- Email: [email protected]
The Teaching of Ophthalmic Surgery
Rayner Medal Lecture
The Teaching of Ophthalmic Surgery CHRISTOPHE HUBER
From a fascinating adventure lens implantation has become a safe routine all over the world. Let us thank the courageous generation of pioneers; Harold Ridley, Cornelius (Kees) Binkhorst, Edward Epstein, Peter Choyce, who started and won a beautiful battle. Not only was knowledge about lens implantation developed outside universities but it was from the field of private practice that this knowledge was taught to a multitude of ophthalmologists. I would like to discuss in this lecture problems related to the teaching of ophthalmology and cataract surgery. Eye surgery is a craft: it can be learned but it has to be taught. Ifwe accept the premise that good quality surgery for all potential patients is a reasonable aim we have to be concerned not to limit the number of surgeons but to help all of them acquire sufficient ability. I do not believe that a surgeon is born with a special gift like a musician or a great painter. I have taught too many surgeons, to believe that they are anything but exceptional. The job we do is astounding to the blind patient and they often consider the result as a miracle but, as one of my discerning patients asked me, 'How does it feel to be the instrument of a miracle?' This is exactly what the surgeon is: an instrument for something which can sometimes be a miracle. But nobody would consider the knife a miracle and we should therefore avoid basking in the sun of our successes. How can we manage to have a sufficient number of adequately trained surgeons? Meetings such as the present one will help trained surgeons to compare results, correct some problems and improve details; they are, however, not an efficient way of teaching surgery to a beginner. The only way to teach surgery is by a hands-on approach with a generous and patient teacher. The teacher has to be patient because he knows quite well that if he was doing the operation himself it would already be finished. He has to be generous, because if he teaches well the skills he has learned over many years will probably be mastered by his pupil in a much shorter time. Unfortunately some teachers are neither patient The Rayner Medal Lecture was delivered at UKIIS section 8th EIIC Congress (September 111990, Dublin) 0955-3681/91/010003+04 $03.00/0 © 1991 Bailliere Tindall
nor generous. I have heard academic teachers imply that their pupils should go the same hard way that they had to go and repeat the same learning steps all over again. Now this attitude is contrary to the whole development of modern scientific knowledge. Our pupils must be spared our errors so that they can build on the small improvements we have achieved, and hopefully become much better than we were and are. Teachers must also avoid ending their sentences without question marks and keep a sceptical mind about what they think they know. One of my teachers finished his lecture on cataract surgery with the sentence: 'As long as I am its head, nobody in this department will ever implant an intraocular lens'. Five years later Saulus had become Paulus and was starting with Binkhorst two loop lenses! A head of department who had taught ex cathedra that only 'superb' surgeons should be allowed to implant lenses revised his opinion 3 years later and affirmed then that only 'superb' surgeons should be allowed to implant in children. Another self-adoring professor told without blushing that one technique he performed was so difficult that he was not able to teach it to anyone! Knowledge you cannot teach has no place in science: it is just an anomaly in time. Knowledge that is not transmitted will not die, it will only be delayed, because however good a surgeon you are it is statistically improbable that you are a new Mozart unique for all time to come. A much practised argument for limiting the number of active surgeons is the idea that the more a surgeon operates the better he will be. This argument certainly holds for a certain critical but unknown number of cases. If you ask different surgeons the value of this number it will always be about twothirds of the number they operate themselves. There is, however, also a definite disadvantage in concentrating surgery in a few hands. Postoperative management will lie with ophthalmologists not aware ofthe intraoperative problems. Also, surgeons will see the serious complications but will not be warned in time when small problems occur. If your profession is limited to wielding the knife your ophthalmological visual field will progressively shrink to a lucrative but monotonous horizon. The best teacher I ever had was Kees Binkhorst, Eur J Implant Ref Surg, Val 3, March 1991
C. Huber
4
