Jin Hak Lee

EFFECT OF THE APPLICATION OF HUMAN AMNIOTIC MEMBRANE ON RABBIT CORNEAL WOUND HEALING AFTER EXCIMER LASER PHOTOREFRACTIVE KERATECTOMY

PURPOSEnWe investigated the influence of amniotic membrane application on corneal wound healing after excimer laser photorefractive keratectomy (PRK) in rabbits.nnnMETHODSnPRK of -9.9 D with an optical zone of 5.0 mm was performed on each right eye of 34 pigmented rabbits, which had been divided into two groups. In 17 eyes, preserved human amniotic membrane was applied in such a way that it covered the entire cornea for 48 h (amniotic group), and the other eyes formed the control group. The area of epithelial defect, inflammatory cell infiltration, the number of anterior stromal keratocytes, and corneal haze were evaluated.nnnRESULTSnIn all animals, the epithelium had healed completely within 3 days, and there was no difference between the two groups. At postoperative 12 and 24 h, the numbers of stromal inflammatory cells in the amniotic group were significantly lower than those in the control group (p = 0.009), and the numbers of anterior stromal keratocytes were significantly higher (p < 0.05). At postoperative weeks 2, 4, 6, 8, and 12, corneal haze scores in the amniotic group were lower than those in the control group (p < 0.05), and at postoperative week 12, the number of anterior stromal keratocytes in the amniotic group was significantly lower than that in the control group (p = 0.002).nnnCONCLUSIONnThe application of amniotic membrane after PRK reduces keratocyte proliferation and corneal haze during corneal wound healing, possibly by reducing the infiltration of inflammatory cells and loss of keratocytes in the ablation area during the early postoperative period.

Corneal endothelial dysfunction associated with amantadine toxicity.

Purpose: To describe bilateral corneal endothelial dysfunction in a patient with Parkinson disease who was treated with long-term amantadine. Methods: We employed an A-B-A-B single-subject research design that included clinical history, clinical findings, photographic images, and specular microscopic findings of ocular changes. Results: A 52-year-old woman with Parkinson disease who had taken amantadine for 6 years had bilateral corneal edema for 2 months at baseline. After cessation of amantadine, the edema resolved, and the endothelial cell densities were ≤600/mm2. Corneal edema recurred when the administration of amantadine was resumed. Therefore, amantadine was permanently discontinued and the cornea cleared again. Conclusions: Amantadine can cause reversible corneal edema but can irreversibly reduce the density of endothelial cells.

The effect of contact lens wear on the ocular surface changes in keratoconus.

Purpose. To investigate the effects of contact lens wear or the keratoconic shape itself on the changes in the ocular surface in keratoconus. Methods. Forty-two patients (84 eyes) were enrolled in this study and divided into four groups. Group 1 comprised 22 eyes with keratoconus that had been wearing rigid gas-permeable (RGP) contact lenses for an average of 5.54 ± 2.11 years. Group 2 comprised 24 myopic eyes that had been wearing RGP contact lenses for 6.42 ± 1.79 years. Group 3 comprised 20 eyes with keratoconus without any contact lens wear. Group 4 comprised 18 healthy eyes that were used as controls. The ocular surface changes were evaluated by determining the tear film breakup time and performing conjunctival impression cytology. The goblet cell densities, nucleus-to-cytoplasm ratio, and epithelial cell morphology in the four groups were compared with optical microscopy in the high-power field. Results. The tear film breakup times in groups 1 and 2 were significantly lower than those in groups 3 and 4. The goblet cell densities were 5.49 ± 1.75 and 5.82 ± 1.63 in groups 1 and 2, respectively, which were significantly lower (P<0.05) than the 8.79 ± 1.42 and 10.24 ± 2.10 in groups 3 and 4, respectively. There were no statistically significant differences in the goblet cell densities, nucleus-to-cytoplasm ratios, and epithelial cell morphologies between groups 1 and 2 and groups 3 and 4. Conclusions. The ocular surface changes in keratoconus may be directly related to contact lens wear and not to the keratoconic shape itself.

Changes of ocular higher order aberration in on- and off-eye of rigid gas permeable contact lenses.

