|Year : 1993 | Volume
| Issue : 4 | Page : 195-210
Extracapsular cataract extraction : Surgical techniques
Surendra Basti, Abhay R Vasavada, Ravi Thomas, Prema Padhmanabhan
|How to cite this article:|
Basti S, Vasavada AR, Thomas R, Padhmanabhan P. Extracapsular cataract extraction : Surgical techniques. Indian J Ophthalmol 1993;41:195-210
|How to cite this URL:|
Basti S, Vasavada AR, Thomas R, Padhmanabhan P. Extracapsular cataract extraction : Surgical techniques. Indian J Ophthalmol [serial online] 1993 [cited 2014 Jul 31];41:195-210. Available from: http://www.ijo.in/text.asp?1993/41/4/195/25591
| 1. Introduction|| |
Gullapalli N. Rao, M.D.
Quality of vision and early rehabilitation are two of the critical parameters that determine the success of modem cataract surgery. Advances in pathophysiology, surgical techniques, instrumentation, and pharmacologic agents have contributed to a revolution in this field making cataract surgery almost risk-free. Newer designs of intraocular lenses implanted into the eye by skilled ophthalmologists have added an unparalleled dimension to the saga of cataract surgery.
Cataract surgery continues to be evolutionary. While extracapsular cataract surgery with high degree of safety is practiced around the world, we in India are still in the process of "conversion." Evidently, in 1992 only 40% of all cataract cases were treated employing extracapsular cataract extraction. This long latency could partly be attributed to lack of adequate exposure to these techniques for many an ophthalmologist.
The following four articles describe the essential steps of extracapsular cataract extraction and diversity in methodology. The authors have attempted to provide an overview of the options available and the individual practitioner is encouraged to evolve his own recipe for successful cataract surgery through extracapsular cataract extraction.
| 2. The Wound and Closure|| |
Surendra Basti, D.N.B.
From L.V. Prasad Eye Institute, Hyderabad.
'As the section goes, so goes the operation' - this dictum initially framed when the Von Graefe section was in vogue, is largely true even in this era of smallincision cataract surgery.
In this article, wound construction and closure are discussed as they relate to the two most popular surgical procedures practised today, namely:
I. Planned Extracapsular Cataract Extraction (pECCE)
II. Kelman Phacoemulsification (KPE)
WOUND CONSTRUCTION FOR PLANNED EXTRACAPSULAR CATARACT EXTRACTION
Location of the wound
The wound may be constructed at the limbus, within the cornea, or at the sclera. The influence of incisions at each of these sites, on the surgical procedure are summarized in [Table - 1]. Clinical situations where corneal and scleral incisions are preferred are listed in [Table - 2].
Length of the wound
The length of the incision may vary between 8 and 12 mm, depending upon the size and density of the nucleus. The chord length needs to be increased as the incision is shifted away from the cornea and vice versa.
CONFIGURATION OF THE WOUND
The external configuration of the incision is usually curvilinear but may be oriented straight when a small (for example, 8 mm) incision is being made [Figure - 1].
Internal Configuration [Figure - 2]A and B
The wound can have the following varieties of internal configurations:
iii. Combined (Beveled and Perpendicular) iv. Three Plane
Salient features of each of these is mentioned in [Table - 3].
CLOSURE OF THE pECCE WOUND
Suture patterns may be divided into:
Salient features of each of these are mentioned in [Table - 4]. The various patterns of continuous suture application are illustrated in [Figure - 3]. Sutures may either be preplaced or postplaced. Preplaced sutures by definition, are those that are placed prior to making the section. The advantage of these are that they appose corresponding points together and hence prevent lateral displacement or override of the wound edges which can cause astigmatism. The advent of microsurgery has greatly facilitated suturing by providing excellent visualization and high magnification. This has largely obviated the need for preplaced sutures.
THE MECHANICS OF SUTURING
Suture Length [Figure - 4]
Sutures produce a zone of compression that equals the length of the suture. Hence, long sutures placed close to each other create significant tissue compression leading to with the rule astigmatism. Widely separated sutures, on the other hand, permit wound slippage and hence cause against the rule astigmatism. Sutures that are separated by a distance that equals their length cause minimal astigmatic change. Sutures 1.5 mm long are optimal for cataract surgery, with the length of the bites being equal on each side of the section.
Loose sutures permit wound edge separation and this leads to against the rule astigmatism. Optimal tightening of sutures apposes wound edges with minimal distortion of adjoining tissue.
Sutures that are too superficial tend to cut through and permit wound edge slippage leading to against the rule astigmatism. Fine sutures, for example, 10-0 nylon, are ideally placed at 90% depth. Sutures that are less fine, for example, 8 - 0 silk, are placed at half-thickness depth. Thick sutures if placed deep can erode through due to necrosis of underlying tissue. The two lips of the wound should have the suture at the same depth for optimal apposition.
Absorbable sutures cause premature or variable relaxation of the wound. They are hence not suitable for closure in cataract surgery. Of the nonabsorbable materials, silk often produces an inflammatory focus; this can cause tissue melting which induces wound relaxation. Nylon, mersilene, polypropylene, or steel wire sutures maintain the zones of compression throughout the wound healing phase and hence, are better materials for wound closure. Late (beyond 1 year) against the rule shift due to suture degradation tends to occur most with nylon and is least with mersilene and steel wire sutures.
