Healio
Healio
February 19, 2014
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Bowman's thickness maps found to help diagnose keratoconus

Measurements taken from custom Bowman's layer vertical topographic thickness maps demonstrated accuracy, sensitivity and specificity in diagnosing patients with keratoconus, according to a new study in Ophthalmology.

Abou Shousha and colleagues evaluated 42 eyes, including 20 eyes from 15 patients with keratoconus and 22 eyes from 15 patients without the disease.

Researchers created Bowman's layer 2-dimensional 9-mm vertical topographic thickness maps with which to measure the patients. They collected average and minimum thicknesses of the inferior half of the cornea; Bowman’s ectasia index (BEI), BEI-Max, keratometric astigmatism in patients with keratoconus and average keratometric readings.

BEI is defined in the study as Bowman’s layer minimum thickness of the inferior half of the cornea divided by Bowman’s layer average thickness of the superior half of the cornea, multiplied by 100. BEI-Max is defined as Bowman’s layer minimum thickness of the inferior half of the cornea divided by Bowman’s layer maximum thickness of the superior half of the cornea, multiplied by 100.

Results showed that patients with keratoconus displayed inferior Bowman’s layer average thickness, inferior Bowman’s layer minimum thickness, BEI and BEI-Max in comparison to participants without the disease.

"Our pilot study has shown for the first time in the literature the in vivo relative localized inferior thinning of Bowman’s layer in keratoconus as measured on a 2-D 9-mm vertical topographic thickness map of the layer," the authors concluded. "Diagnostic indices measured on Bowman’s layer maps, namely, the inferior Bowman’s layer average thickness, inferior Bowman’s layer minimum thickness, BEI and BEI-Max, have been shown to be valuable qualitative and quantitative diagnostic indices for the diagnosis of keratoconus. The BEI and BEI-Max showed excellent accuracy in differentiating keratoconus from normal subjects with 100% sensitivity and specificity in our case series. Moreover, BEI and BEI-Max have been shown to be valuable quantitative indices that accurately correlate with the severity of keratoconus."

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Source:

Ophthalmology. 2014;doi: 10.1016/j.ophtha.2013.11.034.