Hungwon Tchah

The Effect of Topical Bevacizumab on Corneal Neovascularization

PURPOSE To examine the effect of topical bevacizumab on corneal neovascularization (NV) over a period of 3 months. DESIGN Prospective, nonrandomized, masked observational case series. PARTICIPANTS Ten eyes of 7 patients with corneal NV. METHODS Patients received topical bevacizumab (1.25%) twice daily. Ophthalmic evaluations included visual acuity, slit-lamp examination, and tonometry. MAIN OUTCOME MEASURES Corneal NV and changes in ophthalmic evaluations. RESULTS Decreased corneal NV was noted in 7 of 10 eyes, usually within 1 month of treatment. Epitheliopathy (epithelial defect, epithelial erosion) was observed in 6 of 10 eyes, 1 resulting in corneal thinning. Adverse effects generally appeared during the second month of treatment. CONCLUSIONS Topical application of bevacizumab was effective in reducing corneal NV within the first month. However, by the second month there was an increased risk of adverse effects.

Bilateral comparison of wavefront-guided versus conventional laser in situ keratomileusis with bausch and lomb zyoptix

PURPOSE One aim of corneal refractive surgery is to correct defocus and astigmatism. In the process of correcting lower order aberrations, higher order ocular aberrations increase. To evaluate the effectiveness of wavefront-guided laser in situ keratomileusis (LASIK) in reducing the increase of higher order aberration, we compared aberrational change after LASIK with conventional and wavefront-guided customized ablation. METHODS Our study included 48 eyes of 24 patients. We performed conventional LASIK in one eye (Group 1) and wavefront-guided customized ablation in the other eye (Group 2). Ocular aberration was measured with the Zywave, a type of Shack-Hartmann aberrometer. We then compared low and high order aberrations, contrast sensitivity, visual acuity, corneal topography, and manifest refraction preoperatively and postoperatively at 1 and 3 months. RESULTS Uncorrected visual acuity improved to more than 20/20 in two eyes in the conventional ablation group and in five eyes in the customized ablation group. In the conventional ablation group, Root-mean-square for higher order (RMS(H)) was 0.215 preoperatively, 0.465 (216.3%) at 1 month, and 0.418 (194.4%) at 3 months. In the customized ablation group, RMS(H) was 0.207 preoperatively, 0.380 (183.6%) at 1 month, and 0.371 (179.2%) at 3 months after LASIK. Mesopic contrast sensitivity in the customized ablation group was higher than that in the conventional ablation group, but this change was not statistically significant. CONCLUSIONS Wavefront-guided customized ablation reduced the increase of high order aberrations resulting from LASIK. In terms of visual acuity, patient preference, and mesopic contrast sensitivity, wavefront-guided customized ablation produced slightly-but not statistically significant-better results.

Objective evaluation of through-focus optical performance of presbyopia-correcting intraocular lenses using an optical bench system

PURPOSE: TO evaluate spherical aberration and through‐focus optical performances of 5 presbyopia‐correcting and 2 monofocal intraocular lenses (IOLs). SETTING: Flaum Eye Institute, University of Rochester, Rochester, New York, USA. DESIGN: Experimental study. METHODS: Five presbyopia‐correcting IOLs (Restor +4D SN6AD3, Restor +3D SN6AD1, Rezoom NXG1, Tecnis multifocal ZM900, Crystalens HD500) were tested using an optical bench system consisting of a model eye, a high‐resolution Hartmann‐Shack wavefront sensor, and an image‐capturing device. Two monofocal IOLs (Sofport AO LI60AOV, Acrysof SN60AT) were measured for comparison. No accommodation was simulated. The spherical aberration profiles of each IOL were measured using the wavefront sensor. Through‐focus performance was evaluated by calculating cross‐correlation coefficients and comparing the likenesses of captured images of a resolution target and a perfect reference image. RESULTS: With a 5.0 mm entrance pupil, the SN6AD3, SN6AD1, ZM900, NXG1, and HD500 IOLs had spherical aberration of −0.18 μm, −0.14 μm, −0.15 μm, −0.07 μm, and −0.01 μm, respectively. Distance image quality was poorer with multifocal and accommodating IOLs than with monofocal IOLs. All multifocal IOLs had effective distance and near image quality but had a loss in intermediate image quality. The HD 500 accommodating IOL had decreased distance image quality and slightly increased depth of focus compared with the monofocal IOLs because of the bispheric design. CONCLUSIONS: The presbyopia‐correcting IOLs had different optical characteristics, including spherical aberration profile and through‐focus performance. An accurate understanding of the optical characteristics of individual IOLs is essential to selecting the best presbyopia‐correcting IOL and thus improving cataract surgery outcomes. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Mitomycin C, ceramide, and 5-fluorouracil inhibit corneal haze and apoptosis after PRK.