Sutures should always be oriented radially. Nonradial sutures cause lateral displacement of the lips and hence lead on to astigmatism.
II. WOUND CONSTRUCTION FOR KELMAN PHACOEMULSIFICATION
Phacoemulsification procedures call for the construction of small (2.8 to 3.2 mm) wounds. The various types of wounds that may be used for KPE are mentioned in [Figure - 5].
SALIENT FEATURES OF THE SCLERAL POCKET - CORNEAL FLAP KPE WOUND
Location of the wound
This is determined by the width of the incision called for - a parameter determined by the type of IOL to be used. As a rule, the depth of the scleral pocket should equal its circumferential extent. Also, the amount of clear corneal dissection should be approximately 1 mm. [Figure - 6] illustrates this point.
An easy way to determine the site of commencement of the scleral incision is as follows:
Site of incision (From Posterior extent of limbal grey zone) = Planned horizontal width - 2
For example for a 3 mm foldable silicone IOL, the site would be equal to 3 - 2 - 1 mm posterior to the limbal grey zone. Similarly, for a 6 mm IOL it would be 6 -2 -4 mm posterior to limbal grey zone.
Length of the wound
This varies between 3 and 6 mm depending upon the type of IOL available for insertion. When compared to short incisions, long incisions tend to show more early postoperative with-the-rule astigmatism with greater against-the-rule shift subsequently.
CONFIGURATION OF THE WOUND
Internal configuration [Figure - 7].
The scleral pocket-corneal flap wound has an internal corneal flap that is self-sealing in the face of anterior chamber pressure forces and a long scleral tunnel that absorbs external forces and thus avoids wound separation.
The external configuration of the scleral pocket incision may either be straight or curved as shown in [Figure - 8]. Studies by Koch have demonstrated that the astigmatism-neutral zone has a configuration as showed in [Figure - 9]. The 'Frown' configuration is hence best suited for small-incision cataract surgery. The tendency for wound edge separation is also comparatively less for this configuration. Cataracts in children above the age of 10 years and in young adults have soft, small nuclei which lend themselves well to the use of the scleral pocket-corneal flap wound even in the absence of the KPE system (sutureless surgery for the 'phacoless' surgeon !!).
Closure of the KPE wound
Wounds that have an internal corneal lip are selfsealing and are closed by the intraocular pressure. The techniques suitable for closure of KPE wounds without the internal corneal lip are indicated in [Figure - 10].
KPE wounds without the internal corneal flap but with a scleral tunnel may be closed by the horizontal suture technique [Figure - 11], since the scleral pocket itself forms a barrier (although incomplete) to the external compression forces that distort the wound edges and thus cause aqueous to leak out of the anterior chamber. Apposition of the wound surfaces as is achieved with horizontal sutures ensures a watertight wound. The advantage of the horizontal sutures is that they cause much less early postoperative with-the-rule astigmatism, as compared to radial sutures.
REFRACTIVE CONSIDERATIONS DURING CATARACT SURGERY
Cataract surgery, from being a procedure that restores vision lost due to the lenticular opacity is now changing into a procedure that aims for postoperative emmetropia. The cataract incision may be looked upon as a refractive procedure in itself, capable of:
1. permanently reducing the astigmatic component (upto 2.5D) of the preoperative refractive error, and
2. maintaining sphericity in patients without pre operative astigmatism.
THE CYLINDER REGRESSION PROFILE
As the cataract wound heals, the meridian along which the wound is centred tends to progressively flatten. Since most often, the wound in cataract surgery is centred along the 12 o'clock meridian, there is a progressive against-the-rule shift that occurs in the with-the-rule astigmatism that is always seen early, postoperatively. The size and architecture of the incision are important determinants of the final against the rule shift.
Smaller the size of the wound, lesser the amount of cylinder regression. The 3 mm incision, for example is too small to alter the corneal shape appreciably. Such an incision essentially maintains the preoperative cylinder profile to a large extent. Larger incisions however, cause correspondingly more cylinder regression.
Features of the incision architecture that affect the cylinder regression are the location, depth and length, type, density and tension of suture material, the depth and length of the suture bites and postoperative steroid dosage.
Since there are numerous possible combinations of these parameters, no two surgeons can make the same incision. Each surgeon hence has to determine for himself, his cylinder regression profile. On an average, for 12 mm pECCE wounds 2.5 to 3D of ATR shift occurs over a 12-month period.
Broad guidelines that help the cataract surgeon achieve his refractive goal of emmetropia are as follows:
Centre the incision along the steep meridian.
Longer incisions will produce more flattening.
Posterior incisions reduce ATR wound drift.
Straight or frown incisions reduce ATR drift.
Scleral tunnel incisions minimize suture-induced astigmatism and provide a greater wound healing surface. They are hence more stable from the refractive standpoint.
For example, in a patient with pre-existing WTR astigmatism, the following alterations can be made.
1. The incision is moved more posteriorly.
2. The superficial lip of the wound is made one - half to one - fourth depth.
3. A fine suture such as 10 - 0 nylon is used.
4. The bites are made shorter (0.5 mm from wound edges).
5. Fewer suture passes are made and the sutures are not tightened significantly.
| 3. Techniques For Anterior Capsulotomy|| |
Abhay R. Vasavada, M.S., F.R.C.S
From Raghudeep Eye Clinic, Ahmedabad.