and I would like to relate one anecdote which illustrates an aspect of his teaching. At the end of a year I had spent with Kees I asked him whether I might copy some of his slides. The next morning I had a suitcase packed full of slides on my desk with the short commentary, 'These are all my presentations, copy what you need'. I also had another teacher who kept his slides under lock and key! Teachers and students are not very different: both species of ophthalmologists must keep learning and in their relations they must realize that they expect different things from their cooperation. The teacher wants an obedient helper and the student a fast way to fame and recognition. Both teacher and student will face the same two problems during their career: how to gain new knowledge and how to bring it over to a sometimes recalcitrant audience. I will discuss the second problem first. Doctors are conservative because of the many treatments tried over and over again which benefited no patient. Neither do they like people who question their ability. They will oppose new techniques and hypothesize in a manner similar to the attitude of academics described by Thomas More some 5 centuries ago: In such of a company, where some disdain and have despite at other men's inventions and some count their own best, if among such men a man should bring forth anything that he hath read done in times past or that he hath seen done in other places, there the hearers fare as though the whole existimation of their wisdom were injeopardy to be overthrown, and that ever after they should be counted for very dizzards, unless they could in other men's inventions pick out matter to reprehend and find fault at. If all other poor help fail, then this is their extreme refuge. These things, say they pleased our forefathers and ancestors: would God we could be so wise as they were. And as though they had wittily concluded the matter, and with this answer stopped every man's mouth they sit down again ... Many times have I chanced upon such proud, lewd, overtwart, and wayward judgements, yea, and once in England. Because of the disbelief of his audience a teacher will fight this resistance by showing no doubts at all about his new knowledge and commit another traditional error described by Bacon in the Advancement ofLearning (1605!): Another error is the manner of the tradition and delivery of knowledge, which is for the most part magistral and peremptory and not ingenous and faithful, in a form that may be soonest believed and most easily examined.
Unfortunately this attitude will only increase the resistance ofthe critical part of the audience. In gaining new knowledge we must avoid inventing the wheel over and over again. Most discoveries in the field of ophthalmology in the last 20 years were not basic scientific discoveries, but the application of technical knowledge available outside our own field. The idea of light transmitted over long distances to burn the sails of the enemy is already present in an illustration of Bacon's utopia and is even attributed to Archimedes. Medicine did not develop laser technology but thankfully applied it when available. Plexiglass, our much used PMMA, was discovered by Rohm in 1933 and used for a vast number of different applications: dishes, musical instruments, windshields, decorative panels. It needed, however, the extremely expensive and uncontrolled experiment of the Second World War, with the use ofthe material in the cockpit of Spitfires and B52 US bombers to show that the material was inert in the eye. This knowledge would have been nothing without the courage of Dr Ridley to apply it to eye surgery. The brains and the imagination of human beings do not change much over the centuries. We can make new combinations with the knowledge available but the way we think is identical to the way scientists did in Greece some 2000 years ago. I would like to illustrate this point with an example taken from graphic art. Those of you aware of computer pictures known under the generic name of'Mandelbrot set', know the aesthetic pleasure caused by the repetition of similar geometric figures with small changes in size or orientation. The same principles appear in different art forms over a multitude of cultures and centuries-in 'Art Deco' glazed windows of the turn of our century, in the geometric patterns of Arab art or in the fantastic animated letter of the book of Kells in Trinity College in Dublin. The important fact is that over time and different cultures our brains recognize similar patterns as beautiful. The common pattern is not in the art but in the brain of the viewers. As our brains always function in the same patterns we tend to invent the same things over and over again and sometimes also to repeat the same errors. A rotating cystitome proposed by Huisinga in the beginning of our century reappears as a new invention in an Alcon catalogue a few years ago, only to disappear as quickly as the first version of the instrument. The very positive advantage ofVorosmarthy's ocular compression might have been inspired by a very similar instrument dated 1803 used to staunch bleeding after enucleation. We should be more aware of things done in the time past in order to pick up good ideas that have been Eur J Implant Ref Surg, Vol 3, March 1991
Teaching of Ophthalmic Surgery
forgotten and to avoid repeating the same errors time and time again: Time seemeth to be of the nature of a river or stream, which carrieth to us that which is light and blown up, and sinketh and drowneth that which is weighty and solid (Bacon, 1603).
