- Email: [email protected]
Radial keratotomy today
Radial Keratotomy Today Arthur D. McG. Steele* years it has been shown that fewer and fewer incisions are needed to produce an effective result. Fewer incisions have necessarily been followed by a diminished level of nuisance type complications. The most important contribution of the Americans, however, to this subject was the prospective evaluation of radial keratotomy (PERK) study conducted by Waring and his associates (1983). This trial confirmed the hitherto suspected unpredictability of the procedure and helped to dampen the uncontrolled enthusiasm of the public for this "wonder treatment".
Radial Keratotomy in the United Kingdom i~i!!
i ~il¸:~)&~/~
History of the Procedure The principles of radial keratotomy have been understood for a long time and were all quite well described by Lans in 1898. He demonstrated the fact that radial incisions in the cornea could flatten the centre of the cornea. He showed also that deep incisions were more effective as well as the fact that the flattening produced was modified by the healing process. Sato working in Japan experimented with radial keratotomy for myopia (Sato 1953), keratoconus (Sato 1950) and astigmatism using incisions of the cornea both anterior and posterior. At this time the significance of the irreplaceable nature of the endothelial cells on the posterior surface of the cornea was not understood and it is now well known that many of Sato's patients suffered late endothelial decompensation (Akiyama 1984). This complication led to the procedure being abandoned in Japan but it was taken up again by Yenalief (1979) and later by Fyodorov (1980) both working in the Soviet Union. These workers used only anterior corneal incisions and demonstrated the effectiveness of the procedure for the correction of myopia. The publication of their results in the late 1970s stimulated a widespread interest throughout the world. Much of this interest was taken up by the lay press and the resultant public awareness of the procedure and demands for it led to a varied professional response. In the United States of America this was enthusiastic, while in most parts of Western Europe the procedure was taken up on a distinctly sporadic basis. Over the last ten years the procedure has been much modified, predominantly by the American ophthalmologists who brought their interest in technology to bear upon the subject. They introduced new instruments such as ultrasonic pachymeters and micrometer diamond knives which greatly improved the quality of the surgery and the predictability of the technique. In more recent *Moorfields Eye Hospital, London
Transactions B C L A International Conference 1988
As the author had had a longstanding interest in refractive surgery for the management of myopia, aphakia and the management of astigmatism following penetrating keratoplasty, it seemed natural to take aft interest in this new operation and accordingly a small trial was started for carefully selected patients who presented themselves as candidates for refractive surgery for uncomplicated myopia at Moorfields Eye Hospital in 1980. This trial persisted for approximately three years before being brought to a halt. The trial indicated that the procedure was effective with a very low complication rate and since that time a small number of patients have continued to be operated in most weeks under the author's care. At Moorfields Eye Hospital, however, the procedure continues to this day to be regarded as an "experimental" operation. Patients are encouraged to understand that this is not an operation which should be applied to the myopic population in general, largely because of the unknown nature of the long term effects of the procedure. The fact that Sato's patients suffered endothelial decompensation twenty years after their original surgery cannot be forgotten and even now it is still too soon to be absolutely confident that none of our patients will suffer the same disaster. In all fairness endothelial cell studies of our early patients failed to show any pro~essive endothelial cell damage, but even so we continue to take a cautious attitude. Patients also need to know that although their refractive error may fall within a range which can normally be eliminated by radial keratotomy, or at least markedly modified, the procedure is unpredictable for the individual. At Moorfields we also inform patients that the procedure is still controversial, particularly with the ophthalmic medical profession, many of whom regard the procedure as unethical, because it is unnecessary surgery upon the normal eye. The fact that most myopes with four or five dioptres of myopia do not regard themselves as having normal eyes has not encouraged most members of the profession to change their opinion or modify their attitudes. The more important controversial factor about radial keratotomy is the fact that the procedure may well weaken the mechanical strength of the anterior segment
79
of the globe. In the event of the eye receiving further blunt trauma there are good reasons for believing that the globe may well rupture in the lines of the incisions. Fortunately, such trauma is uncommon, but patients are all warned that rough sports like rugby, football and boxing are not advisable for patients who have had radial keratotomy. Patients also need to know that some patients who have undergone radial keratotomy have lost their vision as a result. In most cases this has been by virtue of o~)erwhelming ocular infection which starts as an abscess in the cornea in one of the incisions. The incisions of radial keratotomy are slow to heal completely and the healing processes probably take two to three years. During this time the patient continues to be at risk, possibly in the same way as patients wearing continuous we~ii- contact lenses are at risk of corneal sepsis.
