Intraocular lens power calculation for cataract surgery after photorefractive keratectomy.

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Clinical and theoretical results of intraocular lens power calculation for cataract surgery after photorefractive keratectomy for myopia.

Item does not contain fulltextOBJECTIVES: To describe the refractive results of cataract surgery after photorefractive keratectomy (PRK) for patients with myopia, and to find a more accurate method to predict intraocular lens (IOL) power in these cases. DESIGN: Nonrandomized, retrospective clinical study. PATIENTS AND METHODS: Nine patients (15 eyes) who underwent cataract surgery after prior PRK to correct myopia were identified. The medical records of both the laser and cataract surgery centers were reviewed. MAIN OUTCOME MEASURES: Eight different keratometric values (K values; measured or calculated) were entered into 3 different IOL calculation formulas: SRK/T, Holladay 1, and Hoffer Q. The actual biometry and IOL parameters were used to predict postoperative refraction, which was compared with the actual refractive outcome. Also, the relative underestimation of the refractive change in corneal dioptric power by keratometry after PRK was calculated. RESULTS: In 7 of 15 eyes, IOL exchange or piggybacking was performed because of hyperopia. Retrospectively, the most accurate K value for IOL calculation was found to be the pre-PRK K value corrected by the spectacle plane change in refraction. Use of the Hoffer Q formula would have avoided postoperative hyperopia in more cases than the other formulas. The mean underestimation of the change in corneal power after PRK varied from 42% to 74%, depending on the method of calculation. CONCLUSION: The predictability of IOL calculation for cataract surgery after PRK can be improved by using a corrected, refraction-derived K value instead of the measured, preoperative K value

Increased prevalence of disciform macular degeneration after cataract extraction with implantation of an intraocular lens.

After cataract extraction with implantation of an intraocular lens the increased transmission of ultraviolet and blue light may accelerate the development of age-related macular degeneration by producing free radicals in the retina. The maculae of 82 randomly selected postmortem human pseudophakic eyes and 16 fellow phakic eyes were examined by light microscopy. The presence of a basal laminar deposit, hard and soft drusen, thickening and calcification of Bruch's membrane, geographic atrophy, subretinal neovascularisation, and disciform scars was assessed in a standardised way. An age-matched series of 126 postmortem phakic eyes was used as control group. There was no difference between the two groups, except for a higher prevalence of hard drusen (exact trend test, p = 0.038) and disciform scars for the pseudophakic eyes (Fisher's exact test, p = 0.007). There was no significant correlation between either age-related changes in the macula or disciform degeneration and the length of time between cataract surgery and death. No significant difference was found between pseudophakic eyes with or without ultraviolet filter. These findings do not confirm that disciform scar formation is caused by an increase in ultraviolet or blue light