Drusen

Drusen are changes seen with age and are described as focal collection of acellular, polymorphous debris seen beneath the retinal pigment epithelium and within Bruch’s membrane. These are visualized on funduscope as pale yellow deposits on the macula and peripheral retina (1).

They are divided according to the size as

• small (<63 µm in diameter)
• medium (63 to 124 µm)
• large (>124 µm) (1)

drusen can also be classified into two main subgroups, either hard or soft

• hard drusen are usually less than 64 µm in diameter, hemispherical structures with well-defined borders
  • tend to be mainly distributed around the equatorial retina
• soft drusen are typically larger in diameter, more irregular and can be heterogeneous in structure and composition
  • found more centrally than hard drusen

Drusen formation increases with age and are associated with AMD, which is the leading cause of irreversible visual loss in the elderly population in the Western world.

One or two small hard drusen (<63 mm in diameter) in the macula (of any eye) is seen in around 90% of white people aged ≥40 years. Progression to advanced AMD in these patients is almost insignificant (2).

• in patients with >8 small hard drusen - the risk of developing large soft drusen and pigmentary changes after 10 years is increased by 2-3 folds
• in patients with large drusens - there is a 6-7 fold increased risk of developing advanced AMD
• in patients with large number of small hard drusen – may progress in to geographic atrophy (2)

Reference:

• (1) Jager RD, Mieler WF, Miller JW. Age-related macular degeneration. N Engl J Med. 2008;358(24):2606-17
• (2) Cook HL, Patel PJ, Tufail A. Age-related macular degeneration: diagnosis and management. Br Med Bull. 2008;85:127-49
• (3) Mullins et al. Drusen associated with aging and age-related macular degeneration contain proteins common to extracellular deposits associated with atherosclerosis, elastosis, amyloidosis, and dense deposit disease. Faseb. J. 14 (7) (2000):835-846.