From the Guidelines
Bull's eye maculopathy is primarily caused by hydroxychloroquine (HCQ) and chloroquine (CQ) toxicity.
Causes of Bull's Eye Maculopathy
- Hydroxychloroquine and Chloroquine Toxicity: The mechanism of CQ and HCQ toxicity is not well understood, but it is believed that binding to melanin in the retinal pigment epithelium (RPE) may contribute to or prolong their toxic effects 1.
- Photoreceptor Damage: The primary damage is to the photoreceptors, and as the outer nuclear layer degenerates, there is secondarily disruption of the RPE 1.
- Light Absorption or Cone Metabolism: The macular localization of the disease suggests that light absorption or possibly cone metabolism may play a role, but this is speculative 1.
Key Points
- HCQ and CQ retinopathy can progress even after the drugs are stopped, although the amount of progression and the risk to vision are functions of the severity of retinopathy at the time it is detected 1.
- Early detection of retinopathy is crucial to prevent progression and visual loss, and modern retinal scanning techniques can detect damage much earlier than visible changes on an ophthalmoscope 1.
- The clinical picture of HCQ and CQ toxicity is characterized by a bilateral bull’s-eye maculopathy, but this "textbook" pattern should no longer be seen with recommended screening tests 1.
From the Research
Causes of Bull's Eye Maculopathy
The causes of bull's eye maculopathy can be varied and include:
- Systemic medications such as hydroxychloroquine and clofazimine 2, 3
- Methoxsalen-ultraviolet A therapy 2
- Hereditary ataxia, specifically olivopontocerebellar degeneration 4
- Abnormal Bruch's membrane in Alport syndrome 5
- Iron overload in thalassemia major 6
- Central retinal artery occlusion (CRAO) as a retinal disease, which may increase the risk of hydroxychloroquine maculopathy 3
Medication-Induced Bull's Eye Maculopathy
Medications such as hydroxychloroquine can cause retinal toxicity, leading to bull's eye maculopathy 2, 3. The risk of hydroxychloroquine maculopathy may be increased by factors such as body weight, daily dose, duration of treatment, and underlying retinal diseases 3.
Genetic and Hereditary Causes
Bull's eye maculopathy can also be caused by genetic and hereditary factors, such as Alport syndrome 5 and hereditary ataxia 4. In Alport syndrome, the bull's eye maculopathy is thought to result from damage to the Bruch's membrane and overlying retinal pigment epithelium 5.
Other Causes
Other causes of bull's eye maculopathy include iron overload in thalassemia major 6 and central retinal artery occlusion (CRAO) as a retinal disease 3. In the case of thalassemia major, the bull's eye maculopathy is thought to be caused by iron deposition in the retina 6.