| Ablate |
| |
In surgery, to remove. |
| Ablation |
| |
The vaporization of tissue with
the excimer laser. |
| Ablation zone |
| |
The area of tissue that is removed
during laser surgery. |
| ALK |
| |
See Automated lamellar keratoplasty.
|
| Aniseikonia |
| |
A difference in imaging size between
the two eyes. |
| Anisometropia |
| |
A difference in refractive power
of the two eyes in which the variance is at least
one diopter. |
| Anterior chamber
|
| |
The fluid-filled area between the
cornea and the lens. |
| Aqueous humor |
| |
The fluid in the anterior chamber.
|
| Astigmatism |
| |
A refractive error caused by an
irregular shape of the cornea (much like a football).
Astigmatism is measured in terms of diopters,
cylinder meridian or axis. Uncorrected astigmatism
may produce ghosting or double images. |
| Automated lamellar
keratoplasty (ALK) |
| |
A procedure in which the surgeon
first creates a flap in the uppermost layer of
the cornea using a device called a microkeratome.
Then the surgeon makes an optical cut after removing
additional tissue with a second pass of the microkeratome.
|
| Axis |
| |
In ophthalmology, a line that is
the symmetrical center of a curved optical surface.
Measure of astigmatism. |
|
B
|
| BCVA |
| |
See best corrected visual acuity.
|
| Best corrected visual
acuity (BCVA) |
| |
The best possible vision a person
can achieve with corrective lenses measured in
terms of Snellen lines on an eye chart. |
| Bowman's membrane
|
| |
The non-regenerative layer of tissue
between the epithelium and the stroma (5-10 microns
thick - .005 to .01 millimeters). |
| Broad beam laser
|
| |
A medical instrument that produces
a powerful beam of light that is focused at close
range to remove corneal tissue. A broad beam laser
uses a relatively large beam diameter (from 6.0
to 8.0 millimeters) which can be manipulated to
ablate the cornea. |
|
C
|
| Center islands |
| |
A manageable complication of LASIK
related to ablation. The incidence of center islands
has been greatly reduced as more ophthalmic research
has been devoted to its contributing factors.
|
| Cornea |
| |
The outer part of the eye that
provides 70% of the eye's refractive power. The
cornea is approximately 500 microns thick (.5
millimeter) and consists of 5 layers epithelium,
Bowman's membrane, stroma, Descemet's membrane
and endothelium. |
| Cylinder meridian
|
| |
In ophthalmology, a line that is
the symmetrical center of a curved optical surface.
Measure of astigmatism. |
|
D
|
| Decentration |
| |
A complication caused by movement
of the pupil that can be corrected with an enhancement
procedure. |
| Descemet's membrane
|
| |
The layer of the cornea between
the stroma and endothelium. Five microns thick
(.005 millimeters), this membrane provides an
adhesion layer for the endothelium. |
| Deturgescence |
| |
The balance of hydration in the
eye. |
| Diopters |
| |
A measurement of refractive error.
Hyperopia is measured in terms of positive diopters.
Myopia is measured in terms of negative diopters.
The most common refractive errors ranged between
+6 to -6 diopters. |
| Dry eye |
| |
A Syndrome characterized by corneal
dryness due to deficient tear production. |
|
E
|
| Ectasia |
| |
A progressive corneal thinning
and bulging. |
| Emmetropes |
| |
People who have no refractive error.
|
| Emmetropia |
| |
The ophthalmic term for a perfect
refractive state - no nearsightedness, farsightedness
or astigmatism. |
| Endothelium |
| |
The innermost layer of the cornea.
The endothelium is one cell layer thick (5-10
microns or .005-.01 millimeters) and provides
hydration balance to maintain the cornea's transparency.