5
always carry it stooped towards the ground. They are very ugly brutes to look at. They are not at all such as we describe them when we relate that they let themselves be captured by virgin but clean contrary to our notions. In fact, what he saw as a unicorn was most probably a rhinoceros, a new and, to him, unknown animal which might soon for us also belong to a mythical past. I would like in the last part of my talk to implore the academics to further statistic knowledge in the newer generation of colleagues:
In the search for the perfect intraocular lenses many candidates have been proclaimed as the 'lens for all seasons' able to solve all problems. Every new lens is proclaimed as the 'lens for all seasons': easy to insert, eliminating all complication and cheap in the bargain. Now, the experience with Another error is the over early reduction of knowiris-supported lenses and with mobile lenses for ledge into arts and methods, from which time comexample has taught me that everything that moves monly sciences receive small or no augmentation inside the eye is dangerous. Soft lenses have intro(Bacon, 1603). duced the unknown complication of luxation in the vitreous after laser capsulectomy. Large lenses that Statistics are something we often use with little would never decentre have, nevertheless, achieved common sense. They are required by the editors of notable degrees of decentration after a few years, journals. In some cases statistics will add to the value when asymmetrical capsular flaps were used. of a paper, in some cases it will only confuse the In 1982 a complicated system of a mobile 10L fixed reader. on a small rail was proposed to achieve accommoIn an example taken from Scientific American a dation. This mobile 10L was to be pulled forward or graph showed a strong correlation between the pushed backwards with the help of a small magnet number of nesting storks in West Germany and the worn by the patient on a gold chain around the neck! number of newborn humans during the same time This absolutely dangerous idea to my biological eye period. You might with a statistical test prove a high was published in a truly criminal form. The paper, degree of statistical significance, that the storks have full of pseudoscientific madness and detailed advice something to do with the babies. This is to remind you on the operating technique but with no case descripthat you cannot prove anything by statistics alone. tion, was published privately in such a shape as to You have to show how the correlation is brought resemble a reprint from a respected journal. The about. If a correlation cannot stand a statistical test paper would never have passed a reviewer and this then it just is not present. One reads in some papers illustrates the necessity of having all scientific that a relation was not proven statistically but there papers strictly refereed before being published. seemed to be a tendency. This is just humbug: if it is New knowledge is often not accepted because it is not statistically confirmed then there is no tendency. uncomfortable. The atypical inflammation of the anIn a recent article on the predictions of anterior terior chamber after lens implantation was certainly chamber depth after 10L I had difficulty using the different from a fulminant panophthalmitis and the proposed data (J. Cat. Ref Surg., 1990; 16: 202-210). ophthalmological community discovered the new The conclusion of the paper is that the depth of the syndrome of the sterile hypopion. Some ofthose reacanterior chamber after lens implantation can be pretions were probably due to toxic products inserted dicted with a complex equation. The proposed with the 10L but some of them, ·as Dr Apple has formula looks like a mediaeval drug prescription or shown, were still low grade and localized infections. the recipe of an exotic dish: Those infections did not look like panophthalmitis and we were not ready to recognize something that Take one hundredth of the patients age, add sevenlooked different but was the same thing. Marco Polo tenths of the preoperative ACD, add one-twentieth in Java had a similar problem the other way round. of the axial length and 2.4 mm. Then add the LPCD He saw something which was different from what he (lens posterior capsule distance?). And finally add thought he knew. the lens thickness. They have plenty of unicorn which are scarcely smaller than elephants. They have the hair of a bufallo and feet like an elephant's. They have a single large black thorn but in the middle of the forehead. They have a head like a wild boar's and Eur J Implant Ref Surg, Vol 3, March 1991
This last requirement I certainly cannot fulfil because to know the thickness I have to know the power. And the whole calculation of the postoperative depth is a preliminary calculation to compute this power.