Purpose. To investigate ocular higher order aberration (HOA) changes caused by rigid gas permeable (RGP) contact lens (CL) wear. Methods. Twenty-two eyes of 22 myopic patients and 14 eyes of 14 keratoconic patients who were fitted with an RGP CL were enrolled to examine ocular HOAs using a Hartmann-Shack wavefront sensor before and after RGP wear. Root mean square (RMS) values and Zernike coefficients in RGP-on and RGP-off eyes were compared for both myopic and keratoconic eyes, or between patient groups divided according to their prefitted total HOA value (RMS <0.33 &mgr;m or ≥0.33 &mgr;m in myopic eyes and RMS <0.46 &mgr;m or ≥0.46 &mgr;m in keratoconic eyes). All HOA values were recomputed for a 4-mm pupil for comparison purposes. Results. In keratoconic eyes, RGP CL changed the direction of vertical coma from −0.185 to 0.134 &mgr;m (p = 0.024). In the low HOA myopic group, total HOA increased from 0.23 to 0.35 &mgr;m (p = 0.006) by RGP CL wear, mainly due to increased coma aberration from 0.0951 to 0.2146 &mgr;m (p = 0.006). The direction of vertical coma changed from the inferior to superior cornea in the low HOA group (p = 0.020). In the high HOA keratoconic group, total HOA decreased from 0.54 to 0.36 &mgr;m (p = 0.049), and the direction of the vertical coma changed from the inferior to superior cornea (p = 0.049). Conclusions. RGP CL wear may enhance or reduce HOA based on original existing ocular aberration mainly through directional changes in vertical coma.

Effects of White-To-White Diameter and Anterior Chamber Depth on Implantable Collamer Lens Vault and Visual Outcome

PURPOSEnTo investigate the effects of anterior chamber depth (ACD) and white-to-white (WTW) diameter on vault in eyes with implantable collamer lenses (ICL V4, STAAR Surgical AG) and to evaluate the effect of vault on visual outcomes and other biometric changes.nnnMETHODSnTwenty-eight eyes of 16 patients who underwent ICL implantation were retrospectively reviewed. Patients were divided into two groups (A1, A2) according to preoperative ACD (> or = 3.3 mm and < 3.3 mm, respectively), two groups (B1, B2) based on WTW diameter (> or = 11.55 mm and < 11.55 mm, respectively), and two groups (C1, C2) according to the difference of ICL diameter and sulcus length (> or = 0.25 mm and < 0.25 mm, respectively). Vault, endothelial cell density, and visual performance were compared between each set of groups. Correlations of vault with WTW diameter, ACD, and diametric difference of the ICL from the sulcus were analyzed.nnnRESULTSnThe high ACD and WTW groups showed significantly higher vaults (0.59 +/- 0.32 mm and 0.57 +/- 0.36 mm, respectively) than the low ACD and WTW groups (0.26 +/- 0.17 mm and 0.25 +/- 0.14 mm, respectively; P = .01 and .01), whereas the differences of diameter between the sulcus and ICL were not related to significant vault differences. The WTW diameter wascorrelated more closely to the vault than the ACD or sulcus diameter (r = 0.70, P < .001), whereas the vault difference did not affect visual quality or endothelial cell density.nnnCONCLUSIONSnA high WTW diameter or ACD is likely to render a high vault, regardless of any difference in the ICL and sulcus diameters.

VSX1 gene and keratoconus: genetic analysis in Korean patients.

Purpose: The visual system homeobox 1 (VSX1) gene variants have recently been shown to be associated with keratoconus. To replicate this finding, we performed a genetic analysis of the VSX1 gene in a Korean case–control sample. Methods: Patients with keratoconus and healthy control subjects were recruited from Seoul National University Hospital. A diagnosis of keratoconus was made based on clinical examinations and the presence of characteristic topographic features. For all patients and controls, the whole coding region and the exon–intron junctions of the VSX1 gene were analyzed by direct sequencing. Results: Fifty-three patients with keratoconus and 100 healthy volunteers were included. We observed 2 novel missense substitutions (Leu17Val and Val199Leu) and 1 previously reported substitution (Gly160Val) in 6 of the 53 affected probands. Because these substitutions have been identified in unaffected individuals, they were not considered to be pathogenic. No intragenic polymorphism was associated with a significantly increased risk of keratoconus. Conclusions: We cannot confirm the previously reported association of the VSX1 gene variants with keratoconus. Our results suggest that the VSX1 gene and its mutations with amino acid changes do not play a major role in the pathogenesis of keratoconus.

Protective effect of ascorbic Acid against corneal damage by ultraviolet B irradiation: a pilot study.

Purpose: To determine the protective effect of ascorbic acid (ASA) against corneal damage by ultraviolet B (UVB) irradiation. Methods: Eight rabbits weighing 2.1-2.5 kg were randomly divided into 3 groups: a UVB group, an ASA group, and a control group. The UVB group was made up of 2 rabbits that were exposed to 6.84 J/cm2 of UVB irradiation at a peak wavelength of 306 nm for 17 min/d for 7 days. The ASA group was made up of 4 rabbits that were pretreated intravenously with ASA before being subjected to UVB irradiation. The control group was made up of 2 rabbits that were not subjected to ASA treatment or UVB exposure. After 7 days, the corneas were clinically evaluated for signs of epithelial damage, corneal haze, and neovascularization. After evaluation, the enucleated eyes were analyzed pathologically for signs of proliferation, nuclear change, inflammation, edema, and neovascularization. Results: More damage was observed in the irradiation groups (UVB and ASA groups) than in the control group for all clinical and pathologic parameters (P < 0.0001). Also, when each of the parameters was considered, more severe changes were observed in the UVB group than the ASA group (P < 0.0001), with the exception of nuclear changes, for which the comparison was not applicable. Conclusions: ASA protected the cornea against UVB irradiation in this pilot study; however, further evaluation using many animals is needed to establish its efficacy.

