Nutraceutical antioxidant therapy shows promise in protecting the optic nerve and retina.
The eye is a unique organ because it is constantly exposed to light and oxygen, which generate high levels of reactive oxygen species (ROS). The “oxygen paradox” is that higher aerobic organisms cannot exist without oxygen, yet oxygen is also dangerous because of its ability to form ROS. The two body tissues with the highest oxygen demand are the central nervous system and the retina, making them uniquely susceptible to cellular damage by ROS. Significant demands are placed on the eye to create barriers to ROS damage. Oxidative stress plays a critical role in the pathogenesis of glaucomatous optic nerve damage.
Glaucoma comprises a group of diseases that, if not controlled, ultimately results in optic nerve head circulation damage, retinal ganglion cell death, and irreversible blindness. Glaucoma is also believed to inflict migraine headache-like pain in animals when the intraocular pressure (IOP) is elevated. While affected patients often appear to be pain-free, the reverse is true.
Nearly 2% of dogs suffer from glaucoma. Over 40 breeds are genetically predisposed to the condition. There are three types of primary glaucoma in dogs: narrow/closed angle, open angle, and pectinate ligament dysplasia. Secondary glaucoma may also result in irreversible blindness if the underlying cause is not identified and aggressively treated. Causes of secondary glaucoma include anterior uveitis, lens-induced uveitis, lens instability, retinal detachment, and intraocular neoplasia.
The goals of the practitioner should be to determine if: (1) glaucoma is present; (2) it is primary or secondary; (3) it is acute or chronic. Once these goals are achieved, a treatment plan can be initiated. Traditional medical and surgical therapies have been reviewed elsewhere.
However, traditional therapy is not enough. Nutraceutical antioxidant therapy shows promise in protecting optic nerve and retinal ganglion cells from the harmful effects of glaucoma-induced oxidative stress, which has been shown to be an important part of this disease. In the presence of glaucoma, lamina cribrosa cells generate more intracellular ROS, and have lower antioxidant expression and higher intracellular calcium levels when compared to normal cells.
NF-E2 related factor (Nrf2) is a key transcription factor triggered by oxidative stress. It plays a pivotal neuroprotective role against retinal ganglion cell death in the presence of glaucoma. If oxidative stress is sufficiently controlled in glaucomatous eyes, Nrf2 levels are not elevated. Nrf2 is only upregulated in the presence of huge oxidative stressors.
An antioxidant blend including green tea extract, coenzyme Q10, polyphenols (grapeseed extract) and lipoic acid has been shown to protect the retina, decrease oxidative stress, and decrease IOP in glaucomatous DBA/2J mice. The mice treated with the antioxidant blend had almost no Nrf2; conversely, the untreated mice had high levels. The antioxidant blend almost completely halted the upregulation of Nrf2 and its movement from the cytoplasm to the nucleus of retinal ganglion cells, which means it was not coding for secondary inflammatory mediators. Thus, the oxidative stress in the treated eyes was almost completely halted.
Oxidative stress is a crucial factor in the pathogenesis of glaucoma. Consistent use of nutraceutical support gives hope to this devastating disease by preserving vision longer and “buying time” to allow for surgical intervention.