Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001

4. Menapace R, Amon M, Papapanos P et al: Evaluation of the first 100 consecutive PhacoFlex silicone lenses implanted in the bag through a self-sealing tunnel incision using the Prodigy inserter. J Cataract Refract Surg 20 : 299-309, 1994.

58, 1996.

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8. Kimura W, Kimura T, Sawada T et al: Postoperative decentration of three-piece silicone intraocular lenses. J Cataract Refract Surg 22(Suppl 2): 1996.

9. Auffarth GU, McCabe C, Wilcox M, et al: Centration and fixation of silicone intraocular lenses— Clinicopathological findings in human autopsy eyes. J Cataract Refract Surg 22(2):1281-84, 1996.

10.Mamalis N, Omar O, Veiga J et al: Comparison of two plate-haptic intraocular lenses in a rabbit model. J Cataract Refract Surg 22(2):1291-95, 1996.

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13.Shugar JK: Implantation of AcrySof acrylic intraocular lenses. J Cataract Refract Surg 22(2):135559, 1996.

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Eric J Arnott

I N T R O D U C T I O N

The current history of lens implantation dates back to the 1940s during the Second World War. In the war British fighter pilots frequently, among other serious injuries, had their eyes damaged with intraocular fragments from either their goggles, or canopy of their damaged aircraft. There are several documented reports of these pilots who flew either Hurricane or Spitfire fighter planes. Harold Ridley, at that time a young ophthalmic surgeon with an appointment in St Thomas Hospital, London, realized that the retained fragments of polymethylmethacrylate (PMMA) in the eye remained inert over the ensuing years.

He had been considering idea of “curing aphakia” with the insertion of a lens implant in patients having cataract surgery. In consultation with ICI, who made the plastic for the aircraft canopies and Rayners Optical, he produced the world’s first lens implant using this material. This was inserted into the eye of a patient having a cataract extraction, in November 1959, at St Thomas Hospital.

The original Ridley lens made of PMMA was one piece and diskoid shaped, very like the human lens. While at this time the intracapsular cataract operation was the one currently performed, Harold Ridley was yet again very advanced in his thinking. The operation was performed in conjunction with an extracapsular procedure. With sophisticated irrigating-aspirating systems not being available for removal of the soft lens cortex, this operation was limited to patients with a mature cataract.

The extracapsular procedure was relatively simple and quick. Under topical anesthesia using cocaine 4% guttae and with homatropine 2% guttae, to dilate the pupil, the eye was opened using a Graefe’s knife. This knife penetrated the

264 THE ART OF PHACOEMULSIFICATION

corneoscleral junction in the 3 O’clock meridian and exited at the 9 O’clock junction, keeping in this plane the knife swept along the corneoscleral junction to emerge from the eye in the 12 O’clock meridian. As much as possible of the anterior capsule was removed in one bite, using “extracapsular” toothed forceps. The nucleus was expressed from the eye in one piece and the residual cortex removed with saline irrigation. The lens was then implanted, into this posterior chamber.

While the initial results with this lens were excellent with no undue postoperative reaction it was relatively too heavy, being ten times heavier than current implants, and commonly dislocated into the vitreous cavity. Due to this problem after over 100 lenses had been successfully implanted this form of lens implant surgery was

abandoned.

In a retrogressive step succeeding lens designs were placed in the anterior chamber, usually in association with an intracapsular extraction. The result was that lens implantation entered the doldrums years for the next two decades. Poor lens materials and defective design caused many eyes to be lost, usually on account of corneal decompensation. The one-piece lens was modified to have a PMMA optical portion with the addition of nylon haptic loops. The distal portion of these haptics lying within the angle of the anterior chamber often rubbed against the endothelial layer of the cornea. Progressive loss of these cells, in even one area, would in time reduce the endothelium to such a low cell count that they could not maintain the relative dehydration and integrity of the cornea. An associated problem occurred with the gradual degradation of the nylon loops, which in time caused even greater instability of the lens.

SUBSEQUENT MODIFICATIONS

Modifications were made, with the lens once again being one-piece PMMA, with the haptic portion being fixated in the recess of the anterior chamber. These early modifications did not rectify the complications associated with peripheral endothelial corneal touch. Peter Choice solved the problem by producing a lens with a gullwing configuration to the distal portion of the haptic which kept it clear to the cornea. His style of lens modified by Tennant for the American market and Kelman giving if flexible loop haptics survives till the present time. It is currently used as a phakic lens for correction of myopic and hypermetropia errors of refraction.