C. Huber
6
Even if I could meet all these requirements and collect all the items of the recipe the final predictive power would not be much better than that found by using the mean of the postoperative ACD. In the first part of this paper, all biometric data are considered to be normally distributed. This is curious, both for the age of the patients as well as for the distribution of the axial lengths which usually show a definite asymmetry towards myopia and do not show a normal distribution in any random population of cataract patients. Scientific knowledge should give us some power over nature. Weak correlation has no useful predictive value. Such methods must be tested in a prospective study to show whether they can improve the prediction of postoperative ametropia. If they do not, they do not make much sense. Even if statistically valid. As a last example I want to illustrate a valid way to bluff the unaware reader. Figure 1 is taken from the famous PERK study on Radial Keratotomy and shows the relationship between preoperative and postoperative cycloplegic refraction. In the diagram ro
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Cycloplegic Refraction at base line Fig. 2 Stretch extortion (normalization)
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Normalized from PERK
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The contrary procedure to compressive calming is the stretch extortion. In the second diagram (Figure 2) I have normalized the data by performing a vertical stretch to equalize the dioptre scale on both axes. The
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result of the study definitely does not look so good in the second figure. Now compressive calming and + .... :.......:"0:.-, ........ '1 .- •• • - : •............. c stretch extortion are not lies, they are just a way of o • .\. \::.. ':.,. ••: ..,;-).(. '.1 - 1 .. :.~: ·1· .. "~JI ....... . illuminating what you have found, a small piece of ...,o(,) ..:':: ...... : ':.:~.- i-i• • -: . -2 I " : ••., , magic illusion to make facts look more beautiful than ro -3 .. I.. . .. .,.. . . .. Iftyou know they are. . ':..- ... -4 Q) IWhat conclusions can I make at the end of this -5 (,) -6 disordered speech? The ability and knowledge of an 0) -7 individual are not constants. As soon as you stop Q) -8~--~----~--~--~r---~---r a. learning you begin to fade and forget. If you have o -2 -4 -3 -8 -6 -5 -7 nothing to teach it is high time that you started (,) >learning. Medical knowledge must be common knowu Cycloplegic Refraction at base line ledge because if you keep something useful a secret PERK- Ophthalmology 92 - 1985 you will prevent some patient from getting help and Fig. 1 Compressive calming this is unethical. Keep looking at discoveries outside your own field. one notices that the length of a dioptre on the vertical Finally, a few words by Einstein which could bring axis is shorter than the length of a dioptre on the us a great deal further: horizontal axis. The vertical axis has been reduced in Scientific curiosity is due to an irresistible urge to size in relation to the horizontal axis in spite of the know how nature works. Humanity, social fact that the same quantity is measured on both axes. interests, fame or money have nothing to do with it. This graphical method, described as compressive Scientific knowledge is a reward by itself. calming by Dewdney in the mathematical recreation of Scientific American, is used by bankers who want And this from a man who knew what real science was to make changes in stock appear smaller than they and who, during the whole of his life, showed a great really are. interest in human and social problems.
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Eur J Implant Ref Surg, Vol 3, March 1991
The Teaching of Ophthalmic Surgery CHRISTOPHE HUBER
From a fascinating adventure lens implantation has become a safe routine all over the world. Let us thank the courageous generation of pioneers; Harold Ridley, Cornelius (Kees) Binkhorst, Edward Epstein, Peter Choyce, who started and won a beautiful battle. Not only was knowledge about lens implantation developed outside universities but it was from the field of private practice that this knowledge was taught to a multitude of ophthalmologists. I would like to discuss in this lecture problems related to the teaching of ophthalmology and cataract surgery. Eye surgery is a craft: it can be learned but it has to be taught. Ifwe accept the premise that good quality surgery for all potential patients is a reasonable aim we have to be concerned not to limit the number of surgeons but to help all of them acquire sufficient ability. I do not believe that a surgeon is born with a special gift like a musician or a great painter. I have taught too many surgeons, to believe that they are anything but exceptional. The job we do is astounding to the blind patient and they often consider the result as a miracle but, as one of my discerning patients asked me, 'How does it feel to be the instrument of a miracle?' This is exactly what the surgeon is: an instrument for something which can sometimes be a miracle. But nobody would consider the knife a miracle and we should therefore avoid basking in the sun of our successes. How can we manage to have a sufficient number of adequately trained surgeons? Meetings such as the present one will help trained surgeons to compare results, correct some problems and improve details; they are, however, not an efficient way of teaching surgery to a beginner. The only way to teach surgery is by a hands-on approach with a generous and patient teacher. The teacher has to be patient because he knows quite well that if he was doing the operation himself it would already be finished. He has to be generous, because if he teaches well the skills he has learned over many years will probably be mastered by his pupil in a much shorter time. Unfortunately some teachers are neither patient The Rayner Medal Lecture was delivered at UKIIS section 8th EIIC Congress (September 111990, Dublin) 0955-3681/91/010003+04 $03.00/0 © 1991 Bailliere Tindall
