Browsing by Author "Yilmaz, OF"

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Changes in Anterior Chamber Depth and Axial Length Measurements After Radial Keratotomy
(Royal Coll Ophthalmologists, 1999) Demirok, A; Çinal, A; Simsek, S; Vasar, T; Bayram, A; Yilmaz, OF
Purpose To evaluate the changes that occur in anterior chamber depth and globe axial length after radial keratotomy (RK) surgery in cases with different degrees of myopia. Methods One hundred and twelve eyes that underwent RK were studied. The eyes were divided into two groups: 70 eyes with a correction of myopia of 4.00 D and under after RK (group 1) and 42 eyes with a correction of myopia of more than 4.00 D (group 2). Routine examinations were done in all cases. Ultrasonic biometry and central anterior chamber depth and axial length were measured pre-operatively and on the third day, second week, third month and sixth month post-operatively. Results Pre-operatively the average globe axial length was longer in group 2 than group 1. When all post-operative measurements were compared with pre-operative measurements in group 1, there was a decrease in anterior chamber depth and globe axial length, but no significant difference was found except on the third day (t = 3.15, p = 0.003). In group 2 there was an insignificant decrease in axial length but the decrease in anterior chamber depth was significant at all measurement times except for the sixth month. Conclusions Refractive changes related to biometric changes after RK are not important compared with the total refractive corrections of RK. These changes should be considered, however, when planning RK procedures.
The Effect of Altitude on Radial Keratotomy
(Elsevier Science inc, 1998) Simsek, S; Demirok, A; Cinal, A; Yasar, T; Yilmaz, OF
The authors analyzed refractive results of patients who underwent radial keratotomy (RK) at sea level and high altitude and evaluated the effects of the altitude. A total of 102 eyes undergoing RK procedures performed in two clinical centers having different altitude were analyzed. The results compared between subjects who had undergone RK at sea level (Istanbul/Turkey) and at an altitude of 5750 feet (Van/Turkey) were compared. Subjects were 19-42 years old with myopia from -4.00 to -12.00 diopters (D). The average preoperative spherical equivalent cycloplegic refractions (SECR) were -8.01 +/- 1.86 D and -6.99 +/- 2.15 D in the istanbul and Van groups, respectively. These were divided into subgroups according to myopia degree and number of incisions and optic zone size. The RK procedures were performed by the same surgeon with diamond blade in standard Russian style. The average changes in SECR were 5.09 +/- 1.29 D and 6.50 +/- 2.24 D in subjects who had undergone RK at sea level and at 5750 feet, respectively. There was a significant difference between the subgroups (P < 0.0002). This difference was especially higher in the high myopia subgroups. Additionally, we obtained a partial relation between increase of RK incision number and SECR change at high altitude but not at sea level. No notable regression and progression were seen in the 3 months of follow up at high altitude. These results support hy potheses suggesting both corneal hypoxic expansion in the area of RK incisions, which may lead to central corneal flattening, and barometric pressure directly altering corneal shape, which is responsible for the hyperopic shift induced by altitude. Ophthalmologists performing RK surgery at high altitude had better consider redesigning their RK nomograms in light of these findings. However, when the nomogram used at sea level was used at high altitude, the subjects became hyperopic. (C) 1998 Japanese Ophthalmological Society.
Effect of Superior and Temporal Clear Corneal Incisions on Astigmatism After Sutureless Phacoemulsification
(Elsevier Science inc, 1998) Simsek, S; Yasar, T; Demirok, A; Cinal, A; Yilmaz, OF
Purpose: To evaluate the effect of superior and temporal clear corneal incisions on astigmatism after sutureless, small incision phacoemulsification. Setting: World Eye Hospital, Istanbul, Turkey. Methods: This prospective study evaluated 40 eyes of 20 patients with cataract having bilateral, sutureless, small incision phacoemulsification by the same surgeon. A superior clear corneal incision was used in all right eyes and a temporal clear corneal incision in ail left eyes. Mean preoperative astigmatism was 0.63 diopter(D) +/- 0.21 (SD) and 0.65 +/- 0.20 D, respectively. Mean patient age was 66.45 years. Patients were examined preoperatively and 1 day, 1 week and 1 and 3 months postoperatively. Results: Three months postoperatively, mean astigmatism was 1.60 +/- 0.37 D in the superior incision group and 0.83 +/- 0.19 D in the temporal incision group. Induced astigmatism calculated by vector analysis was 1.44 +/- 0.31 D and 0.62 +/- 0.28 D, respectively. The temporal incision group had significantly lower astigmatism at all follow-ups (P = .000). Conclusion: Upper lid pressure on the superior corneal incisions led to fluctuating, against-the-rule astigmatism that was significantly higher than that induced by temporal incisions.