The human eye is a major sensory organ that reacts to light and transmits visual information to the brain. Contrary to popular belief, the eye is not a perfect sphere—it consists of two major parts that are fused together. The part in front is known as the cornea, which is transparent and has a curved feature. It is directly connected to a larger unit called the sclera, which is the white part of the eyes. These two parts are connected together by a ring of tissue known as the limbus.
The iris, which is located in the center of the eye, is perhaps the most distinguishing feature of this sensory organ. A colored circular structure, the iris can be brown, grey, blue, and green in humans.
At the center of the iris is the pupil, which is often black in color and is responsible for controlling the amount of light that enters the eye. This part functions like a camera aperture in a way that it lets certain amount of light in. The sphincter and dilator muscles of the iris control this aperture-like function.
The human eye’s reaction to light and visual information is quite complex. As light enters through the cornea at the front of the eye, the pupil screens the amount of light coming in. The light then passes through the ciliary muscles, which controls the movement of the lenses. Light will then fall into the retina and converted into electrical signals. These signals are carried by the optic nerves to the brain, which is responsible for interpreting the electric information it receives.
The human eye, a very sensitive organ, is protected by the eyelids and the eyelashes.
Common Eye Problems and Conditions
Eye irritation - This is the most common eye problem experienced by people of all ages and genders. It can come in the form of burning, itching, or stinging sensation. It is often accompanied by symptoms such as dryness, excessive tearing, discomfort, eye fatigue, pain, inflammation of the eyelids, soreness, and redness.
Presbyopia - Common in people over the age of 40, this condition involves the inability to see close objects and small printed text clearly.
Cataracts - This condition involves the growth of cloudy areas in the lenses of the eyes, preventing light from getting into the eye easily, which results in limited vision.
Glaucoma - This condition develops due to pressure build-up in the eye, which can damage the optic nerves and limit vision.
Conjunctivitis - This condition involves the inflammation of the tissue lining the cornea and the eyelids. Conjunctivitis is commonly known as “pink eye”.
- Retinal detachment - This is an emergency situation in which the retina pulls away from its normal position separating from blood vessels that provides nourishment and oxygen.
Common Eye Surgeries and Procedures
Cataract surgery - This surgery, which is often performed on an outpatient basis and under local anesthesia, involves removing the damaged lens inside the eye and replacing it with intraocular lens or IOL to restore clear vision.
LASIK - This procedure corrects the vision of people with nearsightedness, farsightedness, or astigmatism. It uses laser technology that reshapes the inner cornea.
Photorefractive keratectomy or PRK - This procedure corrects nearsightedness, farsightedness, and astigmatism, and is less invasive compared to LASIK.
Pneumatic retinopexy – This procedure is performed in cases of retinal detachment. In involves the use of bubble of air or gas in the vitreous cavity to push the retina against the walls of the eye.