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Mr. L is an 85-year-old Caucasian man who lives with his daughter in a three-story home. He complains that he has had increasing difficulty with his vision over the past year. He has trouble reading and seeing faces when people are speaking to him. His daughter pays his bills and pre-pours his medication, as he can no longer reliably read small print. He denies eye pain, headache, and sudden vision loss. He gave up driving 6 months ago because he couldn’t see the road signs.

Mr. L underwent successful bilateral cataract surgeries several years ago. He has been treated for chronic glaucoma with eye drops, but intraocular pressure has been normal, as measured by the ophthalmologist 6 months ago. He has no history of diabetes mellitus, but is being treated for “blad- der problems” and hypertension. His medications include oxybutynin and losartan. He also takes eye drops, which he cannot name, and a regimen of antioxidant vitamins prescribed by his ophthalmologist. Mr. L has fallen several times at home, often while trying to get to the bathroom at night. His daughter is quite concerned because her father insists on walking outside unaccompanied and without using his cane. She is afraid that Mr. L may have a serious fall and injure himself.

Questions

1. What eye diseases could be causing this patient’s poor vision? 2. How can his condition be managed?

3. How might his medications be affecting his vision? His physical function? 4. What can be done to help Mr. L to manage his activities of daily living and

improve his quality of life?

Case Studies in Geriatric Medicine, Judith C. Ahronheim et al. Published by Cambridge University Press. C

5. What environmental changes in the home might decrease the likelihood of falls?

6. What social and psychologic problems can accompany with vision loss?

Answers

1. Low vision is defined as bilateral vision impairment, which significantly impairs the patient’s ability to function and is not amenable to correction with medica- tion, surgery, corrective lenses, or contacts. In the elderly, common disorders that cause gradual, painless vision loss include open angle glaucoma, cataracts, diabetic retinopathy, and age-related macular degeneration (ARMD). Diabetic retinopa- thy is seen in longstanding diabetes; however, undiagnosed diabetes can present with blurred vision due to hyperglycemia and influx of glucose into the lens. This reversible problem occurs when glucose is converted in the lens to sorbitol, lead- ing to hypertonicity, influx of water, and swelling of the lens. Cataract extraction occasionally is accompanied by complications, including macular edema, retinal detachment, and displacement or fracture of the lens implant. Glaucoma can pro- duce visual loss, but peripheral vision is generally lost while central vision is main- tained. Because this patient has had “successful” cataract extractions, and has no history of diabetes mellitus, he most likely has ARMD, which presents with loss of central vision. In Mr. L’s case, fundoscopic examination by his ophthalmologist demonstrated early macular degeneration a few years ago, but symptoms have now progressed.

In elderly patients like Mr. L, more than one eye disease can coexist, and many systemic factors can further affect vision.

ARMD increases in incidence with age and is more often severe in late life. It is more prevalent in nonHispanic whites than in Hispanic or African Americans (in contrast, glaucoma is more common among African Americans). It is caused by degeneration of the macula, the area of the retina responsible for central vision. The hallmarks of ARMD are blurred central vision, image distortion, central sco- toma, and difficulty reading, with patients noting that they rely more heavily on increased light or a magnifier to see small print. Mr. L has difficulty with bill paying and reading medication labels, both of which require sharp central vision. Because peripheral vision is spared, patients can often ambulate without assist- ance and can participate in many activities. Unfortunately, elderly patients may have more than one eye disorder, and physical comorbidities can further impair function.

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ARMD is classified as either “wet” (exudative) or “dry” (nonexudative). Wet ARMD often involves dramatic, sudden loss of vision due to acute macular hemor- rhage associated with the growth of abnormal vessels (“neovasculature”) from the choroidal circulation to the subretinal space. When these friable vessels leak blood or serum in the macula, blurred or distorted central vision results. The exuda- tive form accounts for about 10% of ARMD cases, but for 80–90% of cases with severe vision loss. Dry ARMD is associated with Drusen (“stones”) – yellowish- white accumulations of extracellular debris in the macula that distort and lift the retinal pigment epithelium. Visual loss occurs slowly and patients often can accommodate to this by using good lighting and other strategies. Patients with large or multiple Drusen have an increased risk of developing neovasculature and leaking.