Management and Technique
Initial.Assessment Prospective candidates for radial keratotomy are initially seen in an outpatient clinic. This assessment involves an interview during which one tries to determine the reasons for the patient's interest in the procedure and an attempt is made by the medical staff to ensure that the patient has as complete an understanding of the risks he or she may be taking as is practicable. In many cases this interview is sufficient and patients wiU depart the wiser for being better informed. Those who continue to be interested in the procedure are examined to assess the degree of their myopia and to ensure that there are no other ocular defects.
Inpatient Management At Moorfietds patients are admitted for refractive surgery and for radial keratotomy they are admitted the day before surgery during which time they have a further intensive medical examination, refraction and pachymetry measurements. Pachymetry is both optical and ultrasonic. It is our experience that optical pachymetry is more accurate and more reliable than the ultrasonic measurements. Thickness measurements are taken centrally and in the mid-periphery at four or eight cardinal points.
Surgery Radial keratotomy is performed in the operating theatre using the operating microscope. The author prefers patients to be anaesthetised by general anaesthetic. The surgical procedure comprises identification of the visual axis, determination of the central corneal area to be spared from the corneal incisions, the making of the radial incisions, irrigation of the incisions and the application of antibiotic drops. The visual axis for surgical purposes is determined by the position of the pupil which is constricted by the instillation of Pilocarpine eyedrops at the time of the anaesthetic pre-medication. The size of the central spared area varies inversely with the degree of myopia one is aiming to correct. The less the myopia, the larger the central spared area and vice versa. The size of this area varies from five to three millimetres though in rare cases of high myopia the author has been known to
80
reduce the central spared area to as little as 2.5ram. The radial incisions are made from the edge of the central spared area which is marked by a circular indentation to just short of the corneal limbus, thus leaving a clear uncut zone around the peripheral cornea. Incisions may either be made from the centre to the periphery or from the periphery to the centre. It is necessary to ensure that the incisions are as deep as possible if they are to be effective and in particular the incisions need to be as deep as possible at the central end of the incision adjacent to the central spared area. In the author's practice most incisions are made at a depth of 115% of the measured central corneal thickness and the incisions are made with a diamond knife mounted in a micrometer knife handle so that the blade projects below the shoulders of the knife by a fixed and known depth. At the conclusion of the incision making, the incisions are irigated with saline to ensure that no epithelium has been left in the depth of the incisions which might otherwise lead to the development of epithelial ceil rests.
Post-operative Care Patients are discharged from hospital the morning after surgery and they are treated with antibiotic and steroid eyedrops for a period of approximately two weeks. They are assessed in the Corneal Clinic at intervals of two and six weeks followed by three, six, twelve and twentyfour month assessments. Simultaneous surgery for both eyes is never undertaken and the procedure between the two eyes is separated by approximately three months. This is because it takes approximately three months to know the final refractive results of the procedure.