Cataract continues to be the major cause of blindness all over the world and surgery remains the only effective treatment. While cataract surgery is of different types, extracapsular cataract extraction has become the most popular technique over the last two decades. In India, most ophthalmologists are in the stage of transition from intracapsular technique to extracapsular cataract surgery.
Extracapsular cataract surgery involves three important steps namely
(1) anterior capsulotomy,
(2) nucleus management, and
(3) removal of cortex.
Anterior capsulotomy is a very vital step for successful extracapsular cataract surgery. There are three main types of anterior capsulotomy in vogue, namely [Figure - 12]:
A) Multipuncture (can-opener) Capsulotomy
B) Envelope (Intercapsular) Capsulotomy
C) Continuous Curvilinear Capsulotomy (Capsulorhexis).
A. MULTIPUNCTURE (CAN-OPENER)
This style of anterior capsulotomy has derived its name from the circular nibbling opening of the capsule through the use of a cystotome. There have been many modifications and variations in the technique. The classical can-opener capsulotomy creates a ragged but approximately circular opening. Multipuncture 'postal stamp' capsulotomy involves multiple punctures made in a circular fashion [Figure - 13]A & B.
A circular opening of approximately 5 to 6 mm in diameter may be created with the cystotome created by bending a 26-gauge or finer needle, or from innumerable other customised styles. The entire procedure may be performed in a closed chamber with the cystotome entering unopened anterior chamber, completely open or semiclosed chamber. I prefer about 2 mm opening between 11 to 12 o'clock. Irrigating cystotome, air bubble, or viscoelastic material may be used to maintain anterior chamber. I prefer a viscoelastic material.
This style of capsulotomy is easy to learn and is therefore practiced widely.
This can be performed on all types of cataracts including intumescent and hypermature cataracts.
Radial Anterior Capsular Tears
'This is almost universal. In a small study performed in 50 consecutive eyes, anterior capsular tears were noted in 98% of the eyes. These tears, in the majority, do not extend beyond the equator as the zonular attachment prevents the extension of these tears. However, these tears make a capsular bag unstable. The fixation of the IOL within the bag, hence becomes uncertain. Haptic or optic, or both can come out of the tear and produce asymmetrical fixation. In a significant number of eyes, true in-the-bag fixation is not achieved. The asymmetrical fixation of the IOL would also have an unfavourable effect on its centration and posterior capsular opacification. In addition, sometimes, small anterior capsular tags and flaps go unnoticed during cortical removal and inadvertently if they are aspirated or pulled, posterior capsule may rupture and vitreous disturbance can occur.
B. ENVELOPE (INTERCAPSULAR) CAPSULOTOMY
In 1979, Sourdilla and Baikuff in France suggested this approach. However Galand developed it to its present stage and popularised the 'Envelope Technique' [Figure - 14].
A horizontal, slightly curved linear capsulotomy is aimed at the junction of upper 1/3rd to middle. The punctures are directed slightly superiorly as the capsulotomy approaches the right hand side. This keeps the superior flap slightly more mobile and gives a better access to the superior capsular fornix for the removal of cortical matter. This is also known as antismiling capsulotomy which gives an excellent entry into the capsular bag. Therefore, placement of the implant in the bag is easier.
The presence of anterior capsule until the IOL is implanted reduces the trauma to the tissue.
The preservation of anterior capsule creates a semiclosed system within the anterior chamber and therefore, facilitates removal of cortical material.
Scraping of the anterior capsule to remove epithelial cells is also possible.
In the event of a posterior capsule rupture, anterior capsule may be utilised for an IOL support.
It produces marked asymmetry of the capsular flaps. This predisposes to decentration of an IOL. The Intraocular lens tends to decentre upwards.
Occurrence of radial anterior capsular tears are quite high. In-the-bag placement becomes uncertain because of these tears. The free floating capsular tears can get stuck to the pupillary margin and produce a distorted pupil later on. This technique was very popular in Europe and many other parts of the world for a few years. I have practiced this technique for number of years, but because of the development of a better capsulotomy technique, I no longer use this technique.
C. CONTINUOUS CURVILINEAR
This technique was deviced by Gimble and Neuhann simultaneously from different parts of the world. This technique involves controlled tearing of the anterior capsule producing a strong, smooth, and regular opening [Figure - 15]A. Although a circular opening is preferred, it could be of any shape.
The technique is performed by opening up the anterior chamber between 11 and 12 o'clock under a viscoelastic substance with a bent 26-guage needle. The first puncture is made in the centre of the cataract. The needle traverses to the left hand side and the horizontal slit is produced. The cystotome needle is placed underneath the slit and is lifted upwards towards the surgeon, so that a tear is produced and a small flap of anterior capsule is fashioned. This small anterior capsular flap is everted, so that the epithelial side faces the surgeon. The needle is placed near the junction of the flap and the peripheral anterior capsule. The needle pushes the flap along the tangent of that particular point along the imaginary circumference of the capsulorhexis opening. The flap is guided with push and pull in such a way that the correct size of the circular opening is produced. As the procedure progresses, sometimes the anterior capsule flap gets curled up and bunches up obstructing visibility. It is very important that the cystotome is placed as close to the junction of the tear as possible. The everted flap gives a better control than otherwise.
