Diagnosis: Neovascular glaucoma secondary to proliferative diabetic retinopathy
This patient has developed a secondary glaucoma, neovascular glaucoma, due to uncontrolled diabetes. In the eye, poorly controlled diabetes initially leads to microaneurysms of the retinal vessels which bleed and leak exudate leading to dot blot hemorrhages, hard exudates, and macular edema. This stage is referred to as non-proliferative diabetic retinopathy. In more severe stages ocular ischemia develops which stimulates vascular endothelial growth factor (VEGF) production. The VEGF promotes angiogenesis or development of abnormal retinal blood vessels, which is referred to as proliferative diabetic retinopathy. These blood vessels are abnormal and prone to bleeding and leakage which can lead to retinal hemorrhage and vitreous hemorrhage. In severe cases, the VEGF stimulates growth of blood vessels (neovascularization) in the trabecular meshwork. These blood vessels block aqueous outflow through the trabecular meshwork, leading to increased intraocular pressure. A sign of possible neovascularization of the trabecular meshwork, is presence of blood vessels on the iris (neovascularization of the iris), which was present on external examination of this patient (see photo below). These iris vessels are also abnormal and prone to bleeding which is why these patients can develop hyphema, or blood in the anterior chamber, in the absence of trauma.
Because aqueous outflow is obstructed, the intraocular pressures can be extremely high, in the 40-50s mmHg (normal 10-21 mmHg). Extremely high intraocular pressure causes the eye to feel firm on palpation and can cause significant periocular pain and headache. This is an ocular emergency, as persistent elevated intraocular pressures can lead to irreversible vision loss.
This case warrants immediate evaluation with an ophthamlologist for many reasons including sudden decrease in vision, presence of rAPD, firm feeling of right eye compared to left eye suggesting elevated intraocular pressure.
Additional ocular complications of diabetes include cataract formation and retinal detachment. Poorly controlled diabetes can accelerate cataract development, which is clouding of the crystalline lens of the eye.
Abnormal new retinal vessels can form neovascular membranes which can contract and tug on the retina, leading to what is referred to as tractional retinal detatchments.
In addition to improving blood sugar control, treatment of diabetic retinopathy includes treatment with intraocular anti-VEGF injections and sometimes laser. Laser treatment of the retina involves applying laser to ischemic portions of the retina to decrease stimulation of VEGF production, This treatment is referred to as laser photocoagulation (see image below), and is usually reserved for cases of severe nonproliferative diabetic retinopathy and proliferative diabetic retinopathy.
References and Additional Resources:
- “Eyewiki: Diabetic Retinopathy.” Available at: https://eyewiki.org/Diabetic_Retinopathy.
- “EyeWiki: Diabetic Macular Edema.” Available at: https://eyewiki.aao.org/Diabetic_Macular_Edema.
- Hendrick AM, Gibson MV, Kulshrestha A. Diabetic Retinopathy. Prim Care. 2015;42(3):451-64.
Case 6 Index