Age-Related Macular Degeneration (ARMD)
Age-related macular degeneration (ARMD) is a medical condition which usually effects older adults and results in loss of vision in the centre of the visual field the (macula) because of damage to the retina. It occurs in "dry" and "wet" forms. It is a major cause of blindness and visual impairment in older adults (>50 years). Macular degeneration can make it difficult or impossible to read or recognize faces, although enough peripheral vision remains to allow other activities of daily life. Starting from the inside of the eye and going towards the back, the three main layers at the back of the eye are the retina which contains the nerves; the choroid which contains the blood supply; an the sclera which is the white of the eye. The macula is the central area of the retina which provides the most detailed central vision.
Glaucoma is an eye disease in which the optic nerve is damaged in a characteristic pattern. This can permanently damage vision in the affected eye(s) and lead to blindness if left untreated. It is normally associated with increased fluid pressure in the eye (aqueous humour). The term 'ocular hypertension' is used for people with consistently raised intraocular pressure (IOP) without any associated optic nerve damage. Conversely, the term 'normal tension' or 'low tension' glaucoma is used for those with optic nerve damage and associated visual field loss, but normal or low IOP.
The nerve damage involves loss of retinal ganglion cells in a characteristic pattern. The many different subtypes of glaucoma can all be considered to be a type of optic neuropathy. Raised intraocular pressure (above 21 mmHg) is the most important and only modifiable risk factor for glaucoma. However, some may have high eye pressure for years and never develop damage, while others can develop nerve damage at a relatively low pressure. Untreated glaucoma can lead to permanent damage of the optic nerve and resultant visual field loss, which over time can progress to blindness.
A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope (lens capsule), varying in degree from slight to complete opacity and obstructing the passage of light. Early in the development of age-related cataract, the power of the lens may be increased, causing near-sightedness (myopia), and the gradual yellowing and opacification of the lens may reduce the perception of blue colors. Cataracts typically progress slowly to cause vision loss, and are potentially blinding if untreated. The condition usually affects both eyes, but almost always one eye is affected earlier than the other.
Diabetic retinopathy is damage to the retina caused by complications of diabetes, which can eventually lead to blindness. It is an ocular manifestation of systemic disease which affects up to 80% of all patients who have had diabetes for 10 years or more. Research indicates that at least 90% of new cases could be reduced if there was proper and vigilant treatment and monitoring of the eyes. The longer a person has diabetes, the higher his or her chances of developing diabetic retinopathy.
Retinitis Pigmentosa (RP)
The progress of RP is not consistent. Some people will exhibit symptoms from infancy, others may not notice symptoms until later in life. Generally, the later the onset, the more rapid is the deterioration in sight. A form of retinal dystrophy, RP is caused by abnormalities of the photoreceptors(rods and cones) or the retinal pigment epithelium (RPE) of the retinaleading to progressive sight loss. Affected individuals may experience defective light to dark, dark to light adaptation or nyctalopia (night blindness), as the result of the degeneration of the peripheral visual field(known as tunnel vision). Sometimes, central vision is lost first causing the person to look sidelong at objects.