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

Fig. 18.2: Tunnel length with crescent blade

Fig. 18.4: Dimple at the cornea just before entering AC

Blumenthal incision should be 2 mm wider than the scleral tunnel (Fig. 18.3). The crescent should be swept with pressure away from anterior chamber.

3.Entry into the anterior chamber is made with an angled 3.2 mm keratome. Angled keratome should be sharp. Blunt keratome leads to Descemet’s detachment. A dimple is seen when pressure of keratome is applied towards anterior chamber (Fig. 18.4). The movement should be controlled otherwise it may hit the capsule and capsulorhexis would be difficult to make in this condition (Fig. 18.5).

4.Viscoelastic is injected into the anterior chamber (Fig. 18.8). Here the care should be taken to slightly press the scleral side so that the aqueous can come out and only the viscoelastic remains. It will make the anterior capsule taut and capsulotomy becomes easier.

5.Capsulotomy Any types of capsulotomy can be done in SICS-can-opener, envelope or capsulo- rhexis—all are useful (Fig. 18.9). In fact author

Fig. 18.3: Extension on other side

Fig. 18.5: Entry into AC by 3.2 angled keratotome

suggests can-opener and envelope technique in initial few cases, because the prolapse of the nucleus in AC becomes easier. Size is important in case one prefers to make capsulorrhexis. 0.1 ml trypan blue dye is injected beneath the air bubble through the side port (Figs 18.6 and 18.7). It should not be less than 6.5 mm and slightly eccentric on the upper side. Both these things will help in prolapse of the nucleus in the AC. In case the capsulorhexis is small, whole nucleus with capsular bag can come in the AC. Then it would be intracapsular rather than extracapsular surgery. One should take precaution here. Other way round too large a capsulorhexis might extend into the periphery (Fig. 18.8).

6.Hydrodissection Aim of hydrodissection is to see that all adhesions between cortex of lens and capsule are broken and a free rotating nucleus is visible. The technique of hydrodissection has been described elsewhere. Two points need to be mentioned here. Do not try to strain the zonules by pushing your

Fig. 18.6: Scleral incision with single air bubble

Fig. 18.8: Capsulorhexis with Trypan blue

rotating instrument too hard. If hydrodissection is complete there is no difficulty in rotating the nucleus. If rotation is difficult, it means incomplete hydrodissection. So, inject more fluid beneath the anterior capsule and retry the rotation. Secondly, fluid injection should be slow and only optimum amount should be injected. Hydrodelineation is a must in SICS. It helps in debulking the nucleus and delivery of nucleus through smaller incision becomes easier.

7.The incision is enlarged with the help of 5.5 mm angled keratome after injecting sufficient amount of viscoelastic (Figs 18.9 and 18.10).

8.Nucleus prolapse in AC This is single important step in a successful SICS. Nucleus prolapse is easier if the pupil is widely dilated and a good rotation of the nucleus is achieved after hydro-dissection. In initial few cases it is easier to prolapse nucleus in AC, if can-opener or envelope type of capsulotomy has been done. The nucleus is prolapsed by rotating the nucleus after filling the chamber with viscoelastic.

Fig. 18.7: Dye being injected under the air bubble from side port

Fig. 18.9: Extension of incision with 5.5 mm keratotome

The moment, rim of nucleus is visualized, the cannula is brought below the rim of nucleus; and again viscoelastic is injected in between the nucleus and perinucleus. The upper pole of nucleus will prolapse in the AC. In small pupils one can depress the nucleus at five O’clock with the cannula. The upper pole at 11 O’clock, then can be seen easily. Now the nucleus is rotated towards 12 O’clock. Thus achieving the aim of prolapse of upper pole of nucleus (Fig. 18.11). Once you are sure about prolapse of nucleus in AC inject more viscoelastic between the cornea and anterior surface of nucleus and also behind the nucleus This maneuver requires copious use of viscoelastic to prevent injury to the corneal endothelial cells. Once this is achieved the nucleus is now ready for delivery.

