Choul Yong Park

MEASUREMENT OF ANGLE KAPPA AND CENTRATION IN REFRACTIVE SURGERY

Purpose of review Consideration of angle kappa is important for correct centration of refractive treatments. Decentered refractive treatment can cause photic phenomena including glare, halo, and deterioration of vision. This review highlights the concept of angle kappa, its measurement and distribution in normal populations, and the methods to compensate for large angle kappa in refractive surgery using laser or intraocular lenses (IOLs). Recent findings Determination of the treatment center is very important in refractive surgery. Moving the ablation center from the center of the entrance pupil to points near visual axis, such as the corneal light reflex (line of sight) or corneal vertex normal, results in less induction of higher order aberrations (including coma aberration) and either the same or better visual outcomes both in hyperopic and myopic eyes when compared to laser ablation centered on the entrance pupil. Decentration of multifocal IOLs can result in deterioration of postoperative visual function with induction of higher order aberrations. The occurrence of photic phenomena positively correlated with preoperative values of angle kappa. Summary There is a growing body of evidence that emphasizes the consideration of angle kappa in refractive surgery. Ignoring angle kappa may sometimes result in decentered treatment and aggravation of visual symptoms. Compensation for angle kappa is important for optimal correction of refractive error by either laser ablation or IOLs, especially for hyperopes and any eyes with large angle kappa.

Demonstration by Redox Fluorometry that Sulforaphane Protects Retinal Pigment Epithelial Cells against Oxidative Stress

PURPOSE To quantify the effects of oxidant challenge on the redox state of adult human retinal pigment epithelial cells using microscopic autofluorescence spectroscopy and to determine whether treatment with the isothiocyanate sulforaphane protects these cells against oxidative stress. METHODS Oxidative stress was evoked in ARPE-19 cells by H2O2 and tert-butyl hydroperoxide. Reduced nicotinamide nucleotides NAD(P)H were assessed by excitation at 366 nm with measurement of fluorescence at 450 nm. Oxidized flavoproteins were assessed by excitation at 460 nm with measurement of fluorescence at 540 nm. The ratio of these measurements served as the index of cellular redox status. RESULTS Redox ratio and cell viability decreased in a dose-dependent manner after oxidant exposure. ARPE-19 cells treated with sulforaphane maintained significantly higher redox ratio and cell viability. The ratio for sulforaphane-treated cells after exposure to 0.64 mM H2O2 was 2.64 +/- 0.19 compared with 1.77 +/- 0.16 in untreated cells (P = 0.001). At 1.2 mM H2O2, the redox ratio of sulforaphane-treated cells was 2.30 +/- 0.18 compared with 1.76 +/- 0.13 in untreated cells (P = 0.02). Similar results were observed after insult with tert-butyl hydroperoxide. CONCLUSIONS Redox fluorometry provides quantitative information on the redox status of living cells. Sulforaphane protects ARPE-19 cells from oxidative injury by induction of antioxidant phase 2 genes. The findings in this study describe a useful method for assessing antioxidant effects in live cells and support phase 2 gene induction as a potential treatment strategy for macular degeneration and diseases in which oxidative injury plays a causative role.

Femtosecond laser refractive surgery: Small-incision lenticule extraction vs. femtosecond laser-assisted LASIK

Purpose of review Small-incision lenticule extraction (SMILE) is a novel technique devised to correct refractive errors. SMILE circumvents excimer laser photoablation of cornea, as the stromal lenticule cut by femtosecond laser is removed manually. Smaller incisions and preservation of anterior corneal biomechanical strength have been suggested as some of the advantages of SMILE over femtosecond laser-assisted LASIK (FS-LASIK). In this review, we compared previous published results of SMILE and FS-LASIK. The advantage, efficacy and safety of SMILE are compared with FS-LASIK. Recent findings SMILE achieved similar efficacy, predictability and safety as FS-LASIK. Greater preservations of corneal biomechanical strength and corneal nerves were observed in SMILE when compared with LASIK or PRK. Additionally, the incidence of postoperative dry eye syndrome was found to be less problematic in SMILE than in FS-LASIK. Summary SMILE is a promising new surgery for refractive error correction. Prospective and retrospective studies of SMILE have shown that results of SMILE are similar to FS-LASIK. With advances in femtosecond laser technology, SMILE may gain greater acceptance in the future.

Immunosuppressive property of dried human amniotic membrane.

Purpose: To report the immunosuppressive property of dry human amniotic membrane (dHAM). Methods: Mouse splenocytes harvested from Balb/c mice were stimulated using functional-grade anti-CD3e antibodies for 4 days either with or without either of 2 commercial types of dHAM (Ambiodry 1 & 2, IOP Inc., Costa Mesa, Calif., USA) added to the culture media. The cell proliferation assay was performed to analyze the extent of splenocyte proliferation. Results: dHAMs significantly suppressed mouse splenocyte proliferation compared to control. The suppression by dHAM with intact amniotic epithelium (Ambiodry 2) was significantly stronger than dHAM without epithelium (Ambiodry 1). Conclusion: The immunosuppressive property of dHAM was demonstrated using an alloreactive splenocyte proliferation assay.

