Medications That Affect Your Eyes (& How)

All medications are accompanied by side effects, some of which can be particularly severe and even result in permanent symptoms to other parts of the body. Medications are intended to treat specific symptoms associated with a medical condition, but because the body functions as a holistic, dynamic, and interrelated system, it is not always possible to medically treat one specific area of the body via medication without affecting others. 

There are numerous medications that can potentially affect the eyes, particularly when they are taken in combination with one another. Some of these effects may not be detectable for long periods of time after taking the medication or even after ceasing to take the medication. 

These can include medications that are directly intended to treat conditions of the eye, as well as those that are not intended to treat the eye. Instead, they affect the eye indirectly. 

Make sure to consult with your doctor before taking any medication and ensure that you disclose any other medications or supplements you are taking due to potential interactions. It is common to believe that taking supplements and over-the-counter medications does not have significant side effects or risk factors. However, many substances (even nutritional supplements) can interact with other medications and have unforeseen impacts on your body, including the eyes. 

Additionally, alcohol can interact with these medications acutely and chronically, causing damage to the functioning and structure of the eye. 

Different Classes of Medications That Can Affect the Eyes

The number of medications and supplements that can affect your eyes is incredibly large. These medications can be divided by their class and function. 

Classes of medications that can affect the eyes include the following:

High Blood Pressure Medication

Medications used to treat high blood pressure are intended to improve blood flow in various ways, such as increasing the diameter of blood vessels or removing blockages over time. These medications have their own subclasses, including these:

• Diuretics: These drugs are designed to lower salt and water in the bloodstream and reduce fluid channeling through the arteries and veins. Diuretics can affect the eyes by causing eye dryness, though this effect is temporary.
  
• Beta blockers: These are medications that block the hormone epinephrine and cause the heart to beat more slowly and with less force. Beta blockers can reduce the production of fluid in the eyes and lower pressure. This can lead to blurred vision. This effect is temporary and improves when the drugs are no longer taken.
  
• Alpha-2 receptor agonists: These drugs are designed to inhibit alpha 2 receptors in the brain stem and reduce sympathetic nervous system activity. These medications are sometimes used to control intraocular pressure in cases of glaucoma. They have positive, neuroprotective effects.
  
• Combined alpha and beta-blockers: This combination of alpha and beta blockers causes binding of alpha-1 and beta receptors, which prevents their stimulation and leads to a dilation of the blood vessels. This combination of medications has the same type of effect on the eyes as beta blockers.
  
• Calcium channel blockers: These drugs prevent calcium from entering the cells of the arteries and heart, which can relax and dilate blood vessels. These drugs can dilate isolated ocular vessels and increase the risk of glaucoma.
  
• ACE inhibitors: These medications relax the veins and arteries by preventing an enzyme from producing angiotensin II, which restricts the blood vessels. These drugs can lead to reductions in vision, conjunctivitis, and photophobia. In rare cases, ACE inhibitors can lead to retinal hemorrhaging, or internal bleeding of the retina.

Antidepressants

Antidepressants are medications that are used to treat chronic depression through inhibiting the uptake of mood-affecting neurochemicals in the brain and allowing for their more free-flowing availability. This increases the availability of neurotransmitters to regulate positive emotions, but not their actual production. 

Antidepressants also have their own sub-classes, including these:

• Selective serotonin reuptake inhibitors: These medications inhibit the reabsorption of serotonin in the neurons and increase their (temporary) availability. These drugs can lead to dryness of the eyes and affect the ocular muscles.
  
• Serotonin and norepinephrine reuptake inhibitors: These medications combine to inhibit the reuptake of serotonin and norepinephrine and increase their availability for use as neurotransmitters to regulate mood. These medications can affect pupil and ciliary muscle function in the eye, leading to blurred vision and difficulty focusing on near objects.
  
• Atypical antidepressants: These medications do not fall under any of the main classes of antidepressants and do not function by inhibiting neurotransmitter reabsorption. They can affect the eyes in a range of ways, depending on their function.
  
• Tricyclic antidepressants: These medications work to block the reuptake of neurotransmitters specifically in the presynaptic terminals, thereby increasing their concentration in the synaptic cleft. Tricyclic antidepressants can affect the eyes in similar ways as typical antidepressants.
  
• Monoamine oxidase inhibitors: These medications inhibit the activity of monoamine oxidase, which allows the accumulation of norepinephrine and serotonin in the brain. These medications also have similar potential effects on the eyes as serotonin and norepinephrine reuptake inhibitors.

Cholesterol-Lowering Drugs

Cholesterol-lowering drugs are designed to reduce the production or accumulation of cholesterol in your heart, liver, or within the arteries in various ways. The following are examples:

• Statins: These are medications that reduce low-density lipoprotein (LDL) cholesterol by facilitating the liver’s functionality and also reduce inflammation in the arterial walls. Statins may increase the risk of cataracts because of the bidirectional effects on oxidation.
   
