Kátia Mantovani Bottós

Corneal asphericity and spherical aberration after refractive surgery

PURPOSE: To evaluate changes in corneal asphericity (Q) and spherical aberrations after refractive surgery using Scheimpflug imaging. SETTING: University of California, San Diego, Shiley Eye Center, La Jolla, California, USA. DESIGN: Cohort study. METHODS: After wavefront‐guided laser in situ keratomileusis, patients within ±0.50 diopter of plano and with an uncorrected distance visual acuity of at least 20/20 were evaluated. The Q values and corneal spherical aberration Zernike values were obtained using Scheimpflug imaging preoperatively and 1 to 3 months postoperatively. RESULTS: The study enrolled 177 myopic eyes and 32 hyperopic eyes. The mean Q value was −0.28 ± 0.11 (SD) and −0.22 ± 0.15, respectively, preoperatively and +0.35 ± 0.44 and −0.64 ± 0.31, respectively, postoperatively. The asphericity change was highly correlated with preoperative spherical equivalent (r2 = 0.81; P≤.001). The mean corneal spherical aberration was +0.21 ± 0.08 μm in myopic eyes and +0.36 ± 0.11 μm in hyperopic eyes preoperatively and +0.36 ± 0.17 μm and 0.00 ± 0.29 μm, respectively, postoperatively. The corneal spherical aberration changes were correlated with the amount of preoperative refractive error (r2 = 0.34; P<.001). There was a tendency for Q values and spherical aberrations to become more positive after myopic ablation and more negative after hyperopic ablation. CONCLUSIONS: Myopic and hyperopic corrections induced changes in the Q value and spherical aberrations in opposite directions (ie, positive and negative, respectively). The changes depended on the magnitude of the refractive correction. Financial disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Effect of corneal epithelium on ultraviolet-A and riboflavin absorption

PURPOSE To determine if the corneal epithelium prevents the collagen cross-linking effect. Using immunofluorescence microscopy after CXL, we indirectly analyzed the role of the epithelium as ultraviolet-A (UVA) shield as well as a barrier to riboflavin penetration. METHODS Fifteen freshly enucleated porcine eyes were divided into 3 groups. The corneal epithelium was kept intact in all groups. Five eyes served as control (Group 1). On group 2, eyes received tetracaine anesthetic drops and topical 0.1% riboflavin solution (10 mg riboflavin-5-phosphate in 10 mL 20% dextran-T-500). On Group 3, riboflavin was injected into the anterior chamber to allow penetration of the drug through the endothelium. Groups 2 and 3 were exposed to UVA (365 nm, 3 mW/cm(2)) for 30 minutes. Ultra-thin sections (8 µm) of the corneas were stained with anti-collagen type I and DAPI (4,6-diamidino-2-fenilindole dihydrocloride) and analyzed with fluorescence microscopy. RESULTS Corneas treated with UVA irradiation and intracameral injection of riboflavin (Group 3) showed greater pattern of collagen organization compared to groups 1 (Control) and 2 (riboflavin and tetracaine eye drops). A yellow stromal staining, which represents the riboflavin diffusion into the stroma, was only observed in eyes injected with riboflavin into the anterior chamber. CONCLUSION Using immunofluorescence microscopy in porcine corneas, we demonstrated that the corneal epithelium reduces the effectiveness of CXL by preventing the penetration of the drug and not by limiting the UVA transmittance. An inadequate intrastromal concentration of riboflavin may impair CXL effect.

Higher-order aberrations of age-related cataract

PURPOSE: To analyze higher‐order aberrations induced by different types of lenticular opacities. SETTING: Federal University of São Paulo, São Paulo, Brazil. METHODS: One hundred thirty‐eyes of 65 patients with bilateral cataract, classified according to the Lens Opacities Classification System III (LOCS III), had complete ophthalmic examinations, corneal topography (EyeSys Technologies), and wavefront analysis (LADARWave, Alcon Laboratories). Patients with cataracts that could not be measured by a Hartmann‐Shack sensor or those with coexisting ocular disease were excluded. Higher‐order aberrations were compared between the nuclear, cortical, and posterior subcapsular groups for statistical significance. RESULTS: One hundred five eyes of 65 patients were assessed. Twenty‐eight eyes (23.33%) had predominantly nuclear opacification (NO1‐NO6 and C1‐2), and 13 (10.83%) had mainly cortical opacification (C1‐4). Sixty‐four eyes (65.83%) had a mixed pattern of LOCS III classification, which hindered the establishment of a correlation between the aberrometry and cataract type. Eighteen eyes that presented with dense posterior subcapsular cataract (P4‐5) and 7 eyes with cortical C5 LOCS III classification were excluded. In eyes with nuclear opacification, the mean spherical aberration with a 6.0 mm pupil was 0.45 μm ± 0.17 (SD) and the mean coma was 0.29 ± 0.13 μm. In eyes with predominantly cortical cataract, the mean spherical aberration was 0.12 ± 0.10 μm and the mean coma was 0.49 ± 0.23 μm. The cortical cataract group had statistically significantly higher coma than the other groups (P<.001). The nuclear cataract group had statistically significantly higher spherical aberrations than the other groups (P<.001). CONCLUSIONS: Different types of early lenticular opacities induced different wavefront aberration profiles. Coma predominated in the cortical cataract group, and spherical aberration predominated in the nuclear cataract group.

