Evaluation of optic nerve head using a newly developed stereo retinal imaging technique by glaucoma specialist and non-expert-certified orthoptist.

Purpose

To evaluate the reproducibility and interexaminer consistency in analyzing the optic disc parameters using a newly fundus stereoscopic camera, and their correlation with parameters of the Heidelberg Retina Tomograph II (HRT II) was also examined.

Methods

This study examined 53 eyes of 53 healthy volunteers (mean age, 21.8 y). Fifty-five eyes of 55 glaucoma patients (mean age, 59.3 y) were also involved. A Nonmyd WX retinal camera was used for stereoscopic fundus imaging. The diagnostic parameters for the optic nerve head analyses were examined under the following conditions: (1) the intraexaminer reproducibility was determined by a certified orthoptist (CO) with 1 year's experience, with the appropriate coefficient of variation in 8 healthy eyes; and (2) the interexaminer consistency of the diagnostic parameters by both glaucoma specialist and CO was examined in 45 healthy eyes and 55 glaucomatous eyes. By subgroup analysis, the healthy eyes were classified into 2 groups based on the degree of myopia, the optic disc of glaucomatous eye was classified into 4 types: focal ischemic, generalized enlargement, myopic, and senile sclerotic, and also classified into 3 stages (early, moderate, and severe) by Hodapp-Anderson-Parrish scale. (3) The correlation of parameters common to Nonmyd WX and HRT II was examined in 18 eyes of randomly selected patients.

Results

The results were as follows: (1) Mean coefficient of variation of 2.6% to 17.6%, with volume parameters considerably lower than the other parameters. (2) In both groups, a high or moderate degree of consistency was obtained (r=0.40 to 0.99; P=0.032 to <0.0001), except only the upper rim width in healthy subjects (r=0.28; P=0.137). In particular, good consistency was obtained in healthy eye with >-3 D of myopia, in glaucoma patients with the generalized type of optic disc and severe glaucomatous stage. (3) A strong correlation with HRT II was obtained only in the cup area and the disc area by both specialist and CO (r=0.75 to 0.90; P=0.0003 to <0.0001).

Conclusions

Our studies indicated that most of the parameters were highly reproducible and consistent, and less difference was found between the results obtained by an experienced glaucoma specialist and a non-expert CO in patients with deep cupping and severe eye, but the examiner needs a clear understanding of the criteria for the rim and the cup.