October 2008




Heat-inducing lens damage

by Matt Young EyeWorld Contributing Editor



Bakeries are known for tasty pastries, birthday cakes and pies. Among cataract surgeons, they also should be known for their ability to cause damage to the eye lens. At least, that’s what a new study published in April 2008 in Experimental Eye Research suggests. “From our measurements of the ambient temperatures in the neighborhood bakery, and on the basis of thermal analysis of the actual heat reaching the human lenses, we conclude that lenses are exposed to high temperatures and to large temperature fluctuations in the neighborhood bakery,” wrote study co-author Ahuva Dovrat, Ph.D., Rappaport Faculty of Medicine, Technion–Israel Institute of Technology, Haifa, Israel. “In the present study we demonstrated that high ambient temperatures cause optical and structural damage to bovine lenses. The longer the time and the greater the frequency of exposure, the greater also was the damage shown by the cultured lenses.”

Better protective eyewear could help prevent damage to the lens in bakery workers, according to the study.

Concerning evidence

Previous studies have suggested a link between high temperature and cataract. “Workers in the glass industry, which involves high environmental temperatures, are at 2.5 [times] higher risk to lose 30% of their sight as a result of cataract, compared with people from the same group of age who are not exposed to high temperature stress,” Dr. Dovrat reported. Cataract formation after infra-red radiation exposure also has been reported, as has a higher incidence of cataract among molten metal workers, Dr. Dovrat noted. This study is unique in analyzing the bakery as another high-temperature environment that could cause lens damage. First, Dr. Dovrat investigated the temperatures at a bakery during six working days. “In the bakery, workers are exposed to high temperature when working close to the electrical oven,” Dr. Dovrat reported. “As part of the daily work, workers push their heads into the electrical oven. The measurements were taken by attaching a thermometer probe to the temporal side of the eyeball of the worker, and following the temperature changes during a working day.”

Additionally, thermal analysis was performed to determine the temperature of the eye lens when exposed to these environmental temperature changes. “The temperature that eventually reached the lens fluctuated between 35 and 39.5 [degrees] C,” Dr. Dovrat reported. Then, Dr. Dovrat performed the crux of the experiment, which involved a simulation of heat exposure upon a bovine lens organ culture system. “In order to simulate the working conditions in the neighborhood bakery, intact bovine lenses were incubated in culture for about 2 weeks. Control lenses were incubated at 35 [degrees] C throughout incubation period,” Dr. Dovrat reported. “Heat treated lenses were exposed to 39.5 [degrees] C for different times.”

These lenses, which numbered 270, were therefore divided into the following five groups: 1. The control group, which remained in the culture for 11–14 days.

2. Lenses exposed to 39.5 degrees Celsius for 6 hours daily beginning on the second day of the culture; These were kept in the culture for 13 days. 3. Lenses exposed to 39.5 degrees Celsius for 4 hours daily starting on the second day of the culture; These were kept in the culture for 11 days.

4. Lenses exposed to 39.5 degrees Celsius, 2 hours daily for 3 days starting on the second day of the culture; These were kept in the culture for 12 days.

5. Lenses exposed to 39.5 degrees Celsius for 1 hour on the second day of the culture; These were kept in the culture for 14 days. “When we exposed bovine lenses in culture conditions to the same temperature and time that the human lenses were exposed in the bakery during a working week, 4 and 6 h of 39.5 [degrees] C for 8 days, optical damage was demonstrated by recording higher focal length variability values in comparison to control lenses, which were kept throughout at 35 [degrees] C,” Dr. Dovrat reported. “The longer time the exposure to heat, the greater the damage appeared in lens optical quality (dose–response manner). In fact, lens damage was influenced both by exposure length to heat and frequency of exposure, Dr. Dovrat found. “Although one should be careful in extrapolating data from isolated lenses in organ culture to human beings, our study may nevertheless indicate a need for the use of eyewear protection in bakeries,” Dr. Dovrat reported. “On the other hand, the issues of temperature’s impact on lens clarity and the involvement of heat exposure in cataract formation require further investigation.”

William Trattler, M.D., director, Cornea, Center for Excellence in Eye Care, Miami, said it does make some sense that bakery high temperatures could induce lens changes. “We know that our lenses are susceptible to trauma and injuries,” Dr. Trattler said. “It makes sense that heat could be a risk factor for cataract formation over time.” Nonetheless, Dr. Trattler said he doesn’t recall any patients hinting at any kind of heat-cataract formation relationship. But he suggested that a variety of situations do induce cataract formation. “We should use this information to try to correlate with other real world jobs and environmental conditions to see if heat really is a risk factor,” he said.

Editors’ note: Drs. Dovrat and Trattler reported no financial interests related to this study.

Contact Information:

Dovrat: dovrat@tx.technion.ac.il

Trattler: 305-598-2020, wtrattler@earthlink.net

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