نتايج و تغييرات شاخص هاي توپوگرافيك و حساسيت كنتراست پس از ليزيك به روش كراس سيلندر در آستيگمات مخلوط

Cross-cylinder Ablation LASIK for Mixed Astigmatism

Purpose: To evaluate visual and refractive results, topographic indices, and contrast sensitivity changes after Laser in situ keratomiluesis (LASIK) for mixed astigmatism using the cross-cylinder ablation method with the Technolas 217C excimer laser. Methods: In a before-after clinical trial, 15 eyes of 8 patients with mixed astigmatism were studied. Refraction and topographic indices including asphericity (Q value), predicted corneal acuity (PCA), and corneal uniformity index (CUI) were derived from Holladay diagnostic summary program (EyeSys 2000 Version) before and after surgery. Contrast sensitivities for spatial frequencies of 3, 6, 12, and 18 cycles per degree were measured using Vector Vision instrument (CSV 1000). Patients were assessed 1 and 3 months after surgery. Results: Before surgery, the range of astigmatism was -1.50 to -6.50 diopters (D) (mean -3.50±1.36 D) and the spherical component was between +0.25 and +3.50 D (mean +1.33±1.30 D). Mean cylinder and spherical refraction reduced from -3.50 and +1.33 D before surgery to -0.76 and +0.36 D after surgery, respectively. Three months after surgery, 11 eyes out of 15 (72.7%) had less than -1.00 D of astigmatism, all eyes had uncorrected visual acuity (UCVA) of 20130 or better and 53% of the eyes had an UCVA of 20120. We found a statistically significant reduction in contrast sensitivity at all mentioned spatial frequencies during the first month which recovered to preoperative values by 3 months after surgery. Asphericity decreased by an average of -0.15 ± 0.16 (P = 0.01). PCA and CUI were not changed after surgery. Conclusion: The cross-cylinder ablation method found to be effective for correction of mixed astigmatism while the cornea maintains its prolate shape and contrast sensitivity is preserved in all spatial frequencies between 1 and 3 months after surgery. Key words: LASIK, cross cylinder ablation, contrast sensitivity, corneal topography, mixed astigmatism Trans-Scleral Diode Laser Retinopexy in Rhegmatogenous Retinal Detachment Modareszadeh M, MD; Bahmani Kashkooli M, MD Purpose: To evaluate the results of trans-scleral diode laser retinopexy for induction of chorioretinal reaction in scleral buckling surgery. Methods: This before-after clinical trial was performed on 69 eyes of 66 patients with rhegmatogenous retinal detachment eligible for scleral buckling. Results: The retina was reattached with scleral buckling in 64 eyes (92.8%). In 4 eyes, the scleral buckling was performed twice (modified). In 5 eyes, significant PVR developed post-operatively (7.2%), two of which had pre-operative PVR grade B. In two eyes, retinal photocoagulation was performed through silicon implants and sclera. Best corrected visual acuity (Log MAR) was 1.22±1.5 preoperatively and 0.74±1.75 postoperatively (P<0.02). In 95% of the eyes with reattached retina (61 eyes), visual acuity improved or remained stable. In 12 eyes, rupture of Bruchʹs membrane associated with retinal break formation happended which did not affect retinal reattachment. No other complications were seen which could be ascribed to diode retinopexy. Conclusion: Trans-scleral diode laser photocoagulation for induction of chorioretinal reaction in scleral buckling is a safe and effective procedure. The ability to perform retinopexy through episcleral silicon implants is a definite advantage of this method over cryopexy.