Peripheral hypertrophic subepithelial corneal degeneration: characterization, treatment and association with human leucocyte antigen genes

Abstract

To evaluate the efficacy of keratectomy in treating irregular astigmatism caused by peripheral hypertrophic subepithelial corneal degeneration (PHSD) and to study the possible underlying immunological risk factors. Patients (14 eyes) with diagnosed PHSD were treated with superficial keratectomy with or without the assistance of phototherapeutic keratectomy (VisX S4; VisX Inc., Santa Ana, CA, USA). Thirteen patients were subjected to analysis of human leucocyte antigen (HLA) genes, complement C4 gene numbers and total plasma immunoglobulin levels. Immunological risk factors between patients and a control group comprising 150 individuals were compared. The mean preoperative best spectacle corrected visual acuity (BCVA) improved from 0.16 ± 0.22 (LogMAR scale range 0-0.7) to 0.06 ± 0.13 (-0.1-0.4) (p < 0.01). The mean preoperative astigmatism decreased significantly from 3.8 ± 2.1 D (range 1.2-8.2) to 2.1 ± 1.4 (range 0.6-5.0, p = 0.02) based on corneal topography. The HLA-B*44 allele and the ancestral haplotype (AH) 8.1 were found significantly more often in PHSD patients than in controls (both p = 0.03). No differences in the C4 genes were found. Astigmatism secondary to PHSD can be effectively treated with keratectomy. Peeling of the fibrotic tissue reduced astigmatism and improved visual performance. We suggest that HLA-B*44 allele and AH 8.1 haplotype are immunological factors predisposing to the development of PHSD. The consequent disruption/alteration of the limbal barrier may lead to corneal peripheral fibrous formation inducing astigmatism.