In the late 1960s Binkhorst developed the “iris clip lens” which could, like the anterior chamber lens, be used in conjunction with either an intra or extracapsular extraction. With this style of lens the PMMA optic was supported by two sets of haptic loops which gave pupillary support fixation. In the original design of this lens, the loops gained fixation within the pupillary margin and the optical portion was prepupillary. Many modifications of these lenses were designed on the concept of pupillary fixation. Svyatoslav Fyodorov produced the “Sputnik” lens, so named as it appeared on the market at the same time as the first Russian satellite. Jorg Boberg-Ans and Eric Arnott made modifications with lenses, which had one-piece optics and posterior haptics in the posterior chamber, while retaining

the anterior loops. The Arnott lens had the anterior loops at right angles to the posterior haptics while the Boberg-Ans lens had the loops in line. A further design was made by Sanford Severin. If adequate pupillary fixation was achieved, good visual results were obtained. Frequently these lenses dislocated forwards into the anterior chamber or posteriorly into either the posterior chamber or vitreous cavity. Moreover fundus examination was difficult.

In 1974 Binkhorst and Worst claimed that the compartments of the eye remained

more stable with less “phakodonesis” in the presence of an extracapsular extraction. As a result of their observations most surgeons, at this time, converted from intracapsular extraction to extracapsular extraction. Binkhorst like Ridley before

him realized that the intact posterior capsule could act as a support for lens implant fixation. This led Binkhorst to develop a lens similar to his iris clip, but with the anterior loops removed. This lens depended for its fixation on the posterior capsule while still retaining an optical portion that was prepupillary.

The introduction of a one-piece PMMA lens with two integral solid haptics in 1974 by John Pearce heralded the return to posterior chamber lens implantation. It had taken 25 years, from the time of the original surgery by Harold Ridley in 1949, for surgeons to finally realize that the ideal position for an implant was in this area, where “The Almighty” had originally placed the “human” lens. Arnott, who at this time was actively working with Pearce at Charring Cross Hospital, London modified the bipod lens to a tripod, known as the Little-Arnott. Pearce also modified his lens to a tripod haptic design. These two lenses, manufactured by Rayners of England, gained a considerable market in the United Kingdom. William Harris of Dallas, the USA modified this design with a lens that was one piece, with quadrangular haptics. The rigidity of all these lenses did not allow for the variabilities of the diameter of the retropupillary space. If fixation did not occur on the posterior capsule some element of decentration could occur.

Posterior chamber lens implantation was totally revolutionized with the reintroduction by Steve Shering, in 1976, of a three-piece, mono plane, lens with optics of PMMA and two-loop haptics which were flexible; allowing for the variations of the dimensions within the posterior chamber of the eye. Shering introduced the “methodology” of placing a flexible loop lens into the posterior chamber of the eye, a system of surgery that has been upheld until the present day. This lens was almost identical to the Barroquer lens produced some twenty years earlier, for anterior chamber lens insertion. It differed fundamentally in that the haptic loops were made of polymethylmethacrylate and not nylon. They were non-biodegradable and therefore did not dissolve. The Shering lens determined the course of lens implantation for the next decade.

Modifications of this style of lens were designed Robert Richard Sinskey, William Simcoe, Dick Kratz, John Sheets and others. All these lenses were three-piece with PMMA optics and two haptic loops of varying configuration, requiring the presence of the posterior capsule for their fixation and an extracapsular cataract extraction. During the latter part of the 1970s and throughout the whole of the 1980s cataract surgery was undergoing a progressive change from simple

extracapsular extraction of the lens to “small incisional phacoemulsification and lens implantation”. Both of these procedures lended themselves very well to these forms of lens implantation. With the implants of this period having rigid optics of 5 mm diameter or more, if “phako” was used, the section into the eye, had to be enlarged for the insertion of the implant.

With all operations performed with extracapsular cataract extraction, whether with one piece removal of the nucleus, or “phako” postoperative problems often occurred due to opacification of the lens capsule. This was associated, in the first instance, with proliferation of the anterior subcapsular cells damaged during the making of the anterior capsulotomy undergoing metaplasia to form “pseudofibroplasts”. These cells, with the inflammatory reaction in the early postoperative period, could form opacification of the posterior capsule within the first weeks after surgery. Later opacification of the posterior capsule occurred from the spread of retained fornix cells germinating and spreading centripedally over the posterior

capsule.