The endothelium serves three main purposes it
regulates the stroma's water content, provides
a barrier to ingress of several constituents of
the aqueous humor, and actively transports glucose.
|
| Enhancement |
| |
A secondary refractive procedure
performed after the initial one in an attempt
to achieve better visual acuity. |
| Epithelial ingrowth
|
| |
A complication of LASIK wherein
epithelial cells grow underneath the corneal flap.
|
| Epithelium |
| |
The outermost layer of cells of
the cornea. Six cells thick (20 microns), the
epithelium is the eye's first defense against
infection. |
| Excimer laser |
| |
A "cold" laser used in
refractive surgery to remove corneal tissue. |
|
F
|
| Farsightedness |
| |
See "Hyperopia" |
|
G
|
| Glare |
| |
A complication of refractive surgery
in which the patient sees additional luster around
lights. Glare is a subjective experience that
often decreases with time. |
| Ghosting |
| |
A distortion of image due to irregular
healing of the corneal surface. |
| Globe |
| |
The eyeball. |
|
H
|
| Halos |
| |
A complication of refractive surgery
in which the patient sees additional rings around
lights at night. Halos are subjective experiences
that often decrease with time. |
| Haze |
| |
A relatively rare complication
of LASIK caused by the deposition of ground substance
in the cornea. An ophthalmologist can measure
the haze response of a patient's eye under a slit
lamp, but patients' experiences of haze vary.
Outcomes for the patient include decreased night
vision, halos or loss of best corrected visual
acuity. Caused by the eye's reaction to the laser,
haze often decreases with time and is more common
with PRK. |
| Hyperopes |
| |
People who are farsighted. |
| Hyperopia |
| |
The ophthalmic term for farsightedness.
In the hyperopic eye, images are focused in back
of the retina. The hyperopic eye is often described
as being too flat or too short. |
|
I
|
| Intraocular pressure
|
| |
The pressure the fluid contained
within the eye exerts on the globe. |
| Irregular astigmatism
|
| |
A refractive error caused by an
irregular shape of the cornea in which the curve
on one side of the meridian or axis is not symmetrical
with the curve on the other side. |
|
K
|
| Keratectomy |
| |
The portion of the LASIK procedure
in which the surgeon raises a thin layer of the
cornea - creates a corneal flap - with an instrument
called a microkeratome, to expose the layer of
the cornea called the stroma. |
| Keratoconous |
| |
A rare inherited condition of the
cornea in which the cornea is steepened to the
point of being cone-shaped. |
| Keratomileusis |
| |
The carving of the cornea formerly
done with a lathe and blade, now done with an
excimer laser. |
| Keratoplasty |
| |
The replacement (transplantation)
of the cornea. Keratoplasty can be lamellar (replacement
of superficial layers) or penetrating (replacement
of the full thickness of the cornea). |
| Keratotomy |
| |
A surgical incision (cut) of the
cornea. |
|
L
|
| Lamellar keratoplasty
|
| |
The replacement of superficial
layers of the cornea with the layers of another
donor cornea. |
| Laser |
| |
An acronym for light amplification
by stimulated emission of radiation. A medical
instrument that produces a powerful beam of light
and can produce intense heat or cool vaporization
when focused at close range. Lasers are often
used in surgery to remove tissue. |
| LASIK |
| |
The acronym for laser assisted
in situ keratomileusis. The name refers the use
of a laser to reshape the cornea without invading
the adjacent cell layers. For more information,
see Step-by-Step
of the procedure. |
| Leucomas |
| |
Scars that are dense and white.
|
|
M
|
| Meibomian secretions
|
| |
Oily secretions from the eyelid
glands that supply the outer portion of tear film,
prevent rapid tear evaporation and tear overflow.
|
| Micron |
| |
One thousandth of a millimeter.
The symbol for a micron is. |
| Microkeratome |
| |
The instrument a surgeon uses to
create the corneal flap in the uppermost layer
of the cornea during the LASIK procedure. |
| Monovision |
| |
The purposeful adjustment of one
eye for near vision and the other for distance
vision accomplished with either corrective lenses
or surgery. |
| Myopes |
| |
People who are nearsighted. |
| Myopia |
| |
The medical term for nearsightedness.
