Type II diabetes is positively associated with the risk of primary open-angle glaucoma (POAG) in women, according to researchers at the Massachusetts Eye and Ear Infirmary at Harvard Medical School.

The prospective cohort analysis included 76,318 women enrolled in the Nurses' Health Study (NHS) from 1980 to 2000. Eligible participants were at least 40 years old, did not have POAG at baseline and reported receiving eye examinations during follow-up. Potential confounders were assessed on biennial questionnaires; diagnosis of Type II diabetes was confirmed on a validated supplemental questionnaire. During follow-up, 429 self-reported POAG cases confirmed by medical chart review were identified.

After controlling for age, race, hypertension, body mass index, physical activity, alcohol intake, smoking and family history of glaucoma, Type II diabetes was positively associated with POAG. The association did not strengthen with longer duration of diabetes for duration less than five years compared with duration of five years or longer. In secondary analyses to evaluate the potential for detection bias, investigators controlled for additional factors, such as the number of eye exams. Type II diabetes remained positively associated with POAG.

Visible micropulse lesions require six times more power but roughly the same energy as visible continuous wave lesions, and the safety margin is almost four times greater for micropulse than continuous wave diode laser photocoagulation, according to a study by French researchers.

Subvisible micropulse diode laser photocoagulation localizes retinal laser damage because brief micropulses allow little time for heat conduction to spread temperature rise from the retinal pigment epithelium to the neural retina. Treatment power is often chosen as a multiple of what is needed for visible continuous wave lesions. The goal of this study was to measure clinical laser powers needed for visible end point micropulse and continuous wave diode laser retinal photocoagulation.

Six parallel rows of 10 diode laser (810 nm) burns were made in the superior peripheral retina of six consecutive patients undergoing their initial frequency doubled Nd:YAG (532 nm) panretinal photocoagulation for proliferative or severe non-proliferative diabetic retinopathy. All photocoagulation exposures were 125 microns in retinal diameter and 0.2 seconds long. Micropulse exposures were performed with 500 Hz, 0.3 ms micropulses. The minimal power needed for visible continuous wave diode photocoagulation was determined from two adjacent rows of laser lesions; the minimal power needed for visible micropulse diode photocoagulation was determined from four additional adjacent rows of laser lesions. Researchers obtained fluorescein angiograms and red-free fundus photographs immediately and six days after laser photocoagulation in each patient. They then determined the extent to which clinical parameters exceeded ANSI Z136.1-2000 maximal permissible exposure (MPE) levels for laser exposure.

Continuous wave lesions typically required 300 mW (60 mJ) and micropulse lesions typically required 1800 mW (54 mJ). Visible continuous wave exceeded MPE levels by 36 times; micropulse lesions exceeded MPE levels by 133 times. Laser energies were similar for visible continuous wave and micropulse lesions.

The authors found no significant difference in the minimal powers needed for photographically and angiographically apparent diode micropulse lesions. MPE levels are designed to provide a 10-times safety margin. This safety margin was 3.7 times greater for micropulse than continuous wave diode laser photocoagulation.