Is Heavy Computer Use Linked to Glaucoma?

Many people have seen the following headline:

Heavy Computer Use Linked to Eye Disease

Study: Near-sighted people at increased risk of glaucoma

But is the information valid?

Here are excerpts from one article regarding the recently published study:

Heavy computer use could be linked to glaucoma, especially among those who are short-sighted, fear researchers Dr Masayuki Tatemichi, from Toho University School of Medicine, and his colleagues tested the sight of workers in four different Japanese companies, employing over 5,000 people each.

The employees were asked to complete questionnaires about their computer use, both at home and at work, and any history of eye disease. The researchers then divided the employees according to how much they used a computer, labeling them light, medium or heavy users. Computer use was categorized in four blocks of five years, ranging from less than five years to more than 20 years, as well as four blocks of the average amount of time spent at the screen per session, ranging from less than one hour to more than eight hours at a time. Those classified as heavy users tended to be men and younger. Overall, 522 (5.1%) of the employees were found to have visual field abnormalities.

Workers who were classified as heavy computer users were more likely to be long-sighted (hypermetropia) or short-sighted (myopia). Around a third (165) of these workers had suspected glaucoma. Upon further analysis, heavy computer use, suspected glaucoma and short-sightedness appeared to be interlinked.

The authors do not know why this might be, but believe it could be that short-sighted people are more susceptible to computer use-related eye strain.

To help put this information in perspective here are some comments by ophthalmologists.

Nick Astbury, president of the UK's Royal College of Ophthalmologists, pointed out that Japanese populations had a high prevalence of myopia anyway and that short-sightedness is a known risk factor for glaucoma. "I doubt whether staring at computers makes any difference," he said.

David Wright, chief executive of the International Glaucoma Association, said: "There may be a risk in heavy use of computer equipment.
"It would be wise for anyone involved in such heavy usage to ensure that they receive regular comprehensive eye examinations in order to detect the earliest possible signs of the development of glaucoma when treatment is most effective." He said three eye tests should be carried out to check for glaucoma: ophthalmoscopy (a visual examination of the optic disc), tonometry (a measurement of pressure in the eye) and perimetry (which checks for visual field anomalies). "It will be important to follow this study with further research in other ethnic populations in order to establish the complete validity of this initial indication of a potential problem and also to address the ethnic risk factors should the evidence add to the Japanese report," he said.

Lou Pasquale, Harvard made the following comments in a letter to the American Glaucoma Society. As the authors acknowledge, and as this group is aware, causal relationships between any potential determinant and a disease can not be claimed from a cross sectional analysis such as this one. The authors do minimize recall bias by first surveying participants for computer use prior to assessing the visual fields. The instrument used to ascertain computer use was not validated ( I suspect this would have been possible if one looked at computer login times and correlated them with responses on the questionnaire). Visual fields were assessed with FDT C-20-1. If the study participant had a single sector that was abnormal at the 5% level or worse, the field was regarded as abnormal. If the field was abnormal it was repeated. 40% of subjects with abnormal VFs did NOT have a confirmatory exam to make a definitive diagnosis of glaucoma calling into question any claims about the association between computer use and glaucoma. With respect to the relation between FDP visual field abnormality and computer use (that is the title of the paper), the authors did find a significant interaction between refractive error (unspecified but assumed to be myopia) and computer use. They therefore stratified the population into those with and without refractive error. After controlling for BMI, OHTN, FH gl, and smoking, heavy computer use was associated with an abnormal FDT field in subjects who wore glasses. This was not the case for those who did not wear glasses. The authors provide no biologic hypothesis to explain these data.

Translation: A recent study of Japanese people who use computers found an elevated incidence of glaucoma. The study was not properly designed to determine if there was a genuine connection and there are many explanations of the findings. Further studies are already underway.