1/32. Topography-controlled excimer laser photorefractive keratectomy.PURPOSE: To assess whether photorefractive keratectomy (PRK) controlled by videokeratography can successfully treat refractive errors in eyes with corneal irregularities and improve spectacle-corrected visual acuity. methods: In a prospective clinical study, PRK was performed in 10 eyes of 10 patients. Reason for surgery was irregular astigmatism after penetrating keratoplasty, corneal irregularity after corneal scarring, corneal astigmatism in keratoconus, and decentration after myopic and hyperopic PRK. Excimer ablation was controlled by preoperative videokeratography (Orbscan II, Orbtek) using the MEL-70 system from Aesculap Meditec. Follow-up was 6 months. RESULTS: Concerning manifest refraction, the sphere was reduced on average from 1.92 to 0.57 D, 6 months postoperatively. Cylinder changed from -1.95 D on average to -0.30 D at 6 months postoperatively. There was improvement of uncorrected visual acuity of 2 or more lines in 5 eyes and no change in 5 eyes 6 months postoperatively. Spectacle-corrected visual acuity improved in 2 eyes by 2 to 3 lines, in 9 eyes by 1 to 3 lines, and showed no change in 1 eye. CONCLUSION: Videokeratography-controlled PRK improved refractive errors in irregular corneas with improvement of spectacle-corrected visual acuity.- - - - - - - - - - ranking = 1keywords = refractive error, error (Clic here for more details about this article) |
2/32. Confocal microscopy of a patient with irregular astigmatism after LASIK reoperations and relaxation incisions.PURPOSE: Laser-assisted in situ keratomileusis (LASIK) is widely used for correcting refractive errors. If the predicted refractive result is not achieved after the first operation, a re-operation can be performed by ablating more stromal tissue after reopening the flap. The goal of this study was to analyze, by using in vivo confocal microscopy, the morphologic changes associated with repeated LASIKs. methods: Clinical examination, computed corneal topography, and real-time in vivo confocal microscopy were performed on both eyes of a 50-year-old patient with induced irregular astigmatism leading to decreased best-corrected vision in the left eye after LASIK. The left cornea had been operated on 5 times (LASIK with two reoperations followed by two relaxing incisions), and the right cornea twice (LASIK with one reoperation). RESULTS: Microfolds at the level of the Bowman's layer and highly reflective particles at the flap interface were observed in both corneas. The subbasal nerve plexus was severed in the left eye. In addition, we identified epithelial material in the flap margin and inside one of the two relaxing incisions placed inferotemporally. CONCLUSION: Repeated LASIKs may stretch the flap and result in microfolding at the Bowman's layer. This and deposition of particles in the flap interface may increase with the number of reoperations, challenging the healing response. Microfolding and occurrence of foreign material in the interface may add to the irregular astigmatism and poor visual outcome after LASIK. Clinical in vivo confocal microscopy offers new possibilities for the assessment of ultrastructural changes after corneal refractive surgery.- - - - - - - - - - ranking = 0.5keywords = refractive error, error (Clic here for more details about this article) |
3/32. A mathematical model for laser in situ keratomileusis and photorefractive keratectomy.PURPOSE: The purpose of ablation refractive surgery is to remove the refractive error from the inherently asymmetric aspheric cornea. Although the technique is gaining wide acceptance and popularity, some patients are left with irregular corneas. Our objective was to develop a methodology to analyze corneal shape, reduce the shape to arcs, modify the local arc value to the desired new arc value, and render a new continuous Euclidean surface without discontinuity. methods: The method to reconstruct the corneal surface consists of importing scanner output elevation data points into a computer-aided design (CAD) application to form the surface model. The corneal arc measurements are derived at 5 degrees increments and centered about the Gauss point of symmetry. Each arc is manipulated to adjust the corresponding arc on the proposed corneal surface to reflect the new arc value, correcting for the refractive error. The method determines the amount of corneal tilt and ablation depth at a given diameter required for the refractive error with a smooth transition zone to the base cornea. RESULTS: The case example is a patient who began with a spherical refraction of -8.75 D and after LASIK was emmetropic, but had irregular astigmatism and 20/30 best spectacle-corrected Snellen visual acuity. The proposed mathematical model compares the achieved surface shape to the mathematically planned surface contour. An enhancement procedure to remove the LASIK-induced corneal irregularity was designed. CONCLUSION: A mathematical technique to plan myopic ablative surgery to make the corneal surface regular and symmetric is proposed.- - - - - - - - - - ranking = 1.5keywords = refractive error, error (Clic here for more details about this article) |