9.Delivery of nucleus The author uses irrigating vectis and a Sinskey type of dialer but the difference here is that it is like a hammer at the end and much thicker than the dialer (Fig. 18.12). Thus it has blunt end,

Fig. 18.10: Enlarged incision for accomodating nucleus

Fig. 18.12: Irrigating vectis and dumbel

which prevents posterior capsule rupture. The author calls it a dumble. Fluid flow through the vectis is checked. First thing is to enter anterior chamber through the incision with the dumble in your left hand (Fig. 18.13). This is kept at the center of nucleus. No pressure is applied. Then the irrigating vectis is passed behind the posterior surface of nucleus in such a way that the nucleus is sandwiched between these two instruments. The pressure is applied from below the nucleus and also on the anterior surface of lens. At the same time the sandwiched nucleus is brought out of the wound (Figs 18.14 and 18.15). Two things will results. If the lens is soft it will come out in one go. If it is hard it may break into several pieces. A part of that will come out sandwiched between two instruments. Remaining pieces of nucleus are taken out by either viscoexpression or by holding the pieces with Mcpherson’s forceps. One needs to be very cautious here as the anterior surface of nucleus or its pieces

Fig. 18.11: Nucleus prolapse in AC only upper pole

Fig. 18.13: First enter with dumbel, on anterior surface of lens. Second instrument is irrigating vectis, which enter behind the nucleus

Fig. 18.14: Nucleus sandwiched between irrigating vectis and dumble

should always have viscoelastics in front of them. In case one finds difficulty in delivering out the nucleus the incision length needs to be increased.

Fig. 18.15: Nucleus being delivered through tunnel sandwiched between irrigating vectis and dumbel

Fig. 18.17: Cortical wash

Fig. 18.19: View of clean posterior capsule after cortical wash

This problem is normally encountered in brown hard cataracts. Rarely in very big nucleus the tunnel has to be abandoned and a routine ECCE is performed.

10.Remaining debris is perinucleus and cortical matter

These are removed by two-way Simcoe cannula,

Fig. 18.16: Expression of perinucleus

Fig. 18.18: Perinucleus being expressed out of tunnel

Fig. 18.20: Conjunctiva is reposited back

which is connected to a BSS bottle by an infusion set. Cannula is opened with full flow. Take this free flowing cannula to 6 O’clock slight pressure on the posterior lip of the tunnel by the cannula will prolapse the perinucleus out of the wound. Remain-

ing material is cortex. A part of this will come out with perinucleus by hydroexpression. Cortical fibres are then aspirated (Figs 18.16 to 18.18). The details are discussed elsewhere.

11.After the posterior capsule has been washed and no fibres are left, intraocular lens is implanted as usual (Figs 18.19 and 18.20).

12.Conjunctiva is reposited back by holding the conjunctiva with two forceps. Cautery is then applied at two ends (Fig. 18.20).

13.Gentamicin and decadron injection is instilled on the top of conjunctiva. There is no need of giving any subconjunctival injection.

FURTHER READING

1.Luther L Fry: The Phaco sandwich technique: In George W Rozakis et al (Eds): Cataract Surgery Alternative SmallIncision Techniques. Thorofare Inc, 71-110, 1995 Indian edn.

For the first time the author learned this technique in Nepal from Dr Hennig, where thousands of cataract surgeries are performed by a simple technique through a 26G needle. The author modified this technique and performed several operations with

great satisfaction.

Surgical instruments required for this technique are described below:

A.For scleral pocket incision:

•Castroviego type of calipers

•For Scleral groove straight blade diamond knife with 45 degree angulation.

•Under mining forward of tunnel by scleral pocket crescent knife with 60 degree angulation.

•A/C entry with 3 mm keratome.

•Side port entry blade 15 degree straight.

•Section enlarging blade 5.5 mm with 60 degree angulation at shaft

B.Instruments for capsulotomy:

•Utrata forceps

•26 gauze needle

C.Instruments for hydroprocedures:

•Hydrodissection cannula 26 gauge with 45 degree angulation with flat tip

•Hydrodelineating cannula

•J shaped hydrodissection cannula for 12 O’clock

D.Instrument to deliver the nucleus (Manipulation of nucleus)

•A single 26 G needle is used for this purpose. 26 G needle is bent like a hook 2 mm proximal to the bevel edge (Fig. 19.1). The bevel edge of eye should be facing outward. It resembles a fishhook. After that the needle is again bent at right angle to the initial bend, so that the hook faces right or left side (Fig. 19.2). Angulation of this bent may be 100 to 130 degrees, it acts like a lever while removing nucleus from the capsular bag.