Complications The only pre-operative complication experienced by the author is spot perforation during the procedure. This is always immediately detected by the appearance of aqueous on the surface of the cornea. Withdrawal of the knife is always associated with cessation of leakage of aqueous and the procedure can be continued without sig~nificant difficulty other than the inconvenience of a mild softening of the globe. The depth of the knife is usually reduced by .02 of a millimetre before proceeding with the operation. The final stages of the procedure under these circumstances is to complete the incision where the perforation occurred. This is in most cases at the central part of the incision in the lower temporal quadrant. In only one case over the last eight years has a spot perforation led to shallowing of the anterior chamber and this in that one case was controlled by the insertion of a single suture, left in place for three days. Patients who have suffered spot perforations and who have had endothelial specular photographic studies do not show any greater propensity for progressive endothelial cell damage than other patients. Other post-operative complications tend to be of a nuisance factor. The worst of these is over correction to a significant degree of hypermetropia. Fortunately, this is not now common but it was more common in the early learning period. Most patients suffer a period of diurnal variation of vision due to the fact that the cornea appears to be flattened during sleep and progressively steepens
Tramactions BCLA lmcrna~ional Coni:erence 1988
during the waking day. This diurnal variation, however, is very variable in the degree to which it annoys patients and has usually completely disappeared after six months. A few patients are troubled by glare and starburst effects at night or in the dark. With the dilated pupil light, especially from point sources like street lamps and car headlights, can be troublesome, but it is uncommon for a patient to be disabled by this symptom. While late infections are well documented in the United States of America (Yelender 1982), some of which have led to total loss of vision, I am fortunate to be able to report that we have not experienced this disaster, but I recognise that we are at constant risk. By the same token we have had no patient suffer a rupture of the globe by virtue of previous radial keratotomy.
Results I thought it would be helpful to show the sort of results being obtained by radial k'eratotomy after the end of the learning procedure and after the introduction of the more sophisticated instruments which were not available in 1980. The results of seventy-one procedures undertaken in the first half of 1986 have now been analysed and all of which have a two year follow-up. The seventyone procedures are on forty-four patients, twenty-six of whom were male and eighteen female. The age range was from twenty to forty-eight years with an average of thirtytwo years. For the purposes of analysis pre-operative refractive errors have been divided into three bands. The first band comprises those with a pre-operative refraction of four dioptres or less. This band is considered to have the best prognosis for a good uncorrected visual acuity postoperatively. The second band with a pre-operative refractive error of between four and six dioptres has a moderate chance of achieving good uncorrected vision, while the third band with a pre-operative refractive error of greater than six dioptres of myopia are regarded as having a poor chance of good uncorrected vision. The distribution of the seventy-one eyes in these three bands Table I: Initial Refractive Error 1 - 4 dioptres -- Good chance of
53 eyes
SUCCESS
4 - 6 dioptres
-- Fair chance of
14 eyes
Success
6 dioptres
-- Poor chance of
4 eyes
success
Table II: Post-operative Acuities 53 eyes 4 dioptres f>6/6 38 >6/12 49 <6/12 4 14 eyes 4 - 6 dioptres > 6 / 6 8 t>6/12 11 <6/12 3 4 eyes 6 dioptres >6/12 3 <6/12 1 TOTAL 6/12 or better-- 89%
Transactions BCLA International Conference 1988
(71%) (92%) (8%) (57%)
(78.5%) (21.5%) 75% 25%
is shown on Table I. The distribution of the post-operafive uncorrected visual actuity is shown in Table II. It will be seen that of this total number of patients 89 % achieved an uncorrected visual acuity of 6/12 or better. Closer inspection of these results shows that of the fiftythree eyes with a good prognosis 92% achieved a levelof acuity of 6/12 or better and of these 71% achieved an acuity of 6 / 6 or better. For the group with a moderate chance of good uncorrected vision, this being a group of fourteen eyes, 78.5% enjoyed an uncorrected vision of 6/12 or better and of these 57% had achieved an acuity of 6 / 6 or better without correction. There was only a small number of eyes (four) who fell into the group with little chance of good uncorrected vision and it is astonishing to find that here 75 % achieved an uncorrected acuity of 6/12 or better though none achieved 6/6. Of the total seventy-one procedures 89% achieved an uncorrected vision of 6 / 1 2 or better.
Table III: Motivation Sporting Police, Fire or Armed Services C / L intolerance "Social" Work related problems High myopia TOTAL
10 10 11 8 4 1 44
Table III lists the motivating factors which prompted the patients to seek refractive surgery and in this group of forty-four patients it will be seen that over half of them sought relief for sporting or work related requirements. No patients suffered severe complications as a result of their procedures and the incidence of nuisance factors like diurnal variation, starburst and nocturnal glare was very low.