In the event of the tear extending towards the periphery, the force is applied radially towards the centre. When the capsulorhexis is at the end stage, it is important to overtake the starting point and join the circle from outside inwards.
In the event of joining it inside from centre to the periphery, it leaves behind a small triangle flap and a weak point in the system. A viscoelastic substance is very useful.
It is extremely difficult to perform this technique in intumescent, mature and hypermature cataracts, and cataracts in neonates and infants. With practice, however, it is possible to perform a small size rhexis in these difficult situations. The use of forceps is desirable in bringing the peripheral extension of the rhexis towards the centre.
However, it is important to maintain the anterior chamber with good viscoelastic substance, if forceps is being used for the technique.
If the capsulorhexis is small, and an attempt is made to deliver a large size nucleus through the small opening in a conventional manner, zonular dialysis and zonular rupture takes place. The capsulotomy opening is much stronger than the zonules and in attempting to express the nucleus out with the pressure-counter pressure technique, sometimes the entire cataract comes out intracapsularly. Therefore, reducing the size of the nucleus with hydrodissection and hydrodelineation becomes very important in this technique. Therefore, if in doubt, one relaxing incision at 12 o'clock may be placed which makes the nucleus management quite safe.
This style of anterior capsulotomy does not give anterior capsular tears as seen with other types of capsulotomies.
The integrity of the capsule bag is maintained throughout.
Hydrodissection and hydrodelineation becomes more effective.
It also helps the subsequent steps of cortical lens removal.
Procedures such as anterior capsule scraping can be carried out very effectively.
It allows endolenticular or in situ phacoemulsification. Consistent in-the-bag placement, with well maintained integrity of the bag has become possible and safe when phacoemulsification is performed after capsulorrhexis [Figure - 15]B. This technique is compatible with small-incision surgery and small size 10L. The opening is very elastic and strong. It can be stretched to 125% or more of its size and therefore, it can withstand large degree of disparity, when either a nucleus is delivered or an IOL is implanted. Like other capsulotomy techniques, it is better performed under a viscoelastic substance. It can be performed with the use of a bent cystotome or a pair of capsule-holding forceps.
Performing capsulorhexis requires some experience and skill.
As mentioned, it is extremely difficult to perform the rhexis in mature and hypermature cataracts, intumescment cataracts and cataracts in infants and small children.
Although, multipuncture (can-opener) technique is very easy and simple, it does not ensure the ultimate goal of placing all the intraocular lenses in the bag. Envelope technique was an attempt to achieve that goal, but because of the anterior capsule tears and asymmetry produced in the capsular flaps, this was not achieved consistently. The modern technique of capsulorhexis maintains the integrity of the capsular bag, facilitates the intraoperative manoeuvres, and gives better control and safety to techniques such as phacoemulsification and in-the-bag fixation of an IOL, which becomes consistent with this type of capsulotomy.
| 4. Methods of Nucleus Extraction|| |
Ravi Thomas, M.D., A. Braganza, M.S., J.K. Challa, M.D., and T. George, M.B.B.S.
From Schell Eye Hospital, Vellore.
This practice review deals with currently available techniques of nucleus management. As the technique of intracapsular cataract extraction (ICCE), is familiar to all of us, this article deals exclusively with nuclear delivery in ECCE techniques.
The methods of nuclear extraction can be classified as follows:
I. METHODS USED WITH MANUAL SMALL INCISION TECHNIQUES
As manual techniques employing small incision are bound to be of more interest to majority of our readers, we will deal with this first.
A. BLUMENTHAL TECHNIQUE
The essential feature of nucleus delivery by this technique is hydrodissection of the nucleus followed by its hydrodynamic expression.
1. Two 20-gauge incisions are made into the anterior chamber (AC).
2. An anterior chamber maintainer connected to irrigating fluid is inserted through one of the 20-gauge incisions. A continuous curvilinear capsulotomy (CCC) is performed through the second incision.
3. The nucleus is hydrodissected through the second incision and manipulated into 'the anterior chamber.
4. Depending on the size of the nucleus, a 5 to 7mm scleral tunnel incision is made superiorly. A sheets type glide is introduced under the nucleus.
5. The force of the fluid from the AC maintainer, and if necessary gentle pressure on the sclera causes the nucleus to engage the wound. The fluid pressure hydrodynamically expresses the nucleus through the scleral tunnel [Figure - 16].
AC is formed at all times.
The procedure is not viscoelastic dependent.
No instruments are required in the AC for nucleus delivery.
No sophisticated instrumentation is needed.
It can be used with all types of capsulotomies and nuclei (Blumenthal). We favour this manual small incision technique. We have, however, not deliberately tried it with any capsulotomy other than a CCC. On occasion when an imperfect CCC has extended we could still successfully complete the operation.
We have also had difficulty with manipulating large brunescent or mature nuclei through CCC's and small incisions, and favour larger incisions or a standard technique for these nuclei.
We find this technique (with only aspiration), ideal for congenital cataracts.
Failure to manipulate the nucleus into the AC can cause zonular dialysis during the manoeuvres required to do so.
Nucleus delivery cannot be considered in isolation. Each step of the technique is critical for the next.
