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Some Aspects of Implant Surgery
PERSONAL VIEW
Some Aspects of Implant Surgery J.G.F. WORST and l.1. LOS Department of Ophthalmology, Refaja Hospital, Stadskanaal, Holland and Jan Worst Research Group, Haren, Holland
In the rapidly developing field of cataract and refractive surgery many techniques and lens designs are introduced and propagated. As it is not always easy to decide which line to follow, some of the author's (J.W.) basic principles will be presented here, mainly regarding cataract surgery. Furthermore the intraocular lens of his first choice in almost all cataract extractions-the Lobster Claw Lens-will be described, plus a modification thereof for implantation in high myopia. Keywords: ICCE; ECCE; Cataract backlog; Lobster Claw Lens; Secondary cataract; High myopia; Stainless steel sutures
INTRODUCTION
Implant and refractive surgery techniques are rapidly developing nowadays. New techniques are continuously introduced and new lens designs proposed and propagated. Since it is not always easy for the individual surgeon to decide which line to follow, some basic principles will be indicated here and will be illustrated with some instruments and techniques. Finally a short description of the Lobster Claw Lens will be presented and a special modification given for implantation in high myopia. An important basic principle is to obtain experience with simple, safe and effective techniques. By this means implant surgery will be prevented from becoming 'high tech'; an expensive field which limits such techniques to the economically privileged. The undesirability of this will be evident by considering the enormous cataract backlog currently present and increasing, mainly in developing countries fl1. SURGICAL TECHNIQUE AND INSTRUMENTS
1. Anaesthesia. General anaesthesia is given on special indication only. If general anaesthesia is administered, care must be taken to avoid venous congestion. A logistic important advantage of local anaesthesia is that it can be deli vered by paramedics, requires fewer instruments and is applicable in outpatient surgery. Local anaesthesia consists of a retroPlease address all correspondence to: Jan Worst Research Group, Julianalaan 11,9751 BM Haren, The Netherlands. 0955-3681/91/020157+ 11 $03.0010 © 1991 Bailliere Tindall
bulbar injection (Fig. lA-D) ofxylocaine. Hyaluronidase and adrenaline are routinely added to this anaesthetic [2]; the latter is omitted if cardiovascular contra indications exist. Additional parabulbar injections with the same mixture are given. Superior rectus anaesthesia (Fig. 2) is given in order to prevent external pressure on the eye. An optimal anaesthetic and akinetic effect is obtained by giving ocular compression and massage for at least 10 min until pressure has dropped below 10mmHg. Low vitreous pressure will decrease the incidence of complications during cataract surgery. Total immobility of the eye and eyelids indicates a correctly applied anaesthesia; ocular pressure can be measured preoperatively by the applanation of a sterile 2 cc syringe filled with water (Fig. 3). PREPARATION OF THE OPERATING FIELD
An important technique in preventing contamination of the operating field is the use of an airflow system. In addition to this the skin and eyelashes of the patient are completely covered by steridrape in such a way that no fluid-filled pockets will form between the drape and the patient's skin (Fig. 4). An adhesive malleable disposable lidholder can be used to prevent external pressure on the eye (Fig. 5). CATARACT EXTRACTION (ICCE AND ECCE)
There is at present a strong tendency to perform ECCE, since this method will preserve the posterior Eur J Implant Ref Surg, Vol 3, June 1991
J.G.F. Worst, LI. Los
158
Fig. Ie Correct position of the needle with the curved tip for retrobulbar injection-lateral view
Fig. lA Retrobulbar injection of local anaesthetic into the lower temporal area. The patient looks in the upper nasal direction. A sharp 24 G needle with a curved tip is used
Fig. ID As Fig. IC, but front view
Fig. 18 The 24 G injection needle is curved 45° at about 5 mm
distance from the tip
lens capsule, thus presenting a possibility for posterior chamber lens fixation. Furthermore the intact posterior lens capsule (and more importantly, an intact anterior vitreous membrane) will form a biological 'watershed' between the anterior and the pos-
terior eye segment, thus maintaining an anatomical and physiological integrity of the various compartments. Vitreous loss will be prevented in most cases. Generally speaking this is the correct approach which by respecting the normal anatomical situation will avoid posterior segment pathology. The natural barrier between anterior and posterior eye segment should be carefully respected, especially in young people, since 'decompartmentalization' in this age Eur J Implant Ref Surg, Vol 3, June 1991
Some Aspects of Implant Surgery
159
Fig.4 Preparation of the operative field: skin and eyelashes are covered by steridrape
\....... ,-r,.
Fig.2 Parabulbar injection through the superior eyelid (superior rectus anaesthesia ). Anaesthetic is injected while retracting the needle
::" :';
.
·····.i:...:...··
Fig. 5
Fig.3 A waterfilled 2cc syringe is applied to the anaesthetized cornea to measure preoperative lOP by applanation. lOP is read as follows: Applanation (number of divisions) 2 3 3.5 4
Schiiitz (mmHg) c. 30 c. 25
c. 20 c.15
5 lines or more indicates a safe preoperative pressure
group will lead to unfavourable results [31. This is associated with the following pathological conditions: 1. Cystoid macular oedema. 2. Aphakic retinal detachment. 3. Vitritis. 4. The irritable eye. In eyes with mature cataracts, however, the anatomical situation is essentially different and ICCE is Eur J Implant Ref Surg, Vol 3, June 1991
.
