Page 96 - The Book Pi in eye

Rajesh Khanna, MD

Peripheral vision: The ability to see objects and movement outside
of, or on the periphery of, one's direct line of vision.

Photoablation: The process of removing, or vaporizing, tissue by
means of laser energy.

Photorefractive keratectomy (PRK): A type of laser vision
correction that removes the outer epithelial layer of the cornea and
reshapes it by ablating, or vaporizing, the corneal tissue one
microscopic layer at a time, using an excimer laser. Unlike with Lasik,
in which a hinged corneal flap is first made and lifted back to expose
the corneal bed, with PRK the sculpting process is on surface of the
cornea.

Presbyopia: Often confused with farsightedness, presbyopia (literally,
"old eyes") is the age-dependent need for reading glasses or bifocals,
caused by the decreasing ability of the eye's lens and surrounding
muscles to fine-tune focus.

Presbyopic Implant (PI): Synthetic inert artificial lens which when
implanted into the eye allows one to see at all distances.

Posterior Vitreous Detachment (PVD): When the vitreous jelly
liquefies and separates from the neurosensory retina. May lead to
retinal detachment.

Prescription: A series of numbers that instruct someone how to
provide a patient with the proper eyeglass or contact lens (see also
refractive error).

Punctum plugs: Used in the treatment of dry eye, this tiny collagen,
plastic or silicone plugs are inserted into the tear-drainage openings of
the eyelid to delay the drainage of natural tears so the eyes will stay
moist.

Pupil: The small black dot, or opening, in the center of the iris. The
pupil changes its diameter in response to changes in lighting.

Radial keratotomy (RK): A form of refractive surgery in which the

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