Effect of Panretinal Photocoagulation on Optic Nerve Head Topography

Effect of Panretinal Photocoagulation on Optic Nerve Head Topography and Nerve Fiber Layer Parameters

The purpose of this study is to evaluate the optic nerve head changes consequent to panretinal photocoagulation done for diabetic retinopathy.

Panretinal photocoagulation thermally ablates the retina to effect the regression of the neovascular process seen with diabetic retinopathy.2-6 Photocoagulative damage also damages the nerve fiber layer in the process. Since this should theoretically be associated with loss of nerve fibers it is expected to manifest as changes in optic nerve head cupping. There is no available literature to support this hypothesis. In fact the only available study done of the subject refuted the hypothesis.7 The study had a retrospective design and was done before any of the current technology to evaluate optic nerve head morphology was available.

Patients with concurrent glaucoma and diabetes often undergo panretinal photocoagulation as a part of their diabetes treatment. Optic disc cupping is a standard outcome measure for glaucoma diagnosis and progression. If PRP were to cause increased cupping, this can be a significant confounder in determining glaucoma progression based on optic nerve cupping. The findings of the study will help us determine as to how much cupping can be attributed to the PRP, if any at all.

Inclusion Criteria:

• Any patient with proliferative diabetic retinopathy or severe non-proliferative diabetic retinopathy otherwise undergoing panretinal photocoagulation for treatment.

Exclusion Criteria:

• Any patient with uncontrolled glaucoma (IOP above target on any occasion in the preceding 6 months) or other optic neuropathy that may confound the analysis of optic nerve head morphology.
• Patients with media opacities (significant cataract, corneal opacity, vitreous hemorrhage) precluding imaging of the optic nerve.
• No PRP done in the previous 6 months.