractive error, and accommodative response, in vivo, in 30- to 50-year-old human subjects.

Methods: The right eyes of 91 adults were examined using ultrasonography, phakometry, keratometry, pachymetry, interferometry, anterior segment optical coherence tomography, and high-resolution magnetic resonance imaging. Accommodation was measured subjectively with a push-up test and objectively using open-field autorefraction. Regression analyses were used to assess differences in ocular parameters with age, refractive error, and accommodation.

Results: With age, crystalline lens thickness increased (0.03 mm/yr), anterior lens curvature steepened (0.11 mm/yr), anterior chamber depth decreased (0.02 mm/yr), and lens equivalent refractive index decreased (0.001/yr) (all p < 0.01). With increasing myopia, there were significant increases in axial length (0.37 mm/D), vitreous chamber depth (0.34 mm/D), vitreous chamber height (0.09 mm/D), and ciliary muscle ring diameter (0.10 mm/D) (all p < 0.05). Increasing myopia was also associated with steepening of both the cornea (0.16 mm/D) and anterior lens surface (0.011 mm/D) (both p < 0.04). With accommodation, the ciliary muscle ring diameter decreased (0.08 mm/D) and the muscle thinned posteriorly (0.008 mm/D), allowing the lens to shorten equatorially (0.07 mm/D) and thicken axially (0.06 mm/D) (all p < 0.03).

Conclusions: Refractive error is significantly correlated with not only the axial dimensions but also the anterior equatorial dimension of the adult eye. Further testing and development of accommodating intraocular lenses should account for differences in patients' preoperative refractive error.
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http://dx.doi.org/10.1097/OPX.0000000000000757DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4692191PMC
January 2016

Who Says There's Nothing New under the Sun?

Optom Vis Sci 2015 Nov;92(11):e392-3

*OD, PhD, FAAO The Ohio State University College of Optometry, Columbus, Ohio (both authors).

The time since our first publication in 2007 describing time spent outdoors as protective for juvenile myopia onset to clinical trials incorporating outdoor light interventions has been short. The time outdoors/myopia example highlights the incorporation of clinical or epidemiologic evidence to translational research that may eventually change clinical practice and/or behavior.
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http://dx.doi.org/10.1097/OPX.0000000000000753DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4621777PMC
November 2015

Prediction of Juvenile-Onset Myopia.

JAMA Ophthalmol 2015 Jun;133(6):683-9

College of Optometry, The Ohio State University, Columbus.

Importance: Myopia (nearsightedness) has its onset in childhood and affects about one-third of adults in the United States. Along with its high prevalence, myopia is expensive to correct and is associated with ocular diseases that include glaucoma and retinal detachment.

Objective: To determine the best set of predictors for myopia onset in school-aged children.

Design, Setting, And Participants: The Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study was an observational cohort study of ocular development and myopia onset conducted at 5 clinical sites from September 1, 1989, through May 22, 2010. Data were collected from 4512 ethnically diverse, nonmyopic school-aged children from grades 1 through 8 (baseline grades 1 through 6) (ages 6 through 13 years [baseline, 6 through 11 years]).

Main Outcomes And Measures: We evaluated 13 candidate risk factors for their ability to predict the onset of myopia. Myopia onset was defined as -0.75 diopters or more of myopia in each principal meridian in the right eye as measured by cycloplegic autorefraction at any visit after baseline until grade 8 (age 13 years). We evaluated risk factors using odds ratios from discrete time survival analysis, the area under the curve, and cross validation.

Results: A total of 414 children became myopic from grades 2 through 8 (ages 7 through 13 years). Of the 13 factors evaluated, 10 were associated with the risk for myopia onset (P < .05). Of these 10 factors, 8 retained their association in multivariate models: spherical equivalent refractive error at baseline, parental myopia, axial length, corneal power, crystalline lens power, ratio of accommodative convergence to accommodation (AC/A ratio), horizontal/vertical astigmatism magnitude, and visual activity. A less hyperopic/more myopic baseline refractive error was consistently associated with risk of myopia onset in multivariate models (odds ratios from 0.02 to 0.13, P < .001), while near work, time outdoors, and having myopic parents were not. Spherical equivalent refractive error was the single best predictive factor that performed as well as all 8 factors together, with an area under the curve (C statistic) ranging from 0.87 to 0.93 (95% CI, 0.79-0.99).

Conclusions And Relevance: Future myopia can be predicted in a nonmyopic child using a simple, single measure of refractive error. Future trials for prevention of myopia should target the child with low hyperopia as the child at risk.
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http://dx.doi.org/10.1001/jamaophthalmol.2015.0471DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4607030PMC
June 2015

Author response: what to do about racial disparities in access to glasses among children in the US?

