Visual, Keratometric and Corneal Biomechanical Changes after Intacs SK Implantation for Moderate to Severe Keratoconus.

PURPOSE: To report visual outcomes and corneal biomechanical changes after femtosecond-assisted Intacs SK implantation in keratoconic eyes. METHODS: This prospective interventional case series is comprised of 32 keratoconic eyes of 25 patients with mean age of 23.8 ± 5.4 years. Uncorrected (UDVA) and corrected (CDVA) distance visual acuity, refraction, manifest refraction spherical equivalent (MRSE), keratometry, central corneal thickness (CCT), corneal hysteresis (CH) and corneal resistance factor (CRF) were measured preoperatively, and 1, 3 and 6 months postoperatively. RESULTS: Mean UDVA improved from 0.81 ± 0.3 LogMAR preoperatively to 0.53 ± 0.2 LogMAR six months postoperatively (P < 0.001). At 6 months, MRSE was significantly reduced only in eyes with moderate KCN (mean change, +2.61 ± 0.54 diopter [D]; P< 0.001). A significant improvement in sphere (mean change, +1.92 ± 0.37 D; P< 0.001) and mean keratometry (mean change, -3.34 ± 0.47D; P< 0.001) were observed. CCT increased from 446.1 ± 38 µm preoperatively to 462.2 ± 50 µm at six months (P < .001). CRF decreased from 6.5 ± 1.6 mmHg to 5.9 ± 1.1 mmHg six months after surgery (P = 0.02). CDVA, refractive cylinder and CH did not change significantly (P = 0.48, 0.203 and 0.55, respectively). Linear regression analysis disclosed that a decrease in CCT and moderate KCN are associated with higher CRF (standardized B,-0.513 and 0.314;P= 0.004 and 0.024, respectively; Adjusted R square = 0.353). CONCLUSION: Visual, refractive and keratometric indices remarkably improved in a parallel fashion. CRF was inversely associated with CCT. Changes in CRF represent the trend of changes in corneal biomechanics and thickness during the early postoperative months.

Long-term Results of an Accelerated Corneal Cross-linking Protocol (18 mW/cm2) for the Treatment of Progressive Keratoconus.

PURPOSE: To compare the long-term outcomes of accelerated and standard corneal cross-linking protocols in the treatment of progressive keratoconus. DESIGN: Prospective randomized clinical trial. METHODS: Thirty-one eyes with keratoconus were treated with an accelerated protocol (18 mW/cm(2), 5 min) and all contralateral eyes were treated with the standard method (3 mW/cm(2), 30 min) using the same overall fluence of 5.4 J/cm(2). RESULTS: At 18 months after the procedure, the standard group showed significant improvement in spherical equivalent (P < .05), K-readings (P < .05), Q value (P < .05), index of surface variance (P < .05), and keratoconus index (P = .008) and decline in central corneal thickness (P < .05), but no significant change in visual acuity, corneal hysteresis, corneal resistance factor, P2 area, or endothelial cell density. In the accelerated group, central corneal thickness was the only parameter with statistically significant change. However, neither of these parameters showed significant differences between the standard and the 18 mW/cm(2) accelerated protocol, except K-reading (P = .059) and index surface variance (P = .034). CONCLUSION: An accelerated cross-linking protocol, using 18 mW/cm(2) for 5 minutes, shows a comparable outcome and safety profile when compared to the standard protocol, but better corneal flattening is achieved with the standard method than the accelerated method. Overall, both methods stop the disease progression similarly. This study will continue to examine more long-term results.

Short-term comparison of accelerated and standard methods of corneal collagen crosslinking.