Instrument for Aspiration of Residual Cortex

• Simcoe cannula regular type

Instrument for IOL Insertion

•MacPherson forceps for rigid PMMA IOL implant

•Inor lens folder for foldable IOL implants

•Inor lens inserter.

Preoperative Clinical Examination

A thorough history and general examination is done in following order :

1.Visual acuity examination to exclude uniocular patient and include patient with accurate PL and PR.

2.Slit lamp microscopy—All the patients are subjected to preoperative slit lamp microscopy on slit lamp. A careful note of the following findings is made.

a.Pre-existing corneal scars that might interfere with the keratometry.

b.Pre-existing corneal endothelial dystrophy, i.e. Fuch’s or corneal guttata that might lead to corneal decompensation.

c.A rough idea of the filtration angle by measuring the distance between cornea and the iris.

d.Status of pupillary dilation to exclude uveitis.

e.Grading the nucleus for its toughness by noting the colour.

f.Subluxation of lens to be reserved for plain ICCE only.

3.Syringing of all selected cases.

4.Intraocular tension with Schiötz tonometer.

5.Conjunctival smear to exclude any infective microbe.

6.Routine hemogram and complete urine examination.

7.Keratometry is done preoperatively in both steep and flatter meridian to record the measured astigmatism.

8.A scan biometry is done in all cases to know exact IOL power. A high axial length denotes high myopia. A scan biometry can also exclude retinal detachment in the cataractous eye.

Method

Lid and globe akinesia is obtained by peribulbar anaesthesia.

Lid retraction by barraquer wire low-tension speculum and superior rectus suturing is done as usual.

Surgical Technique

A fornix based conjunctival peritomy is done between 10.30 to 1.30 O’clock position, superficial scleral blood vessels are cauterized.

Scleral Tunnel Incision

After maintaining haemostasis, a 5.5 to 7 mm of half thickness scleral groove, 1.5 mm behind the limbus is made by a diamond knife. The shape of incision should be frown or antismile.

Scleral dissection is performed by a symmetrical biconvex dissector knife angled 60 degrees having sharp cutting edges on both sides.

Scleral dissection is of half thickness in a given lamella upto 1 mm of clear cornea. This creates a triplanar valve type of self-sealing incision. At 2.30 O’clock position, the anterior chamber is penetrated by a sharp 15 degree angulated side port blade and viscoelastic hydroxymethyl cellulose 2 per cent is injected in anterior chamber This incision is used for entry of manipulation instruments like capsulotomy needle, hydrodissection, hydrodelineation cannula and manipulation of lens.

Anterior Capsulotomy

Anterior capsulotomy is done using a 26 G needle bent and twisted to act as a cystitome. The AC is entered through a side port usually at about 2 O’clock position. The AC is kept deep and formed using a viscoelastic substance. A straight or envelope type of capsulotomy is performed at 12 O’clock position.

Hydrodissection and Hydrodelineation

Hydrodissection is performed using a 1cc syringe and a cannula in which the bent part is 4 mm and tip is flattened. The cannula slides along the exposed hard core nucleus, is inserted obliquely at 12 O’clock into the junction of the hard core nucleus and epinucleus and 0.1-0.3 cc of BSS is injected.

The BSS hydrodissection creates a demarcation line, usually clearly seen by the light reflection (golden ring) created between the nucleus and the epinucleus, or between the epinucleus and the cortex.

Anterior Chamber Entry

Anterior chamber is entered by a keratome blade at 12 O’clock position and chamber is filled with visco elastic. Now the section is enlarged by 5.5 mm wide section enlarging blade. The configuration of this entry should be smile type and size varies according to the pre-evaluated size of the nucleus.

Technique of Nucleus Delivery

Intracapsular tumbling of nucleus with (fish) hooked extraction of nucleus.

After extending the inner incision like a smile fashion, a 26 G needle bent like a hook in mounted on a 2 cc viscoelastic filled syringe. We enter in the A/C injecting visco to make it deep. A downward pressure by hook and visco is applied at 12 O’clock position on the nucleus, through linear capsulotomy site. By this manoeuvre the nucleus at 12 O’clock is pushed downward and inferiorly. Later on it will tumble inside the bag and hook goes posteriorly to nucleus. This time we should inject 1 ml visco inside so that the posterior capsule is pushed back. A space is thus created to move the tip of hook anteriorly to get embedded in mid-substance through posterior surface of nucleus.