:.: . :.:
Disposable Iidholder
possible without disturbing normal physiological conditions (i.e. integrity of the anterior vitreous membrane). This is evident in people over 75 years of age, who generally have anterior and posterior vitreous detachments due to involution of the vitreous body. Another prerequisite is the presence of a weak zonule. In heavily pigmented eyes the anatomical condition of the posterior segment seems to prevent cystoid macular oedema (CMO) after ICCE, even in younger eyes (about 40 years) with mature cataracts [M. Hogeweg, N. Christy, P. Lall, personal communications]. Therefore, we hypothesize an anatomical or physiological difference between blue and brown eyes. If performed under proper conditions, ICCE by cryoextraction still has an important place in cataract surgery, all the more so because of its evident advantages. This method is relatively cheap, easy to perform, quick and will not present the one major problem of ECCE-the formation of a second.~ ary cataract. Intracapsular cataract extraction cannot be performed on very young patients and it is also a disadvantage of ICCE that it is not possible to implant a
160
J.G.F. Worst, L.I. Los
posterior chamber lens. A good alternative is the implantation of an Iris Claw/Lobster Claw Lens. Because the Lobster Claw Lens is fixated to the midperipheral iris, implantation can be performed after ICCE as well as ECCE. The major problem which occurs after ECCE is the formation of a secondary cataract (Fibrosis, Elschnig's pearls, Soemmering's ring) which necessitates a second intervention. The majority of these secondary cataracts are due to mitotic activity in the zona germinativa of the lens capsule. Since this germinative zone is situated just in front of the lens equator, it can be removed by making a large anterior capsulectomy (prevention of secondary cataract). This will not interfere with Lobster Claw Lens implantation, since fixation is independent of a 'capsular bag'.
ij ~
ff(~
.=::::::::;;;::;~ __- :A
INCISION
An irrigating knife is suitable for making a full depth corneoscleral incision (Figs 6, 7). It is recommended that an incision of sufficient width is made (Barra-
Fig.6B The cutting angle can be bent into any required position
c d Fig. 6A Irrigating knife. a, 10 cc syringe; b, millipore filter; c, silicone tube; d, handle; e, irrigating knife
quer: 'small incisions, big trouble; large incisions, little trouble'). When the knifetip enters the anterior chamber, chamber depth can be maintained by BSS injected through the irrigating knife. Haemorrhages are removed by irrigation and will therefore not disturb the surgeon's view. This approach makes the use of cauterization almost always superfluous. The avoidance of cautery will result in faster woundhealing. PREVENTION OF SECONDARY CATARACT: CAPSULECTOMY
There are several methods of performing an extensive capsulectomy: (lA) Multiple puncture holes are made with the microneedle forceps (de Vries: Fig. 8) and connected with each other. The lens capsule is grasped with the
Fig.7
A full-depth corneoscleral incision is made
Fig. 8 De Vries microneedle forceps. a, in closed position; b, digital pressure on the rear end opens the grasping part, which will close automatically on releasing the pressure
forceps and removed from the lens surface (closed chamber technique: Figs 9, 10). (lB) The same technique can be performed after a full-depth corneoscleral incision has been made. Anterior chamber depth can be maintained with viscoelastic materials. cur J Implant Ref Surg, Vol 3, June 1991
161
Some Aspects of Implant Surgery
serve the natural barrier between the anterior and the posterior compartments. This is especially important in the younger age group. Cellular components are removed by aspiration through a cannula. Recently a glass cannula was introduced for this purpose (Van AndeD, which gives an excellent view of all manoeuvres (Fig. 11). A
Fig.9 Peripheral capsulotomy (closed chamber technique)
Fig. 11 Removal of Eischnig's pearls by aspiration through a glass cannula
Fig. 10 Grasping of the perforated anterior lens capsule
(2) Horizontal capsulotomy with an (irrigated) needle with curved tip followed by capsulectomy with special capsulotomy scissors after opening the anterior chamber. (3) 'Tricotage a deux aiguilles': A 27-gauge needle is inserted into the anterior chamber at the 3 o'clock position and a second needle is introduced at the 9 o'clock position. With a knitting movement the capsule is separated from the anterior lens surface (closed chamber technique).
Soemmering's ring can be grasped by the microneedle forceps and removed from the eye. A fibrotic posterior capsule is separated carefully from the anterior vitreous membrane, grasped with the microneedle forceps at a weak point, cut loose from its attachment to the ciliary body with a small discision knife and removed from the eye (Fig. 12A-E).
EXPRESSION OF THE NUCLEUS
As mentioned before, we prefer a large comeoscleral incision which permits easy removal of the nucleus in ECCE (by expression) and of the complete lens in ICCE (by cryoextraction). A separation of cortex and nucleus prior to expression can be obtained by hydrodissection.
