Title: Detection of early macular functional changes using slow double-stimulation mfERG paradigm

WONG H. Y., CHIN M. P., LEE C. W., YUNG M. Y.,CHAN H.H.L.

Labouratory of Experimental Optometry (Neuroscience), School of Optometry, The Hong Kong Polytechnic University

Purpose: To investigate whether this new multifocal ERG (mfERG) paradigm could detect early macular functional changes in early dry age-related macular degeneration (ARMD)

Methods: Twenty one Chinese subjects, aged from 41 to 65 years (mean = 54±7), with early macular changes in at least one eye were recruited from the Optometry Clinic of The

Hong Kong Polytechnic University. The conditions of macula varied from very mild macular pigment change to about 15 medium-sized drusen around the macula, and the eye with more observable macular changes was selected. They were compared with twenty one age-matched control subjects, aged between 42 and 63 years

(mean=53±7). The mfERG was measured by using a slow double-stimulation mfERG paradigm.

Main Outcome Measures: Amplitudes and implicit times of the first (M1) and second (M2) stimulation

Results: In the central region, the ARMD group had a lower M1 amplitude than the control group but the difference was not statistically significant (p>0.05). Split-Plot ANOVA revealed that region had a significant main effect (p<0.05) while the interaction

(region X group) was barely insignificant (p=0.057). The ARMD group had a significantly lower M1: M2 amplitude ratio than the control group (p<0.05) while this differentiation was not present in the peripheral region (p>0.05). The M1:M2 amplitude ratio at central showed a sensitivity of 57.1%, with a specificity of 85.7% for differentiating normal eyes from early dry ARMD eyes.

Conclusions: Our findings suggest that the new mfERG paradigm is sensitive to detect early ARMD.

The application of M1: M2 amplitude ratio at the macula can be an effective parameter for detecting functional deterioration in early ARMD. The weaken M1: M2 amplitude ratio may indicate an early abnormal adaptive change in ARMD at macula.