Diffuse lamellar keratitis: incidence, associations, outcomes, and a new classification system.

PURPOSE: To evaluate the incidence, associations, and visual outcomes in patients with diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK).

SETTING: University-based refractive surgery center, Boston, Massachusetts, USA.

METHODS: This retrospective review comprised 2711 eyes that had LASIK between September 1996 and September 1999. All eyes that developed DLK after LASIK were included. They were divided into type I DLK (center sparing) or type II DLK (center involved) and then subdivided into A (sporadic-DLK not diagnosed in other patients treated on the same day) or B (cluster-other patients identified with DLK). Type IA corresponded to center sparing, sporadic; type IB, center sparing, cluster; type IIA, center involved, sporadic; and type IIB, center involved, cluster. The main outcome measures were incidence of DLK after LASIK, time to diagnosis, time to resolution, and changes in best spectacle-corrected visual acuity (BSCVA). Unpaired t tests were used for statistical analyses.

RESULTS: Thirty-six eyes (1.3%) developed DLK. Type I occurred in 58.3% of cases (type IA, n = 18; type IB, n = 3) and type II, in 41.7% (type IIA, n = 10; type IIB, n = 5). The mean time to diagnosis was not statistically significantly different between type I (1.8 days) and type II (1.1 days). Fourteen eyes (38.9%) developed DLK after an epithelial defect, representing an odds ratio of 13 times. The association with an epithelial defect was statistically significantly greater with type I (11/21 eyes, 52.4%) than with type II (3/15 eyes, 20.0%; P =.05). The mean time to resolution was 3.5 days in type I (type IA = 3.6 days; type IB = 2.7 days). This was significantly shorter than in type II, which had a mean time to resolution of 12.1 days (type IIA = 9.3 days; type IIB = 10.2 days) (P =.001). Loss of 2 or more lines of BSCVA occurred in 2 of 5 patients with type IIB and in no patients with types IA, IB, or IIA.

CONCLUSIONS: Epithelial defects after LASIK increased the risk of DLK occurrence, especially type I. Type II DLK was associated with a prolonged time to resolution and carried a significantly higher risk of BSCVA loss than type I.