Introduction
Low vision is an irreversible or permanent loss of sight. It cannot be corrected through medical or surgical treatment or by the use of prescription eyeglasses or contact lenses. Low vision is different from complete blindness in that the patient still has a degree of sight left.
The eye disorder includes various degrees of loss of vision such as:
- Hazy vision – Where the patient’s entire visual field seems to be covered with a glare or film.
- Loss of central vision – Where there is a black or dark space in the center of the visual field.
- Night blindness – Inability to see well outside at night or in places with low lighting such as theaters.
- Loss of side (peripheral) vision - The patient can’t see anything either above or below the eye level or to the side. But their central vision is not affected.
- Blurred vision – Where objects are out of focus, both near and far.
People with visual impairment must learn to live with it. The great news is that there are many ways to assist people with low vision to live independently.
Also Known As
- Visual impairment
- Vision loss
Sub-Types
Low vision can be categorized into two broad groups:
- Partial vision - People who use conventional prescription lenses and have a visual acuity between 20/70 and 20/200.
- Legally blind – Patients with vision 20/200 and above. They also have restricted visual field of less than 20 degrees wide.
Causes and Risk Factors
Low vision in children can occur due to an injury or a congenital disability. In adults, it may be a result of a variety of diseases and injuries. Common causes of visual impairment include:
- Diabetic retinopathy
- Retinal detachment
- Retinitis pigmentosa
- Retinopathy of prematurity (ROP)
- Macular degeneration
- Amblyopia
- Traumatic brain injury
- Glaucoma
- Cataracts
- Stroke
- Albinism
- Eye trauma
- Cancer of the eye
Age is a risk factor. The eye disorder is common in people over 45, and even more common in those above 75.
Signs & Symptoms
Signs and symptoms of low vision may include:
- Difficulty reading
- Headaches
- Reduced visual acuity or visual field
- Confusion when performing visual tasks
- Glare sensitivity
- Balance problems
- Blurred vision
- Double vision
- Eye misalignment
- Poor judgment of depth
- Dizziness
- Abnormal body posture
- Contrast sensitivity
Diagnosis
The eye care professional performs a comprehensive eye exam. It may include:
- Slit lamp examination
- OCT
- Dilated eye test
- Electroretinography
- Visual field testing
- Fundus photography
- Color testing
Treatment
Treatment is aimed at correcting the underlying cause.
Medical Treatment
The eye doctor may prescribe eye drops for glaucoma, anti-VEGF therapy for macular degeneration or steroid treatment for patients who have had cataract surgery.
Surgical Treatment
Laser therapy may seal bleeding and fluid leakage from the retinal vessels. It prevents further loss of vision due to fluid build up in the macula.
Surgery can drain fluid from inside the eye, remove scar tissue and repair detached retinas. It can also replace a cloudy lens or a damaged cornea.
Vision Aids
Where conventional prescription lenses, medical treatment or surgery can’t help to correct the patient’s vision loss, the eye doctor helps the individual to take the next step towards coping with the condition.
He/she refers the patient to a low vision specialist who assesses the extent and form of vision loss. The specialist will prescribe low vision aids and guide the patient on how to use them. Vision aids include:
- Handheld and freestanding magnifiers
- Telescopic glasses
- Reading prisms
- Magnifying glasses
- Lenses that filter light
- Closed-circuit television/video magnification
The specialist may also recommend non-optical aids. The popular devices include:
- Large-print publications
- Text-reading software
- Books on DVD/CD/audio cassette
- Talking watches and clocks
- Check-writing guides
- Clocks, phones and watches with large numbers
- High-contrast clocks and watches
Prognosis/Long-term outlook
Children with a visual impairment may have learning difficulties that need special instruction. They may also need assistance in developing social skills.
Vision impairment in adults and seniors can be very traumatic. Often, it leads to frustration and depression.
Vision rehabilitation therapy can train patients to maximize the remaining vision and lead a quality life.
Prevention/Follow Up
Preventive measures depend on the cause. For example, regular exercise and a healthy diet can help to prevent low vision in people with diabetes.
Protective gear can also prevent eye injuries.