Glossary as it applies to the eye and refractive surgery
Aberration - Focusing errors of the eye. Glasses correct lower order aberrations such as sphere, cylinder and axis.
Aberrometer - A device that such as the LADARWave™ that measures lower and higher order aberrations.
Ablate - To remove
Ablation - Removal of corneal tissue during excimer laser vision correction.
Ablation depth - The depth of tissue removed during excimer laser vision correction.
Ablation zone - The area of corneal tissue removed during excimer laser surgery.
Accommodation - The ability of the eye to change its focus from distance to near.
Acuity - Clearness as in visual acuity. The most commons method of measuring vision is the Snellen Visual Acuity.
Acular® - Ketorolac Tromethamine-non steroidal anti-inflammatory eyes drops used after PRK/LASEK to reduce pain. Also, used to control inflammation after cataract and other ocular surgery.
AK - Abbreviation for Astigmatic Keratotomy.
Alcon - Ophthalmic Equipment and drug company. LADARVision® 4000 and CustomCornea® are their products.
ALK - Abbreviation for Automated Lamellar Keratoplasty.
Allergan - Ophthalmic drug company
Amblyopia - Poor vision due to lack of development of the visual system to the brain. The eye structure and function is normal. Lay term is lazy eye.
Ametropia - The presence of a refractive error in the eye such as myopia, hyperopia, or astigmatism.
AMO - Advanced Medical Optics. Ophthalmic equipment and device company.
Anisokonia - A difference of the image size on the retina of each eye. It is due to anisometropia.
Anisometropia - A difference in the refractive error of two eyes.
Anterior chamber - The area between the cornea and lens filled with aqueous humor.
Antibiotic Medication - A drug used to treat or prevent infection. It is commonly used after refractive, cataract, or other ocular surgery.
Anti-inflammatory Medication - A drug that reduces inflammation caused by surgery, trauma or disease. It is commonly used after refractive, cataract, or other ocular surgery.
Aphakic - Not having a lens. This was the condition before IOL were inserted after cataract surgery.
Argon laser - Laser light produced from argon gas. The main wavelengths are 488.0 nm blue and 514.5 nm pea green lights, but nine separate wavelengths in the blue-green visible light spectrum are produced
Astigmatic Keratotomy - A procedure use to correct astigmatism by making an incision into the cornea.
Astigmatism - A focusing error that results in blurred distant and/or near vision. This is often caused by the cornea being oval like a football rather than spherical like a volleyball. The amount of astigmatism you have will appear in the second number of most glasses prescriptions i.e. -4.00 –1.00 x 30o or –5.00 + 1.00 x 120o. In both cases the astigmatism is one diopter. These prescriptions are equivalent and differ in the format written. The first is written in minus cylinder and the second in plus cylinder.
Autoimmune Disease - A condition where the immunological system of the body attacks itself and results in inflammation or swelling of parts of the body, such as muscles, joints, and blood vessels. You should discuss any history of this condition with your doctor before having excimer laser surgery.
Automated Lamellar Keratoplasty - A microkeratome is used to create a flap in the cornea followed by a second power cut which corrects the refractive error. The combination of the flap creation with the precise ablation of the excimer laser for the power cut is LASIK.
Axis - In ophthalmology, the direction of the astigmatism.
Bandage Contact Lens - A soft contact lens placed on the cornea after surgery to make it more comfortable and to help in healing.
BCVA - Abbreviation for Best Corrected Visual Acuity.
Best Corrected Visual Acuity - The best possible vision with glasses when measured with Snellen Visual Acuity.
Binocular Vision - The use of both eyes together for depth perception and stereoscopic vision. Not all people have binocular vision.
Biometry Measurement - of the dimensions of the eye and its internal structures. Most commonly, the information is used to determine the IOL power for cataract surgery and refractive lensectomy. Pachymetry is measurement of the corneal thickness of the eye by similar techniques for refractive surgery.
Broad beam laser - Laser beams can range from 9 millimeters to less than 1 millimeter in size. The first excimer lasers were broad beam and used a laser beam of 6 to 8 millimeters is diameter. Shutter mechanisms and slits are used with some of these lasers to control the size and dimensions of the laser beam.
Calibration - The process of measuring and setting the laser to the needed energy for accurate tissue removal. Some machines sculpt a PMMA plastic button to be measured by optical instruments, and others employ a 1 micron thick foil as a method of calibration.
Cataract - A clouding of the lens of the eye. Vision becomes blurred as the cataract progresses. About half of the people by the age 55 over have cataracts.
