Click to call

Eye Dictionary

Please click the term of your interest below to be taken to the extended explanation.

  • Aberrometry
  • Aberrometry

    The measurement of the imperfections in the optical system of the eye, measured in microns as root mean square (RMS). The use of aberrometry in developing better lens systems for telescopes is called adaptive optics and has been used by astronomers for years. It has only recently been applied to the eye.

  • Ablate
  • Ablate

    in surgery, is to remove.

  • Ablation Zone
  • Ablation Zone

    The area of tissue that is removed during laser eye surgery.

  • Acuity
  • Acuity

    Clearness, or sharpness of vision.

  • Anaesthesia
  • Anaesthesia

    is medication that attempts to eliminate pain impulses from reaching the brain. In general anaesthesia this is accomplished by putting the patient asleep. Most eye surgery is accomplished by local anaesthesia with drops or injections of anaesthetic medications either directly applied to the eye or injected around the eye.

  • Aqueous Humor
  • Aqueous Humor

    The clear fluid between the anterior chamber of the eye (which is the space between the cornea and the lens). It is continually produced by the ciliary body, the part of the eye that lies just behind the iris.

  • Astigmatic Keratectomy (AK)
  • Astigmatic Keratectomy (AK)

    is a surgical correction of corneal astigmatism often combined with LASIK correction.

  • Astigmatism
  • Astigmatism

    A distortion of the image on the retina caused by irregularities in the cornea or lens. Regular astigmatism causes light rays to come to a focus at two separate points, 90 degrees apart, rather than at one point as occurs in eyes that focus without astigmatism.

  • BCVA
  • BCVA

    Best corrected visual acuity.

  • Best corrected visual acuity (BCVA)
  • Best corrected visual acuity (BCVA)

    Best possible vision a person can achieve with corrective lenses, measured in terms of Snellen lines on an eye chart .

  • Bifocals
  • Bifocals

    Eyeglasses with two lenses for each frame. With bifocals, the most convex lenses (for close viewing) are in the lower half of the frame and the least convex lenses on the upper for distance vision.

  • Binocular vision
  • Binocular vision

    Simultaneous use of the two eyes. Normal binocular vision yields a stereoscopic image and parallax-induced depth perception.

  • Blended Vision
  • Blended Vision

    The medical term for Monovision, which is the purposeful adjustment of one eye for near vision and the other eye for distance vision.

  • Cataracts
  • Cataracts

    An opacity (clouding) in the internal natural lens of the eye. Most patients will eventually develop cataracts as they age but not all cataracts interfere with vision and so they do not all have to be removed.

  • Ciliary Body
  • Ciliary Body

    is composed of ciliary muscles and processes. The ciliary processes produces nutrients for the eye such as the Aqueous Humor. The ciliary muscles assist in accommodation or focusing of the eye for vision. When the ciliary muscle relaxes, it flattens the lens, generally improving the focus for farther objects. When it contracts, the lens becomes more convex (curved), generally improving the focus for closer objects.

  • Comprehensive eye exam
  • Comprehensive eye exam

    Evaluation of the complete visual system.

  • Conductive Keratoplasty (CK)
  • Conductive Keratoplasty (CK)

    Focal application of radio frequency energy, usually in 8 or 16 spots to shrink the corneal collagen so as to increase the central curvature of the eye to provide better reading vision in normal sighted or post LASIK patients who have good distance vision but have become presbyopic as they aged.

  • Conjunctiva
  • Conjunctiva

    A thin membrane that covers the sclera (the white part of the eye) and lines the inside of the eyelids.

  • Convergence
  • Convergence

    Turning of the eyes inwards so that they are both “aimed” towards a near object being viewed. Normally works in harmony with divergence which is used for more distant objects.

  • Cornea
  • Cornea

    The clear, front part of the eye that provides 70% of the eye’s refractive power. The cornea is the first part of the eye that bends (or refracts) the light and provides most of the focusing 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.

  • Corneal curvature
  • Corneal curvature

    Shape of the front of the eye.

  • Corneal Flap
  • 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.

  • Corneal mapping, topography
  • Corneal mapping, topography

    A tool used to see the refractive problems that might be present in the cornea. Corneal topography is used not only for screening all patients before refractive surgery like LASIK but also for fitting contacts.

  • Cylinder
  • Cylinder

    Refers to the degree of astigmatism (uneven roundness) present in the cornea.

  • Dilated, dilation
  • Dilated, dilation

    Enlargment of the pupil (space in the middle of the iris).

