Ординатура / Офтальмология / Английские материалы / Small Incision Cataract Surgery (Manual Phaco)_Singh_2002

discuss the complications that are specific to and more commonly seen in this procedure.

Intraoperative Complications

Posterior capsular rupture Posterior capsular (PC) rupture may occur during hydrodissection or while trying to push the vectis between the nucleus and posterior capsule. It can be avoided by hydroexpressing the nucleus out of the capsular bag and then pushing the posterior capsule well away from the nucleus by viscoelastic. If there is a PC tear, the rent is plugged and the bag inflated with viscoelastic. Dry aspiration of the cortical matter is done with a Simcoe cannula. A posterior chamber lens is implanted in the bag if the tear is small and central. In case of a large tear, vitrectomy is performed and a posterior chamber lens is placed over the anterior capsular rim.

Posterior dislocation of the nucleus If further manipulation is done in the presence of a large PC rent, then there is the risk of nucleus dropping behind in the vitreous cavity. It is rarely seen and is appropriately managed by a vitreoretinal surgeon in the same sitting or the wound is closed and the patient referred to a vitreoretinal surgeon later.

Descemet’s tear Tear in descemet’s membrane can occur due to rubbing of large nuclear fragments against the endothelium during delivery. It can be prevented by keeping the anterior chamber full with viscoelastic during nucleofracture and delivery as well as ensuring that the direction of pull of the vectis should be in the plane of the scleral tunnel.

Frequent shallowing of anterior chamber The anterior chamber shallowing and collapse is quite frequently seen owing to excessive manipulation and use of multiple instruments in the anterior chamber. It can be avoided by frequently injecting viscoelastic in anterior chamber or by using an anterior chamber maintainer (ACM).

Endothelial damage Due to excessive manipulations in the anterior chamber by multiple instruments, endothelial damage is quite significant in this procedure. A higher endothelial cell loss has been reported in comparison to phacoemulsification.4

Intraoperative miosis Many a times pupil gets cons– tricted during the procedure owing to excessive manipulation of iris. Due to this, there may be difficulty in prolapsing the nucleus into the anterior chamber and might warrant use of intracameral adrenaline or multiple

sphincterotomies. An excessive manipulation of iris can result in iridodialysis and cyclodialysis.

Postoperative Complications

Corneal edema Central corneal edema is more commonly seen with this procedure in the immediate postoperative period. This is related to the increased endothelial loss during the surgery.

High intraocular pressure Intraocular pressure has been found to be high in the immediate postoperative period in a number of cases undergoing manual phacofracture. This can be explained by the large amount of viscoelastic used during the surgery. Another factor that can lead to high postoperative intraocular pressure is the large amount of pigment release that occurs during surgery.

Pupillary distortion Intraoperative iridodialysis or cyclodialysis or multiple sphincterotomies if done, can result in distortion in the pupillary size and shape.

REFERENCES

1.Blumenthal M, Ashkenazi I, Fogel R, Assia EI: The gliding nucleus. J Cataract Refract Surg 19: 435-37, 1993.

2.Fry LL: The phacosandwich technique. In: Rozakis GW, Ed, Cataract Surgery; Alternative Small-Incision Techniques. Thorofare, NJ Slack, 91-110, 1990.

3.Kansas PG, Sax R: Small incision cataract extraction and implantation surgery using a manual phacofragmentation technique. J Cataract Refract Surg 14: 328-30, 1988.

4.Vajpayee RB, Sabharwal S, Sharma N, Angra SK: Phacofracture versus phacoemulsification in eyes with age-related cataract. J Cataract Refract Surg 24: 1252-55, 1998.

5.Akura J, Kaneda S, Ishihara M, Matsuura K: Quarters extraction technique for manual phacofragmentation. J Cataract Refract Surg 26: 1281-87, 2000.

6.Blumenthal M, Ashkenazi I, Assia E, Cahane M: Smallincision manual extracapsular cataract extraction using selective hydrodissection. Ophthalmic Surg 23: 699-701, 1992.

