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Jayne S. Weiss, MD, was understandably concerned when her mother, who is 87, complained of problems with her vision, even though her recent cataract surgery had been uneventful, and a comprehensive dilated exam revealed no ocular cause for a deficit. The visual problems were not easy for her mother to describe. But Dr. Weiss and her brother, who is also an ophthalmologist, were confident that the problem was not dementia or psychiatric illness. They suspected that their mother’s visual complaints were real and were neurologic rather than ophthalmic in origin.

Significantly, Dr. Weiss’ mother has Parkinson disease, a degenerative motor system disorder that is, as in her case, sometimes associated with visual impairment. Dr. Weiss, a cornea specialist who is professor and chairwoman of ophthalmology at Louisiana State University in New Orleans, suspected that most ophthalmologists who do not specialize in neuro-ophthalmology or geriatrics would also be stumped by a presentation like this. Below, two experts from the fields of visual perception and visual rehabilitation provide insights on some of the possible causes of visual complaints in patients with apparently normal eyes.

A Deeper Look at the Visual System

The frustration faced by Dr. Weiss’ family is familiar to Ivan Bodis-Wollner, MD, professor of neurology and ophthalmology at SUNY Downstate Medical School in Brooklyn. Dr. Bodis-Wollner is an expert in pre-emptive perception as well as in the loss of vision unrelated to obvious disease or defects in ocular anatomy.^1,2 In addition, he was the first researcher to describe the specific visual deficits that accompany Parkinson disease.

Neurologic causes of visual symptoms. Dr. Bodis-Wollner said that it is possible for a neurologic disease to seemingly spare the retina, optic nerve and even the occipital cortex but, nevertheless, to impair vision. In addition to the visual cortex, numerous areas of the brain contribute to visual perception, he said. “It is important to appreciate the synchrony among nerve cells, which governs the coordination of multiple phenomena in the brain in order to compose what appears to us as a single, unified image. In the visual system, synchrony occurs among different structures, including the frontal and the parietal lobes and deep structures such as the thalamus.” Disruptions of this synchrony at any point can impair visual perception, he said. “Visual loss can happen in the apparent absence of pathology in the eye. But that does not mean that the cause is idiopathic or that it should be casually dismissed as an expected part of the ‘aging process.’”

OCT reveals hidden ocular pathology. In some cases, however, subtle changes are, in fact, present in the eye itself but cannot be detected through standard eye examinations. Dr. Bodis-Wollner said that new technology, particularly optical coherence tomography, is helpful in uncovering such ocular pathology. “OCT has made possible the visualization of changes we could not previously see in the retinal nerve fiber layer and in hidden inner retinal layers in patients with Parkinson disease,” said Dr. Bodis-Wollner. “This technology may soon let us see hidden retinal changes in Alzheimer’s or other neurodegenerative diseases. The point is that visual deficits whose cause is not obvious on routine ophthalmic exam may nevertheless involve retinal nerve cells as well as the postchiasmal visual pathway in diseases such as Alzheimer’s and Parkinson’s. And, coincidentally, such neurodegenerative disorders may be seen in the aging population. To my knowledge there is no inherent anatomical degradation causing vision loss in the aging population that is not attributable to these or other pathologies.”

Two rare disorders. Dr. Bodis-Wollner said that, in addition to neurodegenerative diseases, visual problems with an elusive etiology might raise suspicions of two unusual phenomena: 1) Charles Bonnet syndrome, the visual hallucinations that haunt some individuals following a significant loss of vision, especially from macular degeneration;³ or 2) “inattentional blindness,” a relatively new phenomenon in the literature described as unconsciously selective vision in individuals with otherwise normal acuity.⁴