  • Dry Eye Syndrome
  • Dry Eye Syndrome

    A common condition that occurs when the eyes do not produce enough tears to keep the eye moist and comfortable. Common symptoms of dry eye include pain, stinging, burning, scratchiness, and intermittent blurring of vision.

  • Emmetropia
  • Emmetropia

    Perfect vision, which is occurs when a normal eye focuses rays of light exactly on the retina. An eye in a state of emmetropia requires no correction.

  • Endothelium
  • Endothelium

    The inner layer of cells on the inside surface of the cornea.

  • EpiLasik
  • EpiLasik

    A form of PRK where the epithelium is removed with a mechanical microkeratome and the underlying surface is then treated with an excimer laser.

  • Epithelium
  • Epithelium

    The outermost layer of cells of the cornea and the eye’s first defense against infection.

  • Excimer Laser
  • Excimer Laser

    An ultraviolet laser used in refractive surgery to remove corneal tissue.

  • Eye chart
  • Eye chart

    Technically called a Snellen chart, a printed visual acuity chart consisting of Snellen optotypes, which are specifically formed letters of the alphabet arranged in rows of decreasing letter size.

  • Eyelid
  • Eyelid

    Either of two movable, protective, folds of flesh that cover and uncover the front of the eyeball.

  • Farsightedness
  • Farsightedness

    The common term for hyperopia, which is the ability to see distance objects more clearly than near objects. Mild farsightedness in young patients is compatible with good vision through accommodation.

  • Femtosecond laser
  • Femtosecond laser

    Used in the LASIK procedure to make a safer and more precise flap than the older mechanical microkeratome technology, it uses a longer wavelength, smaller spot, and shorter duration per pulse than the excimer laser used to reshape the cornea .

  • Flap
  • Flap

    Part of the cornea consisting of epithelium , Bowman’s membrane and some stroma , cut with a remaining hinge and lifted up as part of the LASIK procedure.

  • Flap & Zap
  • Flap & Zap

    A slang term for LASIK.

  • Fundus
  • Fundus

    Furthest point at the back of the eye, consisting of the retina , choroid membrane , sclera , optic disc and blood vessels, seen by means of the ophthalmoscope.

  • Ghost Image
  • Ghost Image

    A fainter second image of the object you are viewing.

  • Glare
  • Glare

    Scatter from bright light that decreases vision.

  • Glaucoma
  • Glaucoma

    An increase in the normal pressure of the eye which will eventually damage the optic nerve of the eye resulting in loss of vision.

  • Halos
  • Halos

    Rings around lights due to optical imperfections in or in front of the eye.

  • Haze
  • Haze

    Corneal clouding that causes the sensation of looking through smoke or fog.

  • Hyperopia
  • Hyperopia

    The medical term for farsightedness, which is the ability to see distance objects more clearly than near objects. Mild farsightedness in young patients is compatible with good vision through accommodation.

  • Image
  • Image

    Light reflected into the eye, off objects in front of the eye. This light contains all the information about the objects (such as color, shadow. motion and detail) that are translated to the brain and allow you to “see” (know about the objects).

  • In Situ
  • In Situ

    a Latin term meaning “in place” or not removed.

  • Inflammation
  • Inflammation

    The body’s reaction to trauma, infection, or a foreign substance, often associated with pain, heat, redness, swelling, and/or loss of function.

  • Informed Consent Form
  • Informed Consent Form

    A document disclosing the risks, benefits, and alternatives to a laser eye surgery procedure.

  • Intraocular
  • Intraocular

    Inside the eye. For example, Toric Implants are intraocular lens implants (which are inserted inside the eye).

  • Intraocular Lens (IOL)
  • Intraocular Lens (IOL)

    A lens that is inserted inside the eye. For example, Phakic Implants are intraocular lens implants which are inserted inside the eye (between the cornea and the lens).

  • Intraocular lens implant (IOL)
  • Intraocular lens implant (IOL)

    Permanent, artificial lens surgically inserted inside the eye to replace the crystalline lens following cataract surgery or clear lens extraction.

  • Intraocular pressure (IOP)
  • Intraocular pressure (IOP)

    Fluid pressure within the eye created by the continual production and drainage of aqueous fluid in the anterior chamber .

  • Iris
  • Iris

    The colored ring of tissue suspended behind the cornea and immediately in front of the lens.

  • Keratectomy
  • Keratectomy

    The surgical removal of corneal tissue.