Invest Ophthalmol Vis Sci 2015 Jan 6;56(1):106. Epub 2015 Jan 6.

State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Division of Preventative Ophthalmology, Guangzhou, China.

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http://dx.doi.org/10.1167/iovs.14-16055DOI Listing
January 2015

The contributions of near work and outdoor activity to the correlation between siblings in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study.

Invest Ophthalmol Vis Sci 2014 Sep 9;55(10):6333-9. Epub 2014 Sep 9.

The Ohio State University College of Optometry, Columbus, Ohio, United States.

Purpose: We determined the correlation between sibling refractive errors adjusted for shared and unique environmental factors using data from the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study.

Methods: Refractive error from subjects' last study visits was used to estimate the intraclass correlation coefficient (ICC) between siblings. The correlation models used environmental factors (diopter-hours and outdoor/sports activity) assessed annually from parents by survey to adjust for shared and unique environmental exposures when estimating the heritability of refractive error (2*ICC).

Results: Data from 700 families contributed to the between-sibling correlation for spherical equivalent refractive error. The mean age of the children at the last visit was 13.3 ± 0.90 years. Siblings engaged in similar amounts of near and outdoor activities (correlations ranged from 0.40-0.76). The ICC for spherical equivalent, controlling for age, sex, ethnicity, and site was 0.367 (95% confidence interval [CI] = 0.304, 0.420), with an estimated heritability of no more than 0.733. After controlling for these variables, and near and outdoor/sports activities, the resulting ICC was 0.364 (95% CI = 0.304, 0.420; estimated heritability no more than 0.728, 95% CI = 0.608, 0.850). The ICCs did not differ significantly between male-female and single sex pairs.

Conclusions: Adjusting for shared family and unique, child-specific environmental factors only reduced the estimate of refractive error correlation between siblings by 0.5%. Consistent with a lack of association between myopia progression and either near work or outdoor/sports activity, substantial common environmental exposures had little effect on this correlation. Genetic effects appear to have the major role in determining the similarity of refractive error between siblings.
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http://dx.doi.org/10.1167/iovs.14-14640DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4193758PMC
September 2014

Peripheral defocus and myopia progression in myopic children randomly assigned to wear single vision and progressive addition lenses.

Invest Ophthalmol Vis Sci 2013 Aug 27;54(8):5761-70. Epub 2013 Aug 27.

University of Houston College of Optometry, Houston, Texas 77204-2020, USA.

Purpose: To determine the effect of progressive addition lenses (PALs) and single vision lenses (SVLs) on peripheral defocus in myopic children, and to compare the effect of myopic versus hyperopic peripheral defocus on foveal myopia progression.

Methods: Eighty-four myopic children aged 6 to 11 years with spherical equivalent (SE) cycloplegic autorefraction between -0.75 diopters (D) and -4.50 D were randomly assigned to wear SVLs or PALs. Aberrometry measurements of the eye and spectacles were made centrally, 30° nasally, temporally, and superiorly, and 20° inferiorly on the retina using a Complete Ophthalmic Analysis System for Vision Research (COAS-VR). The association between peripheral defocus and the 1-year change in central myopia was investigated.

Results: SVLs caused a hyperopic shift in peripheral defocus at all locations (all P ≤ 0.0003). PALs caused a myopic shift in peripheral defocus in three of four locations measured (all P ≤ 0.01) with the greatest shift superiorly due to the PAL addition (-1.04 ± 0.30 D). Superior retinal defocus when wearing either SVLs or PALs was associated with the 1-year change in central myopia. The adjusted 1-year change in central SE myopia was -0.38 D for children with absolute superior myopic defocus (n = 67) and -0.65 D for children with absolute superior hyperopic defocus (n = 17; difference = 0.27 D; P = 0.002).

Conclusions: PALs caused a myopic shift in peripheral defocus. Superior myopic defocus was associated with less central myopia progression. These data support the continued investigation of optical designs that result in peripheral myopic defocus as a potential way to slow myopia progression. (ClinicalTrials.gov number, NCT00335049.).
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http://dx.doi.org/10.1167/iovs.13-11904DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3755539PMC
August 2013

Quantification of age-related and per diopter accommodative changes of the lens and ciliary muscle in the emmetropic human eye.

Invest Ophthalmol Vis Sci 2013 Feb 7;54(2):1095-105. Epub 2013 Feb 7.

College of Optometry, State University of New York, New York, NY, USA.

Purpose: To calculate age-related and per diopter (D) accommodative changes in crystalline lens and ciliary muscle dimensions in vivo in a single cohort of emmetropic human adults ages 30 to 50 years.