Cataract Surgery - The surgery to remove cataracts. More than 2 million cataract surgeries are performed in the United States.
Central islands - A
manageable complication of excimer laser vision correction where the laser beam
fails to remove a portion of cornea- usually in the center of the area to be
removed. If one views the concave area of the ablation like a lake one can imagine
an island sticking up in the center- the visual symptoms would be monocular
double vision or distortion- just as you would expect if there were an irregularity
in the surface of your glasses. This has largely been prevented with advanced
technology excimer lasers.
Chiron - Manufacturer of excimer laser Technolas 217A excimer laser.
CIBA Vision Ophthalmics - Ophthalmic Equipment and Drug Company
Collagen Vascular Disease - A condition that may result in inflammation or swelling of parts of the body, such as muscles, joints, and blood vessels. Examples are lupus and rheumatoid arthritis. You must inform you surgeon if considering laser vision correction surgery.
Concave lens - A lens with a hollow shape like the inside surface of a ball. Concave lenses are - (minus) power lenses and are used to correct myopia or near-sightedness.
Conjunctiva - The delicate mucous membrane that lines the eyelids and covers the white surface of the eye. The conjunctiva joins the eyeball at the edge of the cornea (limbus). Contradictions Any special condition that results in the treatment not being recommended.
Contrast Sensitivity - a measure of the ability of the eye to detect small lightness differences between objects and the background in daylight and in dim light. For example, black lines on a gray background are easier to see than gray lines on a gray background. Objects in daylight are also easier to see than in dim light. Contrast sensitivity testing is a way to determine how well patients can see in poor contrast conditions such as very dim light, rain, snow, and fog. Contrast sensitivity may be reduced after excimer laser vision correction.
Convex lens - A lens with a bulging surface like the outer surface of a ball. Convex lenses are +(plus) power lenses and are used to correct hyperopia or far sightedness and for reading glasses as needed in presbyopia.
Cornea - The transparent front window of the eye. It provides 70% of the eye’s refractive power. It is approximately 500 microns in thickness. Its thickness is an important factor in laser vision surgery. There must be adequate corneal tissue for the ablation zone and depth require for the refractive error and pupil size. The cornea can be considered to have 5 layers:
- the corneal epithelium,
- Bowman's layer,
- corneal stroma,
- Descemet's layer, and
- the corneal endothelium.
Corneal endothelium - The inner layer of cells on the inside surface of the cornea. It maintains the clarity of the cornea by removing fluid from it.
Corneal epithelium - The outer surface layer of the cornea, like the epidermis or outer layer of the skin. This layer is removed in PRK and moved aside in LASEK.
Corneal Flap - A thin slice of tissue on the surface of the cornea made with a microkeratome at the beginning of the LASIK procedure or with the Intralase during the IntraLASIK™ procedure. This flap is folded back before the laser shapes the inner layers of the cornea.
Corneal haze - An opacification or cloudiness of the normally clear cornea. Any build up of inflammatory infiltrates (white blood cells), extra moisture, scar tissue, or foreign substances (like drugs) can cause a clouding of the cornea. Most types of haze will disappear with time or drug treatment. Rarely, a permanent haze or scars can form.
Corneal topography - A detailed colored map of the front surface of the cornea. It is used to detect abnormalities of the surface contour and curvature of the cornea. It a very important test used to diagnosis conditions, such as keratoconus, which can be a contraindication to excimer laser surgery.
Corneal swelling - An abnormal fluid build-up in the cornea. This condition is usually temporary with no significant effect on vision.
Corneal wrinkle - Usually a temporary appearance of fine white lines in the cornea due to swelling. They should be removed if persistent and affecting vision.
Conventional LASIK - LASIK surgery that uses and eyeglass prescription to plan the surgery.
CustomCornea® - The trade name for LADARVision® 4000’s wavefront guided custom ablation.
Custom Lasik - Wavefront guided custom laser vision correction such as CustomCornea®
Decentration - In perfect centration the center of the excimer laser corneal ablation exactly coincides with the center of the visual axis and/or pupil. This is like looking through the very center of your spectacle lens. If you look through the periphery of your lens you might end up seeing partly through the lens and partly through the edge of the lens- this is decentration. Decentration can cause various symptoms including edge glare or even monocular double vision. Other factors such as the normal size of the pupil, whether it is dark out (your pupil will enlarge) or the size of the excimer laser ablation zone will affect the severity or presence of symptoms. This is very rare with the active tracking lasers.
Deturgescence - The balance of hydration in the eye.
