Glossary
A - D
Glossary of terms A - D
Ablation
Removal of tissue using the laser - the tissue is evaporated by the energy of the laser. An average of 0.25 microns of tissue can be ablated per laser pulse. One micron = 0.0001cm (the average treatment is less than half the thickness of a human hair).
Aberrations
Corneal surface irregularities.
Ablation Zone
A circular area of tissue removed by the laser. It is a minute disc shaped like a lens and is effectively a ‘contact lens' lasered on to the eye surface. Doctors take into account maximum pupil dilation when programming the laser. Usually, a 6.5mm ablation zone, which can be expanded up to 9mm is given.
Acetazolamide
Oral drug prescribed to reduce intra-ocular pressure. Possible side effects include loss of appetite, drowsiness and depression. Rashes and blood disorders occur rarely.
Accommodation
The ability to change the focusing of the eye to see close up. Adjustment allows near objects to be brought into focus, this ability is lost when the lens becomes more rigid with age, around the age of 45.
Activities
Once the patient has attended the clinic for aftercare and been given the all clear from the optometrist or doctor, all normal activities can be resumed depending on the vision. (Check with the medical staff if there is anything in particular that they wish to confirm would okay to resume after treatment). Swimming should be avoided for two weeks as the chlorine in the water will sting the eye and risk of infection is increased.
Acuity
The measurement of visual sharpness. Best corrected visual acuity (VA) is the measurement of the best vision achieved with glasses or contact lenses. Uncorrected VA is the quality of vision without lenses.
Acular
Non-steroidal anti-inflammatory drop which can help reduce pain and aid healing.
Acute Complication
Complications arise quickly and need immediate attention. They are very rare and appear during the first days after treatment. These will be picked up and monitored at the first weekly check up.
Add
Used on prescriptions and refers to the power added to the lens for reading glasses, usually seen on prescriptions for people aged 50 plus.
Adverse Reaction
An unexpected and unfavourable reaction to drops or drugs. If a patient feels they are having an adverse reaction, they should contact the Clinic immediately.
Aftercare
Course of post-operative treatment involving the monitoring progress of the treated eye through regular check ups. Drugs or other treatment may need to be prescribed.
Age Related Macular Degeneration
Loss of the detection of and reaction to light resulting in decreased vision and sometimes blindness.
AK
Abbreviation for Astigmatic Keratotomy. This is the use of a diamond shaped knife to make a small incision in the outer part of the eye to reduce astigmatism.
ALK
Abbreviation for Automated Lamellar Keratoplasty, a surgical procedure to replace the front of a damaged cornea.
Amblyopia
Clinical name for a lazy eye, blind or low-functioning eye. Certain forms of mild amblyopia can be helped with laser treatment. We do not treat a good eye in case there is a problem, which could end up leaving the patient with poor vision in both eyes.
Amethocaine drops
Anaesthetic eye drops administered immediately before treatment. Numbs the eye completely, making treatment totally painless.
Anaesthetic
We use anaesthetic eye drops which numb the eye for about an hour, with no injections required.
Aniseikonia
A difference in imaging size between the two eyes.
Anisometropia
A difference in refractive power of the two eyes in which the variance is at least one dioptre.
Anomaly
Deviation from the normal.
Anterior Chamber
The fluid filled area at the front of the eye, between the cornea and the iris.
Anti-inflammatories
Drugs taken in the form of drops or ointments which reduce the inflammation and aid in pain relief.
Antibiotics
Given in the form of ointments or drops to be administered regularly for the first few days after treatment.
Aqueous Humor
The fluid in the eye, which is kept under pressure to maintain the roundness of the eye.
Artisan lens
Lens implant used for Implantable Contact Lens. These lenses are custom made according to the patient's prescription.
Aspirin
Common medication, not a contra-indication to treatment, but because it thins the blood, some doctors recommend Epi-LASEK over LASIK.