7.Akura J, Kaneda S, Hatta S, Matsuura K: Manual sutureless cataract surgery using a claw vectis. J Cataract Refract Surg 26: 491-96, 2000.

8.Akahoshi T: Phaco pre-chop; manual nucleofracture prior to p4hacoemulsification. Operative Tech Cataract Refract Surg

1: 69-91, 1998.

9.Keener GT (Jr): The nucleus division technique for small incision cataract extraction. In: Rozakis GW, Ed, Cataract Surgery; Alternative Small-Incision Techniques. Thorofare, NJ Slack, 163-191, 1990.

10.Quintana M: Implantacion de LIO plegable con facosecion manual y pequena incision. Microcirugia Ocular 6(1): 3744, 1998.

11.Gutierrez-Carmona FJ: Manual multi-phacofragmentation through a 3.2 mm clear corneal incision. J Cataract Refract Surg 26: 1523-28, 2000.

MicrovectisTechnique 21

P Mishra

S Thanikachalam

The cataract surgery has witnessed a phenomenal progress over the years and continues to evolve with the addition of newer surgical techniques and

instrumentation. Michael Mc Farland first conceived the principles of no stitch cataract surgery with phacoemulsification in 1990.1 Earlier Blumenthal in 1987 popularized the technique of Non-phaco SICS in which he described the use of anterior chamber maintainer to hydro-express the nucleus.2 The technique of phaco fracture, where the nucleus is divided before its removal was pioneered by Kansas,3,6 in 1990. In the same year, phaco-sandwich, a bimanual technique of removal of nucleus was described in details, by Luther Fry.4,7 Since 1995, the authors have been using a different technique in which nucleus is expressed with the help of a microvectis. In this technique no anterior chamber maintainer is used, as it is a cumbersome procedure and secondly balanced salt solution (BSS) may not protect the corneal endothelium like viscoelastics. Side port entry is never required as a routine procedure. We recommend this simple and effective method of delivery of nucleus even for rock hard cataracts. The surgeons in the developing countries, particularly in India, who are dealing with more mature and brunescent cataracts may be benefited by this technique.

Indication

Types of cataract All types, and all grades of nuclear cataract.

Objectives

1.To mobilize the nucleus inside the capsular bag.

2.To luxate the nucleus subsequently into the anterior chamber.

3.To express the nucleus with the help of a microvectis / lens loop.

Wound Construction

Scleral tunnel incision, which varies from 5-8mm depending on types of cataract.

Viscoelastics

Liberal use of low molecular viscoelastics to reform the anterior chamber as and when required.

Instrumentation

Nuclear rotation IOL dialer/Sinskey hook or bent 26G. needle.

Nucleus expression Microvectis (3-4 mm)/micro-lens loop.

Anaesthesia

Non-phaco SICS can be performed under peribulbar or topical anaesthesia. Peribulbar anaesthesia was achieved by giving two injections, mixture of 5 cc xylocain (2%) and 5cc bupivacaine (0.5%) by two points technique. In selective cases proparacaine (0.5%) is used as topical anaesthesia.

Capsulorhexis

Continuous curvilinear capsulorhexis originally described by both Gimbel (Canada) and Neuhann (Germany), is usually performed with a bend 26G needle or masket capsulorhexis forceps. A rhexis of 6.5 to 7.5mm is preferred, however, two relaxing incisions at 2 to 10 o’clock is usually required to prolapse the nucleus easily in nuclear cataracts.

Hydrodissection

Good hydrodissection should be performed to separate the nucleus from its capsular attachment. The anterior capsule is elevated with a 26G cannula and BSS is injected slowly and continuously from a 2ml syringe.

When completed nucleus appears to move forward following, which it must be freely rotatable within the capsular bag.

Nucleus Expression

Although there are different techniques available for nucleus management namely phaco-sandwich, phacofracture, hydro-expression, irrigating vectis, etc. we restrict our discussion to removal of nucleus by microvectis technique.

