Pneumocystis jirovecii choroiditis

This is now uncommon, as a result of the use of ART or systemic prophylactic therapy to prevent Toxoplasma infection. The choroiditis is typically bilateral, comprising yellow choroidal patches of 1/4 to 2-disc diameters in size around the posterior pole, with minimal vitritis. It is often asymptomatic. Treatment is with trimethoprim/sulfamethoxazole, clindamycin/primaquine or pentamidine.

Cryptococcus choroiditis

This rare condition is usually associated with cryptococcal meningitis and may be associated with an optic neuropathy or papilloedema. It is characterized by multifocal off-white choroidal lesions, occasionally with a retinitis or endophthalmitis. Treatment is as for cryptococcal meningitis with induction therapy using an antifungal agent, such as amphotericin, followed by consolidation with fluconazole.

HIV retinopathy

HIV microvasculopathy is seen most frequently in HIV patients who are ART-naïve and with high HIV viral loads. HIV targets retinal vascular endothelium resulting in microvascular abnormalities such as microaneurysms, intraretinal microvascular abnormalities and most characteristically cotton wool spots. These are infarcts within the superficial retinal capillary plexus that result in stasis of axoplasmic flow in axons in the retinal nerve fibre layer that swell and become opaque and visible. They resolve over 6-8 weeks with return of normal axon function. Rarely, patients affected by HIV microvasculopathy can develop significant retinal ischaemia, which can result in vision loss.

Sometimes it can be difficult clinically to differentiate early CMV retinitis from cotton wool spots. Serial observation over an interval of 4-6 weeks will resolve this uncertainty. CMV lesions will enlarge, while cotton wool spots will either remain unchanged or begin to resolve. Imaging studies can be valuable at determining this.