Managing Medications

What ECPs can do to treat and help prevent adverse ocular drug reactions

We define healthy sight as the enhancement of everyday quality of vision and the preservation of long-term ocular health—simply put, seeing well now and into the future.

If, as eyecare professionals, you want patients to have healthy sight and the best possible vision, then an integrated approach is needed—considering both preventive and maintenance eyecare and raising awareness with the eyecare and health care community as well as with the patient.

Maximizing visual function depends on better understanding of how both the patient's overall health and visual optics translate into better visual function. We have to understand that the eyes are part of the body and that ocular disease and use of medications and nutritional products can impact general health as well as eye health.

MEDICATIONS ON THE RISE

People are taking more medications than ever before. In the non-prescription arena, approximately 90 percent of patients presenting for eye examination take some form of systemic medication, herbal, or nutritional supplement.

In 2002, 61 percent of the population under age 65 incurred a prescription drug expense. This increases to 91 percent among those 65 years and older.

The eye, due to its rich blood supply and relatively small mass, exhibits a susceptibility to drugs and toxic agents. Considering the vast array of drugs commonly being taken, there is high potential for vision- and eye-related health consequences.

OCULAR SIDE EFFECTS

A host of medications have been associated with adverse ocular drug reactions (AODRs), with side effects ranging from mild, transient, reversible, and clinically insignificant to vision threatening.

With ocular side effects, a causal connection between specific medications and their effects on specific ocular structures is not necessarily proven, and may not be obvious in some cases. Still, eyecare professionals need to pay great attention to the medications patients are taking to determine if they could adversely affect vision.

It may not be possible for eyecare practitioners to be familiar with all the potential ocular side effects of every drug. It is, however, clinically relevant to be alert to the potential role of medications in contributing to unusual visual or ocular complaints of patients.

OCULAR EFFECT CATEGORIES

Faced with the complexity and diversity of adverse reactions, it is helpful to classify adverse ocular effects into three basic categories. (See the box "MEDICATIONS AFFECTING…" below for examples of each.)

1. QUANTITY. This group includes effects that produce a change in the quantity of vision, such as blurriness, altered refractive states, or accommodative dysfunction.

Over 200 drugs/products can paralyze or decrease accommodation. For example, diuretics have been implicated with myopic shift; beta-blockers have been associated with diplopia.

2. QUALITY. The second category alters the quality of vision by inducing glare, increasing light sensitivity, or impairing light-dark adaptation. Drugs associated with these effects include photosensitizers, mydriatics, cyclopegics, and miotics.

3. DISORDERS. This group includes effects that may contribute to the development of ocular disorders such as cataracts, keratopathies, retinopathies, maculopathies, optic neuropathies, and glaucoma.

The effects of drugs in this group typically are long-term, and are potentially more serious, posing a greater threat to vision. However, their progression can usually be prevented or limited if the disorders are recognized early and the offending agent is discontinued or reduced.

ROLE OF UV

Ultraviolet radiation (UVR) can also have an impact on vision quantity and quality. There is also a growing body of experimental and epidemiological evidence connecting chronic UVR exposure with the development of vision-threatening ocular disorders, such as cataracts.

Medications that either dilate the pupil, thereby increasing the amount of UVR entering the eye, or amplify the effects of UVR on the eye (photosensitizers) can increase the risk for the development of UVR-related eye disease.

■ LIGHT SENSITIVITY. Medications can change pupil size, thereby varying the eye's light sensitivity. Under normal conditions, the amount of light entering the eye is controlled by a delicate balance of activity between the dilator and the sphincter muscles.

By acting directly on these muscles, or by altering the activity of autonomic nerves, certain drugs, chemicals, and herbal products can influence pupil size and function.

Mydriasis, or excessive pupil dilatation, can be caused by both topical and systemic agents. In fact, more than 300 systemic agents—many in common use—have been reported to cause mydriasis.

Drugs with pupillary dilation include those that either stimulate or depress the central nervous system, anticholinergic agents, antihistamines for allergy, antibiotics, and antidepressants. Prolonged dilation of the pupils causes light sensitivity and can result in ocular phototoxic effects.

Atropine is used to prevent progression of myopia and as an alternative treatment to patching for amblyopia. It can produce sustained pupillary dilation for the duration of therapy.

■ GLARE. Photophobia or glare is the other important element in quality of vision.