2. There is no treatment that restores vision loss, and treatment options are directed at preventing further vision loss in patients with exudative ARMD. Laser photo- coagulation is used to ablate new vessels to prevent hemorrhage in patients with neovasculature. New leakage may occur over time, necessitating regular follow up examinations, including fluorescein angiography to identify neovasculariza- tion that may respond to additional treatment. In between periodic examination, patients should be instructed to use an Amsler grid, a symmetrical pattern of squares with a central dot, to monitor their vision for any changes (see Figure 8). The Amsler grid is useful as a screening tool in the primary care office and patients can use it at home to monitor their vision for any changes. Any new findings should prompt an immediate visit to the ophthalmologist.

Ablation of new vessels can also be accomplished by photodynamic therapy, which reduces the likelihood of blind spots caused by thermal laser. Other promising options are reviewed in the references (see Fine et al., 2000).

Mr. L’s vitamins are probably antioxidants. These are widely prescribed to retard the progression of ARMD based on the theory that they prevent cellular damage by reacting with free radicals produced during light absorption. A large, randomized, placebo-controlled trial of vitamins C and E, beta-carotene, and zinc modestly reduced progression of ARMD to the advanced stages (Age-Related Eye Disease Study Research Group, 2001), but, to date, there is no evidence that antioxidants prevent the development of this disease.

Because people with light-colored irises have an increased risk of developing ARMD, protective sunglasses have been recommended, but they have not been definitively shown to prevent the disease or its progression. However, their use is prudent because this may decrease development of lens opacities. Likewise, smoking cessation is universally recommended and may reduce the risk of ARMD. 3. Anticholinergic medications such as oxybutynin can precipitate acute angle closure glaucoma, thereby causing rapid vision loss. Although these medications are less

Amsler’s grid

Normal image Patient’s view

Figure 8 Schematic representation of a distortion that might be visualized by a patient with macular degeneration (right) compared with someone with normal vision (left), when utilizing an Amsler grid.

likely to increase intraocular pressure in open angle glaucoma, which Mr. L has, oxybutinin or other bladder antispasmodics could reversibly worsen his vision by reducing pupillary activity and impairing his ability to accommodate vision for near objects. Older, topical antiglaucoma medications, such as pilocarpine, have parasympathomimetic action and cause pupillary constriction, reducing the visual field and impairing visual acuity. This can be a serious problem in patients with ARMD, who already have impaired central vision. Fortunately, more recently intro- duced topical agents, such as beta-blockers (timolol and others) and prostaglandin analogs (latanoprost and others), lack this problem. Other systemic medications that can affect the eye include systemic corticosteroids, which can increase intraoc- ular pressure, and long-term use can cause cataracts.

Topical antiglaucoma medications can produce systemic effects. These agents are absorbed through conjunctival vessels, and this absorption can be enhanced in conjunctivitis or blepharitis, where vessels are prominent. Ocular agents also enter the nasolacrimal duct through the puncta of the eye, gaining access to the nasal mucosa where they are easily absorbed. Unabsorbed drug reaches the nasopharynx and can be swallowed, but small amounts of swallowed drug are likely to be metabolized, leaving only trivial amounts of active agent available. In contrast, direct mucosal or conjunctival absorption avoids first-pass hepatic metabolism, increasing systemic potency so that, even though small amounts are absorbed, symptoms can result. Systemic absorption can be reduced if the eye is

149 Low vision

closed and the punctum occluded during installation and for at least 15 seconds afterwards.

