Publications by authors named "John S M Chang"

20 Publications

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July consultation #5.

Authors:
John S M Chang

J Cataract Refract Surg 2020 07;46(7):1060-1061

Hong Kong, China.

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http://dx.doi.org/10.1097/01.j.jcrs.0000694668.70358.fdDOI Listing
July 2020

Five-Year Changes in Corneal Astigmatism After Combined Femtosecond-Assisted Phacoemulsification and Arcuate Keratotomy.

Am J Ophthalmol 2020 09 11;217:232-239. Epub 2020 May 11.

Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong; Hong Kong Laser Eye Centre, Hong Kong. Electronic address:

Purpose: To investigate the long-term stability of corneal astigmatism after combined femtosecond (fs)-assisted phacoemulsification and arcuate keratotomy.

Design: Retrospective, interventional case series.

Methods: Surgery was performed using a Victus (Bausch & Lomb) platform. A single, 450-μm-deep arcuate keratotomy was paired at the 8-mm zone with the main phacoemulsification incision in the opposite meridian. The keratotomy incisions were not opened. Corneal astigmatism measurements obtained preoperatively and at 2 and 5 years postoperatively were analyzed using vector analysis.

Results: A total of 44 eyes of 44 patients (mean age 66.0 ± 10.1 years) were included. The mean preoperative corneal astigmatism was 1.40 ± 0.66 diopters (D). This was reduced to 0.74 ± 0.54 D at 2 years and 0.70 ± 0.50 at 5 years postoperatively (P < .001). There were no statistically significant differences between postoperative corneal astigmatism at 2 years and at 5 years (P = .609). Both magnitude of error and absolute angle of error were comparable between the 2 postoperative time points (P > .805). At the end of 5 years, 65% of the eyes were within 15 degrees of the preoperative astigmatic meridian. Comparative analysis showed significantly higher surgically induced astigmatism, lower differences in vector and absolute angles of error for the eyes with preoperative with-the-rule (WTR) astigmatism than eyes with against-the-rule (ATR) astigmatism at 5 years (P < .004).

Conclusions: Our study showed the stability of femtosecond (fs)-assisted arcuate keratotomy was well-maintained over 5 years. There was a tendency of increasing overcorrection of preoperative WTR astigmatism and undercorrection of ATR astigmatism over time.
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http://dx.doi.org/10.1016/j.ajo.2020.05.004DOI Listing
September 2020

Transient corneal ectasia after phacoemulsification in an eye with femtosecond intrastromal presbyopic treatment.

J Cataract Refract Surg 2020 01;46(1):143-146

From the Department of Ophthalmology, Hong Kong Sanatorium & Hospital (T.C.Y. Chan, Chang); Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong (T.C.Y. Chan, J.C.K. Chan, Lam, Chang); and Hong Kong Eye Hospital (C.K. Chan, Lam), Hong Kong, China.

We report a case of transient corneal ectasia developed after phacoemulsification in an eye previously treated with INTRACOR. There was a myopic refractive surprise after cataract surgery. Corneal tomography showed an increase in keratometry and elevation profile compared with preoperative examination. Soft contact lenses and intraocular pressure-lowering medications were prescribed as interim treatment. Clinical improvement was seen gradually, and the resolution of myopia and ectasia was achieved at 3 months. We believe that high intraocular pressure during phacoemulsification and the weakening effect of femtosecond intrastromal presbyopic treatment can be the culprits.
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http://dx.doi.org/10.1016/j.jcrs.2019.08.050DOI Listing
January 2020

Monovision with a Bifocal Diffractive Multifocal Intraocular Lens in Presbyopic Patients: A Prospective, Observational Case Series.

Am J Ophthalmol 2020 04 23;212:105-115. Epub 2019 Nov 23.

Department of Ophthalmology, Hong Kong Sanatorium & Hospital, Hong Kong.

