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MANAGING OPEN ANGLE GLAUCOMA

Figure 3: Optic disc size assessed at the slit lamp biomicroscope with handheld high power convex lens

Generally, Caucasian and highly hyperopic individuals (> +5D) tend to have smaller ONHs, whereas Asian, Hispan-
ic, African American, and highly myopic individuals (> -8D) are the opposite. Large ONHs may have significant
160
physiologic cupping, while small ONHs with minimal cupping may be glaucomatous: small discs merit particularly
close scrutiny, as glaucoma is frequently overlooked. 161-164

Although glaucoma is known as a disease of asymmetry, an inter-ocular cupping difference >0.2 is only suspicious
in ONHs of equal size, and asymmetries in ONH size are relatively common. As a rule, clinicians tend to overesti-
165
mate disc size and underestimate cup size on clinical examination, leading to an optimistic assessment of neuroreti-
nal Rim width as thicker than it actually is.

CANADIAN JOURNAL of OPTOMETRY | REVUE CANADIENNE D’OPTOMÉTRIE VOL. 79 SUPPLEMENT 1, 2017 21