Vision Terms


Eyeglass Examinations: The standard examination procedure for a patient who wants to wear eyeglasses includes at least the following:

  • Case history; reason for examination, patient medical and eye history, current medications, etc.
  • Recording of monocular (one eye) and binocular (both eyes) visual acuities at far and near, with and without present correction
  • Pupil responses (Neurological Integrity)
  • External examination findings (Biomicroscopy)
  • Internal examination findings (Ophthalmoscopy)
  • Present prescription (when applicable)
  • Retinoscopy (when applicable)
  • Subjective refraction
  • Phorometry/Binocular testing at far and near
  • Tonometry
  • Diagnosis/Prognosis
  • Specific recommendations

Contact lens examination:  Requirements for patients who wish to wear contact lenses include all of the standard eyeglass examination procedures as well as the following:

  • Keratometry
  • Diagnostic lens testing (when applicable)
  • Additional external examination (biomicroscopy) with and without contact lenses
  • Series of follow-up visits to ensure compliance with maintenance and wearing schedules.

Providers generally assess higher charges for contact lens examinations than for eyeglass examinations. Some benefit plans may require members to pay the difference between the usual and customary price for an eyeglass examination and the usual and customary price for a contact lens examination.

Dilation: The enlargement of the pupil diameter, which allows the doctor to observe the internal eye more completely. It is not always part of a provider's standard examination procedure, but providers may perform dilation if any of the following conditions exist:

  • Diabetes
  • Myopia (nearsightedness) over 6 diopters
  • Hypertension (high blood pressure)
  • Retinal disease
  • Sudden changes in vision
  • Flashes or floaters
  • Family or personal health history that predicts future ocular complications
  • State law requiring dilation

Disease detection: During the course of an examination, an optometrist or ophthalmologist may detect abnormalities in the eye that are symptomatic of certain diseases that require treatment from another health care provider, such as diabetes or hypertension. In this case, the member will be referred to the appropriate medical provider based on their health plan.

Prescription:  Prescriptions are often written following an examination to correct one of the following conditions:

  • Myopia: ("nearsightedness") A condition in which light refracted into the eye focuses at a point in front of the retina. Myopic individuals can see objects clearly at near and have trouble seeing at far. Myopia is correctable with eyeglasses or contact lenses. Myopic correcting lenses are concave, or thinner in the center than on the edge.
  • Hyperopia: ("farsightedness") A condition in which light refracted into the eye focuses at a point behind the retina. Hyperopic individuals can see objects clearly at far and have trouble seeing at near. Hyperopia is correctable with eyeglasses or contact lenses. Hyperopic correcting lenses are convex, or thicker in the center than on the edge.
  • Presbyopia: The loss of focus ability due to the natural aging process. It is correctable with bifocal or trifocal lenses that reduce the need for the eye to focus when changing from far to near vision.
  • Astigmatism:  A condition in which an asymmetric cornea results in different visual irregularities in different parts of the eye. It is correctable with eyeglass lenses that are ground to a different thickness and curvature. Toric soft contact lenses or rigid contact lenses can also correct some cases of astigmatism.

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Ophthalmologist: A medical doctor (MD) or osteopath (DO) who specializes in the treatment of the eye and visual system. In addition to providing routine eye care, ophthalmologists can diagnose and treat eye disease using medical or surgical techniques.

Optometrist: An eyecare professional who has completed four years of optometry school after graduating from college. Optometrists specialize in examination, diagnosis, and treatment of conditions of the visual system, including prescribing and fitting eyeglasses and contact lenses. Optometrists are not authorized to use surgical techniques to treat eye disease.


  • Dispensing optician: Helps patients with the selection of frames, and also measures, adjusts, and fits eyewear using prescriptions supplied by an optometrist or ophthalmologist.
  • Laboratory optician: Manufactures eyewear using prescriptions supplied by an optometrist or ophthalmologist.
  • Optometric technician: Performs the same duties as a dispensing optician, but has also had two years of formal training or has passed the National Optometric Registration Exam for technicians.

Dispensing location: Optical facilities that have the capability to dispense eyewear.  Some dispensing locations have on-site manufacturing capabilities, but the majority of dispensing locations use offsite eyewear manufacturing facilities.

DPA certification: Diagnostic pharmaceutical agent (DPA) certification is granted to optometrists who have demonstrated capability to diagnose eye disease. State licensing agencies serve as the certifying body for DPA certification.

TPA certification: Therapeutic pharmaceutical agent (TPA) certification is granted to optometrists who have demonstrated capability to diagnose and treat eye disease. In addition, TPA certified optometrists can prescribe certain medications to treat eye disease. State licensing agencies serve as the certifying body for TPA certification.

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Single vision lenses: Uncoated, plastic lenses with a single prescription that corrects myopia, hyperopia, or astigmatism.

Standard bifocal lenses: Uncoated, plastic lenses that correct both for distance and near vision in individuals with presbyopia. The top of the lens corrects for distance vision. In the lower part of the lens, there is a visible semicircle ground into the lens that corrects for near vision.

Trifocal lenses:  Uncoated, plastic lenses that correct for vision at three distances. The top of the lens corrects for distance vision. In the lower part of the lens, there is a visible semicircle ground into the lens that corrects for near vision. Just above this semicircle is an additional lens segment that corrects for distances of about an arm's length away.

Lenticular lenses:  Designed to treat eye conditions that are more serious than simply myopia, hyperopia, presbyopia, or astigmatism. They are often prescribed after cataract surgery for patients without intraocular implants.