After reforming the anterior chamber with viscoelastics the superior pole of the nucleus is engaged, lifted and rotated with the help of an IOL dialer and prolapsed into the anterior chamber (Figs 21.1 and 21.2). The nucleus rotation is done either clockwise, anti-clockwise or both to luxate the nucleus completely into anterior chamber. Once the superior pole lifts up viscoelastics may be injected underneath, to make nuclear rotation easy. Viscoelastics is placed both above and below the nucleus when it luxates into anterior chamber. This step is essential

Fig. 21.1: Nucleus is rotated with dialer

Fig. 21.2: Necleus is prolapsed in AC

Fig. 21.3: Microvectis is introduced below the nucleus

Fig. 21.4a

to avoid endothelial damage to cornea. A microvectis, that is very small, 3-4 mm in size is introduced under the nucleus following which the nucleus is expressed (Figs 21.3 and 21.4a and b) by applying forward pressure gently. At the same time minimal amount of depression of sclera, the posterior lip of wound is done by the shaft of the vectis. The above mentioned step is carried in a more controlled fashion under direct visualisation to avoid trauma to cornea and iris. Sometimes the epinucleus or portion of cortex will be sheared off by the anterior lip of the incision without damaging the endothelium. The remaining portion of cortex and epinucleus can be easily rotated and removed either by viscoexpulsion, or aspirated by Soimcoe 1/A cannula.

Viscoexpulsion is achieved by injecting low molecular viscoelastics into the anterior chamber while depressing the posterior scleral lip simultaneously. For easy delivery of nucleus we recommend incision of 7.5 to 8 mm for nuclear cataract (Fig. 21.5) and to 7.5 mm for cortical cataracts. The frown incision is placed 2 mm or more, posterior to limbus, i.e. wider tunnel is fashioned to minimize postoperative astigmatism. Two relaxing incisions over the capsule are usually required to prolapse the nucleus into the anterior chamber and to avoid complications like capsular tear or zonular dialysis in hard cataracts. Similarly in these cases inner entry of wound can be enlarged to desired length to facilitate easy delivery of nucleus. The authors have analysed 500 cases that underwent cataract extraction with IOL implantation by using this technique, in two cases there were inferior iridodialysis and hyphaema because of iris trapped between vectis and nucleus during its delivery when the pupil was not fully dilated. This can be avoided easily by injecting adequate amount of viscoelastics into the

Fig. 21.5: AC is formed with air bubble

anterior chamber both above and below the nucleus. Minimal corneal oedema was encountered in its upper part in 5 to 6 per cent cases, which subsided within two weeks of surgery. In paediatric cataracts as there is virtually no nucleus; the cortex may be easily removed by viscoexpulsion or by irrigation aspiration.8 It has been observed that endothelial loss in non-phaco SICS is between 10 and 12 per cent. The damage to the endothelium usually occurs during nucleus expression mostly in hard cataracts. The nuclear fragments may also touch the corneal endothelium during irrigation aspiration. Our own unpublished data show that the induced astigmatism is never more than 1.50 D even for relatively large incision in nuclear types of cataract, as these incisions are placed more posterior to the limbus. One question that will no doubt be asked, “why not to suture such a large incision.” The logic is very simple if the tunnel is stable in 6 mm why not in 8 mm i.e. 1 mm more on either side. In our series of 200 cases, we have observed that the wound remains stable (Fig. 21.5) even with 10 mm tunnel provided the tunnel dissection is perfect and its width is made longer (external scleral incision more posterior).

The advantages of this technique are that, it has virtually nil learning curve. It is relatively easy to perform, repeatable, cost effective and does not require bimanual technique, and at the same time it gives fairly excellent results. It is true that, despite longer incision placed for nuclear types of cataract we could achieve watertight, self-sealing sutureless wound in all cases (100%). Both in terms of technique and quality this is no doubt, an alternative to phacoemulsification in expert hands.

