INTRODUCTION
It is very well proven that cataract surgery is one of the most satisfying and cost-effective surgeries in the medical field, with promising results.1,2 Over the years, it has remarkably evolved: starting from couching through intracapsular cataract extraction (ICCE), conventional extracapsular cataract extraction (ECCE), manual small-incision cataract surgery (MSICS), and phacoemulsification, to femtosecond laser-assisted cataract surgery (FLACS), with each of the techniques having its own advantages and drawbacks.
In the current era, the main goals of cataract surgery are better uncorrected visual acuity with minimal complications and early postoperative rehabilitation. Phacoemulsification uses smaller incisions. This provides better uncorrected visual acuity due to less astigmatism and early postoperative recovery. These advantages make phacoemulsification the preferred technique in the settings where resources are available.
Phacoemulsification, even with all its benefits, may not be an affordable technique in developing countries. Alternatively, MSICS has similar or sometimes even better advantages over phacoemulsification and is more affordable. However, in this era of FLACS, the relevance of MSICS is still often underquoted. To explain the point, the following advantages of MSICS can be pointed out:
- Small-incision cataract surgery can be done in all types of cataracts. Phacoemulsification may be difficult in brown cataracts, black cataracts, and hard mature cataracts.
- Small-incision cataract surgery, irrespective of the grade of cataract, requires the same time. The time duration for phacoemulsification is more in harder cataracts.
- As reported in a study,3 SICS can be done within 3.8–4.2 minutes. This makes it the preferred technique in a high-volume setup.2
- It is affordable. One study points out the cost to be US $17 for ECCE, US $18 for MSICS, and US $26 for phacoemulsification.4
- Unlike phacoemulsification, SICS does not require a costly machine.
- Small-incision cataract surgery training makes transition to phacoemulsification easier.8 It becomes handy for conversion from phacoemulsification if the need arises.
In summary, phacoemulsification, being an expensive technique, cannot be employed as the standard procedure in developing countries. MSICS offers merits similar to that of phacoemulsification along with the advantages of shorter learning curves and lower costs. Even today, MSICS is practiced by many eminent surgeons in our country as well as across the world with excellent outcomes. The immense demand for it is visible. Hence, this communication is an attempt to discuss the techniques of MSICS. The steps of the technique are described below (pertaining to the right eye):
TECHNIQUE
Instruments
Figure 1.1 shows the various surgical instruments used in MSICS.
OCULAR ANESTHESIA
The purpose of anesthesia is to safely provide comfort to the patient while optimizing conditions for the surgeon.
Fig. 1.1: Instruments for manual small-incision cataract surgery (MSICS). (a) Lieberman eye speculum. (b) Superior rectus holding forceps. (c) Westcott's spring scissors. (d) Corneal forceps. (e) Bard-Parker handle with number 15 disposable surgical blade. (f) Crescent knife. (g) 15° side port blade. (h) Keratome. (i) Cystotome. (j) Hydrodissection cannula. (k) Sinskey hook. (l) Cyclodialysis spatula. (m) Irrigating vectis. (n) Simcoe cannula. (o) Shepard intraocular lens (IOL) holding forceps. (p) Vannas scissors. (q) Needle holder.
Objectives of anesthesia in intraocular surgery are to achieve akinesia of the globe and lid, anesthesia of the globe, lids, and adnexa, control of intraocular pressure, control of systemic blood pressure, and relaxation of the patient.
The various types of anesthesia available for intraocular surgery are retrobulbar, peribulbar, parabulbar, topical, topical with intracameral, facial, sedation, and general anesthesia. However, a detailed discussion of all these techniques is beyond the scope of this article. We will discuss in brief some of the commonly employed techniques of anesthesia that we follow in SICS—retrobulbar, peribulbar, and sub-Tenon's anesthesia.
Composition of Anesthetic Solution
- Two percent lignocaine with or without adrenalin.
- Bupivacaine 0.5–0.75% solution.
- Hyaluronidase: Dose varies from 5 IU/mL to 150 IU/mL. One vial of 1,500 IU is added in 30 mL lignocaine solution making an effective concentration of 50 IU/mL.
Retrobulbar Block
The retrobulbar block involves injection of local anesthetic into the muscle cone in the retrobulbar space. Its advantages include faster take-up of block, better akinesia, less quantity of anesthetic solution is required, and is not associated with chemosis as is often seen with peribulbar block (faster onset of action or faster uptake of block). All these factors facilitate high-volume, efficient cataract surgery.
Complications
Possible complications include retrobulbar hemorrhage, globe perforation, retinal vascular occlusion, and subarachnoid injection. Though the literature reports the rate of complications associated with retrobulbar block to be higher than that of peribulbar blocks, our experience with retrobulbar blocks over the years has been good and associated with minimal complications.
Technique
- The patient is asked to look in the primary gaze position, which keeps the optic nerve out of the needle's path.
- A blunt 35-mm, 22-gauge needle with a 5-mL syringe is used.
- Palpate the inferior orbital margin at its outer one-third and clean the skin in this area with an alcohol swab.
- In the lower lid, the junction of the medial two-thirds and the lateral one-third is marked. The needle is introduced at this point. It should remain parallel to the orbital floor.
- As the needle advances, it enters the muscle cone. The entry into the muscle cone can be felt as the change in resistance as it pierces the intermuscular septum.
- Initial rotational eye movements followed by a rebound should occur. No need to advance the needle beyond this point.
- Inject slowly 1 mL/10 seconds.
- Minimize needle movement to prevent possible laceration of the blood vessels.
