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 Table of Contents  
HISTORY CORNER
Year : 2020  |  Volume : 32  |  Issue : 3  |  Page : 315-320

Sir Harold Ridley and the intraocular foreign body that made history


Department Of Ophthalmology, Regional Institute of Ophthalmology, Government Medical College, Thiruvananthapuram, Kerala, India

Date of Submission18-Oct-2020
Date of Acceptance19-Oct-2020
Date of Web Publication23-Dec-2020

Correspondence Address:
Dr. C Biju John
Regional Institute of Ophthalmology, Government Medical College, Thiruvananthapuram, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/kjo.kjo_160_20

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How to cite this article:
John C B. Sir Harold Ridley and the intraocular foreign body that made history. Kerala J Ophthalmol 2020;32:315-20

How to cite this URL:
John C B. Sir Harold Ridley and the intraocular foreign body that made history. Kerala J Ophthalmol [serial online] 2020 [cited 2021 Apr 22];32:315-20. Available from: http://www.kjophthal.com/text.asp?2020/32/3/315/304547



The operation theater register of St Thomas' Hospital, London, in the 1949–1950 period, contains two entries which are part of history now. Both described surgeries done on the left eye of a 45-year-old female by a certain L. Ridley. There was nothing unusual about the first entry, which was on November 29, 1949, and simply read “Extracapsular ext”[1],[2] [Figure 1]a.
Figure 1: (a and b) Reproduced with permission Original Entry in the OT register of St Thomas' Hospital on November 29, 1949 and February 8, 1950 (Source: A video of the logbook from 1949 showing summary of Sir Harold Ridley operations from 1949 and 1950 supplied by Prof. David Spalton in the ESCRS Video Collection (https://player.escrs.org/online-museum/logbook-from-1949-showing-summary-of-ridley-operations)

Click here to view


The second entry on February 8, 1950, however, was very unusual as the procedure is mentioned as “Lenticular Graft”[1],[2] [Figure 1]b. No such entry had ever been made in any operation theater register before. What it meant to the hospital and what it gave to the world is clarified by a decorative plaque [Figure 2] installed 50 years later at the hospital, which reads ”The first intraocular lens (IOL) for the treatment of cataract was implanted by Mr. Harold Ridley FRS at St Thomas' Hospital on 8th February 1950.”[3]
Figure 2: Plaque commemorating the world's first intraocular implantation at, St Thomas' Hospital, London, (Source: Wikipedia https://en.wikipedia.org/wiki/Harold_Ridley_(ophthalmologist))

Click here to view


However, for the surgeon himself, the seemingly usual first date and entry was the milestone date as he would clarify later in his publications and interviews and vehemently vouched for by his faithful nurse and operation theater assistant Ms. Doreen Ogg. She would explain later that in fact the first implantation of an IOL was performed on November 29, 1949. In written records, the operation on that date was referred to only as “Extracapsular ext.” Mention of an IOL was purposely omitted to retain the secrecy as requested by the surgeon.

Ms. Ogg also remembers vividly that Dr. Harold Ridley and the opticians who helped him design the IOL were totally disappointed when the patient had a postoperative myopia of about -18 D. She recalls that a second surgery was done months later, in which the first IOL was removed and the second one implanted. Hence, this must have been the “Lenticular Graft” on 8th February. Thus, both the register entries are historic – World's first IOL Implantation happened, in all probability on November 29, 1949, and the first IOL exchange on February 8, 1950.[1],[4]

The IOL was a warchild. It was born out of the 2nd World War and it created another world war in the ophthalmic world, a war which left its inventor badly bruised and battered, a war in which he was ridiculed, abused, and threatened with litigations, a war which saw many of the big names in ophthalmology join forces against him.

The ophthalmic world was not ready to accept the IOL. However, as Victor Hugo had said “Nothing is more powerful than an idea whose time has come.” The way this particular idea emerged and how it found the right person at the right time is a story of startling coincidences.

