RESUMO
To compare results of different methods for true corneal power determination and intraocular lens [IOL] power calculation formulas in 10 eyes of 7 patients with previous radial keratotomy [RK] with or without astigmatic keratotomy.In this case series study, we determined the corneal power of 10 eyes of 7 patients who had undergone RK with or without astigmatic keratotomy with two methods: the contact lens method [CLM] and the mean keratometry of the 3 mm zone in topography. In the next step, the IOL power for these eyes was calculated with the 3 formulas of SRK II, SRK T, and Holladay II; the latter was used for the IOL selection. Refractive results were determined 3 month after surgery. According to the rule that 1.5 diopter [D] change in IOL power results in 1.0 D change in a patient's refraction at the spectacle plane, we estimated the manifest refraction of these eyes with other formulas and compared them with the results achieved by Holladay II formula. Using the CLM and Holladay II formula, the postoperative manifest refraction spherical equivalent in 8 eyes ranged from -3.00 to +2.00 D. Both CLM and the mean keratometry of the 3 mm zone in topography lead to a greater degree of hyperopia after cataract surgery with SRK II formula than SRK T, and with SRK T than Holladay II. The mean spherical equivalent with mean keratometry of the 3 mm zone in topography and Holladay II formula was 0.08 D, and with CLM and Holladay II formula was -0.05 D. In this study, it seemed that after RK, the mean keratometry of the 3 mm zone in topography gives a better estimate of true corneal power compared with CLM, and that the Holladay II formula brings results closer to emetropia compared with SRK II and SRK T formulas
RESUMO
To study the effect of prophylactic application of mitomycin-C on regression and corneal haze formation after photorefractive keratectomy [PRK] for high myopia. Fifty-four eyes of 28 high myopic patients were enrolled in this prospective study. All eyes underwent PRK with application of 0.02% mitomycin-C for two minutes and irrigation with 15-20 ml of normal saline. Follow-up visits were scheduled for the first 7 days and 1, 3 and 6 months after surgery. Hanna grading [in the scale of 0 to 4+] was used to assess corneal haze. Mean spherical equivalent [SE] refraction was -7.08 +/- 1.11 diopters [D], preoperatively. All eyes were examined on the first 7 days and one month after surgery; 48 eyes [88.9%] were evaluated 3 and 6 postsurgery. Six months after surgery, all eyes had uncorrected visual acuity [UCVA] of 20/40 or better and 37 eyes [77.1%] achieved UCVA of 20/20 or better, 45 eyes [93.7%] had SE within +/- 1.00D of emmetropia. One month postoperatively, 2 eyes [3.7%] had grade 0.5 haze, while at 3 and 6 months after surgery no visited eye had haze at all. There was no decrease in best corrected visual acuity after 6 months. In spatial frequencies of 6 and 12 cycle/degree, contrast sensitivity decreased immediately after PRK but increased to the preoperative values by the 6th postoperative month. Mitomycin-C can prevent the development of corneal haze when treating high myopia with PRK. In patients with insufficient corneal thickness for laser in situ keratomileusis [LASIK], mitomycin-C makes a useful adjunct to PRK to provide an alternative treatment for myopia. However, further research with longer follow-up is suggested