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Glossary of Lasik Laser Eye Surgery Related Terms - S-Z

Numbers 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

Saline Solution
A sterile salt solution used in cleaning, rinsing, and sometimes storing of contact lenses.
Sands of Sahara
See Diffuse Lamellar Keratitis.
Schlemm's Canal
The passageway for the aqueous fluid to leave the eye.
The tough, white, outer layer (coat) of the eyeball. With the cornea, it protects the entire eyeball.
Scleral Shell
Flush fitting thin artificial eye usually fit over phthisis bulbi.
Scotopic Pupil Size
The size of a pupil under low light conditions similar to light in a theater or during night driving.
An area of partial or complete loss of vision surrounded by an area of normal vision.
Secondary Implant
If no lens was placed in the eye at the time of cataract removal surgery, then a secondary procedure to implant an intraocular lens may be completed later.
See Society for Excellence in Eyecare.
Shirmer Test
Tiny strips of filter paper are placed in the patient's eyes just under the lids. After five minutes the distance the tears have stained the paper is measured. The greater the distance, the higher the natural tear production.
Side Vision
See peripheral vision.
Slit Lamp
A microscope using various magnifications combined with a strong light that can be focused into a slit for examining the eye.
Snellen Visual Acuity Test
The white chart with the big black E at the top and lines of letters that become increasingly smaller. The Snellen Test is one of many tests used to determine visual acuity. The term 20/20 means that the patient can see an item 20 feet away with the same clarity that a normally sighted person can see an item 20 feet away. 20/40 means that the patient can see an item 20 feet away with the clarity that a normally sighted person can see an item 40 feet away. This is worse than normal vision. 20/10 means that the patient can see an item 20 feet away with the same clarity that a normally sighted person can see an item 10 feet away. 20/10 is better than normal vision.
Society for Excellence in Eyecare
Ophthalmologist membership organization.
See Sands of Sahara.
Term meaning spherical refractive error of hyperopia or myopia.
A split-beam excimer laser is a broad-beam laser with an adjustable iris to control the amount and location of the energy that is applied to the cornea. See also flying-spot laser.
See Surgical Reversal of Presbyopia
More commonly known as crossed-eyes, is a vision condition in which a person cannot align both eyes simultaneously under normal conditions. One or both of the eyes may turn in, out, up or down. An eye turn may be constant; when the eye turns all of the time. Strabismus may be intermittent; turning only some of the time, such as, under stressful situations or when ill. See Strabismus Details.
A known complication of refractive surgery that causes images from light sources to blur with spikes radiating out from the center. Starbursts also occur naturally without refractive surgery.
The ability to perceive three-dimensional depth due to the distance between a person's two eyes.
A large class of pharmaceutical agents that chemically resemble cholesterol. Two better known types are anabolic steroids often used in athletics, and glucocorticoid steroids that are used to reduce inflammation.
Stiles-Crawford Effect
The Stiles-Crawford effect (discovered in 1933) describes angular dependence of retinal sensitivity. Rays which enter the pupil near its center, which are parallel to retinal receptors, are more effective than oblique rays which enter the pupil near its margins. So, the light passing through the periphery of the pupil is less efficient at stimulating vision than the light passing near the center of the pupil. It is believed that photoreceptors act as light pipes, and more light gets down if it enters straight down (through the center of the cornea), rather than at a large angle (through the periphery of cornea).
Wrinkles in the corneal flap created for Lasik. There are two kinds, macro striae and micro striae. See Striae Flap Wrinkle Details
Thickest and central layer of cells in the cornea.
Seborrheic Dermatitis
Seborrheic Dermatitis may involve the presence of somewhat greasy flaking involving the area around the eyes, nose, presenting with crusts, scales, itching and occasionally burning, and may also be found on the scalp, ears and torso. Although closely related, it does not usually involve red bumps as in Rosacea. See Seborrheic Dermatitis Details.

