PURPOSE

To determine whether decreasing illumination of the Pelli-Robson contrast sensitivity (CS) chart and MP-1 microperimeter to low mesopic conditions is more sensitive to vision changes occurring with healthy ageing and in early and intermediate age-related macular degeneration (AMD) and whether these mesopic tests can differentiate visual function between healthy older participants with and without AMD risk genotypes.

METHODS

Retinal sensitivity was measured in 98 healthy participants (19-85 years) and 21 AMD (AREDS Grade 2/3) patients (73.9 ± 6.5 years) using the Pelli-Robson CS chart and MP-1 microperimeter under low mesopic and standard illumination. The effect of ageing and AMD on retinal sensitivity was estimated using regression analysis. Healthy older participants (>50 years; n = 24) were genotyped for AMD risk genes CFH and/or ARMS2 and retinal sensitivity was compared between genotypes.

RESULTS

With healthy ageing, photopic and mesopic Pelli-Robson CS showed a similar decline (-0.004 log CS/year). In AMD, photopic CS showed a similar decline to healthy ageing (-0.004 log CS/year) while mesopic CS was significantly reduced (-0.007 log CS/year). Both standard and low mesopic microperimetry showed a significant decline (-0.51 and -0.73% contrast/year) with healthy ageing and greater decline (-0.73 and -0.99% contrast/year) with AMD onset. Pelli-Robson CS and microperimetry sensitivity did not differ between AMD risk genotypes in healthy participants.

CONCLUSIONS

Mesopic Pelli-Robson CS detects functional deficits before photopic CS in early and intermediate AMD that can be differentiated from ageing. This test can be easily administered in clinical practice and may provide a means for early detection of retinal dysfunction.