Corneal Absorption of a New Riboflavin-Nanostructured System for Transepithelial Collagen Cross-Linking

Corneal collagen cross-linking (CXL) has been described as a promising therapy for keratoconus. According to standard CXL protocol, epithelium should be debrided before treatment to allow penetration of riboflavin into the corneal stroma. However, removal of the epithelium can increase procedure risks. In this study we aim to evaluate stromal penetration of a biocompatible riboflavin-based nanoemulsion system (riboflavin-5-phosphate and riboflavin-base) in rabbit corneas with intact epithelium. Two riboflavin nanoemulsions were developed. Transmittance and absorption coefficient were measured on corneas with intact epithelia after 30, 60, 120, 180, and 240 minutes following exposure to either the nanoemulsions or standard 0.1% or 1% riboflavin-dextran solutions. For the nanoemulsions, the epithelium was removed after measurements to assure that the riboflavin had passed through the hydrophobic epithelium and retained within the stroma. Results were compared to de-epithelialized corneas exposed to 0.1% riboflavin solution and to the same riboflavin nanoemulsions for 30 minutes (standard protocol). Mean transmittance and absorption measured in epithelialized corneas receiving the standard 0.1% riboflavin solution did not reach the levels found on the debrided corneas using the standard technique. Neither increasing the time of exposure nor the concentration of the riboflavin solution from 0.1% to 1% improved riboflavin penetration through the epithelium. When using riboflavin-5-phosphate nanoemulsion for 240 minutes, we found no difference between the mean absorption coefficients to the standard cross-linking protocol (p = 0.54). Riboflavin nanoemulsion was able to penetrate the corneal epithelium, achieving, after 240 minutes, greater stromal concentration when compared to debrided corneas with the standard protocol (p = 0.002). The riboflavin-5-phosphate nanoemulsion diffused better into the stroma than the riboflavin-base nanoemulsion.

Effect of collagen cross-linking in stromal fibril organization in edematous human corneas.

Purpose: To assess structural stromal modifications after riboflavin and UV-A exposure in edematous human corneas. Method: Fourteen eyes with corneal edema were enrolled in the study. In the cross-linking (CXL) group, 7 corneal buttons were obtained from 6 patients who underwent penetrating keratoplasty (PK) 7-90 days after the CXL treatment. The control group was composed of 7 corneal buttons with bullous keratopathy. After the PK, stromal modifications were investigated using immunofluorescence in all corneal grafts. All patients had at least 3 months of corneal edema and were in the eye bank list waiting for keratoplasty. Results: All corneas in the treated group showed a pronounced lamellar zone of collagen fibers highly organized in the anterior stroma, but there was not complete homogeneity between the samples. Corneas with advanced disease and stromal fibrosis were less compacted than ones with mild disease severity. Similarly, those ones that underwent PK 3 months after CXL also showed a decreased effect compared with those with a reduced time between the CXL and the PK. DAPI staining demonstrated a complete fragmentation of keratocytes nuclei in the anterior stroma in all treated corneas, which were absent in the control group. Conclusions: Our study showed an immediate effect of CXL with a limited long-term sustainability. Cross-linked corneas had a pronounced anterior zone of organized collagen fibers. Even the treated corneas with advanced bullous keratopathy and stromal fibrosis had histological evidence of collagen fibers organization, but this effect seems to be decreased compared with corneas in initial stages of the disease.

Hipertensão e retinopatia hipertensiva

Purpose: To investigate the relationship between hypertensive retinopathy (HR) and systemic hypertension (controled or not), gender, age and race. Methods: 1,954 patients who live in Piraquara, aged over 40 years were examined between 1998 and 2000, during a glaucoma, hypertension and diabetes screening program. Diabetics were excluded. Questionnaire, blood pressure, glycemia and IOP measurement, direct and indirect fundoscopy were performed for all 1,741 patients. Gans classification was used to study the retinal changes. Results: Considering 1,741 patients, 669 (38.43%) were hypertensive, 645 (37.05%) normotensive and 427 (24.53%) suspected of having hypertension. HR was found in 211 patients (12.12%). 136 (64.46%) were female and 75 (35.54%) male; 135 (63.98%) aged between 40-60 years and 76 (36.02%) aged over 60 years; 75.83% were white and 11.37% black; 154 (73%) were hypertensive, 17 (2.64%) normotensive and 40 (9.37%) hypertension suspects. 12.2% and 25.3% of the hypertensive patients under treatment or not, respectively, had signs of HR. Conclusion: The prevalence of HR was predominant in hypertensive patients comparing to normotensive and hypertension suspects (p<0.001, OR=5.32). Hypertensive patients without blood pressure control (p<0.01, OR=2.44), aged over 60 years (p<0.001, OR=1.85) and/or black ones (p<0.05 e OR= 1.67) are at increased risk to develop HR.