How to Enhance Remaining Vision

Dr. Mogk noted that the management of stroke, if not Parkinson’s and Alzheimer’s, has significantly improved over the years. Thus, more people are surviving strokes, but they often have impairments. And in the case of Parkinson disease, Dr. Bodis-Wollner said that just as pharmaceutical therapies can improve motor debility, they can also reverse related visual deficits, at least for a time. Unfortunately, with the treatments now available, the disease breaks through almost universally. “When a patient’s vision is not expected to return,” Dr. Mogk said, “vision rehabilitation empowers patients to maximize their independence with the vision they have. We like to say that we don’t save eyes, we save lives.” Dr. Mogk suggested three key changes in the patient’s home environment. Maximize contrast. “Examples of enhancing contrast include using a white cup for black coffee, a black dish for mashed potatoes, white dishes on a colored placemat or tablecloth, a cutting board with black on one side, white on the other, high-contrast, large-print checks, high-contrast markings on steps, light floors or rugs under dark furniture, and vice versa,” said Dr. Mogk. The two photographs above demonstrate this principle. On the left, visual perception is hindered by lack of contrast (for example, between the mugs and their contents) or confusing patterns (the fork against the napkin). Optimize lighting. “For lighting, it is important to distinguish between room lighting and task lighting. Task lighting, for anything from reading or writing checks to knitting or chopping vegetables, requires that the light be directed onto the task from a fairly near distance, such as a gooseneck lamp for reading and under-cabinet lights for kitchen work. Good lighting is important in halls and on stairways, as it is in bathrooms; be sure to avoid glare from light bouncing off glass shower doors and other reflective surfaces,” she said. Minimize glare. “Vertical window blinds can modulate the light throughout the day, and chairs can be positioned to avoid direct glare. Sometimes, yellow window filters are effective in reducing glare inside, for example, from a south-facing glass patio door,” Dr. Mogk said.

20/20 Is Only Part of the Picture

Lylas G. Mogk, MD, director of vision rehabilitation and research at the Henry Ford Health System in Grosse Pointe, Mich., agreed with Dr. Bodis-Wollner that visual impairment can accompany neurodegenerative disorders and that there is no compelling evidence that aging, per se, causes visual deficits. But aging is certainly associated with AMD, glaucoma and cataract, so the comprehensive ophthalmologist may feel stymied trying to untangle the various possible causes of visual deficits in an older patient, particularly one with apparently normal visual acuity.

Visual symptoms despite good acuity. “I can think of three situations in which the senior patient may complain of poor vision but the ophthalmologist may find no evidence of it on acuity testing,” Dr. Mogk said.

• Changes in contrast and glare sensitivity. “First, decreased contrast sensitivity and its correlate, increased sensitivity to glare, are extremely important with respect to visual function but are rarely tested outside of vision rehab or research studies. Contrast sensitivity may be affected in early stages of cataracts, glaucoma or macular degeneration, when good acuity is still present. Based on my experience with patients with all levels of visual impairment, if I were forced to choose, I would rather have less acuity and better contrast sensitivity than the reverse.”
   
• Dry AMD. “Second, in dry macular degeneration, a patient may have good visual acuity, according to the ophthalmologist’s exam, but may, in fact, have a ring scotoma that surrounds central fixation and significantly impedes reading and other functions. Among our patients, 40 percent of those with dry AMD develop a ring scotoma; in many patients, these scotomata are completely invisible upon ophthalmic examination.”
   
• Stroke. “Finally, unrecognized stroke may cause a partial hemianopia, alexia or both, which will prompt the patient to complain of inability to read, even with 20/20 acuity. A number of patients have come to us with hemianopias—both diagnosed and not—accompanied by undiagnosed alexia.”

When in doubt, try other tests. Dr. Mogk finds the following tests particularly helpful in her diagnostic workup:

• Testing for contrast sensitivity and glare. “The clinician may get an inkling of contrast sensitivity loss without actually measuring it on a chart like the Pelli-Robson by asking patients if they can read small print on a high-contrast reading card but not a newspaper, for example, or by asking if they can recognize faces, which have no contrast, or pour coffee into a black cup, or whether they keep their drapes closed because of glare,” she said.
   
