Gas permeable toric use and applications: survey of Section on Cornea and Contact Lens Diplomates of the American Academy of Optometry.

BACKGROUND: The purpose of this study was to survey Diplomates in the Section on Cornea and Contact Lenses of the American Academy of Optometry (AAO) to determine their fitting preferences for astigmatic patients, lens materials used, and their perception of simplicity or complexity of bitoric fitting. METHODS: A total of 180 practitioners, representing all active Diplomates in the Cornea and Contact Lens Section, were sent a survey of 11 questions pertaining to their astigmatic contact lens prescribing habits. Sixty-eight (38%) of those surveyed responded to the questionnaire. RESULTS: The results of this survey included the following: (1) gas permeable (GP) lenses represented 28.7% of all contact lenses fit; (2) a spherical power effect (SPE) bitoric lens was preferred (versus four other options) by 58.8% of respondents for a 3.5 diopter (D) refractive astigmat with no residual astigmatism, whereas a cylinder power effect (CPE) bitoric was preferred by 55.9% for a 3.5 D refractive astigmatic with more than 1 D of residual astigmatism; (3) only 10.4% of responding practitioners consider GP torics to be difficult to fit. CONCLUSIONS: (1) Back surface toric and bitoric GP lenses are considered easy to design and fit by most Diplomates. (2) The Mandell-Moore guide is the preferred empirical method, and the Polycon SPE is the preferred diagnostic fitting method for bitoric lenses for those responding to the survey.

Evaluation of corneal sensitivity to mechanical and chemical stimuli after LASIK: a pilot study.

PURPOSE: To evaluate the effect of laser in situ keratomileusis (LASIK) on corneal sensitivity, nerve morphology, and tear film characteristics. METHODS: A cross-sectional study design was used. Eighteen patients (eight men and 10 women with a mean age of 36.9 +/- 11.2 years) who had undergone bilateral LASIK for low myopia within 18 months of the study and 28 control subjects (16 men and 12 women with a mean age of 27.2 +/- 7.7 years) were enrolled. Central and inferior corneal thresholds to mechanical (air) and chemical (air plus carbon dioxide) stimuli were determined by using a staircase technique. Stimuli of a 1-second duration at 34 degrees C were delivered with a CRCERT-Belmonte aesthesiometer. Images of subbasal nerves in the central cornea were captured with confocal microscopy. Nerve morphology was classified as no nerves, short nerves (<175 microm), or long nerves (>175 microm), with or without interconnections. Noninvasive tear break up time was measured. The phenol red thread test was used to indicate basal tear secretion. Differences between groups were evaluated with analysis of variance, and associations between variables were evaluated with parametric or nonparametric correlation, when appropriate. RESULTS: Central corneal mechanical sensitivity was significantly reduced in the post-LASIK group compared with the control subjects (P < 0.001). Nerve morphology was associated with mechanical threshold. Nerve morphology, mechanical sensitivity, and tear breakup time improved during the first 1 to 3 months after surgery, with little change thereafter. Chemical sensitivity was associated with tear secretion (P < 0.05). CONCLUSIONS: Central corneal mechanical sensitivity is reduced in patients after LASIK, with partial recovery seen 3 months after surgery. A similar recovery trend is seen for nerve morphology.