Discussion Radial keratotomy is clearly an effective procedure for the elimination or reduction of low myopia with a low complication rate. The major factor in the United Kingdom which prevents the procedure from being more widely applied is professional reluctance to recognise myopia as a justifiable reason for a surgical procedure. Ophthalmic surgeons in the United Kingdom are already overloaded with work related to patients with visual disability particularly with the management of cataract. It is therefore not surprising that low myopia and its management is regarded as having a low priority. The results achieved in the United Kingdom are every bit as good as those achieved and reported on in the United States of America and in other centres of known excellence. The future of refractive surgery of all sorts is dominated by the possible arrival of an effective form of excimer laser capable of creating on the surface of the cornea any desired refractive curvature by a process of photoablafion involving only the most superficial layers of the corneal stroma. Such a procedure, if it is found to
81
be effective and enduring is likely to be associated with a remarkably low complication rate and the floodgates of members of the public demanding relief from spectacle correctioh of all sorts may well be opened. How the ophthalmic surgical world will manage the possible demand is a problem which may yet have to be solved.
References Akiyama K, Tanaka M, Kanai A, Naka~ma A (1984) Problems arising from Sato's radial keratotomy procedure in Japan. CLAO Journal; 10: 179-184. Fyodorov S (1980) Surreal correction of myopia and astigmatism. In Schachar RA, Levy NS, Schachar L eds. Keratorefraction: Proceed-
~2
ings of the Keratorefractive Society Meeting, Denison. LAL Publishing; 141-172. Gelender H, Flyn HW, Mendelbaum SH (1982) Bacterial endophthalmitis following radial keratotomy. Am J Ophthalmol; 93:323. Lans LJ (1898) ExperimenteUe Untersuchungen uber Enstehung yon asfigmatissus durch nicht-perforirende corneawunden. Albrecht Von Graefes. Arch Ophthalmot.; 45: 117-152. Sato T (1950) Posterior incision of cornea: Surgical treatment for conical cornea and astigmatism. Am. J. Ophthatmol. 33: 943-948. Sato T, Akiyama K, Shibata H (1953) A new surgical approach to myopia. Am. I. Ophthalmol. 36: 823-829. Waring GO, Moffltt SD, Gelender H, Borque LB and the PERK Study Group. (1983) Rationale for and design of the National Eye Institute Prospective Evaluation of Radial Keratotomy (PERK) Study. Ophthalmology; 90: 40-58. Yenalief FS (I979) Experience in surgical treatment of myopia. Vestn OftalmoL; 3: 52-55.
Tr"~asactions BCI-A International Coherence 1988
Radial Keratotomy in the United Kingdom i~i!!
i ~il¸:~)&~/~
History of the Procedure The principles of radial keratotomy have been understood for a long time and were all quite well described by Lans in 1898. He demonstrated the fact that radial incisions in the cornea could flatten the centre of the cornea. He showed also that deep incisions were more effective as well as the fact that the flattening produced was modified by the healing process. Sato working in Japan experimented with radial keratotomy for myopia (Sato 1953), keratoconus (Sato 1950) and astigmatism using incisions of the cornea both anterior and posterior. At this time the significance of the irreplaceable nature of the endothelial cells on the posterior surface of the cornea was not understood and it is now well known that many of Sato's patients suffered late endothelial decompensation (Akiyama 1984). This complication led to the procedure being abandoned in Japan but it was taken up again by Yenalief (1979) and later by Fyodorov (1980) both working in the Soviet Union. These workers used only anterior corneal incisions and demonstrated the effectiveness of the procedure for the correction of myopia. The publication of their results in the late 1970s stimulated a widespread interest throughout the world. Much of this interest was taken up by the lay press and the resultant public awareness of the procedure and demands for it led to a varied professional response. In the United States of America this was enthusiastic, while in most parts of Western Europe the procedure was taken up on a distinctly sporadic basis. Over the last ten years the procedure has been much modified, predominantly by the American ophthalmologists who brought their interest in technology to bear upon the subject. They introduced new instruments such as ultrasonic pachymeters and micrometer diamond knives which greatly improved the quality of the surgery and the predictability of the technique. In more recent *Moorfields Eye Hospital, London
Transactions B C L A International Conference 1988
