Find out the types of vision loss, and how to cope with such a loss.
There is often a blur line between what is considered normal and low-vision. How do you identify this issue within family members, friends and yourself, and at what point do you seek professional help? Dr Anna Tan, a consultant at the Medical Retina Department at the Singapore National Eye Centre (SNEC), shares her thoughts.
First, it is important to understand the difference between low-vision and blindness. Our vision can be measured on a spectrum between regular vision and blindness, with low vision falling on different points in between. Generally, low-vision is defined as “an impairment of visual function, in which the full remediation is not possible by conventional spectacles, contact lenses or medical intervention and which causes restriction in that person’s everyday life”. A common way to quantify low-vision is if a person exceeds 6/15 in the “better” eye.
Types of vision loss
There are two types of vision loss which doctors have categorised – reversible and irreversible. Some conditions that are reversible include dry eyes, cataracts and refractive error which medication, corrective glasses or surgery may be able to solve. Conversely, other forms of vision loss may be irreversible. In either case, with the right aids, there are ways people with low-vision can cope better on a day-to-day basis.
Vision loss can occur in various patterns, which can be broken down into the following:
- Central vision loss – This occurs when the centre of your vision is blurred or “blacked out”, while the perimeter around it remains. To put it simply, it resembles a hole in your vision. This commonly occurs when people get older, associated with conditions such as diabetes, age-related macular degeneration (AMD) or inherited retinal diseases.In such a situation, the person may face difficulties with simple tasks such as counting money, using the computer and reading. One of the most significant challenges causing much distress in many patients is the inability to identify loved ones and recognise their facial expressions. Parts of sentences in a book may be missing a few words making it difficult to follow and a missed smile or frown may cause a loss of confidence for the individual in social situations.
- Peripheral vision loss – This is when the centre of one’s vision remains, while the perimeter around it is lost. Glaucoma patients often experience this, a condition characterised by optic nerve damage and in most times, high pressures in the eye.In some cases, it may not be easy to detect the condition immediately as the initial vision loss is at the far periphery. Central vision may be preserved until the condition becomes severe. As time progresses, the peripheral vision may slowly be lost and the field of vision slowly diminishes. Doctors are able to conduct a visual field test and examine your optic nerves to detect if a person is indeed experiencing early peripheral vision loss that may be associated with glaucoma. If glaucoma is detected, the appropriate treatment may be recommended by your doctor with follow-up to monitor for disease progression.
- Other types of vision loss – Amongst other types of vision loss, there is vision loss whereby half of your visual field is lost and also affects both eyes. Some causes of such a vision field pattern loss include a stroke in the brain, brain tumours or trauma to the brain, which affects its ability to command the eyes to function normally.Similar to peripheral vision loss, a person may not be immediately aware that his or her sight is deteriorating. This can be dangerous as when vision gradually becomes limited, it can cause the patient to get into accidents.
Coping with vision loss
There are multiple and significant effects of vision loss on patients. Physically, some can experience mobility difficulties and an inability to cope with daily activities. This can also affect them on a mental or emotional level. For some, it can cause a loss in confidence in leaving the safety of their homes and going outdoors. In more severe cases, this can lead to isolation from the community and society.
While a patient with irreversible vision loss is unable to regain his or her sight, in some conditions, there are ways to slow down or avoid the condition from deteriorating. Based on the underlying condition, doctors may recommend treatment options to manage the different types of vision loss. For example for glaucoma patients, medication in the form of eye drops can help to lower eye pressure and slow down the progression of vision loss.
At the end of the day, early detection of the disease and early intervention are key to preventing permanent vision loss in many diseases. Eye checks are recommended for anyone experiencing difficulties with their vision. If mild blurring of vision is noted, an optometrist can prescribe glasses or a local general physician may be able to screen for any serious eye conditions and refer the individual to a specialist if required. SNEC and other organisations also hold public eye screenings – some which may be free – at various times every year advertised in the newspapers; attending one of these session allow the individual to be screened for any serious eye disease.
If you or a loved one you know experiences low-vision or blindness, there are many programmes which can help assist you to live independently and maximise what remaining vision you have left. For example, the Singapore National Eye Centre (SNEC) currently runs a programme to provide support for those above the age of 50. These services include specialised optometrists to assess the type of vision loss, prescribing the necessary visual aids such as magnifiers or digital devices as well as introducing and training the individual on how to use some applications available on smartphones and tablets. Occupational therapists in the team are also at hand to provide solutions to improve the individual’s daily functioning and even in some cases modify the home environment to ensure safety and function. Other related services if required include a social worker who can provide counselling for emotional issues, assist with job placements and connect the individual with services available to the visually-impaired in his or her local community.
(** PHOTO CREDITS: Singapore National Eye Centre)