Structure-function relationship and diagnostic value of RNFL Area Index compared with circumpapillary RNFL thickness by spectral-domain OCT.

PURPOSE: The purpose of the study was to evaluate the structure-function relationship and diagnostic value of retinal nerve fiber layer (RNFL) Area Index from the RNFL thickness deviation map of Cirrus SD-OCT.

METHODS: : A total of 84 normal control eyes, 88 preperimetric eyes, and 146 perimetric glaucoma eyes were analyzed. The area of the RNFL defect in the RNFL thickness deviation map was expressed as RNFL Area Index: 1-[area of superpixels coded in red/(6×6-optic disc area)]. The diagnostic performance of RNFL Area Index and that of circumpapillary RNFL thickness were compared with the area under the receiver operating characteristic curve. Regression analysis was performed with the OCT measurements and the mean retinal sensitivity of the corresponding fields.

RESULTS: : The RNFL Area Index was 96.63±14.22%, 89.89±14.54%, and 81.65±17.11% in the control, preperimetric, and perimetric glaucoma group. The RNFL Area Index had the largest area under the receiver operating characteristic curve to discriminate preperimetric and perimetric glaucoma from normal eyes. The RNFL Area Index showed a strong correlation with circumpapillary RNFL thicknesses in perimetric glaucoma, however, only modest correlation was shown in preperimetric glaucoma. In preperimetric glaucoma, the RNFL Area Index had the strongest associations with mean retinal sensitivity and it was significantly different from those of circumpapillary RNFL thicknesses.

CONCLUSIONS: : The RNFL Area Index showed better diagnostic performance for glaucoma detection and stronger structure-function relationships in preperimetric glaucoma. The RNFL thickness deviation map of Cirrus SD-OCT may be useful to correlate with functional loss in early glaucomatous eyes.