Distinguishing between clinical impairments due to optic nerve or macular disease

Many optic neuropathies and subtle maculopathies may have similar clinical presentations. This represents a challenge to the ophthalmologist to distinguish between the two on clinical grounds. These patients may not have obvious signs and their symptoms may be ambiguous. For example, a young man presenting with optic neuritis may have similar complaints to one suffering from central serous retinopathy. Several general principles can be used to distinguish between optic neuropathies and maculopathies. Additionally, specific psychophysical tests can be of help. The most important aspect of the history is in establishing the tempo of onset, duration and resolution of the symptoms. Optic nerve lesions often produce symptoms described as dimness or grayness, whereas macular lesions usually reduce visual acuity and produce metamorphopsia. The clinical examination requires comparing optic nerve function studies (afferent pupillary defects, color vision and brightness sense) to visual acuity. Additionally, assessing the central visual field especially through Amsler grid testing or threshold Amsler grid testing is very useful. Certain psychophysical tests can be performed in the office. Threshold amsler grid testing, photostress testing, contrast sensitivity, and the Pulfrich phenomena can all be put to advantage in distinguishing between optic neuropathies and maculopathies.