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Refer this article as: Chartrand, J., Refractive surgery: evaluation and up-date to 2010, Points de Vue, International Review of Ophthalmic Optics, N64, Spring 2011

Refractive surgery: evaluation and up-date to 2010

Online publication :
05/2011
Reading time :
8 min

The early stages of refractive surgery began in the 19th century with corneal incisions to correct post-cataract astigmatism performed by Snellen and Shiotz.

In 1972, Russian ophthalmologists used radial incisions on the cornea leaving a calibrated clear central area to modify the refractive effect - this was radial keratotomy to correct myopia. Forty years earlier, lamellar type refractive surgery had been performed by Dr Jose Ignacio Barraquer. Then came K.P.R. (Photorefractive Keratectomy) which, by means of an ablation of the corneal surface using an excimer laser, resulted in more foreseeable correction of ametropia. Now, in 2010 it is LASIK (Laser-assisted In Situ Keratomileusis) which is the procedure most commonly used worldwide to treat myopia, hypermetropia and astigmatism.

The past decade has given refractive surgery a definitive and respected position in ophthalmic surgery. Femtosecond and picosecond lasers, the in-depth study of optical aberrations of the human visual system and, above all, a correct understanding of human needs, will ensure that the satisfaction rate is maintained above 95% in patients who have undergone this operation.

Treatment of presbyopia remains the frontier to be crossed now. Remember that crystalline surgery has become a refractive treatment in itself and the laser will always be there to provide any necessary additional adjustments.

Content

By refractive surgery is meant any form of surgery that seeks to correct ametropia, either myopia, hypermetropia, astigmatism or, in some cases, presbyopia.

2010 is the European year of the LASIK. This ophthalmic surgical practice, which originated in Europe, has now been used worldwide for 20 years. It is also the operation most frequently performed on human beings, across all specialities, the second most frequent being cataract removal. Doctor Ioannis Pallikaris [6], from Crete in Greece, was the first, back in 1990, to use the corneal cap to correct ametropia using an excimer laser.

To address the beginnings of emancipation of refractive surgery, one has to go back to the seventies to the time when refractive surgery involved a scalpel, making radial incisions in the cornea, leading to central flattening of the cornea and thus correcting myopia. The ophthalmologist Snellen3, had already put forward a thesis in 1869 on the correction of astigmatism by means of corneal incisions and the Norwegian surgeon, Shiotz [3] also confirmed the refractive result in patients who had undergone cataract operations.

This work done by the pioneers of the 19th century was forgotten until the Japanese professor, Sato [3], noticed in people with kerataconus improvement of vision caused by breaking of the Descemet membrane and the ensuing sagging of the cornea. He then attempted a surgical approach, using incisions on the epithelial and endothelial side of the cornea, unaware at the time of the essential role of the endothelium in physiological maintenance of corneal transparency. Results were mixed.

In 1972, Russian ophthalmologists, the most well-known of whom was Stanislav Fyodorov [2], reported that a calibrated diameter of the clear central area of the cornea, during application of radial incisions, could alter the refractive effect. He then established nomograms to obtain the desired degree of correction. Ultrasound pachymeters had been developed in order to measure the thickness of the cornea extremely precisely and help the surgeon to measure the incisions. Either the Russian method could be used (centripetal incisions) or the American method (centrifugal incisions). The American surgeon Dr Léo Bores [2] from Detroit was one of the first to teach this technique. In Canada it was Dr Jean-Paul Demers [6], of Montreal University who addressed it (Fig. 2).

It is important to mention here that before the advent of radial keratotomy, and for 40 years, lamellar refractive surgery was used to treat strong myopia and hypermetropia. It was Professor Jose Ignacio Barraquer [6], from Bogota in Colombia, who developed this technique, which consists of making a lamellar dissection of the cornea, modifying the curve of the corneal button, which is frozen, replacing it and thus changing the refractive strength. Dr Barraquer has been nominated by the American Cataract and Refractive Society as the most influential ophthalmologist of the 20th century. As a result of his work, microkeratomes have been developed by, amongst others, Dr Ruiz from South America (Fig. 1).