Astigmatism
Condition in which the surface of the eye is not truly round (asymmetrical) and causes the eye to focus unevenly. Vision is blurred and distorted at all distances, for example, when an astigmatic person looks at the spokes of a wheel, some spokes appear clearer than others. The optician can prescribe a lens to rectify this distortion so that when looking at the wheel, each spoke would be equally as clear.
Auto-refraction
An automatic eye test machine to assess the patient's prescription is used as a double check to assist the doctor in consultation.
Axis
The angle of the astigmatism across the cornea, measured in degrees from 0 degrees - 180 degrees. It is noted in the third box of your prescription. 90 degrees is vertical (against the rule) and 180 degrees is horizontal (with the rule) - in minus cyl form.
Balance Prescription
A prescription for one eye with a symbol BAL (or B/S-balance sphere). This means that this eye is non-functioning and the patient is not suitable for treatment. A lens of the same power is given to balance the weight and look of the glasses.
Bandage Lens
This is a contact lens that the doctor places on the eye directly after treatment, in order to protect the eye and reduce pain. Patients should not remove them. An appointment is necessary for two or three days later to be removed professionally.
Base Curve
A measurement used in prescribing a contact lens: the radius of the central posterior surface.
Benoxinate-HCL
Used as a local anaesthetic in the form of eye drops.
Best Corrected Visual Acuity
The measurement of the best vision sharpness achieved with the aid of glasses or contact lenses.
BCVA
Best Corrected Visual Acuity. See above.
Betnesol-N
Anti-inflammatory ointment used following treatment.
Betopic
Drops used to reduce the intra-ocular pressure - a possible side effect is dry eyes.
Bi-focals
Glasses or contact lenses with a different power for distance vision at the top and a prescription for reading at the bottom of the lenses (sometimes you can see the dividing line on the glasses if you look closely).
Bilateral
Treatment to both eyes in the same sitting.
Binocular
Latin bini-two + oculus-eye. Both eyes used in conjuntion give better quality of vision and depth perception.
Binocular Vision
Use of both eyes working together.
Binocular Vision Disorder
When the eyes are not working properly as a ‘team'.
Blend Zone
Patients with large pupils are given extra treatment at the outer edge of the cornea to improve on night vision problems. Where the pupil expands beyond the treatment zone. See TRANSITION ZONE
Blepheritis
Inflammation of the eyelids, a common problem but not a contra-indication. Eyes should be clear of this condition prior to treatment.
Blurry vision
Following Epi-LASEK treatment, your vision will be blurry for the first few days after treatment. This is because your epithelium (the surface cells of your eye) is healing and also partly due to the ointment/drops you are using post-treatment.
Bowman's membrane
The top layer of tissue between the epithelium and the stroma (5-10 microns thick -- .005 to .01 millimetres), which is removed with the Epi-LASEK procedure but not with LASIK.
Broad Beam Laser
A medical instrument that produces a powerful beam of light that is focused at close range to remove corneal tissue. A broad beam laser uses a relatively large beam diameter, from 6.0 to 8.0 millimetres, which can be manipulated to reprofile the cornea.
Buttonhole Flap
A flap complication, in which the flap has a central hole in it. Treatment is abandoned and the flap is replaced to heal. It is usually okay to retreat three months later but there is a small risk of scarring and decreased vision so close follow up is essential.
CK - Conductive Keroplasty
A surgical procedure for the correction of presbyopia (the need for reading glasses). CK uses a probe to apply high frequency radio waves into the corneal tissue, causing shrinkage. This controlled shrinkage reshapes the cornea to change refractive error. Optimax do not offer this procedure because the effect is only temporary and needs to be performed each year or so.
Calibration
Procedure carried out to test the laser before treatment sessions. This is to ensure that the laser is functioning properly and emitting the correct energy level.
Central Island
Central portion of the cornea is insufficiently treated leaving a raised area with surrounding deeper tissue removed around the edge of the treatment zone. This sometimes resolves itself but in some cases a re-treatment of the area is required. Wavefront guided treatment is necessary to correct this condition.
