Intravitreal triamcinolone holds promise for retinal diseases

The results of clinical trials evaluating the effect of triamcinolone given by intravitreal injection may provide the definitive data needed to determine if the benefits of this treatment outweigh the risks.

Dr. Ip underscored just how serious the need is for effective treatments for retinal vascular diseases.

Retinal vein occlusion is the next most commonly occurring retinal vascular disease. There is still no proven effective therapy for macular edema that results from central retinal vein occlusion (CRVO). Grid laser photocoagulation is effective for macular edema arising from branch retinal vein occlusion (BRVO). However, in the Branch Vein Occlusion Study, the investigators found that almost 40% of eyes treated with grid laser photocoagulation still have worse than 20/40 visual acuity after 3 years of follow-up; 12% of the treated eyes are actually worse than 20/200 after 3 years, according to Dr. Ip.

"Because of the lack of a therapy that can reliably improve visual outcomes in patients with retinal vascular disease, a number of treatment approaches have been investigated. These include surgeries and pharmacotherapeutic agents," Dr. Ip noted.

Intravitreal triamcinolone

The injection of triamcinolone intravitreally is presently used for diabetic macular edema, CRVO, and BRVO.

"The rationale for using steroids to treat retinal vascular disease is that hypoxia-induced up-regulation of vascular endothelial growth factor (VEGF) has been observed in diabetic retinopathy, CRVO, and BRVO. VEGF in an animal model increases retinal capillary permeability and retinal edema. Because corticosteroids attenuate the effects of VEGF, the intravitreal injection of a corticosteroid may be an efficient, effective delivery route," Dr. Ip commented.

There have been a number of studies in which triamcinolone has been studied for posterior segment disorders, e.g., diabetic macular edema, CRVO, BRVO-for about 7 years in the United States. Dr. Ip noted the increasing interest in this topic and pointed out that before 2001 no investigators had published articles on triamcinolone. From 2001 to 2003, he identified 24 articles while conducting a literature search using PubMed; from 2003 to 2005, 61 articles were identified.

"This increasing interest has been fueled by a number of case reports that showed the efficacy of intravitreally injected corticosteroids for diabetic macular edema," he stated. "What seems to be common to the studies is that the patients have anatomic improvement and a substantial number of patients have a significant improvement in visual acuity," he explained, but cautioned that the follow-up periods are short and range from 3 to 6 months after treatment.

Studies of cases of retinal vein occlusion similarly show that triamcinolone injected intravitreally might be beneficial. Follow-up periods in the studies to which he referred were 3 to 12 months.

While no treatment is perfect, there are safety considerations associated with triamcinolone. The complications include injection-related complications of retinal detachment, vitreous hemorrhage, and endophthalmitis and the drug-related complications of development of cataract and glaucoma.

Dr. Ip noted that because there are potential benefits associated with triamcinolone injections, the drug has been used by ophthalmologists.

"However, we do this without definitive data on the safety and efficacy of this treatment. The ophthalmology community is in a state of equipoise concerning this treatment," Dr. Ip said. He advised that randomized clinical trials are needed to provide data on whether the treatment benefits outweigh the risks.