Methods: The right eyes of 26 emmetropic adults were examined using ultrasonography, phakometry, anterior segment optical coherence tomography, and high resolution magnetic resonance imaging. Accommodation was measured both subjectively and objectively.

Results: In agreement with previous research, older age was linearly correlated with a thicker lens, steeper anterior lens curvature, shallower anterior chamber, and lower lens equivalent refractive index (all P < 0.01). Age was not related to ciliary muscle ring diameter (CMRD) or lens equatorial diameter (LED). With accommodation, lens thickness increased (+0.064 mm/D, P < 0.001), LED decreased (-0.075 mm/D, P < 0.001), CMRD decreased (-0.105 mm/D, P < 0.001), and the ciliary muscle thickened anteriorly (+0.013 to +0.026 mm/D, P < 0.001) and thinned posteriorly (-0.011 to -0.015, P < 0.01). The changes per diopter of accommodation in LED, CMRD, and ciliary muscle thickness were not related to subject age.

Conclusions: The per diopter ciliary muscle contraction is age independent, even as total accommodative amplitude declines. Quantifying normal biometric dimensions of the accommodative structures and changes with age and accommodative effort will further the development of new IOLs designed to harness ciliary muscle forces.
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http://dx.doi.org/10.1167/iovs.12-10619DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3567753PMC
February 2013

Time outdoors, visual activity, and myopia progression in juvenile-onset myopes.

Invest Ophthalmol Vis Sci 2012 Oct 1;53(11):7169-75. Epub 2012 Oct 1.

The Ohio State University College of Optometry, Columbus, Ohio 43210, USA.

Purpose: To investigate the association between myopia progression and time spent outdoors and in various visual activities.

Methods: Subjects were 835 myopes (both principal meridians -0.75 diopters [D] or more myopia by cycloplegic autorefraction) in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study with both progression data and at least one measure of activity associated with a progression interval. Activity data were collected by parental survey. Average activity level (mean of the activity at the beginning and the end of a 1-year progression interval) was the primary predictor in a repeated-measures mixed model. The model controlled for age, sex, ethnicity, refractive error at the beginning of the progression interval, clinic site, and type of autorefractor used. Effects were scaled based on performing an additional 10 hours per week of an activity.

Results: In the multivariate model, the number of hours of reading for pleasure per week was not significantly associated with annual myopia progression at an a priori level of P ≤ 0.01, nor were the other near activities, the near-work composite variable diopter-hours, or outdoor/sports activity. The magnitude of effects was clinically small. For example, the largest multivariate effect was that each additional 10 hours of reading for pleasure per week at the end of a progression interval was associated with an increase in average annual progression by -0.08 D.

Conclusions: Despite protective associations previously reported for time outdoors reducing the risk of myopia onset, outdoor/sports activity was not associated with less myopia progression following onset. Near work also had little meaningful effect on the rate of myopia progression.
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http://dx.doi.org/10.1167/iovs.11-8336DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3474591PMC
October 2012

The effect of phenylephrine on the ciliary muscle and accommodation.

Optom Vis Sci 2012 Oct;89(10):1507-11

College of Optometry, The State University of New York, New York, New York 10036, USA.

Purpose: To objectively measure changes in the human ciliary muscle dimensions in vivo after instillation of topical phenylephrine, a mydriatic and vasodilating agent.

Methods: A cross-sectional study of 25 healthy young adults was conducted. Measurements of pupil size, accommodation, and ciliary muscle thickness were made both before and 30 min after instillation of 1% proparacaine and 2.5% phenylephrine. Accommodation was measured in three ways: subjectively using a push-up technique and Royal Air Force (RAF) rule, and objectively using both the Grand Seiko autorefractor and PowerRefractor. Images of the temporal ciliary muscle were acquired using the Visante Anterior Segment Optical Coherence Tomographer (OCT). Ciliary muscle images were objectively analyzed using a computer-based segmentation technique.

Results: Amplitude of accommodation using the push-up test was reduced by about 1 D with phenylephrine (p < 0.001). Phenylephrine did not change the accommodative response to a 4 D Badal target as measured by either autorefraction or photorefraction (p > 0.30). There was statistically significant thickening of the anterior region and thinning of the posterior region of the ciliary muscle with accommodation (p < 0.001, all locations). Phenylephrine did not affect either baseline ciliary muscle thickness or the accommodative contraction of the muscle (p > 0.09).

Conclusions: Low-dose phenylephrine does not affect ciliary muscle dimensions, ciliary muscle contractility, or accommodative response to a 4 D near target.
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http://dx.doi.org/10.1097/OPX.0b013e318269c8d0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3607430PMC
October 2012

Asymmetry in keratoconus and vision-related quality of life.