Practical Pearls

1.Ensure good mydriasis throughout the entire procedure.

2.Liberal use of viscoelastics is necessitated as and when required through out the procedure.

3.Good capsulorhexis is essential, but not mandatory for easy rotation of nucleus and its luxation into the anterior chamber. However, this technique can be performed even with can-opener capsulotomy.

4.Relaxing incision one or two may require for hard cataracts.

5.Internal incision, entry to anterior chamber can be widened in accordance with the size of nucleus even after its prolapse into anterior chamber.

6.Side port entry may be required in difficult cases for removal of sub-incisional cortex.

7.If the capsulorhexis is small and no relaxing incisions given, luxation of nucleus to anterior chamber becomes traumatic and may lead to zonular dialysis.

8.To make the rotation and subsequent luxation of nucleus into anterior chamber easy, viscoelastics is injected under the superior pole of the nucleus once it is lifted up.

9.Viscoelastic must be cushioned between nucleus and endothelium, also between nucleus and iris; so that free floating nucleus is easily expressed out.

10.Following introduction of microvectis under the nucleus, anterior chamber must be reformed with viscoelastics, if it becomes flat to avoid endothelial damage.

11.Iris should not be trapped in between the nucleus and microvectis during delivery of nucleus.

12.As nucleus rotation is often difficult in soft cataracts, it can be easily done with repeated irrigation and aspiration of dislodged cortical matter.

REFERENCES

1.Mc Farland MS: Mc Farland surgical technique. In Gills JPM, Sanders DR (Eds): Small Incision Cataract Surgery: Foldable Lenses, One Stitch Surgery, Sutureless Surgery. Slack Inc. Thorofare, NJ 107-16, 1990.

2.Blumenthal M, Moisseiev J: Anterior chamber maintainer for extracapsular cataract extraction and intraocular lens implantation. J Cataract Refract Surg 24: 160-65, 1987.

3.Kansas P: Phacofracture. In Rozakis GW (Eds): Cataract Surgery: Alternative Small Incision Techniques. New Jersy, USA: Slack Inc. 45-70, 1990.

4.Luther Fry: The phacosandwich technique. In Rozakis GW, Aziz YA et al (Eds): Cataract surgery–Alternative Small Incision Technique. Thorofare NJ, Slack Inc. 71-110, 1990.

5.Mishra P: Small incision cataract surgery (SICS). http://

.www.indmedica.com/ophthal/cyberlecture 1-4, 2000.

6.Bartovb E, Isakov I, Rock T: Nucleus fragmentation in a scleral pocket for small incision extracapsular cataract extraction.

J cataract Refract Surg. 24(2): 160-65, 1998.

7.Bryand WR: Cataract surgery: Alternative small incision technique. In Rozaki GW (Eds): New Jersey; Slack Inc. Thorofare.

8.Mishra P: Cataract surgery in children. http://.www. indmedica.com/ophthal/cyberlecture.1-5, 2000.

Blumenthal’sModified 22

Technique

KPS Malik

Ruchi Goel

Ophthalmic surgery has seen the revolution of IOL implantation in the last 2 decades. The focus of attention has shifted to faster rehabilitation of patient to his job. Phacoemulsification, a modern tech-

nique is improving everyday to make it safe technique in all hands. Unfortunately, lack of training facilities, cost and maintenance problem of machine has made this procedure limited to big cities/institutions only.

Alternate small incision cataract surgery techniques are also being practiced by many eminent surgeons of the world. Anterior chamber maintainer assisted mininuc technique of Professor M Blumenthal and other techniques practiced by surgeons like WR Bryant, Luther L Fry, Peter Kansas, etc. are keeping alive the interest in manual small incision cataract surgery.

These procedures are all the more relevant for the developing world. Phacosurgery is expanding quite rapidly in large cities but many government institutions and other practitioners are still struggling to keep pace with advancing costly techniques. Alternative small incision cataract surgery has the advantage of low cost, good postoperative results enabling early rehabilitation of patients. The final aim of all surgeons should be the same–to provide safe, early, reliable and reasonably priced emmetropia.