Diplopia - Double vision or seeing double usually with both eyes open as in binocular diplopia, but can be with only one eye as in monocular diplopia.
Diopter - It is the unit of measurement for optical lenses use to correct the refractive error of an eye. It is used to describe the amount of nearsightedness, farsightedness, and astigmatism. A one diopter lens will focus parallel light rays 1 meter from the lens and a two diopter lens will focus 0.5 meter from the lens. A plus ( + ) 1.0 diopter lens is convex and will converge the light rays so they focus as a visible image 1 meter past the lens. A minus ( - ) 1.0 diopter lens is concave and will diverge or spread light. The minus lens will not actually focus as a visible image on an optics table. Its image is known as a virtual image and if the diverging rays were followed to their point of origin they would focus 1 meter in front of the minus lens. Most eyes are between +6.0 and –6.0.
Distortion - In refractive surgery, an aberration in the optical systems resulting in glare, haloes, shadowing, ghost images and lack of crispness of vision.
Dry Eye - A syndrome characterized by corneal dryness due to decrease in tear production. It is more common in women and its incidence increase with age. It can occur as a complication of refractive surgery.
Ectasia - A progressive thinning and budging of the cornea and can occur as a very rare complication of excimer laser vision correction surgery. This occurs in keratoconus.
Emmetropia - Normal distance vision without glasses. The usual goal of refractive surgery.
Endo - A prefix meaning within or inside.
Endophthalmitis - An inflammation within the eye. Inflammation may be caused by organisms such as bacteria or may be sterile as in immune disorders. It is complication of intraocular surgery such as cataract surgery. It can be treated with surgery or injection of intraocular antibiotics if caught early.
Enhancement - A subsequent laser treatment made to refine or improve the original visual result. It is important to appreciate that although refractive predictability is excellent at lower planned corrections, that predictability is reduced at higher corrections. Higher corrections and wider optical zones require deeper sculpting and consequently undercorrection and overcorrection are more common. Enhancement treatment by contrast is usually a small correction and usually has a highly accurate outcome.
Epithelial - ingrowth A complication of LASIK wherein epithelial cells grow underneath the corneal flap. It should be removed if it progressives and affects vision, or creates other problems.
Excimer laser - A “cold” laser energy produced by several rare gas- halide mixtures. The term excimer comes from the concept of an energized molecule with two identical components or excited dimer (contracted to one word exci-mer). In excimer laser vision correction the term has for practical purposes become synonomous with the argon-fluoride (ArF) gas version. The wave length of an ArF excimer laser is in the far ultraviolet range at 193.
Farsightedness - The lay term for hyperopia or hypermetropia.
Focusing Error - A condition in which your eye forms a blurred image on your retina. Examples are nearsightedness, astigmatism, and higher-order aberrations (complex focusing errors).
Flap & zap - A term meaning LASIK.
FLAREX® - Fluoromethalone acetate 0.1% - Corticosteroid eyedrop used to reduce inflammation in excimer laser surgery, other ocular surgeries and ocular inflammation from other causes. It is used to decrease corneal haze and regulate healing response after PRK/LASEK. Manufactured by Alcon.
FML® - Fluoromethalone 0.1% - Corticosteroid eyedrop used to reduce inflammation in excimer laser surgery, other ocular surgeries and ocular inflammation from other causes. It is used to decrease corneal haze and regulate healing response after PRK/LASEK. Manufactured by Allergan.
FML FORTE® - Fluoromethalone 0.25% - Corticosteroid eyedrop used to reduce inflammation in excimer laser surgery, other ocular surgeries and ocular inflammation from other causes. It is used to decrease corneal haze and regulate healing response after PRK/LASEK. Manufactured by Allergan.
Glare - A condition in which patients see additional luster around lights. Patients with contacts lens can experience glare. It often occurs after refractive surgery and decreases with time.
Ghosting - Additional less distinct images surrounding the real image. A distortion of image due to irregular healing of the corneal surface.
Glaucoma - An eye disease usually associated with high eye pressure which damages the optic nerve. It is progressive and can leads to loss of vision. It is commonly treated with glaucoma eye drops. The cornea becomes thinner after excimer laser vision correction and results in eye pressure measurements reading falsely low.
Halos - A circular flares or rings of light that may appear around a headlight or other lighted object. This symptom may occur with contact lenses and after excimer laser surgery. Halos after surgery usually diminishes with time.
