Retina diseases

GUANYLATE CYCLASE-ACTIVATING PROTEINS AND RETINA DISEASE... 

A disease process characterized by deterioration of the macula of the retina that results in a loss of shaip central vision. AMD is the leading cause of central vision loss in the developed countries today for those over the age of fifty years. 

Disorder characterized by atrophy ofthe choroid (the thin membrane covering most of the posterior of the eye between the retina and sclera) and degeneration of the retinal pigment epithelium resulting in night blindness. The disease is caused by mutations in Rab escort protein Repl (component A of Rab geranylgeranyl transferase). 

The incidence and severity of ROP both rise with decreasing birthweight and gestational age. Fielder et al. (1992) have shown that the incidence of ROP in infents of < 1700 g birthweight is about 50%, although only 5% had severe disease. Severe ROP results in vitreous haemorrhage from new vessel formation on the immature retina, retinal traction and eventually retinal detachment (Fig. 9.6). In the most severe cases, retinal detachment is complete, resulting in total blindness. Treatment with cryotherapy or laser has halved the incidence of retinal detachment. 

A new therapy involves treatment for neovascularization of the retina, a disease in which proliferation of... 

FIGURE 13.4 (See color insert following page 336.) Topography of the MP. This figure schematically shows the distribution of the yellow MP across the retina horizontally (top) and vertically (bottom). (From Gass, J.D., Stereoscopic Atlas of Macular Diseases Diagnosis and Treatment, Vol. 1, Mosby - Year Book Inc., 3, 1997. With permission.)... 

The observation that lutein and zeaxanthin occur in the highest concentration in the macula soon raised expectations that the macular xanthophylls may be essential in maintaining structure and function of the retina by contributing not only to risk reduction of macular diseases but also to improving visual performance of the healthy eye, which was the original hypothesis to explain the presence of the macular yellow pigment as mentioned previously. 

Mares, J. A., T. L. LaRowe et al. (2006). Predictors of optical density of lutein and zeaxanthin in retinas of older women in the carotenoids in age-related eye disease study, an ancillary study of the women s health initiative. Am. J. Clin. Nutr. 84(5) 1107-1122. 

Racemase deficiency. The biological role of 2-methyl-acyl-CoA racemase has only recently been clarified. This peroxisomal enzyme is essential for certain steps of the oxidation of phytol and bile acid derivatives, which are stereospecific. Biochemically there is accumulation of pristanic acid and C27 bile acid intermediates. Clinical symptoms may include adult-onset peripheral neuropathy, pigmentary degeneration of the retina and liver disease [ 13]. 

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