After hooking the nucleus we should inject more viscoelastic that makes a positive pressure inside and this positive pressure and a little active extracting pressure by hook delivers the nucleus outside the bag and directly engages it in the scleral tunnel.

A slight more passive (visco assisted) and active (of hook) pressure helps in extraction of nucleus from the tunnel. It should be always kept in mind that every step of nucleus manipulation a pre-judged amount of viscoelastic is injected gradually making nucleus tumble inside the bag and deliver it through scleral tunnel. A well-bal- anced passive pressure of viscoelastic and active movement of hook is the key to success of this procedure.

The case in which difficulties are found during nuclear manipulation should be converted into standard ECCE by increasing the length of incision.

After thorough cleaning of capsular bag and polishing of posterior capsule, depending on the size of incision, a foldable silicone introaocular lens, or a 6 mm optic or a phacolens of 5 mm optic are introduced through scleral tunnel and placed inside capsular bag.

Suture Application

Scleral tunnel incisions are self-sealing incisions that’s why we apply no or a single suture according to need and size of incision. At the end of procedure either BSS solution or single air bubble is injected. At the same time pressure is applied on the eye globe to check the integrity (leakage) of wound.

Follow-up

All the patients are followed up upto two months at weekly interval and corneal condition, Keratometry, visual acuity and any other complications are noted and analysed. In all visits postoperative problems and complications like iritis and corneal oedema are observed and treated accordingly.

Modern cataract surgery aims at the visual rehabilitation of the patients in a minimally invasive manner. The final goal is the removal

of the contents of the capsular bag through the smallest possible incision, and the implantation of a suitable intraocular lens into the bag. Small incision cataract surgery has contributed immensely to accelerated wound healing and minimization of hospital stay of the patient. Two of the main goals of cataract surgery in recent times are to minimize induced astigmatism and achieve rapid visual recovery. The smaller the surgical incision, the lesser is the residual postoperative astigmatism. With the advent of the current technique of phacoemulsification, and the development of today’s state-of-the-art phacoemulsification machines, phacoemulsification, is today, the surgery of choice for extraction of senile cataract. Phacoemulsification allows the removal of a nucleus of 6-8 mm size through an incision size of 3 mm or less. However, the expensive instrumentation and prolonged learning curve involved with phacoemulsification are its major limitations, particularly in developing countries.

If extracapsular cataract extraction (ECCE) is performed through a small self-sealing incision, postoperative visual recovery and stability can rival that of phacoemulsification.

During late 1980s, manual fragmentation techniques of the nucleus began to appear as an alternative to phacoemulsification. In manual phaco-fragmentation techniques, incision size depends on the dimensions and hardness of the nuclear fragments to be extracted from the anterior chamber. Usually, the nucleus is divided into 2 or 3 fragments, which is then viscoexpressed through the incision. Soft cataract can be extracted through a 4.0 to 4.5 mm incision. With hard nuclei, it is usually necessary to increase the wound size to avoid damaging the iris and corneal endothelium.

Small incision cataract surgery (non-phaco) is a cost effective alternative to phacoemulsification. It combines the advantages of small incision surgery with the low cost of instrumentation.

Advantages of Small incision cataract surgery:

1.Less astigmatism

2.Early wound stabilization and early rehabilitation

3.Low cost of surgery

4.Shorter learning curve

There are basically two principle ways of extraction of

cataract by small incision non-phaco surgery. They are:

(1) extraction of the nucleus as a mass without fragmentation,1,2 and (2) extraction of the nucleus after fragmentation.3,4,5

Surgical Techniques

Various surgical techniques of small incision cataract surgery sans phacoemulsification have been described. The principle of small incision cataract surgery involves reducing the size of the nucleus. This can be achieved either by hydro-maneuvers6,7 or by breaking the nucleus into pieces by various nucleo-fracture techniques.

Nucleo-fracture Techniques

Kansas and Sax3 initially described phaco-fragmentation techniques. These are technically more complex than the techniques of nucleus removal without fracture. This involves removal of the nucleus by breaking it into smaller chunks so as to allow their removal through a smaller incision than that required for a conventional ECCE or a small incision manual ECCE without nucleo-fracture.

