noun. the clear front surface of the eye. It lies directly in front of the iris and pupil, and it allows light to enter the eye.


dry eye

noun. a condition in which a person doesn't have enough quality tears to lubricate and nourish the eye

Tears are necessary for maintaining the health of the front surface of the eye and for providing clear vision. With each blink of the eyelids, tears spread across the front surface of the eye, known as the cornea. Tears provide lubrication, reduce the risk of eye infection, wash away foreign matter in the eye and keep the surface of the eyes smooth and clear. Excess tears in the eyes flow into small drainage ducts in the inner corners of the eyelids, which drain into the back of the nose. Dry eyes can occur when tear production and drainage is not in balance.

Dry eyes can occur when tear production and drainage are not in balance. People with dry eyes either do not produce enough tears or their tears are of a poor quality:

  • Inadequate amount of tears: Tears are produced by several glands in and around the eyelids. Tear production tends to diminish with age, with various medical conditions or as a side effect of certain medicines. Environmental conditions, such as wind and dry climates, can also decrease tear volume due to increased tear evaporation. When the normal amount of tear production decreases or tears evaporate too quickly from the eyes, symptoms of dry eye can develop.

  • Poor quality of tears: Tears are made up of three layers: oil, water, and mucus. Each component protects and nourishes the front surface of the eye. A smooth oil layer helps prevent evaporation of the water layer, while the mucin layer spreads the tears evenly over the surface of the eye. If the tears evaporate too quickly or do not spread evenly over the cornea due to deficiencies with any of the three tear layers, dry eye symptoms can develop.


The cornea provides most of your eye's optical power. Some diseases associated with an improper functioning cornea include: 

● Dry Eye

● Keratitis

● Ulcers



noun. an inflammation and swelling of the cornea, the clear front cover of the eye

Keratitis may or may not be associated with an infection.

Noninfectious keratitis

Noninfectious keratitis can be caused by an eye injury, by wearing contact lenses too long or by a foreign body in the eye.

Infectious keratitis

Infectious keratitis can be caused by bacteria, viruses, fungi and parasites.


Keratitis can be associated with other eye conditions such as conjunctivitis (pink eye). Keratitis can cause pain, redness and blurred vision. If left untreated or if an infection is severe, keratitis can lead to serious complications that may permanently damage your vision

Wearing contact lenses increases the risk of developing infectious and noninfectious keratitis, especially if slept in them. Do not wear contact lenses longer than recommended by a doctor of optometry. Follow the cleaning regimen and do not wear contact lenses while swimming, as the chemicals and microbes in the water can cause keratitis.

  • Eye Injury—mechanical (scratch) or chemical (fumes or liquids splashed in the eye).

  • Dry eyes.

  • Overexposure to ultraviolet (UV) light, also called snow blindness.

  • Bacteria.

  • Viruses, most commonly Herpes Simplex.

  • Fungus.

  • Allergies.

  • Conditions and medications that cause a reduced immune system.

Symptoms of keratitis can include:

  • Redness

  • Pain

  • Excessive tearing

  • Blurred vision

  • Light sensitivity



noun. an open sore on the cornea

The cornea covers the iris and the round pupil, much like a watch crystal covers the face of a watch. A corneal ulcer usually results from an eye infection, but severe dry eye or other eye disorders can cause it.

Symptoms of corneal ulcers include:

  • redness of the eye

  • severe pain and soreness of the eye

  • the feeling of having something in your eye

  • tearing

  • pus or other discharge

  • blurred vision

  • sensitivity to light

  • swelling of the eyelids

  • a white spot on your cornea that you may or may not be able to see when looking in the mirror


Corneal ulcers can badly and permanently damage your vision and even cause blindness if they are not treated.