Abstract
Purpose :
To establish the limits of monocular and binocular spatial vision that describe only changes that can be attributed to healthy aging. To investigate the advantages of using briefly presented stimuli and mesopic light levels to detect the earliest changes in spatial vision that can be attributed to ocular or systemic disease.
Methods :
Photopic and mesopic Visual Acuity (VA) and Functional Contrast Sensitivity (FCS) were measured under binocular and monocular viewing conditions using briefly presented (180ms), Landolt-ring optotypes in negative and positive contrast. 251 subjects (age range: 10-77) participated in the study. The screening procedure included detailed medical and ocular histories and a thorough ophthalmic examination. The stimuli were generated on a high resolution visual display using the Acuity-Plus (AP) test developed at City, University of London. VA was also measured using a standard ETDRS test chart under photopic conditions.
Results :
The results reveal only a gradual increase in VA and FCS thresholds with increasing age under photopic conditions. The gap acuity of ~ 0.8 min arc measured in young subjects increases only gradually up to 50 years of age, but a larger increase of ~ 0.25 min arc / decade was observed from 50 to 80 years of age. Under mesopic conditions, these results were more pronounced. VA and FCS measured with negative contrast stimuli produced smaller and less variable thresholds. The ETDRS test chart tended to yield higher acuity for all ages and was less correlated with age when compared to the AP test.
Conclusions :
VA and FCS thresholds increase gradually in normal ageing with a more rapid increase above the fifth decade. VA thresholds measured with the AP test were significantly higher and more strongly correlated with age when compared to conventional, ETDRS thresholds. Preliminary AP test data in subjects with macular disorders such as age-related macular degeneration reveal larger differences in VA thresholds when compared to ETDRS results. Our findings suggest that in addition to spatial deficits, patients with early-stage macular disease have severely impaired temporal processing. Short duration stimuli are often perceived as having reduced spatial contrast. The AP test is therefore more sensitive in detecting vision loss in macular disease.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.