Early diagnosis of forme fruste Keratoconus disease (FFK) is the first priority in the preoperative evaluations of RS refractive surgery.The aim of this study was to investigate the correlation between findings of Belin Ambrosio Enhanced Ectasia display (BAD) software and conventional corneal imaging (Orbscan and topography) in the early diagnosis of KCN (Keratoconus).

For doing this cross-sectional study, a total of 1000 eyes were selected from 500 patients that underwent the myopic PRK surgery (photorefractive keratectomy) and were compared in four study groups during the years 2014-2015. In group 1, all topography, Orbscan and BAD criteria were normal (65.8%).In contrast; at least one of the topography or orbscan criteria as well as at least one BAD criterion (12.6%) were abnormal in Group 2. In Group 3, Eyes that had normal Orbscan and topography criteria and but at least one abnormal BAD criterion (18.5%). Also Patients that had least one abnormal Orbscan or topography criterion, but all BAD criteria (3.1%) were normal in Group 4. Thickness of the thinnest point (TP) of cornea was compared in Pentacam and topography. Data analysis was done by SPSS software (version 21). P value < 0.05 was considered statistically significant.

BAD criteria were normal in 78.5% of all eyes with normal topography and Orbscan criteria (157 eyes). BAD criteria were also abnormal in 80.2% of eyes. "Dt" was the only criterion that had significant correlation with thinnest point (TP) in the orbscan in four studied groups. There was also no significant difference between TP in Orbscan and Pentacam.

BAD criteria had a relatively acceptable sensitivity (80%) and specificity (78%), compared with conventional Orbscan and topography criteria. Thus, BAD criteria can be more effective in the diagnosis of FFK.