Articles about Eye Health and Disease 2002
 

Alternative Treatments for Diabetic Retinopathy

(Intravitreal Steroids for Diabetic Vascular Edema, Martidis A, et al., Ophthalmology 2002;109:920.)

Diabetic retinopathy has traditionally been treated by laser photocoagulation of the retina. This includes laser treatment for diabetic macular edema (swelling of the part of the retina which serves the central vision), as well as laser treatment of the peripheral retina for proliferative diabetic retinopathy (growth of abnormal vessels on the retina which can hemorrhage or cause retinal detachment).  The treatment of diabetic macular edema, which can occur very early in the course of diabetic retinopathy and threaten the vision, is based on the results of the Early Treatment of Diabetic Retinopathy Study (ETDRS), published in the 1980's.  However, many patients do not respond to the traditional laser treatment, or have multiple recurrences of edema.  Eventually the swelling can lead to diffuse cystic changes in the retina, for which the laser has little effect.

One alternative treatment for persistent macular edema is vitrectomy.  Vitrectomy is an outpatient surgical procedure where the vitreous that fills most of the eye is microsurgically removed using highly specialized instruments.  It has been found that if the vitreous is separated from the retina internally, there is often an improvement in the swelling and in the vision.  It is not fully understood why this procedure helps. Some think that tractional forces may be relieved by separating the vitreous from the retina, while others feel that oxygen perfusion to the retina may be improved.  Vitrectomy is a relatively invasive procedure with its own set of risks, and a controlled study needs to determine the efficacy and safety of this procedure in treating recalcitrant macular edema.

Another option of treatment is the use of steroid medication injected into the vitreous of the eye.  In the study cited above, the corticosteroid triamcinolone was injected into the vitreous of eyes which had diffuse cystoid diabetic macular edema.  In 16 eyes of 15 patients, 4 mg of triamcinolone was injected into the vitreous of the eye as an office procedure under eyedrop anesthesia.  All eyes had been treated previously with laser (2 to 6 treatments per eye), and all had persistent macular edema last from 6 to 47 months.  The retinal thickness was measured using OCT (optical coherence tomography).

In 14 eyes (2 did not complete the study), OCT showed an average of a 55% reduction in retinal swelling at 1 month, and 58% at 3 months.  At 6 months there was an average of a 38% reduction in thickness.  The visual acuity improved from 1 to 5 lines of vision at the 1 and 3 month follow-up visits, with 64% showing at least a 2 or more line improvement at 3 months.  Complications included increased eye pressure (controlled with glaucoma medications) and worsening of cataract.  In some eyes the macular edema recurred after 6 months.  There were no complications from the injections themselves.

Another method of steroid delivery into the vitreous is through an implanted sustained release device.  The implant can be attached to the wall of the eye internally through a small incision, and slowly releases the steroid over an extended period of time.  The implant can be removed or replaced, if necessary.  An ongoing clinical trial is determining the effectiveness of this approach.

Another therapy on the horizon is the use of an orally taken inhibitor of protein kinase C.  This protein is under investigation of an inhibitor of VEGF (vascular endothelial growth factor).  Protein kinase C is found in high levels in the retina, and increases in this enzyme is felt to increase VEGF, which in turn leads to new vessel formation in the retina (neovascularization, or proliferative diabetic retinopathy).  There are two ongoing studies looking at the effectiveness of oral protein kinase C inhibitors for diabetic macular edema, and for proliferative retinopathy.

 

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