Alterations in blood-aqueous barrier after corneal refractive surgery.
Author(s): Vita RC, Campos M, Belfort R Jr, Paiva ER
Affiliation(s): Department of Ophthalmology, Paulista School of Medicine, Federal University of Sao Paulo, Brazil.
Publication date & source: 1998-03, Cornea., 17(2):158-62.
Publication type: Clinical Trial; Comparative Study ; Randomized Controlled Trial
PURPOSE: To assess alterations in the blood-aqueous barrier after radial keratotomy (RK), photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), and phototherapeutic keratectomy (PTK). METHODS: Aqueous flare was evaluated using the Kowa FM 500 laser flare meter in a total of 87 eyes from 82 patients who underwent refractive surgery. Measurements were obtained preoperatively in 51 eyes of 51 patients who underwent RK or PRK and again at the end of surgery, and at 1 day and 1 week postoperatively. These patients had been randomized (double masked) to receive topical 0.1% dexamethasone, polymyxin B (6,000 U/ml), and 0.5% neomycin 4 times a day for 1 week after surgery, or polymyxin B (6,000 U/ml) and 0.5% neomycin for 1 week. Aqueous flare measurements were also obtained before surgery in 36 eyes (31 patients) that underwent LASIK and again at 1 day and 1 and 2 weeks postoperatively. All patients in this group received topical 0.1% dexamethasone, polymyxin B (6,000 U/ml), and 0.5% Neomycin 4 times a day for 15 days after surgery. RESULTS: Uneventful RK induced a significant increase in flare immediately after surgery, although this did return to baseline 1 day after surgery (Friedman test). Measurements at 7 days after surgery were similar in steroid-treated and untreated groups. Limbal bleeding, which occurred in 23% (12/51) eyes, did not induce significantly increased flare as compared to uneventful RK. Microperforations, which occurred in 18% (9/51) eyes, did induce significant alterations in the blood-aqueous barrier that persisted for >1 day, but measurements returned to preoperative levels by day 7. PRK and LASIK induced substantially increased flare in some eyes. Phototherapeutic keratectomy, in particular, induced an elevation in flare measurements that did not return to normal levels even by 15 days after surgery (Friedman test). CONCLUSIONS: Using mean results of laser flare meter evaluation, uneventful RK appears to induce short-lasting elevations in aqueous flare in both steroid-treated and untreated patients. Microperforation induced prominent alterations in flare measurements, although limbal bleeding did not. Both PRK and LASIK did appear to increase flare measurements in some eyes, while PTK induced significant elevations in aqueous flare in the majority of eyes.