Welcome to Northern Eye

This is a personal ophthalmic web site run by Dr Stephen J Doyle BSc, MRCOphth

for the benefit of patients and fellow professionals. 

It is mainly concerned with refractive laser eye surgery for the correction of short sight (myopia), 

long sight (hyperopia) and astigmatism (eye shaped like a rugby ball). The two popular modalities of this are:-

PRK (Photorefractive Keratectomy) - this is where the excimer laser (an ultraviolet laser at 198nm) is applied directly onto the eye under the epithelium (top layer of the cornea)

This is a "no knife" operation. It is mostly used for myopes of -6 Dioptres or less and for hyperopes of up to +2 Dioptres. 

The  latest variation of PRK is called LASEK (Laser assisted epithelial keratomileusis) or  EPI-LASEK

(epithelium taken off with alcohol) and EPI-LASIK( epithelium taken off with a machine)

This is not quite as quick and pain free postoperatively as LASIK but without the same surgical risks and can be used from about +4 to -8 Dioptres

 i.e. the same range as LASIK

..Laser flattens the central cornea for myopia

LASIK (Laser assisted in situ keratomileusis) - so called "flap and zap". In this a thin flap from the front of the eye is made 

with a special machine called a microkeratome and the laser is applied under the flap. 

The flap can also be cut with an infrared laser (see femtosecond laser / INTRALASE). This may be slightly safer than using a mechanical microkeratome

and the quality of the flap may also be a bit better, although these claims are contentious. 

Lasik can treat up to about 8  Dioptres of short sight and 4 Dioptres of long sight.

  LASIK for myopia

If you are outside these ranges, then you may be more suitable for intraocular lens surgery. There are many good ophthalmic surgeons who do this, including my colleague Chris Heaven whose website is at www.lens-exchange.co.uk 

As a general rule, PRK or LASEK is safer then LASIK in the lower corrections. 

The eye hurts for about 6 hours after the surgery but there is little to go wrong.

 LASIK is a nicer surgical experience for the patient as there is no pain and 

there is good sight from a few hours after the operation. 

Human hair cut by excimer laser      However, as there is a surgical element as well as the laser, the potential complications are greater:

 90% of complications with LASIK are flap complications. The end results are similar with both operations. 

With higher prescriptions LASEK takes longer for good vision than lower ones.

LASIK gets there faster with no pain but at a slightly greater risk whereas LASEK/PRK  hurts a bit and takes  about 1 week before 

there is clear vision, although there is useful vision from right after the operation. 

I have done up to about 120 eyes a month and had one or two eyes with complications for both LASIK and LASEK each year, so in absolute terms the risks seem to be about the same.

PRK has a slight risk of "haze", especially in the higher prescriptions, whereas LASIK does not have this risk.

LASEK seems to have a lower risk of haze than PRK, even for high prescriptions, so reducing the one real risk of classical PRK.

"Haze" is a deposition of glycosoaminoglycans or "GAG's" and is maximal at 6 weeks post op. (see PRK complications)

Surface laser such as LASEK  may be better for the new wavefront guided lasers designed to give an even better quality of vision ("super vision"). 

This is because cutting the flap in LASIK induces random higher order aberrations, whereas surface based laser does not. 

However, this is a field still in development..

The Royal College of Ophthalmology guidelines for refractive surgery (March 2006) are available at http://www.rcophth.ac.uk/docs/publications/ExcimerLaserPatientGuideMarch2006.pdf and are worth reading.