Free Radicals, Antioxidants and Eye Diseases: Evidence from Epidemiological Studies on Cataract and Age-Related Macular Degeneration

Abstract

Cataract and age-related macular degeneration (AMD) are the major causes of vision impairment and blindness worldwide. Both conditions are strongly age related with earlier signs (usually asymptomatic) occurring in middle age and becoming severer and more prevalent with increasing age. The aetiology of these conditions is thought to fit with the ‘free radical theory’ of ageing which postulates that ageing and age-related diseases result from the accumulation of cellular damage from reactive oxygen species (ROS). Mitochondrial energy production is a major source of endogenous ROS. External sources of ROS include environmental sources especially solar radiation, biomass fuels and tobacco smoking. There is strong evidence from epidemiological studies that smoking is a risk factor for both cataract and AMD. There is moderate evidence for an association with sunlight and cataract but weak evidence for sunlight and AMD. The few studies that have investigated this suggest an adverse effect of biomass fuels on cataract risk. The antioxidant defence system of the lens and retina include antioxidant vitamins C and E and the carotenoids lutein and zinc, and there is mixed evidence on their associations with cataract and AMD from epidemiological studies. Most epidemiological studies have been conducted in well-nourished western populations but evidence is now emerging from other populations with different dietary patterns and antioxidant levels.

Comparison of macular pigment in patients with age‐related macular degeneration and healthy control subjects – a study using spectral fundus reflectance

“…In the recent years, some insight into pathophysiology of the disease has been gained, and genetic and environmental risk factors have been identified (Wong & Hyman 2008;Feigl 2009;Solomon et al 2009;Boltz et al 2010;Deangelis et al 2011). Oxidative stress has been identified as a key player in the pathophysiological processes of AMD (Beatty et al 2000;Fletcher 2010;Khandhadia & Lotery 2010). The outer retina is particularly prone to oxidative stress because of the high oxygen turnover at the level of the photoreceptors and because of the exposure to high-energy blue light.…”

Novel Protective Effects of Cistanche Tubulosa Extract Against Low-Luminance Blue Light-Induced Degenerative Retinopathy

“…AMD is the most common cause of blindness among the elderly in developed countries and is representative of multifactorial retinopathy [23]. Improvements in technology, such as those observed for digital devices, have resulted in an increase in the amount of time people spend using their handsets, which has led to the development of smartphone dependency and even addiction.…”

Comparative Evaluation of Antioxidant Activities of Ethanol Extracts and Their Solvent Fractions Obtained from Selected Miscellaneous Cereal Grains

“…During fatty acid degradation in peroxisome, H2O2 is known to be generated as a by-product [20]. An excessive production of ROS has been implicated in oxidative damage to biomolecules such as carbohydrates, lipids, proteins, nucleic acids, which would lead to the damage of membranes and cellular organelles, and cause cancer [11,21], cardiovascular diseases [36,45], inflammatory disorders [4], aging and other diseases in humans [9,10]. For protection from the oxidative damage, human body is known to take advantage of not only endogenous antioxidant enzymes, such as superoxide dismutase (SOD), catalase, peroxidase, but also exogenous low molecular weight compounds such as tocopherol, ascorbic acid, and polyphenols.…”