Glossary of Laser Eye Surgery Terms: E – H

laser eye surgery glossary


At AVC eye clinic on Harley Street we use the sophisticated multi-dimensional Eyetracking Technology. This monitors the position of the eyes at all times during the laser eye surgery procedure and detects even the slightest movement to ensure the laser treatment follows the eye exactly. If too much eye movement is detected the laser is stopped immediately. Our state-of-the-art laser, the Bausch and Lomb z100, and the Eyetracking Technology enables us to deliver the highest quality and most accurate laser eye treatment available today.


A form of ultraviolet chemical laser which is commonly used in laser eye surgery and semiconductor manufacturing. This removes tissue accurately without increasing the temperature of the tissue. AVC uses the latest Bausch and Lomb z100 Technolas excimer laser.


This is an infrared laser that delivers pulses of energy to create small bubbles at precise points within the cornea. The bubbles separate the top layer of cornea to form a flap to allow refractive laser eye treatment to be performed. This is called blade-free technology as originally the flap could only be made using a miniature steel blade.


This is an orange dye that is instilled in the eye in order to assess the health of the cornea. When a cobalt blue light is shone onto the eye, any problem on the surface of the cornea appears bright green. This enables the eye care professional to easily detect any problems that can affect the cornea, for example, dryness or a scratch from a foreign body.


Specks or strands that seem to float across the field of vision. Floaters and spots are actually shadows on the retina cast by tiny bits of gel or cells inside the clear fluid that fills the eye. Floaters and spots are usually normal and harmless. However, in some cases they may warn of serious conditions such as retinal detachment, diabetic retinopathy or infection. Someone who experiences a sudden decline in vision accompanied by flashes and floaters or a sudden increase in the number of floaters should consult an optometrist or ophthalmologist urgently. Only in very severe cases would they affect laser eye surgery.


A rigid type of contact lens that allows oxygen to permeate through it. Gas permeable lenses (also known as RGP) need to be removed about one month (sometimes more) prior to the consultation and laser eye treatment as they can warp the corneal shape.


Starburst and flaring effect when looking at bright lights, particularly noticeable at night with car headlights. Halos and haze is a common side effect of laser eye treatment. Wavefront technology reduces the incidence of halo and glare, enabling patients with larger pupils to now have successful treatment.


Disease in which the pressure of the fluid inside the eye is too high, resulting in a loss of peripheral vision. If the condition is not diagnosed and treated, the increased pressure can damage the optic nerve and eventually lead to irreversible total blindness. A person who has glaucoma will not experience any symptoms in the early stages of the disease. Early detection through regular eye examinations and prompt treatment is essential to prevent vision loss. Daily medication (usually eye drops), surgery or a combination of both enables most people to control their intraocular pressure and retain their vision. Glaucoma is generally a contra-indication for laser correction but it depends on how it is controlled.


Halos used to be experienced by patients with large pupils as the treated area of the cornea was smaller than pupil size. Wavefront laser eye technology can treat a larger optical zone and can now treat pupils measuring up to 8.5mm.


Distant objects are clear but the ability to focus on close objects is impaired. This is either caused by a flat cornea or the length of the eye ball being shorter than normal which leads to the image being focused behind the retina, producing a blurry image.


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