Contrast sensitivity after LASIK, LASEK, and wavefront-guided LASEK with the VISX S4 laser

PURPOSEnTo evaluate the changes in contrast sensitivity and glare after corneal refractive surgery for moderate myopia.nnnMETHODSnThe study comprised 267 eyes of 149 patients who underwent LASIK, laser epithelial keratomileusis (LASEK), or wavefront-guided LASEK with the VISX STAR S4. Contrast sensitivity was measured with VCTS 6500 before surgery and at 2 and 6 months postoperatively. Glare was evaluated using questionnaires and the ALC glare test at last follow-up. Contrast sensitivity at 2 and 6 months was compared with preoperative contrast sensitivity in each group. Glare sensitivity in each group was compared to normal controls.nnnRESULTSnContrast sensitivity did not change after LASIK (P > .05). Contrast sensitivity of 3 and 6 cycles per degree (cpd) at 2 months increased after LASEK (P < .05) and contrast sensitivity of 6, 12, and 18 cpd at 2 months and 3, 6, 12, and 18 cpd at 6 months improved in wavefront-guided LASEK (P < .05). Glare test and questionnaires did not show any significant difference between the groups.nnnCONCLUSIONSnWavefront-guided LASEK induced significant increases in contrast sensitivity of moderate myopes at high spatial frequencies under mesopic conditions by 6 months. Glare was not affected by the different refractive procedures.

Biocompatibility of nanocomposites used for artificial conjunctiva: in vivo experiments.

Purpose: To evaluate the biocompatibility of nanocomposites used for artificial conjunctiva. Methods: Fifty New Zealand white rabbits were used for the experiments. Nanocomposites of poly ϵ-caprolactone (PCL) and of PCL coated with polyvinyl alcohol (PCL+PVA), polyvinyl pyrrolidone (PCL+PVP), or chitosan (PCL+C), and amniotic membrane (AM) as a control, were cut into small disks with a diameter of 3.5 mm. The disks were inserted underneath the conjunctiva to measure their inflammation-inducing properties. To investigate epithelial adhesion and goblet cell differentiation, the disks were transplanted after round conjunctival excision. Cultivated conjunctival epithelial cells on nanocomposite were then transplanted onto the abdomen of Balb/c athymic mice. The number of inflammatory cells and the density of goblet cells were measured using hematoxylin and eosin, periodic-acid–Schiff, and immunohistochemistry after 2 weeks. Results: The number of inflammatory cells found inside of the inserts was as follows: 21 ± 4.9 for controls, 21 ± 15.1 for PCL, 49.6 ± 26.0 for PCL+PVP, 40.2 ± 17.1 for PCL+C, and 13.8 ± 3.9 for PCL+PVA. In PCL+PVA, the accumulation of inflammatory cells was significantly lower than in the controls (p < 0.01, Mann-Whitney U). The reepithelialization of conjunctival cells was accomplished in more than 75% of all disks except for the PCL+C. In addition, we found the differentiation of goblet cells in the following order from greatest to least: amniotic membrane, PCL, and PCL+PVP. Conclusions: Nanocomposites of PCL were biocompatible in rabbit conjunctiva, suggesting that PCL may be considered as a candidate for use in the development of artificial conjunctiva.

Five-year results of corneal tattooing for cosmetic repair in disfigured eyes.

Purpose: To investigate the 5-year results of corneal tattooing for cosmetic repair in disfigured eyes and identify the risk factors associated with complications. Methods: Corneal tattooing was performed in patients with stable corneal opacity and blind eyes. A total of 147 eyes of 147 patients who were followed up for at least 5 years after tattooing were enrolled in the study. The following valuables were included as potential risk factors for long-term complications: age, sex, duration of opacity before tattooing, and the presence of calcific plaque. Corneal tattooing was also performed in 6 rabbit eyes, and the stained eyes were enucleated at 6 months postoperatively for histological analysis. Results: The average follow-up time after surgery was 65 ± 5 months. Long-term complications such as reopacification or increased opacity, fading of color, and epithelial growth developed in 12% of the tattooed eyes between 2 and 4 years after surgery and most required reoperation. Univariate analysis of risk factors affecting recurrence or complications revealed no statistically significant differences among candidate factors. Histological results of the tattooed rabbit eyes showed that clumps of blackish granules were present in the anterior half of the stroma without any infiltration of inflammatory cells to the adjacent layers. Conclusions: Corneal tattooing in disfigured eyes provided a good cosmetic outcome more than 5 years after surgery.