Monocular Vision: Occupational Limitations and Current Standards

摘要

At the request of the Canadian Forces (CF) Health Services Group, Defence Research and Development Canada (DRDC) - Toronto conducted a literature review on the occupational limitations of monocular vision including recommendations for further work if required. The current CF vision standard for new recruits covers only near and far visual acuity and colour vision. The general entry standard for far visual acuity is a minimum of 6/9 corrected in the better eye and 6/60 corrected in the other eye. Based on that standard, anyone with monocular vision would be excluded automatically. Recently, this policy has been challenged on the grounds that not all military occupational categories require binocular vision. A review of the basic and applied literature and other standards indicated that monocular vision could impact performance on critical military tasks requiring good spatial vision, especially under low illumination and low contrast conditions. However, most of the research compared the performance of people with good visual acuity or contrast sensitivity in both eyes against the same people wearing an eye patch. Research using people with monocular vision finds smaller differences, and in the case of people enucleated early in life, equivalent performance. Possibly more importantly, none of the research has compared people meeting the minimum visual acuity standards for entry into the CF to monocular controls. It is recommended that the performance of people in these two populations should be compared on critical occupational tasks, under low illumination and low contrast conditions. Some of the difficulties in carrying out these recommendations are identified.