Unilaterally extinguished electroretinograms in an eye with normal visual acuity and visual field

Area of Science:

• Ophthalmology
• Neuroscience
• Retinal Diseases

Background:

• Unilateral retinopathy presents diagnostic challenges, especially when initial visual acuity and visual fields are preserved.
• Electroretinography (ERG) is crucial for assessing retinal function, with full-field ERGs (ffERGs) evaluating global retinal response and multifocal ERGs (mfERGs) providing localized information.

Observation:

• A 39-year-old female presented with nyctalopia in her left eye, later showing bilateral fundus pigmentary changes.
• Initial examination revealed normal visual acuity (20/20) and visual fields in both eyes.
• ffERGs were normal in the right eye but extinguished in the left eye; mfERGs were normal in the right and extinguished in the left, with central sparing.

Findings:

• Over 7 years, the left eye developed visual field defects (shading, ring scotoma), while the right eye remained unaffected.
• The extinguished ERG responses in the affected eye served as an early indicator of functional decline.
• Despite normal initial visual parameters, the left eye exhibited progressive functional loss.

Implications:

• This case highlights the predictive value of extinguished ERG responses in identifying eyes at risk for functional deterioration, even with initially normal visual acuity and fields.
• The pathogenesis remains unclear, with possibilities including unilateral retinitis pigmentosa, pigmentary retinopathy, acute zonal occult outer retinopathy, or autoimmune retinopathy.
• Understanding such unique presentations can refine diagnostic approaches and prognostication for rare retinal disorders.