Cornea 2013 Mar;32(3):267-72

College of Optometry, The Ohio State University, Columbus, OH 43210, USA.

Purpose: To examine the relationship of increased ocular asymmetry over time to vision-related quality of life in keratoconus.

Methods: The subjects were from the Collaborative Longitudinal Evaluation of Keratoconus Study and had complete data on a least 1 scale of the National Eye Institute Visual Function Questionnaire and examination data at baseline and at least 1 follow-up visit. Three measures of disease asymmetry [visual acuity (VA), corneal curvature, and refractive error] and better eye status were assessed. Multilevel models were fit to the data.

Results: The analyses were completed using the data from 961 subjects. Six scales on the National Eye Institute Visual Function Questionnaire had adequate variability to the model (distance activity, driving, mental health, near activity, ocular pain, and role difficulties). Refractive error changes were not associated with statistically significant quality-of-life differences. Except for ocular pain, statistically significant, but not clinically meaningful, differences were found for VA changes and corneal curvature changes. For a 0.1-unit logarithm of the minimum angle of resolution of VA change, the quality-of-life scales decreased between 0.20 and 0.99 units. For a 1.00-diopter steepening of corneal curvature, these decreases were on the order of 0.20 to 0.59 units. Changes related to asymmetry were small as well; decreases were on the order of 0.20 to 0.38 units.

Conclusions: Increasing ocular asymmetry and decreases in VA and corneal steepening in the better eye were associated with decreasing vision-related quality of life, although the magnitudes of the changes were not clinically meaningful. Of these 2 disease status indicators, the vision in the better eye had greater effect on the vision-related quality of life.
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http://dx.doi.org/10.1097/ICO.0b013e31825697c4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3482277PMC
March 2013

New cases of myopia in children.

Arch Ophthalmol 2012 Oct;130(10):1274-9

School of Optometry, University of Alabama at Birmingham, USA.

Objective: To report the percentage of new cases of myopia in 4927 children aged 5 to 16 years who participated in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error Study between 1989 and 2009.

Design: A multicenter, longitudinal, observational, volunteer study of refractive error and ocular development in children from 5 racial/ethnic groups in which the participants were children who were not myopic (right eye cycloplegic auto refraction of less myopia/more hyperopia than -0.75 diopters [D] in both principal meridians) at study entry. A new case was a diagnosis of myopia (right eye cycloplegic auto refraction of -0.75 D or more myopia in both principal meridians) after study entry.

Results: Of the 4556 children entering the study who were not myopic, 749 (16.4%) received a diagnosis of myopia after study entry. Among these 749 children, the ages of the participants at diagnosis varied from 7 to 16 years, with the largest number diagnosed at age 11 years(136 participants [18.2%]). New cases of myopia occurred in 27.3% of Asians, 21.4% of Hispanics, 14.5% of Native Americans, 13.9% of African Americans, and 11% of whites. Female participants had more new cases than did male participants (18.5% vs 14.5%). Normal-birth weight children had more new cases than did low-birth weight children (16.9% vs 15.5%).

Conclusions: Sixteen percent of children enrolled in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error Study developed myopia during their school-aged years. The percentage increased yearly until age 11 years, after which it decreased. New cases of myopia varied by ethnic/racial group.
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http://dx.doi.org/10.1001/archophthalmol.2012.1449DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4457538PMC
October 2012

Academy president reports: "indebtedness".

Authors:
Karla Zadnik

Optom Vis Sci 2012 Jun;89(6):826

American Academy of Optometry, Columbus, Ohio, USA.

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http://dx.doi.org/10.1097/OPX.0b013e31825c0679DOI Listing
June 2012

Corneal and crystalline lens dimensions before and after myopia onset.

Optom Vis Sci 2012 Mar;89(3):251-62

The Ohio State University College of Optometry, Columbus, Ohio 43210-1240, USA.

Purpose: To describe corneal and crystalline lens dimensions before, during, and after myopia onset compared with age-matched emmetropic values.

Methods: Subjects were 732 children aged 6 to 14 years who became myopic and 596 emmetropic children participating between 1989 and 2007 in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error Study. Refractive error was measured using cycloplegic autorefraction, corneal power using a hand-held autokeratometer, crystalline lens parameters using video-based phakometry, and vitreous chamber depth (VCD) using A-scan ultrasonography. Corneal and crystalline lens parameters in children who became myopic were compared with age-, gender-, and ethnicity-matched model estimates of emmetrope values annually from 5 years before through 5 years after the onset of myopia. The comparison was made without and then with statistical adjustment of emmetrope component values to compensate for the effects of longer VCDs in children who became myopic.