nor generous. I have heard academic teachers imply that their pupils should go the same hard way that they had to go and repeat the same learning steps all over again. Now this attitude is contrary to the whole development of modern scientific knowledge. Our pupils must be spared our errors so that they can build on the small improvements we have achieved, and hopefully become much better than we were and are. Teachers must also avoid ending their sentences without question marks and keep a sceptical mind about what they think they know. One of my teachers finished his lecture on cataract surgery with the sentence: 'As long as I am its head, nobody in this department will ever implant an intraocular lens'. Five years later Saulus had become Paulus and was starting with Binkhorst two loop lenses! A head of department who had taught ex cathedra that only 'superb' surgeons should be allowed to implant lenses revised his opinion 3 years later and affirmed then that only 'superb' surgeons should be allowed to implant in children. Another self-adoring professor told without blushing that one technique he performed was so difficult that he was not able to teach it to anyone! Knowledge you cannot teach has no place in science: it is just an anomaly in time. Knowledge that is not transmitted will not die, it will only be delayed, because however good a surgeon you are it is statistically improbable that you are a new Mozart unique for all time to come. A much practised argument for limiting the number of active surgeons is the idea that the more a surgeon operates the better he will be. This argument certainly holds for a certain critical but unknown number of cases. If you ask different surgeons the value of this number it will always be about twothirds of the number they operate themselves. There is, however, also a definite disadvantage in concentrating surgery in a few hands. Postoperative management will lie with ophthalmologists not aware ofthe intraoperative problems. Also, surgeons will see the serious complications but will not be warned in time when small problems occur. If your profession is limited to wielding the knife your ophthalmological visual field will progressively shrink to a lucrative but monotonous horizon. The best teacher I ever had was Kees Binkhorst, Eur J Implant Ref Surg, Val 3, March 1991
C. Huber
4
and I would like to relate one anecdote which illustrates an aspect of his teaching. At the end of a year I had spent with Kees I asked him whether I might copy some of his slides. The next morning I had a suitcase packed full of slides on my desk with the short commentary, 'These are all my presentations, copy what you need'. I also had another teacher who kept his slides under lock and key! Teachers and students are not very different: both species of ophthalmologists must keep learning and in their relations they must realize that they expect different things from their cooperation. The teacher wants an obedient helper and the student a fast way to fame and recognition. Both teacher and student will face the same two problems during their career: how to gain new knowledge and how to bring it over to a sometimes recalcitrant audience. I will discuss the second problem first. Doctors are conservative because of the many treatments tried over and over again which benefited no patient. Neither do they like people who question their ability. They will oppose new techniques and hypothesize in a manner similar to the attitude of academics described by Thomas More some 5 centuries ago: In such of a company, where some disdain and have despite at other men's inventions and some count their own best, if among such men a man should bring forth anything that he hath read done in times past or that he hath seen done in other places, there the hearers fare as though the whole existimation of their wisdom were injeopardy to be overthrown, and that ever after they should be counted for very dizzards, unless they could in other men's inventions pick out matter to reprehend and find fault at. If all other poor help fail, then this is their extreme refuge. These things, say they pleased our forefathers and ancestors: would God we could be so wise as they were. And as though they had wittily concluded the matter, and with this answer stopped every man's mouth they sit down again ... Many times have I chanced upon such proud, lewd, overtwart, and wayward judgements, yea, and once in England. Because of the disbelief of his audience a teacher will fight this resistance by showing no doubts at all about his new knowledge and commit another traditional error described by Bacon in the Advancement ofLearning (1605!): Another error is the manner of the tradition and delivery of knowledge, which is for the most part magistral and peremptory and not ingenous and faithful, in a form that may be soonest believed and most easily examined.
