Macular pigment function

The first hypotheses to explain the physiological importance and function of the yellow macular pigment (MP) dealt exclusively with its putative effects on visual acuity, which were believed to be... 

Schupp, C., E. Olano-Martin et al. (2004). Lutein, zeaxanthin, macular pigment, and visual function in adult cystic fibrosis patients. Am. J. Clin. Nutr. 79(6) 1045-1052. 

Furthermore, several studies have shown that in some individuals an increased intake of xanthophylls does not lead to increased levels of xanthophylls in their plasmas and/or retinas, and macular pigment densities do not exhibit a positive correlation with plasma levels of lutein and zeaxanthin (Aleman et al., 2001 Bernstein et al., 2002b Bone et al., 2000, 2001, 2003 Hammond et al., 1995,1997). These apparently conflicting epidemiological results need to be interpreted with caution as a diet rich in fruit and vegetables includes a great variety of phytochemicals that may independently, or in cooperation with lutein or zeaxanthin, and other dietary components affect carotenoid uptake and function in the retina. 

Figure 5.3 The spectral absorbance of macular pigment plotted with the blue light hazard function. (From Hammond, B.R. et al., Optom. Vis. Sci., 82(5), 387-404, 2005.) This function described the potential for photochemical damage to the retina resulting from exposure to light from about 400 to 500 nm as defined by the IESNA Photobiology Committee for ANSI (ANSI/ IESNA RP-27.1-05).

Comeal deposits of chloroquine may be asymptomatic or may cause halos around lights or photophobia. These are not a threat to vision and reverse when the dmg is stopped. Retinal toxicity is more serious, however, and may be irreversible. In the early stage it takes the form of visual field defects late retinopathy classically gives the picture of macular pigmentation surrounded by a ring of pigment (the bull s-eye macula). The functional defect can take the form of scotomas, photophobia, defective colour vision and decreased visual acuity resulting, in the extreme case, in blindness. 

Relating the Function of Macular Pigment to Retinal Stractnre and Disease... 

Sasamoto Y, Gomi F, Sawa M, Tsujikawa M, Nishida K (2011) Effect of 1-year lutein supplementation on macular pigment optical density and visual function. Graefes Arch Clin Exp Ophthalmol 249 1847-1854. doi 10.1007/s00417-011-1780-z... 

Berendschot, T.T., Plaf J., de Jong, A., and Mensink, R.P. 2009. Long-term plant stanol and sterol ester-enriched functional food consumption, serum lutoin/zeaxanthin concentration and macular pigment optical density. Br JNutr 101 1601-1610. 

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. 

An additional clinical use of acetazolamide is unrelated to its ocular hypotensive properties.The 500-mg acetazolamide capsule administered daily for 2 weeks may produce either a partial or a complete resolution of macular edema in patients with cystoid macular edema (CME), retinitis pigmentosa, and chronic intermediate uveitis (pars planitis). Macular edema produced by primary retinal vascular diseases (branch and central retinal vein occlusion and macular telangiectasia) did not respond to acetazolamide therapy. It is believed that acetazolamide may improve visual function if the macular edema stems from retinal pigment epithelial dysfunction. Improved macular edema in these conditions may be associated with fluid movement from the retina to the choroid. However, acetazolamide does not appear to alter macular blood flow. 

---