To begin with, the inventor of the IOL, Sir Nicholas Harold Lloyd Ridley (July 10, 1906–May 25, 2001), was never short of ideas. He was born as the elder of the two sons to Nicholas Charles Ridley and his wife Margaret Parker in Kibworth, Leicestershire, in England. At the age of 7 years, the shy-stammering boy once told his mother that he wanted to be an inventor.[3] He was always making new toys and all sorts of things in his childhood. In spite of not being a great communicator, he asked the right questions more often than not and ended up finding practical solutions. This very same nature was in display when during his house surgency at the St Thomas' Hospital, London; he encountered a young skilled work man whose career was brought to an abrupt halt by a traumatic cataract and intraocular foreign body in one eye. The man's work was such that binocular vision was essential. The young Ridley brooded over it and posed a question to two people whom he adored and worshipped most at that time, his father, who was then a consultant ophthalmic surgeon to the Royal Navy and his beloved teacher and mentor in the Department of Ophthalmology of St Thomas' hospital, Mr. A Cyril Hudson. “How nice it would be to put a new lens in his eye?”

The senior Ridley said it was impossible and dangerous. The answer of his teacher Mr. Hudson reflected the collective ophthalmic mindset at that time “We take foreign bodies out of eyes. We don't put them in.”[3] And, that was the end of the matter or so thought the senior men. But, unknown to them or even the questioner himself, the embers of the flame were residing deep inside that questioning mind waiting to be fanned. The fanning came eventually a decade later when Harold Ridley was working as a full-time ophthalmic surgeon at the famous Moorfields Eye Hospital, London.

It was in 1938 that Ridley got the coveted appointment as a full surgeon and permanent consultant at Moorfields Eye Hospital.[5] He had plenty of experience both professional and worldly under his belt by then, which included 6 months as casualty officer, 1 year of general surgery, 6 months in ophthalmology under Mr. A C Hudson, all at St Thomas' Hospital, followed by 1 year as ship's surgeon in various vessels and then an 18-month formal ophthalmology residency training at Moorfields in 1934–1935.


  The Forgotten Goggles and a Historic Foreign Body Top


As Dr. Ridley began spreading his wings at the Moorfield's, eighty miles away another young man, having obtained his wings 1 year back was beginning to make good use of it. This was Flight Lieutenant Gordon Mouse Cleaver of the Royal Air Force 601 Squadron. A set of curious coincidences starting with the outbreak of the Second World War in 1939 contrived to place Dr. Ridley in the flight lieutenants “flight path.” On August 13, 1940, the German Air force launched one of the fiercest aerial attacks on Britain , code named “Eagle Attack,”. The objective was to “Wipe out the British air Force from the sky”[4] and what resulted was one of the fiercest battles in the history of aerial warfare. The 601 Squadron was in the thick of things. On August 14, 1940, Gordon Cleaver took off into the battle in the “Hurricane” that was normally assigned to him. He survived the morning sortie and returned by noon. He was just entering the officer's mess for refreshments when he was called back for another “scramble” based on the radar warning. His plane, it seemed, was not ready and by pulling the choke Cleaver ended up flooding and incapacitating the engine. He was immediately allotted a brand new Hurricane by the commander and ordered to catch up. In his haste and confusion, he forgot the air man's goggles. He finished the combat, but while returning to base was ambushed by German fighter planes. The canopy of his cockpit made of Perspex (Commercial Polymethyl methacrylate [PMMA]) shattered under the enemy fire. Without the protection of his goggles, he was blinded instantly as multiple fragments of the Perspex penetrated into both his eyes. The brave pilot maintained control and flipped the plane upside down enabling him to just fall off from the plane and parachute down to safety.

The first words spoken by Cleaver to his friend and mate Jack Riddle when the latter visited him at the military hospital were.”Jack, tell them all to wear their goggles.”[5] Evidently, this was not an isolated problem.

Eventually, Cleaver was referred to Moorfield's Eye Hospital and this was where he came under Dr. Ridley's care. He was under treatment at Moorfields for several years during which about 18 surgeries were done on his eye and face to preserve some vision and several of them were performed by Dr. Harold Ridley. Many of these were for the removal of the Perspex pieces that had gone inside his eyes or embedded in the ocular coats. Eventually, one of the Cleaver's eyes (left) could be saved, and in spite of a large iris hole through which one Perspex piece had gone in and hit his lens and one or two pieces still inside, he was able to return to civilian life with reasonably good vision. The other eye was permanently blinded. This was when Ridley made the historic observation that the acrylic pieces in cleaver's eye did not seem to elicit any sort of inflammatory reaction. He observed the same phenomenon in several other pilots' eyes with similar foreign bodies. The old flame of an idea in his mind was rekindled. Was it the Eureka moment?