Practicing steps of alternate small incision cataract surgery will place every surgeon on a solid foundation to switch to phaco surgery, bypassing the notoriously steep learning curve of phaco surgery.

Preoperative Preparation and Anaesthesia

A medical clearance is obtained. Wide spectrum antibiotic drops topically every four hours a day before surgery is instilled. Mydriasis is achieved using cyclopentolate 1 per cent or tropicamide 1 per cent along with phenylephrine 5-10 per cent drops. Topical 0.03 per cent flurbiprofen

or diclofenac sodium 0.1 per cent every 20 minutes thrice will maintain intraoperative mydriasis.

Peribulbar retrobulbar/subconjunctival/sub-Tenon/ topical/intracameral preservative free xylocaine with or without facial block can be used.

Our preferred technique is:

1.Topical xylocaine 4 per cent/Proparacaine 0.5 per cent 4-5 times.

2.3 cc xylocaine 2% + 3 cc bupivacaine. 75 per cent as a inferior temporal peribulbar injection. 3 cc is injected peribulbar, needle is withdrawn, directed lateral to lateral canthus, deep enough to inject the solution around the branches of facial nerve. This one prick

anaesthesia should take care of every need of SICS. No use is made of mannitol, diamox, massage, pressure or superpinky. The need is for normotensive eyeball. Some movements of eyeball are acceptable and would

not interfere with smooth execution of the procedure. Concept of hypotony was introduced for safe ECCE

where in surgeons made 13-15 mm corneoscleral incision. Iris prolapse or lens extrusions were common bugbears in absence of hypotony. Physiologically a normotensive eyeball is the best proposition as vascular dynamics of retinal and uveal tissue are minimally disturbed in normotensive state . The following flow chart indicates the advantages of maintaining a normotensive eyeball .

Maintenance of Vascular Dynamics of Eyeball

↓

No prostaglandin

↓

No inflammation

↓

No CME

↓

No choroidal haemorrhage

↓

Intact blood aqueous barrier

In small incision cataract surgery as practised by Dr Blumenthal, ‘AC maintainer system’ keeps the AC deep and IOP at normal or higher level. This pressurised state of eye is required for easy hydroexpression of nucleus from the eyeball.

Hypertonic state of the eye ball also facilitates the following:

1.Introduction of MVR for sideport entry or AC maintainer.

2.Dissection of sclerocorneal tunnel.

3.Even for curvilinear capsulorhexis the deep AC and pressure on anterior capsule is necessary to counter the lenticular pressure.

4.Hydroexpression of epinucleus, cortex or blood.

Sclerocorneal Pocket Tunnel Incision

Success of small incision cataract surgery depends on efficient, smooth and functional construction of a clean edged sclerocorneal pocket incision of suitable dimensions. The placement of initial incision posteriorly on sclera has many advantages, namely stable section, early healing, less induced astigmatism. It has been shown by Trasher and Boerner that a 9 mm scleral incision will induce astigmatism as much as that induced by a 6 mm limbal incision. Jaffe has stated that 7 mm incision, 2 mm behind the limbus can be left unsutured.

So we have following advantages of scleral placement of incisions:

1.Less induced postoperative astigmatism.

2.Faster stabilization of refraction.

3.Less tendency towards against the rule astigmatism.

4.Even if a suture is applied, the knot remains buried deep in the section covered by full thickness tenon and conjunctiva therefore there is no irritation by the protruding ends of the suture.

Technique of making the sclerocorneal pocket tunnel incision The incision area is prepared by detaching the conjunctiva from limbus at 11 to 2 O’clock position. The conjunctiva is undermined, attachment of tenon is severed. All episcleral tissue should not be removed as it initiates the healing. Light and minimal cautery is applied on perforating vessels or large surface vessels. Excess cautery can lead to shrinkage of tissue and is best avoided.

