A-Z of Common Eye Surgery Terminology

A

ANAESTHETIC EYE DROPS
Before laser eye surgery ‘topical’ anaesthetic is used to numb the cornea. If an anaesthetic is ‘topical’ it means it can be used to numb the surface of a body part – for example, the front of the eyeball or the inside of the nose or ear. The anaesthetic works fast, usually numbing the cornea (front window of the eye) within 10 to 20 seconds. The numbing effects can last up to an hour.

ASTIGMATISM
Someone who has an astigmatism is unable to focus on close or distant objects. The condition can be accompanied by myopia (short-sightedness) or hyperopia (long-sightedness). An astigmatism is caused by the cornea being an irregular shape, where it is not equally curved with one side more curved than the other. The irregular shape usually leaves the eyeball being more ‘rugby ball’ shaped as opposed to the round ‘football’ shape most people have. The rugby ball shape means the light is distorted at it passes through the cornea and the image that is seen is blurry.

B

BILATERAL
Bilateral means both eyes. Unilateral refers to only one eye.

BLEPHARITIS
Blepharitis is inflammation of the eyelids. It is a condition that can cause the eyes to become red and swollen and itch. If you are diagnosed with Blepharitis, this needs to be treated before you can go on to have surgery. The treatment for blepharitis is straightforward and involves eye drops and compresses.

C

CATARACT
A cataract is a condition in which the lens of the eye, which is normally clear, becomes cloudy or opaque. Having a cataract is painless and develops slowly over time. It can affect both eyes or just one eye. The longer a cataract develops the more it will interfere with your vision. It can cause your eyesight to become blurry or fuzzy and colours may seem less bright. Cataracts are often related to ageing, more than 50% of people will have developed a cataract by the age of 80.
Cataract surgery is common and during this procedure, the clouded lens is removed from the eye and replaced with an artificial lens, this allows the patient to see clearly again. If the patient requires glasses for their eyesight the lenses implanted can also be used to correct their prescription too.

CONJUNCTIVITIS
Conjunctivitis is a condition where the conjunctiva has become inflamed. The conjunctiva is the clear covering of the white bit of your eye and the coating on the inside of your eyelids. Conjunctivitis can develop quickly and can cause your eyes to become red and sore. Conjunctivitis may clear on its own but often needs eye drops to treat it. Conjunctivitis can be caused by bacteria, viruses or can be allergic in nature and with the aid of eye drops usually lasts for only a short period of time.

CORNEA
The cornea is the transparent (clear) front part of the eye. The cornea covers the iris, pupil, and anterior chamber. Because there are no blood vessels in the cornea, it is clear and has a shiny surface.

CORNEAL FLAP
During the LASIK laser eye surgery procedure a corneal flap needs to be created. This means the superficial layer of the cornea needs to be lifted so the lower corneal layers are revealed. These lower corneal layers are those that will be shaped by the laser.
The thin corneal flap is hinged at a pre-determined point on the cornea. Once the laser procedure has finished and the cornea has been treated the flap is then replaced.
Whereas in the past, the corneal flap was created by a blade, nowadays, the flap is created using a femtosecond laser which has increased the safety profile of the procedure.

CORNEAL THICKNESS
When you come for an initial consultation at one of our clinics, a series of tests are carried out on your eyes, one of these will be to determine the thickness of your cornea. Corneal thickness is an important factor that will be taken into account when determining if you are suitable for laser eye surgery. As the corneas are moulded during laser eye surgery it is important that your corneas have an adequate thickness to ensure that the procedure is safe.

CROSS LINKING
Corneal collagen cross-linking is a procedure that is used to stop the progression of keratoconus or pellucid marginal degeneration cases (conditions where the cornea is inherently weak). It works by strengthening the cornea. The technique uses ultra-violet (UV) light and riboflavin (a form of vitamin B12) to strengthen the chemical bonds in the cornea.

D

DILATING EYE DROPS
During your initial consultation it is very likely we will use dilating eye drops in your eyes. Dilating eye drops are eye drops that contain medication to dilate the pupil. They work by stimulating the muscles in your eye. They either cause the muscles that enlarge the pupil to contract, or cause the muscles that make the pupil constrict to relax. Having a large (dilated) pupil is helpful to allow us to examine the interior of the eye. The effect of the dilating eye drops generally last for around 4 hours. For the duration of this time your pupils will be dilated and your vision may be slightly blurred – we ask you not to drive to your initial consultation for this reason.

DOMINANT EYE
Everyone has a dominant eye as you would have a dominant hand – the one you use to write with. You can determine which eye is your dominant eye as it is usually the eye you use to focus a camera or the eye that has the sharper vision.
If we are treating presbyopia (reading vision correction) with laser, we usually set up the dominant eye to see far (distance correction) and the non-dominant eye to see near. The brain often prefers it this way round and hence it’s important to determine which eye is dominant. In some individuals, there is cross dominance which means they can switch dominance between the eyes.

