THE OBJECTIVE OF THIS RESEARCH WAS TO OBTAIN NORMATIVE DATA FOR 3 MEASURES OF VISUAL ABILITY UNDER SIMULATED NIGHT-DRIVING LUMINANCE (MESOPIC) AND ORDINARY LIGHTING (PHOTOPIC) CONDITIONS, TO COMPARE THE PERFORMANCE OF DIFFERENT AGE GROUPS, AND TO COMPARE RESULTS WITH THOSE OF A PREVIOUS STUDY. A TOTAL OF 371 SUBJECTS AGED 16 TO OVER 60 WERE GIVEN THE TITMUS STANDARD ACUITY TEST AND A TITMUS LOW-CONTRAST TEST AT PHOTOPIC (34 FT-L) AND MESOPIC (0.4 FT-L) BACKGROUND LUMINANCE, THE LATTER SIMULATING NIGHT-DRIVING CONDITIONS. THEY WERE ALSO GIVEN THE ALLEN NIGHT VISION PERFORMANCE TEST WITH A 10 PERCENT CONTRAST TARGET AT 10 AND 0.2 FT-L. COMPARISONS WERE MADE WITH A PREVIOUS STUDY IN WHICH THE NVPT TARGET WAS 50 TO 60 PERCENT. AVERAGE SCORES (THRESHOLDS) WERE HIGHER (POORER) ON THE ALLEN TEST WITH THE 10 PERCENT CONTRAST TARGET THAN WITH THE 50 TO 60 PERCENT, BUT LOWER CONTRAST TARGETS WERE SEEN ON THE LOW-CONTRAST TITMUS TEST. THE RESULTS SEEM TO INDICATE THAT THE ALLEN TEST WITH A 10 PERCENT CONTRAST TARGET MEASURED ABILITY TO SEE LOW-CONTRAST TARGETS AGAINST GLARE IN BOTH PHOTOPIC AND MESOPIC LUMINANCE AND THE TITMUS LOW-CONTRAST TEST MEASURED LOW-CONTRAST VISION OF A DIFFERENT TYPE. AVERAGE LOW-CONTRAST VISUAL DISCRIMINATION DECREASED WITH AGE. HOWEVER, SOME SUBJECTS IN ALL AGE GROUPS EXHIBITED POORER VISUAL PERFORMANCE THAN MOST OF THEIR OWN AND OTHER AGE GROUPS, AND PERFORMANCE BY MOST OLDER SUBJECTS WAS AS GOOD AS THAT OF A LARGE PROPORTION OF YOUNGER SUBJECTS.

T W Forbes

Papers

Low-contrast vision under mesopic and photopic illumination