PURPOSE: To compare the 6-month results of accelerated and standard collagen crosslinking (CXL) treatment of progressive keratoconus. SETTING: Noor Eye Hospital, Tehran, Iran. DESIGN: Prospective randomized clinical trial. METHODS: Two groups of eyes (intervention and control) received corneal collagen crosslinking (CXL) treatment. The intervention group received accelerated CXL (18 mW/cm(2), 5 minutes), and the control group received standard CXL (3 mW/cm(2), 30 minutes). The eyes were evaluated for changes in the visual indices, refraction, and topography preoperatively and 1, 3, and 6 months postoperatively and regarding corneal rigidity indices and the endothelial cell count (ECC) preoperatively and at 6 months. RESULTS: The study evaluated 62 eyes (31 patient) in 2 groups. The mean changes in uncorrected (P = .733) and corrected (P = .646) distance visual acuities and manifest refraction spherical equivalent (P = .598) did not differ statistically significantly between the 2 groups. The central corneal thickness was higher in the standard group than the accelerated group (P = .025). The mean decrease in the maximum keratometry (K) (P = .865) and mean K (P = .974) and the mean changes in the asphericity (P = .272) were not statistically significantly different between the 2 groups. The mean changes in corneal hysteresis (CH) (P = .548) and the corneal resistance factor (CRF) (P = 1.000), CH-CRF (P = .282), and the area under the peak 2 (P = .260) were similar in both groups. The mean decrease in the ECC was not statistically significantly different between the 2 groups (P = .218). CONCLUSION: Based on 6-month results, accelerated and standard corneal CXL arrested the progression of keratoconus similarly. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Clinical results with two different pharmaceutical preparations of riboflavin in corneal cross-linking: an 18-month follow up.

BACKGROUND: Comparison of long-term clinical results of two different pharmaceutical formulations used in corneal cross-linking (CXL) in keratoconus patients. METHODS: Sixty eyes of 60 keratoconus patients underwent CXL in two groups. We used riboflavin preparations from Sina Darou, Iran in group A, and Streuli Pharma, Switzerland in group B. Here we made inter-group comparison of changes in vision, refraction, Pentacam indices, corneal biomechanical indices, and endothelial cell count (ECC) 18 months after CXL. RESULTS: Since four patients were lost to follow-up, 56 eyes (28 eyes in each group) were compared. Mean improvement in uncorrected visual acuity (UCVA) was 0.31 ± 0.65 LogMAR (P=0.014) in group A and 0.24 ± 0.62 LogMAR (P=0.082) in group B. Best corrected visual acuity (BCVA) remained quite unchanged in both groups (P=0.774). Mean spherical refractive error reduced by 0.45 ± 1.15 diopter (D) (P=0.041) in group A and 0.27 ± 1.73 D (P=0.458) in group B (P=0.655). Cylinder error and spherical equivalent had a similar trend without any change. Max-K (P=0.006) and mean-K (P=0.044) decreased significantly more in group A compared to group B. The reduction in CCT was significantly more in group A than group B (P=0.004). Q-value was quite unchanged in both groups (P=0.704). The inter-group difference in CH reduction was borderline significant statistically (P=0.057). Changes in corneal resistance factor and endothelial cell count were not significantly different between two groups (P=0.117 and P=0.229). CONCLUSION: Clinical results of CXL with the domestic preparation of riboflavin are similar to that achieved with the Swiss made product in some aspects, and it is the preferred brand in some other aspects. This study will continue to report longer follow-up results. TRIAL REGISTRATION: IRCT201212034333N2.

Comparison of clinical results of two pharmaceutical products of riboflavin in corneal collagen cross-linking for keratoconus.

BACKGROUND: To compare the 6-month results of two formulations of Riboflavin provided by Sina Darou, Iran, and Uznach, Switzerland, in corneal collagen cross-linking (CXL) for keratoconus patients. FINDINGS: Considering the results of the previous study about the similarity of the formulations and the active ingredients of the two types of Riboflavin, they were used in the CXL procedure of 60 keratoconic eyes (30 eyes in each group). After 6 months, the mean improvement of UCVA (0.239), BCVA (0.707), and MRSE (0.513) did not differ significantly between the two groups. The mean decrease in max- K (0.731), mean- K (0.264), central corneal thickness (0.759), and Q-value (0.669) did not show any significant difference between the two groups. The two groups had no significant difference in endothelial cell count decrease (0.229). The Sina Darou formulation decreased corneal hysteresis more than the Swiss formulation (P = 0.057) but there were no significant differences in the mean decrease of corneal resistance factor between the two groups (P = 0.117). CONCLUSIONS: Based on the early results, the results of visual acuity, refraction, and corneal topography using Sina Darou and Uznach formulations of Riboflavin showed that both were effective in CXL. However, considering the relatively significant difference in corneal hysteresis changes between the two groups, this study will continue to report the long-term results.