DRY EYE SYNDROME
Having consistently dry eyes is normally due to your eyes not producing enough tears or your tears evaporating too quickly. Having dry eyes may cause symptoms such as itching, burning or stinging eyes. Some people feel like there is something in their eye, causing irritation. At your initial consultation the dryness of your eyes will be measured. If your eyes are too dry to operate on we may suggest you use lubricating drops/artificial tears to moisten your eyes.

F

FLOATERS
Floaters appear as small specks or strands that seem to float across your field of vision. Floaters are actually shadows that are cast on the retina by tiny bits of gel or cells inside the clear fluid that fills the eye. Floaters usually don’t cause you any harm, however in extreme cases they may be a warning sign of serious conditions such as retinal detachment, diabetic retinopathy or infection.
If you do experience a sudden reduction in your vision and an increase of floaters you should contact us urgently.

G

GAS PERMEABLE CONTACT LENSES
Gas permeable contact lenses are a rigid type of contact lens. They allow oxygen to permeate (pass) through them. Gas permeable lenses need to be removed about one month (sometimes longer) before your initial consultation and laser eye treatment as they can distort the shape of the cornea and can affect the accuracy of the measurements we take.

GLARE
Glare is a flaring effect that occurs when looking at bright lights. It is particularly noticeable at night time when looking at car headlights. Increased haloes and glare can be a side effect of laser eye treatment although this is unusual with modern laser treatment. Glare and haloe can also occur following refractive lens exchange with multifocal lenses although these symptoms typically improve over time.

GLAUCOMA
Glaucoma is a disease in which the pressure of the fluid inside the eye is too high. This results in a loss of peripheral vision. If the condition is not diagnosed and treated appropriately the increased pressure can cause damage to the optic nerve which in turn can lead to loss of vision.

There are no symptoms to experience in the early stages of glaucoma and as such, the most common way of picking up the condition is via a regular eye examination where the eye pressures are noted to be high. Early diagnosis and treatment is important to prevent loss of vision. Daily medication in the form of eye drops are normally sufficient to treat glaucoma. Rarely, surgical intervention is required.

H

HALOES
In the early years of laser vision correction, patients used to commonly experience worsening haloes at night (additional circles around lights). This was because the treated area of cornea was smaller than the pupil size. This problem has largely been resolved by the use of wavefront laser technology and larger optical zones during treatment. We also routinely measure the pupil size prior to surgery and employ blend zones during treatment to prevent this phenomena.

HYPEROPIA
Hyperopia is where people can see distant objects clearly but are unable to focus on close objects. This is commonly known as ‘long-sightedness’. Hyperopia can be caused by either having a flat cornea or having a short eyeball. This result is that the image is focused behind the retina instead of on it, causing a blurry image.

I

IMPLANTABLE CONTACT LENSES
Implantable contact lenses are tiny contact lenses. These are implanted inside the eye instead of lying on the surface of it as most contact lenses do. Their main aim is to correct vision and are usually used to correct very high prescriptions. They can be left in the eye permanently as they are made from a biocompatible material; this means they will not be rejected by the body.
During implantable contact lens (ICL) surgery a small incision is made at the edge of the cornea. The lens is then inserted through this incision and placed behind the iris (the coloured part of the eye). The incision in the cornea heals by itself.

K

KERATOCONUS
Keratoconus is a condition that occurs in about 1 in 2000 people. It causes the cornea of the eye to become thinner over time and as it does this it gradually bulges outwards. The overall effect is blurred and distorted vision and it usually affects both eyes. Cross-linking surgery is commonly used to stabilise the progression of keratoconus.

L

LASER
Laser is an acronym that stands for: Light Amplification by Stimulated Emission of Radiation. A laser is a high energy light source; it uses light that has been emitted by the natural vibrations of atoms. In laser eye surgery, the excimer laser is used to mould the cornea to the correct prescription without causing any collateral damage. It does this by causing evaporation of tissue rather than heating it and is often described as a “cold” laser.

LASEK LASER EYE SURGERY PROCEDURE
LASEK is an abbreviation for Laser Epithelial Keratomileusis. LASEK and LASIK are both laser eye surgery procedures. LASEK is different from LASIK as at the start of the procedure the outer layer of the cornea is placed aside or removed as opposed to a corneal flap being made. To place this outer layer of cornea aside the surgeon used a diluted alcohol solution to denature it first. Once this layer has been removed a laser is then used to reshape the cornea and correct the vision – the same as the LASIK procedure. Once the reshaping is complete, the top layer is either replaced or discarded and in both cases, regenerates over 3-5 days.

LASIK LASER EYE SURGERY PROCEDURE
LASIK laser eye surgery is more commonly used than LASEK. It is a highly successful procedure used to correct vision. During the LASIK process a laser is used to cut a thin flap in the outer layer of the cornea. This flap is then lifted up and another laser is used to reshape the cornea beneath, correcting the vision of the patient. The flap is then replaced and by doing this, tricks the eye into thinking nothing has happened.