PLANNED POSTERIOR CAPSULECTOMY
Some surgeons are in favour of a planned posterior capsulotomy during cataract surgery in order to prevent central opacifications caused by secondary cataract formation. Since decompartmentalization consists of the creation of a pathway for biochemically active substances from the anterior to the posterior eye segment, this will mimic the situation that exists after ICCE has been performed. The same is true for the Vag-laser or surgical posterior capsulotomy to treat existing posterior capsule opacifications. Therapy should consist of a method of cleaning the posterior lens capsule which will preEur J Imp/ant Ref Surg. Val 3. June 1991
REMOVAL OF CORTICAL REMNANTS
A simple single irrigation cannula is used for this purpose (the glass cannula is also very suitable for this surgical technique). Gentle irrigation and aspiration is done by the assistant until all cortical material has been removed. Careful iris massage will bring peripheral lens fibres into view. Loss of the anterior chamber is prevented by repeated aspiration of minimal quantities of cortical remnants. An important point is to wait patiently for the natural swelling of the cortex fibres which then can be
162
J.G.F. Worst, LI. Los
Fig. 12A-E Removal of a fibrotic posterior lens capsule. A Introduction of the microneedle forceps behind a Lobster Claw Lens. This lens type leaves sufficient surgical working space for this technique. B Grasping of the fibrotic membrane. C Discision of the upper temporal quadrant with a small discision knife. D Discision of the lower temporal quadrant. E Removal of the fibrotic membrane. The anterior vitreous membrane is not damaged
removed more easily from the lens capsule without rupturing it. IMPLANTATION OF THE LOBSTER CLAW LENS
After constriction of the pupil with pilocarpine chlorate (avoid the pilocarpine nitrate), an Iris Claw Lens (Fig. 13A, B) is introduced into the anterior chamber
and fixated to the midperipheral portion of the iris. Fixation can be done with a fine iris enclavation forceps (Fig. 14) or by a pair of double bent 30 G needles (iris 'crochet needles': Fig. 15A, B) and is based upon enclavation of small bridges of midperipheral iris tissue (immobile part of the iris) into the clawlike haptics. An iridectomy is always made to prevent potential pupillary block glaucoma. This type of fixation does not interfere with normal iris physiology (Fig. 16). The fixation principle makes the Lobster Claw Lens independent of an intact posterior capsule or a 'capsular bag'. This lens therefore has a wide applicability and can be implanted after ICeE and ECCE; as a primary or a secondary implant. The standard type is designed for implantation in adults, but a smaller version (for children) can be made on request. Since the only condition for a stable fixation is the Eur J Implant Ref Surg. Vol 3. June 1991
Some Aspects of Implant Surgery
163
Fig. 15A A 30 G needle is bent twice to form an iris 'crochet needle'. Separate needles are required for enclavation of the left and right side
Fig. 13A, B Iris Claw (Lobster Claw) Lens. A Standard design: symmetric position of enclavation sites. B Worst-Singh modification: asymmetric position of enclavation sites. The broad upper rim prevents the lens from tilting
Fig. 15B Enclavation with an iris 'crochet needle'
Fig. 14 Enclavation of the Lobster Claw Lens. A small bridge for iris tissue is grasped by the fine iris enclavation forceps. The Lobster Claw implantation forceps, while holding the lens well onto the optic part, depresses the lens onto the enclavation forceps (avoid iris pull which risks an iridodialysis) Eur J Implant Ref Surg, Vol 3. June 1991
presence of iris tissue in two diametrically opposite positions, implantation is also possible after previous glaucoma surgery (large iridectomy). Implantation of a modified Lobster Claw Lens is possible, e.g. excentric claws or additional claws even after extensive iris loss (trauma: Fig. 17). In aniridia a special Lobster Claw Lens with oblique slots is fixated to stainless steel Strampelli sutures (Fig. 18). Because of its wide applicability and relatively simple manufacturing technique (one piece) the
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164
Fig.16
Normal iris physiology is preserved, e.g. undisturbed motility of the pupil
Fig.17
Lobster Claw implantation after perforating trauma
Lobster Claw Lens was originally designed for developing countries and since its introduction in 1978 about 40,000 lenses have been implanted in India (Daljit Singh, Amritsar) and Pakistan. In Europe about 10,000 have been implanted up to 1989 (in Holland the Iris Claw Lens is currently inserted in about 12% of IOL implantations). The Lobster Claw Lens is enjoying an increasing popularity. From this lens model a negative power Lobster Claw Lens for implantation in high myopia in phakic patients has been developed (Fig. 19). Some considerations which have resulted in this new field of application are: (1) The Lobster Claw fixation principle has proved to be safe and effective during the 11 years of its existence. (2) The developments in refractive surgery during
Fig. 18 Special Lobster Claw Lens with oblique slots. Fixation to preplaced transcameral stainless steel Strampelli type sutures