Progressive lenses: Commonly called "no-line bifocals", progressive lenses are bifocal or trifocal lenses that have an invisible corridor of increasing power that leads from the distance portion of the lens down to the reading portion.

Polycarbonate lenses: Made of a material similar to standard plastic, but are lighter in weight and thinner than uncoated plastic lenses. They offer protection from surface abrasions like scratch resistant coated plastic lenses, and they do not shatter like glass or standard plastic lenses.

Photochromic lenses: Light sensitive glass lenses. The glass contains silver halide crystals that darken when exposed to ultraviolet (UV) light and become clear when removed from the light. In their darkened state, photochromic lenses offer protection from potentially damaging UV rays.

Transition lenses:  Light sensitive plastic lenses, which makes them lighter in weight than photochromic glass lenses. They become darker when exposed to ultraviolet light and lighten when removed from the light. Transition lenses resist UV radiation both when light and dark, and the lenses are scratch resistant.

Scratch resistant coated lenses:  Offers protection from most surface abrasions. The coating is included as a part of polycarbonate lenses, but available as an option that is applied to the surface of standard plastic lenses after the lenses are ground.

Glass lenses:  Generally heavier than plastic lenses and resist scratching better than uncoated plastic lenses.

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Daily wear contact lenses:  Can be soft or rigid contact lenses made of different types of plastic, depending on the specific type of lens. Daily wear lenses are to be worn for periods of less than 24 hours at a time, and should be removed each night before the wearer goes to sleep. Lenses generally need to be replaced annually or biannually.

Extended wear contact lenses:   Usually soft contact lenses, but are designed to be worn for 24 hours or more at a time. Some lenses are FDA approved for up to 30 days of continuous wear, but most doctors recommend removing and cleaning the lenses at least weekly. Extended wear lenses have replacement schedules that vary significantly by the specific type of lens and length of continuous wear.

Disposable contact lenses: Soft contact lenses, either daily wear or extended wear, that are replaced on a 7 to 30 day cycle. Wearers generally purchase a supply of disposable lenses that will last six months to one year.

Hard contact lenses:  These are made from a rigid plastic resin, polymethylemethacrylate (PMMA). The lenses are more durable and easier to handle than soft contact lenses, but many people may find them uncomfortable. PMMA does not absorb water, and does not allow for the transmission of oxygen through the lens to the eye. Hard contact lenses should be removed daily.

Rigid gas permeable contact lenses:  (RGP) These contact lenses are made of a non-absorbent material that is oxygen permeable. RGP lenses are durable and easy to handle like hard contact lenses, but more comfortable to wear, though usually not as comfortable as soft contact lenses. Most RGP lenses are used for daily wear, but some lenses can be worn for extended periods of time.

Medically necessary contact lenses:  Following certain surgeries, soft contact lenses are sometimes prescribed to act as a replacement for the front covering of the eye that has been removed or disturbed. These contact lens prescriptions are medically necessary, and are generally addressed differently than elective contact lenses in managed vision care policies. Medically necessary contact lenses can also be prescribed for the treatment of certain eye diseases, including keratonocus.

Toric lenses: Either hard or soft contact lenses used to treat astigmatism, which cannot be corrected with traditional spherical contact lenses.

Tinted contact lenses: Many soft and disposable contact lenses have a visibility tint, usually bluish, that makes them easier to see. This visibility tint makes the lenses easier to handle and easier to find if the wearer drops them. There is generally no additional charge for lenses with a visibility tint. Contact lenses can also be tinted to change or enhance the color of the wearer's eye. The lenses are generally made with a clear center so that the wearer's perception of color is not affected. Since these lenses are more complicated to manufacture, they are generally more expensive than clear contact lenses.

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Lasik:  Laser in-situ keratomileuis (Lasik) is a laser refractive procedure in which a portion of the outermost layer of the eye is temporarily pulled away to allow a laser beam to make direct contact with the stroma of the cornea. The laser beam is used to reshape the cornea so that it focuses light properly into the eye. The outer layer of the eye is then replaced. Recovery time after a Lasik procedure is usually very short, often a matter of hours, and patient satisfaction with the procedure is very high. The procedure is nearly painless, and it can be used to treat myopia, hyperopia, and astigmatism. Lasik was introduced in the mid 1990's, and is now the most commonly performed laser vision correction procedure.

PRK: Photorefractive keratectomy (PRK) was one of the first laser refractive surgery procedures performed to correct vision defects. In PRK, the outermost layer of the eye is removed, and then a laser beam is used to reshape the cornea. PRK can be used to correct myopia, hyperopia, and astigmatism, and results are fairly predictable. The removal of the outermost layer of the eye can result in significant discomfort, long recovery time, and the need for steroid drops to reduce inflammation in many patients. PRK was introduced in the early 1990's.

RK:  Radial keratotomy (RK) was introduced in the 1980's as a surgical technique to correct myopia. RK involves surgical scarring of the peripheral cornea to change the curvature of the cornea. Small incisions are made at even intervals around the surface of the eye. As the incisions heal, scar tissue develops and causes the cornea to reflect light at different angles. RK outcomes are often unpredictable and rely heavily on the individual surgeon performing the procedure. It also introduces the possibility for serious eye damage and compromises the integrity of the eye. Since the introduction of the laser refractive procedures, RK has rarely been performed in the United States.

AK: Astigmatic keratotomy (AK) is a variation of RK that corrects astigmatism. In AK, incisions are made in the eye at angles instead of at even intervals. AK, like RK, is rarely performed in the United States due to the significant potential for complications and the introduction of laser refractive procedures.

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