Purpose: We report the visual outcomes and patient satisfaction after bilateral implantation of a bifocal diffractive intraocular lens with monovision.

Design: Prospective, observational case series.

Methods: Twenty-one subjects underwent cataract surgery or refractive lens exchange with bilateral implantation of the ZMB00 intraocular lens, with the dominant eye and nondominant eye targeted for plano and -1.25 to -1.00 diopters, respectively. Postoperative assessments included visual acuity (VA) at various distances under photopic and mesopic conditions; defocus curve, contrast sensitivity, and stereopsis; and Visual Function Questionnaire-25 and supplementary questionnaire.

Results: Mean binocular uncorrected VA at distance, intermediate (67 cm), and near (30 cm) were -0.03 ± 0.06, 0.12 ± 0.18, and 0.11 ± 0.05, respectively. No eyes lost >1 line of corrected distance VA. Binocular intermediate VA was significantly better in the uncorrected condition (P = .004) whereas binocular distance VA was better in the distance-corrected condition (P = .014). Near VA was similar in both conditions (P > .05). Stereoacuity and contrast sensitivity were within normal limits. All subjects had a composite score of ≥90 for vision-targeted items in the National Eye Institute Visual Function Questionnaire-25. Halos, glare, and starbursts occurred in 52%, 29%, and 24% of subjects, respectively. All subjects reported a satisfaction score of ≥3.5 of 5 and required no spectacles postoperatively. No intraocular lens exchange was required.

Conclusions: Monovision with bilateral bifocal multifocal intraocular lens was safe and provided satisfactory vision at various distances, with good stereopsis and contrast sensitivity. Complete spectacle independence and high satisfaction score were achieved. In comparison with bilateral emmetropic bifocal multifocal intraocular lens, it provided better vision at intermediate and at very near distances without inducing more dysphotopsia.
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http://dx.doi.org/10.1016/j.ajo.2019.11.010DOI Listing
April 2020

Bilateral Implantation of a Single-Piece Bifocal Diffractive Intraocular Lens in Presbyopic Patients: A Prospective Case Series.

Authors:
John S M Chang

Asia Pac J Ophthalmol (Phila) 2019 Jan-Feb;8(1):12-21. Epub 2018 Sep 27.

Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Hong Kong.

Purpose: To report visual outcomes and quality after bilateral implantation of a single-piece diffractive multifocal intraocular lens (MIOL) with a bifocal design.

Design: Prospective, observational case series.

Methods: All presbyopic subjects were implanted with the ZMB00 MIOL (Abbott Medical Optics) at the Hong Kong Sanatorium and Hospital. We evaluated the distance, intermediate, and near visual acuity (VA) under photopic and mesopic conditions; contrast sensitivity with and without glare under photopic and mesopic conditions; quality of vision; and rate of spectacle independence.

Results: A total of 36 subjects were included. No intraoperative complications developed. At the 6-month visit, the mean (± standard deviation) monocular uncorrected VAs at distance, intermediate, and near were 0.01 ± 0.12, 0.26 ± 0.17, and 0.09 ± 0.08, respectively. The respective mean binocular uncorrected VAs were -0.05 ± 0.09, 0.12 ± 0.13, and 0.04 ± 0.06. No eyes lost any corrected distance VA. The binocular contrast sensitivity was significantly better without glare than with glare under photopic and mesopic conditions ( < 0.05 for all spatial frequencies under both conditions). A total of 21 (58%) and 21 subjects (58%) reported halo and glare, respectively. Thirty subjects (83%) reported complete spectacle independence.

Conclusions: Bilateral implantation of the bifocal MIOL in presbyopic patients with or without cataract was safe and resulted in satisfactory vision and a high rate of spectacle independence. Halos and glare were common.
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http://dx.doi.org/10.22608/APO.2018152DOI Listing
March 2019

Femtosecond laser-assisted astigmatic keratotomy: a review.

Authors:
John S M Chang

Eye Vis (Lond) 2018 12;5. Epub 2018 Mar 12.

