For many Yalies, sleep falls pretty low on the to-do list, especially during final exam week. But finals involve more than just stress and 20-page papers: Yale researchers and national experts say late-night studying habits may put students — especially those with contact lenses — at added risk for eye damage.

But even for students with perfect vision, staring at a computer screen or textbook for hours on end, as many Yalies do during exams, can take a toll on the eyes, Daniel Salchow, a professor of ophthalmology at the Yale School of Medicine, said.

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“Looking at an object a constant distance away is not an activity the human eye is designed to do,” he said. “Studies have shown that this unnatural activity reduces the frequency of blinking, which causes irritation and puffiness.”

Blinking helps distribute tear fluid — a substance essential for lubricating the eye as well as providing it with nutrients — around the cornea, Salchow said. In the absence of blinking, he said, the eye dries up.

Prolonged periods of being awake may also cause damage to the eyes, Salchow said. During the day, he said, the eyes are bombarded not only with visual information but also with particles from the air, such as dust and dirt. Sleep is a necessary “time of regeneration,” when tear fluid coats the eyes and they remain shielded from these inputs, he said.

Yalies interviewed — many of whom said they become nocturnal during finals — attest to the effects of reduced sleep on their eyes.

Christopher Williams ’08 said he routinely suffers eye puffiness and tiredness during finals week. He said he uses his eyes to gauge whether he requires sleep, since the coffee he drinks often prevents him from determining whether he needs to rest.

“When my eyes begin to hurt, it’s my signal to stop working,” he said.

In his experience, Williams said, a good night’s sleep is the best remedy for strained eyes, but nonetheless, a dull ache usually persists in the morning.

If students must stay awake for long periods, Salchow said he recommends they take breaks from continuous reading or computer work by looking around or out a window to exercise their eyes. Puffiness can also be remedied without a power nap — to renew the quality of their tear fluid and clean their eyes, students should place warm compresses on their eyelids for several minutes, he said.

But while reading may strain the eyes, prolonged periods of reading probably do not substantially damage vision, Bruce Shields, professor of ophthalmology and visual science at the medical school, said.

“Contrary to popular myth, reading for hours by the light from a fireplace as a youth had no adverse effect on Abraham Lincoln’s vision, and probably has none on Yale students either, by whatever light they are using,” he said. “Reading doesn’t really appear to hurt your eyes … [so] damage to the eyes can’t be used as an excuse not to hit the books.”

He said research has shown that consistent reading correlates with only slightly more near-sightedness. He said in one study, students entering MIT were compared to a group of young people entering the workforce, under the assumption that the former group would be doing more reading. Four years later, the MIT students showed only a slightly greater progression in myopia than the workers, he said.

But students with contact lenses may be even more at risk of eye damage than the average student, especially for infections, Vanessa Tarud, a clinician in ophthalmology at the Yale Eye Center, said.

The most common infections are the result of students with time pressures’ not sticking to optimum cleaning and replacement schedules, showering or swimming with their contacts in or wearing their contacts for too long, she said.

According to the national Contact Lens Council, more than 11 million of the 35 million contact-lens wearers in the United States do not properly take care of their lenses, but Tarud said students may comprise a disproportionate percentage of this pool because of their schedules.

“If you’re awake for 18-20 hours a day, even if you’re not sleeping with your contacts in, that type of schedule is much like if you were,” she said.

She said regular hydrogen lenses are not completely permeable to oxygen, which the eye requires for correct metabolism and to keep the cornea transparent. Using contacts for more than 12-15 hours a day prevents the cornea — a layer that contains no blood vessels and therefore depends on contact with the air to obtain oxygen — from breathing, Robert Bernardino, associate professor of ophthalmology and director of oculoplastics and orbital surgery at the medical school, said. In its absence, inflammation occurs, making vision blurry, she said.

Bernardino said prolonged inflammation can lead to conditions such as corneal toxicity, bacterial infection and even permanent loss of vision.

This effect is amplified if students sleep with their contacts in their eyes, Tarud said.

Indeed, sleeping without taking out contacts may be fairly common among contact wearers at Yale, especially during finals week, students interviewed said.

Sally Tan ’10 said she has accidentally fallen asleep several times while studying, only to wake with sore eyes.

“Usually I fall asleep without even realizing it,” she said. “Sometimes, my eyes hurt so much that I can’t even open them again.”

But Tan said she adopts a different strategy during finals week to minimize occurrences like this: using her glasses. Several student interviewed who said they wear their contacts during the day said they switch to glasses at night while doing their homework.

While the soreness is usually momentary for Tan, for some students, falling asleep while wearing contacts can lead to prolonged discomfort.

Bharat Ayyar ’10 said he developed a corneal ulcer from forgetting to replace his bi-weekly lenses on time and then falling asleep with them in his eyes. The condition — which made his eyes red, sore and watery — prevented him from wearing contacts for a two-week period, Ayyar said.

Ayyar is a staff reporter for the News.

Tarud said she recommends that students with irregular sleep cycles wear contacts made from silicon hydrogen. The material is a new technology that has a greater permeability to oxygen and may significantly reduce the chances of eye infection or discomfort with prolonged contact use, she said. If discomfort persists, she said she recommends re-wetting drops or taking a “contact lens holiday.”

The Advanced Medical Optics recently launched a nation-wide campaign entitled Elevate Your Eye Care (EYE) in order to raise awareness among youth about proper care for contact lenses. The campaign urges students to “rub and rinse” their lenses — a precaution that takes only 20 seconds and that substantially lowers students’ risk of eye infection, AMO representatives say.