Gradual Loss of Vision
The four major causes of gradual blindness in the world are: cataract, onchocerciasis, vitamin A deficiency and trachoma. The latter three are very rare in the UK. Cataract occurs in 75% of over-65 s, but only 20% of 45- to 65-year-olds. Most cases of gradual loss of vision encountered in primary care arrive via the optician, often with a letter outlining the problem and suggesting referral to an ophthalmologist.
- Chronic Glaucoma
- Diabetic and Hypertensive Retinopathy
- Senile Macular Degeneration
- Gradual Inferior Retinal Detachment
- Optic Neuritis (in MS)
- Paget’s Disease of the Skull
- Retinitis Pigmentosa
- Intraorbital or Intracranial Tumours
- Cerebromacular Degeneration
- Toxic Amblyopia (Tobacco, Methanol, Arsenic, Quinine, Carbon Bisulphide)
- Choroidal Melanoma
- Leber’s Hereditary Optic Atrophy
Key distinguishing features of the most common diagnoses
|Cataract||Glaucoma||Retinopathy||Macular Degeneration||Retinal Detachment|
|Unilateral Visual Loss||Possible||Possible||Possible||Possible||Yes|
|Pigment at Macula||No||No||No||Yes||No|
|Exudate + Haemorrhage||No||No||Yes||Yes||No|
|Disc Cupped >50%||No||Yes||No||No||No|
- The only investigation the GP is likely to perform is a urinalysis and/or blood sugar or HbA1c for suspected diabetes. If glaucoma is a possibility, and the patient has not already seen the optician, then optician referral will provide information about fields and pressures. More obscure tests – such as posterior pole ultrasound and CT scan for retinal, or other, tumours; syphilis serology; skull X-ray for Paget’s disease; and neurological investigations for MS – are rarely required and are inevitably arranged in secondary care.
- Opticians will tend to report cataracts in the elderly routinely. Referral for surgery is only required if the problem is significantly impairing the individual’s normal activities.
- The presence of a cataract in relatively young patients is unusual and should prompt referral regardless of visual impairment – there may be a rare underlying metabolic cause.
- Remember that significant glaucoma or other causes of visual loss may render the individual unfit to drive.
- The elderly patient with a cataract whose vision is not improved considerably with the pinhole test probably has macular degeneration too, and so is unlikely to benefit much from cataract extraction.
- It can be very difficult to establish in an elderly person whether the problem really has been gradual in onset or whether the history is more sudden; if in doubt, refer urgently as the cause may be acute and remediable.
- Progressive early morning headache or proptosis with gradual loss of vision suggests a tumour. Refer urgently.
- Gradual or recurrent visual loss or blurring with other intermittent neurological symptoms, especially in younger patients, suggests the possibility of MS.