Intraretinal refractile deposits.
If crystals are intravascular and cause capillary nonperfusion, peripheral neovascularization as well as neovascularization of the optic nerve can develop (most commonly with talc). ME, macular pucker, and VH may also occur. Dermatologic examination may reveal evidence of intravenous drug abuse.
Canthaxanthin toxicity: Oral tanning agent causing ring-shaped deposits in the superficial retina. Generally asymptomatic and usually resolves over many years when the drug is stopped. Usually requires a total of 19 g over 2 years. Crystals appear more prominent in eyes with pre-existing retinal disease and patients taking beta-carotene.
Tamoxifen: Used in patients with hormone receptor-positive breast cancer. Toxicity usually requires 7.7 g total. Crystals appear in the inner retina usually around the macula and may cause ME. Vision may improve with discontinuation of drug, but crystals remain. Asymptomatic patients taking tamoxifen do not need to be screened. Consider medication change if evidence of toxicity in consultation with patient’s oncologist.
Retinal arterial emboli: Seen within vessel. See 11.6, Central Retinal Artery Occlusion and 11.7, Branch Retinal Artery Occlusion.
Talc: Red-yellow refractile particles seen intravascularly in intravenous drug users. Usually requires chronic IV drug use over several months to years before retinopathy develops.
Methoxyflurane: An inhalational anesthetic agent. Calcium oxalate crystals deposited throughout the body can lead to irreversible renal failure. Crystals seen in both the RPE and inner retina.
Bietti crystalline dystrophy: Crystals of unknown composition in the peripheral corneal stroma and in the retina at different layers. See 11.28, Retinitis Pigmentosa and Inherited Chorioretinal Dystrophies.
Idiopathic juxtafoveal/parafoveal telangiectasis: Telangiectasis of juxtafoveal or parafoveal retinal capillaries leading to exudation and deposition of crystals on the ILM. The temporal perifoveal area may exhibit grayish discoloration. Patients can develop ME and/or CNV. Disease progression can lead to cystic retinal changes or even macular hole.
Other: Nitrofurantoin toxicity, Sjögren–Larsson syndrome, West-African crystalline maculopathy, chronic RD, among others.
Complete past medical and medication history: Intravenous drug use? Cardiovascular risk factors such as HTN, elevated cholesterol? Breast cancer? Use of oral tanning agents? History of anesthesia in patient with renal failure?
Complete ocular examination, including dilated fundus evaluation using a slit lamp and a handheld lens along with indirect ophthalmoscopy. Carefully assess the location, depth, color, and morphology of crystals as well as the potential presence of ME, neovascularization of the disc and peripheral retina, or retinal infarction. Examine the cornea for crystals.
Consider carotid Doppler US and echocardiography in older patients and those with cardiovascular risk factors.
Dermatologic examination patient for evidence of intravenous drug abuse.
Consider testing for diabetes if idiopathic juxtafoveal/parafoveal telangiectasis suspected.
IVFA may be helpful to demonstrate areas of nonperfusion distal to an intravascular crystal. OCT may be helpful to determine depth.
Stop tamoxifen or canthaxanthin use if responsible for toxicity.
If cholesterol, calcium, or fibrin-platelet emboli, see 10.22, Transient Visual Loss/Amaurosis Fugax,11.6, Central Retinal Artery Occlusion, and 11.7, Branch Retinal Artery Occlusion.
If there is peripheral nonperfusion or neovascularization, consider PRP or anti-VEGF agents. Visual loss may be permanent if there has been vascular nonperfusion in the macula secondary to blockage from intraretinal crystals.