Abstract
Purpose :
To investigate the impact of chromatic blur with positive and negative optical defocus on retinal electrical response using multifocal-electroretinogram (mf-ERG).
Methods :
Eight adult emmetropes (aged 22 to 29 years) with normal ocular health were enrolled in the study. Multifocal-ERG was performed six times on both eyes according to the following conditions: in focus (focused on retina), positive defocus (+2D) and negative defocus (-2D) conditions with short-pass (blue) and long-pass (red) filters. Two neutral density filters that matched the transmittance of each colored filter were used as a control. The mf-ERG instrument (Diagnosys LLC) was used per manufacturer's protocol. Two drops of 1% Cyclopentolate ophthalmic solution were instilled with 5-minute interval for complete cycloplegia. The mf-ERG stimulus pattern subtended 60 degrees horizontally and vertically at a working distance of 33 cm. The amplitudes and implicit times of the P1 wave component were analyzed by grouping the responses into five concentric rings.
Results :
Among the experimental conditions, the P1 amplitude demonstrated a significant difference between red and blue filters in the central ring in all three conditions (P=0.002). The interaction between color filters and type of defocus was statistically significant (p= 0.045). With the red filter, positive defocus showed higher P1 amplitude compared to negative defocus, whereas the blue filter showed higher P1 amplitude with negative defocus than with positive defocus (Figure 1). The implicit time of P1 of all rings was not significantly different (P=0.9).
Conclusions :
The findings of this study suggest that the change in the P1 amplitude of the retinal response was consistent with ocular chromatic aberration. Previous studies have shown the paracentral and near-peripheral retina is able to differentiate between positive and negative defocus. Based on this pilot study, chromatic aberration could be the mechanism the retina uses to identify and differentiate positive from negative defocus.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.