The anticonvulsants Dilantin and Tegretol have been associated with glare, and CV agents—beta-blockers, antiarrhythmics—have been reported as causing photophobia. According to Darzins et al (Ophthalmology, 1997), patients with age-related macular degeneration (AMD) have a higher sun sensitivity index than a similar control group. They also observed a positive correlation with glare sensitivity in adulthood and AMD.

Other examples of patients who are likely sensitive to light include those with migraines or dry eye.

■ PHOTOSENSITIZING AGENTS. UV radiation can affect anterior ocular tissues like the cornea and lens. In the lens, for example, exposed components like lens proteins can be photosensitized by bound drug molecules following exposure to UV radiation.

The adult crystalline lens normally filters most UV radiation, but in aphakic and pseudophakic patients, UV can penetrate. In these patients there is a risk to the retina where drug molecules can potentially bind and be photoactivated by UV radiation.

■ PHOTOSENSITIZING DRUGS. Of special concern are drugs that might increase UVR damage to the eye. These are called photosensitizers, and they bind to body tissues, increasing UVR absorption at the molecular level.

Well-documented photosensitizers include chloroquine (Pacquenil), phenothiazines, allopurinol, and amiodarone/Cordarone, which has a tendency to store lipids in the cornea and lens and induces lens changes. Visual acuity may not be affected, but glare, halos, and foggy vision are patient complaints. A UV blocker should be prescribed.

Certain other cardiac/antihypertensive drugs, antidepressants, erectile dysfunction agents, and oral contraceptives have also been implicated.

NSAIDs (ibuprofen, etc.) used by patients have been associated with complaints of light sensitivity, and it has been reported that with prolonged use, RPE or retinal changes can occur.

Of particular importance are the verteporfins, which are becoming increasingly popular in photodynamic therapy for age-related macular degeneration.

Because of the increased susceptibility to potential adverse effects of UVR in patients using these medications, the prescription of UVR-protective eyeglasses is mandatory.

DRUGS AND OCULAR DISEASE

Many topical and systemic medications have been implicated in increasing the risk of ocular conditions and disease.

Probably the most widely recognized relationship between medication use and eye disease is that between steroid use and cataract.

Etiology is not well understood, but steroids may interact with amino groups of the crystalline lens fibers, causing protein complexes to aggregate.

Other drugs implicated in ocular diseases include:

■ Antiarrhythmic agents: keratopathy, optic neuropathy

■ Antineoplastic agents: keratitis, scleritis, color blindness, internal ophthalmoplegia, retinopathy, papilledema, maculopathy, dry eyes, cataract, glaucoma, optic neuritis, and blepharitis

■ Antipsychotics: cataracts, keratopathy

■ Bisphosphonates: conjunctivitis, scleritis, uveitis

■ Corticosteroids: cataracts, glaucoma

■ Dermatologic agents (isotretinoin): keratopathy, dry eye, optic neuritis, night blindness, and blepharo-conjunctivitis

■ HIV/AIDS-related agents: night blindness, retinal detachment, glaucoma, cataract, maculopathy, retinopathy, optic neuritis, and conjunctivitis

CATARACTS AND AMD

Photosensitizing drugs and prolonged light exposure can alter lens proteins and lead to cataract formation. Extended exposure to the sun, aphakia, and pseudophakia increase retinal pigment and incidence of early AMD.

REDUCED TEARING

Diverse groups of drugs with varying levels of anticholinergic effects cause reduced aqueous production.

The first generation antihistamines for allergy (older, not newer) are worse for drying. H-2 antihistamines (used for acid reflux) and antihistamines for nausea usually cause less drying than the allergy drugs. Certain beta-blockers, as well as niacin (used to lower cholesterol) have also been associated with dry eyes.

VISION WEAR

The right vision wear can play a role in both minimizing disturbing visual effects of certain drugs, such as photosensitivity, and decreasing the long-term threat of drug-related ocular disease (such as UV damage).

For example, AR, fixed-tint, polarized, and photochromic lens treatments are all valuable options that can be incorporated into the customized eyeglass prescription to effectively address the potential adverse ocular effects of medication.

It is also important to ensure lenses block 100 percent of harmful UV. Most photochromic lenses in particular can provide 100 percent blockage from ultraviolet radiation A and B, and titrate light on demand, promoting good sight and healthy vision. EB