Novel ERG for Detection of Hydroxychloroquine Retinopathy

Inclusion Criteria: 1. Age ≥18 years 2. HCQ groups: a. HCQ use \>5 years for patients without any high-risk factors, or \>1 year in patients with one or more high-risk factors for HCQ retinopathy, namely: i. Dose \>5mg/kg per day actual body weight (ABW) ii. Estimated glomerular filtration rate (eGFR) of \<60mls/min/1.73m2 iii. Concomitant tamoxifen use 3. Control group: 1. No prior HCQ exposure Exclusion Criteria: 1. Cataract grade ≥3 of any subtype 2. Recent cataract surgery within 4 weeks of recruitment 3. Significant media opacity or corneal disease including, but not limited to, corneal oedema, corneal scarring, keratoconus, previous corneal transplants, severe keratoconjunctivitis sicca (requiring the use of topical serum, immunosuppressive or analogous therapy, or procedural treatment). 4. Significant macular co-pathology including, but not limited to, macular degeneration, macular scarring, cystic macular oedema (for any reason), staphyloma. 5. Inherited retinal and/or macular dystrophies including colour vision deficiencies 6. Active or previous posterior uveitis or pan-uveitis 7. Aphakia 8. High refractive error \>6.00 dioptres 9. Amblyopia 10. Diabetes 11. Retinal angiopathies including, but no limited to, retinal vein occlusion, retinal artery occlusion, ocular ischaemic syndrome, HIV retinopathy, Sickle cell disease, radiation retinopathy 12. Visually significant surgical retinal disease including epiretinal membrane, macular hole, retinal detachment, retinal tear 13. Previous retinal laser or intravitreal treatment 14. Moderate or worse glaucoma 15. Optic atrophy 16. Photosensitive epilepsy 17. Ungradable HCQ retinopathy screening images 18. Periocular infection or rash (recruitment can be deferred until acute pathology has resolved) 19. Unable or unwilling to undertake study activities 20. Any active use or history of the following medications: Amiodarone Canthaxanthin Deferoxamine Digoxin Ethambutol Interferon-alpha Melatonin Nefazodone Sildenafil Vigabatrin Chloroquine Quinine