Different effect of dioptric defocus vs. light scatter on the pattern electroretinogram (PERG)

Area of Science:

• Ophthalmology
• Visual Neuroscience
• Retinal Electrophysiology

Background:

• Optical deficiencies can influence electrophysiological measures of retinal function.
• The Pattern Electroretinogram (PERG) is a key test for assessing retinal ganglion cell and inner retinal function.
• Understanding how optical quality affects PERG is crucial for accurate clinical interpretation.

Purpose of the Study:

• To quantitatively evaluate the impact of different optical deficiencies on Pattern Electroretinogram (PERG) amplitude.
• To compare the effects of dioptric defocus versus scatter transparencies on PERG responses.
• To determine the clinical relevance of suboptimal refraction on PERG outcomes.

Main Methods:

• Degraded retinal imaging using dioptric defocus (+1.75-5 D) and scatter transparencies.
• Measured visual acuity and steady-state PERG evoked by checkerboards and flash stimuli.
• Equated optical degradation methods based on visual acuity for comparison.

Main Results:

• Scatter transparencies caused a greater reduction in PERG amplitude than defocus when visual acuity was matched.
• Significant PERG amplitude reductions were observed with scatter at 16 degrees, escalating for smaller checks.
• Defocus only showed significant effects for check sizes of 1.6 degrees and smaller.
• Halving visual acuity reduced PERG amplitude by 15% with defocus and 30% with scatter at 0.8 degrees check size.
• No clinically relevant PERG effects were found with acuity of 0.8 or higher.

Conclusions:

• The type of optical degradation significantly influences PERG amplitude reduction.
• Dioptrical defocus may underestimate the impact of media opacities on PERG compared to scatter.
• Suboptimal refraction with acuity above 0.8 does not clinically affect PERG outcomes.