Centration
High speed trackers and iris recognition is used to ensure the laser is properly centred.
Chiron
Manufacturer of the Excimer laser ‘Technolas 217 & 217A lasers.'
Chloramphenicol
Antibiotic ointment to be administered after treatment by some doctors.
Choroid
The brownish membrane of the eyeball between the sclera (outer) and the retina (inner).
Ciliary Body
The part of the eye that connects the choroid with the iris.
Collagen Diseases
Diseases of the fibrous protein of connective tissue and bones. A contra-indication to laser treatment as healing is abnormal and unpredictable. A typical symptom is raised large scarring of wounds on the body.
Complications
During the healing process patients may experience pain on waking up, tenderness, grittiness, glare around lights at night (halos), droopy eye lids, slight double vision or loss of best visual sharpness. These effects reduce gradually and rarely persist in the long term.
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.
Congenital Nystagmus
Nystagmus is the involuntary movement of the eye, which reduces vision. This is common in Albinos. Congenital Nystagmus is thought to be present at birth. A contra-indication to laser treatment.
Conjunctiva
Delicate inner surface of the eyelid expanding to the white part of the eyeball.
Conjunctivitis
The inflammation or infection of the conjunctiva. A person who has conjunctivitis would have to wait until it has cleared before having laser treatment.
Consultant Opthalmic Surgeon/Consultant Opthalmologist
In order to become a consultant in the UK a doctor must be on the Specialist Register of the General Medical Council (GMC). Entry to the Specialist Register is with the CCST (Certificate of Completion of Specialist Training) or through equivalent qualifications under the European Union Law.
Contact lens
Miniature lens which can be placed directly onto the eye to correct refractive errors. After Epi-LASEK treatment the doctor will place a bandage contact lens on the treated eye. This is to help protect the cornea and must only be removed by the Optometrist or Doctor (NOT by the patient) in the following few days.
Contrast Sensitivity
The ability to perceive differences between an object and its background. Reduced contrast sensitivity is a possible side effect of laser vision correction and is particularly troublesome in poor illumination.
Controlled drugs
Home Office regulated and monitored prescription drugs.
Convergence
The ability to turn both eyes inward to ‘aim' at the object being viewed. Involuntary covergence is called a squint and is not correctable with a laser.
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 presyopia.
Cornea
Transparent layer covering the front of the eye. The cornea accounts for two thirds of the focusing power of the eye. Flattening of the cornea by the laser reduces its focusing power, thereby eliminating short sight.
Corneal Ectasia
The outward bulging of the cornea. This usually happens when the cornea is not thick enough to leave an adequate stromal bed (thickest layer of the cornea) following treatment. A rare but serious complication of LASIK surgery.
Corneal Endothelium
The inner layer of renewable cells on the inside surface of the cornea, which supply the cornea with nutrients and oxygen.
Corneal Epithelium
The outer surface layer of the cornea, like the epidermis or outer layer of the skin. These cells regenerate themselves every 24 hours or so and have to be displaced prior to lasering in Epi-LASEK laser treatment.
Corneal Epitheliopathy
This is staining of the surface of the eye which can result from contact lens use or disease. It will depend on the consultation with our medical staff as to whether the patient is suitable for treatment or not.
Corneal Erosion
Erosion of the cornea, due to surface dryness, trauma or other causes. Corneal erosion is very painful (similar to ARK eye) for a period of minutes to hours.
Corneal Haze
An opacification or cloudiness of the normally clear cornea, which can occur as a side effect of Epi-LASEK. Any build up of inflammatory infiltrates (white blood cells), extra moisture, scar tissue, or foreign substances such as drugs, can cause a clouding of the cornea. Most types of haze will disappear with time or drug treatment but sometimes, permanent haze or scars can form.
Corneal Thickness
Measured in microns by a Pachymeter. Essential in checking if there is enough tissue for LASIK treatment which involves cutting a flap in the cornea. Patients with a thin cornea may not be suitable for LASIK but may be suitable for Epi-LASEK or Implantable Contact Lenses.
