As mentioned, patients may describe optical aberrations as distorted or double vision. Monocular diplopia usually results from abnormalities of the refractive media (eg, uncorrected astigmatism, corneal irregularities such as keratoconus and tear film abnormalities, and cataract). The characteristics of optical causes are seeing ghost images, haloes, or more than 2 images. Monocular diplopia that resolves with use of a pinhole proves there is an optical etiology, obviating the need for a neurologic workup. Less commonly, monocular diplopia can arise from retinal pathology (eg, maculopathy with retinal distortion by fluid, hemorrhage, or fibrosis). Cerebral monocular diplopia or polyopia is always bilateral and extremely rare.
Excerpted from BCSC 2020-2021 series: Section 5 - Neuro-Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.