Purpose: To investigate the effects of mitomycin C (MMC), ceramide, and 5-fluororacil (5-FU) on haze after photorefractive keratectomy (PRK) and exposure to ultraviolet B (UVB) radiation. Methods: The right eyes of 42 New Zealand white rabbits were treated with PRK to correct −10 diopter with a 5-mm optical zone. Sponges soaked in 0.02% MMC, 10 or 40 μmol/L ceramide, or 0.5% 5-FU were applied to the right eyes of 6 rabbits each, and a tarsorrhaphy was performed. Eight weeks after complete healing, topical 0.02% MMC or 0.5% 5-FU was applied twice daily to the right eyes of 6 rabbits that had previously received PRK but no topical medication. The control group of 6 rabbits was treated only with PRK. Three weeks after PRK, all the laser-treated eyes were exposed to 100 mJ/cm2 UVB radiation. Corneal haze was assessed biomicroscopically every 2 weeks using the Fantes scale. Eyes were enucleated 2, 7, and 13 weeks after PRK, and tissue specimens were stained with hematoxylin and eosin and with Apostain. Results: Corneal haze was observed in all rabbits after PRK and was aggravated by UVB irradiation. When applied immediately after PRK, MMC induced corneal opacity and apoptosis of keratocytes, but, at later times, this reagent significantly suppressed opacity, Apostain-positive keratocytes and reactivation of keratocytes, even after UVB irradiation. In contrast, ceramide and 5-FU suppressed corneal opacity after PRK, but this effect was not sustained after UVB irradiation. Conclusions: MMC is a potent inhibitor of haze induced by PRK and UVB irradiation. Throughout the process of corneal wound healing, the severity of apoptosis and reactivation of keratocytes was closely correlated with haze formation.

Photoastigmatic refractive keratectomy in 168 eyes: Six-month results

Abstract Using a 193 nm excimer laser, we performed elliptical astigmatic and spherical corneal ablation on 168 eyes with compound myopic astigmatism and analyzed the three‐ and six‐month postoperative results. Mean preoperative astigmatism was 1.51 ± 0.81 diopters (D). Mean three‐ and six‐month postoperative astigmatism was 0.70 ± 0.58 D and 0.67 ± 0.60 D, respectively. Six months after surgery, eyes with less than 1.00 D preoperative astigmatism improved 4.8%. The improvement was 53.5% and 59.1 % for eyes with a preoperative astigmatism of 1.00 D to 2.00 D and above 3.00 D, respectively. Overall, astigmatism improved 55.6%. There was a wide distribution from overcorrection to undercorrection. Astigmatism six months after surgery was within 10 degrees of the preoperative axis in 46.1 % of eyes.

Human cadaver corneal thinning for experimental refractive surgery.

Human cadaver eyes can be dehydrated by prolonged elevation of intraocular pressure (three to five hours) or by hyperosmotic Dextran over a 20- to 30-minute period. We divided four pairs of donor eyes into two groups (A and B) and dehydrated four corneas by each method. After corneal thinning to 500 to 600 microns, central corneal pachymetry was measured every ten minutes during the rehydration period for one hour, with each cornea pair being moistened at a different rate (every 30 seconds, 1 minute, 2.5 minutes or 5 minutes). The resultant increase in central corneal thickness noted by change in pachymetry (delta P) ranged from 12.4% to 14.7% over one hour between the two groups. delta P did not differ significantly between groups A and B, regardless of the varying rate of balanced salt solution irrigation of the corneas. Thus, it appears that either method of corneal dehydration provides comparable stability of corneal thinning for at least one hour to allow consistent corneal dynamics for experimental refractive surgery.

