Vision is a very important sense for all humans and animals, isn't it? And when our four-legged friend has an eye disorder, whether due to advanced age or some other factor, such as trauma or chronic illnesses that may affect vision, we get very worried about the possibility that he may go blind or experience pain or discomfort. So let's understand how this happens and look at options to prevent our buddy's eyes from being compromised!
From a metabolic point of view, the eye is a very active structure, continuously receiving and absorbing light. Therefore, oxidative and inflammatory stress are considered to be at the root of almost all eye disorders, such as cataracts, glaucoma, uveitis and retinal degeneration, but these factors are still poorly recognized and considered as targets for prevention [6].
Oxidative stress occurs in inflammatory processes of the conjunctiva, cornea and uvea, in the formation of cataracts, in retinal degeneration and in pathological conditions of the optic nerve, neuritis and glaucoma, with the lens and retina being the tissues most affected by this process. With regard to the conjunctiva and cornea, the metabolic rate is not as high, but they are the most exposed parts of the eye and, for this reason, oxidative stress associated with ultraviolet radiation and allergens is frequent [6].
Thus, fighting ocular oxidative processes is of paramount importance from a therapeutic point of view [6]. In recent years, several studies have shown the role of diverse micronutrients and nutraceuticals in the treatment of eye diseases and new therapies to reduce inflammation and oxidative stress are being used with good results. Below we talk about some of these nutraceuticals.
PEA (Palmitoylethanolamide):
Belongs to the N-acylethanolamine family, which includes the main representative of endocannabinoids which is anandamide. Endocannabinoids bind to the receptors of the same name and are involved in regulating inflammation and pain. PEA is considered an "endocannabinoid-like" - it does not bind directly to endocannabinoid receptors, but acts as a mediator and participates in the biological response to endogenous cannabinoids by preventing their degradation, thus prolonging their action. It has known anti-inflammatory and analgesic activity and this occurs through various mechanisms. The activation of PPARs exerts anti-inflammatory properties by inhibiting the expression of pro-inflammatory genes and reducing cytokines and matrix metalloproteases, as well as stimulating the catabolism of pro-inflammatory eicosanoids. In this way, PEA can improve the functional impairment of the lacrimal glands, inducing an increase in tear production. This anti-inflammatory activity also improves the quality and stability of the tear film, since the reduction in inflammation induces an increase in the mucin secreted by the Goblet cells and an improvement in the secretion of lipids by the meibomian glands and auxiliary glands, improving the osmolarity of the tear film [8]. PEA protects endogenous cells and due to its anti-inflammatory, antioxidant and cytoprotective activity, it is well suited to the treatment of retinopathies, especially those related to glaucoma and diabetes, both diseases linked to chronic inflammation [2].
ASTAXANTHIN:
Astaxanthin is a natural carotenoid pigment belonging to the xanthophyll family, found in marine environments, especially in microalgae and seafood. Due to its unique molecular structure, astaxanthin has important biological properties, such as antioxidant, anti-inflammatory and anti-apoptotic action. Scientific evidence suggests that astaxanthin is effective in the prevention and treatment of various eye diseases, as it combats cumulative oxidative stress and inflammation. Its efficacy in retinopathies, ocular surface disorders, uveitis and cataracts is reported in numerous animal and human studies, which highlight its ability to modulate various metabolic pathways, restoring cellular homeostasis [1].
ZEAXANTHIN AND LUTEIN: Two carotenoid pigments from the xanthophyll subclass, they are present in high concentration in the retina, especially in the macula. They act as a filter protecting the macula from blue light and also as structurally linked antioxidants that protect the surrounding eye cells from oxidative damage. Studies have shown that lutein and zeaxanthin can reduce the risk of various eye disorders, especially age-related macular degeneration. It also has the ability to inhibit the growth and cause apoptosis of malignant tumor cells such as ocular melanoma cells [7].
