Utility of orthokeratology contact lenses; efficacy of myopia correction and level of patient satisfaction in Iranian myopic/myope-astigmatic patients.

PURPOSE: To investigate the medical profiles of patients referred to Iran Lens Clinic with myopic/myope-astigmatic refractive errors. METHODS: Medical records of 182 patients (364 eyes) with myopic/myope-astigmatic refractive errors that underwent orthokeratology contact lens wear and fulfilled a 6-month period of follow-up were recruited. Efficacy and safety of these contact lenses in improving the visual acuity and correction of the refractive errors were investigated. Time needed to achieve final targeted visual acuity and association of various factors in this time course and level of acuity were investigated. Complications related to these lenses that were recorded in the medical profiles were studied. RESULTS: In manifest refraction, the amount of spherical equivalent and myopia decreased significantly after orthokeratology contact lens wear (P < 0.001). A significant negative association was found between amount of mean baseline spherical equivalent and final achieved mean uncorrected visual acuity (P < 0.001). None of the parameters of age, gender, and keratometric findings influenced the outcomes significantly (P > 0.1). CONCLUSION: Patients with myopic refractive error lower than -5.0 Diopters achieved higher final visual acuities rather than patients with higher amounts of myopic refractive errors.

Rigid contact lens fitting based on keratometry readings in keratoconus patients: predicting formula.

AIM: To find a simple mathematical correlation between the lens base curve (BC) and keratometry findings (krf). METHODS: This retrospective study included 400 keratoconic eyes (350 patients) previously fit with rigid contact lenses at an academic eye center over a five year period. The patients were classified into five groups based on the keratometry findings (krf<7, krf:7-8, krf>8, krf-krs (difference between two keratometry; flat and steep)= 0.3-0.6, krf-krs >0.6mm as groups 1 to 5, respectively. Multivariate linear regression and Munro's correlation coefficient were employed to defer the formulas. RESULTS: A linear correlation could be found in all groups except for patients in group 3. For group 1, BC=0.211×krf+ 5.904. For group 2, BC=0.456×krf+4.160. For group 4, BC= 0.321×krf+5.219. For group 5, BC=0.337×krf+ 5.090. CONCLUSION: The development of new formulas for RGP fitting enables ophthalmologists to work with confidence and prevents unnecessary and frequent lens trials. The customary lens fitting methods are needed to be replaced by new formulas, which help to save time and costs.