Legal blindness: Nursing

Legal blindness is defined as having a central visual acuity of 20/200 or less in the better-seeing eye, or having a peripheral visual field of 20 degrees or less. So, many people who are legally blind in some sense can still see, but they have severe visual impairment.

First, let’s quickly review the physiology of vision. Okay, now, the visual pathways begin in the eye. If we zoom into the wall of the eye, there's an outer fibrous layer, which contains the cornea and sclera, and helps control and focus the entry of light. So the light that passes through the cornea is directed to the lens, which in turn collects light arrays and focuses them into the retina at the back of the eye. The retina houses photoreceptors that translate light into electrical impulses, which are then carried by the optic nerve into the visual cortex of the brain. Finally, the visual cortex processes the impulses coming from both eyes, and fuses them into one clear image.

Now, common causes of legal blindness include eye conditions like cataracts, age-related macular degeneration, glaucoma, diabetic retinopathy, eye infections like trachoma, or it can be congenital. Lastly, the cause of legal blindness may also be idiopathic or unknown. Risk factors for legal blindness include being assigned female at birth or over the age of 50, as well as having a systemic disease like diabetes mellitus, or undergoing eye surgery.

Okay, so the pathology of legal blindness can have two main origins. On the one hand, it can originate from abnormalities or damage involving a structure within the eye, such as the lens or retina. If any of these structures isn’t properly functioning, the eye is not able to perceive light and images, and thus fails to translate it to electrical impulses for the brain.