Surgical Reversal of Presbyopia

A general term used for many different techniques that attempt to cure presbyopia. To date, none of these techniques have been proven to be safe, effective, and predictable. There are, however, surgical techniques that offer a "work around" the symptoms of presbyopia, including monovision.
Upper eyelid depression.
Ophthalmic equipment company.
Sunrise Technologies
Ophthalmic equipment company.
Upper, as in upper eyelid.
The inability to perceive all of part of objects in the field of vision of one eye.
Surface Ablation
Any surgical procedure that ablates tissue at the surface of the cornea, rather than under a Lasik or Bladeless Lasik stromal flap. PRK, LASEK, and Epi-Lasik are all surface ablation techniques. Several studies have shown that surface ablation techniques provide better refractive surgery outcomes than Lasik or Bladeless Lasik, for patients who are appropriate candidates for both types of surgery. T
See Tear Break Up Test
Tear Break Up Test
A test that determines the quality of the tears on the eye. The doctor observes the tear film under the microscope while the patient avoids blinking until tiny dry spots develop. The longer the amount of time that passes before the tear film breaks up, the more stable the tear film. A good value is more than 10 seconds.
Toward the ear.
A procedure for the measurement of the fluid pressure inside the eye (intraocular pressure). One of the tests for glaucoma.
Ophthalmic equipment company.
Topographic Supported Customized Ablation
Abbreviated as TOSCA, a system to use a topographical mapping system to guide the laser during refractive surgery.
To measure the high and low areas of a plane. See corneal topography.
A contact lens that is designed to correct sphere and astigmatism. A toric lens is weighted on the bottom so it will maintain the same axis position of the astigmatic correction.
Is the acronym for Topographic Supported Customized Ablation. This means using a topographical mapping system to guide the excimer laser ablation.
Trabecular Meshwork
The spongy, mesh-like tissue near the front of the eye that allows the aqueous fluid to flow to Schlemm's canal then out of the eye through ocular veins.
Transition Zone
The area of laser ablation that changes for the full correction of the central ablation zone optical ablation zone to the original surface depth of the cornea.
Corrective lenses that have three powers of correction. Typically the majority of the lens is corrected for distance vision while a small area is corrected for near vision and another small area is corrected for middle vision. Trifocals and bifocals are normally prescribed for individuals with presbyopia.
See Uncorrected Visual Acuity.
Procedures using sound waves to measure certain portions or detect abnormalities within the eye. See A Scan and B Scan.
Ultraviolet Radiation
Radiant energy with a wavelength just below that of the visible light. UV-c is the shortest wavelength at 200-280nm and is absorbed by the atmosphere before reaching the surface. Extremely damaging to living tissue. UV-b, at 280-315nm is "burning rays" of the sun and is damaging to most living tissue. UV-a, at 315-400nm is "tanning rays" of the sun and is somewhat damaging to certain tissues. UV radiation has been described as a contributing factor to the processes that results in ARMD, cataracts, and causes exposure keratitis.
Abbreviation meaning 10 to the -6 power meter.
Uncorrected Visual Acuity
The best vision measurement taken without the use of glasses or contact lenses.
A complication of refractive surgery where the expected amount of correction is less than desired. Undercorrection often occurs where healing regresses more vigorously than predicted.
Uvea, Uveal Tract
The middle coat of the eyeball, consisting of the choroid in the back of the eye and the ciliary body and iris in the front of the eye.
Variable Spot
This is a method of applying excimer laser energy. Rather than applying all excimer energy in a broad-beam across the entire ablation area, or with a very small flying spot of excimer energy applied in rapid succession at different locations across the ablation area, the energy is applied in variable spot sizes across the ablation area.
Visian ICL
P-IOL manufactured by STAAR Surgical. See Visian ICL Details.
Vector Vision
Ophthalmic equipment company.
Vision Therapy
A treatment process for the improvement of visual perception and/or coordination of the two eyes for efficient and comfortable binocular vision (orthopedics, vision training, and eye exercises).
Visual Acuity
Clearness of vision. The ability to distinguish details and shapes of objects; also called central vision.
Visual Axis
The central area of the cornea, pupil, and lens that light passes through to reach the retina and be "seen".
Visual Field
The area or extent of space visible to an eye in a given position of gaze. The central visual field is directly in front and the target at which we are looking. The peripheral visual field is that which we perceive in our "side vision". The fields of each eye partly overlap.
Ophthalmic equipment company. 
Involving the vitreous humor, retina, or both.
Vitreous Humor
The transparent, colorless mass of gel that lies behind lens and in front of retina.
See Wavefront Supported Corneal Ablation
Wave Length
The distance between the top of one wave and the top of the next wave. The length of one complete wave of the argon fluoride excimer laser is 193 nm. This wavelength is in the far ultraviolet end of the electromagnetic spectrum.
A technology used in optics that is able to determine and measure high order aberrations. These aberrations directly relate to an individual's quality of vision.

