EYES
Description:
Your vision is dependent on the reception of light. On the outside, there is the colored iris, a clear dome called the cornea, the pupil which allows light, the white sclera, and a thin layer of tissue called the conjunctiva. After light touches the surface of the eye, it reaches the cornea, which is in charge of maintaining focus. Behind the cornea is the aqueous humor which maintains pressure in the eye. As it passes through the pupil, it will dilate or shrink according to how much light it requires. Then, the lens will change shape to adjust focus. As the light continues onto the eyeball inside the jelly-like vitreous, it will reach the retina in the back. The retina is made of several components; blood vessels for nerve cell nutrition, the macula in the center, photoreceptors that convert light into signals (which will then be sent to the optic nerve and into the brain for comprehension), retinal pigment epithelium (RPE) beneath photoreceptors that receive excess light, and the choroid that has blood vessels.
Diseases and Conditions
Refractive Errors
These are the most common eye conditions and include things such as near-sightedness and farsightedness, called myopia and hyperopia respectively. Astigmatism is where vision is distorted regardless of distance, and presbyopia comes with age and causes a loss of focus. People with refractive errors will require glasses, contacts, or surgery.
Amblyopia
Also known as lazy eye, it is common in children and occurs when the eyes and brain do not coordinate, so one eye may have impaired vision.
Age-related Macular Degeneration (AMD)
Caused by aging, it blurs the vision of elders by affecting the macula in charge of focusing. Wet AMD is a result of abnormal blood vessel growth causing fluid leaks. Dry AMD is when the macula simply thins. AMD can be also caused by drusen, or deposits under the retina.
Strabismus
Incorrect positioning of the two eyes. It can either be crossed, called esotropia, or turned outward, called exotropia. This makes it difficult for the person to focus on one point.
Cataract
Clouding of the lens and can eventually lead to blindness. It is associated with aging and requires surgery to address it.
Glaucoma
An increase in fluid pressure in the eye rises. Open-angle slowly develops, which contrasts the sudden closed-angle glaucoma.