Since the nineteenth century, conjunctival flaps have been used as a conventional treatment to resistant corneal disease such as herpetic ulcers, recurrent erosions, bullous keratopathy, marginal ulcers, painful blind eyes and filamentary keratitis (Gundersen, 1958). In 1960, Gundersen described a new technique, now called the Gundersen or bucket-handle flap, which provided a permanent option with increased efficacy for treatment resistant corneal disease (Gundersen, 1960).
The G-G haplotype had an extremely high association with PEX (odds ratio of 27.7) in the patient population. Therefore, the G-G haplotype is associated with a high risk of having PEX. Furthermore, 29/32 children of the PEX patients could be categorized based on the presence or absence of the inherited G-G haplotype (predicting high risk of having PEX) with a diagnostic yield of 91%.