PURPOSE. The Heidelberg Retina Tomograph (HRT) is an automated instrument, which performs a 3D morphometric study of the optic nerve. Optic nerve studies were performed on 4,000 European eyes in order to obtain the normal values for each of the parameters listed below. We suspected that the norms might not be an accurate representation of the African-American population. METHOD. Fifty African-American patients ranging in age from 19.5-69 years with a mean age of 40.58 were enrolled in the study. The group consisted of 37 females and 13 males. Each subject received a comprehensive eye exam that included IOPs and dilated fundus exam. Only subjects that did not have glaucoma were allowed to participate in the study Three images of each optic nerve taken thru a dilated pupil were obtained for analysis. Each optic nerve was then analyzed with respect to; cup area, HRT C/D estimation, rim area, cup volume, rim volume, maximum cup depth and nerve fiber layer thickness.
RESULTS. Data reflecting the mean and standard deviation of our 50 subjects for the right eye is as follows, with manufacture’s HRT values in parenthesis. Mean cup area 0.59 (.32), +/- 0.42 (.025), Mean rim area 1.77 (1.73), +/- 0.471 (0.035), Mean cup volume 0.18 (0.06), +/- 0.218 (0.006), Mean rim volume 0.47 (0.48), +/- 0.202 (0.015), Mean max cup depth 0.65 (0.47), +/- 0.218 (0.019), Mean NFL thickness 0.24 (0.24), +/- 0.072 (0.006) and left eye data: Mean cup area 0.59 (0.32), +/- 0.472 (0.025), Mean rim area 1.58 (1.73), +/- 0.414 (0.035), Mean cup volume 0.16 (0.06), +/- 0.212 (0.006), Mean rim volume 0.42 (0.48), +/- 0.179 (0.015), Mean max cup depth 0.65 (0.47), +/- 0.236 (0.019), Mean NFL thickness 0.24 (0.24), +/- 0.068 (0.006). Based on an ANOVA with post hoc student Newman-Keuls: Cup volume, Cup depth and Cup Area were statistically different from the norm at p=.05 level CONCLUSIONS. The results of this study suggest care must be taken when using the HRT on African American patients when accepting the interpretation of normal vs glaucoma status since this population deviates in several respects from the norms established.