What is monocular vision?
When there is vision loss in one eye due to eye diseases or eye injuries, you only get useful vision out of the fellow unaffected eye. This is called monocular vision impairment.
As we normally see the world through both eyes (what we refer to as binocular vision), people with only useful vision in one eye may need to adapt to monocular vision. Majority of people are able to develop adaptation with time and go on to resume a normal lifestyle.
Monocular vision loss may be partial or complete. With partial vision loss, there may be some remaining vision in the affected eye, which can help with peripheral vision and some degree of depth perception.
How does having good vision in one eye only affect your work, lifestyle and driving?
Most people with monocular vision can function in a normal occupation, though specific tasks such as operating heavy machinery, military work, driving heavy vehicles, working on heights, or tasks which require fine motor skills may be restricted or difficult to perform. A period of readjustment in the workplace with increased time and care in performing tasks may be required to adapt to monocular vision.
Driving a motor vehicle is legal in the State of Queensland with monocular vision, provided that the remaining eye has good vision and field of view, certified by your doctor and notified to the Department of Transport. A period of readjustment to monocular driving may take 3 months or more and driving re-training may be required. A list of occupational therapy driving instructors is available below.
With monocular vision, the horizontal field of vision is reduced to approximately 140° compared to 180° of normal stereoscopic vision. As a result, monocular patients need to compensate by turning their head more often to the side of the vision loss. It is hence important when driving a motor vehicle to scan both sides of the field of vision, particularly the side with the vision loss.
Initially there may be a period of eye strain when adapting to monocular vision, and it is important to optimise any refractive error in the remaining good eye, with distance and reading spectacle correction if necessary. Good lighting whilst working and reading is also important.
Mobility around objects requires stereoscopic cues such as shadows and size disparity to determine relative distances between objects. When walking on uneven ground, it is important to look and scan downwards more often to determine the surface and objects ahead of it. Exercise caution particularly in the kitchen when pouring a cup of tea or cooking on a stove. Practice bouncing a ball may assist in developing stereoscopic cues.
It is important to always wear eye safety protection when performing tasks at risk to the eyes such as playing ball sports, working on a construction site, or home workshop, and avoid hitting metal-on-metal which can cause shrapnel.
In some circumstances where there is distorted or reduced vision in one eye, causing confusion with the good vision from the better eye, a form of occlusion therapy (such as a patch or spectacle occlusion) in the poorer vision eye may be beneficial. Often over time, brain adaptation will occur, blocking the signal of the poorer vision from the affected eye, such that patients may no longer notice the distorted vision.
What happens when you require surgery in the remaining good eye?
Whenever a procedure is required to be performed in the remaining good eye, particular information needs to be obtained from the treating doctor, regarding the risks, benefits and the rehabilitation time required to return to normal vision. This is important where there is a significant recovery time when vision will be reduced in the remaining good eye.
Following the surgery including the anaesthetic recovery time in the immediate post-operative phase, vision may be slow to recover following the peribulbar anaesthetic used in the procedure. It is important that all care staff and family members are aware of this, particularly where patients may be treated in a day surgery situation, and where the good eye may have a patch over it. Prior planning and care during the recovery period is important for the safety of the patient.
The following links on references, cosmesis, counselling and support services available in Queensland may be useful in assisting with the adaptation process. Most patients fortunately adapt over time and function well without obvious impairment.
A good video regarding monocular vision:
Support services available in Queensland:
Occupational therapy driving assessments: