Laser therapy is an established method to stabilize and control proliferative diabetic eye disease. Questions on the long-term effect on the retina from these treatments remain to be answered. The purpose of the study was to evaluate changes in the retina following panretinal photocoagulation (PRP) over time, using structural and functional diagnostic tests.

Diabetic retinopathy is the most common cause of adult-acquired retinal vascular disease. Diabetic retinopathy is estimated to affect more than 100 million adults, and is the leading cause of blindness worldwide.

Over the past 30 years, epidemiological studies and clinical trials have shown that early detection through annual eye exams, intensive glucose and blood pressure control, and timely laser photocoagulation could prevent visual loss. More recently, a variety of newer ocular treatments and medications have been introduced, such as the use of the PASCAL photocoagulation laser system, and various anti-vascular endothelial growth factor therapies. While these treatments have revolutionized how diabetic retinopathy patients are managed clinically, questions on appropriate patient selection and the long-term efficacy and safety of these treatments remain to be answered.

The purpose of this study is to focus on studying the nature and the time course over 2 years of structural and functional changes to the retina following PASCAL photocoagulation in severe preproliferative or proliferative diabetic retinopathy patients.

Inclusion Criteria:

• Male or female patient's greater than 18 years of age who have signed an informed consent.
• Patients with type 1 or type 2 diabetes mellitus (according to ADA or WHO guidelines) that have severe preproliferative or proliferative diabetic retinopathy and require PRP surgery in at least one eye.
• Adequate pupil dilation and clear media to perform laser photocoagulation, HRT, OCT and visual field testing.

Exclusion Criteria:

• Advanced lens opacity (Lens opacity that excludes the ability to capture data)
• Prior PRP within the past year
• Focal laser within one year of study entry