Conventional eye examinations can detect two types of error on the cornea - spherical (myopia and hyperopia) and cylindrical (astigmatism). Wavefront diagnostic can detect an infinite set of ocular aberrations called The Zernike polynomials, but in ophthalmology discussion has generally been limited to the first 15 or so.

The wavefront sensor system includes a fixation target, an input laser beam that generates a point light source, a wavefront sensor that measures the slope of the exiting wavefront, and software that will determine the characteristics of the excimer ablation.

The visual fixation target assists the patient in maintaining view, direction and accommodation during the wavefront measurement. While the patient fixates, a laser beam is shined into the eye. The light is reflected from the retina back through the pupil, and the wavefront of the light leaving the pupil is relayed to the wavefront sensor. The wavefront gets distorted by the refractive properties in the human eye.

When the laser beam enters the eye, it has a flat wavefront. In theory, a perfect human eye would reflect back a beam with its wavefront still flat. But in a normal human eye — after the beam of light has traveled through an imperfect crystalline lens, an irregular cornea and the other ocular media — the flat wavefront has become irregular. Think of a square grid being projected in and a wavy grid reflecting out. Detailed Custom Wavefront Lasik Information.
Wavefront Supported Corneal Ablation
Trade name of the Carl Zeiss Meditec WASCA aberrometer and the MEL 70 or MEL 80 excimer laser system when used for wavefront guided excimer laser ablation for Lasik, Bladeless Lasik, PRK, LASEK, and Epi-Lasik.
Ophthalmic equipment company.
Welch Allyn
Ophthalmic equipment company. 
With-the-rule Astigmatism
"With the rule" astigmatism has an axis of about 180 degrees (when Rx is written in minus cylinder form). "Against the rule" astigmatism has the axis at about 90 degrees.

Both forms are common. Nevertheless, when looking at population norms, "with the rule" is more common in young adults while "against the rule" is more common in older adults.
YAG Laser
YAG is an abbreviation for neodymium yttrium-aluminum-garnet, the material used generate a short pulsed, high-energy light beam in the infra red wavelength of 1064 nm. The YAG laser is a surgical instrument that can be precisely focused by computer to cut, photovaporize, or fragment tissue. The YAG laser is used to treat posterior capsular opacification; a clouding of the remaining capsular tissue that develops postoperatively in as many as 75% of cataract removal operations. The tissue is vaporized with carefully controlled pulses of the YAG laser, and the surgery is performed on an outpatient basis. The common misconception that "lasers" are used to remove cataracts occurs because post-cataract patients eventually require YAG laser capsulotomy.
See Zernike Polynomial.
Zernike Polynomial
Zernike polynomials are mathematical blueprints of ocular aberrations measured with wavefront technology. Each Zernike polynomial, called a mode, describes a certain type of geometric shape, a certain three-dimensional surface. The second-order Zernike terms represent the conventional aberrations defocus (spherical correction) and astigmatism. Zernike aberrations above the second order are called higher order aberrations. The third-order Zernike terms are coma (a wavefront shape with twofold symmetry) and trefoil (a wavefront shape with threefold symmetry). The fourth order Zernike terms include spherical aberration and four other terms, and so on. The Zernike polynomials are an infinite set, but in ophthalmology discussion has generally been limited to the first ten or so.
The brand name for wavefront guided custom ablation on the Bausch & Lomb Technolas excimer laser.
The fibers that hold the lens suspended in position and enable it to change shape during accommodation.

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