The use of Bowman's layer vertical topographic thickness map in the diagnosis of keratoconus.
OBJECTIVE
To evaluate the use of Bowman's layer (BL) vertical topographic thickness maps in diagnosing keratoconus (KC).


METHODS
Prospective, case control, interventional case series.


METHODS
A total of 42 eyes: 22 eyes of 15 normal subjects and 20 eyes of 15 patients with KC.


METHODS
Bowman's layer 2-dimensional 9-mm vertical topographic thickness maps were created using custom-made ultra high-resolution optical coherence tomography.


METHODS
Bowman's layer average and minimum thicknesses of the inferior half of the cornea, Bowman's ectasia index (BEI; defined as BL minimum thickness of the inferior half of the cornea divided by BL average thickness of the superior half of the cornea multiplied by 100), BEI-Max (defined as BL minimum thickness of the inferior half of the cornea divided by BL maximum thickness of the superior half of the cornea multiplied by 100), keratometric astigmatism (Ast-K) of patients with KC, and average keratometric (Avg-K) readings.


RESULTS
In patients with KC, BL vertical thickness maps disclosed localized relative inferior thinning of the BL. Inferior BL average thickness (normal = 15±2, KC = 12±3 μm), inferior BL minimum thickness (normal = 13±2, KC = 7±3 μm), BEI (normal = 91±7, KC = 48±14), and BEI-Max (normal = 75±8; KC = 40±13) all showed highly significant differences in KC compared with normal subjects (P< 0.001). Receiver operating characteristic (ROC) curve analysis showed excellent predictive accuracy for BEI and BEI-Max with 100% sensitivity and specificity (area under the curve [AUC] of 1) with cutoff values of 80 and 60, respectively. The AUC of inferior BL average thickness and minimum thickness were 0.87 and 0.96 with a sensitivity of 80% and 93%, respectively, and a specificity of 93% and 93%, respectively. Inferior BL average thickness, inferior BL minimum thickness, BEI, and BEI-Max correlated highly to Ast-K (R = -0.72, -0.82, -0.84, and -0.82, respectively; P< 0.001) and to Avg-K (R = -0.62, P< 0.001; R = -0.59, P = 0.001; R = -0.60, P< 0.001; and R = -0.59, P = 0.001, respectively).


CONCLUSIONS
Bowman's layer vertical topographic thickness maps of patients with KC disclose characteristic localized relative inferior thinning. Inferior BL average thickness, inferior BL minimum thickness, BEI, and BEI-Max are qualitative and quantitative indices for the diagnosis of KC that accurately correlate with the severity of KC. In our pilot study, BEI and BEI-Max showed excellent accuracy, sensitivity, and specificity in the diagnosis of KC.
Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida; Saint Louis University Eye Institute, Saint Louis University, St. Louis, Missouri; Department of Ophthalmology, Faculty of Medicine, University of Alexandria, Alexandria, Egypt.
Mohamed
M
Abou Shousha
Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida.
Victor L
VL
Perez
Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida.
Ana Paula
AP
Fraga Santini Canto
Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida.
Pravin K
PK
Vaddavalli
Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida.
Fouad E
FE
Sayyad
Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida.
Florence
F
Cabot
Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida.
William J
WJ
Feuer
Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida.
Jianhua
J
Wang
Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida. Electronic address: syoo@med.miami.edu.
Sonia H
SH
Yoo
D000328:Adult; D019540:Area Under Curve; D050541:Bowman Membrane / Q000473:pathology*; D016022:Case-Control Studies; D019781:Corneal Topography; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis*; D008297:Male; D009929:Organ Size; D010865:Pilot Projects; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D041623:Tomography, Optical Coherence