ABLATION:
The process of removing tissue by applying
energy pulses from the excimer laser onto
the surface of the cornea, thus reshaping
the focusing surface of the eye.
ASTIGMATISM:
A condition in which the cornea is "out of
round". The surface is not spherical like
the surface of a standard ball but more angular
like the surface of a football.
BCVA (Best Corrected Visual Acuity):
Usually refers to the best a person can see
on the standard eye chart with their most
accurate refraction in glasses or the phoropter
testing equipment.
CORNEAL ABRASION:
A surface defect involving the most
superficial layer of the cornea, known as the
epithelium. These defects can be caused by contact lenses,
fingernails, tree branches, etc., or induced
surgically, as in the PRK and LASEK
procedures. Corneal abrasions typically heal spontaneously
over the next few hours or days, as the
epithelium has the ability to regenerate.
EMMETROPIA:
The term applied to the vision status of an
individual when the eye is properly shaped
and has "perfect" distance vision without
correction.
ENHANCEMENT:
A term used to describe a re-operation or
re-treatment in refractive surgery. Primarily
used in association with incisional surgeries,
such as radial keratotomy and astigmatic keratotomy,
it is used when there is still correction
needed after the initial operation.
EXCIMER LASER:
An ultraviolet-based laser that generates
energy pulses that when directed by computer
control can be used to reshape the surface of
the cornea. This technology was originally designed for
etching computer chips. It was approved by
the FDA for use in the correction of nearsightedness
in 1995.
FLUCTUATING VISION:
A transient condition following most refractive
surgery in which the patient’s vision
may vary a bit, day to day, until stabilization.
In LASIK this is usually about two weeks.
HAZE:
A type of healing reaction that causes cloudiness
in the cornea following PRK or LASEK. It is related
to the loss of Bowman’s Layer in these
procedures.
HYPEROPIA (Farsightedness):
Refractive error related to either a flat
cornea or short eye length. The optical effect
is that distant objects tend to be clearer
than near objects.
INTRACORNEAL RINGS:
Approved by the FDA in April 1999, these small
acrylic arc-shaped implants are fed into tunnels
created in the cornea, affecting a shape change
in the cornea. Currently, they are used for
mild degrees of nearsightedness only. In case
of complication, they are theoretically reversible.
INTRAOCULAR
LENSES (IOL's):
Small lenses made of silicone, plastic, or
acrylic material that are placed inside the
eye following cataract removal. Some newer
forms of these lenses are under FDA investigation
for use in highly nearsighted and highly farsighted
patients.
LASER IN-SITU KERATOMILEUSIS (LASIK):
A surgical procedure in which a microkeratome
is used to create a surface layer of corneal
tissue (flap) that can be reflected out of
the way so that a laser re-surfacing treatment
may be applied underneath. The flap is returned
to its original position and heals very quickly.
LASER
SUB-EPITHELIAL KERATOMILEUSIS (LASEK):
A surface laser procedure in which the epithelial layers are loosened as a single sheet, moved to the side, and the laser treatment is placed immediately on the underlying
surface (Bowman's membrane). The epithelial layer is then
repositioned to facilitate in the healing process.
Also known as Advanced Surface Ablation (ASA)
or Epi-LASEK.
MICROKERATOME:
A surgical instrument used to cut the corneal
flap in the LASIK procedure. There are several
manufacturers and different methods by which
they work.
MONOVISION:
The process of treating one eye (mono) for
distance and leaving one eye somewhat nearsighted
for reading. This allows the greatest freedom
from glasses use but also has the negative
of reduced depth perception and the reduction
of acuity that comes from two eyes adding
image information together.
MYOPIA (Nearsightedness):Refractive error related to either
a steep, or pointed cornea, or an eye of greater
than usual length. The optical effect is that
near objects are clearer than distance ones.
NIGHT VISION PROBLEMS:
Many individuals complain of poor vision in
the dark. This is essentially normal since
the human eye is not designed for high acuity
night acuity. However, some of us have worse
night vision than others. Unusual enlargement
of the pupil in the dark, in some people,
may contribute to this problem.
NOMOGRAMS:
Tables created by surgeons to adjust the laser
for individual patient treatments. Based on
the major variables of age and amount of correction
required.
OVERCORRECTIONS:
The term applied to the situation when a refractive
surgery treatment produces a change that is
larger than that planned. This can happen
in treatments for nearsightedness, farsightedness
or astigmatism. Overcorrections are related
to unusual healing responses, errors in
preoperative
measurements or nomogram use. Overcorrections
can usually be remedied by the application
of another, reversing type treatment.
PHOTOREFRACTIVE KERATECTOMY (PRK):
A surgical procedure using the excimer laser
to reshape the front surface of the eye, the
cornea, to correct refractive errors. In this
procedure, the laser pulses are applied directly
through the surface of the cornea after
removing the most superficial layer, the
epithelium, which then regenerates to cover
the treated area over the next few days.
PRESBYOPIA:
This is the condition, faced by all of us as we age, that causes us to require
reading glasses for near focus. This is due
to the progressive weakening of our focusing
muscles, which begins in our youth and culminates
in reading glasses, typically in our forties.
RADIAL KERATOTOMY (RK):
A surgical procedure used to correct mild degrees
of nearsightedness and astigmatism. This procedure
involves making a series of small incisions
in the cornea with a diamond knife to cause
the cornea to change shape. RK has largely
been abandoned in the United States.
REGRESSION:
This is the term applied to the situation
when, following surgery for a refractive error,
there is a tendency for the eye to shift somewhat
back towards its original condition during
the healing process. It is usually a relatively
minor shift and can be adjusted with a re-treatment
procedure.
RETINA:
The lining of the back of the eye upon which
the images focused by the front of the eye
fall. It is very specialized and serves as
a “living film” to process the
light impulses into the images that we "see".
TOPOGRAPHY:
A digital image processing device used to
measure the surface contour of the cornea. It is used
before refractive surgeries to identify certain
individuals with conditions making refractive
surgery an unacceptably unpredictable undertaking.
It can also be used after surgery to identify
unusual cornea shapes during the healing process.
UNDERCORRECTION:
The term applied to the situation when a refractive
surgery treatment produces a change that is
less than that planned. This can happen in
treatments for nearsightedness, farsightedness
or astigmatism. Undercorrections are related
to unusual healing responses, errors in pre-operative
measurements or nomogram use. Undercorrections
can usually be remedied by the re-treatment
process.
WAVEFRONT
SENSING:
A technology designed to improve the optical quality of lens elements used in astronomical telescopes. A new
addition to vision correction surgery used to attempt to reduce the aberrations present in the human eye.
