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Meixiao Shen, Zhe Xu, Mei Peng, Jun Jiang, Jianhua Wang, Fan Lv; Diagnostic value of entire vertical thickness profiles of epithelium and Bowman’s layer for sub-clinical keratoconus using ultra-high resolution optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1619.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the diagnostic value of vertical thickness profiles of epithelium and Bowman’s layer for sub-clinical keratoconus (KC) using ultra-high resolution optical coherence tomography (UHR-OCT).
Eighty-one eyes of 81 normal subjects, 20 eyes of sub-clinical KC and 53 eyes of 39 KC patients were enrolled. The vertical thickness profiles of epithelium and Bowman’s layer in each eye were measured using UHR-OCT. Eight diagnostic indices including ESD (epithelial standard deviation) and BSD (Bowman’s layer standard deviation), ESV (epithelial standard variation) and BSV (Bowman’s layer standard variation), EEI (epithelium ectasia index) and BEI(Bowman’s ectasia index), EEI-MAX(maximum epithelial ectasia index) and BEI-MAX((maximum Bowman’s ectasia index) were calculated to quantify the specific change pattern for each layer. Receiver operating characteristic (ROC) curves were used to determine the diagnostic accuracy (area under the curve, AUC) and to identify optimal cutoff points to maximize sensitivity and specificity in discriminating keratoconus and subclinical keratoconus from normal corneas.
Both minimum thicknesses of epithelium and Bowman’s layer were statistically thinner in KC (41.55 ± 6.42 µm for EL, 11.08 ± 2.84 µm for BL, both P< 0.005) and sub-clinical KC (49.47 ± 4.06 µm for EL, 15.44 ± 2.42 µm for BL, both P <0.05). ROC curve analyses showed high diagnostic accuracy of the indices (AUC ranged from 0.95 to 0.98, and 0.83 to 0.87, respectively)and Bowman’s layer (AUC ranged from 0.91 to 0.96, and 0.71 to 0.87, respectively) for both KC and subclinical KC. Among all investigated indices based on vertical thickness profiles of epithelium and Bowman’s layer, ESD provided the higher diagnostic accuracy to discriminate keratoconus (AUC 0.98 with sensitivity and specificity of 98% and 97%, respectively) and subclinical keratoconus (AUC 0.87 with sensitivity and specificity of 80% and 73%, respectively) from normal corneas.
UHR-OCT characterized the vertical thickness change patterns of epithelium and Bowman’s layer among normal, sub-clinical KC and KC eyes. The diagnostic index of ESD detected the sub-clinical KC and KC eyes with high accuracy and it might be useful to detect early or even sub-clinical KC.
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