Patients with diabetes, because of poor circulation to the retina, sometimes develop new and abnormal vessel growths in the eye. This is called proliferative diabetic retinopathy. These abnormal vessels cause bleeding, scarring, retinal detachment, and can lead to severe and permanent vision loss. Although it seems that the extra blood vessels would be helpful, they are not. The new blood vessels are fragile and prone to bleeding. Bleeding into the inside of the eye is called a vitreous hemorrhage. This causes severe loss of central and peripheral vision. If vitreous hemorrhage doesn’t clear on its own, it can be treated surgically. The new blood vessel growth in proliferative diabetic retinopathy include scar tissue most of the time. This scar tissue often contracts and pulls on the retina causing tractional retinal detachment. Panretinal laser reduces the risk of vision loss by decreasing the development of vitreous hemorrhage and tractional retinal detachment.
Panretinal photocoagulation is performed with a laser in the office. This laser therapy usually requires over 1000 laser spots total. Depending on the severity of the proliferative diabetic retinopathy, over 2,000 laser spots can be necessary to stop the proliferative process. Usually the laser is performed over multiple sessions. It can hurt, so sometimes an anesthetic injection is used behind the eye prior to the laser to reduce the pain.
Panretinal photocoagulation reduces the risk of severe vision loss by 50 percent in patiets with high risk proliferative diabetic retinopathy. By severe vision loss, we mean vision loss to the point where the patient cannot see well enough to walk around the room without bumping into things. Prior to the discovery of panretinal photocoagulation, it was not uncommon for diabetics to be blind and need a white cane. Today, that level of blindness is very rare.
Panretinal photocoagulation can decrease the reading vision in younger patients making them need reading glasses. It can also cause a slight dilation of the pupil. Macular edema occurs in some patients after panretinal photocoagulation but almost always responds to treatment.