Evaluation Of Cup-To-Disc Ratios Using 3-Dimensional Fundus Photography.

Background: The evaluation of cup-to-disc ratios can be a daunting task for the novice
optometry student. As most experienced optometrists know, perceiving the optic nerve head stereoscopically requires practice and skill which takes time to acquire. When first performing this evaluation, students often rely on color changes of the nerve head in order to evaluate cup-to-disc ratios. However, relying solely on coloration of the optic nerve head to evaluate cup-to-disc ratios can be misleading, especially in patients who are suspect for glaucoma or other optic nerve head diseases. Methods: Utilizing fundus photography, we asked optometry students of two different skill levels to evaluate cup-to-disc ratios using 2-dimensional and 3-dimensional images. The images were presented to students at random via two separate online quizzes during which they were asked to unknowingly evaluate the same nerve head in both 2-D and 3-D. Results: Twelve 2nd year students and twelve 4th year students were asked to estimate the cup-to-disc ratios (CDR) of 10 optic nerve heads. In each quiz five were presented as single 2-dimensional images while the other five were presented as stereo image pairs. The more advanced students were able to more accurately estimate the CDR compared to their less
experienced peers. Overall, both sets of students were more accurate when viewing the
optic nerve images stereoscopically rather than monoscopically. Conclusions: Since both the beginning and advanced students were able to judge the CDRs more precisely when viewed in 3-D, it is recommended that stereo photographs be used in some capacity as an instructional tool for training optometry students.