• PCSK9 inhibitors: These drugs block PCSK9 proteins from breaking down LDL receptors, which can help reduce this type of cholesterol more effectively. The mechanism by which this affects the eyes is unknown, though some research has found correlations between the use of these medications and ocular side effects.
  
• Fibric acid derivatives: These medications reduce the amount of very-low-density lipoprotein (VLDL) the liver produces and lowers triglyceride levels. Fibrates can have positive effects on the eyes, such as controlling diabetic eye disease.
  
• Bile acid sequestrants: These drugs block bile acid in the stomach from being absorbed into the blood, requiring the liver to extract more cholesterol from the blood to make bile acid. Bile acid sequestrants can affect every structural layer of the eye, though the mechanism by which this occurs is not yet fully understood.
  
• Nicotinic acid: This acid reduces the production of triglycerides and VLDL. This acid has been linked with blurred vision, proptosis, loss of eyelashes and eyebrows, eyelid edema, toxic amblyopia, and superficial punctate keratitis.
  
• Selective cholesterol inhibitors: This class of medications helps the body inhibit the uptake of cholesterol from the intestines. These medications can affect the eyes in similar ways as statins.
  
• Omega-3 fatty acids and fatty acid esters: These fatty acids may improve the amount of high-density lipoprotein (HDL) by inhibiting the synthesis of VLDL cholesterol and triglycerides in the liver. They can improve the eye’s oil film produced in the glands of the eyelid, thus reducing the need to produce tears.

Antihistamines

Antihistamines are commonly used to treat allergies. They work by blocking histamine in the body, which is typically produced when a harmful external agent is detected. This causes the blood vessels to expand, leading to inflammation of the epidermis and providing protection to the body. These medications can diminish the aqueous layer in the tear film and reduce eye moisture. 

There are two main classes of antihistamines:

• H-1 receptor antagonists
• H-1 blockers

Both can have this effect on the eyes, so always consult with your doctor before taking an over-the-counter antihistamine, such as Benadryl, because of its potential to interact with other medications. There are 414 drugs that are known to interact specifically with Benadryl.

Reproductive & Sexual Health Medications

Some reproductive and sexual health medications can affect the eyes. Two examples are birth control pills and erectile dysfunction medications. 

• Birth control pills: These drugs prevent sperm from joining with the egg after sexual activity. They can potentially cause ocular complications. Approximately 1 in 230,000 women experience such complications, which can consist of corneal disturbance, vascular complications, retinal-neuro-ophthalmologic complications, lens opacities, and dry eyes.
  
• Erectile dysfunction medications: These drugs work by enhancing the effect of nitric oxide, which can relax muscles in the penis. Erectile dysfunction medications can cause blurred vision as well as increase the risk of retinal detachment. Some reports of individuals who take the erectile dysfunction medication sildenafil (Viagra) include bluish vision and increases in the brightness of lights.

Xenobiotics

Xenobiotics are chemical substances found within an organism that are not naturally produced by that organism. These substances can be used medically to bio-transform polar compounds, which is called drug metabolism. This is used to modify the structure of a native protein. 

Some nutritional supplements fall under the category of xenobiotics. If complications caused by xenobiotics are not addressed, they can lead to issues like ocular toxicity and retinal photodamage.

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How to Manage Effects on the Eyes

While no medication is without the potential for side effects, you can limit issues by communicating with your doctor at every step. Before you are prescribed or use any medication, confirm your doctor is aware of any medications you already take as well as any pre-existing eye issues.

If you notice any eye or vision issues after starting a medication, contact your doctor promptly. They may switch you to another medication.

References

1. Benadryl Interactions. (December 2022). Drugs.com. 

2. The Impacts of Combined Oral Contraceptives on Ocular Tissues. (October 2018). International Ophthalmology.

3. Ocular Effects of Niacin: A Review of Literature. (2015). Medical Hypothesis, Discovery & Innovation Ophthalmology Journal.

4. Ocular Toxicity from Systemically Administered Xenobiotics. (October 2021). Expert Opinion on Drug Metabolism & Toxicology.

5. Retinal Photodamage by Endogenous and Xenobiotic Agents. (November-December 2012). Photochemistry and Photobiology.

6. Viagra (Sildenafil Citrate) and Ophthalmology. (September 2002). Progress in Retinal and Eye Research.

7. The Ocular Adverse Effects of Oral Drugs. (August 2021). Australian Prescriber.

8. A Review of Ocular Complications Associated with Medications Used for Anxiety, Depression, and Stress. (February 2022). Clinical Ophthalmology.

9. VLDL Cholesterol. National Library of Medicine.