The Role of Macular Pigment Carotenoids in the Pathogenesis and Treatment of Macular Telangiectasia Type 2 (MacTel)

Overview

Macular telangiectasia type 2 ("MacTel Type 2") is an uncommon eye disorder that results in slow vision loss beginning in middle age. The macula is the central part of the retina, which lines the back of the eye like the film of a camera. The macula is responsible for central or reading vision. Telangiectasis refers to dilated, leaky vessels, for example varicose veins in the legs. One of the earliest manifestations of macular telangiectasia type 2 is an acquired reduction and/or redistribution of the macular pigment carotenoids at the foveal center. Currently, the biochemical mechanisms and clinical significance underlying these changes are not known, but it seems likely that better understanding of this phenomenon could lead to new interventions against MacTel. The objectives of this study are to image the maculas of MacTel subjects using two-wavelength autofluorescence imaging and resonance Raman imaging to target the 7-degree radius pigment ring characteristic of macular telangiectasia type 2 in order to gain further insight into the significance of this early clinical sign, and to evaluate whether supplementation with oral zeaxanthin can normalize macular pigment distribution in MacTel subjects

One of the earliest manifestations of macular telangiectasia type 2 ("MacTel") is an acquired reduction and/or redistribution of the macular pigment carotenoids at the foveal center. Currently, the biochemical mechanisms and clinical significance underlying these changes are not known, but it seems likely that better understanding of this phenomenon could lead to new interventions against MacTel. Dr. Bernstein's laboratory at the Moran Eye Center of the University of Utah has focused for the past fifteen years on the role of the macular pigment carotenoids, lutein and zeaxanthin, in maintaining macular health. These xanthophyll carotenoids are derived exclusively from the diet, especially from green leafy vegetables and orange-yellow fruits and vegetables. They are thought to protect the macula from light-induced oxidative damage by virtue of their light-screening and antioxidant properties. Dietary supplement products, from infant formula to those aimed at seniors, primarily contain lutein; however the central macula (the fovea) actually has been shown to have higher concentrations of zeaxanthin. Dr. Bernstein's lab has identified and characterized the binding proteins responsible for the uptake and stabilization of lutein and zeaxanthin in the macula, developed new, noninvasive methods to quantify and image carotenoids in the retina and many other non-ocular tissues, and has participated in intervention trials of lutein and zeaxanthin against age-related macular degeneration. As a leading site for identification of MacTel families in North America as part of the "MacTel Project", Dr. Bernstein and other researchers at the University of Utah have unique expertise in the biochemistry and biophysics of the macular pigment carotenoids that may help to hasten progress toward effective diagnosis and intervention against MacTel in a highly collaborative manner. Macular Pigment Imaging: Dr. Bernstein has extensive experience with various methods to image and quantify macular pigment in the living human eye, especially using autofluorescence imaging (AFI) and resonance Raman imaging (RRI). Dr. Bernstein is also currently utilizing these methods to evaluate age-related macular degeneration (AMD) patients participating in the "AREDS2" study. The objectives of this study are two-fold: 1. To image the maculas of MacTel subjects using two-wavelength autofluorescence imaging (AFI) and resonance Raman imaging (RRI) to target the 7-degree radius pigment ring characteristic of macular telangiectasia type 2 in order to gain further insight into the significance of this early clinical sign; 2. To evaluate whether supplementation with oral zeaxanthin can normalize macular pigment distribution in MacTel subjects. This is an open-label pilot study that will enroll up to ten patients affected with macular telangiectasia type 2 and evaluate them every six months for two years. All participants will take 20 mg of zeaxanthin supplement per day for the duration of the study. Macular pigment distributions will be determined using two-wavelength autofluorescence imaging and resonance Raman imaging.