Toxic Retinopathies

Question 1

Describe Chloroquine/hydroxychloroquine toxicity?

Answer 1

• Chloroquine is an antimalarial drug
• Hydroxychloroquine is used as immunosuppression for various rheumatological and dermatological conditions
• Have an affinity for pigment - “melanotropic”
• Drug can accumulate in RPE
• Bull’s Eye Maculopathy – classic finding – area of atrophy and central area of sparing – photoreceptor loss in area of atrophy (can be seen by white arrows on OCT scan)
• VF defects
  o Look for clinical appearance, OCT scan, VF, fundus autofluorescence & electrophysiology

Question 2

Describe drug induced crystalline maculopathies?

Answer 2

• Have crystal formations at macula
• Affect on vision is variable: sometimes not affected v much, other times can cause breakdown of RPE & leads to macular cysts causing a loss of vision
• Commonest drug Tamoxifen:
  o Used in treatment in breast cancer
  o Fine crystals form in inner retinal layers
  o May lead to macular cysts & loss of vision
• Other drugs:
  o Canthaxanthin – drug used for tanning, ↑pigmentation – so can be a risk of people using sunbeds
  o Nitrofurantoin – anti-biotic used for treatment of urinary tract infections
• Other causes:
  o Bietti crystalline dystrophy
  o Cystinosis (Corneal & macular crystals)
  o Gyrate atrophy
  o Sjogren-Larsson Syndrome