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Key Points

• Both chloroquine and hydroxychloroquine are thought to interfere with the way the malaria virus breaks down haemoglobin into its constituent protein unit and heme unit, and have historically been used in the treatment of malaria.
  
• Chloroquine and hydroxychloroquine are also found to have an impact on inflammatory disease by a number of different processes and in recent years their use in the treatment of rheumatoid arthritis, systemic lupus erythematosus (SLE) and discoid lupus erythematosus (DLE) has increased. They are mainly prescribed by dermatologists or rheumatologists and tend to be used as long-term therapy.
  
• The drugs are preferred to alternatives such as the long-term use of steroids or immunosuppressant drugs, both of which have significant adverse side effects.
  
• Both drugs are known to cause adverse ocular effects, the most serious being sight loss through maculopathy, though this is less marked with hydroxychloroquine use than chloroquine use. Other (non-retinal) effects have been noted including blurred vision, headache, accommodative dysfunction and a vortex keratopathy.
  
• Age of the patient and the duration of drug use correlate with the risk of adverse ocular effects.
  
• In 2018, the RCO published guidelines suggesting that retinal screening is undertaken annually whenever chloroquine is taken for one year or hydroxychloroquine for five years.
  
• Screening should include fundus photography (with wide-field autofluorescence) and spectral domain OCT, with a Humphrey 10-2 field test when maculopathy is suspected and, currently, should be carried out within the hospital eye service.