Department of Ophthalmology, Hong Kong Sanatorium & Hospital, 8/F, Li Shu Pui Block, Phase II, 2 Village Road, Happy Valley, Hong Kong.

Background: Astigmatic keratotomy (AK) remains an accessible means to correct surgically induced or naturally occurring astigmatism. The advantages of femtosecond laser-assisted astigmatic keratotomy (FSAK) over conventional methods have been recognized recently.

Main Text: This review evaluates the efficacy, complications, and different methods of FSAK for correction of astigmatism in native eyes and those that underwent previous penetrating keratoplasty (PKP).The penetrating and intrastromal FSAK (IFSAK) techniques can reduce post-keratoplasty astigmatism by 35.4% to 84.77% and 23.53% to 89.42%, respectively. In native eyes, the penetrating and IFSAK techniques reduce astigmatism by 26.8% to 58.62% and 36.3% to 58% respectively, implying that the magnitude of the astigmatic reduction is comparable between the two FSAK procedures. Nonetheless, IFSAK offers the additional advantages of almost no risk of infection, wound gape, and epithelial ingrowth. The use of nomograms, anterior-segment optical coherence tomography, and consideration of posterior cornea and corneal biomechanics are helpful to enhance the efficacy and safety of FSAK. The complications of FSAK in eyes that underwent PKP include overcorrection, visual loss, microperforations, infectious keratitis, allograft rejection, and endophthalmitis. The reported difficulties in native eyes include overcorrection, anterior gas breakthrough, and suction loss.

Conclusions: In eyes that underwent PKP, FSAK effectively reduces high regular or irregular astigmatism, with rare and manageable complications. Nevertheless, the drawbacks of the procedure include the potential loss of visual acuity and low predictability. For native eyes undergoing femtosecond laser-assisted cataract surgery, IFSAK is a good choice to correct low astigmatism (< 1.5 diopters). The refractive effect of astigmatism from the posterior cornea needs to be considered in the nomograms for native eyes undergoing refractive cataract surgery. To further improve the efficacy of FSAK, more large-scale randomized studies with longer follow-up are needed.
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http://dx.doi.org/10.1186/s40662-018-0099-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5853056PMC
March 2018

Consultation Section: Refractive. June consultation #4.

Authors:
John S M Chang

J Cataract Refract Surg 2017 06;43(6):855-857

Hong Kong, China.

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http://dx.doi.org/10.1016/j.jcrs.2017.06.013DOI Listing
June 2017

Femtosecond Laser in situ Keratomileusis Flap Creation in Narrow Palpebral Fissure Eyes without Suction.

Case Rep Ophthalmol 2017 May-Aug;8(2):341-348. Epub 2017 Jun 6.

Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Hong Kong, Hong Kong.

Purpose: To evaluate a surgical technique used in eyes with narrow palpebral fissure undergoing femtosecond laser flap creation without suction during laser in situ keratomileusis (LASIK).

Methods: All data of 2 patient groups were collected through chart review. Group 1 consisted of 6 eyes with narrow palpebral fissure in which the suction ring was manually fixated and femtosecond laser was applied accordingly. Thirty comparison cases were randomly drawn from among eyes that underwent a standard LASIK procedure matched for age and preoperative refraction (group 2). Only 1 eye of each patient was selected to compare the refractive and visual outcomes between groups.

Results: In all group 1 eyes, the flaps were created successfully with manual fixation of the suction ring without suction. No eyes lost 2 or more lines of vision. No significant difference was found in the safety and refractive outcomes between groups.

Conclusion: Manual fixation of the suction ring in eyes with narrow palpebral fissure without suction was feasible for flap creation during LASIK.
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http://dx.doi.org/10.1159/000477201DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5498974PMC
June 2017

Visual Outcomes, Quality of Vision, and Quality of Life of Diffractive Multifocal Intraocular Lens Implantation after Myopic Laser In Situ Keratomileusis: A Prospective, Observational Case Series.