Ocular beta-blockers have been reported to produce all the systemic effects seen with systemic agents, including hypotension, bradycardia, bronchospasm, and oth- ers. In someone like Mr. L, who is falling, it is important to make sure these agents are not affecting blood pressure or heart rate in any significant way. Parasympatho- mimetic agents such as pilocarpine are generally well tolerated in doses used in chronic glaucoma but in high doses, as used in acute angle closure, they can pro- duce gastrointestinal symptoms, bradyarrhythmias, and other cholinergic effects. The incidence of these effects is difficult to gauge because they are not frequently considered in differential diagnosis. Oral carbonic anhydrase inhibitors such as acetazolamide (Diamox) can produce systemic acidosis or weakness and, when given together with potassium-losing diuretics, can produce severe hypokalemia; today, these agents are generally instilled topically but drug interactions are the- oretically possible, as they have been reported with other ophthalmic agents. Systemic effects of ophthalmic agents are reviewed in the references (see Novack

et al., 2002).

Antioxidants are widely used for ARMD and are generally well tolerated, but caution is advised. High doses of zinc can produce copper deficiency and anemia (thus, copper was added to regimens that contained zinc in the Age-Related Eye Disease Study Research Group, 2001), carotenoids produce yellowing of the skin, which is not believed harmful but can look peculiar, and high doses of vitamin E may impair coagulation in certain circumstances (see Case 21).

4. Medications can be pre-poured in dated pill dispensers (boxes) or bottles should be marked with large print labels. Other low vision assistive devices are prism glasses for near work, high-powered magnifying lenses for reading small print, a hand-held monocular telescope for near vision, hand magnifiers with or without illumination, and a signature guide for check writing and form signing. Community agencies offer low- or no cost courses to the visually impaired to help them acquire skills and use assistive devices to maintain independent living. Local libraries may offer large print books or magazines, or books on tape, and some deliver these items to the home. Resources in some communities include courses in the arts, such as ceramics and sculpture. Web-based resources can assist in finding agencies in many countries, as noted in the references (see Lighthouse International, 2004).

Mr. L should be strongly encouraged to accept assistance and to use his cane, especially when walking outside. If he feels stigmatized by this, he may feel more at ease with alternative devices, such as a specially constructed wheeled grocery cart designed for use as a walker or with a strong umbrella fitted with a rubber walking tip.

5. The primary care provider must have an accurate picture of the patient’s living arrangements and functional capacity in order to make recommendations. A home visit is an excellent method for assessing the home for environmental hazards and seeing how the patient maneuvers in his environment.

Many simple home adaptations can be made to increase the safety of some- one with impaired vision. There should be good lighting with minimal glare. A bedside commode and a night light can help prevent falls at night. Doorbells should be sufficiently loud, and pathways to the door kept free of clutter. Stove and oven dials should be marked in contrasting colors. Household utensils can be marked with contrasting color tape for easier identification in a kitchen drawer. Keys can be marked with color labels. Emergency telephone numbers should be posted in large contrasting lettering near the telephone. The telephone itself can be a one-touch model with large buttons preprogrammed for emergency num- bers and family contacts. Furniture and objects should be kept in the same posi- tions and doors not left half-way open. When possible, the ground floor of a house should be adapted for 24-hour living to decrease the need for going up and down stairs, especially at night; otherwise, the edges of stairs can be painted or marked with contrasting colors or tape. In apartment buildings, entrances and exits should be clearly marked and special attention paid to the adequacy of the lighting.

In the health care settings, there should be a clear line of sight from the door to the receptionist, good lighting with minimal glare, and forms printed in large contrasting type that patients may take home to review carefully. The staff should use the sighted guide technique to assist patients when they are walking in an unfamiliar environment. The patient walks slightly behind the guide and holds lightly onto the guide’s bent elbow. The guide should walk slightly ahead of the patient and announce the presence of steps, doors, and other hazards.