Making the Groove

Site The site and shape of scleral groove will depend on type of incision planned and AC depth. In a hypermetropic small eye with shallow AC one should not make a

groove too far behind the sclera as it will make the entry of instruments difficult and will also pry open the section with every manoeuvre.

Incisions can be of following shapes:

1.Straight

2.Frown

3.Inverted V, with apex pointing towards limbus.

Best instrument for initial groove is guarded diamond knife set at a depth of 0.3 mm. Many experienced surgeons can make brilliant grooves with blades of any material or configuration. We use 15 number blade on BP knife or 15 degree angled knife for making the initial groove. Site of groove behind the limbus is dependent on planned configuration of sclerocorneal tunnel. Three types are shown in the Figure 22.1.

1.Straight A straight line groove is made parallel to limbus about 5.5 to 6.5 mm in length depending on hardness of nucleus. The groove is usually 1.5 to 2 mm behind the limbus.

2.Frown shaped A parabolic groove convex towards limbus is made 1.5 to 2 mm behind limbus centered at 12 O’clock.

3.Inverted V The two arms of inverted V, AB and CB meet at an angle of 120 degrees. A and C being 2 to 2.5 mm behind the limbus. Straight distance between A and C being 5.5 to 6.5 mm. The point B or apex of

V falls short of touching the limbus (Fig. 22.1).

Fig. 22.1: Types of incisions

TUNNELING FORWARDS

After the initial groove has been defined with a clear cut sharp incision, the 2.8 mm crescent blade, disposable or diamond, is engaged in the groove. It’s tip is tilted anteriorly to follow the curve of limbus and dome of cornea. Maintaining uniform thickness of dissection, tunneling should be performed anteriorly upto 2 mm of clear cornea. While dissecting the lateral area the blade should not be moved straight but tilted downwards following the slope of lateral cornea. The blade can be tilted 90 degree medially or laterally to dissect pockets in cornea and sclera. At the end of the dissection we would have the following types of sclerocorneal pocket tunnels.

Precautions

Not following the curve of cornea or globe can result in premature entry into AC or buttonholing of the anterior walls of the tunnel. Tunnel is best dissected in normotensive eyeball. If the eye appears soft one can inject viscoelastic to make it tight, before continuing the dissection (Fig. 22.2).

After tunnel has been dissected, entry is made into the anterior chamber. The capsular opening is best made through a valvular sideport created at 10 O’clock by MVR blade. Viscoelastic is injected to make the eyeball hypertensive (30–35 mm of mercury). Small side port entry will allow the chamber to remain deep, will have minimal leak.

Three types of capsular openings can be made, continuous curvilinear capsulorhexis, envelope or can-op rhexis (Fig. 22.3).

Fig. 22.3: Making curvilinear capsulorhexis

Continuous curvilinear capsulorhexis (CCC) CCC is a landmark step in the safety of IOL surgery. CCC has multiple advantages in phaco as well as non-phaco SICS such as:

1.Safe hydroprocedures.

2.Safe nuclear rotation and manipulation in AC.

3.Central IOL placement with minimal decentration.

4.Safer cortical clean up and posterior capsular polishing.

5.IOL placement on intact rhexis margin in case of posterior capsular tear.

CCC was developed by Gimbel, Neuhann and Shimizu, independent of each other in the mid 1980’s.

Procedure

Through the sideport entry viscoelastic is injected to deepen the AC and counter any vitreous thrust. In case of hypermature cataracts, dyes which can stain the anterior capsule, can be used. A suitably bent 26G needle can be used as a cystitome. The first bent is just near the tip at right angle and the second bent is at an obtuse angle to allow easy manipulation in the anterior chamber. A puncture is made in the centre of the anterior capsule and a tongue shaped flap is lifted. This flap is everted, flattened on the capsule and manipulated anticlockwise (our way) or clockwise, applying shearing force. The flap is flattened out again and again, keeping the shearing junction in sight. Pulling far away at the flap will have tearing effect and may result in loss of control. The final tear is from outside to inside. If CCC

appears small, continue in spiral fashion all over again, enlarging the CCC.

