The ageing eye
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As we age, there is a possibility of reduced vision. A look at ARMD and treatment options.
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Normal field of vision...
WHAT is age-related macular degeneration?
Age-related macular degeneration (ARMD) is a very common cause of reduced vision. As the name suggests, it is a condition that tends to become more common as people get older. Although this condition may cause significant reduction in vision, it never leads to complete blindness as it affects only the central part of the vision and the side, or peripheral, vision is always left intact.
The retina, which is situated at the back of the eye, transmits the images that we see to the brain. The retina has two main parts — the macula and the peripheral retina. The macula is the part of the retina that is responsible for seeing fine detail, such as reading, seeing facial features and interpreting different colours. It is this part of the retina that is affected by age-related macular degeneration.
How does ARMD develop?
This is an ageing change and occurs because of "wear and tear" changes in the macular region. It is thought that waste materials from this very active part of the eye build up as the mechanisms for removing them become less able. This causes damage to the cells over a period of time.
What happens in ARMD?
The retinal pigment epithelium, which is the outer layer of the retina, fails to carry out its function as a result of which there is accumulation of the breakdown products.
What are the types of ARMD?
There are two types namely Dry and Wet type
Dry type is caused by aging and thinning of the tissues in the macula, which results in gradual visual loss. It is characterised by yellowish deposits in the macular region which may undergo subsequent atrophy or may progress to wet form.
Wet type results from abnormal new vessel formation. The new vessels can lead or bleed resulting in sudden and severe loss of vision.
How does a patient with ARMD have symptoms?
... and a person with AMRD
Most people do not have many symptoms except for blurring of vision. The Amsler Grid test evaluates 10{+o} surrounding the fixation. The Amsler Grid is a chart which the patient is asked to look at for diagnosis of early Macular disorders. A patient with ARMD perceives a straight line as distorted. In advanced cases, the vision in the central area is completely affected and patient is unable to see any grid pattern.
There are two main diagnostic tests for ARMD:
Fundus Fluorescein Angiography
Indocyanine green angiography
Fundus Fluorescein Angiography allows visualisation of blood flow in retinal and choroidal tissues, permitting diagnostic support in many ocular diseases. In particular, fluorescein angiography has become a very important tool in the diagnosis and treatment of macular diseases. However, limitations of fluorescein angiography in imaging the choroidal circulation and associated pathologies prompted the use of alternative dyes like Indocyanine green to improve choroidal angiography.
Indocyanine green angiography is a diagnostic study where Indocyanine green dye, is injected intravenously, and observations of the retina are made at intervals for assessing the integrity of retinal and choroidal circulation. It is effective when used as an adjunct to fluorescein angiography in the diagnosis and treatment of ill-defined choroidal neovascularisation (i.e. associated with age-related macular degeneration).
What are the treatment options available?
The main aim of treatment is not to improve sight but to prevent further deterioration. In the dry type we can monitor patients with the help of special charts called Amsler charts by which we can assess the progress of the disease. Vitamin supplements reduce the impact of ARMD in some people. For patients with difficulty in reading, low visual aids can be prescribed which is usually a special type of magnifying glass, which helps to improve the quality of life.
In the wet type, Laser is the mainstay of treatment. Here, abnormal vessels are coagulated either by a conventional argon laser or by newer modalities like Transpupillary Thermotherapy (TTT) and photodynamic therapy.
TTT represents an emerging a new form of treatment for ARMD patients.
Dr. S. SANJAY
Dr. P. SRIVIDYA
Dr. MOHAN RAJAN
Dr. SUJATA MOHAN
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