  • Keratitis
  • Keratitis

    Inflammation of the cornea.

  • Kerato
  • Kerato

    Prefix indicating relationship to the cornea.

  • Keratoconus
  • Keratoconus

    A disorder characterized by an irregular corneal surface (cone-shaped) resulting in blurred and distorted images.

  • Keratomileusis
  • Keratomileusis

    Carving of the cornea to reshape it.

  • Keratoplasty
  • Keratoplasty

    Surgical reshaping of the cornea.

  • Keratotomy
  • Keratotomy

    A surgical incision (cut) of the cornea.

  • LASEK
  • LASEK

    (Laser-Assisted Sub-Epithelial Keratectomy) a form of PRK where the epithelium is loosened, usually with alcohol, and either reflected like a LASIK flap and replaced after the excimer laser is applied to reshape the cornea. At times the epithelium is simply discarded and allowed to regenerate as it does in standard PRK surgery.

  • Laser
  • Laser

    The acronym for light amplification by stimulated emission of radiation. A laser is an instrument that produces a powerful beam of light that can vaporize tissue.

  • LASIK
  • LASIK

    The acronym for laser assisted in situ keratomileusis which refers to creating a flap in the cornea with a femtosecond laser or microkeratome and using an excimer laser to reshape the underlying cornea.

  • Lazy eye
  • Lazy eye

    Amblyopia ,an eye condition noted by reduced vision not correctable by glasses or contact lenses and is not due to any eye disease.

  • Lens
  • Lens

    A part of the eye that provides some focusing power. The lens is able to change shape allowing the eye to focus at different distances.

  • Lid speculum
  • Lid speculum

    A surgical tool that holds the eyelids open and which allows the surgeon to gain access to the eye with minimal pressure on the globe.

  • Limbus
  • Limbus

    Thin area that connects the cornea and the sclera.

  • Lower Order Aberrations
  • Lower Order Aberrations

    Refractive errors, such as nearsightedness, farsightedness, and astigmatism, that typically can be corrected with LASIK, PRK, other laser vision correction procedures, as well as glasses or contact lenses.

  • Meridian
  • Meridian

    Orientation of a particular curve, often used in relation to the cornea .

  • Microkeratome
  • Microkeratome

    A surgical device that is affixed to the eye by use of a vacuum ring. When secured, a very sharp blade cuts a layer of the cornea at a predetermined depth.

  • Monovision
  • Monovision

    The purposeful adjustment of one eye for near vision and the other eye for distance vision.

  • Myopia
  • Myopia

    The inability to see distant objects as clearly as near objects. Myopia is the medical term for nearsightedness.

  • Nearsightedness
  • Nearsightedness

    The common term for myopia, which is the inability to see distant objects as clearly as near objects.

  • Normal vision
  • Normal vision

    Occurs when light is focused directly on the retina rather than in front or behind it.

  • Ophthalmologist
  • Ophthalmologist

    A medical doctor specializing in the diagnosis and medical or surgical treatment of visual disorders and eye disease.

  • Ophthalmoscope
  • Ophthalmoscope

    Instrument used to examine the interior of the eye. It consists of a perforated mirror arranged to reflect light from a small bulb into the eye.

  • Ophthalmoscopy
  • Ophthalmoscopy

    Examination of the internal structures of the eye using an illumination and magnification system.

  • Optician
  • Optician

    An expert in the art and science of making and fitting glasses and may also dispense contact lenses.

  • Optometrist
  • Optometrist

    A primary eye care provider who diagnoses, manages, and treats disorders of the visual system and eye diseases.

  • Overcorrection
  • Overcorrection

    A complication of refractive or laser eye surgery where the achieved amount of correction is more than desired.

  • Pachymeter
  • Pachymeter

    Instrument that measures the distance between the top of the corneal epithelium and the bottom of the corneal endothelium used as diagnostic testing device measuring for corneal thickness.

  • Pachymetry
  • Pachymetry

    Exam for measuring corneal thickness.

  • Phakic Implants
  • Phakic Implants

    A type of IOL (Intra ocular Lens) that is inserted between the cornea and the lens inside the eye for the purpose of correcting near or farsightedness where LASIK is contraindicated.

  • Photophobia
  • Photophobia

    Sensitivity to light.

