Excimer laser photorefractive keratectomy(PRK) has been used as a good treatment modality for myopia. However many surgeon reported its complications, especially loss of best corrected visual acuity(BCVA) after PRK with an incidence of 0~12%. Thus we studied the causes and incidence of BCVA loss in myopic eyes that were followed up at least 12 months after PRK. We defined `BCVA loss` as 2 or more lines decrease by Snellen chart comparing to preoperative visual acuity. We found that 16 of 313 eyes(5.1%) lost BCVA during follow up period after PRK. High myopes, 8.25diopters or more, developed BCVA loss(8.8%) more commonly than myopes below 8.00 diopters(3.3%) (P<0.05). But BCVA loss recovered after post-operative 2 years except one eye. The causes of BCVA loss were corneal haze, irregular astigmatism, incidental cataract and steroid-induced glaucoma. According to the corneal haze scoring, average corneal haze was greater in eyes(1.47 score) with BCVA loss than eyes(0.36) without BCVA loss (P<0.01). However average cornea haze score in eyes with BCVA loss gradually decreased with time.As a result, main causes of BCVA loss after PRK was corneal haze, irregular astigmatism. High myopia more than 8.25 diopters showed greater BCVA loss than myopia less than 8.00diopters after PRK, but BCVA loss recovered with time.
Astigmatism ; Cataract ; Cornea ; Follow-Up Studies ; Glaucoma ; Incidence ; Lasers, Excimer* ; Myopia ; Photorefractive Keratectomy* ; Visual Acuity*

We examined 60 eyes of 60 patients after excimer photorefractive keratectomy(PRK) for myopia and analyzed the changes of central island on corneal topography for 6 months prospectively. These patients were divided into two groups according to the degree of myopia, group 1(26 eyes, 6 diopters or below by spherical equivalent) and group 2 (34 eyes, over 6 diopters). The occurrence rate of central island was 76.4% collectively, 87.5% in group 1, 67.7% in group 2 at 2 weeks after PRK. It decreased to 30.4%, 43.5%, and 21.1% respectively at 6 months after PRK and was lower in group 2 than group 1. However there was no statistically significant correlation between the reduction of central island size and improvement of corrected visual acuity in both groups. In conclusion, the central island disappeared and decreased the amount for six months follow-up period after PRK and seems to be no effect on the corrected visual acuity.
Corneal Topography ; Follow-Up Studies ; Humans ; Myopia* ; Photorefractive Keratectomy* ; Prospective Studies ; Visual Acuity*

FK506 is a relatively new immunosuppressant similar in action to cyclosporine A, but is potent about 100 times. Its primary action is against T lymphocyte, the major cellular component in corneal allograft rejetion. The purpose of this was to evaluate the ability of topical FK506 in prevention corneal xenograft rejection in an experimental animal model according to topical FK506 concentration. Cross-species xenotrasplants were used as the most vigorous stimulus to induce corneal rejection. Corneas derived from Hartley guinea pigs were transplanted into the right eyes of 24 male Sprague Dawley rats. Topical treatment was administerd by using FK506 0.3mg/ml, lmg/m, 3mg/ml in 8 cyclodextrin suspension or cyclodextrin suspension Only four times per day (10micrometer at one time). Treatments were started post-op 1 day and continued for 21 days. The grafts underwent 8 double-masked examination, and 8 score was given for opacity, edema, neovascularization, protrusion due to rejection. The animals were sacrificed 10 days and 21 days after transplantation and graft was stained with H & E, PAS. We examined the stained graft about inflammatory cells infiltration. Topical FK506-treated corneas was much clear than cyclodextrin-treated corneas less inflammatory cell infiltration after post-op 10 days (P<0. 05). There was no difference in different FK506 concentration. We conclude that topical FK506 may be effective in prolonging xenograft survival in rat keratoplasty model.
Allografts ; Animals ; Cornea ; Corneal Transplantation ; Cyclosporine ; Edema ; Guinea Pigs ; Heterografts* ; Humans ; Lymphocytes ; Male ; Models, Animal ; Rats ; Rats, Sprague-Dawley ; Tacrolimus* ; Transplants