4/32. Primary multipoint (segmental) custom ablation.PURPOSE: We present our experience in resolving visual symptoms in refractive patients undergoing primary multipoint (segmental) custom ablation. methods: Twelve eyes with mixed myopic astigmatism underwent evaluation and primary treatment by multipoint (segmental) custom ablation for the correction of refractive errors and visual symptoms using the Nidek NAVEX platform. RESULTS: Twelve eyes showed resolution of visual symptoms following diagnosis and treatment with MCA using the NAVEX platform. No patient lost two or more lines of best spectacle-corrected visual acuity. The postoperative root mean square of higher order aberrations did not change in a predictable or reproducible fashion. CONCLUSION: Multipoint (segmental) custom ablation with the Nidek NAVEX system was safe and effective for correcting mixed myopic astigmatism and for resolving visual symptoms in selected refractive surgery candidates. Small changes in the root mean square of higher order aberration values were not always reflected in a patient's subjective assessment of vision quality.- - - - - - - - - - ranking = 0.5keywords = refractive error, error (Clic here for more details about this article) |
5/32. Laser in situ keratomileusis for astigmatism greater than -3.50 D with the Nidek EC-5000 excimer laser.PURPOSE: LASIK with the Nidek EC-5000 excimer laser was used to treat high astigmatism. methods: The Nidek EC-5000 excimer laser and ACS microkeratome were used in regular LASIK procedures. Results of 74 eyes with astigmatism of more than 3.50 D and up to 10.00 D were evaluated. RESULTS: With Nidek algorithms, it was possible to eliminate refractive error completely or reduce it to a satisfactory amount, especially in difficult cases of mixed astigmatism with high astigmatic components. CONCLUSION: The Nidek software for mixed and high astigmatism was efficient, predictable, and produced good results in difficult cases of high astigmatism.- - - - - - - - - - ranking = 0.5keywords = refractive error, error (Clic here for more details about this article) |
6/32. Bilateral marginal sterile infiltrates and diffuse lamellar keratitis after laser in situ keratomileusis.PURPOSE: To report cases of acute bilateral catarrhal infiltrates in the early postoperative period after laser in situ keratomileusis (LASIK). methods: Retrospective review of both eyes of two patients. RESULTS: Two patients developed acute bilateral, marginal, catarrhal infiltrates in the early postoperative period after LASIK. Both patients had moderate to severe chronic meibomian gland dysfunction preoperatively. One patient (both eyes) developed grade 3 diffuse lamellar keratitis (DLK) that required both flaps to be lifted for irrigation and cleaning on postoperative day 5. Fungal and bacterial cultures were negative in both eyes of both patients. The condition resolved with intensive topical corticosteroids and fortified antibiotics. Regression of refractive error and the need for enhancement was encountered in all eyes. There was mild recurrence in one eye of each patient with pretreatment with topical corticosteroids prior to enhancement. CONCLUSIONS: Endogenous factors such as chronic blepharitis and meibomian gland dysfunction may trigger inflammation resulting in sporadic cases of catarrhal infiltrates after LASIK. These patients may have chronic inflammatory milieus that can trigger sporadic cases of catarrhal infiltrates after LASIK, with accompanying diffuse lamellar keratitis.- - - - - - - - - - ranking = 0.5keywords = refractive error, error (Clic here for more details about this article) |
