- Aberrations
- The complex shape of the cornea can mean there are many different factors that can cause distortion or blurring of the viewed image. It is possible to derive the individual contributing factors that cause these distortions. These are called aberrations. Lower order aberrations (such as Sphere or Cylinder) are corrected by glasses or contact lenses or standard laser procedures. Higher order aberrations (such as Coma or Trefoil) can only be corrected by the latest Wavefront (CustomVue) laser eye treatments.
- Aberrometry
- Measuring the extent of a persons optical aberrations using a diagnostic instrument known as an aberrometer.
- Abrasion
- The temporary loss of some of the cells of epithelium, usually by the surface being rubbed.
- Algorithm
- Calculations that have taken into account various factors. When applied to laser eye software this means the calculations should allow for the factors and correctly predict the change that is made in the patients prescription.
- Ambient
- Illumination surrounding brightness level of light.
- Astigmatism
- Where an irregular shape of the cornea prevents light rays from focusing clearly at one point on the retina, resulting in blurred vision.
- Apodization
- The gradual reduction or blending of the diffractive step heights. The application of apodization to intraocular lenses is a patented process by Alcon and can only be found in the AcrySof ReSTOR IOL.
- Cataract
- Where the natural protein structure begins to breakdown causing the lens to become cloudy or opaque.
- Coma
- A type of higher order aberration.
- Contrast Sensitivity
- A measurement of how good a person can distinguish objects against a background usually more difficult in low ambient illumination.
- Cornea
- Outer surface of the eye.
- Corneal Abrasion
- The temporary loss of some of the cells of epithelium, usually by the surface being rubbed.
- Cylinder
- A type of lower order aberration associated with astigmatism.
- Epi-LASIK
- Epithelium Laser Assisted In-Situ Keratomileusis. Combines LASIK and Advanced Surface Ablation (ASA). During this method, the microkeratome glides across the surface of the cornea. The device slides under the Epithelium layer (the cells of the eye), leaving a hinged sheet of epithelium on top of the cornea. This is then placed to the side leaving the Stromal layer exposed for ablation. Upon completion of ablation, the sheet is replaced and a soft bandage contact lens is placed over the eye.
- Epithelium Surface skin
- In this context this is the thin layer of skin on the surface of the cornea.
- Extraneous
- In this context means additional and unwanted.
- Higher order
- Aberrations such as Coma or Trefoil that can only be corrected by the latest Wavefront (CustomVue) laser eye treatments.
- Hyperope
- Someone with hyperopia.
- Hypermetropia
- Long-sightedness.
- Idiopathic
- Naturally occurring.
- Innervations
- The supply nerves to a particular part of the body.
- Lacrimal Gland
- Organ in the eye responsible for tear formation.
- Flap
- In this context the flap is the thin layer of corneal tissue that is temporarily lifted aside, whilst the laser is applied to the inner layers of the cornea.
- LASEK
- Laser Assisted Epithelial Keratomileusis. An adaptation of the PRK procedure where the epithelium is first softened by diluted alcohol before moving it aside as an epithelial flap, prior to the use of the laser. Unlike PRK, the aim is to keep this epithelium flap intact and replace it in position once the laser treatment is complete. This should mean the first 24-72 hours after treatment are more comfortable (less pain) than in the case of PRK.
- LASIK
- Laser Assisted In-Situ Keratomileusis. The most common refractive surgery procedure in the world. A flap of corneal tissue is raised and the laser is applied to remove some of the tissue of the exposed layers of cornea, before the flap is replaced in position. The removal of the tissue makes the refractive change designed to improve vision without wearing traditional forms of correction (glasses or contact lenses).
- Lower order
- Aberrations such as Sphere or Cylinder that can be corrected by glasses or contact lenses or standard laser procedures.
- Microkeratome
- An instrument used by the surgeon in the LASIK procedure to gently raise the flap of the corneal tissue.
- Myope
- Someone with myopia.
- Myopia
- Short-sightedness.
- Optical Aberrations
- The complex shape of the cornea can mean there are many different factors that can cause distortion or blurring of the viewed image.
- Photophobia
- Light sensitivity.
- Presbyopia
- Need for reading glasses. It describes the condition where the eye exhibits a progressively diminished ability to focus on near objects with age. Similar to grey hair and wrinkles, presbyopia is a symptom caused by the natural course of aging. The first symptoms (described below) are usually first noticed between the ages of 40-50.
- PRK
- Photo-refractive keratectomy. The first type of laser eye treatment. The epithelium is first removed by debridement prior to the use of the laser.
- Punctal Occlusion
- The punctum is the small hole on the lower eye-lid surface down which the tears drain away from the eye. In the case of quite severe eye dryness it is possible to block this hole with a small plug. This procedure is known as punctual occlusion.
- Pupil
- The opening in the iris through which light passes so it may reach the retina. The pupil grows in low ambient illumination and closes in bright light.
- Retina
- The film at the back of the human eye on to which the viewed image must be focused to ensure a sharp picture is communicated to the brain.
- Sphere
- A type of lower order aberration associated with myopia or hyperopia.
- Stroma
- The stroma is a middle layer in cornea. It is composed of tiny collagen fibrils that run parallel to each other. This special formation of the collagen fibrils gives the cornea its clarity.
- Surface Ablation
- Customised Surface Ablation (ASA). The title given to any Refractive Surgery technique on the surface of the eye. These may include PRK and LASEK.
- Sutured
- Stiches are applied.
- Symptomatic
- Something of which the patient is aware or affects the patient in some way.
- Trefoil
- A type of higher order aberration.
- Wavefront
- A detailed personalised description of the precise amounts and locations of an individuals optical aberrations. This information is established using an aberrometer and saved on computer to be used to direct the laser for a bespoke laser eye correction.
- Visual axis
- The part of the eye through which the person sees. This is usually through the centre with the light entering in the middle of the pupil.
