Panretinal photocoagulation reduces the risk of visual loss by 50% in patients with diabetic retinopathy. It is recognized that laser expansion into the retina may be associated with photoreceptor loss, retinal pigment epithelial hypertrophy and visual field loss.

Panretinal photocoagulation can cause alteration in retinal vascular permeability therefore, retinal thickness may be increased including retinal nerve fiber layer. On the contrary, it can damage retinal cells including ganglion cells, which may decrease the retinal nerve fiber layer thickness in the latter follow up period.

Peripapillary retinal nerve fiber layer can be measured by optical coherence tomography which is a non-invasive technique for obtaining high resolution cross sectional images of a tissue.

Pre laser assessment:

• Assessment of medical and family history
• Refraction and best corrected visual acuity
• Anterior segment examination using binocular slit lamp bi-microscopy.
• Posterior segment examination.
• OCT scan of peripapillary area

Post laser assessment ( at 1,3 and 6 months):

• Refraction and best corrected visual acuity.
• Anterior segment examination using binocular slit lamp bi-microscopy.
• Posterior segment examination.
• OCT scan of peripapillary area.

Inclusion Criteria:

• Patients with a clinical diagnosis of proliferative diabetic retinopathy.
• Treated by panretinal photocoagulation.
• Age between 40-70 years old.

Exclusion Criteria:

• Patients with densely opaque media (as dense cataract or vitreous hemorrhage).
• Glaucomatous patients.
• Any other associated retinopathy.

The study will be carried out on patients with a clinical diagnosis of proliferative diabetic retinopathy treated by panretinal photocoagulation.