6. Social and psychologic effects of vision loss can be devastating to an elderly patient. The fear of blindness ranks fourth among Americans after the fear of developing AIDS, cancer, and Alzheimer’s disease (Faye and Stuen, 1992). Low vision that occurs late in life increases the risk of decreased mobility, social isolation, and loss of independence. This can lead to depression, loss of self-esteem, anxiety, and sometimes dependence on antianxiety agents and alcohol. These problems, often compounded by other chronic physical impairments, need to be addressed with counseling, use of community resources, and even pharmacotherapy for depression if needed. After a period of reluctance, many patients adapt well to alternative living arrangements such as assisted living facilities, where new social contacts and services can improve quality of life.

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Caveats

1. Prior to the introduction of intraocular lens implants, aphakic spectacles were needed following cataract extraction, which results in aphakia (absence of a lens). Some patients still use these thick, goggle-like spectacles. While providing useful central vision, they do not provide peripheral vision, which can be problematic. A patient who then develops macular degeneration lacks the additional coping mechanism of useful peripheral vision. Another drawback of aphakic spectacles is that they do not correct unilateral cataract extraction, because they produce magnification and distortion in the corrected eye, and unilateral correction would result in double vision.

2. In some instances, the patient must be declared “legally blind” to obtain community services for the visually impaired. The criteria for legal blindness is generally central visual acuity of 20/200 or less in the better eye, even with corrective lenses, or better than 20/200 but with a peripheral field restricted to a diameter of 20 degrees or less. Clinically, the legally blind cannot read the biggest letter on the Snellen eye chart with or without corrective lenses.

R E F E R E N C E S

Age-Related Eye Disease Study Research Group (2001). A randomized, placebo-controlled clinical trial of high dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss. Archives of Ophthalmology, 119, 1417–36.

Fine, S. L., Berger, J. W., Maguire, M. G. et al. (2000). Age-related macular degeneration.

New England Journal of Medicine, 342, 483–92.

Lighthouse International. www.visionconnections.org; accessed February 21, 2005. Novack, G. D., O’Donnell, M. J., and Molloy, D. W. (2002). New glaucoma medications in

the geriatric population. Efficacy and safety. Journal of the American Geriatrics Society,

50, 956–62.

B I B L I O G R A P H Y

Elner, S. G. (1999). Gradual painless vision loss: retinal causes. Clinics in Geriatric Medicine,

15, 25–46.

Evans, J. R. (2002). Antioxidant vitamins and mineral supplements for age-related macular degeneration. Cochrane Database of Systematic Reviews, 2, CD000254.

Faye, E. E. and Stuen, C. S. (1992). The Aging Eye – A Study Guide for Physicians. New York: The Lighthouse Inc.

Fong, D. S. (2000). Age-related macular degeneration, update for primary care. American

Family Physician, 61, 3035–42.

Frock, T. (2002). Gaining insight into age-related macular degeneration. Journal of the Amer-

ican Academy of Nurse Practitioners, 14, 207–13.

Klein, R., Klein, B. E., and Jensen, S. C. (1997). The five-year incidence and progression of age-related maculopathy: the Beaver Dam Eye Study. Ophthalmology, 104, 7–21. Klein, R., Rowland, M. L., and Harris, M. I. (1995). Racial/ethnic differences in age-related

maculopathy. Third National Health and Nutrition Examination Survey. Ophthalmology,

102, 371–81.

Quillen, D. A. (1999). Common causes of vision loss in elderly patients. American Family

Physician, 60, 99–108.

Shields, S. R. (2000). Managing eye disease in primary care. Part 1. How to screen for occult disease. Postgraduate Medicine, 108, 69–72, 75–6, 78.

Smith, W., Mitchell, P., Webb, K. et al. (1999). Dietary antioxidants and age-related macu- lopathy. The Blue Mountains Eye Study. Ophthalmology, 106, 761–7.

Watson, G. R. (2001). Low vision in the geriatric population: rehabilitation and management.

Journal of the American Geriatrics Society, 49, 317–30.

Wormald, R., Evans, J., Smeeth, L. et al. (2003). Photodynamic therapy for neovascular age- related macular degeneration. Cochrane Database of Systematic Reviews, 2, CD002030.

Case 24