Eye is too steep, too long, image is focused in
front of the retina. |
|
N
|
| Nearsightedness
|
| |
See "Myopia" |
| Nebulas |
| |
Scars that are translucent. |
| Nomogram |
| |
A surgeon's adjustment to the laser's
computer calculation to further refine his or
her own results. |
|
O
|
| Off label use |
| |
The permissible use of an approved
drug or instrument in a way that has not been
specifically sanctioned. |
| Optic nerve |
| |
The millions of optical nerve fibers
connecting to the eye and terminating in the brain
where images are created and processed. |
| Overcorrection |
| |
The result achieved when the change
to refractive error exceeds the attempted correction.
|
|
P
|
| Pachymetry |
| |
The process of measuring corneal
thickness, usually using an ultrasonic probe.
|
| Photorefractive
keratotomy |
| |
A procedure involving the removal
of the surface layer of the cornea (epithelium)
by gentle scraping and use of a computer-controlled
excimer laser to reshape the stroma. Acronym is
PRK. |
| Plano |
| |
Characterized by no refractive
error. |
| Practice of medicine
|
| |
A regulatory body's allowance of
practitioners to make decisions to best serve
their patients. |
| Presbyopia |
| |
The natural deterioration of near
vision caused by loss of flexibility in the eye's
lens as one ages. |
| PRK |
| |
The acronym for photorefractive
keratotomy. A procedure involving the removal
of the surface layer of the cornea (epithelium)
by gentle scraping and use of a computer-controlled
excimer laser to reshape the stroma. |
| Ptosis |
| |
Droopy eyelid. |
|
R
|
| Radial keratotomy
|
| |
A surgical procedure designed to
correct myopia (nearsightedness) by flattening
the cornea with incisions. The procedure is called
a radial keratotomy because the incisions resemble
the spokes in a wheel. Acronym is RK. |
| Refraction |
| |
The bending of light wave as they
pass from one medium to another. |
| Refractive surgery
|
| |
Any surgical procedure that attempts to decrease
the patient's refractive error. Typically the
surgeon alters the shape of the cornea in order
to change the angle at which an image is projected
onto the retina. |
| Regression |
| |
A backwards shift from the initial
visual outcome. |
| Regular astigmatism
|
| |
A refractive error caused by an
irregular shape of the cornea (usually a football
shape) in which the curvature is symmetrical across
one or more meridians or axes. |
| Retina |
| |
Light processing membrane; converts
light into electrical impulses that are transmitted
to the optic nerve. |
| RK |
| |
Acronym for radial keratotomy.
A surgical procedure designed to correct myopia
(nearsightedness) by flattening the cornea with
incisions. The procedure is called a radial keratotomy
because the incisions resemble the spokes in a
wheel. |
|
S
|
| Slit lamp |
| |
Table-top microscope for examining
the eye. |
| Snellen chart |
| |
An eye chart used to test a patient's
vision. |
| Snellen line |
| |
A line of same-sized letters on
an eye chart that is used to test a patient's
vision. |
| Spot scanning laser
|
| |
A medical instrument that produces
a powerful beam of light that is focused at close
range to remove corneal tissue. Spot scanning
lasers use radar technology to track the eye's
movement. |
| Stroma |
| |
Thickest part of the cornea (450-600
microns - approximately .5 millimeters). Between
Bowman's membrane and Decemet's membrane. |
| Symmetry of refractive
error |
| |
The refractive error in both eyes
are close to the same value. |
|
T
|
| Tear film |
| |
A very thin film of water and other
chemicals riding on top of the epithelium that
lubricates the front of the eye. |
Topical proparacain hydrochloride |
| |
Anaesthetic eye drops. |
|
U
|
| UCVA |
| |
See uncorrected visual acuity.
|
| Uncorrected visual
acuity (UCVA) |
| |
A person's vision without corrective
lenses measured in terms of Snellen lines on an
eye chart. Acronym is UCVA. |
| Undercorrection
|
| |
The result achieved when desired
change in refractive error is not fully achieved.
|
|
V
|
| Vitreous humor |
| |
The gel-like fluid in the main
cavity of the eye behind lens and pupil. |
