The effect of light scattering on multifocal electroretinography

Area of Science:

• Ophthalmology
• Neuroscience
• Visual Science

Background:

• Unclear ocular media, common in older eyes, causes light scattering and image degradation.
• Multifocal electroretinography (MERG) objectively measures retinal activity, but its use with cloudy media is uncertain.

Purpose of the Study:

• To evaluate the validity of MERG under controlled light scattering conditions simulating cloudy ocular media.
• To assess how image degradation affects MERG responses in normal subjects.

Main Methods:

• MERG recordings were obtained from 13 young subjects with and without a liquid crystal diffuser (LCD) simulating scatter (visual acuity ~6/18 vs. ~6/6).
• MERG waveforms were analyzed, focusing on the first-order kernel response.
• Three subjects were tested at intermediate scattering levels (visual acuity ~6/9 and ~6/12).

Main Results:

• Light scattering significantly reduced macular MERG response density (p < 0.001) but increased peripheral response densities (p < 0.001).
• A novel retinal response (P60) was identified, which diminished under scattering conditions.
• Similar trends were observed at intermediate light scattering levels.

Conclusions:

• Veiling luminance from light scatter may explain reduced macular and elevated peripheral MERG responses.
• The observed suppression of P60 suggests retinal adaptation to light scatter.
• Cloudy ocular media significantly affects MERG interpretation.