The human macula uniquely concentrates three carotenoids: lutein, zeaxanthin, and meso-zeaxanthin. Lutein and zeaxanthin must be obtained from dietary sources such as green leafy vegetables and orange and yellow fruits and vegetables, while meso-zeaxanthin is rarely found in diet and is believed to be formed at the macula by metabolic transformations of ingested carotenoids. Epidemiological studies and large-scale clinical trials such as AREDS2 have brought attention to the potential ocular health and functional benefits of these three xanthophyll carotenoids consumed through the diet or supplements, but the basic science and clinical research underlying recommendations for nutritional interventions against age-related macular degeneration and other eye diseases are underappreciated by clinicians and vision researchers alike. In this review article, we first examine the chemistry, biophysics, and physiology of these yellow pigments that are specifically concentrated in the macula lutea through the means of high-affinity binding proteins and specialized transport and metabolic proteins where they play important roles as short-wavelength (blue) light-absorbers and localized, efficient antioxidants in a region at high risk for light-induced oxidative stress. Next, we turn to clinical evidence supporting functional benefits of these carotenoids in normal eyes and for their potential protective actions against ocular disease from infancy to old age.

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Aim:The results of a study designed to investigate the predictive value of preoperative anterior chamber depth (ACD) and intraocular pressure (IOP) are reported. The relation between these factors and their effect on the reduction in IOP following phacoemulsification cataract surgery was also studied. Methods: The ACD and IOP were prospectively measured in 103 non-glaucomatous eyes of 103 patients who underwent uneventful phacoemulsification and posterior chamber intraocular lens (PCIOL) implantation. Other data which were recorded included best corrected visual acuity, axial length, lens thickness, and severity of lens opacity. Results: The ACD increased by a mean (SD) of 1.10 (0.44) mm (p,0.00001) and this increase was significantly and inversely related to preoperative ACD (r 2 = 68%; p,0.01). IOP dropped by a mean of 2.55 (1.78) mm Hg following cataract surgery (p,0.0001), and this reduction was significantly and positively related to preoperative IOP (r 2 = 56%; p,0.01), and significantly and inversely related to preoperative ACD (r 2 = 21%; p,0.01). A novel ratio, the pressure to depth (PD) ratio (preoperative IOP/preoperative ACD), was found to be significantly and positively related to the surgically induced reduction in IOP (r 2 = 73%; p,0.01), and IOP was reduced by >4 mm Hg in all patients with a PD ratio .7. Conclusion: The reduction in IOP following cataract surgery was found to be positively related to preoperative IOP, and inversely related to preoperative ACD. Furthermore, these results indicate that a novel index, the PD ratio, is strongly predictive for IOP reduction following cataract extraction, and may prove useful in surgical decision making.A n increase in anterior chamber depth (ACD) has been reported after cataract extraction, 1-5 and a significant drop in intraocular pressure (IOP) following this surgery has also been well documented, 6-8 especially in eyes with narrow angles where it has been found that cataract extraction can permanently normalise IOP. [9][10][11][12][13][14] However, the relation between preoperative parameters and IOP reduction after cataract extraction has not been well described. In this study, we investigated whether preoperative ACD and IOP, and the relation between these variables, are predictive for the surgically induced changes in IOP following phacoemulsification in cataractous eyes. METHODSWe prospectively studied 103 eyes of 103 patients without ocular co-morbidity, all of whom underwent phacoemulsification between October 2002 and December 2003. All subjects were assessed by the same clinician (SI), who was masked to patients' identity; however, it was not possible to mask pseudophakia. This study was approved by the ethics committee of Waterford Regional Hospital and eyes with a history of trauma or surgery were excluded.The following were recorded in the preoperative assessment, which is typically 1-2 weeks before surgery: best corrected visual acuity (BCVA); ACD; lens thickness; axial length (AXL); IOP; and severity of lens opacity. The same details, ...

These results suggest that supplementation with all three macular carotenoids potentially offered advantages over preparations lacking MZ, both in terms of MPOD response and visual performance enhancement.

Foveal MP was positively and significantly related to foveal width in the entire study group. This relationship may be determined by the greater length of the cone axons (Henle fibers) in wider foveas. MPOD was unrelated to foveal thickness in the white subjects. However, in the nonwhite subjects there was a positive association between MFT and MPOD at the 0.25 degrees and 0.5 degrees eccentricities, suggesting that other personal characteristics modulate the MPOD-retinal thickness relationship.

Macular pigment (MP) is comprised of the carotenoids lutein (L), zeaxanthin (Z), and meso--zeaxanthin (MZ), which selectively accumulate at the macula (central retina) of the eye and are neuroprotective. These carotenoids are also present in the brain, and evidence suggests a close correlation between retinal and brain concentrations. We investigated the relationship between MP and cognitive function in 4453 adults aged ≥50 years as part of The Irish Longitudinal Study on Aging. Macular pigment optical density (MPOD) was determined using customized heterochromatic flicker photometry-a quick and noninvasive way of measuring the concentration of the pigment. Lower MPOD was associated with poorer performance on the mini--mental state examination (p = 0.026) and on the Montreal cognitive assessment (p = 0.016). Individuals with lower MPOD also had poorer prospective memory (p = 0.011), took longer time to complete a trail--making task (p = 0.003), and had slower and more variable reaction times on a choice reaction time task (p = 0.000 and 0.001). These associations were only slightly attenuated following adjustment for physical and mental health. There was no significant association between MPOD and verbal fluency, word recall, visual reasoning, or picture memory. Overall, the findings support the theory that xanthophyll carotenoids impact on cognitive function, underscoring the need for exploration of novel, noninvasive biomarkers for cognitive vulnerability and preventive strategies.

METHODS. Subjects consumed daily a formulation containing 10 mg L, 2 mg Z, and 10 mg MZ (active group; n ¼ 53) or placebo (n ¼ 52) for a period of 12 months. Study visits were at baseline, 3, 6, and 12 months. Contrast sensitivity at 6 cycles per degree (cpd) was the primary outcome measure (POM). Secondary outcome measures included CS at other spatial frequencies, best-corrected visual acuity (BCVA), glare disability, photostress recovery, and light scatter. Macular pigment optical density (MPOD) was measured using dual-wavelength autofluorescence, and serum carotenoid concentrations were analyzed using high performance liquid chromatography (HPLC).RESULTS. Compared to placebo, statistically significant improvements from baseline CS were detected at 6 (P ¼ 0.002) and 1.2 (P ¼ 0.004) cpd in the active group. Additionally, improvements in CS were commensurate with the observed increases in retinal concentrations of these carotenoids (r ¼ 0.342, P ¼ 0.002 at 6 cpd). CONCLUSIONS.These results indicate that dietary fortification with the macular carotenoids can have meaningful effects on visual function.