the past years indicate a need for the correction of high myopia by other means than spectacles or contact lenses (epikeratophakia, keratomileusis, radial keratotomy). (3) The concept of a negative power IOL for the correction of high myopia is not a new one. Barraquer introduced a negative power anterior chamber IOL and inserted it in about 400 phakic eyes. After initial good results this system has been completely abandoned because of the large number of late corneal dystrophies. At present, however, there is a tendency to reintroduce the negative power anterior chamber lens using chamber angle support for this same indication, which has been predicted to create another disaster in implantology (Worst, 1989). The midperipheral iris-fixation principle differs basically from chamber angle fixation and therefore Eur J Implant Ref Surg. Vol 3. June 1991
Some Aspects of Implant Surgery
V1
3 3
Fig. 19A Negative power Lobster Claw Lens for implantation in high myopia
Fig. 19B The vaulted design provides a safe distance from the patient's own lens
should not be compared with the former. The negative power Lobster Claw Lens is of a special vaulted type in order to maintain a safe distance from the patient's own lens. The implantation technique has been developed by one of the authors (J.W.); about 300 implantations have been done during the past two years by different surgeons [4, 5]. Although the initial results have been promising, we would like to make some remarks upon the desirability of the use of this technique on a larger scale. Since the experience of one author (J. W.) with this particular type of lens is of relatively short duration (starting about 2.5 years ago), implantation is done only on strict indication (high myopia: at least 10 D and otherwise uncorrectable; severe cosmetic problems) after informing the patient of the possible risks (informed consent). An anatomical prerequisite is an anterior chamber depth of at least 3.5 mm. Since most implant surgeons lack experience with the midperipheral iris claw fixation principle, we consider it absolutely necessary that training should be given in this technique before implantation of the negative power modification of the Lobster Claw Lens is considered. SUTURING
The final step in implant and cataract surgery is Eur J Implant Ref Surg. Vol 3, June 1991
165
suturing of the corneoscleral wound. We use a 50 fl.m stainless steel thread for this purpose. Stainless steel sutures and suturing techniques differ from standard procedures in several respects: (1) The stainless steel must be stretched lightly to remove 'kinks' (Fig. 20A). (2) Very short bites can and must be taken. Because there is no sloughing or tissue compression by the suture, any risk of late suture failure is excluded. The bite taken at surgery will remain the bite taken for the years to come (Fig. 20B). (3) A double throw is made around the needle holder; the left hand moves away from the surgeon and the right hand is moved in the opposite direction (cross-handed technique). This results in a small ringshaped 'staple' (Fig. 20C-E). (4) After formation of a 'staple', one suture end is broken off by pulling firmly and the other end of the suture is cut off flush with the sclera with Vannas scissors (Fig. 20F).
J.G.F. Worst, L... Los
166
D
E
--~.
-
Fl
F2
Fig. 2OA-E Stainless steel suturing technique: A Stretching of the stainless steel thread, B Short bites of corneoscleral wound edges are taken. C Adouble throw is made around the needleholder. DCross-handed technique. E Pulling the suture ends will result in the formation of a ringshaped 'staple', FOne suture end is broken ofT; the other suture end is cut ofT flush with the sclera
Incidentally, the suture hardly ever needs to be taken out. This is only necessary when one has failed to perform a proper short cutting technique and some end of the metal is sticking up. The steel 'staple' provides firm wound closure, which makes it very suitable for outpatient surgery. The costs of this suture, if not swaged to a commer-
cially available needle, are negligible. It can be easily inserted into a self-made needle. Sterilization, finally , can be done in many ways, e.g. by acetone, or by autoclaving. These advantages make it a firstchoice suture especially in developing countries. Recently a WHO-funded study to evaluate its merits was started in Aravind [61. cur J Implant Ref Surg. Vol 3. June 1991
Some Aspects of Implant Surgery
ACKNOWLEDGEMENTS We would like to thank W. Velt for the diagrams. Figures 6A, 6B and 11 reprinted by permission of Slack Inc. Figures 13, 16, 19B and 20 reprinted by permission of Kluwer Academic Publishers. Note: The instruments described in this article can be obtained through Ophtec BV, Groningen, Holland.
REFERENCES C. Kupfer. Editorial. IAPB News (Newsletter of the International Agency for the Prevention of Blindness), 12, 1 (1989).
Eur J Implant Ref Surg, Vol 3, June 1991
167 2 W.S. Atkinson. In D.J. Lyle (Ed.), Anesthesia in Ophthalmology. Illinois, USA, C.C. Thomas, 1955. 3 J.G.F. Worst. Biotoxizitiit des Kammerwassers, eine vereinheitlichende pathologische Theorie, begriindet auf hypothetische biotoxische Kammerwasserfaktoren. Klin. Mbl. Augenheilk., 167,376-384 (1975). 4 P.U. Fechner, G.L. van der Heyde, J.G.F. Worst. Intraokulare Linse zur Myopiekorrektion des phaken Auges. Klin. Mbl. Augenheilk., 193,29-34 (1988). 5 P.U. Fechner,G.L. vander Heyde,J.G.F. Worst. The correction of myopia by lens implantation into phakic eyes. Am. J. Ophthalmol., 107,659-663 (1989). 6 R.D. Thulasiraj. Operations research to reduce the backlog of cataract blind. IAPB News, 12,5 (1989).
