01392
A - Z of Eyes & Focusing
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A
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.
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 dioptre.
Anterior chamber
The fluid-filled area between the cornea and the lens.
Aqueous humour
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 dioptres, cylinder meridian or axis. Uncorrected astigmatism may produce ghosting or double images.
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.
Bladeless
Refers to the creation of a corneal incision without the use of a metal microkeratome blade. The Ziemer Femtosecond LDV Laser is a bladeless technology that uses a laser to create the corneal flap in Step One of LASIK.
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) that can be manipulated to ablate the cornea.
C
Centre 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 (0.5 millimeter) and consists of 5 layers - epithelium, Bowman's membrane, stroma, Descemet's membrane and endothelium.
Corneal Flap
A circular, hinged portion of the outer layer of the cornea, lifted in Step One of LASIK surgery. The corneal flap allows the surgeon to access the inner portion of the cornea in Step Two. Although LASIK complications are rare, most of those that occur result from improperly formed flaps.
Cylinder meridian
In ophthalmology, a line that is the symmetrical centre of a curved optical surface. Measure of astigmatism.
