domingo, 25 de noviembre de 2018

Treatment of visual impairment

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By Ananya Mandal, MDReviewed by April Cashin-Garbutt, MA (Cantab)

Depending on the cause and degree of the visual impairment, management can be decided upon.

Types of visual impairment

Visual impairment may mean partial sight, or sight impairment which is defined as:

either having very poor visual acuity (3/60 to 6/60) and having a full field of vision
or having moderate visual acuity (up to 6/24) and reduced field of vision
or having moderate visual acuity (up to 6/18) but severe loss of visual field

Blindness of complete vision loss is defined as extremely poor visual acuity (less than 3/60) and full field of vision or poor visual acuity (between 3/60 and 6/60) with severe reduction in visual field or having average visual acuity (6/60 or above) and an extremely reduced visual field. (1-6)

Registering as visually impaired

Those with severe visual impairment may need assistance and the first step may be to register as visually impaired.

For this the patient needs to be tested by an ophthalmologist.

In the UK a Certificate of Visual Impairment (CVI) is issued to those with visual impairment.

The patient is entitled to benefits such as Disability Living Allowance (DLA), tax allowance a disabled person’s card etc.

Visual impairment means invalidation of the driving license as well. There are around 360,000 people who are registered as visually impaired in England. (1-6)

Considerations for treatment

For management for patients some considerations are important (3) –

The degree of impairment, disability, or handicap
Cause of visual impairment and possible outcome
Age of the patient and level of development
General health of the patient
Patient’s other impairment and adjustment to the vision loss and patient’s expectations from therapy

Treatments for visual impairment

Treatment and management of visual impairment include (1-6):

Control of diabetes – This prevents progression of diabetic retinopathy and resulting visual impairment to some extent. However in advanced cases this may be of little help.
Cataract surgery – In cases of visual impairment due to cataracts, surgery may be opted. Usually an artificial lens is placed within the eye as a replacement of the damaged and clouded lens. This, more often than not restores vision.
Magnification systems – This is achieved using appropriate lens, reading telescopes or surgical systems etc. Hand magnifiers may also be offered. For improvement of visual fields prisms and mirror systems may be prescribed.
Glaucoma – medications in eye drops are prescribed to control glaucoma. These may contain drugs like Latanoprost, tafluprost, travoprost which are prostaglandin analogues.
The drugs may include Beta-blockers like betaxolol hydrochloride or carbonic anhydrase inhibitors dorzolamide and Sympathomimetics like brimonidine tartrate.
Glaucoma may also be managed surgically using open microscopic surgery, laser corrections, etc.
At present there are no cures for age-related macular degeneration (AMD) especially of the dry variety.
For the wet AMD there are therapies that help to stop the progression. These include Photodynamic therapy. This uses a light-sensitive medicine called verteporfin injected into a vein of the arm.
The drug identifies the abnormal blood vessels in the eyes and attaches itself to the proteins in these blood vessels. This is followed by a low-powered laser therapy.
Some new types of medications called Anti-VEGF medication may also be used. One example is Ranibizumab that has recently been approved by the National Institute for Health and Clinical Excellence (NICE) for use on the NHS.