Monocular vision (sight in one eye)

It is perfectly normal to need some time to adjust to losing the sight in one of your eyes – both emotionally and practically.

When you lose vision in one eye it’s common to experience some uncomfortable symptoms as your visual system adjusts to this new way of seeing.

You’ll only be using one eye instead of using both eyes as a pair which can affect 3-dimensional (3D) vision. This can initially cause some problems for people with things like depth perception (judging the height of steps or correctly gauging how to pour liquid into a cup for example).

Monocular vision can also affect your field of vision on the affected side reducing the area you can see to that side when looking straight ahead. You may not notice people or objects on the affected side particularly in unfamiliar or crowded environments.

If the sight loss is not complete, it may also cause things to appear less clear, as the poor sight in the affected eye can "interfere" with vision from your good eye.

People can also find that their eyes can become tired sometimes after very little effort as the eyes are trying to work to make the best of the remaining vision. You can continue using your good eye for activities such as reading or watching television; this won’t damage your eyes. However, you may find it helpful to take regular breaks from these tasks to prevent your eyes from becoming tired or fatigued.

In the main, the solution to these problems is a natural adjustment which happens over time. Our brains are adaptable and can adjust to this change in vision. Usually, people find that with time their good eye ‘takes over’ and tasks that were previously difficult become easier. Difficulties with depth perception also improve naturally as the visual system uses other clues to help with this problem, such as the size and position of objects in relation to each other, as well as other texture, shadow and light effects.

It’s difficult to say how long this adjustment will take as this is very individual. Sudden loss of vision in one eye can take longer to adapt to than if the vision loss has happened gradually. However, once someone has adjusted to monocular vision, they find that they can read, watch television and perform many daily activities without any problems.

Here are a few ideas that you may find useful to incorporate into things you do every day.

• When putting a drink down, place the other hand on the table or surface, then place the drink next to it.
• When pouring liquid, gently rest the lip of the container on the rim of the cup or glass.
• It can be difficult to judge the last step on the staircase. Move cautiously, feel ahead with your foot and keep a hand on the banister or handrail.
• You may find it useful when crossing the road, to stop at the kerb for a while to gauge the depth of the kerb and the distance of vehicles before crossing.
• Let friends and family know that it is easier for you if they walk or sit next to you on the side where you can see.
• In crowded areas, some people find that walking with a partner or against a wall on their affected side prevents them from bumping into obstacles.
• You may find you have to turn your head more to see things towards your affected side. With time, this will become more natural.

You may still be able to drive a car or motorcycle if you have monocular vision if your other eye has good enough vision to meet the legal standards set by the Driver and Vehicle Licensing Agency (DVLA), and you have adapted to the sight loss in one eye.

Your ability to judge distances accurately may be affected and you may be less aware of objects on the side that has lost vision. Making better use of your wing mirrors will help. You will also need to bear in mind that blind spots caused by your car’s design will be larger for you if you only have vision in one eye.

For complete loss of vision in one eye (where there is no perception of light in the affected eye), the driver:

• must meet the same visual acuity and visual field standards as binocular drivers (drivers with sight in both eyes). This means that with your unaffected eye you must be able to read a number plate from 20 metres and read down to the 6/12 line (or better) on the eye test letter chart with any glasses or contact lenses you need. Your unaffected eye must also have good all-round field of vision.
• may drive only after clinical advice of successful adaptation to the condition. This means that you should not drive until you have been advised by your doctor or optometrist (optician) that you have fully adapted to monocular vision.

Any driver with monocular vision must notify the DVLA if they fail to meet these requirements. If you live in Northern Ireland you must contact the Driver & Vehicle Agency (DVA). Your ophthalmologist (hospital eye doctor) or optometrist will be able to advise you further about these requirements and let you know whether you need to notify the DVLA or DVA.

If you hold a Heavy Goods Vehicle or Public Service Vehicle licence (bus or lorry licence), the rules and requirements are different, and you must let the DVLA or DVA know about your monocular vision. You will probably need to complete a V1V form from the DVLA. In Northern Ireland, contact the DVA.

RNIB cannot give permission for you to carry on driving. If you have any doubt about whether you can meet the visual requirements for driving, your GP, optometrist, or ophthalmologist will be able to advise you.

Many people who have sight in only one eye consider themselves partially sighted. However, an eye consultant will not be able to certify you as “Sight Impaired/Partially Sighted” because you would not meet the criteria unless you also have a significant loss of sight in your other eye. This is because both eyes need to be affected by loss of vision to meet the criteria for certification. The criteria for certification and registration are set nationally by the Department of Health and applied at the discretion of a consultant ophthalmologist.

If you have some loss of sight in your other eye as well then it is worth discussing the possibility of registration with your ophthalmologist.

It’s important for people who have good sight in only one eye to have regular eye examinations with an optometrist so that the health of the eye they rely on can be monitored. Your optometrist should let you know how often you need to have your eyes examined.

For people who have sight in only one eye, it may be a good idea to use protective eyewear or sports goggles for certain sports or activities, such as gardening or DIY, to prevent injury to the good eye. You can speak to a dispensing optician at your local optician practice for more advice about this. Dispensing opticians are qualified in the dispensing and fitting of eyewear and can give professional advice about suitable protective frames and lenses.

If you have further questions about monocular vision, please get in touch with our Sight Loss Advice Service by calling 0303 123 9999.

Artificial Eyes provides some useful information on adapting to monocular vision which may be helpful for people who have lost sight in one eye.