J Ophthalmol 2017 4;2017:6459504. Epub 2017 Jan 4.

Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Hong Kong.

. To report visual performance and quality of life after implantation of a bifocal diffractive multifocal intraocular lens (MIOL) in postmyopic laser in situ keratomileusis (LASIK) patients. . Prospective, observational case series. Patients with prior myopic LASIK who had implantation of Tecnis ZMA00/ZMB00 MIOL (Abbott Medical Optics) at Hong Kong Sanatorium and Hospital were included. Postoperative examinations included monocular and binocular distance, intermediate and near visual acuity (VA), and contrast sensitivity; visual symptoms (0-5); satisfaction (1-5); spectacle independence rate; and quality of life. . Twenty-three patients (27 eyes) were included. No intraoperative complications developed. Mean monocular uncorrected VA at distance, intermediate, and near were 0.13 ± 0.15 (standard deviation), 0.22 ± 0.15, and 0.16 ± 0.15, respectively. Corresponding mean values for binocular uncorrected VA were 0.00 ± 0.10, 0.08 ± 0.13, and 0.13 ± 0.10, respectively. No eyes lost >1 line of corrected distance VA. Contrast sensitivity at different spatial frequencies between operated and unoperated eyes did not differ significantly (all > 0.05). Mean score for halos, night glare, starbursts, and satisfaction were 1.46 ± 1.62, 1.85 ± 1.69, 0.78 ± 1.31, and 3.50 ± 1.02, respectively. Eighteen patients (78%) reported complete spectacle independence. Mean composite score of the quality-of-life questionnaire was 90.31 ± 8.50 out of 100. . Implantation of the MIOL after myopic LASIK was safe and achieved good visual performance.
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http://dx.doi.org/10.1155/2017/6459504DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5241461PMC
January 2017

Cataract Surgery with a New Fluidics Control Phacoemulsification System in Nanophthalmic Eyes.

Case Rep Ophthalmol 2016 Sep-Dec;7(3):218-226. Epub 2016 Oct 21.

Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Hong Kong, Hong Kong.

Purpose: To report visual outcomes and complications after cataract surgery in nanophthalmic eyes with a phacoemulsification system using the active fluidics control strategy.

Methods: This is a retrospective case series. All eyes with an axial length of less than 20 mm that underwent cataract surgery or refractive lens exchange using the Centurion Vision System (Alcon Laboratories Inc.) in Hong Kong Sanatorium and Hospital were evaluated. The visual acuity and intraoperative and postoperative complications were reported. Prior approval from the Hospital Research Committee has been granted.

Results: Five eyes of 3 patients were included. The mean follow-up period was 10.2 ± 5.3 months (range, 4-18). Two eyes (40%) had a one-line loss of corrected distance visual acuity. No uveal effusion and posterior capsular tear developed. An optic crack and haptic breakage in the intraocular lens developed in 1 eye (20%) and 2 eyes (40%), respectively. Additional surgeries to treat high postoperative intraocular pressure were required in 1 eye (20%).

Conclusion: The use of a new phacoemulsification system, which actively monitors and maintains the intraoperative pressure, facilitated anterior chamber stability during cataract surgery in nanophthalmic eyes. This minimized the risk of major complications related to unstable anterior chambers such as uveal effusion and posterior capsular tear. Development of intraoperative crack/breakage in a high-power intraocular lens was common.
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http://dx.doi.org/10.1159/000452158DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5121556PMC
October 2016

Visual Performance after Bilateral Implantation of a Four-Haptic Diffractive Toric Multifocal Intraocular Lens in High Myopes.

J Ophthalmol 2016 2;2016:5320105. Epub 2016 Aug 2.

Department of Ophthalmology, Hong Kong Sanatorium and Hospital, 8/F, Li Shu Pui Block, Phase II, 2 Village Road, Happy Valley, Hong Kong.