Traumatic delivery with danger to the endothelium.
While viscoelastics are not necessary, they can be used for endothelial protection.
This technique was pioneered by Peter Kansas. The nucleus removal consists of the following steps:
1. %w H G H G 0 or can-opener capsulotomy.
2. Hydrodissection of the nucleus.
3. Nucleus is prolapsed into the AC.
4. Viscoelastic material is used to protect the endothelium and needs to be replenished as required.
5. A solid curved vectis is introduced under the nucleus.
6. A special instrument (nucleotome) is introduced above the nucleus.
At this stage the nucleus is sandwiched between the two instruments.
7. The two instruments are manoeuvred towards each other. The nucleotome gradually cleaves its way through the nucleus till it comes into contact with the vectis [Figure - 17]. This is a very gentle step: steady and constant prsssure on the nucleotome and gentle lifting pressure on the vectis are required. There is no need to attempt the step quickly.
8. Vectis is removed and nucleotome is left in place.
9. With a spatula and nucleotome the cleavage is confirmed and pieces of the nucleus separated.
10. The viscoelastic material is replenished.
11. A special nucleus forceps (9 mm jaws each with a double row of teeth) is introduced into the AC.
12. Nuclear fragments are positioned in the axis of the wound and removed. The superior lip of the wound is gently elevated at the same time. Downward pressure on the posterior lip with the nuclear forceps facilitates delivery [Figure - 18].
13. Deliberate removal of cortical debris mixed with viscoelastic material (viscoelastic sludge) with a large bore irrigation-aspiration tip is an important step.
3-4 mm incision can be used.
Relatively simple instrumentation.
The procedure is extremely viscoelastic dependent. In our hands methyl cellulose has not maintained the chamber adequately for this technique, and we have had to use Healon or Viscoat.
Difficult technique to master.
We have been unable to cleave Brunescent nuclei and have had to convert to standard ECCE.
Potential for corneal damage.
This technique was pioneered by Luther-Fry. The initial steps are similar to the phacofracture technique.
1. The superior pole of the nucleus is prolapsed into the AC. Any capsulotomy can be used, but a CCC is preferred.
2. Viscoelastic material is used to form the AC.
3. Lens loop is placed behind the nucleus and inserted half way towards 6 o'clock.
4. A spatula is placed on top of the nucleus. The nucleus is now sandwiched between these two
instruments [Figure - 19].
5. Using a two-handed technique, the nucleus is extracted.
7-8 mm incision.
The procedure is extremely viscoelastic dependent.
Potential damage to cornea.
A similar method is described by Gills. A lens loop (open vectis) alone is used to extract the nucleus. We prefer an irrigating vectis when using this technique.
D. NUCLEUS DIVISION WITH SNARE
This technique was developed by Keener.
1) The nucleus is prolapsed into the AC.
2) Viscoelastic material is used to form the AC.
3) A special nucleus divider (snare) is used. This can be made with a cannula and a 32-gauge stainlesssteel wire. The wire sticks out of the cannula end in the form of a loop which can be shortened (and hence tightened).
4) The nucleus snare is introduced into the AC; it is manipulated around the nucleus and tightened to divide it [Figure - 20].
5) The two pieces of the nucleus are separated.
6) The viscoelastic material is replenished.
7) The fragments are extracted separately with a narrow lens loop.
Simple instrumentation. The nucleus divider can be made by almost any ophthalmologist.
Easy to learn
Difficult in small pupils.
Difficult with soft nuclei and subluxated lenses.
Potential for damage to cornea (seems less than phacofracture and phacosandwich).
E. HYBRID TECHNIQUES
In the Hybrid techniques, the nucleus is initially sculpted with the phacoemulsifier. The nucleus is then prolapsed into the AC and removed by one of the small incision techniques described, for example, phacofracture or phacosandwich.
The major use of Hybrid techniques would be for those converting to phacoemulsification. The phacoemulsification techniques - sculpting, trench digging, etc., can be practiced step by step, increasing the amount of nucleus emulsified with the phaco as the surgeon gains experience before converting to the preferred manual technique. For example, initially some sculpting may be done before converting to a manual technique; with experience a trench is dug, and the nucleus rotated and a second trench dug before converting. Later, nucleofractis is attempted and one quadrant emulsified before converting, and so on till the surgeon gains confidence to emulsify the entire nucleus.
II. SMALL INCISION INTERCAPSULAR WASHOUT WITH HYDROSONIC
A new technique described by Azis Anis.
The technique is almost an evolutionary step to phaco and can surely be used in combination with it. Using a hydrodelineating hydrosonic handpiece with a special 29-gauge cannula, incremental injections of fluid are made from posterior (just in front of posterior capsule) to anterior. The needle is introduced through a small superior CCC. As the injection of balanced salt solution (BSS) proceeds, cleavage planes between nuclear lamellae produce concentric circles [Figure - 21]. The diameter of the smallest circle produced, according to Anis logically determines the hardness of the nucleus and hence the technique of nucleus extraction. According to Anis, a largest circle diameter of 5 to 6 mm (representing a grade III nucleus) is the upper extreme that can be managed by his technique of small incision intercapsular washout. A diameter of 7 mm or more requires standard ECCE or phaco after softening of the nucleus.