Some Aspects of Implant Surgery J.G.F. WORST and l.1. LOS Department of Ophthalmology, Refaja Hospital, Stadskanaal, Holland and Jan Worst Research Group, Haren, Holland
In the rapidly developing field of cataract and refractive surgery many techniques and lens designs are introduced and propagated. As it is not always easy to decide which line to follow, some of the author's (J.W.) basic principles will be presented here, mainly regarding cataract surgery. Furthermore the intraocular lens of his first choice in almost all cataract extractions-the Lobster Claw Lens-will be described, plus a modification thereof for implantation in high myopia. Keywords: ICCE; ECCE; Cataract backlog; Lobster Claw Lens; Secondary cataract; High myopia; Stainless steel sutures
INTRODUCTION
Implant and refractive surgery techniques are rapidly developing nowadays. New techniques are continuously introduced and new lens designs proposed and propagated. Since it is not always easy for the individual surgeon to decide which line to follow, some basic principles will be indicated here and will be illustrated with some instruments and techniques. Finally a short description of the Lobster Claw Lens will be presented and a special modification given for implantation in high myopia. An important basic principle is to obtain experience with simple, safe and effective techniques. By this means implant surgery will be prevented from becoming 'high tech'; an expensive field which limits such techniques to the economically privileged. The undesirability of this will be evident by considering the enormous cataract backlog currently present and increasing, mainly in developing countries fl1. SURGICAL TECHNIQUE AND INSTRUMENTS
1. Anaesthesia. General anaesthesia is given on special indication only. If general anaesthesia is administered, care must be taken to avoid venous congestion. A logistic important advantage of local anaesthesia is that it can be deli vered by paramedics, requires fewer instruments and is applicable in outpatient surgery. Local anaesthesia consists of a retroPlease address all correspondence to: Jan Worst Research Group, Julianalaan 11,9751 BM Haren, The Netherlands. 0955-3681/91/020157+ 11 $03.0010 © 1991 Bailliere Tindall
bulbar injection (Fig. lA-D) ofxylocaine. Hyaluronidase and adrenaline are routinely added to this anaesthetic [2]; the latter is omitted if cardiovascular contra indications exist. Additional parabulbar injections with the same mixture are given. Superior rectus anaesthesia (Fig. 2) is given in order to prevent external pressure on the eye. An optimal anaesthetic and akinetic effect is obtained by giving ocular compression and massage for at least 10 min until pressure has dropped below 10mmHg. Low vitreous pressure will decrease the incidence of complications during cataract surgery. Total immobility of the eye and eyelids indicates a correctly applied anaesthesia; ocular pressure can be measured preoperatively by the applanation of a sterile 2 cc syringe filled with water (Fig. 3). PREPARATION OF THE OPERATING FIELD
An important technique in preventing contamination of the operating field is the use of an airflow system. In addition to this the skin and eyelashes of the patient are completely covered by steridrape in such a way that no fluid-filled pockets will form between the drape and the patient's skin (Fig. 4). An adhesive malleable disposable lidholder can be used to prevent external pressure on the eye (Fig. 5). CATARACT EXTRACTION (ICCE AND ECCE)
There is at present a strong tendency to perform ECCE, since this method will preserve the posterior Eur J Implant Ref Surg, Vol 3, June 1991
J.G.F. Worst, LI. Los
158
Fig. Ie Correct position of the needle with the curved tip for retrobulbar injection-lateral view
Fig. lA Retrobulbar injection of local anaesthetic into the lower temporal area. The patient looks in the upper nasal direction. A sharp 24 G needle with a curved tip is used
Fig. ID As Fig. IC, but front view
Fig. 18 The 24 G injection needle is curved 45° at about 5 mm
distance from the tip
lens capsule, thus presenting a possibility for posterior chamber lens fixation. Furthermore the intact posterior lens capsule (and more importantly, an intact anterior vitreous membrane) will form a biological 'watershed' between the anterior and the pos-
terior eye segment, thus maintaining an anatomical and physiological integrity of the various compartments. Vitreous loss will be prevented in most cases. Generally speaking this is the correct approach which by respecting the normal anatomical situation will avoid posterior segment pathology. The natural barrier between anterior and posterior eye segment should be carefully respected, especially in young people, since 'decompartmentalization' in this age Eur J Implant Ref Surg, Vol 3, June 1991
Some Aspects of Implant Surgery
159
Fig.4 Preparation of the operative field: skin and eyelashes are covered by steridrape
\....... ,-r,.
Fig.2 Parabulbar injection through the superior eyelid (superior rectus anaesthesia ). Anaesthetic is injected while retracting the needle
::" :';
.