Background. The vision with diffractive toric multifocal intraocular lenses after cataract surgery in long eyes has not been studied previously. Objectives. To report visual performance after bilateral implantation of a diffractive toric multifocal intraocular lens in high myopes. Methods. Prospective, observational case series to include patients with axial length of ≥26 mm and corneal astigmatism of >1 dioptre who underwent bilateral AT LISA 909M implantation. Postoperative examinations included photopic and mesopic distance, intermediate, and near visual acuity; photopic contrast sensitivity; visual symptoms (0-5); satisfaction (1-5); and spectacle independence rate. Results. Twenty-eight eyes (14 patients) were included. Postoperatively, mean photopic monocular uncorrected distance, intermediate, and near visual acuities (logMAR) were 0.12 ± 0.20 (standard deviation), 0.24 ± 0.16, and 0.29 ± 0.21, respectively. Corresponding binocular values were -0.01 ± 0.14, 0.13 ± 0.12, and 0.20 ± 0.19, respectively. One eye (4%) had one-line loss in vision. Under mesopic condition, intermediate vision and near vision decreased significantly (all P ≤ 0.001). Contrast sensitivity at all spatial frequencies did not improve significantly under binocular condition (all P > 0.05). Median scores for halos, night glare, starbursts, and satisfaction were 0.50, 0.00, 0.00, and 4.25, respectively. Ten patients (71%) reported complete spectacle independence. Conclusions. Bilateral implantation of the intraocular lens in high myopes appeared to be safe and achieved good visual performance and high satisfaction.
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http://dx.doi.org/10.1155/2016/5320105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4985582PMC
August 2016

Comparison of refractive and visual outcomes with centration points 80% and 100% from pupil center toward the coaxially sighted corneal light reflex.

J Cataract Refract Surg 2016 Mar;42(3):412-9

From the Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Hong Kong Special Administration Region, China.

Purpose: To compare the refractive and visual outcomes between 2 ablation centration points, 80% and 100% from the pupil center toward the coaxially sighted corneal light reflex.

Setting: Hong Kong Sanatorium and Hospital, Hong Kong, China.

Design: Retrospective comparative study.

Methods: All eyes had myopic laser in situ keratomileusis with the ablation 80% or 100% from the pupil center toward the coaxially sighted corneal light reflex. Three months postoperatively, the refractive and visual outcomes were compared between groups. Subgroup analysis was also performed for the large-angle κ and small-angle κ groups.

Results: There were no differences in the preoperative variables between groups. Three months postoperatively, the sphere was significantly more hyperopic in the 80% group than in the 100% group (0.19 diopter [D] versus 0.09 D) (P = .009) and the cylinder was significantly lower in the 80% group (0.25 D versus 0.33 D) (P = .011). More eyes achieved zero astigmatism in the 80% group than in the 100% group (43.9% versus 34.2%), and fewer eyes had astigmatism greater than 0.75 D in the 80% group (0.9% versus 6.1%) (P = .039). The error from the target refraction indicated that the 80% group tended to have significantly less undercorrection (P = .045). There were no significant differences in the other outcomes. Subgroup analysis did not show significant findings for the large-angle κ.

Conclusions: Both 80% centration and 100% centration were safe and effective. Compared with the 100% group, the 80% group had less astigmatism and less undercorrection.
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http://dx.doi.org/10.1016/j.jcrs.2015.09.030DOI Listing
March 2016

Visual outcomes and patient satisfaction after refractive lens exchange with a single-piece diffractive multifocal intraocular lens.

J Ophthalmol 2014 23;2014:458296. Epub 2014 Nov 23.

Department of Ophthalmology, Hong Kong Sanatorium and Hospital, 8/F, Li Shu Pui Block, Phase II, 2 Village Road, Happy Valley, Hong Kong.