  A Fruitful Detour Top


The flames were soon doused as he found his plate full for the next 6–7 years by other pursuits in life. May 1941 turned out to be bitter sweet for Dr. Ridley, sweet because of his marriage to Elisabeth Weather hill and his entry into temporary military service as Major, Royal Army Medical Corps. The bitter part was that he found himself posted in Ghana, West Africa. Ridley was deeply distressed by this as he knew his surgical experience was going to be wasted there as it was not a place of any war action.[5] He also believed, perhaps rightly that Sir Stewart Duke Elder who was a very high ranking official in the Medical Corps at that time was behind this. He put 18 months of service in Ghana followed by a short period of service in Calcutta, India, and then finally in Rangoon, Burma. These years in the wilderness also saw significant contributions to ophthalmology coming from the irrepressible Ridley and included first of its kind papers on Onchocerciasis and Nutritional amblyopia based on his vast experiences in Ghana and Burma, respectively. The fundus drawing painted by Ridley showing the posterior pole changes in Onchocerciasis came to be known as the “Ridley Fundus.” He was given an early release from the army in 1945 and brought back to Britain to make use of his unparalleled experience in tropical ophthalmology to treat the refugees and prisoners returning after the war. Ridley was appointed honorary ophthalmologist, Ministry of Defense, and resumed duties with an affiliation at both St Thomas and Moorfields, performing surgeries in both hospitals.[5]

Dr. Ridley's inventive and enthusiastic mind found a new passion at this time, Electronics. With the help of Marconi's Wireless Telegraph Company, he became the first person to televise eye operations, first in black and white (1948) and later in color. He did pioneering work in electronic ophthalmoscopy which helped later in establishing principles of confocal microscopy and scanning laser ophthalmoscopy.[4]


  The Final Catalyst and the Fire Top


In 1930, a young house surgeon had innocently asked his father and teacher about the feasibility of putting an artificial lens inside the human eye. 17 years later, history turned the tables on the questioner. Major Harold Ridley found himself at the receiving end of his old heretical question. It came from a medical student (Stephen Perry) who after watching Ridley perform a cataract surgery remarked. “It is a pity that you can't replace the cataract with a clear lens.”[5] Ridley decided that it was time to change the answer. The old flame was back. There was no holding back of the idea now. Its time had come. This time Ridley knew exactly what material he was going to use for the lens. Gordon Cleaver and the other pilots whom he treated had taught him that. The 8-year follow-up of the Perspex (PMMA) pieces in Cleaver's and the other Pilot's eyes was to Ridley the preclinical study of his material.[4] However, he was acutely aware of the general sentiment of ophthalmologists toward foreign bodies inside the eye and wanted to keep things under wrap till he had concrete results.

One evening in 1948, a rather secretive meeting took place between two men in the back seat of a Bentley Car parked in a side road of Cavendish Square, London. One was the owner of the car, Dr. Harold Ridley and the other his friend John Pike, an optical scientist at Rayner and Keeler, a leading optical company in England. The cure of aphakia was perhaps established in the next 30 min in that car when the two men discussed and finalized the nitty-gritty and major principles of the first IOL implantation surgery.[4] Other materials such as glass and quartz were also considered for the implant and rejected. As for the site of implantation, the more accessible anterior chamber was considered and rejected. In Ridley's own words, he wanted the implant to be “just where the nature had placed a biconvex lens throughout the animal kingdom.” “Extracapsular extraction was preferred to the more fashionable intracapsular because it produced a stronger eye with the intact posterior capsule acting as a bulkhead within the globe.”[5] John Pike roped in his friend Dr. John Holt at the Imperial Chemical Industries to make some pure high quality Perspex, as the commercially available one was not pure. John Holt obliged and the material was made, which he named the Perspex clinical quality (CQ). Allvar Gullstrand's work and other known formulae helped them to fashion a lens with what they thought was the desired optical effect. The three of them Dr. Ridley, Dr. John Holt and John Pike agreed to forgo any financial reward to prevent colleagues from alleging it was a commercial venture and did not even apply for a patent.