·····.i:...:...··
Fig. 5
Fig.3 A waterfilled 2cc syringe is applied to the anaesthetized cornea to measure preoperative lOP by applanation. lOP is read as follows: Applanation (number of divisions) 2 3 3.5 4
Schiiitz (mmHg) c. 30 c. 25
c. 20 c.15
5 lines or more indicates a safe preoperative pressure
group will lead to unfavourable results [31. This is associated with the following pathological conditions: 1. Cystoid macular oedema. 2. Aphakic retinal detachment. 3. Vitritis. 4. The irritable eye. In eyes with mature cataracts, however, the anatomical situation is essentially different and ICCE is Eur J Implant Ref Surg, Vol 3, June 1991
.
:.: . :.:
Disposable Iidholder
possible without disturbing normal physiological conditions (i.e. integrity of the anterior vitreous membrane). This is evident in people over 75 years of age, who generally have anterior and posterior vitreous detachments due to involution of the vitreous body. Another prerequisite is the presence of a weak zonule. In heavily pigmented eyes the anatomical condition of the posterior segment seems to prevent cystoid macular oedema (CMO) after ICCE, even in younger eyes (about 40 years) with mature cataracts [M. Hogeweg, N. Christy, P. Lall, personal communications]. Therefore, we hypothesize an anatomical or physiological difference between blue and brown eyes. If performed under proper conditions, ICCE by cryoextraction still has an important place in cataract surgery, all the more so because of its evident advantages. This method is relatively cheap, easy to perform, quick and will not present the one major problem of ECCE-the formation of a second.~ ary cataract. Intracapsular cataract extraction cannot be performed on very young patients and it is also a disadvantage of ICCE that it is not possible to implant a
160
J.G.F. Worst, L.I. Los
posterior chamber lens. A good alternative is the implantation of an Iris Claw/Lobster Claw Lens. Because the Lobster Claw Lens is fixated to the midperipheral iris, implantation can be performed after ICCE as well as ECCE. The major problem which occurs after ECCE is the formation of a secondary cataract (Fibrosis, Elschnig's pearls, Soemmering's ring) which necessitates a second intervention. The majority of these secondary cataracts are due to mitotic activity in the zona germinativa of the lens capsule. Since this germinative zone is situated just in front of the lens equator, it can be removed by making a large anterior capsulectomy (prevention of secondary cataract). This will not interfere with Lobster Claw Lens implantation, since fixation is independent of a 'capsular bag'.
ij ~
ff(~
.=::::::::;;;::;~ __- :A
INCISION
An irrigating knife is suitable for making a full depth corneoscleral incision (Figs 6, 7). It is recommended that an incision of sufficient width is made (Barra-
Fig.6B The cutting angle can be bent into any required position
c d Fig. 6A Irrigating knife. a, 10 cc syringe; b, millipore filter; c, silicone tube; d, handle; e, irrigating knife
quer: 'small incisions, big trouble; large incisions, little trouble'). When the knifetip enters the anterior chamber, chamber depth can be maintained by BSS injected through the irrigating knife. Haemorrhages are removed by irrigation and will therefore not disturb the surgeon's view. This approach makes the use of cauterization almost always superfluous. The avoidance of cautery will result in faster woundhealing. PREVENTION OF SECONDARY CATARACT: CAPSULECTOMY
There are several methods of performing an extensive capsulectomy: (lA) Multiple puncture holes are made with the microneedle forceps (de Vries: Fig. 8) and connected with each other. The lens capsule is grasped with the
Fig.7
A full-depth corneoscleral incision is made
Fig. 8 De Vries microneedle forceps. a, in closed position; b, digital pressure on the rear end opens the grasping part, which will close automatically on releasing the pressure
forceps and removed from the lens surface (closed chamber technique: Figs 9, 10). (lB) The same technique can be performed after a full-depth corneoscleral incision has been made. Anterior chamber depth can be maintained with viscoelastic materials. cur J Implant Ref Surg, Vol 3, June 1991
161
Some Aspects of Implant Surgery
serve the natural barrier between the anterior and the posterior compartments. This is especially important in the younger age group. Cellular components are removed by aspiration through a cannula. Recently a glass cannula was introduced for this purpose (Van AndeD, which gives an excellent view of all manoeuvres (Fig. 11). A
Fig.9 Peripheral capsulotomy (closed chamber technique)
Fig. 11 Removal of Eischnig's pearls by aspiration through a glass cannula
Fig. 10 Grasping of the perforated anterior lens capsule
(2) Horizontal capsulotomy with an (irrigated) needle with curved tip followed by capsulectomy with special capsulotomy scissors after opening the anterior chamber. (3) 'Tricotage a deux aiguilles': A 27-gauge needle is inserted into the anterior chamber at the 3 o'clock position and a second needle is introduced at the 9 o'clock position. With a knitting movement the capsule is separated from the anterior lens surface (closed chamber technique).
Soemmering's ring can be grasped by the microneedle forceps and removed from the eye. A fibrotic posterior capsule is separated carefully from the anterior vitreous membrane, grasped with the microneedle forceps at a weak point, cut loose from its attachment to the ciliary body with a small discision knife and removed from the eye (Fig. 12A-E).
