Introduction:
Medications are usually systemically absorbed, which means they can influence every organ in the body, including the eye. The eye is more sensitive to drug-related side effects due to its abundant blood supply and thin size. Numerous systemic medications include Bisphosphonates, Topiramate, Vigabatrin, Isotretinoin, other retinoids, Amiodarone, Ethambutol, Chloroquine hydroxychloroquine, Tamoxifen, Quetiapine, Cyclo-oxygenase (COX)-2 inhibitors, erectile dysfunction medications, and some herbal remedies may cause eye toxicity. Ocular side effects may be linked to a drug's pharmacodynamic (action of the drug) or pharmacokinetic activity (reaction of the body in relation to the exposure of the drug), perhaps acting as a toxicity signal. It is possible to experience both transient visual abnormalities and permanent eyesight loss. Although there are several ways to lower the risk of vision loss, including monitoring for ocular toxicity, lowering the dosage, or quitting the medication and seeking an alternative.
What Are the Systemic Drugs With Toxic Ophthalmic Reactions?
All the tissues and functions of the eye can be impacted by systemic drug administration, and they may even act as a toxic indicator. It is possible to experience both transient visual abnormalities and irreversible eyesight loss. The most common drugs which induce adverse or toxic ophthalmic reactions are
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Amiodarone.
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Phosphodiesterase inhibitors.
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Bisphosphonates.
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Antiepileptic drug.
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Antimalarial drug.
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Ethambutol.
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Herbs.
1) Amiodarone: Amiodarone is a class III anti-arrhythmic used to treat different arrhythmias. It has been linked to several ocular side effects, the most prevalent of which are
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Corneal Deposits: After one month of treatment with Amiodarone, corneal deposits or keratopathy develops. It is distinguished into three phases. The first phase is forming a horizontal line in the cornea in people taking 200 to 400 mg. Higher dosages can cause phase two and three effects, characterized by a cat-whisker pattern and a whorl-like (verticillate) pattern in the cornea. It might take 3 to 20 months after the withdrawal of Amiodarone to recover from deposits. Colored halos or bright circles of light that encircle headlights and other light sources are also associated with corneal deposits:
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Optic Neuropathy: It occurs less commonly (2 percent), although it can be severe, resulting in vision loss.
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Other Toxic Effects: Irritation of the eyelid, eyelid cysts, and dry eyes linked with Amiodarone therapy. A baseline ophthalmic examination is recommended before starting medication, followed by subsequent examinations every six months for the first year and every 12 months afterward.
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2) Phosphodiesterase Inhibitors: Sildenafil, Vardenafil, and Tadalafil are phosphodiesterase type 5 (PDE5) inhibitors that treat erectile dysfunction by inhibiting cyclic guanosine monophosphate. PDE5 inhibitors have been linked to various ocular side effects, including color perception abnormalities (typically blue or green), blurred vision, changes in light perception, photophobia, and eye inflammation. However, these occurrences have not resulted in long-term changes in perceptions of color.
3) Bisphosphonates: Bisphosphonates (Alendronate, Ibandronate, and Risedronate) treat osteoporosis during postmenopausal and in paget disease. Inflammatory responses caused by bisphosphonates include conjunctivitis (inflammation of the eyeball), uveitis (inflammation of the middle layer in the eye wall or uvea), scleritis (inflammation in the white portion of the eye), episcleritis, and keratitis (corneal inflammation). The majority of conjunctivitis cases resolve on their own. Uveitis is often treated with ocular or systemic medications, and the Bisphosphonate may be discontinued. However, Bisphosphonate can be maintained in episcleritis conditions.
4) Antiepileptic Drug: Vigabatrin and Topiramate are antiepileptic drugs used to treat seizures. Vigabatrin is an antiepileptic medicine that can treat refractory seizures in individuals who have not responded to previous antiepileptic drug treatments. From 30% to 40% of individuals have experienced vision loss due to Vigabatrin medication. On the other hand, Topiramate is used to treat seizures and migraine prophylaxis.
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Acute Angle-closure Glaucoma: Acute angle-closure glaucoma is most likely to occur within the first two weeks after beginning or modifying the Topiramate drug. It manifests as bilateral blurry vision. Topical mydriasis-inducing medications and beta blockers may help reduce intraocular pressure by retracting the ciliary processes.
5) Antimalarial Drug: Hydroxy-chloroquine treats several illnesses, including malaria, systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA). Ophthalmic toxicity is associated with both Chloroquine and Hydroxychloroquine. These medications impact retinal cell metabolism by adhering to melanin in the retinal pigment epithelium. Antimalarial drug toxicity is characterized by bilateral bull's-eye maculopathy. There is currently no cure for hydroxychloroquine-induced retinopathy. Discontinuation may aid in arresting progression, but the impact is irreversible.
6) Ethambutol: Ethambutol is used to treat TB and is also associated with many ocular side effects, the most serious of which is optic neuritis. Color vision alterations and visual-field abnormalities have also been reported as ocular abnormalities. Generally, Ethambutol is eliminated in the kidneys by glomerular filtration and tubular secretion; hence, renal impairment might result in higher drug levels and toxicity. Hence, Individuals with additional ocular risk factors, such as renal insufficiency, should be examined periodically.
6) Herbs: Herbal supplements have also been linked to ocular side effects. The common herbs with toxic effects are
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Niacin: 1.5g of niacin reduces cholesterol. However, it causes cystoid macular edema (thickening of the retina). However, the edema usually disappears after two weeks of stopping the medication. Additionally, it is also reported that clouded vision is a result of niacin usage.
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Chamomile: It can produce acute conjunctivitis and angioedema, most likely owing to sensitivity to allergens in chamomile.
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Echinacea: It is taken orally to stimulate the immune system and might induce eye irritation and conjunctivitis. Symptoms resolve within a day of discontinuing usage.
How to Manage Ocular Toxicity?
Certain ocular side effects or toxicity, such as increased intraocular pressure, are treatable with medication or laser treatment. Some ocular adverse effects like macular atrophy (age-related retinal damage) might result in irreversible vision loss, emphasizing the importance of screening for damage at an early stage. The other management of ocular toxicity involves
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Screening before therapy
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Monitoring for ocular toxicity.
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Lowering medication dosages.
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Withdrawing the medicine.
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Investigating an alternative drug.
Conclusion:
Oral medications that are commonly used can have ocular side effects. In addition to retinal toxicity, oral medications can harm other eye elements, such as the cornea, lens, and optic nerve. Drugs should always be considered a potential cause of unexplained eye problems. Ophthalmologist is positioned to highlight the possibility of ocular toxicity with systemically administered drugs and to emphasize the significance of frequent monitoring and follow-up for adverse visual effects.