When BSS is hydrosonically injected into the nucleus (where the lamellae have fused together), the nucleus fractures into small pieces. The fractured pieces are washed out of the eye with a special Anis irrigatinggutter spatula introduced through a small superior CCC into the capsular bag posterior to the nuclear fragments. Gentle irrigation washes out the nucleus fragments; the epinucleus is removed with irrigation and aspiration.
Small incision (5 to 6 mm).
All procedures include "in-the-bag" technique.
A special Hydrodelineating Hydrosonic handpiece and disposable 29 gauge cannulas with a side port are required.
III. MANUAL EXPRESSION WITH
This method of nuclear extraction is probably the only one that can be used for almost all nuclei.
The nucleus is expressed either with pressure superiorly just behind the incision site, and if required, with counter pressure at or within the limbus inferiorly.
A word of caution to all those who are/were used to the Modified Smith Indian technique. In the Modified Smith Indian technique, the pressure is applied at the limbus superiorly, sealing the wound, as well as inferior to the limbus inferiorly leading to tumbling of the inferior pole. A deliberate attempt must be made to change this to what is described if problems are to be avoided.
The techniques vary. Some surgeons prefer just superior pressure. This works especially well if a good hydrodissection has been performed.
Alternatively, the superior pole of the nucleus is tipped up, an irrigating vectis is introduced behind, and the nucleus extracted by irrigation with almost simultaneous removal of the vectis.
The only technique which is almost universally applicable for all nuclei.
No extra instrumentation required.
Potential for damage to the cornea, theoretically decreased with a linear capsulotomy (envelope) technique.
Larger incision size as compared to other manual techniques.
We will not discuss phacoemulsification in detail. Anterior and iris plane phacoemulsification (as deliberate procedures) have been almost universally discarded. There are some who still do a posterior chamber phacoemulsification without attempting to remain in the bag.
The technique that we use is the Shephard modification of the nucleofractis technique described by Gimbel. In this technique, 4 quadrants are created in the nucleus by "trench digging" with the phacoemulsification probe and rotation of the nucleus. The objective is to fracture and isolate the quadrants following which they are individually emulsified, preferably in the bag. This technique is usually considered CCC dependent.
For softer nuclei, Koch suggests a SPRING technique which seems logical and useful. A single linear trench is dug requiring only 180° of rotation of the nucleus: relaxing nucleotomies are made, the nuclear plate is shaved. PAAR (peripheral aspiration and removal) performed and the resultant halves of the nuclei emulsified.
SELECTION OF TECHNIQUE FOR INDIVIDUAL CASES
The guidelines for nucleus extraction in an individual case is as follows:
1. CONGENITAL AND JUVENILE CATARACTS
If no nucleus is anticipated, a modified Blumenthal approach is performed. The modification involves using only aspiration for these soft nuclei. If the nucleus is harder than anticipated and cannot be aspirated, an appropriate size incision is made and the nucleus is hydrodynamically expressed.
2. SUBLUXATED AND HYPERMATURE
For subluxated lenses (>4 o'clock hours), and for very advanced SHRUNKEN HYPERMATURE CATARACTS with calcified capsules a single stage planned extraction of the nucleus, cortex, and capsule can be performed using the cryoprobe.
However, except for grossly subluxated lenses a standard manual ECCE is preferred in these cases.
3. IMMATURE CATARACTS
Immature cataracts with a red glow (easier for CCC at least for less experienced surgeons like us), and nuclear sclerosis including Grade IV can be extracted using either a manual standard ECCE, manual small incision technique, Hybrid phaco, or phacoemulsification. If a manual small incision technique is used, the Blumenthal technique is preferred. In case of any difficulty, the incision is enlarged and the nucleus is extracted with an irrigating vectis.
Phacoemulsification can also be employed for these cases. If there is a problem "we bail out" to standard manual ECCE.
For switching over to phacoemulsification, a Hybrid technique is initially encouraged. Steps of phaco are performed and here we deliberately convert to standard manual ECCE or alternatively a more experienced phaco surgeon should take over. Instrumentation for phaco fracture is available if the surgeon wants to maintain the small incision status in such situations.
4. INTUMESCENT CATARACTS AND VERY
ADVANCED IMMATURE SENILE CATARACTS
For advanced and intumescent Immature senile cataract (no red glow), and nucleus sclerosis Grade V standard manual ECCE is electively performed by us. The reason is two-fold. Firstly, we have not yet mastered the CCC techniques in such cases. Without a CCC we do not perform phaco. For beginners, we even consider a single tear in the CCC a relative contraindication to proceeding with phaco.
Secondly, brunescent and hard lenses can certainly be emulsified by experienced phaco surgeons. The time taken is longer, the corneas may not look as clear as a standard ECCE, but it can be done. Rather than spending 5 to 7 minutes of phaco time trying to emulsify these hard nuclei, the overall risk-benefit ratio, favours a quick and safe standard manual extraction. Of course, the 5-7 minutes gained by manual extraction is spent suturing the wound.
We feel that phacoemulsification as such, especially for the hard nuclei must be approached with a mindset of "conversion," if one encounters problems. Phacoemulsification of a hard nucleus is really not for anybody but the most experienced phaco surgeons.
| 5. Techniques of Removal of Lens Cortex|| |
Prema Padmanabhan, M.S.
From Sankara Nethralaya, Madras.