The Effect of Silica Nanoparticles on Human Corneal Epithelial Cells.

Ocular drug delivery is an interesting field in current research. Silica nanoparticles (SiNPs) are promising drug carriers for ophthalmic drug delivery. However, little is known about the toxicity of SiNPs on ocular surface cells such as human corneal epithelial cells (HCECs). In this study, we evaluated the cytotoxicity induced by 50, 100 and 150 nm sizes of SiNPs on cultured HCECs for up to 48 hours. SiNPs were up-taken by HCECs inside cytoplasmic vacuoles. Cellular reactive oxygen species generation was mildly elevated, dose dependently, with SiNPs, but no significant decrease of cellular viability was observed up to concentrations of 100 μg/ml for three different sized SiNPs. Western blot assays revealed that both cellular autophagy and mammalian target of rapamycin (mTOR) pathways were activated with the addition of SiNPs. Our findings suggested that 50, 100 and 150 nm sized SiNPs did not induce significant cytotoxicity in cultured HCECs.

Acute effect of bupivacaine and ricin mAb 35 on extraocular muscle in the rabbit

Purpose. To identify acute histologic change of extraocular muscles induced by bupivacaine or ricin mAb 35 injection. Methods. The superior rectus and inferior rectus of white rabbits were injected with bupivacaine (0.4 mg in 0.3 ml) or ricin mAb 35 (0.2 µg/kg in 0.3 ml). After 1, 2, and 4 weeks, the rectus muscles were harvested, and postinjection changes in the muscle layers were examined histopathologically. Results. Bupivacaine and ricin mAb 35 induced myotoxic changes in both the orbital and the global layers. However, the inflammation and the myofiber destruction produced by bupivacaine injection was localized to the injection site, which compared with the diffuse change induced by ricin mAb 35. Inflammation reduced rapidly over 2 weeks. Regenerating myofibers with a central nucleus were found at 1 week after injecting these myotoxins. Four weeks after injection, the acute changes induced by these two toxins respectively were much recovered with prominent myofiber regeneration. Conclusions. We found that extraocular muscle has a superb ability to recover from the acute injury induced by bupivacaine or ricin mAb 35, and the two myotoxins induce unique damage including the predilection of muscle layers and duration of damage persisted. Further investigation about the functional change during recovery from the myotoxin-induced injury of extraocular muscles is needed.

Evaluation of the pentacam ray tracing method for the measurement of central corneal power after myopic photorefractive keratectomy

Purpose: The study evaluated the ray tracing method [total corneal refractive power (TCRP)] in a Pentacam apparatus (Oculus, Wetzlar, Germany) for postoperative keratometry measurement after myopic photorefractive keratectomy (PRK). Methods: Manifest refraction (MR) and Pentacam analyses were performed preoperatively and at 6 months postoperatively after the PRK (STAR S4 IR CustomVue; Abbott Medical Optics/Visx) in 49 right eyes from 49 patients (age, 25.42 ± 3.51 years). Postoperative corneal power was calculated using the clinical history method (CHM) and compared with postoperatively measured simulated keratometry (simK), true net power (TNP) at 3 mm, and pupil-centered TCRP at the center, 1, 3, and 4 mm (TCRP0, TCRP1, TCRP3, and TCRP4). Vertex-distance-adjusted refractive change (delta-MR) at the corneal plane was also compared with various keratometric changes (delta-K). Results: Postoperative TCRP0, TCRP1, TCRP3, and TCRP4 showed no significant difference compared with that of the CHM. Postoperative simK was significantly higher than that of the CHM, whereas the TNP was significantly lower compared with that of the CHM. The delta-Ks measured by simK, TNP, and TCRPs were significantly smaller than delta-MR, and delta-TCRP4 showed the least difference [mean ± SD, 0.28 ± 0.55 diopters (D)] with delta-MR. The 95% limit of agreement between delta-MR and delta-TCRP4 was −0.85 to 1.31 D. The difference between delta-TCRP4 and delta-MR was <0.5 D in 55.1% and <1.0 D in 87.8% of the eyes studied. Conclusions: Although postoperative TCRPs showed no significant difference with CHM, delta-MR was still underestimated after myopic PRK.

Predicting postoperative astigmatism using Scheimpflug keratometry (Pentacam) and automated keratometry (IOLMaster).

