Which category of drugs is linked with dry eyes and an increased risk of retinal vein occlusions such as CRVO and BRVO?

• A. Estrogen agonists (oral contraceptives)
• B. Tamoxifen (Nolvadex)
• C. Topiramate (Topamax)
• D. Phenytoin (Dilantin)

Answer: (A)

Estrogen-containing medications raise the risk of retinal vein occlusions by creating a prothrombotic state. Estrogen increases hepatic production of coagulation factors and reduces certain anticoagulant pathways, tipping the balance toward clot formation. Retinal vein occlusions, such as central or branch retinal vein occlusion, can occur when thrombi form in the retinal venous system, especially in the presence of other vascular risk factors. At the same time, hormonal effects from estrogens can influence the ocular surface, leading to tear film instability and dry eye symptoms in some patients. This combination explains why this drug category is linked to both dry eyes and an increased risk of CRVO and BRVO.

Other listed drugs have different ocular or systemic profiles. Tamoxifen can cause retinal toxicity with crystalline deposits and cystoid macular edema but isn’t a classic driver of retinal vein occlusion; topiramate is more associated with acute angle-closure glaucoma and myopic shifts; phenytoin can cause nystagmus and diplopia but not specifically dry eye or retinal vein occlusion risk.