Diabetic Retinopathy

Nonproliferative diabetic retinopathy (NPDR) is the most common form, accounting for 80% of all diabetic retinopathy. Although it rarely results in total blindness, 5-20% of these patients will become legally blind within five years. In the early stages, the retinal findings consist of microaneurysms, hemorrhages and increased vascular permeability, resulting in edema and hard exudates in the central retina (macular edema). In the later stages, venous tortuosity, vascular shunts and retinal ischemia occur. The ischemia may involve small, superficial capillaries and produce cotton wool spots; or there may be more extensive vascular occlusion. Blindness usually results from macular edema, retinal ischemia or progression to the proliferative type.

Proliferative diabetic retinopathy (PDR) is the less common (20%) but more severe form. Over a five year period, 50% of these patients will become legally blind without treatment. In the early stages, new vessels proliferate on the surface of the optic nerve and retina. Hemorrhage, contraction of the vitreous and fibrovascular membrane formation subsequently result in retinal detachments, glaucoma and blindness.

Treatment
The main treatment for nonproliferative diabetic retinopathy is laser photocoagulation for macular edema. Many patients with significant macular edema are asymptomatic with good vision. It is therefore essential to diagnose and treat these patients during this early stage to prevent future visual loss. Treatment, done on an outpatient basis with topical or local anesthesia, burns or seals areas of vascular leakage and significantly reduces the progression and prevalence of severe visual loss.

Laser photocoagulation is also the primary treatment for proliferative diabetic retinopathy. Localized areas of neovascularization are treated directly. Neovascularization on the optic nerve or diffuse retinal neovascularization are treated by photocoagulation of the peripheral retina (panretinal photocoagulation). As in nonproliferative diabetic retinopathy, many of these patients may be asymptomatic despite the presence of extensive neovascularization. Early diagnosis and treatment of these patients is essential in preventing future visual loss. 'I'reatment is done on an outpatient basis with topical or local anesthesia in one to four sessions. Laser photocoagulation has proven extremely effective in reducing the prevalence of severe visual loss.

When hemorrhage or retinal detachment occurs in proliferative diabetic retinopathy, vitreous surgery (vitrectomy) may be necessary. In this procedure, small instruments the size of 19 or 20 gauge needles are inserted into the eye and under microscopic visualization, the hemorrhage and membranes are removed. Approximately 60% of patients have visual improvement following vitrectomy.

Prevention
Although we can't prevent the occurrence of diabetic retinopathy, good medical control and early diagnosis and treatment of the retinopathy can significantly reduce the progression to severe visual loss. This obviously requires close cooperation between the primary physician, ophthalmologist and patient. The primary physician not only plays a key role in medical management but assumes responsibility for patient education and coordination of care. All diabetics should be referred to an ophthalmologist upon diagnosis and then for periodic ophthalmic examinations.

Diabetic Retinopathy Summary

1. Nonproliferative Retinopathy
   
   1. Most common
      
   2. 5-20% legally blind (5 years)
      
   3. Microaneurysms, hemorrhages
      
   4. Macular edema and exudates
      
   5. Ischemia
   6. Laser treatment of macular edema
2. Proliferative Retinopathy
   
   1. Least common (most severe)
      
   2. 50% blind (5 years)
      
   3. Vessel growth on disc and retina
      
   4. Retinal detachments, glaucoma
      
   5. Treatment: laser and vitrectomy
3. Treatment
   
   1. Reduces severe visual loss by 60%
      
   2. Most effectively accomplished early, while patient is still asymptomatic
4. Prevalence
   
   1. 15% (4 years)
      
   2. 90% (15 years)

Reference: American Academy of Ophthalmology