Canthaxanthin is a naturally occurring chemical, which is most commonly utilized as a colorant for food and dyes or a skin bronzing agent. Its most prevalent impact on human health is canthaxanthin retinopathy, which appears as birefringent, yellow to red crystals surrounding the macula. This occurs with increasing, dose-dependent exposure. Generally, patients remain asymptomatic and findings may only be evident on funduscopic examination. Cessation of canthaxanthin ingestion appears to reverse the retinopathy, but the time until crystal disappearance is variable. Despite a usually favorable outcome, long-standing visual changes may occur. We report a case of an 84-year-old woman with significant visual loss secondary to canthaxanthin retinopathy that ultimately improved upon cessation of the drug.
Canthaxanthin is a naturally occurring carotenoid pigment which is synthesized by microorganisms and plants. It can be found in fruits, vegetables, and fish and primarily occurs in human tissue as a result of dietary ingestion. Like other carotenoids, it is fat-soluble and intensely colored. Canthaxanthin carries a red to orange hue and is used as an agent for coloring foods, dyes, and for skin bronzing. Experimental use has been successful for photoprotection for erythropoietic protoporphyria and cosmetic improvement in vitiligo [
An 84-year-old woman presented with a two-month history of worsening vision in both eyes. She had a 10-year history of canthaxanthin use for tanning, at variable dosages. Estimated total dosage is greater than 100 g. She had undergone bilateral cataract extractions in the past and had no other known ocular diseases. Visual acuity was 20/200 OD and 20/300 OS. Funduscopic examination demonstrated bilateral macular pigmentary changes and gold crystalline deposits (Figure
Fundus photographs of an 84-year-old woman showing diffuse canthaxanthin crystal deposition. (a) Right eye. (b) Left eye.
Late phase fluorescein angiogram of an 84-year-old woman with canthaxanthin retinopathy showing bull’s eye pattern of central hypofluorescence. (a) Right eye. (b) Left eye.
Optical coherence tomography of an 84-year-old woman with canthaxanthin retinopathy showing a thin retina with no edema, crystals, or shadowing artifacts. (a) Right eye. (b) Left eye.
Canthaxanthin and other carotenoids locate in biological lipid membranes and based on their orientation and location can influence membrane properties such as permeability and fluidity. They are powerful antioxidants due to their radical scavenging and singlet oxygen-quenching properties [
Incidence and prevalence are difficult to predict due to the generally asymptomatic course of canthaxanthin retinopathy. Some reports state an incidence between 12 and 14% [
Funduscopic examination generally reveals highly reflective, tiny (30
The present case, to our knowledge, represents the oldest reported patient with canthaxanthin retinopathy. Also relatively unique to this case is the severe decrease in visual acuity. Such a complication is likely related to the large total ingested dose compounded by the patient’s age, similar to other drug-related retinopathies such as that associated with hydroxychloroquine [
Differential diagnosis for canthaxanthin retinopathy includes other crystalline disorders such as tamoxifen, methoxyflurane, and talc retinopathy. Primary ocular disorders such as Bietti’s crystalline retinopathy, calcified macular drusen, and idiopathic parafoveal telangiectasis are other possibilities. Crystals on the inner retinal surface in the setting of longstanding retinal detachment have also been reported, although the pathophysiology of this finding has not been fully elucidated [
Treatment for canthaxanthin retinopathy is immediate discontinuation of the drug as soon as crystals are identified, even if the patient is asymptomatic. Prognosis is very good with complete recovery occurring in the vast majority of patients. Hueber et al. [
In summary, canthaxanthin retinal crystal deposition is a very common finding in patients with prolonged use of the drug. Symptomatic visual loss is less common and correlates with total dosage and possibly patient age. Even with profound visual loss, prognosis for improvement is very good with recognition and discontinuation of the drug.