Results: Before myopia onset, the crystalline lens thinned, flattened, and lost power at similar rates for emmetropes and children who became myopic. The crystalline lens stopped thinning, flattening, and losing power within ±1 year of onset in children who became myopic compared with emmetropes statistically adjusted to match the longer VCDs of children who became myopic. In contrast, the cornea was only slightly steeper in children who became myopic compared with emmetropes (<0.25 D) and underwent little change across visits.

Conclusions: Myopia onset is characterized by an abrupt loss of compensatory changes in the crystalline lens that continue in emmetropes throughout childhood axial elongation. The mechanism responsible for this decoupling remains speculative but might include restricted equatorial growth from internal mechanical factors.
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http://dx.doi.org/10.1097/OPX.0b013e3182418213DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3288626PMC
March 2012

A randomized trial using progressive addition lenses to evaluate theories of myopia progression in children with a high lag of accommodation.

Invest Ophthalmol Vis Sci 2012 Feb 13;53(2):640-9. Epub 2012 Feb 13.

University of Houston, College of Optometry, Houston, Texas 77204-2020, USA.

Purpose: To compare the effect of wearing, then ceasing to wear, progressive addition lenses (PALs) versus single vision lenses (SVLs) on myopia progression in children with high accommodative lag to evaluate accommodative lag and mechanical tension as theories of myopia progression.

Methods: Eighty-five children (age range, 6-11 years) with spherical equivalent (SE) cycloplegic autorefraction between -0.75 D and -4.50 D were randomly assigned to wear SVLs or PALs for 1 year; all children wore SVLs a second year. Children had high accommodative lag and also had near esophoria if their myopia was greater than -2.25 D SE. The primary outcome after each year was the previous year's change in SE.

Results: When the children were randomly assigned to SVLs or PALs, the adjusted 1-year changes in SE were -0.52 D (SVL group) and -0.35 D (PAL group; treatment effect = 0.18 D; P = 0.01). When all children wore SVLs the second year, there was no difference in myopia progression between SVL and former PAL wearers (0.06 D; P = 0.50). Accommodative lag was not associated with myopia progression.

Conclusions: The statistically significant, but clinically small, PAL effect suggests that treatments aimed at reducing foveal defocus may not be as effective as previously thought in myopic children with high accommodative lag. Finding no evidence of treatment loss after discontinuing PAL wear supports hyperopic defocus-based theories such as accommodative lag; however, not finding an association between accommodative lag and myopia progression is inconsistent with the PAL effect being due to decreased foveal blur during near work. (Clinical Trials.gov number, NCT00335049.).
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http://dx.doi.org/10.1167/iovs.11-7769DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3317412PMC
February 2012

Intraocular pressure, ethnicity, and refractive error.

Optom Vis Sci 2011 Dec;88(12):1445-53

University of Houston College of Optometry, Houston, Texas 77204-2020, USA.

Purpose: The ethnically diverse Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study cohort provides a unique opportunity to explore associations among intraocular pressure (IOP), ethnicity, and refractive error while adjusting for potential confounding variables.

Methods: Mixed linear models were used to examine the effect of age, refractive error (cycloplegic auto-refraction), ethnicity, sex, and measurement protocol on IOP (Tono-pen) in 3777 children, aged 6 to 14 years at their first CLEERE visit (1995-2009). Children who became myopic during follow-up were used to examine the relationship between time since myopia onset and IOP. Clinically meaningful differences in IOP were preset at >2 mm Hg.

Results: IOP differed among refractive error categories with higher IOP in children with low/moderate myopia than those with high hyperopia (differences <1 mm Hg). There was a statistically significant relationship between age and IOP that depended on ethnicity (interaction p < 0.0001) and measurement protocol (interaction p < 0.0001). The relationship between sex and IOP depended on measurement protocol (interaction p = 0.0004). For children who became myopic during follow-up, the adjusted mean IOP showed a significant decline for only Asian (p = 0.024) and white children (p = 0.004). As with other statistically significant results, these changes in mean adjusted IOPs from 2 years before to 2 years after myopia onset were <2 mm Hg.

Conclusions: Small but significant differences in IOP by refractive error category were found in this ethnically diverse cohort of children. Relationships between IOP and age, ethnicity, sex, and measurement protocol were complicated by significant interactions between these parameters. Longitudinal analysis of children before and after myopia onset showed changes in IOP over time that varied by ethnicity. Higher IOPs before and at myopia onset were not present in all ethnic groups, with differences before and after onset too small to suggest a role for IOP in the onset of myopia.
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http://dx.doi.org/10.1097/OPX.0b013e318230f559DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3223547PMC
December 2011

Vitamin D receptor (VDR) and group-specific component (GC, vitamin D-binding protein) polymorphisms in myopia.