While the proliferation of these traumatized anterior cells, becoming fibroblasts, could aid in fixation of the lens implant, the proliferation of the germinal cells were no more than an obstacle for vision.

Simcoe in 1982 had shown that a prolene loop lying on the posterior capsule of the lens could inhibit centripetal spread of germinating fornix cells over its surface. These concepts led Arnott to produce a lens with totally encircling PMMA loops, which, on contact with the posterior capsule, would block the spread of these germinal cells to the optic axis. At the same time good fixation could be achieved by the pseudo-fibroblasts produced by the traumatized anterior capsular cells. The first one-piece flexible PMMA lens was introduced in 1980 by Arnott, and Jaffe with totally encircling one-piece PMMA loops. This style of lens with various modifications and manufactured by Alcon dominated the American market for a number of years.

Other important lens styles at this time included the Anis totally encircling loop lens and the one-piece lenses made with soft material such as the “Iogel”. All these lenses relied on posterior capsular membrane support. With all forms of extracapsular cataract extraction (ECCE), be it one-piece removal of the nucleus, or “phaco”, the configuration of the anterior capsulotomy was inexact. As a result the haptics of the lens could lie either on the exposed surface of the posterior capsule or actually within the confines of the capsular bag. David Apple of the Storm Eye Institute showed some signs of decentration. With the variability of fixation of the opposing loops, either on the posterior capsule, or within the capsular bag decentration could occur. Lenses with the maximum arc of contact on the posterior capsule such as the Jaffe, Arnott, Anis or Simcoe showed the least incidence of decentration.

RECENT ADVANCES

The most dynamic change in the procedure came with the introduction of the capsulorrhexis perfected by Thomas Neumann and Howard Gimbel in 1987. This enhanced the concept of posterior chamber lens implantation. Not only was the

implant placed within the posterior chamber of the eye but it was inserted, through the round capsulorrhexis opening of the anterior capsule, to lie within the confines of the lens capsular bag itself.

In this surgical procedure of small incisional cataract extraction, removal of the nucleus by ultrasound or laser is obligatory. The implants currently available can be used in conjunction with this procedure, but having optics of 5 mm or more in diameter require an enlargement of the incision for their insertion.

This has led to the introduction of lenses being made with soft materials such as silicone, poly-HEMA, or acrylates, which can be folded, for insertion into the eye. Polymethylmethacrylate lenses, with slimmed-down optics, can also be used.

The present format of cataract and implant surgery encompasses a small incisional procedure, with a capsulorrhexis, and insertion of an implant totally within the confines of the capsular bag.

268 THE ART OF PHACOEMULSIFICATION

Tetsuro Oshika

I N T R O D U C T I O N

Acrylic foldable intraocular lens (IOL) (AcrySofTM, Alcon Laboratories Inc., Fig. 26.1) is composed of a copolymer of phenylethylacrylate and phenylethylmethacrylate which is crosslinked with 1,4 butanedial diacrylate.1 The IOL retains many of the advantageous physical properties of polymethylmethacrylate (PMMA), but is able to be folded. Its unique characteristics include a high refractive index of 1.55, making it the thinnest lens possible without compromising the optic diameter, and slow, controlled unfolding. The records of safety and efficacy of acrylic foldable IOL have been increasingly accumulated.

The advent and widespread distribution of foldable IOL have significantly contributed

to the growing and renewed interest in phacoemulsification. This was particularly true for acrylic foldable IOL, since it was not before the introduction of this lens to the market that a great deal of interest was generated and directed to small incision cataract surgery. Even though the silicone IOLs had been available for more than a decade, the combination of phacoemulsification and foldable IOL was not yet widely accepted.

IMPLANTATION TECHNIQUES OF ACRYLIC FOLDABLE IOL & ITS CLINICAL RESULTS 271

Fig. 26.10: The positioning of the grasping forceps relative to the slit on the folding forceps. The upper most part of the slit is the appropriate position to grasp

the forceps. It is very important to guide the distal haptic into the capsular bag before the whole optic enters and opens in the anterior chamber.

Once the leading haptic is placed beneath the capsulorrhexis margin, the implantation forceps is rotated clockwise (Fig. 26.14). Opening the forceps allows the optic to slowly unfold and be disengaged from the forceps (Fig. 26.15). By depressing and rotating the optic with the implantation forceps (Fig. 26.16), the proximal haptic is implanted into the capsular bag (Fig. 26.17). The non-slippery