RCOpth General Description Of Laser Eye Surgery
Refractive surgery encompasses a range of procedures which are undertaken with the primary aim of correcting refractive error. The most common reason for performing these procedures is because the patient wishes to reduce their dependence on spectacles or contact lenses to achieve clear vision.
The National Health Service and private medical insurers do not normally fund refractive surgical procedures. Occasional exceptions to this rule include situations where cataract surgery has induced an unexpected refractive error, when a corneal refractive procedure may sometimes be preferable to an intraocular lens exchange.
Organisations which provide refractive surgical services are required to register with the Care Quality Commission and their facilities are subject to periodic inspection.
Most refractive surgical procedures achieve their objective by altering the curvature (and therefore the effective power) of the cornea. Flattening the cornea reduces its refractive power and reduces myopia (short sightedness), whilst steepening the cornea increases its refractive power and reduces hyperopia (long-sightedness). Flattening or steepening the cornea selectively along one axis reduces astigmatism.
The first refractive surgical procedure which achieved wide popularity was radial keratotomy, developed by Fyodorov in 1974. This involved the creation of a series of radial cuts in the cornea which had the effect of flattening the curvature of the central part of the cornea and reducing myopia. In the early 1980s, the excimer laser was adapted to re-shape the surface of the cornea by removing tissue in a very precise manner without damage to the internal structures of the eye. During the 1980s, laser refractive procedures gradually superseded radial keratotomy.
Early laser refractive surgery involved mechanical removal of the epithelium in the centre of the cornea followed by laser ablation of the underlying corneal stroma. This in turn has largely been replaced by LASIK (laser-assisted in-situ keratomileusis - where a hinged flap of the central corneal stroma is raised with a microkeratome and the laser ablation is applied to the underlying stromal bed before the flap is replaced) and LASEK (laser-assisted sub-epithelial keratomileusis – where a hinged flap of corneal epithelium is raised and laser ablation applied to the underlying corneal stroma before the epithelial flap is replaced).
The computer algorithms which translate a desired refractive correction into precise removal of corneal tissue by the laser have become very sophisticated and are regularly updated based on the results of surgery. Laser refractive surgery is generally effective up to 10 dioptres of myopia, 6 dioptres of hyperopia and 4 dioptres of astigmatism, though the predictability of correction tends to diminish towards the extremes of these ranges.
For correction of large myopic refractive errors and moderate or large hyperopic refractive errors, a more predictable correction may be achieved by removal of the lens (refractive lensectomy) and insertion of an intraocular lens implant of the appropriate power. This is effectively identical to a cataract operation, except for the fact that the lens being removed is healthy. There are also a number of designs of intraocular lens implant which can be inserted without the need to remove the natural lens (phakic intraocular lens implants).
Laser refractive surgery is normally conducted under local anaesthesia as a “walk-in, walk-out” procedure. Clear lensectomy and phakic intraocular lens insertion are also usually performed under local anaesthesia on a day case basis but should be performed in an operating theatre which conforms to the same standards recommended for other forms of intraocular surgery.
Disclaimer - The information contained on this page is for reference purposes only and VIP makes no guarantees as to the accuracy or credibility of the information herein. The content provided and opinions conveyed are not necessarily the opinions of VIP, it's owners or it's agents. VIP make no representation to be associated or endorsed with any person, business or organisation mentioned in our articles. The relevance and factual accuracy of the information provided and referenced, lays with the author and not VIP or it's agents and therefore we advise care when relying on this information. Links are available on every article and page to take you to the publisher and information / copyright owner, to further demonstrate that any publication is for your reference and education as topics freely available in the public domain.