SIGNS AND SYMPTOMS
Fluctuating visual acuity secondary to unstable blood sugar is a common ocular sign. Swelling within the crystalline lens results in large sudden shifts in refraction as well as premature cataract formation. Changes in visual acuity will depend upon the severity and stage of the disease.
In the retina, weakening of the arterioles and capillaries may result in the characteristic appearance of intraretinal dot and blot hemorrhages, exudates, intraretinal microvascular abnormalities (IRMA) microaneurysms, edema and cotton wool infarcts. Proliferative diabetic retinopathy is the result of severe vascular compromise and is visible as neovascularization of the disc (NVD), neovascularization elsewhere (NVE) and neovascularization of the iris (NVI, or rubeosis irides). Neurological complications include palsies of the third, fourth and sixth cranial nerves as well as diabetic papillitis and facial nerve paralysis.
Biochemistry involving the formation of sorbitol plays a role in the destruction of pericytes, which are cells that support the vascular endothelium. As the supportive pericytes perish, capillary endothelium becomes compromised, resulting in the vascular leakage of blood, protein and lipid. This, in combination with thickened, glucose-laden blood, produces vascular insufficiency, capillary nonperfusion, retinal hypoxia, altered structure and decreased function. The formation and release of vasoproliferative factors which play a role in the genesis of retinal neovascularization are poorly understood.
Most non-vision threatening sequelae of diabetes resolve spontaneously over the course of weeks to months following medical control. In cases where there are large refractive changes, patients may require a temporary spectacle prescription until the refraction stabilizes. The most important element of
MANAGEMENT is education so that patients are informed that they may eventually need to change their spectacle lenses.
When retinopathy threatens the macula or when new blood vessels proliferate, refer for laser photocoagulation. The Diabetic Retinopathy Study (DRS) has conclusively proven that panretinal photocoagulation was successful in reducing the risk of severe vision loss in high risk patients. It defined the high risk characteristics as: (1) Neovascularization of the optic disc (NVD) one-quarter to one-third of a disc diameter in size and (2) Neovascularization elsewhere (NVE) with any vitreous hemorrhage.
If the patient exhibits either of these high risk characteristics, refer him or her to a vitreoretinal specialist.
The Early Treatment of Diabetic Retinopathy Study (ETDRS) has shown that focal/grid laser photocoagulation reduced the risk of moderate vision loss in patients with clinically significant macular edema, defined as: (1) retinal thickening at or within 500 microns (one-third of a disc diameter) of the center of the foveola, (2) exudate at or within 500 microns of the center of the foveola only if associated with retinal thickening, or (3) an area of retinal thickening one disc diameter or greater in size, within one disc diameter of the foveola.
If you observe any of these signs, regardless of the acuity, refer the patient to a retinal specialist. Referral is also indicated if you suspect clinically significant macular edema but are having difficulty visualizing the macula or edema.
Other reports in this section
Eyelids & Eyelashes | Conjunctiva & Sclera | Cornea
Uvea | Vitreous & Retina | Optic Nerve & Brain | Oculosystemic Disease
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