  • Phototherapeutic Keratectomy (PTK)
  • Phototherapeutic Keratectomy (PTK)

    is a type of eye surgery that uses a laser to treat various ocular disorders by removing tissue from the cornea. PTK allows the removal of superficial corneal opacities and surface irregularities. It is similar to photorefractive keratectomy which is used for the treatment of refractive conditions. The common indications for PTK are corneal dystrophies, scars, opacities, bullous keratopathy, recurrent corneal erosions.

  • Presbyopia
  • Presbyopia

    The inability to maintain a clear image (focus) as objects are moved closer. Presbyopia is due to reduced elasticity of the lens with increasing age.

  • PRK
  • PRK

    The acronym for photorefractive keratectomy which is 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.

  • Pupil
  • Pupil

    A hole in the center of the iris that changes size in response to changes in lighting. It gets larger in dim lighting conditions and gets smaller in brighter lighting conditions.

  • Radial Keratotomy (RK)
  • Radial Keratotomy (RK)

    A surgical procedure designed to correct myopia (nearsightedness) by flattening the cornea using radial cuts.

  • Refraction
  • Refraction

    A test to determine the refractive power of the eye; also, the bending of light as it passes from one medium into another.

  • Refractive errors
  • Refractive errors

    The degree of visual distortion or limitation caused by inadequate bending of light rays, includes hyperopia, myopia, and astigmatism.

  • Refractive Errors
  • Refractive Errors

    Imperfections in the focusing power of the eye, for example, hyperopia, myopia, and astigmatism.

  • Refractive Lensectomy (RLE)
  • Refractive Lensectomy (RLE)

    also referred to as Clear Lensectomy (CLE). The removal of the natural lens of the eye even though it does not have a cataract to replace it with an artificial lens implant of the proper power to correct nearsightedness or farsightedness in patients not suitable for LASIK or PRK.

  • Refractive Power
  • Refractive Power

    The ability of an object, such as the eye, to bend light as light passes through it.

  • Refractive surgery
  • Refractive surgery

    Type of eye surgery (such as LASIK or laser eye surgery) that affects the refraction of vision.

  • Retina
  • Retina

    A layer of fine sensory tissue that lines the inside wall of the eye. The retina acts like the film in a camera to capture images, transforms the images into electrical signals, and sends the signals to the brain.

  • RK
  • RK

    Abbreviation for “radial keratotomy “, an outdated procedure once used to correct mild to moderate myopia , whereby making a series of spoke-like incisions around its periphery flattens the cornea.

  • Routine eye exam
  • Routine eye exam

    To test the overall condition of the eye and prescribe corrective measures such as glasses, contact lenses or LASIK .

  • Sclera
  • Sclera

    The tough, white, outer layer (coat) of the eyeball that, along with the cornea, protects the eyeball.

  • Single vision
  • Single vision

    Lenses with only one focal length.

  • Slit-Lamp
  • Slit-Lamp

    Ophthalmic instrument producing a slender beam of light used to illuminate and examine the external and internal parts of the eye.

  • Sloan eye chart
  • Sloan eye chart

    A common chart used to test visual acuity with black letters of various sizes against a white background.

  • SMILE ReLEx
  • SMILE ReLEx

    SMILE often known simply as SMILE, which stands for Small Incision Lenticule Extraction, is a single-step procedure to treat short-sightedness and astigmatism. Traditional laser treatment involves cutting a flap from the cornea and uses Excimer laser to change the shape of the cornea. With ReLEx there is no flap cut required. A 4mm opening is all ReLEx SMILE needs. The minimally invasive technique allows significantly more corneal tissue to remain intact.

  • Snellen eye chart
  • Snellen eye chart

    Most common chart used to test visual acuity with black letters of various sizes against a white background.

  • Snellen lines
  • Snellen lines

    Snellen optotypes arranged in horizontal rows called “lines”.

  • Sphere
  • Sphere

    Focusing power of the corrective lens.

  • Stroma
  • Stroma

    The middle, thickest layer of tissue in the cornea.

  • Tonometry
  • Tonometry

    Procedure for the measurement of intraocular pressure. A test for glaucoma.

  • Topography
  • Topography

    A tool used to see the refractive problems that might be present in the cornea. Corneal topography is used not only for screening all patients before refractive surgery like LASIK eye surgery but also for fitting contacts.

  • Toric Implants
  • Toric Implants

    a type of Intraocular Lens (IOL) used to correct astigmatism.

  • Trifocals
  • Trifocals

    Lenses containing three focal lengths, usually arranged with the focus for distance above, intermediate distance in the middle, and near vision below.

Login