Prevalence of Granular Corneal Dystrophy Type 2 (Avellino Corneal Dystrophy) in the Korean Population

Purpose: This study investigates the prevalence of granular corneal dystrophy type 2 (GCD2; Avellino corneal dystrophy) in the Korean population. Methods: GCD2 homozygotes were identified through a collaboration of Korean referral centers for corneal disease. The genetic status of the patients and their immediate families were verified by DNA analysis. A lower bound for the gene prevalence was calculated using a model based on the Hardy-Weinberg principle. A second population-based model was developed to correct for known underestimation in the primary model. The corrected model used population data from the 2005 Korean census and fertility rates from historical Korean census data. Results: We identified 21 individuals homozygous for GCD2 (R124H mutation) from 16 Korean families. From this, we estimate that the overall prevalence (combining heterozygotes and homozygotes) is at least 8.25 affected persons/10,000 persons. Our corrected estimate for overall prevalence is 11.5 affected persons/10,000 persons. Conclusion: We present the first estimate of the prevalence of GCD2. Although uncommon, the prevalence of GCD2 in Korea is greater than anticipated. We believe that our approach could potentially be applied to estimating the prevalence of other rare diseases.

Effect of laser in situ keratomileusis on retinal nerve fiber layer thickness measurements by scanning laser polarimetry

Purpose: To determine the effect of laser in situ keratomileusis (LASIK) on retinal nerve fiber layer measurements by scanning laser polarimetry in a large clinical trial. Setting: Asan Medical Center, University of Ulsan, Department of Ophthalmology, Seoul, Korea. Methods: Scanning laser polarimetry measurements were performed in 59 eyes of 59 consecutive patients who had LASIK. The mean retardation values of the whole measurement ellipse and of the superior, inferior, temporal, and nasal sectors of the ellipse before and after LASIK were compared statistically. Results: The mean spherical equivalent refractive error was −6.10 diopters (D) ± 2.34 (SD) (range −1.19 to –15.50 D) preoperatively and –0.31 ± 0.52 D (range +0.68 to –2.13 D) postoperatively. The mean ablation depth was 94.0 ± 30.49 &mgr;m (range 28.0 to 161.1 &mgr;m). The mean postoperative retardation values of all the sectors and of the superior, temporal, inferior, and nasal sectors showed reduced nerve fiber layer thickness (P = .000, P = .000, P = .011, P = .000, and P= .002, respectively). Conclusion: Laser in situ keratomileusis affected nerve fiber layer thickness measurements by scanning laser polarimetry. The change in nerve fiber layer thickness was probably due to modification of the corneal architecture. This effect of keratorefractive surgery should be considered when using scanning laser polarimetry as a diagnostic and follow‐up tool for glaucoma.

A novel mutation of the decorin gene identified in a Korean family with congenital hereditary stromal dystrophy.

Purpose: To identify mutations in the decorin (DCN) gene in family members with congenital hereditary stromal dystrophy (CHSD). Methods: Bilateral deep anterior lamellar keratoplasties using a big-bubble technique and a 60-kHz femtosecond laser (IntraLase; Abbott Medical Optics, Irvine, CA) for zig-zag incisions were performed for the patients with CHSD. Medical records were reviewed for the probands daughter with the same corneal manifestation who had bilateral penetrating keratoplasty 8 years before. After obtaining informed consent from the pediatric patients and their guardians, we sampled the peripheral blood of 2 patients and the probands son who had no clinical manifestation of CHSD. Genomic DNA was extracted from white blood cells. Eight exons and exon–intron boundaries of the DCN gene were amplified by polymerase chain reaction using specific primers for each exon. The polymerase chain reaction products were subsequently analyzed using the direct DNA sequencing method. Results: The proband and her daughter showed typical pathological findings of CHSD, such as lamellae of normal collagen fibrils separated by layers of abnormal collagen filaments, as seen on electron microscopic examination. A novel mutation c.947delG (p.Gly316AspfsX12) was identified in the exon 8 of the DCN gene, which might lead to an abnormal truncation of the C-terminal in the decorin protein. However, the probands son who was without any sign of CHSD showed a normal sequence of the DCN gene. Conclusions: We report a novel frameshift mutation of the DCN gene in a Korean family with CHSD.

Mitomycin C inhibits recurrent Avellino dystrophy after phototherapeutic keratectomy.

Purpose: To report 4 patients with Avellino corneal dystrophy (ACD) who were treated with 0.02% mitomycin C (MMC) during phototherapeutic keratectomy (PTK). Methods: ACD was confirmed by polymorphism of the exon region in the BIGH3 gene using polymerase chain reaction followed by DNA sequencing analysis. Three patients with recurrent ACD and 1 patient with primary ACD underwent PTK. Intraoperative 0.02% MMC was applied topically with a soaked microsponge. Results: There was no recurrence of ACD in the heterozygotes, but there were recurrences with best-corrected visual acuity of 20/30 in the 2 homozygotes. Conclusion: Intraoperative use of topical 0.02% MMC in conjunction with PTK may prevent or delay the recurrence of ACD for at least for 1 year.