The next step was to find a volunteer for the procedure. It had to be a patient with unilateral cataract who was able to work quite well with the other eye and for whom the loss of function in one eye would not be so bad. The patient had to understand the risks of the untried operation and be prepared for the possible loss of the defective eye. It took Ridley about 1 year to get the right candidate.[3],[4],[6] The patient was a 45-year-old hospital nurse named Elizabeth Attfield who had a cataract in her left eye. The lens was a simple disc with a peripheral groove, exquisitely manufactured by Rayner and Keeler from Perspex CQ, and given to Ridley at the cost of 18 Shillings (<1 pound).

The operation for which Dr. Ridley had been preparing, which he might have rehearsed a hundred times in his mind, was finally carried out in secrecy at the St Thomas' Hospital in the afternoon of November 29, 1949, and history was made. The confusion regarding the dates and why the plaque in St Thomas mentions 8th February as the historic date and still believed by many as the actual date have already been mentioned in the beginning of this article. As per the latter theory, the entire exercise was a 2-stage procedure and the IOL implantation happened in the second stage on February 8, 1950.

Ridley and John Pike had been a little too accurate in copying the radii of curvature of the human lens to their implant with the result that the first two patients were rendered highly myopic. However, they made the necessary adjustments with the result that the subsequent implants only produced anisometropia in the range of 2–3 diopters[7] [Figure 3].
Figure 3: Ridley Posterior Chamber intraocular lens (1949–1960) (Source: https://rayner.com/about-us/history/)

Click here to view



  The Wrong Ridley and an Ophthalmic World War Top


The 2nd, 3rd, and 4th implantations were done in Moorfield's hospital. A total of 8 such operations were done till 1951. Dr. Ridley wanted to keep everything secret for about 2 years by which he thought he would be sure about the results. However, another curious coincidence forced his hand. One of his implant patients, delighted after the surgery wanted to meet Dr. Ridley outside the hospital to give him a fee.[3] He looked up Ridley in the phone book, made an appointment, and presented himself at the office of “Dr. Ridley.” The problem was it was the wrong Ridley. It was the office of Dr. Frederick Ridley, another ophthalmologist. This happened as “F” came before “H” in the directory and the patient had selected the number of the first Dr. Ridley for fixing up the appointment. The news was out. So, to establish priority, he published about the IOL in the “St Thomas' Hospital Reports,” which was a low profile, not widely read journal. Subsequently, he published reports in the Lancet and also in BJO.

Arguably Dr. Ridley's IOL work cannot be claimed to have adhered to the present day ethical research principles, but then those were not well established at that time. However, one mistake was that the dean and the head of research of Moorfields Eye Hospital who also happened to be one of the most powerful men in British Ophthalmology at that time was kept in the dark about these implantations and that was a certain Sir Stewart Duke Elder. There was a row over it in and Ridley is reported to have virtually told Duke Elder that he did not see any reason to inform him about what he was doing. He was never forgiven for that and thus ensued one of the bitter battles in ophthalmology.

In July 1951, Ridley drove to the Oxford Ophthalmological Conference with high hopes of presenting his work there in a lecture allotted to him. In his car was his wife and two of his IOL implant patients with good postoperative vision. One had 20/20 unaided. He also had prepared a cine film of one of his implant operations.

Dr. Ridley's lecture was well prepared and presented, but the response was something for which he was not prepared at all. Barring a few greatly impressed people, most from USA and Britain showed little interest and there were some very hostile reactions. Sir Stewart Duke Elder and the prominent ophthalmologists repeatedly refused to even look at the patients. The film was never shown. The session was foreclosed by the deputy master and Dr. Ridley and his wife drove off quietly, missing the dinner arranged. His attempt at getting his work recognized at the US also met with a similar fate when he had to face an even more hostile reaction at the 57th session of the American Academy of Ophthalmology at Chicago in 1952. The comments of Derrik Veil the then Editor in Chief of the AJO who incidentally was a close friend of Sir Duke Elder were especially scathing. However, there were also people like Warren Reese who enthusiastically collected one Lens from Ridley, flew back to Philadelphia in his private plane, and implanted the same the next morning at Wills Eye Hospital, thus becoming the first implant surgeon in the United States.[4]