EXPRESSION OF THE NUCLEUS
As mentioned before, we prefer a large comeoscleral incision which permits easy removal of the nucleus in ECCE (by expression) and of the complete lens in ICCE (by cryoextraction). A separation of cortex and nucleus prior to expression can be obtained by hydrodissection.
PLANNED POSTERIOR CAPSULECTOMY
Some surgeons are in favour of a planned posterior capsulotomy during cataract surgery in order to prevent central opacifications caused by secondary cataract formation. Since decompartmentalization consists of the creation of a pathway for biochemically active substances from the anterior to the posterior eye segment, this will mimic the situation that exists after ICCE has been performed. The same is true for the Vag-laser or surgical posterior capsulotomy to treat existing posterior capsule opacifications. Therapy should consist of a method of cleaning the posterior lens capsule which will preEur J Imp/ant Ref Surg. Val 3. June 1991
REMOVAL OF CORTICAL REMNANTS
A simple single irrigation cannula is used for this purpose (the glass cannula is also very suitable for this surgical technique). Gentle irrigation and aspiration is done by the assistant until all cortical material has been removed. Careful iris massage will bring peripheral lens fibres into view. Loss of the anterior chamber is prevented by repeated aspiration of minimal quantities of cortical remnants. An important point is to wait patiently for the natural swelling of the cortex fibres which then can be
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Fig. 12A-E Removal of a fibrotic posterior lens capsule. A Introduction of the microneedle forceps behind a Lobster Claw Lens. This lens type leaves sufficient surgical working space for this technique. B Grasping of the fibrotic membrane. C Discision of the upper temporal quadrant with a small discision knife. D Discision of the lower temporal quadrant. E Removal of the fibrotic membrane. The anterior vitreous membrane is not damaged
removed more easily from the lens capsule without rupturing it. IMPLANTATION OF THE LOBSTER CLAW LENS
After constriction of the pupil with pilocarpine chlorate (avoid the pilocarpine nitrate), an Iris Claw Lens (Fig. 13A, B) is introduced into the anterior chamber
and fixated to the midperipheral portion of the iris. Fixation can be done with a fine iris enclavation forceps (Fig. 14) or by a pair of double bent 30 G needles (iris 'crochet needles': Fig. 15A, B) and is based upon enclavation of small bridges of midperipheral iris tissue (immobile part of the iris) into the clawlike haptics. An iridectomy is always made to prevent potential pupillary block glaucoma. This type of fixation does not interfere with normal iris physiology (Fig. 16). The fixation principle makes the Lobster Claw Lens independent of an intact posterior capsule or a 'capsular bag'. This lens therefore has a wide applicability and can be implanted after ICeE and ECCE; as a primary or a secondary implant. The standard type is designed for implantation in adults, but a smaller version (for children) can be made on request. Since the only condition for a stable fixation is the Eur J Implant Ref Surg. Vol 3. June 1991
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Fig. 15A A 30 G needle is bent twice to form an iris 'crochet needle'. Separate needles are required for enclavation of the left and right side
Fig. 13A, B Iris Claw (Lobster Claw) Lens. A Standard design: symmetric position of enclavation sites. B Worst-Singh modification: asymmetric position of enclavation sites. The broad upper rim prevents the lens from tilting
Fig. 15B Enclavation with an iris 'crochet needle'
Fig. 14 Enclavation of the Lobster Claw Lens. A small bridge for iris tissue is grasped by the fine iris enclavation forceps. The Lobster Claw implantation forceps, while holding the lens well onto the optic part, depresses the lens onto the enclavation forceps (avoid iris pull which risks an iridodialysis) Eur J Implant Ref Surg, Vol 3. June 1991
presence of iris tissue in two diametrically opposite positions, implantation is also possible after previous glaucoma surgery (large iridectomy). Implantation of a modified Lobster Claw Lens is possible, e.g. excentric claws or additional claws even after extensive iris loss (trauma: Fig. 17). In aniridia a special Lobster Claw Lens with oblique slots is fixated to stainless steel Strampelli sutures (Fig. 18). Because of its wide applicability and relatively simple manufacturing technique (one piece) the
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Fig.16
Normal iris physiology is preserved, e.g. undisturbed motility of the pupil
Fig.17
Lobster Claw implantation after perforating trauma
Lobster Claw Lens was originally designed for developing countries and since its introduction in 1978 about 40,000 lenses have been implanted in India (Daljit Singh, Amritsar) and Pakistan. In Europe about 10,000 have been implanted up to 1989 (in Holland the Iris Claw Lens is currently inserted in about 12% of IOL implantations). The Lobster Claw Lens is enjoying an increasing popularity. From this lens model a negative power Lobster Claw Lens for implantation in high myopia in phakic patients has been developed (Fig. 19). Some considerations which have resulted in this new field of application are: (1) The Lobster Claw fixation principle has proved to be safe and effective during the 11 years of its existence. (2) The developments in refractive surgery during
Fig. 18 Special Lobster Claw Lens with oblique slots. Fixation to preplaced transcameral stainless steel Strampelli type sutures