As the author had had a longstanding interest in refractive surgery for the management of myopia, aphakia and the management of astigmatism following penetrating keratoplasty, it seemed natural to take aft interest in this new operation and accordingly a small trial was started for carefully selected patients who presented themselves as candidates for refractive surgery for uncomplicated myopia at Moorfields Eye Hospital in 1980. This trial persisted for approximately three years before being brought to a halt. The trial indicated that the procedure was effective with a very low complication rate and since that time a small number of patients have continued to be operated in most weeks under the author's care. At Moorfields Eye Hospital, however, the procedure continues to this day to be regarded as an "experimental" operation. Patients are encouraged to understand that this is not an operation which should be applied to the myopic population in general, largely because of the unknown nature of the long term effects of the procedure. The fact that Sato's patients suffered endothelial decompensation twenty years after their original surgery cannot be forgotten and even now it is still too soon to be absolutely confident that none of our patients will suffer the same disaster. In all fairness endothelial cell studies of our early patients failed to show any pro~essive endothelial cell damage, but even so we continue to take a cautious attitude. Patients also need to know that although their refractive error may fall within a range which can normally be eliminated by radial keratotomy, or at least markedly modified, the procedure is unpredictable for the individual. At Moorfields we also inform patients that the procedure is still controversial, particularly with the ophthalmic medical profession, many of whom regard the procedure as unethical, because it is unnecessary surgery upon the normal eye. The fact that most myopes with four or five dioptres of myopia do not regard themselves as having normal eyes has not encouraged most members of the profession to change their opinion or modify their attitudes. The more important controversial factor about radial keratotomy is the fact that the procedure may well weaken the mechanical strength of the anterior segment
79
of the globe. In the event of the eye receiving further blunt trauma there are good reasons for believing that the globe may well rupture in the lines of the incisions. Fortunately, such trauma is uncommon, but patients are all warned that rough sports like rugby, football and boxing are not advisable for patients who have had radial keratotomy. Patients also need to know that some patients who have undergone radial keratotomy have lost their vision as a result. In most cases this has been by virtue of o~)erwhelming ocular infection which starts as an abscess in the cornea in one of the incisions. The incisions of radial keratotomy are slow to heal completely and the healing processes probably take two to three years. During this time the patient continues to be at risk, possibly in the same way as patients wearing continuous we~ii- contact lenses are at risk of corneal sepsis.
Management and Technique
Initial.Assessment Prospective candidates for radial keratotomy are initially seen in an outpatient clinic. This assessment involves an interview during which one tries to determine the reasons for the patient's interest in the procedure and an attempt is made by the medical staff to ensure that the patient has as complete an understanding of the risks he or she may be taking as is practicable. In many cases this interview is sufficient and patients wiU depart the wiser for being better informed. Those who continue to be interested in the procedure are examined to assess the degree of their myopia and to ensure that there are no other ocular defects.
Inpatient Management At Moorfietds patients are admitted for refractive surgery and for radial keratotomy they are admitted the day before surgery during which time they have a further intensive medical examination, refraction and pachymetry measurements. Pachymetry is both optical and ultrasonic. It is our experience that optical pachymetry is more accurate and more reliable than the ultrasonic measurements. Thickness measurements are taken centrally and in the mid-periphery at four or eight cardinal points.
Surgery Radial keratotomy is performed in the operating theatre using the operating microscope. The author prefers patients to be anaesthetised by general anaesthetic. The surgical procedure comprises identification of the visual axis, determination of the central corneal area to be spared from the corneal incisions, the making of the radial incisions, irrigation of the incisions and the application of antibiotic drops. The visual axis for surgical purposes is determined by the position of the pupil which is constricted by the instillation of Pilocarpine eyedrops at the time of the anaesthetic pre-medication. The size of the central spared area varies inversely with the degree of myopia one is aiming to correct. The less the myopia, the larger the central spared area and vice versa. The size of this area varies from five to three millimetres though in rare cases of high myopia the author has been known to
80
reduce the central spared area to as little as 2.5ram. The radial incisions are made from the edge of the central spared area which is marked by a circular indentation to just short of the corneal limbus, thus leaving a clear uncut zone around the peripheral cornea. Incisions may either be made from the centre to the periphery or from the periphery to the centre. It is necessary to ensure that the incisions are as deep as possible if they are to be effective and in particular the incisions need to be as deep as possible at the central end of the incision adjacent to the central spared area. In the author's practice most incisions are made at a depth of 115% of the measured central corneal thickness and the incisions are made with a diamond knife mounted in a micrometer knife handle so that the blade projects below the shoulders of the knife by a fixed and known depth. At the conclusion of the incision making, the incisions are irigated with saline to ensure that no epithelium has been left in the depth of the incisions which might otherwise lead to the development of epithelial ceil rests.
