[Clinical analysis on the effects of laser-assisted subepithelial keratomileusis in treatment of super high myopia].

OBJECTIVE: To assess the clinical efficacy and safety of LASEK in the treatment of super high myopia. METHODS: It was a retrospective case series study. Fifty-six eyes of 33 cases with super high myopia were treated with LASEK. Mean spherical equivalent preoperative was (-11.70 +/- 1.59) D (range from -10.0 D to -15.13 D), mean ablation zone was (5.3 +/- 0.51) mm (range from 4.3 mm to 6.0 mm), mean ablation depth was (146.1 +/- 29.3) microm. The mean time of alcohol used treatment was (29.2 +/- 2.8) seconds. Postoperative follow-up assessments were performed at 1, 3, 6 and 12 months after surgery. Postoperative measurements included slit-lamp microscopy, manifest refraction, un-corrected visual acuity (UCVA), best corrected visual acuity (BCVA), intraocular pressure and haze, etc. The time of follow-up was more than one year. The results were analyzed with ANOVA by SPSS software. RESULTS: Fifty percent of eyes obtained UCVA of > or = 1.0, and 78.6% of eyes obtained UCVA > or = 0.6, at six months after operation. Forty-one percent eyes obtained UCVA of > or = 1.0, and 73.2% eyes obtained UCVA > or = 0.6 at one year postoperatively. The mean UCVA in Snellen chart was 0.85 +/- 0.20, 0.88 +/- 0.28, 0.84 +/- 0.26 and 0.83 +/- 0.28 at 1, 3, 6 and 12 months after operation, respectively. These data were transformed into lgMAR visual acuity and analyzed statistically. There was no significant statistically difference between UCVA at different follow-up periods (F = 0.749, P = 0.518). The postoperative UCVA compared to preoperative BCVA being the same/or improved in 71.4% eyes and decreased in 28.6% eyes at six months after operation; and was 64.3%, and 35.7% at one year after operation, respectively. The effective index was 0.994 and 0.992 at six and twelve months after operation, respectively. The postoperative BCVA compared to preoperative being the same (or improved) and decreased at six and twelve months after operation was 85.3% vs. 14.7%, and 84.8% vs. 15.2%, respectively. The mean BCVA in Snellen chart was 0.90 +/- 0.17, 0.94 +/- 0.24, 0.95 +/- 0.16 and 0.96 +/- 0.16 at 1, 3, 6 and 12 months after operation, respectively. These data were transformed into lgMAR visual acuity and analyzed statistically. There was no significant statistically difference between lgMAR BCVA at difference different follow-up periods (F = 1.567, P = 0.229). The safe index at 6 and 12 months were 1.009 and 1.010. The incidence of refraction regression at 3, 6 and 12 months after operation was 19.6%, 28.6% and 30.3%, respectively. Mean regressive diopter in regressed eyes at 3, 6 and 12 months after operation was (-1.20 +/- 1.08) D, (-1.23 +/- 0.75) D, (-1.49 +/- 1.04) D, respectively. Haze grade 0.5 was 21.4% at 3 months after operation; grade 0.5 and 1 were 8.9% and 5.4% at 6 months after operation, respectively, at 6 months after operation. Haze grade 0.5 was 12.5% at one year after operation. The incidence of high intraocular pressure induced by topical use of corticosteroid eye drop was 8.9%. CONCLUSIONS: LASEK is a safe and effective procedure for correction of super high myopia, though there is still some regression happened after operation and the intraocular pressure should be observed during the follow-up periods.

[Intraocular lens power calculations in eyes with previous corneal refractive surgery].

Results of intraocular lens power calculation were lower than actual required power in eyes with previous corneal refractive surgery because the inaccurate readings of corneal power obtained from standard keratometry. This causes the unacceptable hyperopia after cataract surgery. With increasing of population undergone excimer laser refractive surgery, this problem will be an obvious problem in years or decades. Several methods have been proposed to increase the accuracy of intraocular lens power calculation for cataract surgery in eyes undergone refractive surgery and are reviewed in this article.

[Observation on healing process of corneal lens after epikeratophakia with confocal microscopy].

OBJECTIVE: To investigate the nerve and cell healing process of cryopreservation tissue lens after epikeratophakia by in vivo confocal microscopy. METHOD: Epithelia, stroma and nerves of tissue lens, interface between lens and recipient and stroma and endothelia of recipient were observed by in vivo confocal microscopy and recorded by video in 24 cases of keratoconus from 3 days to 5 years after epikeratophakia. RESULTS: Epithelial layer of lens: The tissue lens was covered by corneal superficial flat cells with wing cells and basal cells on the periphery at 3 - 4 days postoperatively, but the morphology and arrangement of these cells were irregular with low density. Superficial flat cells took shape completely at one month, and the morphology and density of the basal cells tended to be normal at 6 months postoperatively. Subepithelial nerve plexus were scattered at 18 months and their normalization completed at 2 years postoperatively. Stroma of lens: Keratocytes appeared circular, dot-shaped, rod-shaped or reticular in morphology postoperatively. Normal keratocytes were discovered sporadically on the periphery of the lens at 2 years postoperatively. At 5 years postoperatively the density of keratocytes was lower than normal stromal keratocyte in the center of the lens. Stromal nerves of lens: Nerves could grow into tissue lens at 6 months postoperatively, the quantity of nerves increased at 2 years and was still less than normal quantity at 5 years postoperatively. Stroma and endothelia of recipient: There was no change in the stroma and endothelia of recipient. CONCLUSIONS: There is significant difference among healing process of epithelia, nerves of unvital tissue lens after epikeratophakia, but there is little change in the transparency of tissue lens.

[Experimental and clinical studies on photo-therapeutic keratectomy for superficial corneal diseases].

OBJECTIVE: To study the histologic changes in rabbit corneas after photo-therapeutic keratectomy (PTK), define the indications and treatment parameters and evaluate efficacy of PTK. METHODS: (1) The model of superficial corneal scar in rabbit was made by burn with 8.17% sulfuric acid, and then treated with PTK in two weeks. The corneas were examined with confocal microscope in vivo, nerve staining, light and transmission electron microscope during period after PTK to study the histopathologic changes. (2) Thirty eyes with superficial corneal diseases including 12 eyes with corneal dystrophy, 2 eyes with band degeneration, 10 eyes with scar after infection and trauma and 6 eyes with Dimmer nummular keratitis were treated with PTK. The method of treatment was varied with different diseases. Follow-up was more than six months. To investigate the change of haze, visual acuity, refraction and keratometric power during period after PTK, chi-square tests were used. RESULTS: (1) Experimental group: in the ablative zone at early time after PTK, there were infiltration of polymorphonuclear leukocytes accompanied by macrophages, proliferation of fibroblast and loose nascent collagen in disorder in the anterior stroma. The wound healing process was stable at six months after PTK. (2) Clinical group: compared with the preoperative visual acuity, the best corrected visual acuity was improved in 21 eyes (70.0%), unchanged in 5 eyes (16.7%) and decreased in 4 eyes (13.3%) at six months after PTK, and the results were better for corneal dystrophy and band degeneration. Haze grade 0.5 was in five eyes, grade I in two eyes and grade 0 the rest. The mean hyperopic shift was + 1.52 D. CONCLUSIONS: The wound healing process in rabbit cornea stabilizes at six months after PTK. PTK is a simple, safe, effective treatment for superficial corneal diseases. The indications for PTK are corneal pathology in the anterior one-third of the cornea, especially corneal dystrophy and band degeneration.