Purpose. To report visual outcomes and patient satisfaction after unilateral or bilateral refractive lens exchange (RLE) with a single-piece bifocal diffractive multifocal intraocular lens (MIOL). Methods. All patients underwent RLE with the ZMB00 MIOL (Abbott Medical Optics). Patient charts were reviewed to evaluate the distance, intermediate, and near visual acuity (VA), contrast sensitivity, extent of visual symptoms (0-5), satisfaction (1-5), and rate of spectacle independence between unilateral and bilateral RLE group. Results. Forty-seven eyes of 28 patients were included. No intraoperative complications developed. Mean monocular uncorrected VA at distance, intermediate (67 cm), and near (30 cm) were 0.01 ± 0.12 (standard deviation), 0.27 ± 0.18, and 0.15 ± 0.11, respectively. No eyes lost >1 line of corrected distance VA. Monocular contrast sensitivity remained at normal level. Median scores of halos, night glare, and starbursts for 27 patients were 2.0, 3.0, and 0.0, respectively. Median score of satisfaction was 4.0. There were no differences in visual symptom scores or satisfaction between unilateral and bilateral group (P > 0.05). Eighty percent of 25 patients reported total spectacle freedom, with similar rate between bilateral (82%) and unilateral group (75%) (P = 1.000). Conclusions. RLE with the bifocal diffractive MIOL was safe in presbyopic patients and resulted in a high rate of spectacle independence.
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http://dx.doi.org/10.1155/2014/458296DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4258327PMC
December 2014

Initial evaluation of a femtosecond laser system in cataract surgery.

J Cataract Refract Surg 2014 Jan 22;40(1):29-36. Epub 2013 Nov 22.

From the Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Hong Kong Special Administrative Region, China.

Purpose: To report the early experience and complications during cataract surgery with a noncontact femtosecond laser system.

Setting: Hong Kong Sanatorium and Hospital, Hong Kong Special Administrative Region, China.

Design: Retrospective case series.

Methods: All patients had anterior capsulotomy or combined anterior capsulotomy and lens fragmentation using a noncontact femtosecond laser system (Lensar) before phacoemulsification. Chart and video reviews were performed retrospectively to determine the intraoperative complication rate. Risk factors associated with the complications were also analyzed.

Results: One hundred seventy eyes were included. Free-floating capsule buttons were found in 151 eyes (88.8%). No suction break occurred in any case. Radial anterior capsule tears occurred in 9 eyes (5.3%); they did not extend to the equator or posterior capsule. One eye (0.6%) had a posterior capsule tear. No capsular block syndrome developed, and no nuclei were dropped during irrigation/aspiration (I/A). Anterior capsule tags and miosis occurred in 4 eyes (2.4%) and 17 eyes (10.0%), respectively. Different severities of subconjunctival hemorrhages developed in 71 (43.8%) of 162 eyes after the laser procedure. The mean surgical time from the beginning to the end of suction was 6.72 minutes ± 4.57 (SD) (range 2 to 28 minutes).

Conclusions: Cataract surgery with the noncontact femtosecond laser system was safe. No eye lost vision because of complications. Caution should be taken during phacoemulsification and I/A to avoid radial anterior capsule tears and posterior capsule tears.
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http://dx.doi.org/10.1016/j.jcrs.2013.08.045DOI Listing
January 2014

Sulcus fixation of a 3-piece diffractive multifocal intraocular lens with and without optic capture in the anterior capsulorhexis.

Ophthalmology 2014 Jan 21;121(1):429-430.e2. Epub 2013 Nov 21.

Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Hong Kong.

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http://dx.doi.org/10.1016/j.ophtha.2013.09.040DOI Listing
January 2014

Correlation Between Axial Length and Anterior Chamber Depth in Normal Eyes, Long Eyes, and Extremely Long Eyes.

Asia Pac J Ophthalmol (Phila) 2012 Jul-Aug;1(4):213-5

From the Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Hong Kong, China.

Purpose: The objective of this study was to investigate the correlation between axial length (AL) and anterior chamber depth (ACD) in normal to long eyes and in extremely long eyes.

