Clinical News
MEDICAL AND PRODUCT UPDATES

RESTORING VISION
Replacing broken photoreceptors

Two new developments offer hope for some patients with visual loss:

Sight through photosynthesis. Researchers at the U.S. Department of Energy's Oak Ridge National Laboratory and the University of Southern Califor-nia believe a protein found in spinach may be able to revitalize a nonfunctioning light receptor in the eye. The protein generates an electric current of up to one volt when exposed to light.

Researchers have demonstrated that if retinal tissue is stimulated electrically using pinhead-sized electrodes implanted in the eyes of legally blind patients with healthy, intact neural wiring, many can see image patterns that mimic the effects of stimulation by light. This protein, implanted in a retinal cell, would provide similar electrical stimulation.

A method for implanting the protein has been developed, but it's too early to know whether the strategy will actually restore vision.

A photosynthetic protein from the spinach plant may hold promise for restoring vision.

Genetically altered iris cells. According to researchers in Kyoto, Japan, adult iris tissue cells possess the ability to differentiate into photoreceptors. Iris cells implanted with CRX (the homeobox gene that causes embryonic tissue to develop into photoreceptor cells) express rhodopsin, a marker for rod photoreceptors.

Dr. Masayo Takahashi, of the Kyoto University Graduate School of Medicine, believes that it may even be possible to cause the cells to differentiate without implanting a gene because single pigmented ciliary margin cells have shown the ability to become rod photoreceptors under the right conditions.

Dr. Takahashi hopes to begin transplanting the rhodopsin-positive cells in animal trials beginning next year.

IMPLANTABLE CONTACT LENS
New clinical trial data

STAAR Surgical Company recently presented new clinical data from its U.S. Food and Drug Administration (FDA) clinical trial for the implantable contact lens (ICL).

The new data showed that 2.3% of myopic patients (12 out of 529) developed lens opacities following implantation. Of these, eight (1.5%) were seen early in the post-op period and were nonprogressive, with no loss of best-corrected visual acuity at the last visit. These were most likely due to mild trauma at the time of surgery.

The hyperopic study produced four lens opacities among 178 eyes (2.2%). One center was responsible for three of the four opacities, which resulted in two cataract extractions. In the remaining 175 eyes, implanted by 23 investigators, only one lens opacity was observed, with no loss of best-corrected visual acuity. No late anterior subcapsular lens opacities were seen, and no cataract extractions were required in these patients.

VISUAL IMPAIRMENT IN INFANTS
Prenatal solvent exposure

Chronic exposure to organic solvents has been associated with visual impairment in adults. Now, research suggests that levels of organic solvents believed to be safe for an adult may not be safe for an unborn child.

Researchers at the Hospital for Sick Children in Toronto, Canada, tested the visual acuity and color perception of 32 children between the ages of 3 and 7 years whose mothers worked with organic solvents during pregnancy. Compared to age-matched children whose mothers did not work with organic solvents, these children had significantly higher error scores on red-green and blue-yellow color discrimination, poorer visual acuity and some degree of vision sensitivity loss. Three of the children had full color vision blindness.

The risk was greatest for women who worked with several different types of organic solvents, and those who worked with them on a daily basis. Many of the women had jobs in the auto industry, paint industry or in laboratories.

DRY EYE SYNDROME
Hormone replacement side-effects

For the first time, a study has demonstrated a significant relationship between the use of hormone replacement therapy (HRT) in postmenopausal women and keratoconjunctivitis sicca (dry eye). The study was based on information from more than 25,000 women.

Dry eye syndrome was prevalent in:

• 5.9% of women who had never used HRT
• 6.7% of women who took estrogen plus progesterone/progestin
• 9.1% of women who took estrogen alone.

Researchers also reported that each 3-year increase in the duration of HRT use was associated with a 15% elevation in risk of clinically diagnosed dry-eye syndrome or severe symptoms.

The study was reported in the November 7 issue of The Journal of the American Medical Association.