Senile Macular Degeneration

Synonyms: Age-related macular degeneration (ARMD), Macular degeneration

This is a disease of the macular area of the retina characterised by deposition of small colloid bodies (drusen). These are found between the retinal pigment epithelium (RPE) and the underlying Bruch's membrane. They appear at about 45 years of age and increase in size and number. When they reach a critical size and number in the macular area, they give rise to ARMD.
There are two main types of disease:

• Atrophic (dry, non-exudative) - the presence of drusen results in progressive atrophy of the RPE, photoreceptors and choriocapillaris. This is the commonest form of the disease.
• Exudative (wet, neovascular) - there is a growth of choroidal vessels under and into the retina, resulting in a neovascular membrane. Serous fluid may accumulate here causing serous retinal detachment. Furthermore, the vessels may bleed.

This is a bilateral but often asymmetrical disease with second eye involvement in over 60% of cases over 5 years.¹

Prevalence - this is the commonest cause of irreversible visual loss in patients over 50 years old, in the Western world.² 10% of 65-75 year olds and 30% of over 75 year olds are affected to some degree. 1.7% of the population over 50 years of age have severe disease (rising to 18% of the over 85 year olds).
Risk Factors - caucasian background; there is some degree of genetic and environmental factors including smoking.

Symptoms

• Atrophic: progressive, steady decline of central vision (scotoma): difficulty in reading, seeing distant objects, distortion of straight lines ("Does the frame of the doorway look straight?"), micropsia or macropsia (seeing things smaller or bigger than they are). Getting around house is not affected as the peripheral vision spared.
• Exudative: as above but may suddenly deteriorate to profound central visual loss.

Signs

Discrete yellow deposits in the macular area which may become paler, larger and confluent in patients progressing to exudative ARMD. There may have been a bleed, seen as a dark red, well defined patch in the macular area. Late in the disease, a macular scar may develop: a thick yellow patch over the macular area.

• Rule out diabetes
• Type 2 membranoproliferative glomerulonephritis
• Various rare ophthalmic conditions to be ruled out by ophthalmology team

• Slit lamp examination (bio-microscopy) is needed.
• Patients with a suspected neovascular membrane will have fluorescein angiography to assess suitability for treatment.

Refer to a specialist team who may suggest the following:
Maximisation of remaining visual function:

• Refraction (i.e. glasses check at optician)
• Treatment of concurrent pathology where appropriate (ophthalmologist to decide)
• Low visual aid clinic referral
  • Magnifiers for near vision, telescopes for distance vision
  • Large print books, talking tapes etc.
  • Variety of gadgets to help with household tasks

• Reassure them that they will not go totally blind: peripheral vision is preserved.
• Check that still safe to drive and advise them to inform DVLA (document this).

• Royal National Institute for the Blind (RNIB)
• Macular Disease Society
• Macular Degeneration Support Group

Drug Therapy

• Photodynamic therapy (PDT) can be used to obliterate subfoveal neovascular membrane. This is carried out in specialist units in selected cases (only refer if best corrected vision of 6/60 ⁴). It involves intravenous injection of verteporfin which is then activated by an argon laser beam. The activated molecules destroy the vessels but spare the photoreceptors. The treatment has limited success rates and needs to be repeated approximately every three months. In 3% of cases, it can result in a temporary loss of vision.
• Pegaptanib (Macugen™) and ranibizumab - these are new agents thought to be effective in the treatment of wet (neovascular) ARMD via down regulation of vascular endothelial growth factor (VEGF) - and therefore a reduction in accumulation of subretinal serous fluid and associated haemorrhage. They are given as monthly intravitreal injections, and are currently being evaluated by NICE - but are popular in the States where they have shown some promising results. ⁵ There are some concerns about the cardiovascular safety of these anti-VEGF drugs until more research data becomes available.⁶Bevacizumab (a similar drug developed for systemic treatment of colorectal cancer) is cheaper and is used in some areas but good quality research evidence is also lacking.⁶

Surgical

Excision of subfoveal neovascular membranes or repositioning of the macula away from the membranes is being investigated. ²

Serous retinal detachment, haemorrhage (both in exudative ARMD only).

This is a progressive, irreversible disease affecting central vision only.