Reading newsprint but not headlines: pitfalls in measuring visual acuity and color vision in patients with bullseye maculopathy and other macular scotomas

Abstract

Purpose: To illustrate the confounding factors when assessing visual acuity and color vision in a patient with a bullseye macular scotoma in one eye and a horseshoe of atrophy sparing the fovea in the fellow eye.

Methods: Case report. Visual acuity, color vision, and scanning laser ophthalmoscope analysis.

Results: The patient with geographic atrophy from age-related macular degeneration in both eyes had visual acuity of 20/40- in the right eye and 20/40+ in the left eye. She reported that she could read newsprint but not news headlines. She could not identify any color plates, but had only minor errors using a color cap (large D-15) test. She had a macular ring scotoma (bullseye scotoma) in the right eye, and a horseshoe-shaped area of atrophy surrounding the fovea in the fellow eye.

Conclusion: Scotomas surrounding but sparing the fovea can lead to difficulty reading large letters, because these letters do not fit in the spared foveal region. Care must be taken in measuring visual acuity in these patients so that the testing does not stop when the patient cannot read the largest letters. The presence of scotomas in the central field may not allow the whole figure on color plate testing to be integrated and identified, leading to a possible misdiagnosis of cone dystrophy. Color cap testing avoids this problem.