7/32. Laser in situ keratomileusis as treatment for anisometropia after scleral buckling surgery.scleral buckling is an excellent procedure for retinal reattachment but can induce disabling refractive errors. Laser in situ keratomileusis (LASIK) has been proven effective for the reduction of refractive errors induced by ophthalmic surgery. We describe the case of a 53-year-old man who developed symptomatic anisometropia after placement of a scleral buckle for repair of a rhegmatogenous retinal detachment (RD). After the scleral buckling procedure, he retained excellent best corrected visual acuity but could not tolerate spectacle or contact lens correction. Thirty-four months after the scleral buckling procedure, LASIK was performed to correct myopic astigmatism with excellent refractive and functional results. This case demonstrates that LASIK may be safe and effective for the correction of refractive errors induced by RD repair.- - - - - - - - - - ranking = 1.5keywords = refractive error, error (Clic here for more details about this article) |
8/32. LASIK after epikeratophakia.PURPOSE: To present a case of successful laser in situ keratomileusis (LASIK) performed on a patient with residual hyperopic astigmatism and symptomatic anisometropia after previous epikeratoplasty (epikeratophakia). methods: LASIK was used successfully to treat hyperopic astigmatism after regression of epikeratophakia performed 16 years earlier. RESULTS: visual acuity improved to 20/30 without correction, and best-corrected visual acuity was 20/25 at the 3-month postoperative visit.CONCLUSIONS: LASIK can be used successfully as an alternative treatment to correct residual refractive error after epikeratoplasty.- - - - - - - - - - ranking = 0.5keywords = refractive error, error (Clic here for more details about this article) |
9/32. Wavefront-guided treatment of abnormal eyes using the LADARVision platform.PURPOSE: To evaluate the clinical results of Alcon LADARVision4000 wavefront-guided customized treatment of eyes with myopia and/or astigmatism, and clinically significant visual symptoms related to the presence of higher order aberrations. methods: Seven consecutive abnormal eyes from seven patients underwent wavefront-guided CustomCornea (1 PRK, 6 enhancements after previous LASIK) to correct low and higher order aberrations, using the Alcon LADARVision4000 platform. Eyes were examined at 1 to 3 months after treatment; the longest follow-up examination was used for analysis. Uncorrected and best spectacle-corrected visual acuity, manifest refractive spherical equivalent error, and subjective visual symptoms were measured, as well as wavefront measurement of higher order aberrations. RESULTS: All seven eyes had an improvement in UCVA. One eye gained 2 lines of BSCVA, four eyes gained 1 line, and no eye lost any lines. Manifest refractive spherical equivalent error was slightly hyperopic in all eyes ( 0.12 to 1.50 D). All eyes showed a reduction in pre-existing higher order aberrations, ranging between 1% and 48%. Spherical aberration was reduced most (mean 38% reduction), coma was reduced by a mean 14%, and all other terms were reduced by a mean 17% compared to preoperative values. Subjectively, all patients noticed a reduction in their pre-existing visual symptoms and reported visual performance comparable to their fellow asymptomatic eye. overall, the treatment was considered very satisfactory by patients in terms of visual quality gain. CONCLUSION: Wavefront-guided custom ablation with Alcon's LADARVision4000 was effective in reducing higher order aberrations and related visual symptoms in this preliminary small series. Longer follow-up on more eyes is necessary to assess the accuracy of the algorithm in the correction of defocus, which resulted in a slight overcorrection in this study.- - - - - - - - - - ranking = 0.00096640466209546keywords = error (Clic here for more details about this article) |
10/32. Complete bilateral vitreous detachment after LASIK retreatment.We describe a case of a 47-year-old woman who underwent bilateral laser in situ keratomileusis (LASIK) for the correction of myopia and astigmatism. Two months later a residual refractive error was present in both eyes. LASIK retreatment was decided and performed the following day. Twenty-four hours after the procedure, the patient reported myodesopsia in both eyes. Funduscopic examination revealed a complete bilateral posterior vitreous detachment confirmed by kinetic ultrasound. Visual disturbance in both eyes continued to be present after 10 months of follow-up. Sudden changes in intraocular pressure related to suction ring use might be the cause of posterior vitreous detachment in this patient.- - - - - - - - - - ranking = 0.5keywords = refractive error, error (Clic here for more details about this article) |
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