A frown shaped scleral groove perpendicular to the eyeball surface and of uniform depth of about half thickness of sclera is made. The ends of the frown are approximately 3mm from the limbus while its central convexity is 1.5mm from the limbus. This frown incision, which confines itself to within the astigmatic neutral zone,

provides the best results from astigmatic point of view. The length of incision varies from 5 to 6 mm depending upon the size of intraocular implant. This incision is then tunneled by the use of crescent knife so that the tip of the blade should be 1mm into the clear cornea. The anterior chamber is entered by a 3.2mm angled keratome. A side port is made with the microvitreoretinal blade.

A large continuous curvilinear capsulorhexis of approximately 7.0 mm is made using 26G needle. A large capsulorhexis is essential for prolapsing the nucleus into the anterior chamber. If the capsulorhexis is small, a radiating cut to the capsulorhexis edge is made at the 12 o’clock position to facilitate the prolapse of the nucleus.

Hydro-dissection and hydro-delineation are essential for freeing the nucleus from the surrounding epinucleus and cortex so that it can be easily prolapsed into the anterior chamber without excessive stress. The hydrodissection cannula is placed under the anterior capsule, the capsule is tented and small amount of fluid is injected. This is repeated in all the quadrants. After every injection the nucleus is gently pressed so that fluid seeps out and does not tear the posterior capsule. Hydrodissection should be avoided in posterior polar cataract. Hydro-delineation is done with a 26G cannula by repeated strokes going deeper into the nucleus. The end point of hydro-delineation is the appearance of a golden ring.

The anterior chamber is deepened with viscoelastic (sodium hyaluronate or hydroxypropyl methylcellulose) and the nucleus is gently pushed at one end. If the hydro procedures have been done properly and the nucleus is free, it will lift up at one point. It is prolapsed into the anterior chamber by repeated strokes by hydrocannula. Viscoelastic is injected both behind the nucleus as well as in front of the nucleus to protect the posterior capsule and the endothelium. The whole incision is made fullthickness with a keratome. The nucleus is fractured by using Kansas trisector (Fig. 20.1) and Kansas vectis (Fig. 20.2). The trisector is positioned above the nucleus and Kansas nucleus vectis placed under the nucleus. By

moving the tips of the two instruments towards each other with a constant force, the nucleus is fractured. These nuclear fragments are then visco-expressed and the remaining cortical material is aspirated with a Simcoe cannula.3,4 Maintenance of the anterior chamber is the main surgical concern so as to avoid damage to the corneal endothelium or the posterior lens capsule. This is taken care either by an anterior chamber maintainer (ACM) or by repeated injections of viscoelastic material into the anterior chamber.

A pre-chop technique8 has been described in which the nucleus is chopped into smaller pieces using a sharp chopper. The fragments are then visco-expressed. Risk of damage to the posterior capsule while using this technique can be reduced with the use of a lens vectis or slide behind the nucleus.

Keener’s9 stainless steel loop and Quintana’s10 3-0 nylon loop techniques involve snaring the nucleus and cutting it into smaller pieces before removal.

Another technique called manual multi-phaco- fragmentation (MPF) with a racquet shaped nucleotome and spatula has been described.11 A 3.2 mm clear corneal incision was made and the spatula was placed under and the nucleotome on top of the nucleus. The nucleus was fragmented into 4 pieces by pressing the nucleotome against the spatula. These pieces were extracted out using a sandwich technique by removing the two instruments together. Right and left manipulators were used to displace the remaining fragments for further fragmentation and extraction. This maneuver was repeated until the whole nucleus was fragmented.

Another instrument devised for use through a 3.2mm incision is the Akura5 nucleus puncher. It has the advantage that it need not be inserted beyond the center of the nucleus during nucleus fragmentation, can be used safely in hard cataracts and can be used with one hand. Pieces of the nucleus are punched out and this technique is called the ‘quarters extraction technique’.

Epinucleus and most of the cortex can be removed by hydro-expression. Residual cortical matter is removed by irrigation-aspiration by a Simcoe cannula. The intraocular lens is implanted. Stromal hydration of the tunnel and the side port is done. This prevents the need of any suture.

Fig. 20.1: Kansas trisector

Fig. 20.2: Kansas nucleus vectis

Complications

Apart from the routine surgical and postoperative complications that can be seen during any cataract surgery, certain specific complications can occur during the procedure of manual nucleofracture. Here we will