Cornea guttata more prevalent in women and smokers, researchers say

Using non-contact specular microscopy allowed researchers to make the connection and analyze related cell density.

ByMichelle Dalton

ByJared Schultz

People who have smoked for more than 20 pack-years have a more than twofold increase of developing cornea guttata than those who never smoked, according to one study. In addition, women have a higher prevalence of the disease than men, researchers of a large population-based study found.

Fridbert Jonasson

Fridbert Jonasson, MD, and colleagues at the University of Iceland analyzed data from 774 participants of the 5-year follow-up Reykjavik Eye Study. Their goal was to get both descriptive and analytical data including the prevalence of cornea guttata in the population.

To analyze the prevalence rates of cornea guttata, the researchers used slit lamp and non-contact specular microscopy and endothelial specular photography, as well as computer-assisted morphometry, according to the study published in the April issue of Ophthalmology.

All participants were 55 years and older. Men were between 55 and 92 years old, and women were between 55 and 100 years old, researchers said.

Of the male participants, 24 out of 339 right eyes were identified with cornea guttata. Of the women, 47 out of 431 right eyes were identified with cornea guttata. Women had an 11% prevalence of cornea guttata, and men had a 7% prevalence rate. The difference was not statistically significant after adjusting for age.

Cigarette smoking was associated with the disease, and reached a statistically significant level after 20 years of smoking one pack of cigarettes per day, or half a pack a day for 40 years, they said.

“I think this is one more reason for stopping smoking,” Dr. Jonasson said in a phone interview with Ocular Surgery News.

Lower weight levels were significantly associated with cornea guttata, as was a lower body mass index, according to the authors.

Advanced method of analyses

The researchers said this study is the first of its kind where specular microscopy was used for diagnosis of cornea guttata in a population-based sample of Caucasians.

Under specular microscopy, the cornea guttata appears as dark areas in comparison with the healthy white epithelial cells.

Image: Jonasson F

Cornea guttata may be present as “a beaten metal appearance” on slit lamp examination, the researchers said however that it appears as dark areas on specular microscopy and photography (Figure).

“This is a much more advanced method than other methods,” Dr. Jonasson told Ocular Surgery News.

With the help of specular microscopy, Dr. Jonasson and his colleagues were able to establish 5 grades of guttata based on the amount of the area covered by dark spots. Grade 1 was 0% coverage but visible with a slit lamp, and grade 5 was more than 50% coverage.

They did not analyze cornea guttata in the baseline study done in 1996 because the equipment was not available, but did however do specular microscopy and photography of all patients in the follow-up study in 2001, Dr. Jonasson said.

“It is relatively recently that we got instruments allowing a non-contact technique, and that makes it suitable in large population-based studies like ours,” he explained. He also said that this was the only way to properly make a connection between smoking and cornea guttata.

Analyzing cell density

The cornea guttata group had significantly reduced endothelial cell density compared with the non cornea guttata group and this structural change leads to decreased functional capacity of the corneal endothelium.

The results showed that the average cell density in right eyes with cornea guttata was 2,339 compared with non-cornea guttata eyes, which had an average cell density of 2,495.

Although they do not know the exact mechanism that links smoking with development of cornea guttata, Dr. Jonasson said it is likely due to oxidative damage, as is believed to be the case with smoking and other eye diseases.

“We do not know what exactly the pathogenesis is. We have established a dose-response effect since only those who had smoked 20 pack-years had significantly increased the risk of cornea guttata. This may reflect accumulated oxidative damage to the corneal endothelium,” he said.

For more information:

Fridbert Jonasson, MD, is the corresponding author for this study. He can be reached at Department of Ophthalmology, University of Iceland, Landspitalin, 101 Reykjavik, Iceland; +354-543-7228; fax: +354-543-4831; e-mail: fridbert@landspitali.is.

Reference:

Zoega GM, Fujisawa A, et al. Prevalence and risk factors for cornea guttata in the Reykjavik Eye Study. Ophthalmology. 2006;113(4):565-569.

Michelle Dalton is an OSN Correspondent.
Jared Schultz is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses geographically on Europe and the Asia-Pacific region.