Invest Ophthalmol Vis Sci 2011 Jun 1;52(6):3818-24. Epub 2011 Jun 1.

College of Optometry, The Ohio State University, Columbus, Ohio 43210-1280, USA.

Purpose: Epidemiologic evidence indicates that time outdoors reduces the risk of myopia, suggesting a possible role for vitamin D. This case-control study was conducted to determine whether single-nucleotide polymorphisms (SNPs) within VDR at 12q13.11 and GC at 4q12-13 are associated with myopia.

Methods: The primary analysis was conducted on 81 white adult control subjects between 18 and 50 years of age with a spherical equivalent refractive error between +0.50 and +2.00 D in both eyes and less than 1.50 D of astigmatism. Affected myopic subjects were 289 unrelated white adults at least 18 years of age with at least -0.75 D myopia in both principal meridians of both eyes.

Results: One SNP within VDR was significantly associated with myopia in the multivariate analysis of the primary sample (rs2853559: odds ratio = 1.99, P = 0.003). In a subsample of less severely myopic white subjects between -0.75 and -4.00 D, three SNPs within VDR were significantly associated in a multivariate model after adjustment for multiple comparisons (rs2239182: odds ratio = 2.17, P = 0.007; rs3819545: odds ratio = 2.34, P = 0.003; rs2853559: odds ratio = 2.14, P = 0.0035), accounting for 12% of model variance over age alone.

Conclusions: Polymorphisms within VDR appear to be associated with low to moderate amounts of myopia in white subjects. Future studies should determine whether this finding can be replicated and should explore the biological significance of these variations with respect to myopia.
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http://dx.doi.org/10.1167/iovs.10-6534DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3109057PMC
June 2011

Accommodative lag and juvenile-onset myopia progression in children wearing refractive correction.

Vision Res 2011 May 20;51(9):1039-46. Epub 2011 Feb 20.

University of Houston College of Optometry, Houston, TX, United States.

The relationship between accommodative lag and annual myopia progression was investigated using linear models in 592 myopic children wearing a full refractive correction in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study. The mean (± SD) age and spherical equivalent refractive error at baseline were 10.4 ± 1.8 years and -2.13 ± 1.24 D, respectively. The mean annual progression of myopia was -0.45 ± 0.32 D, and the mean accommodative lag (for a 4-D Badal stimulus) was 1.59 ± 0.63 D. Neither lag at the beginning nor at the end of a yearly progression interval was associated with annual myopia progression (all p ≥ 0.12). These data suggest that foveal hyperopic retinal blur during near viewing may not drive juvenile-onset myopia progression.
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http://dx.doi.org/10.1016/j.visres.2011.02.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3111954PMC
May 2011

Bringing science (back?).

Authors:
Karla Zadnik

Optom Vis Sci 2010 Dec;87(12):929

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http://dx.doi.org/10.1097/OPX.0b013e3182035a76DOI Listing
December 2010

Study of Theories about Myopia Progression (STAMP) design and baseline data.

Optom Vis Sci 2010 Nov;87(11):823-32

College of Optometry, The Ohio State University, Columbus, Ohio, USA.

Purpose: The Study of Theories about Myopia Progression (STAMP) is a 2-year, double-masked, randomized clinical trial of myopic children 6 to 11 years of age. STAMP will evaluate the 1-year effect of progressive addition lenses (PALs) compared with single vision lenses (SVLs) on central refraction, peripheral refraction in four quadrants, and accommodative response and convergence. STAMP will also evaluate any changes 1 year after discontinuing PALs. Baseline characteristics of enrolled children are reported.

Methods: Eligible children had a high accommodative lag and either low myopia (less myopic than -2.25 diopter (D) spherical equivalent) or high myopia (more myopic than -2.25 D spherical equivalent) and esophoria at near. Children were randomly assigned to wear either PALs or SVLs for 1 year to determine the difference in myopia progression in the PAL group relative to the SVL group. All children will then wear SVLs for the 2nd year to evaluate the permanence of any treatment effect. Complete ocular biometric data are collected at 6-month intervals.

Results: Over 17 months, 192 children were screened, and 85 (44%) were eligible and enrolled. Of these 85 children, 44 (52%) were girls, and 54 (64%) were esophoric at near. The mean age (± SD) was 9.8 ± 1.3 years. The right eye mean cycloplegic spherical equivalent refractive error was -1.95 ± 0.78 D. Horizontal relative peripheral hyperopia (30° nasal retina + 0.56 ± 0.59 D; 30° temporal retina + 0.61 ± 0.77 D) and vertical relative peripheral myopia (30° superior retina -0.36 ± 0.92 D; 20° inferior retina -0.48 ± 0.83 D) were found.