M

MONOVISION
Monovision is where you would use one eye to see distant objects and the other eye to see close objects or read. Patients with presbyopia often find monovision very advantageous as they do not need glasses for most tasks. 80% of people can get on with monovison but 20% of individuals do not like it. Before performing surgery for presbyopia, we simulate what monovision would feel like to ensure you can adapt to this arrangement.

MYOPIA
Myopia means short-sightedness. Individuals can see close objects clearly but are unable to focus on objects in the distance. Myopia can be caused either by a steep cornea or having an eyeball that is too long. As a result, images are focused in front of the retina, creating a blurry image.

MULTIFOCAL INTRA-OCULAR LENSES
Multifocal lenses are used in refractive lens exchange surgery to allow you to see objects in the distance as well as near. They are purposely designed to reduce dependence on glasses for both distance and near.

O

OPHTHALMOLOGIST
An ophthalmologist is a doctor who specialises in the eye and diseases of the eye.

P

PENTACAM
A pentacam is a scan that is used to evaluate the cornea. It takes a series of measurements from 25,000 different points on the cornea; using this information it is able to generate a detailed three dimensional map which shows the thickness of the entire cornea. The pentacam scan is then used by the eye surgeon to assess whether or not a patient is suitable for laser eye surgery treatment.

PRESBYOPIA
Presbyopia is the inability to focus on close objects. The condition gets progressively worse over time and is associated with the natural aging of the eye. It begins to affect everyone over the age of 40. Presbyopia is caused by the natural lens in the eye hardening; it becomes less elastic and the lens is not able to flex in order to focus on near objects.

The symptoms of presbyopia can be gradual but commonly include:

Being unable to read small print
Holding reading materials further away (the sensation that your arm is not long enough)
Eye strain when reading or doing concentrated work
Headaches when reading or doing concentrated work
There are several ways to treat presbyopia, these include using glasses for reading or undergoing either laser vision correction or refractive lens exchange surgery.

PUPIL
The pupil is the black circular opening in the centre of the iris (the coloured part) of the eye. The pupil regulates the amount of light that is able to enter the eye and varies in size according to the amount of light present.

R

RETINA
The retina is the area of light sensitive nerve tissue that is found at the back of the eye. It converts the images that the eye sees into electrical impulses. These electrical impulses are sent along the optic nerve to the brain which then interprets them as images.

READING GLASSES
Reading glasses are generally needed by everyone once they reach their 40s. The reason for this is that with age the muscles in the eye get stiffer, this means the eye is less able to focus on objects that are close. The need for reading glasses is often caused by the condition presbyopia. If reading glasses are not for you then there are some treatment options available including laser vision correction and refractive lens exchange.

REFRACTIVE ERRORS
When light enters the eye it is refracted (bent) as it passes through the cornea and lens. The light is bent to focus on the retina (the back of the eye) which then converts the image into a message that is sent to the brain.
Refractive errors are caused by having either an irregularly shaped eyeball or the natural aging process of the lens. This can cause problems with seeing objects far or near and can cause headaches, eye strain and squinting.

The refractive errors that are most common are:

Myopia (being short-sighted)
Hyperopia (long-sighted)
Astigmatism
Presbyopia

S

STRABISMUS (SQUINT)
A squint is a condition which causes the eyes to be mis-aligned; they are not directed at the same point at the same time. It occurs when the eye muscles are not working together properly. It is often an inherited condition but could also be caused by an injury or disease. If it is diagnosed early, a squint can usually be corrected. It can be treated with corrective glasses, eye muscle exercises, surgery or a combination of these approaches.

V

VARIFOCAL GLASSES
Varifocal glasses allow you to see three different distances in one pair of glasses – near, intermediate and far distance. They are designed for patients who need different prescription glasses, often caused by the aging of the eye. Refractive surgery has advanced over the years and now means that we are able to treat these prescriptions with surgery, enabling patients to see distant objects as well as focus on close objects without needing reading glasses.

W

WAVEFRONT TECHNOLOGY
Wavefront technology is the technology we use in laser eye surgery as standard. It is the same technology that satellite systems use to provide clear images of the earth from space. It works by correcting any imperfections in optical systems to allow for clearer images. When used in eye surgery, it is used to minimise any effects on the laser on the eyes’ optical system as well as correct any significant errors that are present. This is often the reason why many patients feel their vision is better than it ever was following laser vision correction.

Z

Z-LASIK
Z-LASIK is a specific form of laser treatment where the Ziemer Femtosecond laser is used to create the flap in the cornea. This is one of the most technologically advanced lasers on the market and one of the fastest. It can create a flap in 20 seconds with unsurpassed accuracy.

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20/20 VISION
20/20 vision is a term used to express ‘normal’ visual acuity. If you have 20/20 vision it means you see at 20 feet what should be seen at 20 feet when compared to a “normal” individual. If you had 20/100 vision, for example, if means that at 20 feet, you see what a normal person would see at 100 feet from the chart- not so good!

Having 20/16 vision which many of our patients achieve after laser vision correction means that you are better than normal; you’re seeing at 20 feet what a normal person would see at 16 feet from the chart.