Summary
Cataract has been associated with several systemic diseases, importantly diabetes mellitus, myotonic dystrophy, atopic dermatitis and neurofibromatosis type 2. Many of these cataracts have unique, characteristic patterns.
Summarised below are the salient learning points regarding cataracts associated with systemic disease.
Diabetes mellitus
Pathophysiology
- Hyperglycaemia results in a high glucose level in the aqueous humour, which diffuses into the lens
- Glycosylation of lens proteins causes over-dehydration
- Vacuoles of cortical fluid develop, which opacity over time
Cataract features
- ‘Snowflake’ pattern ******- appear as grey-white subcapsular opacities. These cataracts can grow rapidly with the entire lens turning white. These are rare and typically occur in the young
- Age-related cataracts develop at a younger age in diabetes mellitus
Image showing bilateral posterior subcapsular ‘snowflake’ cataracts in a diabetic patient. Image courtesy of Park.
Myotonic dystrophy
Cataract features
- ‘Christmas tree’ pattern - bilateral iridescent needle-shaped cortical opacities. 90% of patients with myotonic dystrophy develop these in their 30’s.
- These grow over time into wedge-shaped or ‘star-like’ cortical and subcapsular opacities by their 50’s.
Image showing a ‘Christmas tree’ cataract. Note the reticular network of colourful needle-shaped opacities. Image courtesy of Zahir and Tahri.