Herpes Simplex - A viral infection that can recur. This virus typically causes cold sores and/or vesicles to appear on the face or other parts of the body. The excimer laser can reactivate herpes simplex keratitis. You should discuss any history of this condition with your doctor before having excimer laser surgery.
Herpes Zoster - A viral infection that can recur. This condition is a reactivation of the chicken pox virus as an adult. Vesicles appear on only one side of the body. It can affect the cornea similar to herpes simplex. You should discuss any history of this condition with your doctor before having excimer laser surgery.
Hyperopia (hypermetropia) - A refractive abnormality of the eye requiring a plus (positive or convex) lens for correction. Lay term is farsightedness. Farsighted people can see at a distance more clearly than they can see objects that are closer
Immunodeficiency disease - A condition that compromises the body’s ability to heal. An example is acquired immunodeficiency syndrome (AIDS). You should discuss this condition with your doctor before having LASIK surgery.
Inflammation - A tissue's reaction to trauma often with pain, heat, redness, swelling, and or loss of function. Inflammation may be caused by mechanical trauma such as surgery, infections by bacteria or viruses, and by immune reactions, and other causes.
IntraLASIK™ - Use of an Intralase Femtosecond Laser to created a flap in LASIK surgery rather than using a microkeratome.
IOL - abbreviation for Intra-Ocular Lens.
Intra-Ocular Lens - An artificial lens to replace the cataract after cataract surgery.
Keratitis - An inflammation of the cornea. It may be caused by trauma as in an abrasion, surgery; or be caused by infections by bacteria or viruses; or be caused by immune disorders.
Keratoconjuntivitis - An inflammation (infectious or auto-immune) of the cornea and conjunctiva.
Keratometer - An instrument use to measure the curvature of the corena.
Keratoconus - An abnormality of the eye where the cornea becomes thin and deformed in the shape of a cone. This condition is usually a contraindication to excimer laser refractive surgery.
Keratomileusis - A refractive surgical technique where a partial thickness circular flap of cornea is removed, frozen, lathed to a new shape and replaced upon the cornea. The lathe can shape either a convex or concave lens.
Keratectomy - Surgical excision (removal) of any portion of the cornea.
Keratotomy - Surgical incision (cut) of the cornea as in radial keratotomy.
LASEK - An acronym for Laser assisted subepithelial keratectomy. The epithelium is moved aside followed by excimer laser ablation of the cornea and replacement of the epithelium. A bandage contact lens in place on the cornea during the healing period.
Laser - An acronym for Light Amplification by the Stimulated Emission of Radiation. It is different from ordinary light and is millions of times more powerful than light energy produced by other sources. It is composed of one color (wavelength), travels in one direction and each light wave is traveling in step with the adjacent wave increasing the laser light energy.
Laser - Thermo-Keratoplasty A holmium laser is used to shrink the collagen fibers of the cornea and results in a “steeper” cornea. It us used for lower amount of hyperopia and does not require a creation of a flap.
LASIK - An acronym for Laser in Situ Keratomileusis. A surgical operation where a flap of surface cornea is cut and rolled aside followed by excimer laser ablation of the internal tissues (stroma or body) of the cornea to correct the refractive error. The flap is replaced and heals without sutures.
Lens - A structure inside the eye that helps to focus light onto the retina. It also allows the eye to focus from distance to near. This is called accommodation. Presbyopia occurs when accommodation is lost starting around age 40. It is called a cataract when it becomes cloudy.
Limbus - The visible borderline between the clear window (cornea) and the white globe (sclera) of the eye. The conjunctival layer which covers the globe also joins at the limbus.
Low Contrast Visual Acuity - A measure of the sharpness of vision using a 10% low contrast chart with gray letters on a white background. Low contrast acuity testing is another way to determine how well patients can see in poor contrast conditions such as very dim light, rain, snow, and fog.
LTK - Abbreviation for Laser Thermo-Keratoplasty.
Masks - They are used in excimer laser surgery to modify the removal of corneal tissue by the laser. Excimer laser surgery involves the removal of or fashioning of concave (myopic) or convex (hyperopic) lenses on the corneal surface. Most refractive errors also include some element of astigmatic irregularity. Most excimer laser machines employ different kinds of masks to customize, refine and smooth the corneal surface. Many machines have an internal constricting diaphragm (like a camera f-stop mechanism) as an internal mask for use in treating Myopia. One manufacturer uses an extra material applied unto the cornea (an ablatable or destroyable mask) for treating astigmatism. Another manufacturer uses a different shaped metal mask for treatment of hyperopia or myopia. Variable rotation of the masks is used to deal with astigmatism.
