Elastic properties and scanning electron microscopic appearance of manual continuous curvilinear capsulorhexis and vitrectorhexis in an animal model of pediatric cataract.

PURPOSE: To compare the tear resistance of anterior capsulotomies using manual continuous curvilinear capsulorhexis (CCC) and vitrector-cut capsulotomy (vitrectorhexis) techniques in an animal model of the pediatric eye and in 2 pairs of human infant eyes. SETTING: Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: Continuous curvilinear capsulorhexis and automated vitrectorhexis capsulotomy techniques were performed in 20 pig eyes, 10 with each technique. The capsules were then stretched until they ruptured. The forces required for rupture after each technique were compared. The forces required for rupture of the pig eye lens capsule were also compared with those required for the human infant eye lens capsule. Scanning electron microscopy was performed in each group following intraocular lens (IOL) insertion. RESULTS: All capsules stretched adequately for IOL insertion. The percentage of stretch prior to rupture was higher in the capsulorhexis group (mean 157%, range 147% to 169%) than in the vitrectorhexis group (mean 135%, range 124% to 147%) (P < .001). The percentage of stretch in the human infant eyes was not statistically different from that in the porcine eyes (P > .05). CONCLUSIONS: The manual CCC offered greater resistance to capsule tearing than the vitrectorhexis and also revealed a more smooth, regular edge. It therefore remains the gold standard. However, the vitrectorhexis displayed more than adequate resistance to unwanted anterior capsule tears when used for IOL insertion through capsulotomy sizes currently used in clinical practice.

Predictive value of regression and theoretical IOL formulas in pediatric intraocular lens implantation.

PURPOSE: Intraocular lenses (IOLs) are being implanted in children with greater frequency and in a wider age range. The accuracy of available regression and theoretical formulas in predicting correct IOL power for pediatric eyes, however, has not been reported. METHODS: We reviewed medical records of 47 consecutive pediatric IOL implantations after cataract extraction that met inclusion criteria. Age at surgery ranged from 2 months to 10 years, with measured axial lengths of the eye between 18.6 and 26.7 mm. For the purpose of this study, the 2-month postoperative refraction was considered the post-IOL refractive outcome. Using preoperative globe axial length, corneal curvature, IOL power, and the A constant for the lens provided by the manufacturer, we employed the four common IOL power formulas (one regression formula [SRK-II] and three theoretical formulas [SRK-T, Holladay, and Hoffer Q]) to predict refractive outcome. RESULTS: The average difference between predicted and actual postoperative refractive error ranged from 1.2 to 1.4 diopters (D) for all formulas. Predicted postoperative refraction was less than the actual in 89 calculations and greater in 99. No significant differences in predictive accuracy were found in any of the axial length groups (group 1 P = 0.79, group 2 P = 0.42, and group 3 P = 0.86). All formulas were slightly less accurate in group 3 patients (shortest eyes). In this group, the Hoffer Q formula had the lowest error (1.4 D) and the SRK-II had the highest error (1.8 D). The difference was not statistically significant (P = .86). CONCLUSIONS: In our pediatric study eyes, all four IOL power calculation formulas predicted mean refractive outcome within 1.4 D. Theoretical formulas did not outperform the regression formula.

5-Fluorouracil reduces scarring after strabismus surgery.

PURPOSE: To examine the effect of topically administered 5-fluorouracil during strabismus surgery on post-operative scarring and the strength of the tendon-muscle union. METHODS: Bilateral superior and inferior rectus muscle recessions were performed on 10 Stauffland white rabbits. The operated muscles in one eye received a 5-min topical application of 50 mg/mL solution of 5-fluorouracil (5-FU). The fellow eye received placebo treatment with a 5-min application of balanced sterile saline. Both eyes were enucleated 29 days postoperatively and examined for evidence of scarring. The tensile strength of both treated and untreated muscles was measured. Two additional rabbits received no surgery but had their eyes enucleated to serve as controls for tensile strength measurements. RESULTS: A significant reduction (P = 0.0001) in the amount of scarring was noted in eyes treated with 5-FU. A reduction in the tensile strength of both operated groups compared with the unoperated groups (P = 2.72 x 10(-12)) was noted, with a small but significant difference between the two operated groups (P = 0.0423). CONCLUSION: This study suggests that 5-FU may be a useful adjunctive therapy in strabismus surgery, especially when extensive postoperative scarring is expected.

Long-term effects of hydrophilic contact lenses on myopia.

Myopic patients aged 14 to 19 years were divided randomly into two groups: those that wore contact lenses full time and those that wore spectacles only as age-matched controls. These two groups were analyzed statistically for any difference in the rate of progression of myopia. Refraction records were screened and analyzed using the unpaired Student's t test. We found no statistically significant difference between the two groups. There appears to be no effect of soft contact lens wear on the progression of myopia.