Eung Kweon Kim

Comparison of laser epithelial keratomileusis and photorefractive keratectomy for low to moderate myopia

Purpose: To compare the effectiveness, safety, and stability of laser epithelial keratomileusis (LASEK), a modified photorefractive keratectomy (PRK) technique, with those of conventional PRK for low to moderate myopia. Setting: Department of Ophthalmology, Yonsei University School of Medicine, Seoul, Korea. Methods: In this prospective study, 27 patients with a manifest refraction of –3.00 to –6.50 diopters were treated and followed for 3 months. In each case, PRK was performed in 1 eye and LASEK in the other eye. The first eye treated and the surgical method used in the first eye were randomized. Postoperative pain, epithelial healing time, uncorrected visual acuity (UCVA), manifest refraction, corneal haze, and surgical preference were examined in PRK‐ and LASEK‐treated eyes. Results: During the 3 month follow‐up, there were no significant between‐eye differences in epithelial healing time, UCVA, or refractive error. However, LASEK‐treated eyes had lower postoperative pain scores (P = .047) and corneal haze scores (1 month; P = .02) than PRK‐treated eyes. Seventeen patients (63%) preferred the LASEK procedure. Conclusions: Laser epithelial keratomileusis safely and effectively treated eyes with low to moderate myopia. It reduced the incidence of significant postoperative pain and corneal haze and may prevent the flap‐ and interface‐related problems of laser in situ keratomileusis.

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.

Ic3d Classification of Corneal Dystrophies—edition 2

Purpose: To update the 2008 International Classification of Corneal Dystrophies (IC3D) incorporating new clinical, histopathologic, and genetic information. Methods: The IC3D reviewed worldwide peer-reviewed articles for new information on corneal dystrophies published between 2008 and 2014. Using this information, corneal dystrophy templates and anatomic classification were updated. New clinical, histopathologic, and confocal photographs were added. Results: On the basis of revisiting the cellular origin of corneal dystrophy, a modified anatomic classification is proposed consisting of (1) epithelial and subepithelial dystrophies, (2) epithelial–stromal TGFBI dystrophies, (3) stromal dystrophies, and (4) endothelial dystrophies. Most of the dystrophy templates are updated. The entity “Epithelial recurrent erosion dystrophies” actually includes a number of potentially distinct epithelial dystrophies (Franceschetti corneal dystrophy, Dystrophia Smolandiensis, and Dystrophia Helsinglandica) but must be differentiated from dystrophies such as TGFBI-induced dystrophies, which are also often associated with recurrent epithelial erosions. The chromosome locus of Thiel-Behnke corneal dystrophy is only located on 5q31. The entity previously designated as a variant of Thiel-Behnke corneal dystrophy on chromosome 10q24 may represent a novel corneal dystrophy. Congenital hereditary endothelial dystrophy (CHED, formerly CHED2) is most likely only an autosomal recessive disorder. The so-called autosomal dominant inherited CHED (formerly CHED1) is insufficiently distinct to continue to be considered a unique corneal dystrophy. On review of almost all of the published cases, the description appeared most similar to a type of posterior polymorphous corneal dystrophy linked to the same chromosome 20 locus (PPCD1). Confocal microscopy also has emerged as a helpful tool to reveal in vivo features of several corneal dystrophies that previously required histopathologic examination to definitively diagnose. Conclusions: This revision of the IC3D classification includes an updated anatomic classification of corneal dystrophies more accurately classifying TGFBI dystrophies that affect multiple layers rather than are confined to one corneal layer. Typical histopathologic and confocal images have been added to the corneal dystrophy templates.

Comparison of tear secretion and tear film instability after photorefractive keratectomy and laser in situ keratomileusis

Purpose: To evaluate and compare tear secretion and tear film instability following photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Setting: Department of Ophthalmology, Yonsei University School of Medicine, Seoul, Korea. Methods: In a prospective study, 36 eyes (21 patients) had PRK and 39 eyes (25 patients) had LASIK to correct myopia. Tear secretion and tear film instability were tested preoperatively and 3 and 6 months postoperatively using Schirmer test values, tear breakup time (BUT) scores, and tear osmolarity. Results: Six months after surgery, the change in Schirmer test values from preoperative levels was –14.57% ± 6.39% (SD) in the PRK eyes and –23.40% ± 5.94% in the LASIK eyes and the change in BUT scores, –12.54% ± 8.28% and –18.79% ± 13.01%, respectively. The change in tear osmolarity was 14.95% ± 6.46% and 35.63% ± 8.51%, respectively. Conclusions: The decrease in tear secretion was greater after LASIK than after PRK at 6 months. Proper treatment of dry eye is required after LASIK and PRK, particularly in the LASIK postoperative period.