Post-operative Care Patients are discharged from hospital the morning after surgery and they are treated with antibiotic and steroid eyedrops for a period of approximately two weeks. They are assessed in the Corneal Clinic at intervals of two and six weeks followed by three, six, twelve and twentyfour month assessments. Simultaneous surgery for both eyes is never undertaken and the procedure between the two eyes is separated by approximately three months. This is because it takes approximately three months to know the final refractive results of the procedure.
Complications The only pre-operative complication experienced by the author is spot perforation during the procedure. This is always immediately detected by the appearance of aqueous on the surface of the cornea. Withdrawal of the knife is always associated with cessation of leakage of aqueous and the procedure can be continued without sig~nificant difficulty other than the inconvenience of a mild softening of the globe. The depth of the knife is usually reduced by .02 of a millimetre before proceeding with the operation. The final stages of the procedure under these circumstances is to complete the incision where the perforation occurred. This is in most cases at the central part of the incision in the lower temporal quadrant. In only one case over the last eight years has a spot perforation led to shallowing of the anterior chamber and this in that one case was controlled by the insertion of a single suture, left in place for three days. Patients who have suffered spot perforations and who have had endothelial specular photographic studies do not show any greater propensity for progressive endothelial cell damage than other patients. Other post-operative complications tend to be of a nuisance factor. The worst of these is over correction to a significant degree of hypermetropia. Fortunately, this is not now common but it was more common in the early learning period. Most patients suffer a period of diurnal variation of vision due to the fact that the cornea appears to be flattened during sleep and progressively steepens
Tramactions BCLA lmcrna~ional Coni:erence 1988
during the waking day. This diurnal variation, however, is very variable in the degree to which it annoys patients and has usually completely disappeared after six months. A few patients are troubled by glare and starburst effects at night or in the dark. With the dilated pupil light, especially from point sources like street lamps and car headlights, can be troublesome, but it is uncommon for a patient to be disabled by this symptom. While late infections are well documented in the United States of America (Yelender 1982), some of which have led to total loss of vision, I am fortunate to be able to report that we have not experienced this disaster, but I recognise that we are at constant risk. By the same token we have had no patient suffer a rupture of the globe by virtue of previous radial keratotomy.
Results I thought it would be helpful to show the sort of results being obtained by radial k'eratotomy after the end of the learning procedure and after the introduction of the more sophisticated instruments which were not available in 1980. The results of seventy-one procedures undertaken in the first half of 1986 have now been analysed and all of which have a two year follow-up. The seventyone procedures are on forty-four patients, twenty-six of whom were male and eighteen female. The age range was from twenty to forty-eight years with an average of thirtytwo years. For the purposes of analysis pre-operative refractive errors have been divided into three bands. The first band comprises those with a pre-operative refraction of four dioptres or less. This band is considered to have the best prognosis for a good uncorrected visual acuity postoperatively. The second band with a pre-operative refractive error of between four and six dioptres has a moderate chance of achieving good uncorrected vision, while the third band with a pre-operative refractive error of greater than six dioptres of myopia are regarded as having a poor chance of good uncorrected vision. The distribution of the seventy-one eyes in these three bands Table I: Initial Refractive Error 1 - 4 dioptres -- Good chance of
53 eyes
SUCCESS
4 - 6 dioptres
-- Fair chance of
14 eyes
Success
6 dioptres
-- Poor chance of
4 eyes
success
Table II: Post-operative Acuities 53 eyes 4 dioptres f>6/6 38 >6/12 49 <6/12 4 14 eyes 4 - 6 dioptres > 6 / 6 8 t>6/12 11 <6/12 3 4 eyes 6 dioptres >6/12 3 <6/12 1 TOTAL 6/12 or better-- 89%
Transactions BCLA International Conference 1988
(71%) (92%) (8%) (57%)
(78.5%) (21.5%) 75% 25%
is shown on Table I. The distribution of the post-operafive uncorrected visual actuity is shown in Table II. It will be seen that of this total number of patients 89 % achieved an uncorrected visual acuity of 6/12 or better. Closer inspection of these results shows that of the fiftythree eyes with a good prognosis 92% achieved a levelof acuity of 6/12 or better and of these 71% achieved an acuity of 6 / 6 or better. For the group with a moderate chance of good uncorrected vision, this being a group of fourteen eyes, 78.5% enjoyed an uncorrected vision of 6/12 or better and of these 57% had achieved an acuity of 6 / 6 or better without correction. There was only a small number of eyes (four) who fell into the group with little chance of good uncorrected vision and it is astonishing to find that here 75 % achieved an uncorrected acuity of 6/12 or better though none achieved 6/6. Of the total seventy-one procedures 89% achieved an uncorrected vision of 6 / 1 2 or better.
