Glossary of Laser Eye Surgery Terms: C – D

laser eye surgery glossary


A condition in which the crystalline lens of the eye, which is normally clear, becomes cloudy or opaque. Cataracts are painless and form slowly and can affect one or both eyes. Over time, a cataract may interfere with vision, causing images to appear blurred or fuzzy and colours to seem faded. Most cataracts are related to ageing and affect more than 50 per cent of all adults by the age of 80. They are the primary cause of vision loss in people aged 55 and older. Those in the early stages of this condition may benefit from new glasses, better lighting and sunglasses. Cataract surgery, which is common, involves removal of the cloudy lens and replacement with an artificial lens. [Search for more]


Removal of the cloudy crystalline lens from the eye. Surgical removal of cataracts and replacement with an artificial lens (called an intraocular lens) is the most successful surgical procedure in the country. This is performed as an out-patient procedure under local anaesthesia.


The Clear Lens Exchange procedure is very similar to a cataract operation and involves replacing the human lens with an artificial intraocular lens implant (IOL). The lens is bespoke and calculated to the patient’s exact prescription to provide optimum vision. In presbyopic lens exchange, the surgeon implants a specialist multifocal lens. This type of surgery is ideal for patients aged 45 and over who require a different prescription for both their reading and distance vision.


Like any elective surgery, laser eye surgery is not 100% risk free. During and after treatment patients may feel uncomfortable, experience 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. The quality and experience of the eye surgeons at AVC mean that the clinic has a very low complication rate.


Conjunctivitis is redness and soreness (inflammation) of the conjunctiva which is the clear covering of the white of the eye and inside of the eye lids. This comes on relatively quickly and lasts for a fairly short time. Conjunctivitis may clear on its own but often needs treatment (eye drops). Conjunctivitis needs to be resolved before surgery.


Contrast sensitivity is the ability to see differences in contrast between objects or parts of objects. Reduced contrast sensitivity is a possible side effect of laser vision correction and is particularly troublesome in poor light conditions. Wavefront laser eye surgery technology reduces the change in contrast sensitivity and in some cases can actually improve it.


The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of the eye’s optical power. Because there are no blood vessels in the cornea, it is clear and has a shiny surface.


During the LASIK laser eye surgery procedure the superficial layer of the cornea needs to be lifted to reveal the lower corneal layers which are then shaped by the laser. This is done by creating a thin corneal flap which is hinged at a pre-determined point on the cornea. Once the cornea has been treated with the laser the flap is then replaced and a contact lens placed on the eye to protect it whilst it heals. The corneal flap can be created either by a miniature blade called a microkeratome or a specialised femtosecond laser.


Corneal thickness is one of the main factors that the eye surgeon will take into account when determining a patient’s suitability for laser eye treatment. During laser surgery the cornea is slightly thinned so the surgeon needs to ensure that it is thick enough to withstand the procedure. The thickness of the cornea is measured prior to surgery at the initial assessment using a device known as a pachymeter.


Corneal collagen cross-linking is used to halt the progression of keratoconus or pellucid marginal degeneration cases by strengthening the cornea. The technique uses UV light and riboflavin (a form of vitamin B12) to strengthen chemical bonds in the cornea.


The lens or crystalline lens is a transparent, bi-convex structure in the eye that, along with the cornea, helps to refract light to focus on the retina. Its function is similar to a man-made spectacle lens.


Diabetic retinopathy is the most common diabetic eye disease and a leading cause of blindness in adults. It is caused by changes in the blood vessels of the retina. The longer someone has had diabetes, the greater their likelihood of developing diabetic retinopathy. Changes in the tiny blood vessels of the retina can lead to vision loss. People with diabetes should have routine eye examinations so that diabetes-related eye problems can be diagnosed and treated as soon as possible. Maintaining strict control of blood sugar levels helps to prevent diabetic retinopathy. Surgical and laser treatments can help many people affected with this condition but this is a different type of treatment than laser eye correction.


Dilating eye drops contain medication to dilate the pupil by either stimulating the contraction of the muscles that enlarge the pupil, or relaxing the muscles that make the pupil constrict. A large pupil is helpful for examining the interior of the eye and allows for more accurate measurement of the prescription prior to laser eye surgery treatment. In general, dilation of the pupil can last from 4 to 24 hours depending on the strength of the drops used.


Usually the eye used to focus a camera or fire a gun. This eye 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 appointment.


Persistent dryness of the eyes resulting from too little production or too rapid evaporation of tears. People with dry eye syndrome may experience such symptoms as itching, burning or stinging eyes. Some people feel as though something is caught in their eye, causing an irritation. Dry eye syndrome has many causes. An optometrist may recommend the application of special eye drops called artificial tears to moisten the eyes. Laser eye surgery is not suitable for patients with severe dry eye syndrome.


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