The excimer laser came into being in 1975 at Kansas State University [1] in the United States, when it was discovered that xenon atoms can react with fluorine, and by excitement of a beam of electrons, emit light of a wavelength of 193 nm. Dr Stephen Trokel, of Columbia University in New-York showed that this laser beam could perform a precise ablation of bovine corneal tissue without causing any significant damage to the surrounding tissue.

I had the opportunity of joining a one week cruise around the Greek islands during which Dr Gilles Lafond was also present, following the Aegean Cornea meeting ophthalmological congress in 1996 [6] held in Samos. About twelve refractive surgeons, including Stephen Trokel, Ioannis Pallikaris, Marguerite MacDonald, Stephen Klyce and Perry Binder, the cream of refractive surgery, were also present. I was told of years of intensive research work by Dr Marguerite MacDonald at the time an ophthalmological student with Dr Trokel. A group directed by Dr Francis L’Espérance from the United States, decided to make incisions in the cornea just as for radial keratotomy (Fig. 2), using a laser, to treat myopia. The Trokel group decided to make a central ablation to achieve the same result. This was the right choice and in 1988, the first myopia treatment by excimer laser on a normal cornea was performed successfully by MacDonald, in Louisiana, on a woman in her thirties with a refractive error of less three dioptres.

The development of refractive surgery owes a great deal to the invention of the topograph that shows the curve and surface characteristics of a given cornea. It was Dr Stephen Klyce [6], of Louisiana University, who was precursor in this field and continues to work on improvement of this fundamental tool in refractive surgery. The first excimer lasers projected a wide beam and, to make the desired ablation, a diaphragm or a series of masks were used.

However, treatment areas on the cornea were limited in order to avoid removing too much stroma, thereby provoking visual difficulties in scotopic conditions.

Also, central irregularities on the cornea (central islands), as well as the induction of positive spherical aberrations, sometimes led to less satisfactory results. So, in the mid nineties, excimer lasers were improved. Sweeping systems were introduced. A small diameter beam sweeps over the surface of the cornea and can thus shape it with extreme precision. Also, these systems require less energy and less maintenance. Alongside this, guide systems were developed to ensure correct centring of the treatment (Fig. 3).

Surgical techniques have also changed. Up until the mid nineties, surface treatment, known as K.P.R (Photorefractive Keratectomy) [4], dominated worldwide The epithelium was removed from the surface of the cornea, either manually or mechanically, before applying the laser beam to modify the corneal surface. Healing of the epithelium lasted three to four days, and was sometimes extremely uncomfortable. The LASIK surgical technique (Laser-assisted in situ keratomileusis), which consists of creating a cap over the anterior cornea thanks to a keratome and performing photoablation in the stroma, has now improved the patient's comfort considerably, as well as reducing visual recuperation time. In many cases, patients are now able to drive the day after surgery. In 2010, the LASIK technique is by far the most frequently used technique worldwide in refractive surgery (Fig. 4).

In 1991, the inventor of LASIK, Pallikaris [6], believed that by leaving a hinge on the corneal cap (rather like a skin graft) healing would be easier. He used a horizontal cap. The Italian surgeon, Dr Lucio Buratto [4] was to be the initiator of the vertical hinged cap and Mr Hansa built the necessary keratome. During this period excimer lasers continued to be improved with accelerated repetitions thus reducing length of treatment. At the start of the year, 2000 visual aberrations caused by the excimer laser received a great deal of attention, leading to a study of the profile of corneal ablation with attempts at correcting aberrations of the optical system specific to each individual.

At the beginning of the 21st century [3, 4], both in America and Europe, there were those who believed that the era of super-vision had arrived. Thanks to the aberrometers, which can measure all the irregularities of the optical system in each eye, the idea of personalised treatment and elimination of optical aberrations in individuals are leading some to believe that increased acuity is possible. Based on optics used in astronomy (Zernicke polynomials), attempts are being made to correct optical aberrations of higher orders, but in view of the complexity and constant changes on the ocular surface, there is still a great deal of research needed in this field.