Conclusions: The baseline data for STAMP are reported. Asymmetry between vertical and horizontal meridian relative peripheral refraction was found. STAMP will use the ocular biometric changes associated with the PAL treatment effect to attempt to elucidate the mechanism responsible for the treatment effect.
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http://dx.doi.org/10.1097/OPX.0b013e3181f6f776DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3075061PMC
November 2010

Visual activity before and after the onset of juvenile myopia.

Invest Ophthalmol Vis Sci 2011 Mar 29;52(3):1841-50. Epub 2011 Mar 29.

The Ohio State University College of Optometry, Columbus, Ohio 43210, USA.

Purpose: To investigate visual activities before and after the onset of juvenile myopia.

Methods: The subjects were 731 incident myopes (-0.75 D or more myopia on cycloplegic autorefraction in both meridians) and 587 emmetropes (between -0.25 and +1.00 D) in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study. Parents supplied visual activity data annually. Data from myopic children 5 years before through 5 years after myopia onset were compared to data from age-, sex-, and ethnicity-matched models of children who remained emmetropic.

Results: Hours per week spent reading or using a computer/playing video games did not differ between the groups before myopia onset; however, hours per week for both activities were significantly greater in myopes than in emmetropes at onset and in 4 of the 5 years after onset by 0.7 to 1.6 hours per week. Hours per week spent in outdoor/sports activities were significantly fewer for children who became myopic 3 years before onset through 4 years after onset by 1.1 to 1.8 hours per week. Studying and TV watching were not significantly different before myopia onset.

Conclusions: Before myopia onset, near work activities of future myopic children did not differ from those of emmetropes. Those who became myopic had fewer outdoor/sports activity hours than the emmetropes before, at, and after myopia onset. Myopia onset may influence children's near work behavior, but the lack of difference before onset argues against a major causative role for near work. Less outdoor/sports activity before myopia onset may exert a stronger influence on development than near work.
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http://dx.doi.org/10.1167/iovs.09-4997DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3101696PMC
March 2011

Relative peripheral refractive error and the risk of onset and progression of myopia in children.

Invest Ophthalmol Vis Sci 2011 Jan 5;52(1):199-205. Epub 2011 Jan 5.

The Ohio State University College of Optometry, Columbus, OH, USA.

Purpose: To investigate whether relative peripheral hyperopia is a risk factor for either the onset of myopia in children or the rate of myopic progression.

Methods: The risk of myopia onset was assessed in 2043 nonmyopic third-grade children (mean age ± SD = 8.8 ± 0.52 years) participating in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study between 1995 and 2007, 324 of whom became myopic by the eighth grade. Progression analyses used data from 774 myopic children in grades 1 to 8. Foveal and relative peripheral refractive error 30° in the nasal visual field was measured annually by using cycloplegic autorefraction. Axial length was measured by A-scan ultrasonography.

Results: The association between more hyperopic relative peripheral refractive error in the third grade and the risk of the onset of myopia by the eighth grade varied by ethnic group (Asian children odds ratio [OR] = 1.56, 95% confidence interval [CI] = 1.06-2.30; African-American children OR = 0.75, 95% CI = 0.58-0.96; Hispanics, Native Americans, and whites showed no significant association). Myopia progression was greater per diopter of more hyperopic relative peripheral refractive error, but only by a small amount (-0.024 D per year; P = 0.02). Axial elongation was unrelated to the average relative peripheral refractive error (P = 0.77), regardless of ethnicity.

Conclusions: Relative peripheral hyperopia appears to exert little consistent influence on the risk of the onset of myopic refractive error, on the rate of myopia progression, or on axial elongation.
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http://dx.doi.org/10.1167/iovs.09-4826DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3053275PMC
January 2011

The effect of bifocal add on accommodative lag in myopic children with high accommodative lag.

Invest Ophthalmol Vis Sci 2010 Dec 4;51(12):6104-10. Epub 2010 Aug 4.

Ohio State University College of Optometry, Columbus, Ohio, USA.

Purpose: To determine the effect of a bifocal add and manifest correction on accommodative lag in myopic children with high accommodative lag, who have been reported to have the greatest reduction in myopia progression with progressive addition lenses (PALs).