LACTOFERRIN: This is a glycoprotein produced and secreted by mucosal epithelial cells and neutrophils in various mammal species. Due to its antinflammatory, antioxidant and antimicrobial activities, the topical application of lactoferrin plays a crucial role in keeping the ocular surface healthy [5]. It protects ocular surface cells from the deleterious effects of ultraviolet radiation and reduces tissue responses associated with allergens. It is very useful in animals suffering from keratoconjunctivitis sicca (KCS), as they often have low levels of lactoferrin on the ocular surface, making its supplementation beneficial [6].
OMEGA 3, EPA and DHA: Omega-3 polyunsaturated fatty acids are fundamental structural components of the cell membrane, as well as precursors for the synthesis of numerous biologically active substances. Among their many properties, we highlight their anti-inflammatory and epitheliotrophic properties. They also promote corneal integrity and tear production, among others [3].
VITAMIN A: It is involved in the metabolism, growth and differentiation of the ocular surface epithelium. Vitamin A deficiency caused by malnutrition is one of the main causes of avoidable blindness. Patients with a long-term deficiency of this vitamin can develop complications on the ocular surface such as conjunctival keratinization, corneal epitheliopathy and ulceration [3].
VITAMIN C: This water-soluble vitamin is necessary for the functioning of various enzymes and is found naturally in various foods. The tear film contains high levels of vitamin C, reflecting the high need for antioxidants on the ocular surface. In addition, vitamin C plays an important role in the healing processes of corneal wounds. Some studies have shown that the combination of vitamin C, E, A and astaxanthin significantly improved the function of the lacrimal gland, with consequent stability of the tear film and reduced damage to the corneal epithelium [3].
In general, the main signs of eye disorders are excessive discharge, difficulty opening the eyes or excessive blinking, color changes, irritation of the conjunctiva, red eyes and altered vision. But we know that some breeds are at greater risk of developing eye diseases, either because of genetics or because of the anatomy of their eyes. Brachycephalic dog breeds, whose eyes are more exposed, are more prone to lesions and dryness of the ocular surface, among other things. The same applies to Persian and exotic cats. Breeds such as the Poodle, Schnauzer and Cocker are more likely to develop cataracts. Other breeds, such as the Sharpei, Basset hound, Beagle, Samoyed and Husky, are prone to developing glaucoma.
So, my recommendation is that pet parents should always be aware of any eye changes and, in the case of animals of more prone breeds, taking extra care with their eye health is important, because if we act preventively, using nutraceuticals and carrying out regular ophthalmic examinations, we can avoid the development of more serious problems.
REFERENCES:
1) GIANNACCARE, G. et al. Clinical Applications of Astaxanthin in the Treatment of Ocular Diseases: Emerging Insights. Mar. Drugs v. 18, n. 239, May 2020.
2) HESSELIK, JMK et al. Palmitoylethanolamide, a Natural Retinoprotectant: Its Putative Relevance for the Treatment of Glaucoma and Diabetic Retinopathy. Journal of Ophthalmology Volume 2015, Article ID 430596, 9 pages.
3) PELLEGRINI, M. et al. The Role of Nutrition and Nutritional Supplements in Ocular Surface Diseases. Nutrients, v. 12, n. 952; March 2020.
4) SULAIMAN, R.S. et al. Natural product inhibitors of ocular angiogenesis. Exp Eye Res. 2014 December ; 0: 161–171.Dec. 2015.
5) VAGGE, A. et al. Therapeutic Effects of Lactoferrin in Ocular Diseases: From Dry Eye Disease to Infections. Int. J. Mol. Sci., v. 21, n. 6668, 2020.
6) WILLIAMS, D. Oxidative Stress and the Eye. Vet Clin Small Anim 38 (2008) 179–192
7) YANG, S. et al. Zeaxanthin and Lutein in the Management of Eye Diseases. Journal of Ophthalmology V. 2016, Art. ID 4915916, 2 pages. Hindawi Publishing Corporation Journal of Ophthalmology.
8) ZAZZO, A di. et al. Use of Topical Cannabinomimetic Palmitoylethanolamide in Ocular Surface Disease Associated with Antiglaucoma Medications. Journal of Ocular Pharmacology and Therapeutics. V. 33, Nr. 9, 2017.
#ophthalmology
Comentarios