Following removal of the lens nucleus the residual lens cortex must be aspirated using a manual or automated system of irrigation-aspiration. This is an essential step of Extracapsular Cataract Extraction (ECCE) requiring careful and meticulous handling by the surgeon. It is vital to remove all cortical matter from the equatorial region to reduce the incidence of postoperative complications, for example, capsular fibrosis.
TYPES OF INSTRUMENTS AVAILABLE
The surgeon has three general types to select from:
1. MANUAL : Mcintyre - Gills - Simcoe
2. AUTOMATED : Cavitron - Coburn
3. VITRECTOR : Ocutome - Site
It is suggested that one should be familiar with the use of a manual system because automated and vitrector systems can fail. Although one may prefer manual or automated systems for cortical aspiration, the vitrector systems are important for ECCE because proper management of posterior capsule tear with vitreous requires closed system vitrectomy instruments in order to avoid leaving behind remnants of cortex and capsule admixed with formed vitreous.
Some vitrector systems, for example, ocutome are not suited for irrigation-aspiration because their aspiration lines do not vent (the pressure does not fall to zero) when aspiration is stopped. Thus, if the posterior capsule is inadverdently aspirated, it is difficult to disengage the capsule without trauma.
Comparison of Aspiration Systems
MCINTYRE COAXIAL CANNULA
This consists of 3 parts. The central cannula for aspiration has a round tip and side port of 0.3 mm. The external cannula is for infusion. It is connected to a 2-way system through which fluid from the bottle flows into the infusion cannula.
Here the surgeon aspirates with a 5-ml syringe in the left hand and infuses fluid into the anterior chamber with his right hand.
IRRIGATION - STRIPPING - ASPIRATION
Regardless of the type of instrument used, there are a few general principles of cortical removal, which are important.
Good coaxial illumination and clarity of the cornea are of utmost importance.
Success depends on the surgeon's experience with the procedure and microscope.
Cortical removal is, in fact, a simple irrigationaspiration procedure done only in mature cataracts. Typically, the irrigation-aspiration is more accurately described as irrigation-strippingaspiration.
Cortical removal can be done by either open system (Gills technique) or Closed system.
The anterior chamber is kept deep with a constant infusion of balanced salt solution (BSS) from a drip. The bottle is kept approximately 60 cm above eye level. The amount of infusion is changed by adjusting the height of the bottle. Ideally, the fluid should contain BSS with adrenalin (1:10,00,000 dilution) to keep the pupil dilated which is essential for cortical removal. Another reason why BSS should be used is because it causes minimal damage to the endothelium.
This is done through a cannula with a small port usually of 0.3 mm and is controlled by hand with a 5-ml syringe, for example, McIntyre cannula, Pearce cannula etc.
1. The microscope is adjusted to a more or less vertical position to optimize the red reflex to help identify the cortex and posterior capsule.
2. The microscope is then adjusted for high magnification and fine focus. As the irrigationaspiration proceeds the foot should be on the fine focus pedal of the microscope. Sharp focusing is essential before aspiration to prevent inadvertent pull on the capsule.
3. The assistant should irrigate the cornea continuously to maintain clarity of the view.
4. When the wound is ready to be sutured at the end of the procedure, the microscope is focused off the visual axis to reduce the risk of photopic injury to the fovea.
ORIENTATION OF THE IRRIGATIONASPIRATION INSTRUMENT
1. The anterior chamber is entered with the infusion on and the infusion port facing parallel to the corneal endothelium (avoiding jet stream injury to the endothelium) and the aspiration port facing anteriorly. The posterior lip of the wound is depressed to avoid stripping of the Descemet's membrane. If the anterior chamber collapses during irrigation-aspiration the surgeon should either increase infusion by raising the bottle or reduce outflow. The latter is accomplished by:
a) trying not to let the wound gape during the procedure,
b) avoiding unnecessary aspiration (aspiration should be done only when the aspiration port is positioned optimally),
c) placing additional sutures, and
d) instilling sodium hyaluronate
2. In general, the aspiration port should be kept facing anteriorly at all times. This protects against inadvertent posterior capsule rupture. Sometimes it is necessary to rotate the aspiration port to the side in order to engage cortex but this is always done under direct visual control and the port is subsequently rotated anteriorly before stripping or aspiration.
HYDRODISSECTION is a technique which separates the nucleus from the cortex when fluid is injected under the anterior capsule and into the cortex. This ensures easier and complete removal of the cortex.
THE CORTICAL REMOVAL
1. Any air and all loose cortical matter present in the anterior chamber should be aspirated keeping the port anteriorly. If the iris prolapses through the wound, the infusion is slowed or additional suture is placed to close the wound. Although iris prolapse may be advantageous by creating a larger pupillary space and exposing superior cortex, it is avoided because it liberates excessive iris pigment and results in localised iris atrophy.
2. After aspirating loose anterior chamber cortex, the smallest aspiration port is used to remove the anterior cortex adherent in the capsular fornix.
3. Closed system techniques allow sufficient pressure to open the fornices of the capsular bag which facilitate engagement of peripheral cortex. Sufficient aspiration pressure is applied to get hold of the cortex handle but not enough to aspirate. Once cortex is caught in the aspiration port, the cortex is stripped from the capsular fornix. Stripping is done by aspirating sufficiently to get and keep hold of the cortex while the instrument tip is moved from side to side as it is withdrawn. Once stripped to the visual axis, suction is applied to aspirate the cortex. If the cortex is not aspirated it is dragged out of the eye.