Dr. Ridley had hoped that his Oxford presentation would be a land mark day in the history of Ophthalmology. To quote David Apple, “Indeed, it was a landmark day, but not in the way he expected. Instead, it was the beginning of more than 30 years of personal trials and tribulations that led to health problems that plagued him for the rest of his life. Worse, it was the beginning of an unconscionable delay in the implementation of this new procedure, a delay that deprived an entire generation of patients of the benefits of the IOL.”[4]

Ridley did about 1000 IOL implantations with reasonable success. But, many of them had complications related to the instability and poor fixation of the rather heavy lens and uveitis in a few due to the cetrimide solution used for sterilization of the lenses. Eventually, 15%–20% of these lenses had to be explanted.[8] He was forced to abandon the procedure due to severe opposition, ostracization from the mainstream ophthalmology, fear of litigations, and report of a plethora of complications happening around the world due to poor quality IOLs and suboptimal surgery by many. The quality of some of these lenses even led to the joke that they would have made better IUDs than IOLs.[6] Many ophthalmologists who could never reconcile with the absolutely heretical idea of “putting things into the eye” viewed the IOL as a “time bomb.” Had Dr. Ridley access to things such as viscoelastics, operating microscopes, and capsulorhexis principles, the story would have played out differently.

Anyway, there were people like Ridley's favourite protégé Peter Choyce, Edward Epstein, Binkhorst, and Fyodrov to take the IOL story forward through the first-generation anterior chamber IOLs (1952–1962), iris-supported lenses (1953–1973), modern anterior chamber lenses (1963 onward), and finally back to modern posterior chamber IOLs from 1975 onward. In 1979, when almost simultaneously John Pierce of UK and Peter Sherring of US came up with the posterior chamber IOL design of today, it was the Ridley lens which was back again, this time with 2 haptics for fixation which made the central disc smaller and much lighter.[9] Its implantation place also returned to where Ridley had planned 30 years back, i.e., “where nature had placed a biconvex lens throughout the animal kingdom.” By 1980, posterior Chamber intraocular lenses got the Food and Drug Administration approval and finally Dr. Harold Ridley was vindicated in all respects.


  Recognition Finally Top


For 30 years after his historic IOL implantation, Dr. Harold Ridley received more of ridicule, abuse, and professional ostracism than recognition. There were times when he had to take medication for depression. But, things began to change after 1980. He is reported to have said at European Intraocular Implant Lens Council in 1986 “All you people have enjoyed your implant work, I'm sure, I suffered from it.” But from then on, at last in the last 15 years of his life, he began receiving the honor and recognition which was overdue. These included -1.Election to the Royal Society, London, in 1986 2.Doctor of Humane Letters, (DHL) conferred in 1989, by the Medical University of South Carolina, USA. 3.Publication of a detailed biography by David J Apple in the Survey of Ophthalmology in 1996(6)4.The Gullstrand Medal conferred by the Swedish Society of Medicine in 1992, 5.Being honoured at the annual meeting of the American Society of Cataract and Refractive Surgery in Seattle,Washington in April 1999. And finally to cap it all knighthood was conferred on him by Queen Elizabeth in February 2000 [Figure 4]. He was 92 years old and partly deaf at the time of his knighting. After the ceremony when he was asked what did the queen tell him, Sir Harold Ridley answered with a smile, “I couldn't hear a damn thing!”[4]
Figure 4: Investiture of knighthood on Harold Ridley by Queen Elizabeth II, February 9, 2000 (Source: Apple1, David J., Werner, Liliana, &amp; Werner, Leonardo P. Arquivos Brasileiros de Oftalmologia 2002;65:137-40. https://doi.org/10.1590/S0004-27492002000100025)

Click here to view



  History Filling up Some Dotted Lines Top


In 1940, multiple pieces of PMMA from an air plane canopy plunged a young pilot's world into darkness, but illuminated the mind of a young inventor. Forty-seven years later another PMMA piece, this time deliberately placed into the now retired pilot's eye brought him back into the world of light. This beautiful quirk of history was effected, when Dr. Eric Arnott, in 1987, did cataract surgery on Gordon Mouse Cleaver's only functional eye and implanted an IOL. And, the surgeon reported that there was still a piece of the original Perspex buried in the Cornea.