Precautions

1.Do not disturb the cortex otherwise visibility may be lost.

2.Reinject the viscoelastic if chamber shallows because the tear may go to the periphery. Stop, refill the AC, examine and proceed. It is very important to counter the positive pressure of vitreous.

3.CCC should not be less than 6 mm for this procedure.

Envelope Technique

Envelope technique is preferred over can-opener in cases where CCC is difficult. In case of morgagnion, intumescent Black/brown or hypermature cataract envelope making is an easy and excellent technique which allows all the benefits of CCC.

A scratch mark is made at the junction of lower 2/3rd and upper 1/3rd of capsule. Further tiny cuts are given medially and laterally saving 1 mm of capsule on either side, cuts are then joined by a horizontal line. This type of capsular opening is useful for placement of IOL in the bag. After placing the IOL in the bag the remnants of anterior capsule are cut off by cystitome or Vannas scissors.

Can-op Rhexis

A CCC may be given relaxing cut at 11-12 O’clock position for nuclear manipulation out of the rigid CCC margin in cases of hard or large nucleii. Can-op rhexis opening will give all the benefits of CCC and allow in the bag placement of IOL. Therefore, while performing CCC if one loses control and part of it has to be completed by can opener technique, it is still preferable to have some round margin of capsular opening.

Fixing the AC Maintainer

Fix the AC maintainer at this stage as AC is still deep with viscoelastic. MVR entry is made at 6 O’ clock parallel to limbus, away from the vascular arcade of cornea. The AC maintainer, a hollow steel tube with 0.9 mm outer and 0.65 mm inner diameter is entered with bevel up and then turned 180 degrees so that the bevel faces the iris. The AC maintainer is always inserted from the temporal side. The tube of AC maintainer is attached to BSS bottle suspended 60-70 cm above the patient’s eye.

Completing the Tunnel

The prior dissected tunnel is inflated with visco to facilitate entry of slit knife. 3.2 mm angled keratome (slit knife) disposable, steel or diamond is introduced at 12 O’clock, after traversing the full length of tunnel it is dipped down in AC and knife is introduced till the elbow. It is noteworthy that the Descemet’s is entered not at right angle but in sloping fashion. Subsequent cuts are made by repeated thrusts of the 3.2 mm knife in rest of the dissected cornea. Conscious effort should be made to cut while going in and not while coming out. These manoeuvres of slit knife should be in quick succession to cover whole of predissected area including side pockets. If chamber shallows while cutting in the tunnel, the chamber should be filled up with viscoelastic before reintroducing the knife. At the end we shall get a funnel shaped sclerocorneal pocket tunnel that is narrow outside and wider in the cornea. It is to be noted that side pocket dissections are akin to the bulge of the oral cavity of a snake, which can accommodate a larger animal than it’s apparent mouth size. At the time of nuclear expression a large nucleus too can get engaged because of extraspace created by side pockets in cornea and sclera.

Hydroprocedures

Hydroprocedures comprise of hydrodissection and hydrodelineation. The aim is to separate the lens nucleus, epinucleus and cortex from capsule and the lens lamella from the cortex and its different layers. This facilitates rotation of nucleus from its bag into the anterior chamber. Therefore thorough hydroprocedures play a key role in this surgery. Michael Blumenthal first described hydroprocedures but Faust gave the term hydrodissection. These procedures can be carried out with anterior chamber maintainer being in on or off state.

