Glossary of Laser Eye Surgery Terms: N – R

laser eye surgery glossary


Abnormal formation of new blood vessels, usually in or under the retina or on the iris surface; can develop in diabetic retinopathy, central retinal vein occlusion or macular degeneration. Corneal neovascularisation develops in patients who overwear their contact lenses.


Condition that involves involuntary, rapid, repetitive movements of one or both eyes from side to side, up and down or in a circular motion. Nystagmus may be present at birth or, less commonly, may result from disease or injury. A full assessment would be needed to establish if the nystagmus is a contra-indication to laser eye surgery.


A doctor who specialises in the eye and its diseases. AVC’s Medical Director Mr CT Pillai is fully qualified with over 20 years of ophthalmic experience. As well as being a fellow of the Royal College of Surgeons (FRCS) and Royal College of Ophthalmologists (FRCOphth), Mr Pillai is currently Chairman of the UK’s Refractive Surgeons Association (RSA).


AVC eye clinic in London has established a network of clinical partners (all of whom are experienced and accredited optometrists) in the UK and Ireland to act as a referral base for initial consultation and aftercare. Our partners are well-trained, experienced professionals in refractive surgery. They are able to carry out both initial assessments and post-operative checks. All of AVC’s partners receive continued training and support to ensure that the best possible care is received by all patients who live outside the London area and who require local initial assessments and aftercare.


The Orbscan IIz topographer analyses the physical shape and contours of the corneas and allows our laser eye surgeon to decide if it has a suitable shape and is healthy and thick enough for treatment. It is the only topographer currently available that measures the shape of both the front and back surface of the entire cornea and can therefore provide a complete picture of the dimensions of the cornea.


Corneal pachymetry is the process of measuring the thickness of the cornea. This measurement is essential prior to LASIK laser eye surgery for ensuring there is sufficient corneal thickness to prevent complications after treatment. At Advanced Vision Care, pachymetry is measured using three different devices to ensure accuracy; the ultrasound pachymeter, the pentacam and the orbscan.


The pentacam is the gold standard for evaluating the cornea. It takes measurements from 25,000 points on the cornea to generate a detailed three dimensional map which shows the thickness of the entire cornea. This is used by the laser eye surgeon to assess whether or not a patient is suitable for treatment.


AVC will not treat a woman who is pregnant or breast-feeding. They are advised to wait until three months after giving birth or breast feeding. This is because the eyes can change during this time.


Presbyopia is the loss of the ability to focus on close objects that progressively worsens over time. This condition is associated with the natural aging of the eye and it will affect everyone over the age of 40, even if the individual has or hasn’t had any previous refractive errors in their prescription in the past (including hyperopia). It is caused by the hardening of the natural crystalline lens which leads to a loss in elasticity and the inability to flex the lens to focus on near objects.


Given the condition is progressive, the symptoms can be gradual and include:

  • The inability 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 this condition; glasses for reading, bifocals/varifocal glasses (if there is another refractive error present) or Clear Lens Exchange (the removal and replacement of the natural lens with an artificial lens).


Variable-sized black circular opening in the centre of the iris that regulates the amount of light that enters the eye.


Light sensitive nerve tissue in the eye that converts images from the eye’s optical system into electrical impulses that are sent along the optic nerve to the brain. The retina forms a thin membranous lining of the rear two-thirds of the globe.


Needed by virtually everyone after they reach their forties. This is because the muscles in the eye slowly become stiffer which affects the ability to focus clearly on objects very close up. The need for reading glasses is medically known as presbyopia. There are a range of laser and non-laser eye surgery treatments available for this.


refractive errorsWhen light enters the eye it is refracted (bent) as it passes through the cornea and the lens. The light is focused on to the retina (light sensitive tissue at the back of the eye) which then converts the image into a message that is sent along the optical nerve to the brain.

Refractive errors/refraction errors are caused either by an irregularity in the shape of the eye or the aging of the natural lens. These can cause a difficulty in seeing distances or up close and blurry vision. Symptoms include haziness, headaches, eye strain and squinting.

The most common refractive errors are:


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