Corneal Cross-Linking With Verteporfin and Nonthermal Laser Therapy.

PURPOSE: To test whether verteporfin with a nonthermal laser increases corneal mechanical stiffness and resistance to enzymatic degradation ex vivo. METHODS: Thirty human corneas (n = 5 per group) were treated with verteporfin alone (V), irradiated with nonthermal laser therapy (689 nm) alone (NTL), or received combined treatment of verteporfin with nonthermal laser therapy for 1 sequence (V+NTL1) or 6 sequences (V+NTL6) of 1 minute of NTL exposure. Positive controls were pretreated with 0.1% riboflavin/20% dextran every 3 to 5 minutes for 30 minutes and irradiated with ultraviolet light type A (λ = 370 nm, irradiance = 3 mW/cm) for 30 minutes using the Dresden protocol (R+UVA). Untreated corneas were used as negative controls. The corneal biomechanical properties were measured with enzymatic digestion, compression, creep, and tensile strength testing. RESULTS: V+NTL6- and R+UVA-treated corneas acquired higher rigidity and more pronounced curvature than untreated corneas. The stress-strain tests showed that V+NTL6 and R+UVA corneas became significantly stiffer than controls (P < 0.005). The V+NTL6 group seemed to be slightly stiffer than the R+UVA group, although the differences were not statistically significant. V+NTL6 corneas were found to have a significantly lower absolute creep rate (-1.87 vs. -3.46, P < 0.05) and significantly higher maximum stress values (7.67 vs. 3.02 P < 0.05) compared with untreated corneas. CONCLUSIONS: Verteporfin-NTL (V+NTL6) increases corneal mechanical stiffness and resistance to enzymatic collagenase degradation. Although a clinical study is needed, our results suggest that V+NTL6 induces corneal cross-linking and corneal biomechanical changes that are similar to those induced by standard corneal collagen cross-linking.

Anterior chamber depth in normal subjects by rotating scheimpflug imaging.

PURPOSE: Anterior chamber depth (ACD) is an important preoperative parameter in anterior segment surgery. Several factors are known to influence ACD, including race and geography. Our purpose was to sample data from various countries to characterize differences in ACD worldwide and, if any, assess their level of clinical significance. SETTING: International, multicenter. METHODS: Cross-sectional study. Using the Pentacam Eye Scanner (OCULUS GmbH, Wetzlar, Germany), we analyzed ACD measurements from 1077 eyes of 568 normal adults from nine countries spanning six continents. Differences between countries were assessed by comparison of 95% confidence intervals and by ANOVA. Normative thresholds were constructed at three standard deviations (SD) above and below the mean. RESULTS: Mean ACD was 3.11 mm overall, ranging from 2.91 mm (New Zealand) to 3.24 mm (United States). The ACD among New Zealanders was significantly shallower (P < .0001) than that among Chinese, Egyptians, Germans, Indians, and Americans. The maximum difference in the mean ACDs was 0.33 mm, between New Zealand and the United States. The shallowest 0.15% of normal ACD values occurred below 2.04 mm overall, ranging from 1.69 mm (New Zealand) to 2.42 mm (United States). The deepest 0.15% of normal ACD values occurred above 4.18 mm overall, ranging from 4.03 mm (Saudi Arabia) to 4.35 mm (Brazil). CONCLUSIONS: ACD did not vary significantly in the countries studied, with the notable exception of New Zealand. Surgeons should anticipate a greater likelihood of a shallow ACD when evaluating patients from New Zealand. Clinical examination and direct measurement of ACD are recommended. Finally, deep ACD has limited clinical utility in screening for keratoconus.