Accuracy of RTVue Optical Coherence Tomography, Pentacam, and Ultrasonic Pachymetry for the Measurement of Central Corneal Thickness

OBJECTIVE To compare the reliability and the agreement in measuring central corneal thickness (CCT) using the following technologies: RTVue Fourier-domain optical coherence tomography (Optovue, Inc., Fremont, CA), Pentacam (Oculus, Inc., Wetzlar, Germany), and ultrasonic pachymetry (USP; Pocket-II; Quantel Medical, Inc., Bozeman, MT). DESIGN Evaluation of diagnostic test. PARTICIPANTS One hundred four eyes of 52 healthy subjects (mean age ± standard deviation, 28.6 ± 4.8 years). METHODS One eye from each subject was assigned randomly for a repeatability test in which a single operator performed 3 successive measurements. The other eye underwent an interoperator reproducibility test by 3 operators. Two centering methods of RTVue and 3 types of CCT from Pentacam were investigated. For USP, 1 drop of topical anesthetic was administered, and measurement was initiated 90 seconds later. Agreement among the instruments was evaluated using Bland-Altman plots. MAIN OUTCOME MEASURES Various types of CCT were compared: central zone average and minimum thickness of RTVue centering on the vertex and the pupil; corneal thickness at the pupil center, apex, and thinnest location from Pentacam; and mean CCT of 5 repeated measurements of USP. The reliability of measurement was assessed using the repeatability or reproducibility coefficient (Rco), the coefficient of variation, and the intraclass correlation coefficient. The limit of agreement was used to analyze concordance. RESULTS The Rco of RTVue was 4 to 5 μm, which was comparable with that of USP and better than that of Pentacam (10-11 μm). The Rco was not dependent on centering methods (RTVue) or types of CCT (Pentacam). The location of minimum thickness found by RTVue was less reliable than that of the Pentacam. The central zone average of RTVue was approximately 7 μm larger than the pupil center or apex thickness of Pentacam and approximately 13 μm larger than the CCT measurement of USP. Those discrepancies could be as high as 20 and 23 μm, respectively. The minimum thickness measured by the RTVue was similar to that of Pentacam. CONCLUSIONS The RTVue is a rapid and reliable noncontact means of measuring CCT; however, the characteristics of CCT measured by RTVue must be understood when comparing the CCT obtained by the Pentacam or USP. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Comparison of corneal thickness after the instillation of topical anesthetics: proparacaine versus oxybuprocaine.

To compare changes in human corneal thickness after the instillation of proparacaine with those after oxybuprocaine instillation with time over a period of 10 minutes. Methods: Eighteen healthy young participants were recruited. Proparacaine was used in the right eye and oxybuprocaine in the left. Right and left baseline corneal thicknesses were measured every 30 seconds for 10 minutes using a noncontact specular microscope by 1 observer. Baseline corneal thickness was defined as the average of all values taken over 10 minutes. Changes in corneal thickness were measured every 20 seconds for 10 minutes after the administration of 1 drop of 0.5% proparacaine onto the right cornea and 1 drop of 0.4% oxybuprocaine onto the left cornea. Results: Mean baseline right cornea thickness was 531 ± 45 μm, and that of the left cornea was 531 ± 42 μm. The corneal thickness after proparacaine increased by 8.6 μm (∼4.5-12.6 μm, 95% CI) and then returned to baseline within 80 seconds. Corneal thickness after applying oxybuprocaine increased by 7.7 μm (3.6-11.2 μm, 95% CI) and then returned to baseline within 80 seconds. There was a second transient increase about 5 minutes later after proparacaine instillation but no additional transient increase after oxybuprocaine instillation. Conclusion: Oxybuprocaine is similar to proparacaine in terms of the severity of its effect on corneal thickness. Corneal thickness instability may occur for 5 minutes after proparacaine administration. Changes in corneal thickness after topical anesthetic instillation should be considered when performing measurements for refractive surgery or central corneal thickness in glaucoma patients.

Analysis of Tear Cytokines and Clinical Correlations in Sjögren Syndrome Dry Eye Patients and Non–Sjögren Syndrome Dry Eye Patients

PURPOSE To compare concentrations of tear cytokines in 3 groups composed of Sjögren syndrome (SS) dry eye, non-Sjögren syndrome (non-SS) dry eye, and normal subjects. Correlations between ocular surface parameters and tear cytokines were also investigated. DESIGN Prospective cross-sectional study. METHODS SS dry eye patients (n = 24; 40 eyes) were diagnosed with primary SS according to the criteria set by the American-European Consensus Group. Non-SS dry eye patients (n = 25; 40 eyes) and normal subjects (n = 21; 35 eyes) were also enrolled. Tear concentrations of interleukin (IL)-17, IL-6, IL-10, IL-4, IL-2, interferon γ (IFN-γ), and tumor necrosis factor α (TNF-α) were measured by a multiplex immunobead assay. Ocular Surface Disease Index (OSDI), tear film breakup time (TBUT), Schirmer I test, and fluorescein staining scores were obtained from dry eye patients. RESULTS All cytokine levels except for IL-2 were highest in the SS group, followed by non-SS dry eye group and control subjects. Concentrations of IL-17, TNF-α, and IL-6 were significantly different among the 3 groups (IL-17: SS > control P < .001, non-SS > control P = .042, SS > non-SS P < .001; TNF-α: SS > control P = .006, non-SS > control P = .034, SS > non-SS P = .029; IL-6: SS > control P = .002, non-SS > control P = .032, SS > non-SS P = .002). IL-17 was significantly correlated with TBUT (R = -0.22, P = .012) and Schirmer I test (R = -0.36, P = .027) scores in the SS group. IL-6 was significantly correlated only with TBUT (R = -0.38, P = .02) in the non-SS group. CONCLUSIONS Differences in tear cytokine levels and correlation patterns between SS dry eye and non-SS dry eye patients suggest the involvement of different inflammatory processes as causes of dry eye syndrome.