Unfortunately this attitude will only increase the resistance ofthe critical part of the audience. In gaining new knowledge we must avoid inventing the wheel over and over again. Most discoveries in the field of ophthalmology in the last 20 years were not basic scientific discoveries, but the application of technical knowledge available outside our own field. The idea of light transmitted over long distances to burn the sails of the enemy is already present in an illustration of Bacon's utopia and is even attributed to Archimedes. Medicine did not develop laser technology but thankfully applied it when available. Plexiglass, our much used PMMA, was discovered by Rohm in 1933 and used for a vast number of different applications: dishes, musical instruments, windshields, decorative panels. It needed, however, the extremely expensive and uncontrolled experiment of the Second World War, with the use ofthe material in the cockpit of Spitfires and B52 US bombers to show that the material was inert in the eye. This knowledge would have been nothing without the courage of Dr Ridley to apply it to eye surgery. The brains and the imagination of human beings do not change much over the centuries. We can make new combinations with the knowledge available but the way we think is identical to the way scientists did in Greece some 2000 years ago. I would like to illustrate this point with an example taken from graphic art. Those of you aware of computer pictures known under the generic name of'Mandelbrot set', know the aesthetic pleasure caused by the repetition of similar geometric figures with small changes in size or orientation. The same principles appear in different art forms over a multitude of cultures and centuries-in 'Art Deco' glazed windows of the turn of our century, in the geometric patterns of Arab art or in the fantastic animated letter of the book of Kells in Trinity College in Dublin. The important fact is that over time and different cultures our brains recognize similar patterns as beautiful. The common pattern is not in the art but in the brain of the viewers. As our brains always function in the same patterns we tend to invent the same things over and over again and sometimes also to repeat the same errors. A rotating cystitome proposed by Huisinga in the beginning of our century reappears as a new invention in an Alcon catalogue a few years ago, only to disappear as quickly as the first version of the instrument. The very positive advantage ofVorosmarthy's ocular compression might have been inspired by a very similar instrument dated 1803 used to staunch bleeding after enucleation. We should be more aware of things done in the time past in order to pick up good ideas that have been Eur J Implant Ref Surg, Vol 3, March 1991
Teaching of Ophthalmic Surgery
forgotten and to avoid repeating the same errors time and time again: Time seemeth to be of the nature of a river or stream, which carrieth to us that which is light and blown up, and sinketh and drowneth that which is weighty and solid (Bacon, 1603).
5
always carry it stooped towards the ground. They are very ugly brutes to look at. They are not at all such as we describe them when we relate that they let themselves be captured by virgin but clean contrary to our notions. In fact, what he saw as a unicorn was most probably a rhinoceros, a new and, to him, unknown animal which might soon for us also belong to a mythical past. I would like in the last part of my talk to implore the academics to further statistic knowledge in the newer generation of colleagues:
In the search for the perfect intraocular lenses many candidates have been proclaimed as the 'lens for all seasons' able to solve all problems. Every new lens is proclaimed as the 'lens for all seasons': easy to insert, eliminating all complication and cheap in the bargain. Now, the experience with Another error is the over early reduction of knowiris-supported lenses and with mobile lenses for ledge into arts and methods, from which time comexample has taught me that everything that moves monly sciences receive small or no augmentation inside the eye is dangerous. Soft lenses have intro(Bacon, 1603). duced the unknown complication of luxation in the vitreous after laser capsulectomy. Large lenses that Statistics are something we often use with little would never decentre have, nevertheless, achieved common sense. They are required by the editors of notable degrees of decentration after a few years, journals. In some cases statistics will add to the value when asymmetrical capsular flaps were used. of a paper, in some cases it will only confuse the In 1982 a complicated system of a mobile 10L fixed reader. on a small rail was proposed to achieve accommoIn an example taken from Scientific American a dation. This mobile 10L was to be pulled forward or graph showed a strong correlation between the pushed backwards with the help of a small magnet number of nesting storks in West Germany and the worn by the patient on a gold chain around the neck! number of newborn humans during the same time This absolutely dangerous idea to my biological eye period. You might with a statistical test prove a high was published in a truly criminal form. The paper, degree of statistical significance, that the storks have full of pseudoscientific madness and detailed advice something to do with the babies. This is to remind you on the operating technique but with no case descripthat you cannot prove anything by statistics alone. tion, was published privately in such a shape as to You have to show how the correlation is brought resemble a reprint from a respected journal. The about. If a correlation cannot stand a statistical test paper would never have passed a reviewer and this then it just is not present. One reads in some papers illustrates the necessity of having all scientific that a relation was not proven statistically but there papers strictly refereed before being published. seemed to be a tendency. This is just humbug: if it is New knowledge is often not accepted because it is not statistically confirmed then there is no tendency. uncomfortable. The atypical inflammation of the anIn a recent article on the predictions of anterior terior chamber after lens implantation was certainly chamber depth after 10L I had difficulty using the different from a fulminant panophthalmitis and the proposed data (J. Cat. Ref Surg., 1990; 16: 202-210). ophthalmological community discovered the new The conclusion of the paper is that the depth of the syndrome of the sterile hypopion. Some ofthose reacanterior chamber after lens implantation can be pretions were probably due to toxic products inserted dicted with a complex equation. The proposed with the 10L but some of them, ·as Dr Apple has formula looks like a mediaeval drug prescription or shown, were still low grade and localized infections. the recipe of an exotic dish: Those infections did not look like panophthalmitis and we were not ready to recognize something that Take one hundredth of the patients age, add sevenlooked different but was the same thing. Marco Polo tenths of the preoperative ACD, add one-twentieth in Java had a similar problem the other way round. of the axial length and 2.4 mm. Then add the LPCD He saw something which was different from what he (lens posterior capsule distance?). And finally add thought he knew. the lens thickness. They have plenty of unicorn which are scarcely smaller than elephants. They have the hair of a bufallo and feet like an elephant's. They have a single large black thorn but in the middle of the forehead. They have a head like a wild boar's and Eur J Implant Ref Surg, Vol 3, March 1991
This last requirement I certainly cannot fulfil because to know the thickness I have to know the power. And the whole calculation of the postoperative depth is a preliminary calculation to compute this power.
