Optic Disk Size Assessment Techniques: Photo Essay

Measuring optic disc size is an essential part of the optic nerve head for evaluation for glaucoma. Large discs that appearing to have large cups may in fact be physiologic because of normal neuroretinal rim area. Small discs may appear to have a normal cup to disc ratio, but have decreased neuroretinal rim area in association with glaucoma. We illustrate relevance of these points with respect to glaucoma diagnosis in two case examples. We then present clinically relevant techniques to assess disc size including direct ophthalmoscopy, slit lamp biomicroscopy, disc macula: disc diameter ratio, planimetric assessment of fundus photographs, and imaging modalities such as OCT as well as HRT.