Design: This was an observational cross-sectional study in a single-center, private hospital.

Methods: Axial length and ACD data were retrieved from the intraocular lens (IOL) Master database of patients who presented for IOL or phakic lens implantation. Only left eyes were included. The correlation between AL and ACD was tested with Pearson correlation coefficient in all eyes, normal to long eyes (AL < 27.5 mm), and extremely long eyes (AL ≥ 27.5 mm). P < 0.01 was statistically significant.

Results: The cohort was composed of 1184 eyes of 1184 Chinese patients. The mean age was 65.8 ± 13.3 years (range, 19-98 years). The mean AL and ACD were 24.73 ± 2.48 mm (range, 20.51-36.20 mm) and 3.09 ± 0.44 mm (range, 1.95-4.68 mm), respectively. Pearson correlation coefficients in all eyes, normal to long eyes (1026 eyes, 87%), and extremely long eyes (158 eyes, 13%) were 0.56 (P < 0.001), 0.59 (P < 0.001), and -0.15 (P = 0.67), respectively.

Conclusions: There was a statistically significant positive correlation between AL and ACD in normal and long eyes but not in extremely long eyes. No correlation between AL and ACD in extremely long eyes requires newer-generation IOL formulas (ACD included) to increase the accuracy of IOL implantation.
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http://dx.doi.org/10.1097/APO.0b013e31825f8cb6DOI Listing
June 2015

Visual outcomes and patient satisfaction after presbyopic lens exchange with a diffractive multifocal intraocular lens.

J Refract Surg 2012 Jul 18;28(7):468-74. Epub 2012 Jun 18.

Department of Ophthalmology, Hong Kong Sanotorium and Hospital, Hong Kong.

Purpose: To investigate the visual outcomes, severity of symptoms, and patient satisfaction after refractive lens exchange (RLE) with a diffractive multifocal intraocular lens (IOL).

Methods: A nonrandomized, unmasked, retrospective chart review study was performed. Patients who underwent RLE with ZMA00 (Abbott Laboratories) were identified from a hospital database. Eyes with preoperative uncorrected distance visual acuity or corrected distance visual acuity 20/20 or better were included. The study cohort comprised 45 eyes from 29 patients. Monocular uncorrected and distance-corrected visual acuity at distance, 67 cm, and 30 cm were measured 6 months postoperatively. A patient questionnaire assessing visual symptoms (halo, night glare, and starburst) and satisfaction with visual performance was administered.

Results: Six months postoperatively, mean uncorrected visual acuity (logMAR) was -0.10±0.13, 0.43±0.25 at 67 m (intermediate), and 0.18±0.05 at 30 m (near). Mean distance-corrected visual acuity at these distances was -0.02±0.06, 0.40±0.21, and 0.17±0.02, respectively. Twenty-seven patients completed the questionnaire. Patients reported postoperative halos (78%), night glare (26%), and starbursts (48%). All bilateral RLE patients were spectacle-free at all distances, whereas 50% of unilateral RLE patients required spectacles postoperatively. Bilateral RLE patients with habitual spectacle use preoperatively were the most satisfied with their postoperative visual performance.

Conclusions: Refractive lens exchange with the ZMA00 is an option for presbyopic correction; however, significant glare, halo, and starburst issues are subjectively reported.
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http://dx.doi.org/10.3928/1081597X-20120612-01DOI Listing
July 2012

Conductive keratoplasty to treat hyperopic overcorrection after LASIK for myopia.

J Refract Surg 2011 Jan 15;27(1):49-55. Epub 2010 Feb 15.

Guy Hugh Chan Refractive Surgery Centre, Department of Ophthalmology, Hong Kong Sonatorium and Hospital, Happy Valley, Hong Kong.

Purpose: to investigate the refractive outcomes and stability of conductive keratoplasty (CK) for retreatment of myopic LASIK overcorrection.