Corneal Topographical Map
A corneal topography which shows the surface profile of the cornea. Height mapping is shown in colour of the front surface of the eye to show the surface shape of the cornea.
Corneal Ulcer
Ulcer on the front of the eye - it can be motivation to have laser treatment for short or long sight. Suitability is dependent on the doctor's decision.
Curvature
Amount of curve on the front of eye.
Custom Ablation
This refers to Wavefront guided treatment. When the laser has been programmed specifically for the patient's cornea based on their topography or on Wavefront scans.
Cylinder Meridian
In ophthalmology, a line that is the symmetrical centre of a curved optical surface. Measure of astigmatism.
Cyclopelgic Refraction
An examination of the eye to determine refractive error while the natural crystalline lens of the eye is paralysed and unable to accommodate.
Cyclopentolate
Drops used to dilate the pupil.
Debridgement
Removal of tissue or foreign object from a wound.
Decentration
In the perfect centration the centre of the Epiflap corneal ablation exactly coincides with the centre of the visual axis and/or pupil. This is like looking through the very centre 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 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 or the size of the Epiflap laser ablation zone will affect the severity or presence of symptoms. Optimax eye trackers and iris recognition avoid laser decentralisations.
Delayed Healing
When the eye heals slower than the normal rate. This can result in leaving the patient long-sighted, or suffering from haze.
Descemet's Membrane
The layer of the cornea between the stroma and the endothelium. Five microns thick (.005 millimetres), this membrane provides an adhesion layer for the endothelium.
Detached Retina
This is a serious condition affecting the back lining of the eye. If repaired successfully it may be possible to perform laser treatment on the eye. This would need to be discussed at the clinic upon consulation.
Deturgescence
The balance of hydration in the eye.
Dexamethasone
Drops used to reduce post-operative inflammation following eye operations, also in ointment form such as Maxitrol.
Diabetes
People suffering abnormal levels of blood sugars and can result in raised internal eye pressure.
Dilation
A process by which the pupil is enlarged, in order to see the back of the eye.
Dioptre
Unit of measuring the refractive power of a lens. A lens with strength of 1 dioptre will converge distant light at a point of one meter from the lens.
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.
Disposable lenses
Soft, throw away contact lenses.
Dizziness
Sense of unbalance. This is a normal symptom after treatment and should subside after a few days. If it persists then mention it to the doctor at the check up. Rest can often help to reduce the symptom.
DLK (Diffuse Lameller Keratitis)
Also known as Sands of Sahara Syndrome (SOSS). Inflammation between the corneal flap and the bed of the eye. No specific cause, but should be noted as one of the possible complications after LASIK. Not an infection. It is necessary to treat DLK without delay to avoid long term side effects and is effectively treated with steriods.
DO
Diploma in Ophthalmology.
Dominant Eye
Usually the eye used to focus a camera or fire a gun. This eye is would usually be treated second if the patient is only having one eye treated at a time. Most of the time patients now have both eyes treated at the same sitting.
Double Vision
Seeing two or more images, often shown with a prism reading on the prescription. Not suitable for laser treatment. Laser treatment can only treat the distance vision problem. If you are happy with the vision from contact lenses, then you should be suitable for laser treatment.
Droopy eye lid
A rare side effect of laser treatment. The treated eyelid droops down to varying degrees. There are surgical procedures available to correct this. Medical term for this is Ptosis (pronounced Tosis). Usually if this occurs it is only very slight (about 1mm) and in most cases it rectifies itself with time.
Dry eye
A condition where the eye fails to produce enough tears. If this is a severe condition then it is considered to be a contra-indication to treatment. Post treatment, doctors normally prescribe Hypromellose (artificial tears) which are available over the counter. This should relieve the discomfort the patient is experiencing. If discomfort continues or is severe, the patient should contact us for an appointment to check it.
D/S
Abbreviation for dioptre sphere - the measurement of short/long sight.
