Intravitreal triamcinolone may cause elevated IOP

In the late 1970s, injection of intravitreal steroids was shown to be effective for treating retinal detachments and retinal neovascularization in a rabbit model, according to reports by Machemer and Tano. Triamcinolone was used because it lasted longer in the vitreous than dexamethasone. The reason for this is that triamcinolone has a lower solubility in water than dexamethasone, explained Dr. Lim, assistant professor of ophthalmology, glaucoma service, UC Davis department of ophthalmology, Sacramento, CA.

The problem with IVTA is its high incidence of elevated IOP, reported to occur in 32% to 52% of patients treated for various retinal diseases. This is not really surprising when one studies the history of steroid-induced glaucoma.

Clinicians need to monitor patients closely after IVTA injections because elevated IOP can occur as soon as 1 week after treatment. However, in most cases, elevated IOP has been seen at about 4 to 8 weeks after injection, she said.

How long does it last? Triamcinolone will last up to 3 months in the vitreous. Although there are no specific reports on duration of elevated IOP, a few studies with follow-up longer than 6 months showed that most patients discontinued use of anti-glaucoma medications at about 8 months.

So do the benefits of IVTA outweigh the risks? There is a definite anatomic improvement, according to a number of studies. Dr. Lim presented a case of a patient with cystoid macular edema after cataract surgery. The edema resolved at 3 months after IVTA injections and the retinal thickness dropped from 428 to 282 μm.

As far as functional improvement, the reported results are not so clear, Dr. Lim said. Three different studies looked at the improvement of visual acuity in patients who received IVTA for diabetic macular edema. In the Martidis study published in Ophthalmology in 2002, IVTA was helpful in these patients, although there was no control group. In the Jonas study published in Archives of Ophthalmology in 2003, there was only minimal improvement in visual acuity but a significant difference from the control groups. In another report by Massin published in Ophthalmology in 2004, patients receiving IVTA injections had no improvement in visual acuity when compared with the control group.

Patients with non-ischemic central retinal vein occlusion did have improved visual acuity following IVTA, according to three published reports.