If you ask physicians about the most serious health problems faced by older patients, they will usually list significant medical conditions like heart disease, diabetes or cancer. But ask the patients, and they will complain more about sensory deprivation — the loss of vision and hearing.

This information makes a recent report by the Centers for Disease Control and Prevention particularly alarming. A survey of 11,503 adults over the age of 40, who were known to have mild to moderate visual impairment, found that 39.8 percent did not have an eye examination in the previous year due to no insurance or the cost.

Thirty-five percent did not seek eye care because they felt that they did not need it, and 4.5 percent said they could not get an appointment.

Those over the age of 65 and on Medicare obviously used lack of insurance as a reason much less frequently (23.3 percent). Remarkably, 43.8 percent of Medicare recipients felt they did not need to see an eye doctor, compared to 32.9 percent for those under age 65. Men were less interested in eye exams (41.7 percent) compared to women (28.7 percent).

People seeking eye care varied by state. In Massachusetts, 21.6 percent of those under the age of 65 did not feel the need for eye care; in Tennessee, it was 60.4 percent. For Medicare recipients, 61 percent did not seek care in Massachusetts, compared to 25.4 percent in Florida.

This information should be an urgent wake-up call for public health officials, health care providers and the population at large. Vision is perhaps the most precious of all our sensory functions. Often occurring insidiously over time, loss of eyesight is a cause of functional dependency and poor quality of life. Most importantly, for many conditions, appropriate medical management can prevent blindness.

For younger people, a visit to the ophthalmologist or optometrist primarily evaluates visual acuity and the need for glasses, but it always includes screening to identify the common causes of eye disease — cataracts, glaucoma, macular degeneration and retinal disease. Although some primary care physicians can evaluate eyesight and measure eye pressure, the level of skill required for an accurate evaluation is exclusively the domain of the ophthalmologist or the optometrist, who is trained in all aspects of assessing vision and screening for eye diseases.

The most common cause of significant visual loss is a cataract, a painless clouding of the lens of the eye that interferes with the transmission of light to the back of the eye or retina. Common symptoms include blurred vision, seeing rings around lamps and trouble driving at night. Surgery is needed if vision is impaired sufficiently and interferes with daily functions.

Testing for glaucoma is critically important, as vision loss progresses so slowly that a serious problem may not be identified until virtual blindness is present. Glaucoma is caused by increased eye pressure that damages the optic nerve, impairing the ability to transmit visual images to the brain. Untreated, there is a gradual loss of peripheral vision, which eventually leads to total blindness. The disease is easily diagnosed by measuring eye pressure and treated with drops to lower pressure. Sometimes surgery is needed.