Estrogens directly affect a wide range of bodily functions, with positive and negative effects depending on the targeted organ.
Estrogen receptors exist in various organs, including the anterior and posterior segment of the eye and lacrimal gland.
Thus, changes in estrogenic activity affect the visual function both centrally (optic nerve) and distally.
Selective Estrogen Receptors Modulators (SERMs) such as tamoxifen and clomiphene act on the estrogen receptors and may exert agonistic or antagonistic activity, depending on the targeted tissue.
In the eye, they have the ability to inhibit the action of estrogens, causing various symptoms.
These include flashing lights (photopsia), color perception changes (dyschromatopsia), increased sensitivity to light (photophobia), images in the visual field, reduced peripheral vision and scotomas.
A rare but serious complication is “tamoxifen retinopathy”, a disturbance which depends on the total cumulative dose of the drug.
It is characterized by bilateral presence of crystalline deposits in the retina with or without macular edema.
Tamoxifen can also induce cataracts.
Aromatase inhibitors (AIs) are a class of drugs, which inhibit the action of the enzyme aromatase, which converts androgens into estrogens.
Thus, AIs suppress estrogen production and are considered potent anti estrogens in the peripheral tissues.
The two types of AIs include irreversible steroidal inhibitors, such as exemestane and non-steroidal inhibitors, such as anastrozole and letrozole.
Ocular side effects occur rarely and are linked to retinal hemorrhage, retinal detachment and disorders in color vision, similar to those caused by SERM’s.
The side effects of SERMs and AI in the eye are dose and time dependent.
It should be noted that, the ocular toxicities of tamoxifen such as macular edema or retinal deposits are often reversible, if the drug is discontinued or the dosage reduced.
But, as with all medicines, every individual’s susceptibility plays also a role, just like the rest of the eye concurrent problems (dry eye, myopia-short sighted, increased intra-ocular pressure) do too.
Therefore, the use of SERMs and AI should be stopped immediately after the occurrence of visual disturbances and a full ophthalmologic monitoring should follow.