4. One has to keep track of the areas of cortex that have been removed. If the cortex in a particular meridian is not removed but no cortex is visible in the pupillary area, one has to carefully search for cortex hidden behind the iris.
The capsular bag is opened by a combination of tight wound and sufficient irrigation and with no aspiration, as the instrument is passed along the posterior capsule behind the iris. The aspiration port faces towards the iris. After it is positioned in the capsular fornix, a gentle aspiration pressure is applied as the probe is slowly withdrawn towards the pupillary space. If an edge of the anterior capsule is seen the surgeon must release it, otherwise there is risk of zonular dialysis or posterior capsule tear. One should watch for tension lines on the posterior capsule. If lines are seen, then the surgeon must release the pressure. Once certain that there is only cortex in the cannula, aspiration pressure should be increased to hold on to the cortex as the fornix is stripped clean.
SUPERIOR CORTEX : CORTEX AT 12 0' CLOCK POSITION
It is wise to leave the superior cortex to the end but it is also important to remove the superior cortex because it tends to gravitate towards the centre and thus interfere with vision. This is the most difficult to remove and if you break the posterior capsule, it is better to have taken all the easily removable cortex previously. It is difficult to remove the residual cortex from the 12 o'clock, when the pupil is not fully dilated. Maximum mydriasis should be obtained.
i) Aspiration of the cortex from the 12 o'clock may be aided by purposely prolapsing the superior iris temporarily to get a good view of the superior cortex.
ii) Aspiration of the superior cortex may be aided by using a microiris retractor in the other hand.
iii) Cannulae with curved ends help to retract the iris and superior capsular flap to gain access to the superior cortex.
iv) Where access to the 12 o'clock cortex is still difficult, an irrigating aspirating iris retractor has been designed which deepens the anterior chamber and forces the 12 o' clock cortex into the aspiration port while retracting the iris and superior capsular flap (Peckar double cannula).
v) Aspiration of the 12 o'clock cortex using a straight aspirating cannula with the port directed upwards, entering the anterior chamber at the inferior limbus.
vi) A J-shaped aspirating cannula with the port directed under the capsular flap.
vii) While removing superior cortex the probe/ cannula should be moved to the extremities of the wound, the aspiration port is rotated superiorly and cortex captured and rotated anteriorly as the probe moves from side to side and centrally (ice cream scoop).
Accidental aspiration of the iris is avoided because this liberates pigment and causes miosis.
Excessive aspiration pressure is avoided which could lead to collapse of the chamber and instrument= endothelial touch.
If the anterior capsulotomy does not go as planned, large flaps of anterior capsule can be created which could frustrate the irrigation-stripping-aspiration by blocking the aspiration port or by travelling with the cortex, as the instrument is used to strip the cortex which causes tearing of the anterior capsule leading to zonular dialysis or posterior capsule disruption and vitreous loss.
Once aspiration is completed the posterior capsule should be inspected and residual opacities are removed by careful aspiration or by polishing.
CLEANING THE POSTERIOR CAPSULE
After the superior cortex is removed, the little tags of cortex attached to the posterior capsule should be sul2sequently removed by gently rubbing the McIntyre cannula along the posterior capsule. Sometimes the port is turned posteriorly and gentle suction is applied which engages the posterior capsule and creates fine radiating folds on the posterior capsule. With delicate suction it is possible to remove the remnants of cortex and not tear the posterior capsule. The removal can be done with a Sand Blasted or Diamond Dust Polisher attached to a syringe filled with salt solution.
Sometimes a plaque on the posterior capsule cannot be removed by irrigation-aspiration. A posterior capsulotomy is required if the thickened capsule is central for, it will interfere with vision.
It is sometimes better to leave a little cortex behind than to take the risk of tearing the posterior capsule which can lead to vitreous loss. In certain occasions it is safer to aspirate the residual cortex after insertion of the posterior chamber IOL which protects the capsule from the complication of a tear while aspirating the cortex.
CORTEX REMOVAL IN THE EVENT OF A POSTERIOR CAPSULE TEAR
Sometimes the surgeon is in dilemma as to how to remove the cortical matter in presence of a posterior capsule tear with or without the presence of vitreous. The following points are important.
The margins of the tear should always be visualised while removing the cortex.
The infusion rate should be decreased.
The cortex should be aspirated from the periphery to the margins of the tear, taking care not to enlarge the tear.
DRY ASPIRATION: In this technique, a visco-elastic substance is injected into the chamber which helps to push the vitreous face down. Next, the aspiration of the cortex is carried out without any infusion/ irrigation.
In case of a large rent in the posterior capsule with vitreous admixed with cortex, an ocutome can be used to remove the cortex with associated vitrectomy.
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9], [Figure - 10], [Figure - 11], [Figure - 12], [Figure - 13], [Figure - 14], [Figure - 15], [Figure - 16], [Figure - 17], [Figure - 18], [Figure - 19], [Figure - 20], [Figure - 21], [Figure - 22], [Figure - 23], [Figure - 24], [Figure - 25]
[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5], [Table - 6]