C. Huber
6
Even if I could meet all these requirements and collect all the items of the recipe the final predictive power would not be much better than that found by using the mean of the postoperative ACD. In the first part of this paper, all biometric data are considered to be normally distributed. This is curious, both for the age of the patients as well as for the distribution of the axial lengths which usually show a definite asymmetry towards myopia and do not show a normal distribution in any random population of cataract patients. Scientific knowledge should give us some power over nature. Weak correlation has no useful predictive value. Such methods must be tested in a prospective study to show whether they can improve the prediction of postoperative ametropia. If they do not, they do not make much sense. Even if statistically valid. As a last example I want to illustrate a valid way to bluff the unaware reader. Figure 1 is taken from the famous PERK study on Radial Keratotomy and shows the relationship between preoperative and postoperative cycloplegic refraction. In the diagram ro
ro Q)
>Q)
c
o
..., ro
c
o
...,
(,)
ro
I-
ftQ)
I(,)
Ol Q)
a. o (,)
>u
+4
+3 +2 + 1
I I,..
•I
o -
I
-4 -5 -6 -7 -8
:
1.1 "
I
I..
.:'
.1, ~ .. '
... :~.. t.lrl,..11
:-
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, • II,':, ,'I,.,',' ...rlh'I~~l1 U • ,',11 1 111.\ .. r~ Itll
1
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Cycloplegic Refraction at base line Fig. 2 Stretch extortion (normalization)
Q)
>~
I-
Normalized from PERK
I-
o
The contrary procedure to compressive calming is the stretch extortion. In the second diagram (Figure 2) I have normalized the data by performing a vertical stretch to equalize the dioptre scale on both axes. The
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result of the study definitely does not look so good in the second figure. Now compressive calming and + .... :.......:"0:.-, ........ '1 .- •• • - : •............. c stretch extortion are not lies, they are just a way of o • .\. \::.. ':.,. ••: ..,;-).(. '.1 - 1 .. :.~: ·1· .. "~JI ....... . illuminating what you have found, a small piece of ...,o(,) ..:':: ...... : ':.:~.- i-i• • -: . -2 I " : ••., , magic illusion to make facts look more beautiful than ro -3 .. I.. . .. .,.. . . .. Iftyou know they are. . ':..- ... -4 Q) IWhat conclusions can I make at the end of this -5 (,) -6 disordered speech? The ability and knowledge of an 0) -7 individual are not constants. As soon as you stop Q) -8~--~----~--~--~r---~---r a. learning you begin to fade and forget. If you have o -2 -4 -3 -8 -6 -5 -7 nothing to teach it is high time that you started (,) >learning. Medical knowledge must be common knowu Cycloplegic Refraction at base line ledge because if you keep something useful a secret PERK- Ophthalmology 92 - 1985 you will prevent some patient from getting help and Fig. 1 Compressive calming this is unethical. Keep looking at discoveries outside your own field. one notices that the length of a dioptre on the vertical Finally, a few words by Einstein which could bring axis is shorter than the length of a dioptre on the us a great deal further: horizontal axis. The vertical axis has been reduced in Scientific curiosity is due to an irresistible urge to size in relation to the horizontal axis in spite of the know how nature works. Humanity, social fact that the same quantity is measured on both axes. interests, fame or money have nothing to do with it. This graphical method, described as compressive Scientific knowledge is a reward by itself. calming by Dewdney in the mathematical recreation of Scientific American, is used by bankers who want And this from a man who knew what real science was to make changes in stock appear smaller than they and who, during the whole of his life, showed a great really are. interest in human and social problems.
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Eur J Implant Ref Surg, Vol 3, March 1991