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Spectral domain OCT offers new insights on macular telangiectasia
Optical coherence tomography allows an early detection and more precise location of telangiectatic lesions.
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Spectral domain optical coherence tomography has been a step forward in the study of idiopathic macular telangiectasia, adding new information on the morphology and progression of this rare condition.
On OCT, a central empty space is visible, with underlying discontinuation by smaller cavitations of the photoreceptor layer.
“We can observe hyporeflective areas that may extend to all the layers of the neurosensory retina. These cavitations appear morphologically different from those produced by other conditions, such as inflammatory macular edema or diabetes. This raises a number of questions on their nature and origin, particularly because they don’t have an angiographic translation,” Gisèle Soubrane, MD, PhD, said.
Detection and location
OCT allows an early detection and more precise location of telangiectatic lesions and is particularly useful in analyzing the modifications of the external neurosensory retina and photoreceptor layer.
Telangiectasias are conventionally classified into three groups. The most commonly seen is group two, the so-called “occult,” bilateral, non-exudative telangiectasia. It progresses through three characteristic stages: first, a discoloration of the parafoveal retina; second, a dilation of the temporal capillaries; third, an angulation of retinal vessels toward the deep layers. Further progression produces pigmented deposits at the extremities of these vessels and, eventually, subretinal neovascularization.
Spectral domain OCT also provides additional evidence of how current treatments produce no modification of the lesion, although they may reduce the secondary subretinal neovascularization occurring in the most advanced stages.
“Laser photocoagulation has become the most common treatment option over the past 10 years. It may have some efficacy in destructing the regrowth of neovascular lesions, but results on visual acuity are unproven and mostly poor. To date, we have … no treatment that specifically addresses the telangiectasia itself,” Prof. Soubrane said.
Fashionable therapy?
Anti-VEGF has more recently been attempted as a treatment in a few studies, but according to Prof. Soubrane, there are no scientific reasons to consider it as an option.
“I suspect that it is more of a fashionable than a rational therapy,” she said.
She showed the results of two studies in which repeated 1.5-mg injections of Avastin (bevacizumab, Genentech) were used at 4-week intervals in patients with stage-two telangiectasia.
“All we can see on fluorescein angiography is a reduction of hyperfluorescence, but not of the staining site. No significant changes in retinal thickness were visible on OCT. The authors may say that there was a decrease, but it was in the order of 20 µm to 22 µm, at the most. The cavitations were still there, with very little modifications during the follow-up,” she said.
Also, the gain in visual acuity was small, about eight letters on average.
“An improvement that we would not consider as statistically significant,” Prof. Soubrane said.
The little improvement that was obtained was because of the effects of bevacizumab on the intraretinal neovascularization.
“We are back again to a treatment that deals with the secondary effects of advanced stage telangiectasia but does not address the telangiectatic process itself,” she said. “Therefore, there are no advantages and no indications for the use of anti-VEGF in this specific pathology.”
Triamcinolone, which was also used in small studies, gave no better results on visual acuity and caused cataract in more than half of the eyes and ocular hypertension in nearly 40% of the eyes.
“Clearly, another approach must be considered, which should be highly dependent of the identification of the physiopathogenesis of the occurrence of telangiectasia,” Prof. Soubrane said. – by Michela Cimberle
- Gisèle Soubrane, MD, PhD, can be reached at Hopital Intercommunal de Créteil, University of Créteil, 40 Ave. Verdun, 94010 Créteil, France; +33-14-517-5221; fax: +33-14-517-5227; e-mail: gisele.soubrane@chicreteil.fr.