The past decade has truly enabled refractive surgery to gain a firm, respected place in ophthalmological surgery. Surgical inclusion criteria have been tightened and permanent discussions are on-going between surgeons, resulting in a better understanding of the morpho-biological phenomena of the cornea. For example, still today some patients need the KPR technique to treat ametropia. However the use of an antimetabolite, mitomycin, prevents variable healing of the cornea.

Better understanding of the bio-mechanical tensile forces of the cornea helps us to understand ectasia, a very rare but highly undesirable complication of LASIK.

Microkeratomes [5] are being continually improved and, in some cases, replaced by the femtosecond laser to create corneal caps, thus eliminating the complications linked to the keratome but, on the other hand, these lasers cause new types of possible complications inherent to any new instrument or laser surgery technique.

I believe that one day intrastromal [5] modification of the corneal curve will be possible, without the creation of a cap.

Several other refractive surgery procedures [3, 4] have existed over the years but, due to a lack of stable results, are no longer in use. For example, thermokeratoplasty consists of using the thermic energy of a laser to shrink the semi-peripheral collagen fibres of the cornea, leading to raising of the central section of the cornea, to correct hypermetropia. However, a regression of the refractive effect prevents a long-term result. Therefore, a modified form of LASIK, LASEK (creation of an epithelial cap) was promoted for a short while.

Treatment of keratoconus (natural or corneal post-ectasia) has been recently achieved using a surgical technique to tighten collagen fibres (cross-linking) or the implantation of intrastromal rings.

Treatment of presbyopia [3, 4] remains the frontier that we refractive surgeons would love to attain. A lot of research work and improvement in knowledge remains to be done. Nevertheless, some experimental lasers do exist and some patients have been treated, mostly patients with hypermetropia, by a friend and colleague, Dr Bruce Jackson of the University of Ottawa in Canada.

In 2010 refractive surgery complications [5] are rare, but a better understanding is still needed of ocular dryness, nocturnal vision and, above all, the human factor. I believe that the aim of refractive surgery should not be to achieve super-vision but rather natural vision that meets the specific needs of the patient and will enable us to meet any future needs.

In 2009, Dr Kerry Solomon [4, 6] of North Carolina University published a report which stated that over 90% of people who had undergone refractive surgery between 1995 and 2003 were entirely satisfied. Over 3.5 million people get rid of their ametropia every year, worldwide. I believe that the procedure will continue to be perfected and that we will achieve a procedure that is even simpler, where everything will be done by laser. Femtosecond and picosecond lasers are at the forefront of these developments.

But let us not forget that crystalline surgery has in itself become refractive treatment and, with the advent of improved intra-ocular implants, with more specific functions such as the correction of astigmatism (toric implant), and presbyopia (bifocal or progressive implant), we are witnessing an extension of possibilities for the treatment of ametropia.

In conclusion, the laser is here to stay, and will continue to be used for additional adjustments made to refractive surgery treatments.

My thanks to the ophthalmologists Doctor Patrice Archambault, M.D. of McGill University in Montreal and Doctor Gilles Lafond, M.D. of Laval University in Quebec, for their revision of my text.

References

01. Frank B. Thompson M.D. / Peter J. McDonnell, M.D.; Color Atlas / Text of EXCIMER LASER SURGERY – The Cornea. 1993
02. George O. Waring III ; REFRACTIVE KERATOTOMY for myopia and astigmatism. 1992
03. ESCRS Eurotimes journal
04. Ophthalmology times ASCRS journal
05. Numerous ESCRS and ASCRS congresses
06. Personal meetings with the refractive surgeons mentioned
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Refer this article as: Chartrand, J., Refractive surgery: evaluation and up-date to 2010, Points de Vue, International Review of Ophthalmic Optics, N64, Spring 2011

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