Microkeratome - A surgical instrument used in LASIK to cut a thin flap of tissue from the front surface of the eye before the laser treatment is applied.
Monovision - One eye is set for distance vision and the other is set for near vision. Successful adaptation to monovision occurs in 3 to 4 weeks in about 80% of patients. The main advantage is not needing reading glasses for near tasks. The disadvantage is some decrease in depth perception. It has been our experience that patients in their 40s adapt to monovision in one to two weeks and patients in their 60s may take a few months. If a patient does not have significant astigmatism we have them try monovision with contact lenses. A few of the patients use glasses for night driving or for prolonged computer work or reading. Some monovision patients use one disposable contact lens in their near eye for good binocular vision during sports, such as tennis. Dr. Oyakawa had laser vision correction (PRK) with monovision. He uses prescription sunglasses for driving, no glasses for night driving, and glasses for prolonged computer work, reading, and close mechanical work. He is able to read the newspaper in the morning and function through out the day without glasses. During patient eye examinations and surgeries the eyepieces of the instruments are adjusted for binocularity.
Myopia - A refractive abnormality of the eye requiring a minus (negative or concave) lens for correction. The lay term is nearsightedness. People who are nearsighted can see objects up close or at near without glasses.
Nearsightedness - The lay term for myopia.
Nidek Technologies - Manufacturer of argon floride excimer laser machine - EC-5000.
N.S.A.I.D. - Abbreviation for Non Steroidal Anti-Inflammatory Drug.
OCUFEN® Flurbiprofen sodium 0.03% - Non steroidal anti-inflammatory eyes drops used after PRK/LASEK to reduce pain. Also, used to control inflammation after cataract and other ocular surgery. Manufactured by Allergan.
Off label use - The permissible use of an approved drug or instrument in a way that has not been specifically sanctioned.
Ophthalmic - Anything to do with the eye.
Ophthalmologist - A medical doctor who specializes in the eye. To become an Ophthalmologist one must first obtain a Medical Degree (M.D.) followed by an internship and a residency in ophthalmology. A medical degree typically takes 7 or 8 years of university training, an internship takes one year and an ophthalmology residency takes three years. Fellowship training is another one to two years. Specialist MDs are usually divided into "medical" and "surgical" disciplines and Ophthalmology is technically a "surgical" discipline. Some Ophthalmologists chose not to perform surgery and can be called "medical ophthalmologists".
Optician - An person who fits contact lens and glasses. They do not refract.
Optometrist - (or Doctor of Optometry) is health care provider who specializes in the examination, diagnosis, treatment, management and prevention of diseases and disorders of the visual system, the eye and associated structures as well as the diagnosis of related systemic conditions. Optometrists today most often complete a Bachelor of Science degree (with very specific requirements) followed by the four year Optometry degree. Most optometrists include provision of Contact Lens and Spectacle devices as part of their daily practice. They do not perform surgery. However, the can evaluate patients preoperative for the refractive and cataract surgeries and follow them postoperatively.
Overcorrection undercorrection, and regression - The desired correction was not achieved. This is due to many factors. Each person’s eye heals differently. The surgical plan is based on an average response to treatment. Some patients have an increased or decrease healing response. In addition the state of corneal hydration, the humidity and other unknown factors contribute to the response to surgery. These conditions can usually be enhanced (retreatment by lifting up the previously created flap and treating with the excimer laser) when stable. Enhancements are done three to six months after surgery when the eye is stable. It may the eyes longer with sever correction to become stable.
Pachymetry - Measurement of the thickness of the cornea. A minimum stromal thickness is necessary to prevent ectasia. Flap thickness and ablation depth determine the thickness of the stroma.
Phacoemulsification - The modern technique of cataract extraction through a very small incision (about 1/8”) using ultrasound to pulverize and remove the lens. An IOL is folded and inserted through very small incision. Recovery from surgery is very rapid without the postoperative restriction of older cataract techniques.
Phakic - Having an lens.
Phakic Intra-Ocular Lens - They are either placed in front of or behind the iris. They are usually used to correct severe refractive errors and maybe combined with excimer laser correction (Bioptics). There is an increased risk of complications compared to laser vision correction since this is an intraocular surgery.
Phoropter - An optical instrument containing many lenses that is used to determine the power of glasses or refractive error.
Photo Light -
Photoablation - The "cold" process of tissue removal that occurs with laser in the 200nm wavelength range. This far-UV wavelength possess light photons so powerful that the molecular bonds of the target tissue both break down and have sufficient extra kinetic energy to fly off the surface; hence ablation. Microscopic pictures show incredibly precise cuts with no evidence of tissue burning in adjacent tissue.
