Panretinal Photocoagulation

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Definition and Indications

Panretinal photocoagulation involves using a laser (photocoagulator) to place laser spots in the peripheral retina for 360 degrees sparing the center of the retina. The central vision is in the macula which is roughly the center 20 degrees of the retina. Most panretinal photocoagulation treatments spare the center 30 degrees of the retina.

 

Panretinal photocoagulation (PRP) is used primarily for patients with proliferative diabetic retinopathy. It is also effective at reducing the risk of vision loss in patients with occlusive retinopathies like central retinal vein occlusion, branch retinal vein occlusion, sickle retinopathy, Eales disease and IRVAN (idiopathic retinal vasculitis, aneurysms, and neuroretinitis).

How it works

nonperfusion
Proliferative diabetic retinopathy (PDR) occurs when diabetic patients develop very poor circulation to the peripheral (side) retina. In response to the poor circulation and low oxygen environment, the retinal cells release vascular endothelial growth factor (VEGF). VEGF causes the growth of abnormal 'new' blood vessels in the retina. This neovascularization (new vessel growth) is dangerous and causes vision loss. Patients with PDR are likely to develop bleeding inside of the eye because the new vessels are fragile. They are also likely to develop tractional retinal detachment because the new vessels grow into the vitreous cavity and attach to the vitreous. When the vitreous contracts, it pulls on the new vessels which are attached to the retina and therefore pull on the retina. If the traction on the retina is sufficiently great, the retinal will pull away from the eye wall and a tractional retinal detachment occurs. Once detached from the eye wall, the retina is away from it's main blood supply and the retinal tissue gradually thins out and dies, leading to irreversible vision loss.

 

Panretinal laser, by destroying peripheral retinal cells that are releasing VEGF, decreases the amount of VEGF inside the eye. This not only protects the eye from the formation of new vessels, it also causes regression of already formed new vessels.

 

Benefit of PRP

vitreous hemorrhage
The risk of vision loss in an eye with PDR is much less once the eye has been treated with panretinal photocoagulation.

 

 

 

 

 

 

 

 

 

Risk of PRP

Panretinal laser is a lot of laser. Most eyes need between 1000 and 3000 laser spots to suppress neovascularization. That much laser has some side effects:

  • Pain during treatment
  • Loss of accommodation (near vision) requiring stronger reading glasses
  • Mild pupillary dilation
  • Minimal peripheral vision loss