Table III: Motivation Sporting Police, Fire or Armed Services C / L intolerance "Social" Work related problems High myopia TOTAL
10 10 11 8 4 1 44
Table III lists the motivating factors which prompted the patients to seek refractive surgery and in this group of forty-four patients it will be seen that over half of them sought relief for sporting or work related requirements. No patients suffered severe complications as a result of their procedures and the incidence of nuisance factors like diurnal variation, starburst and nocturnal glare was very low.
Discussion Radial keratotomy is clearly an effective procedure for the elimination or reduction of low myopia with a low complication rate. The major factor in the United Kingdom which prevents the procedure from being more widely applied is professional reluctance to recognise myopia as a justifiable reason for a surgical procedure. Ophthalmic surgeons in the United Kingdom are already overloaded with work related to patients with visual disability particularly with the management of cataract. It is therefore not surprising that low myopia and its management is regarded as having a low priority. The results achieved in the United Kingdom are every bit as good as those achieved and reported on in the United States of America and in other centres of known excellence. The future of refractive surgery of all sorts is dominated by the possible arrival of an effective form of excimer laser capable of creating on the surface of the cornea any desired refractive curvature by a process of photoablafion involving only the most superficial layers of the corneal stroma. Such a procedure, if it is found to
81
be effective and enduring is likely to be associated with a remarkably low complication rate and the floodgates of members of the public demanding relief from spectacle correctioh of all sorts may well be opened. How the ophthalmic surgical world will manage the possible demand is a problem which may yet have to be solved.
References Akiyama K, Tanaka M, Kanai A, Naka~ma A (1984) Problems arising from Sato's radial keratotomy procedure in Japan. CLAO Journal; 10: 179-184. Fyodorov S (1980) Surreal correction of myopia and astigmatism. In Schachar RA, Levy NS, Schachar L eds. Keratorefraction: Proceed-
~2
ings of the Keratorefractive Society Meeting, Denison. LAL Publishing; 141-172. Gelender H, Flyn HW, Mendelbaum SH (1982) Bacterial endophthalmitis following radial keratotomy. Am J Ophthalmol; 93:323. Lans LJ (1898) ExperimenteUe Untersuchungen uber Enstehung yon asfigmatissus durch nicht-perforirende corneawunden. Albrecht Von Graefes. Arch Ophthalmot.; 45: 117-152. Sato T (1950) Posterior incision of cornea: Surgical treatment for conical cornea and astigmatism. Am. J. Ophthatmol. 33: 943-948. Sato T, Akiyama K, Shibata H (1953) A new surgical approach to myopia. Am. I. Ophthalmol. 36: 823-829. Waring GO, Moffltt SD, Gelender H, Borque LB and the PERK Study Group. (1983) Rationale for and design of the National Eye Institute Prospective Evaluation of Radial Keratotomy (PERK) Study. Ophthalmology; 90: 40-58. Yenalief FS (I979) Experience in surgical treatment of myopia. Vestn OftalmoL; 3: 52-55.
Tr"~asactions BCI-A International Coherence 1988