• Testing for ring scotoma. “The definitive test for ring scotoma is macular perimetry with a scanning laser ophthalmoscope, although you may get some information from a central Humphrey as well. If you suspect a ring scotoma, you may start by asking whether the patient can read the newspaper headlines, the bylines and the regular newsprint; those with rings generally cannot read headlines or the newsprint but can read the bylines—the medium-sized print. The headlines are too big to fit into their ring and the newsprint too small or too low contrast to decipher; but the bylines are usually in darker print and slightly bigger than the newsprint.”
   
• Testing for hemianopia and alexia. “Rule out hemianopia with visual field testing. Rule out alexia for words by having the patient read not only individual letters but also words in large print; if alexia is present, record visual acuity by asking the patient to copy the shape of the letter on the chart rather than naming it. If agraphia is also present, display a letter and ask the patient to point to the matching letter on the chart.”

Distinguishing among the confounding ills of age. Deficits in memory, cognition and balance can all be exacerbated by, and confused with, visual loss, Dr. Mogk said, and the depression associated with visual loss can present as systemic lack of energy.

• “With regard to memory, a patient might remember having left her keys on the coffee table, but if she is unable to see them on the coffee table, she may appear, incorrectly, to have a poor memory.”
   
• “Concerning cognition, a patient with low vision might ask who a nearby person is, causing her family to think she is losing cognitive ability—after all, it’s the neighbor she should know perfectly well. With poor contrast sensitivity, however, she cannot distinguish facial features.”
   
• “Balance and mobility are constrained by loss of visual acuity and, even more, of contrast sensitivity as surface variations disappear, increasing the risk of falling and fear of falling, resulting in decreased activity and exercise.”
   
• “Depression often correlates with loss of ability to accomplish basic activities of daily living, which occurs with very early vision loss and has far-reaching implications for health and well-being.”
   
• “Health is compromised in other ways, too; for example, individuals with visual impairment may change their eating habits because of difficulty preparing food, so they may lose weight for no apparent reason.”

When to refer. Dr. Mogk concluded that if no obvious ophthalmic abnormalities can account for the visual deficits, the clinician should consider neurologic entities such as cerebrovascular accidents (especially in the presence of alexia) or Parkinson or Alzheimer disease. Dr. Bodis-Wollner added that most comprehensive ophthalmologists have not been trained to identify pathology that is not immediately observable in the eye and yet impairs their elderly patients’ visual functioning. In such cases, referral to a neurologist or a neuro-ophthalmologist is appropriate.

Respect the Patient’s Complaints—and Feelings

Dr. Weiss hopes that ophthalmologists working with an older patient community will soon learn when to recognize true visual loss in the presence of a healthy eye, and when to refer patients to experts in neurodegenerative disease and low vision rehabilitation. She remembers her mother saying, “It is very frustrating to be told that your eyes are just fine when you know you can’t see.” Dr. Weiss hopes that the cataract surgeon who has completed an apparently flawless surgery and IOL implantation may no longer be so puzzled by visual complaints. “I think we should never again say to these patients, ‘You’re 20/20 so you can’t possibly have any vision problems.’”
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1 Bodis-Wollner, I. Arch Neurol 2002;59(8):1233–1234.
2 Bodis-Wollner, I. J Neural Transm 2009;116(11):1493–1501.
3 Mogk, L. “I See Purple Flowers Everywhere,” in Macular Degeneration: The Complete Guide to Saving and Maximizing Your Sight. (New York: Ballantine; 2003), 236–252.
4 Chabris, C. F. and D. J. Simons. The Invisible Gorilla: and Other Ways Our Intuitions Deceive Us. (New York: Crown; 2010).

SmartSight Resources

SmartSight is an Academy initiative to help ophthalmologists assist their patients who have BCVA less than 20/40, scotomata, visual field deficits or reduced contrast sensitivity. Visit SmartSight (www.aao.org/smartsight) for the following materials and more: Patient handout providing resources for low vision services and tips for optimizing remaining vision.   Information for Eye M.D.s, including steps for examining patients with visual deficits, as well as references and rehabilitation resources.   Sample letter to make primary care physicians aware of a patient’s visual loss and its possible consequences.