While some loss of vision is fairly common, complete loss of vision is relatively unusual.
Causes of Blindness
Blindness can result from disease anywhere along the visual pathways from the eyes to the brain. Causes therefore include not only diseases of the eyes but brain disorders as well.
Most blindness in the developed world results from damage to the retina, which is the light-receiving surface at the back of the eye. This is a densely packed structure where specialized light receptors – the rods and cones – react to light. Much of the initial processing of information takes place in complex nerve interconnections within the retina that begin the recognition of shape, movement and position. The retina needs a good blood supply to function, and interference with it underlies much acquired blindness.
The major causes of blindness are glaucoma, diabetic eye disease (see Diabetes) and macular degeneration. These all affect blood supply to the critical receptors through disease of the blood vessels.
Direct injury to the eye will cause blindness if it damages the lens or destroys the eyeball. This includes detached retina.
The information from the eyes reaches the brain through the optic nerve and is finally analysed in specialized regions of the brain. A stroke may damage some of those fibres. This is unlikely to produce total blindness but it can destroy part of the field of vision. A tumour of the pituitary gland also causes gradual loss of part of the field of vision.
Other important causes are parasite infection of the eye and deficiency of vitamin A, required to make the visual receptors.
Symptoms of Blindness
Abrupt blindness is immediately recognized but a slower onset blindness can be easily overlooked. This is especially true if only one eye is affected because the brain compensates. This happens with glaucoma, diabetic eye disease and also a slow-growing brain tumour.
Blindness after a stroke typically affects only part of the field of vision – one-half or one-quarter – and this too can be overlooked unless specifically tested for. This is done by measuring the whole field of vision with special charts.
The reflexes of the pupils of the eye and the appearance of the back of the eye viewed through an ophthalmoscope give some clue as to the likely cause of blindness.
Treatment of Blindness
Emergency treatment may help when the cause is a detached retina or blockage of blood flow to the retina. Blindness as a result of strokes in the brain cannot be treated but there is a high probability of improvement with time and as the brain compensates. The treatment of trauma, brain tumours and parasitic infections varies from case to case. Early treatment is essential for glaucoma and diabetic eye changes to reduce the risk of deteriorating vision.
How common is blindness?
In the United Kingdom about 140,000 people are registered totally blind; many more are registered as severely visually impaired. Such individuals can often cope well if they are given input from specialized adviseis. Similar peirentages of blindness apply else-tvhere in the developed world.
When can temporary blindness occur?
Migraine can cause loss of vision, usually in one eye, accompanied by headache and nausea. Vision returns after’ an hour or two. Sudden painless loss of vision that recovers within hours is almost certainly due to a stroke. Since this may herald a larger stroke, it is important to have an urgent medical assessment.
Warning: Never use aromatherapy oils near the eyes. No specific therapy is recommended as treatment, but some can ease the stress associated with increasing blindness and help you come to terms with your deteriorating vision – aromatherapy massage to the body can be beneficial in promoting positive acceptance; arts therapies, chakra balancing, healing and hvpnotherapy also have a role here. Other therapies to try: see Stress.