Photocoagulation - The process of tissue destruction accomplished by visible light radiation. Tissue is broken down by the light and "clots" as if it were cooked.
Photo Therapeutic Keratectomy - Excimer laser removal of surface tissue of the cornea such as scar tissue for medical or optical treatment reasons.
Photovaporization - The process of tissue destruction as occurs with infra red light radiation such as with a yag laser. The target tissue is ionized causing plasma formation followed by a shock wave.
Photo Refractive Keratectomy - Excimer laser correction after the removal of the epithelium. A bandage contact lens is used during the healing period.
Pinguecula - A yellowish spot seen on the white of the eye at the junction of the clear cornea and white sclera of the eye. These lesions are usually caused by UV radiation. The white surface of the eye cannot "tan" and therefore cannot protect itself from sunburn.
PRED FORTE® Prednisolone acetate 1% - Corticosteroid eyedrop used to reduce inflammation in excimer laser surgery, other ocular surgeries and ocular inflammation from other causes. It is used to decrease corneal haze and regulate healing response after PRK/LASEK. Manufactured by Allergan.
PRED MILD® Prednisolone acetate 0.12% - Corticosteroid eyedrop used to reduce inflammation in excimer laser surgery, other ocular surgeries and ocular inflammation from other causes. It is used to decrease corneal haze and regulate healing response after PRK/LASEK. Manufactured by Allergan.
Presbyopia - Is a condition in which the ability to accommodate for near vision falls off because of loss of elasticity of the crystalline lens of the eye and weakness of the ciliary muscle. The individual is no longer able to read clearly and requires reading glasses. This usually starts in the early 40s.
PRK - Abbreviation for Photo Refractive Keratectomy.
PTK - Abbreviation for Photo Therapeutic Keratectomy.
Psuedophakic - Having an IOL.
Ptygeria - The growth of a pinguecula on to the cornea.
Ocular Hypertension - Increased intraocular pressure. The intraocular pressure measures falsely low after excimer laser surgery due to the thinning of the cornea.
Radial - Pertaining to the radius or line from a circle center to the circle itself.
Radial keratotomy - A surgical operation where 90% thickness cuts are made in the cornea. These cuts are made in a radial fashion and spare the visual center of the cornea. The intention is to flatten the central cornea and was used to treat myopia.
Refraction - The bending of light wave as they pass from one medium to another also measurement of the lower order refractive error of the eye.
Regression - See overcorrection, undercorrection and regression.
Retina - The light sensitive layer that converts light images into electrical signals for transmission to the brain. Light must be focused correctly on the retina to form clear images. The retina can be compared to the film of a camera.
Retreatment - See enhancement.
RK - Abbreviation for Radial Keratotomy.
Slit lamp - A microscope for examining the eye.
Steroid Medication - A drug that reduces inflammation or the body’s reaction to injury, disease or surgery. Steroid eye drops are used after excimer laser correction. You must inform your refractive surgeon if you are taking steroids.
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.
Tonometer - An instrument that measure the intraocular pressure.
UCVA - Abbreviation for Uncorrected visual acuity.
Uncorrected visual acuity - This is the best vision measurement taken without the use of glasses or contact lenses.
Undercorrection - See overcorrection, undercorrection and regression.
Visual Acuity - A measure of the sharpness of vision using a Snellen Visual Acuity Chart.
VisX - Manufacturer of argon floride excimer laser machines VisX 2015, VisX 2020, and VisX STAR, VisxS3 and VisxS4.
VOLTAREN OPHTHALMIC - Diclofenac Sodium 0.1% non steroidal anti-inflammatory eyes drops used after PRK/LASEK to reduce pain. Also, used to control inflammation after cataract and other ocular surgery.
Wavefront - A measure of the total focusing errors (aberrations) including nearsightedness, astigmatism, and complex focusing errors (higher-order aberrations). Light is projected into your eye and focused on the retina. Part of this light is reflected back out of your eye to form the wavefront.
Wave length - The distance between the top of one wave and the top of the next wave. The argon fluoride excimer wavelength is 193 nm. This wavelength is in the far ultraviolet end of the electromagnetic spectrum.
Yag laser - A laser type using an infra red wavelength of 1064 nanometers. The laser material is neodymium Yttrium-Aluminum-Garnet. Yag lasers are used after cataract surgery to photovaporize the residual membrane behind the artificial lens.