Methods: Monocular accommodative lag to a 4-D Badal stimulus was measured on two occasions 6 months apart in 83 children (mean ± SD age, 9.9 ± 1.3 years) with high lag randomized to wearing single-vision lenses (SVLs) or PALs. Accommodative lag was measured with the following corrections: habitual, manifest, manifest with +2.00-D add, and habitual with +2.00-D add (6-month visit only).

Results: At baseline, accommodative lag was higher (1.72 ± 0.37 D; mean ± SD) when measured with manifest correction than with habitual correction (1.51 ± 0.50; P < 0.05). This higher lag with manifest correction correlated with a larger amount of habitual undercorrection at baseline (r = -0.29, P = 0.009). A +2.00-D add over the manifest correction reduced lag by 0.45 ± 0.34 D at baseline and 0.33 ± 0.38 D at the 6-month visit. Lag results at 6 months were not different between PAL and SVL wearers (P = 0.92).

Conclusions: A +2.00-D bifocal add did not eliminate accommodative lag and reduced lag by less than 25% of the bifocal power, indicating that children mainly responded to a bifocal by decreasing accommodation. If myopic progression is substantial, measuring lag with full correction can overestimate the hyperopic retinal blur that a child most recently experienced. (ClinicalTrials.gov number, NCT00335049.).
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http://dx.doi.org/10.1167/iovs.09-4417DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3055747PMC
December 2010

Gas permeable and soft contact lens wear in children.

Optom Vis Sci 2010 Jun;87(6):414-20

The Ohio State University College of Optometry, Columbus, Ohio 43210, USA.

Purpose: To compare children's reports of comfort, vision, and contact lens-related issues in gas permeable (GP) and soft (SCL) contact lens wearers.

Methods: Subjects were 116 8- to 11-year old children in the Contact Lenses and Myopia Progression Study. Aspects of contact lens wear were compared for children remaining in their original treatment group (either GPs or SCLs) for 3 years. Questionnaires were completed at every visit, as was visual acuity. Comparisons were made between the two groups using logistic regression or mixed linear models analyses as appropriate to examine the contact lens wearing experience. Additionally, children crossing over from GP wear to SCLs were compared with children remaining in GP lenses to determine the potential factors related to GP dissatisfaction.

Results: Seventy percent of GP wearers and 93% of SCL wearers wore their assigned lenses every visit. GP wearers wore their lenses significantly fewer hours per week than the SCL wearers (76.2 h/week vs. 86.8 h/week, respectively, p = 0.003). GP wearers had statistically significantly better visual acuity though the difference was not clinically meaningful (p < 0.001). Comfort was poorer among the GP wearers using the Ocular Pain subscale (p < 0.001) but did not differ using a subjective question about comfort. Symptoms were more frequent in GP wearers than SCL wearers (p = 0.002) and were related to reports of discomfort. Significant factors relating to crossing over from GPs to SCLs were lower wearing time with GPs and itching.

Conclusions: Children are able to successfully wear GP and soft contact lenses. Long-term adaptation occurred more frequently to SCLs than to GPs. The amount of time GP lens wearers are able to comfortably wear their contact lenses and the amount of itching may help determine whether they will remain in that modality.
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http://dx.doi.org/10.1097/OPX.0b013e3181dc9a04DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4448960PMC
June 2010

The influence of gender and hormone status on the severity and progression of keratoconus.

Cornea 2010 Jan;29(1):65-72

College of Optometry, The Ohio State University, Columbus, OH 43210-1240, USA.

Purpose: To assess the effects of gender and hormone status on the severity and progression of keratoconus in patients enrolled in the Collaborative Longitudinal Evaluation of Keratoconus Study.

Methods: The severity and progression of keratoconus in both men (M) and women were evaluated over a 4-year period that encompassed menopausal transition for hormone-active women (HA) and hormone-inactive women (HI). Four outcome measures were selected as indicators of the severity of keratoconus: high-contrast best-corrected visual acuity, low-contrast best-corrected visual acuity, the steep keratometric measurement, and corneal scarring (yes/no).

Results: There were no statistically significant differences among the 3 groups (M, HA, and HI) in race, history of atopic disease, family history of keratoconus, or rigid contact lens wear in the right and left eyes. At baseline, there were no significant differences among the 3 groups in high-contrast best-corrected visual acuity, low-contrast best-corrected visual acuity, or steep keratometric reading. Progression of keratoconus, as assessed by changes in these 3 continuous variables, was equal for the 3 groups. M had more corneal scarring than did HA or HI; however, there was no progression of scarring for any of the groups.

Conclusion: Keratoconus progressed in both men and women, aged 48-59 years; however, there were no differences among the groups in progression.
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http://dx.doi.org/10.1097/ICO.0b013e3181ac0518DOI Listing
January 2010