Methods: seven eyes (six patients) that were overcorrected after myopic LASIK by +1.00 to +2.75 diopters (D) manifest refraction spherical equivalent (MRSE) were retreated using CK. All eyes had insufficient stromal thickness for LASIK retreatment. LightTouch CK was performed at least 1 year after LASIK. Either 8 or 16 spots were applied at 7- and/or 8-mm zones on the cornea. Uncorrected distance visual acuity, manifest refraction, corrected distance visual acuity (CDVA), and postoperative complications were analyzed.

Results: mean MRSE after CK at last follow-up was +0.38 ± 0.52 D (range: -0.38 to +1.13 D). The change in MRSE ranged from -0.63 to -2.38 D. Mean MRSE after CK changed from -0.60 ± 2.07 D (range: -3.38 to +1.50 D) at 1 week to +0.45 ± 0.69 D (range: -0.38 to +1.38 D) at 12 months. Two eyes experienced an initial overcorrection of -2.75 D and -3.38 D, respectively, at 1 week after CK. Cylinder ≤0.75 D was induced in four eyes, whereas one eye had a 0.75-D reduction in cylinder. All eyes had CDVA of logMAR 0.10 or better. Two eyes lost one line of CDVA and no eyes lost more than one line.

Conclusions: lighttouch CK retreatment for over-corrected myopic LASIK can reduce the hyperopia but produces minimal change in cylinder, and may be appropriate for eyes with insufficient stromal tissue for repeated excimer laser surgery. Early regression occurs commonly.
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http://dx.doi.org/10.3928/1081597X-20100212-10DOI Listing
January 2011

Intraoperative flap re-cut after vertical gas breakthrough during femtosecond laser keratectomy.

J Cataract Refract Surg 2010 Jan;36(1):173-7

Department of Ophthalmology, Guy Hugh Chan Refractive Surgery Centre, Hong Kong Sanatorium and Hospital, Hong Kong, China.

We describe the management of intraoperative vertical gas breakthrough (VGB) during femtosecond laser flap creation in 3 patients. All eyes were immediately re-cut using 2 different microkeratomes, and the laser in situ keratomileusis treatments were completed on the same day. There were no postoperative complications. Corneal abrasion might predispose to VGB. Management of VGB is effective using microkeratomes. Caution is advised during placement of the suction ring and in eyes with preexisting corneal abrasion or loose epithelium if femtosecond laser keratectomy is used. The approach in terms of direction of the microkeratome re-cut is fundamental to the safety and successful re-cut with a microkeratome.
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http://dx.doi.org/10.1016/j.jcrs.2009.06.046DOI Listing
January 2010

Complications of sub-Bowman's keratomileusis with a femtosecond laser in 3009 eyes.

Authors:
John S M Chang

J Refract Surg 2008 01;24(1):S97-101

Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong.

Purpose: To assess the safety and complication rate of sub-Bowman's keratomileusis (SBK) in 3009 eyes.

Methods: The flaps were created using the IntraLase femtosecond laser, and excimer ablation was performed with the Bausch & Lomb H.Eye.Tech laser system. The complications of SBK were evaluated retrospectively. The types of complications were grouped into intra- and postoperative flap related.

Results: In 3009 SBK procedures, the total complication rate was 0.63%. Intra- and postoperative flap-related complication rates were 0.33% and 0.30%, respectively. Only 1 (0.033%) eye lost one line of best spectacle-corrected visual acuity from diffuse lamellar keratitis (DLK). Intraoperative complications included flap tear, free cap, bubble escape, and flap folds. Postoperative complications included DLK and epithelial ingrowth. Other flap-related complications such as uneven bed, buttonhole, short flap, flap striae, or wrinkles did not occur in this series. All intraoperative complications were managed within the same day.

Conclusions: The complication rate of SBK is low. Vision loss is also rare.
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http://dx.doi.org/10.3928/1081597X-20080101-17DOI Listing
January 2008