Hydrodissection

AC is emptied of viscoelastics remaining after capsulorhexis. 1 cc Ringer lactate/BSS is loaded onto 2 cc syringe and is injected behind the rhexis margin using a suitably angled cannula with a blunt tip (like Healon cannula) in different directions. The bolus of fluid injected between anterior capsule and cortex dissects all around the capsular bag and separates it from the nucleus. The cortex is completely dissected from the capsule freeing the entire lens nucleus, epinucleus, cortex from the capsular bag thereby facilitating nuclear rotation and

manipulation out of it’s bag. Indication that the dissection has occurred is a shallowing of anterior chamber, signifying entrapment of fluid in the subcapsular layer of the lens at one pole. Intermittent gentle tapping releases the fluid collected behind the nucleus thereby completing the hydrodissection (Fig. 22.4).

Fig. 22.4: Hydrodissection

Hydrodelineation/Hydrodelamination/Hydrodemarcation

The fluid is injected between the epinucleus and nucleus. The fluid wave appears as a golden ring under the surgical microscope. The procedure is carried out using either a straight cannula or one with 2 sideports. The final result is a debulking of nucleus. The cannula is passed into the nucleus until it meets resistance where the soft outer nucleus ends and a firm inner nucleus begins. At the point of resistance the cannula is pulled back a fraction of a mm and fluid is injected. The fluid passes into the body of the cataract and creates a cleavage plane. This may be repeated at a different site. In a very hard cataract, the inner nucleus may extend right out to the capsule and cleavage plane may never be identified whereas in a soft cataract multiple planes may be isolated. Thorough hydroprocedures reduce the size of the nucleus which in turn enable the surgeon to deliver it out of a small incision.

Nuclear Management and Delivery

Nuclear prolapse into the AC Adequately sized CCC and thorough hydroprocedures will prolapse the nucleus in the AC. Some of the soft cataracts have fibres firmly adhered to each other as well as with epinucleus. These lenses need manual manipulations or multiple hydro– procedures to finally free them out of the bag.

We use a Sinskey’s hook to guide the nucleus out of the bag. AC is filled with viscoelastic. The hook is

introduced between 10 and 12 O’clock positions near the edge of the rhexis margin and passed behind the upper pole of the nucleus. Nucleus is engaged, the hook is pulled upwards and towards 12 O’clock. Once the bulk of the nucleus is out, the rest is cartwheeled out clockwise or anticlockwise into the AC.

Precautions

1.Never hold the edge of the section with forceps, hold at the limbus or the sclera to stabilize the globe while carrying out manoeuvres in the AC. Holding the section will roughen the edges, delaying the healing and leading to poor co-optation of the wound.

2.Avoid repeated entry into the section.

3.Fill up the AC with viscoelastic–inject it in front and behind the nucleus.

4.Never use rough-ended cannula in the section or you may damage the Descemet’s membrane.

5.Consciously keep a watch on Descemet’s for any manoeuvres in the AC.

Nuclear Delivery by Hydroexpression

This is the most important step in small incision cataract surgery. The skill and experience of operator guides him to make a correct size outlet depending on the hardness of nucleus. The goal is a smooth delivery of reduced size nucleus leaving behind other parts of the lens. AC Maintainer, attached to a bottle of Ringer lactate/BSS, suspended 70 cm above the patient’s head, is brought into play now. Once the reduced size nucleus has been brought out in deep AC, suspended in an ocean of viscoelastic, a lens glide is passed from 12 ‘o clock behind the nucleus. Care should be taken that the glide does not injure the iris, ciliary body or capsule during its journey behind the nucleus. Once the glide is in position, the AC maintainer flow is switched on fully. The tip of forceps is used to apply a firm pressure on the lens glide, on the scleral side of section. The nucleus will be taken up by section and the adjacent pockets. A few intermittent taps on the lens glide will see the nucleus delivered out, deepening the AC. A few more taps will allow the cortex, epinucleus to be washed out of the eye. We pull out the AC maintainer at this stage. Simcoe cannula is further used for cleaning up the remaining cortex.

Assisted delivery In case nucleus is stuck up in section, lifting the bottle up will raise the pressure of fluid in anterior chamber and help in nucleus expression. If tip of the nucleus shows but no further progress is there, a 23 gauge needle can be held in left hand and applied at