Two years later, it was the turn of the inventor to benefit from his own invention and he chose to receive it at exactly the same venue where he made the invention. Dr. Harold Ridley successfully underwent cataract surgery with IOL implantation in both his eyes at his favorite St Thomas' Hospital in 1989 and 1990.[4] He asked for GA for both surgeries and explained to the surgeon Michel Falcon “Well my boy if I am awake, I will be telling you what to do all the time.”[9] He would jokingly say about it later. “I am the only man to have invented his own operation.”[10]


  Humanitarian Services Top


The man who, as a little child had sat in the lap of the great Florence Nightingale (was a friend of his mother), who had spent 5 productive years in the service of the underprivileged people of the third world countries, whose life partner had grown up in India, will not be left far behind in humanitarian activities. He established the Ridley foundation in 1967 financed by his inherited assets to promote ophthalmological services in underprivileged countries and to help needy people especially nurses and their families in dire financial situations. Dr. Ridley along with his wife and another nurse used to make several visits to underdeveloped countries, training the local surgeons there in cataract surgery and rendering other help.


  Epitaph Top


Dr. Ridley was very specific about how he should be remembered. He said in an interview in his inimitable style.[3] “I am going to have on my tombstone: “He cured Aphakia.” People are then going to say 'Who was Aphakia?”. Well, he did not get a tombstone with that epitaph. But, the millions of intraocular lenses happily sitting in innumerable eyes all over the world literally enlightening and empowering the owners will be proclaiming exactly that silently.

Acknowledgement

I would like to place on record my sincere thanks to Dr Sobha Joseph, Consultant Ophthalmologist Birmingham Heartlands Hospital and Solihull Hospital, London who helped me immensely in getting relevant materials for this article. My sincere thanks also to Professor Dr David Spalton who gave permission to use a screen shot of Dr Ridley's surgical log book from the video he had supplied to the ESCRS Video Collection.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Trivedi RH, Apple DJ, Pandey SK, Werner L, Izak AM, Vasavada AR, et al. Sir Nicholas Harold Ridley. He changed the world, so that we might better see it. Indian J Ophthalmol 2003;51:211-6.  Back to cited text no. 1
[PUBMED]  [Full text]  
2.
Williams H. Casanova and the Spitfire Pilots Ophthalmology Documentaries. Available from: http://www.rcophth.ac.uk/about/rcophth/museum/#. [Last accessed on 2020 Sep 12].  Back to cited text no. 2
    
3.
Sir Harold Ridley-Science Museum Tribute 2. Available from: https://youtu.be/T7kj7GnCf9I. [Last accessed on 2020 Sep 14].  Back to cited text no. 3
    
4.
Apple DJ. Sir Nicholas Harold Lloyd Ridley. Biogr Mems Fell R Soc 2007;53:285-307.  Back to cited text no. 4
    
5.
Apple DJ. Harold Ridley and his fight for sight. He Changed the World so that we May Better See it; Slack Books; Slack Incorporated; 1st edition (September 10, 2006).  Back to cited text no. 5
    
6.
Apple DJ, Sims J. Harold Ridley and the Invention of the intraocular lens. Surv Ophthalmol 1996;40:279-92.  Back to cited text no. 6
    
7.
Williams HP. Sir Harold Ridley's vision. Br J Ophthalmol 2001;85:1022-3.  Back to cited text no. 7
    
8.
Hoffer KJ. The Evolution of the Intraocular Lens. Cataract Surgery. 3rd ed.. PART VI – Intraocular Lenses. Ch. 35. Elsevier Inc. 2010  Back to cited text no. 8
    
9.
Bhattacharya D. Tribute to Sir Harold Ridley (Video). Available from: https://www.youtube.com/watch?v=RkpssUDW2_Ehttps://www.youtube.com/watch?v=RkpssUDW2_E. [Last accessed on 2020 Sep 12].  Back to cited text no. 9
    
10.
Cataract Pioneer Sir Harold Ridley to be Honoured with Plaque: BBC News article on 18 February, 2012. Available from: https://www.bbc.com/news/uk-england-leicestershire-17076063. [Last accessed on 2020 Sep 09].  Back to cited text no. 10
    

Dr. Fredrick Ridley introduced the wet pack [soak in 10% NaOH for 1 h at 30°C, store in 0.1% NaOH, neutralize on use with 0.5% NaHCO3, rinse with saline] method of IOL sterilization which was used from 1957 to 1978


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]



 

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Recognition Finally
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