Optic Disc Size in Glaucoma Patients Attending a Tertiary Institution in Nigeria

Background: Assessment of optic disc size is an important component of optic nerve head examination which is often overlooked in the diagnostic evaluation for glaucoma. Measured values of optic disc size vary with the measurement technique utilized. The actual disc size varies with race and possibly other demographic characteristics. Disc size is also associated with variation of specific anatomical structures of the optic nerve head and the retinal nerve fiber layer. These disc size-dependent variations are risk factors for glaucoma or affect the likelihood of glaucoma diagnosis [1].

Aim: To report the clinical (measured by biomicroscopy) disc diameters of small, average and large optic discs and produce data on the disc sizes of Nigerian patients who have been diagnosed with glaucoma and are currently undergoing treatment.

Materials and Methods: One hundred eyes of 100 glaucoma subjects were studied. Disc diameter was measured using stereo biomicroscopy (78 D). Discs were classified into small (<1.3 mm2), average (1.3-1.75 mm2) and large (>1.75 mm2) using the European Glaucoma Society Guidelines [2,3]. The relationship between disc size and age, sex and type of Glaucoma was also assessed.

Results: One hundred eyes of 100 individuals were studied comprising 64 (64.0%) males and 36 (36.0%) females. Age range was 20- 80 years with a mean age of 50±13.66.

Mean disc size was 1.99±0.239. Eighty-two percent of discs were large size (>1.75 mm2). Males (61%) had larger discs than females (21%) (p=0.001). There was no correlation between disc size and age (p=0.87) or clinical types of glaucoma (p=0.59).

Conclusion: Majority had large optic discs in our study (82%). Large discs have large cup: Disc ratio. These differences must be considered while evaluating the optic disc to prevent over diagnosis of glaucoma and its attendant economic burden on the patient.