LOW CONTRAST AND STANDARD VISUAL ACUITY UNDER MESOPIC AND PHOTOPIC ILLUMINATION

IN VIEW OF RECENT REPORTS ON THE IMPORTANCE OF LOW CONTRAST VISION UNDER NIGHT DRIVING CONDITIONS, A STUDY WAS CARRIED OUT TO OBTAIN NORMATIVE DATA USING BOTH LOW CONTRAST AND STANDARD ACUITY MEASUREMENTS. THE ALLEN NIGHT VISIBILITY PERFORMANCE TESTER AND THE TITMUS VISUAL ACUITY TESTER WERE USED UNDER LOW ILLUMINATION (MESOPIC) AND ORDINARY ROOM ILLUMINATION (PHOTOPIC) TESTING CONDITIONS. SCORES WERE OBTAINED ON A TOTAL OF 202 MALE AND 194 FEMALE SUBJECTS RANGING IN AGES FROM 15 TO OVER 60 YEARS. THE RESULTS INDICATED THE WELL KNOWN DECREASE OF AVERAGE ACUITY WITH INCREASED AGE IN ALL FOUR TEST SCORES. THE ALLEN TEST (50-60 PERCENT CONTRAST) SHOWED NO GREATER LOSS IN AVERAGE SCORES THAN DID THE TITMUS TEST (90 PERCENT CONTRAST) UNDER MESOPIC CONDITIONS. BOTH TESTS SHOWED A NUMBER OF INDIVIDUAL CASES OF VISUAL DISADVANTAGE UNDER THE SIMULATED NIGHT OR MESOPIC CONDITIONS. THE NIGHT VISIBILITY PERFORMANCE TEST SCORES CORRELATED HIGHLY WITH EACH OTHER (.84) AND CORRELATED ABOUT .50 WITH EACH OF THE NORMAL ACUITY TITMUS SCORES. THERE WERE A NUMBER OF INDIVIDUAL CASES SHOWING NIGHT VISION DIFFICULTY NOT ONLY IN THE HIGHER AGE GROUPS BUT ALSO IN YOUNGER GROUPS. SUCH CASES WERE SHOWN ALSO BY LOW ILLUMINATION HIGH CONTRAST TITMUS SCORES. ANALYSIS OF THE POOREST 20 PERCENT OF SCORES ON EACH TEST SHOWED THAT 46 TO 78 PERCENT WERE THE SAME PEOPLE. THE NIGHT VISION PERFORMANCE TESTER GAVE CONTRAST MEASURES OF 54 TO 62 PERCENT RATHER THAN THE SPECIFIED 10 TO 20 PERCENT. THIS MAY ACCOUNT FOR DIFFERENCES FROM VERY LOW CONTRAST RESULTS PREVIOUSLY REPORTED. THE QUESTION IS RAISED WHETHER 50 PERCENT CONTRAST MAY NOT BE MORE NEARLY WHAT IS MET IN NIGHT DRIVING. IN THIS CASE THE RESULTS INDICATE A VISUAL DISADVANTAGE IN NIGHT DRIVING BY SOME MEMBERS OF ALL AGE GROUPS. THIS TYPE OF TEST INFORMATION IS PROBABLY OF MORE VALUE FOR ADVISING DRIVERS WITH DIFFICULTIES THAN FOR LICENSING PROCEDURES.

• Supplemental Notes:
  • Vol 1, No 1, PP 5-12, 5 FIG 1 TAB, 6 REF
• Corporate Authors:

  N/A

  ,   United States 
• Authors:
  • Forbes, T W
  • Pain, R F
• Publication Date: 1969-3

Media Info

• Serial:
  • Safety Research Journal
  • Publisher: N/A

Subject/Index Terms

• TRT Terms: Age; Alternatives analysis; Drivers; Gender; Light; Measurement; Measuring instruments; Night visibility; Vision; Visual perception
• Old TRIS Terms: Driver vision
• Subject Areas: Highways; Safety and Human Factors; Society;

Filing Info

• Accession Number: 00220500
• Record Type: Publication
• Source Agency: Nat Safety Council Safety Res Info Serv
• Files: TRIS
• Created Date: Mar 22 2003 12:00AM