Description,Symptoms, SIigns,Incidence and Significance
See: Diabetes – Proliferative Retinopathy Assessment
Diabetes – Introduction to Retinopathy, Diabetes – Nonproliferative Retinopathy, Retinal Detachment, Glaucoma – Classification.
Intravenous fluorescein angiography demonstrates leakage from new vessels, capillary nonperfusion and macular ischemia.
Panretinal laser photocoagulation reduces the incidence of severe visual loss in PDR by up to 95 percent when certain ‘high risk characteristics’ are present:
- NVD larger than one-third of the optic disc area.
- NVD with vitreous or preretinal hemorrhage.
- NVE larger than one-half of the optic disc area with vitreous or preretinal hemorrhage.
By mechanisms that are imperfectly understood, laser treatment induces involution of new vessels (including NVI) and reduces the incidence of vitreous hemorrhage. A common treatment schedule is the delivery of approximately 2500 burns over 2 to 4 sessions, from the posterior fundus to the peripheral retina, sparing the optic disc and macula. Complications include macular edema, reduced visual fields and impaired color vision and dark adaptation. Any pre-existing macular edema should be treated prior to panretinal laser photocoagulation. When hazy ocular media preclude laser therapy, peripheral retinal cryotherapy and transscleral diode laser photocoagulation are alternative treatments.
Some of the indications for vitrectomy include:
- Persistent vitreous or preretinal hemorrhage precluding panretinal photocoagulation.
- Tractional retinal detachment, or combined tractional and rhegmatogenous detachment.
- Progressive fibrovascular proliferation.
- Persistent neovascularization despite laser treatment.
The vitreous gel is removed, fibrovascular tissue is excised, and any retinal breaks are sealed. Panretinal photocoagulation is then applied. Overall, visual improvement is achieved in 70 percent of patients, while vision is reduced in 10 percent. Subsequent deterioration in vision may be due to neovascular glaucoma, recurrent hemorrhage or retinal detachment, or cataract, which may require further surgery.
Patients without high-risk characteristics are reviewed at 3 month intervals. Patients are reviewed 1 month after laser treatment. Depending on progress, additional treatment or vitreous surgery may be required. Findings with involution of PDR include pale ‘ghost’ vessels, absorption of retinal haemorrhages and optic disc pallor. Although vision is usually stable thereafter, review at 6-month intervals is recommended to detect recurrences.
Advanced proliferative diabetic retinopathy (PDR) with neovascularization and preretinal hemorrhage
The same eye as in Figure 1, two months later, following pan-retinal laser photocoagulation treatment.
The same eye as in Figure 1 and 2, a further 3 months later, following surgical vitrectomy.