the past years indicate a need for the correction of high myopia by other means than spectacles or contact lenses (epikeratophakia, keratomileusis, radial keratotomy). (3) The concept of a negative power IOL for the correction of high myopia is not a new one. Barraquer introduced a negative power anterior chamber IOL and inserted it in about 400 phakic eyes. After initial good results this system has been completely abandoned because of the large number of late corneal dystrophies. At present, however, there is a tendency to reintroduce the negative power anterior chamber lens using chamber angle support for this same indication, which has been predicted to create another disaster in implantology (Worst, 1989). The midperipheral iris-fixation principle differs basically from chamber angle fixation and therefore Eur J Implant Ref Surg. Vol 3. June 1991
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V1
3 3
Fig. 19A Negative power Lobster Claw Lens for implantation in high myopia
Fig. 19B The vaulted design provides a safe distance from the patient's own lens
should not be compared with the former. The negative power Lobster Claw Lens is of a special vaulted type in order to maintain a safe distance from the patient's own lens. The implantation technique has been developed by one of the authors (J.W.); about 300 implantations have been done during the past two years by different surgeons [4, 5]. Although the initial results have been promising, we would like to make some remarks upon the desirability of the use of this technique on a larger scale. Since the experience of one author (J. W.) with this particular type of lens is of relatively short duration (starting about 2.5 years ago), implantation is done only on strict indication (high myopia: at least 10 D and otherwise uncorrectable; severe cosmetic problems) after informing the patient of the possible risks (informed consent). An anatomical prerequisite is an anterior chamber depth of at least 3.5 mm. Since most implant surgeons lack experience with the midperipheral iris claw fixation principle, we consider it absolutely necessary that training should be given in this technique before implantation of the negative power modification of the Lobster Claw Lens is considered. SUTURING
The final step in implant and cataract surgery is Eur J Implant Ref Surg. Vol 3, June 1991
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suturing of the corneoscleral wound. We use a 50 fl.m stainless steel thread for this purpose. Stainless steel sutures and suturing techniques differ from standard procedures in several respects: (1) The stainless steel must be stretched lightly to remove 'kinks' (Fig. 20A). (2) Very short bites can and must be taken. Because there is no sloughing or tissue compression by the suture, any risk of late suture failure is excluded. The bite taken at surgery will remain the bite taken for the years to come (Fig. 20B). (3) A double throw is made around the needle holder; the left hand moves away from the surgeon and the right hand is moved in the opposite direction (cross-handed technique). This results in a small ringshaped 'staple' (Fig. 20C-E). (4) After formation of a 'staple', one suture end is broken off by pulling firmly and the other end of the suture is cut off flush with the sclera with Vannas scissors (Fig. 20F).
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D
E
--~.
-
Fl
F2
Fig. 2OA-E Stainless steel suturing technique: A Stretching of the stainless steel thread, B Short bites of corneoscleral wound edges are taken. C Adouble throw is made around the needleholder. DCross-handed technique. E Pulling the suture ends will result in the formation of a ringshaped 'staple', FOne suture end is broken ofT; the other suture end is cut ofT flush with the sclera
Incidentally, the suture hardly ever needs to be taken out. This is only necessary when one has failed to perform a proper short cutting technique and some end of the metal is sticking up. The steel 'staple' provides firm wound closure, which makes it very suitable for outpatient surgery. The costs of this suture, if not swaged to a commer-
cially available needle, are negligible. It can be easily inserted into a self-made needle. Sterilization, finally , can be done in many ways, e.g. by acetone, or by autoclaving. These advantages make it a firstchoice suture especially in developing countries. Recently a WHO-funded study to evaluate its merits was started in Aravind [61. cur J Implant Ref Surg. Vol 3. June 1991
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ACKNOWLEDGEMENTS We would like to thank W. Velt for the diagrams. Figures 6A, 6B and 11 reprinted by permission of Slack Inc. Figures 13, 16, 19B and 20 reprinted by permission of Kluwer Academic Publishers. Note: The instruments described in this article can be obtained through Ophtec BV, Groningen, Holland.
REFERENCES C. Kupfer. Editorial. IAPB News (Newsletter of the International Agency for the Prevention of Blindness), 12, 1 (1989).
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167 2 W.S. Atkinson. In D.J. Lyle (Ed.), Anesthesia in Ophthalmology. Illinois, USA, C.C. Thomas, 1955. 3 J.G.F. Worst. Biotoxizitiit des Kammerwassers, eine vereinheitlichende pathologische Theorie, begriindet auf hypothetische biotoxische Kammerwasserfaktoren. Klin. Mbl. Augenheilk., 167,376-384 (1975). 4 P.U. Fechner, G.L. van der Heyde, J.G.F. Worst. Intraokulare Linse zur Myopiekorrektion des phaken Auges. Klin. Mbl. Augenheilk., 193,29-34 (1988). 5 P.U. Fechner,G.L. vander Heyde,J.G.F. Worst. The correction of myopia by lens implantation into phakic eyes. Am. J. Ophthalmol., 107,659-663 (1989). 6 R.D. Thulasiraj. Operations research to reduce the backlog of cataract blind. IAPB News, 12,5 (1989).