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A pachymeter is an instrument that measures the thickness of the cornea. Commonly used to determine whether the cornea is strong enough for procedures such as LASIK , but is typically useful in monitoring the progression of certain disorders that cause changes in the cornea, resulting in a loss of vision.


Additional keywords and misspellings:
pachymetry pachimetry cornea test lasik evaluation

A superficial vascularization of the cornea.
An inflammation involving all coats of the eye.


An excessive amount of fluid in the optic nerve head.

A wound entering an ocular structure, but not going completely through it.
A wound going completely through an ocular structure.


A test used to help diagnose Glaucoma that produces a map of the complete field of vision. Small vision changes can be detected by having the patient look straight ahead and indicate when a moving object or light is seen out of the corner of the eye. See Visual Field Test .



A surgical cataract removal method which uses ultrasonic waves to break up the existing natural lens, so it can be removed by aspiration. The incision is smaller and recovery time is faster with this method than with other cataract removal methods.


Additional keywords and misspellings:
phaco extracap cataract removal aphakia artificial lens lens removal

Sensitivity to light.
Photorefractive Keratectomy

foh-toh-ree-FRAK-tiv kayr-ah-TEK-toh-mee

Also known as PRK, A procedure in which a laser is used to reshape the front of the cornea and correct nearsightedness and astigmatism.

Phthisis Bulbi
A shrunken and atrophic globe.

Pinguecula is a thickening of the white of the eye, an irritation caused by the degeneration of the conjunctiva. It appears as a small lump and is yellowish-brown and composed of degenerated elastic tissue, occurring on either side of the cornea and often occurring in both eyes. It is usually benign in nature.


The cause of pinguecula is usually dryness and exposure to the environment. They occur more frequently in dry, dusty climates. Farmers, foresters and outside workers are especially prone to this condition.

Symptoms are slight but may be associated with burning or stinging of the eyes. Occasionally a pinguecula may become red, irritated and inflamed.Treatment with appropriate drops will clear this redness in just a few days.

Additional keywords and misspellings:
pingecula pingucula pingecila yellow

Plasmoid Aqueous
The fibrin in the anterior chamber.
Polarized Lens

POH-lah-rized lenz

Lenses designed to reduce glare caused by reflections from water, snow and road surfaces. Ideal for fishing and bright light conditions.

More than one pupil, each having sphincter muscle.
Posterior Capsulotomy

poh-STEER-ee-or kap-soo-LOT-oh-mee

Following cataract surgery, approximately 30% of the cases develop fibrotic lines or wrinkles in the capsule behind the intraocular lens implant. A YAG Laser is used to clear the center of the capsule.

Posterior Capsulotomy

Posterior Vitreous Detachment

Also known as PVD, It is the separation of the vitreus from the retina. Commonly occuring in middle age, the vitreous gel of the eye may start to thicken or shrink, and may form clumps or strands inside the eye. The vitreous begins to pull away from the back wall of the eye, causing a posterior vitreous detachment and creating flashes.

Posterior Vitreous Detachment

Posterior vitreous detachment is more common in:

  • People who are nearsighted
  • People who have undergone cataract operations
  • Those who had YAG laser surgery of the eye, or
  • Have had inflammation inside the eye.

Add'l keywords/misspellings:
vitrius detached floaters vitreus pvd posterior vitreous detachment




Presbyopia is a condition in which the focusing ability of a person's eyes has decreased to the point where vision at his reading distance becomes blurred and difficult.

Additional keywords and misspellings:
nearsighted nearsightedness nearvision

Photorefractive Keratotomy. A procedure in which a laser is used to reshape the front of the cornea and correct nearsightedness and astigmatism.
A line-less bifocal
A forward protrusion of the eyeball, usually of traumatic origin.
A conjunctival scar attached to the cornea.

ter ah gee' um

A pterygium is a raised, whitish wedge-shaped growth of tissue from the white of the eye (the conjunctiva) that extends onto the cornea. Pterygia are benign lesions that can be found on either side of the cornea. The majority of pterygia are located on the side of the eye closest to the nose.

What causes a pterygium?
More commonly, prolonged exposure to ultraviolet light (UV exposure) may contribute to the formation of a pterygium. Pterygia are more often seen in people from tropical climates near the equator, but can be found in others as well -- including those who spend a great deal of time outdoors or those exposed to dry and dusty environments. Wind, dust, smoke, dirt and air pollution can contribute to the formation of a pterygium.

What is the treatment?
If a pterygium is small but becomes inflamed, your optometrist may recommend a brief therapy of a mild steroid eye drop. If these drops are recommended, you will be monitored closely to ensure that you do not develop side effects from the use of these medications. In some cases, your optometrist may recommend surgical removal of the tissue.

Removal is advised if the pterygium is growing far enough onto the cornea to disrupt your line of vision or if they cause discomfort similar to the sensation of a persistent foreign body in the eye, or if they are constantly inflamed and irritating. Some pterygia may ultimately grow onto the cornea in such a way that they can pull on the surface of the cornea and change the focus of the eye, causing astigmatism. In these cases, removing the pterygium can correct or significantly decrease the astigmatism.

Additional keywords and misspellings:
terigeum pterigeum taragium pterygeum abnormal corneal tissue conjunctival



The drooping of the upper eyelid beyond its normal position. The ability to raise the eyelid may be compromised. Ptosis can be caused by a number of disorders and diseases, including Parkinson's Disease.




The "black center" of the eye, responsible for controlling the amount of light entering the eye. 



The Eye Encyclopedia is a collection of eye care terminology created by practicing optometrists and ophthalmologists. The information provided is not intended to be a substitute for regular medical care or to diagnose or treat any medical condition, and should be used only as a supplemental source of information. Please consult your doctor if you have any questions or concerns about your eye health.