Purpose: To compare keratometry measurements obtained using an automated keratometer (AK, IOLMaster) and a Scheimpflug keratometer (Pentacam) in predicting residual astigmatism after cataract surgery. Methods: Preoperative corneal astigmatism was calculated using preoperative refraction, an AK and a Scheimpflug keratometer (anterior corneal power [ACP] and true net power [TNP]) in 155 eyes of 107 Asian subjects. Phacoemulsification cataract removal and nontoric intraocular lens insertion (Akreos®MI-60™, Bausch & Lomb, Rochester, NY, USA) were performed through a 2.8 mm temporal clear corneal incision. Six months later, postoperative astigmatism (postA) was calculated using manifest refraction. Error angle (EA) and error magnitude (EM) of above keratometries (AK, ACP, and TNP) in prediction of postA was calculated. The correlation between preoperative astigmatism and postA was analyzed using power vectors (J0 and J45). Results: AK resulted in the lowest EM and ACP resulted in the lowest EA. Preoperative astigmatism (preA) measured using AK, ACP, and TNP showed significant correlation with postA in both J0 and J45 components. (AK: rJ0 = 0.554, rJ45 = 0.559, ACP: rJ0 = 0.346, rJ45 = 0.281, TNP: rJ0 = 0.409, rJ45 = 0.231). Preoperative refractive astigmatism showed no significant correlation in any components. Conclusions: PreA determined using AK showed superior performance in prediction of postA than ACP and TNP.

Systemic Comorbidities of Dry Eye Syndrome: The Korean National Health and Nutrition Examination Survey V, 2010 to 2012.

Purpose: To identify systemic comorbidities in patients with dry eye syndrome in South Korea. Methods: From 2010 to 2012, 17,364 participants aged 20 or older were randomly included in the nationwide Korean National Health and Nutrition Examination Survey V. The prevalence of dry eye syndrome and demographics of these patients were investigated. We performed conditional logistic regression analyses based on age, sex, residential area, education level, occupation type, and household income level to obtain the odds ratio for each systemic comorbidity among subjects with and without dry eye syndrome. Results: The prevalence of dry eye syndrome in this study was 10.4%. Age [adjusted odds ratio (AOR): 1.02], female gender (AOR: 3.01), and indoor occupation (AOR: 1.30) were associated with a higher prevalence of dry eye syndrome and found to be less prevalent in those residing in rural areas (AOR: 0.73) and with lower education levels (AOR: 0.66–0.99). With regard to systemic comorbidities, dyslipidemia (AOR: 1.63), degenerative arthritis (AOR: 1.56), rheumatoid arthritis (AOR: 1.44), thyroid disease (AOR: 1.79), and renal failure (AOR: 2.56) were associated with a significantly higher prevalence of dry eye syndrome. Conclusions: We found that patients with dry eye syndrome have a higher prevalence of several systemic comorbidities. A more comprehensive therapeutic approach considering the effect of systemic medication may be necessary in these patients.

Risk Factors for Pterygium in Korea: The Korean National Health and Nutrition Examination Survey V, 2010-2012.

AbstractThe aim of this study is to report general and age-specific risk factors for pterygium prevalence in the Korean population.This in an observational case series study.Data from total 24,812 participants (age 40 years or older) from the Korean National Health and Nutrition Examination Surveys conducted from 2010 to 2012 were retrieved. After applying exclusion criteria, data from 13,204 participants (821 with pterygium and 12,383 without) were used for univariate and multivariate analyses. General risk factors were identified and participants were grouped by decade: 40 s, 50 s, 60 s, 70 s, and 80+. Age-specific risk factors were investigated for each group.After univariate analysis, 2 multiple regression models were constructed. Model 1: age + sex + spherical equivalent (SE) + sun exposure hours + occupation (indoor vs outdoor) + residency area (rural vs urban) + education level; model 2: age + sex + SE + sun exposure hours. In model 1, older age (odds ratio [OR]: 1.05 95% confidence interval [CI]: 1.05–1.06), male gender (OR: 1.28, 95% CI: 1.01–1.61), and longer sun exposure hours (OR: 1.47, 95% CI: 1.11–1.94) were significant risk factors for pterygium prevalence whereas higher level of education (elementary school vs college, OR: 3.98, 95% CI: 2.24–7.06) and urban residency (vs rural residency, OR: 0.56, 95% CI: 0.45–0.70) were protective factors. Higher SE (OR 1.11, 95% CI: 1.03–1.19) refractive error was considered a risk factor when using model 2 for the analysis. Age-specific risk factors were different in each age group. Male gender was associated with higher pterygium prevalence in younger age groups while longer sun exposure (5+ hours/day) increased pterygium prevalence in older age groups.Previously characterized risk factors were also found in this large population study. However, we found that risk factors may vary according to the age group. Myopic eyes were found to have lower prevalence than hyperopic eyes.