Central Corneal Thickness Measurements in Unoperated Eyes and Eyes After PRK For Myopia Using Pentacam, Orbscan II, and Ultrasonic Pachymetry

PURPOSE To compare central corneal thickness measurements obtained in unoperated eyes and eyes after myopic photorefractive keratectomy (PRK) using a rotating Scheimpflug camera (Pentacam), a scanning slit corneal topography system (Orbscan II), and ultrasonic pachymetry. METHODS Corneal thickness was measured using Pentacam, Orbscan II, and ultrasonic pachymetry in 25 unoperated eyes (unoperated group), 24 eyes 1 to 3 months after myopic PRK (early postoperative PRK group), and 21 eyes 4 months or more after myopic PRK (late postoperative PRK group). RESULTS In the unoperated group, corneal thickness measurements were similar for all three methods (P=.125). In the early postoperative PRK group, Orbscan measurements were thinner than Pentacam and ultrasonic measurements by a mean of 69.4 microm and 63.4 microm (P<.001 and P=.002, respectively). In the late postoperative PRK group, Orbscan measurements were thinner than Pentacam measurements by a mean of 36.0 microm (P=.017). Pentacam and ultrasonic pachymetry measurements were similar for all three groups with a mean difference of approximately 10 microm. CONCLUSIONS Following myopic PRK, Pentacam was comparable to ultrasonic pachymetry in measuring corneal thickness, whereas Orbscan measurements were thinner.

Inhibition of experimental corneal neovascularization by using subconjunctival injection of bevacizumab (Avastin).

Purpose: To evaluate the effect of subconjunctival bevacizumab (Avastin) administration on corneal neovascularization (NV) in rabbits. Methods: NV was induced by placing a suture at the corneal periphery of the right eye of 20 rabbits. Immediately after suturing and again 1 week later, rabbits were divided into 2 groups and administered a subconjunctival injection of normal saline (control) or bevacizumab (Avastin; 5 mg/0.2 mL), respectively. On day 14, digital photographs of the cornea were taken and analyzed to determine the area of the cornea covered by NV. In addition, immunohistochemical analysis was used to determine CD31 and vascular endothelial growth factor (VEGF) expression in corneal tissue. Results: Analysis of digital photographs showed that there was less corneal NV in bevacizumab-treated eyes than in controls (P < 0.001, Mann-Whitney U test). In addition, there was less staining for VEGF and CD31 in corneas from bevacizumab-treated eyes than in control eyes. Subconjunctival bevacizumab injections were not associated with any complications during observation. Conclusions: Subconjunctival bevacizumab administration decreased suture-induced corneal neovascularization in rabbits.

Bevacizumab application delays epithelial healing in rabbit cornea.

PURPOSE Vascular endothelial growth factor (VEGF) is essential for neovascularization, but the use of anti-VEGF therapies to inhibit neovascularization may influence epithelial wound healing. Here, the effects of bevacizumab on corneal epithelial wound healing time in rabbit models, cell proliferation, and expression of integrins in human corneal epithelial and fibroblast cells were evaluated. METHODS To compare epithelial wound healing times, epithelial defect sizes were measured after application of bevacizumab topical eye drops at 0, 0.5, 1.0, 1.5, 2.5, or 5 mg/mL, twice daily, to mechanically debrided epithelia of rabbit corneas. The cellular covering of wounded areas and expression of Ki67 were assessed after scrape injuries in cultures of human corneal epithelial and fibroblast cells. Expression of cell surface integrins and collagens was measured using plates coated with mouse monoclonal antibodies against human adhesion molecules, and relevant mRNA levels were assessed by reverse-transcription-polymerase chain reaction (RT-PCR). RESULTS The application of bevacizumab topical eye drops at 1.0, 1.5, 2.5, or 5 mg/mL delayed rabbit corneal epithelial healing. Cell cultures growing under high concentrations of bevacizumab showed delay in the proliferation of corneal epithelial and fibroblast cells. Surface expression of mRNA encoding integrins and collagens were decreased by 1.5 mg/mL of bevacizumab. CONCLUSIONS Bevacizumab delayed corneal epithelial wound healing and inhibited integrin expression. When bevacizumab is used to reduce the development of new corneal vessels, slight delays in epithelial wound healing are possible and cellular proliferation is to be expected.