- After injecting the drug, the needle is withdrawn and pressure is applied over closed lids with a “pinky ball” or with hand for 1–2 minutes, intermittently.
- Unlike peribulbar block, retrobulbar block requires a separate facial block.
Signs of a Good Block
- Ptosis
- Akinesia (or minimal movement)
- Inability to fully close the eye once opened.
PERIBULBAR ANESTHESIA
In peribulbar block, the anesthetic agent is injected in the peribulbar space around the eye-ball. This drug gradually spreads inside the muscle cone.
Technique
- 25-mm, 24-guage needle
- 7–10 mL of anesthetic solution
- Two injections are given at the inferotemporal and superonasal quadrants:
- Inferotemporal injection (4–5 mL) is essentially the same as a retrobulbar block, except that the needle is not angled and is not moved centrally after passing the bulbar equator.
- The second superonasal injection is given just below the supraorbital notch which is identified by palpating the orbital rim.
- The needle is passed parallel to the orbital roof and the anesthetic solution injected in the peribulbar space.
Digital Massage after Block
- It is given with fingers of the hand, or with the application of a super pinkie.
- Intermittent massage with release of pressure every 30–45 seconds.
- It results in the following benefits:
- Decreases vitreous volume
- Decreases orbital volume
- Provides better akinesia and anesthesia
- Hemostasis within the orbit.
Complications are similar to retrobulbar block, but the incidence is less as compared to retrobulbar injection.
The disadvantage of a peribulbar block is an inferior quality anesthetic effect when compared to retrobulbar block.
SUB-TENON'S ANESTHESIA
Sub-Tenon's block involves injection of anesthetic agent below the Tenon's capsule around the globe.
Technique
- Instruments: Westcott's scissors, blunt cannula.
- 3–5 mL of anesthetic solution.
- The topical anesthetic drops are instilled.
- In the inferonasal quadrant, 7 mm from the limbus, a small conjunctival nick is made with Wescott scissors.
- The scissors is introduced in the sub-Tenon's plane and blunt dissection is done by the opening action of the scissors.
- A blunt cannula is introduced in this plane and 2.5–3 mL of anesthetic agent is injected.
Advantages
- Less chances of globe perforation
- Less chances of injury to optic nerve or muscles.
Disadvantages
- Poor akinesia compared to retrobulbar and peribulbar block
- Conjunctival chemosis and subconjunctival hemorrhage.
BRIDLE SUTURE
Bridle suture refers to a 5-0 silk suture passed beneath the insertion of superior rectus muscle. It facilitates downward rotation of the eye and increases exposure of superior surgical field. It also aids in the nucleus delivery with an irrigating wire vectis.
Technique
- Grasp the conjunctiva at 12 o'clock or 6 o'clock with fine-notched forceps and rotate the eye inferiorly.
- Grasp the superior rectus muscle at its insertion with a pair of toothed forceps and rotate the muscle toward 6 o'clock.
- Using a needle-holder, pass a 5-0 nylon suture through the conjunctiva and beneath the superior rectus muscle.
- Rotate the eye inferiorly to expose the superior limbus and clamp the suture to the eye drape.
CONJUNCTIVAL FLAP
We prefer a small fornix-based conjunctival flap from 11 o'clock to 2 o'clock position.
- Pick up the conjunctiva with fine, notched forceps at the temporal limbus (Fig. 1.2A).
- Make a small conjunctival nick with conjunctival scissors at 11 o'clock (Fig. 1.2B).
- Insert the scissors into the sub-Tenon's space with jaws closed and with the blades parallel to the limbus and bluntly dissect in the sub-Tenon's space.
- After this, insert one blade of the scissors into the space created and position the other on the conjunctival surface at the limbus.
- Cut both the conjunctiva and Tenon's capsule and continue until 2 o'clock is reached (Fig. 1.2C).
- Retract the conjunctival flap, exposing the sclera (Fig. 1.2D).
- Apply moderate-intensity cauterization to any bleeding vessels and vascular areas. Avoid excess cautery as it can cause shrinkage of scleral tissue and this increases the risk of postoperative astigmatism.
SCLEROCORNEAL TUNNEL CONSTRUCTION
The external incision of sclerocorneal tunnel is smaller in length as compared to the internal incision. This gives the tunnel a trapezoidal configuration.7 The scleral side-pockets allow for the accommodation of a large-sized nucleus. These features of the tunnel allow comfortable delivery of the largest sized nuclei.
Instruments: Toothed forceps, 15-number Bard Parker knife, bevel-up crescent knife, 2.8 mm bevel-down keratome.
Technique
The technique for the corneoscleral tunnel can be described under three main parts:
- External incision or scleral groove
- Construction of the tunnel
- Entry into the anterior chamber (AC).
External Incision
The various types of external incisions are:
- Smile incision: It follows the curvature of the limbus and is parallel to it. When made in superior quadrant, this induces against-the-rule astigmatism due to flattening effect on vertical meridian.
- Straight incision: It is a straight line and does not follow the curvature of the limbus. It has the advantage of inducing less astigmatism when compared to the smile incision.
- Frown/chevron incision: The major part of this incision lies in astigmatic neutral funnel. The ends of the incision are further away from the limbus than the ends of smile and straight incision. Due to these features, it induces least astigmatism.
Flowchart 1.1 exhibits the essential points which should be noted while placing the external incision.
We usually perform a frown incision 6–7 mm in size as it is an astigmatically stable incision. The size of 6–7 mm allows us to deal with almost all types of cataracts comfortably. The globe is stabilized by holding the limbus with the help of a toothed forceps. A frown incision is made in the superior quadrant, using a 15-number Bard-Parker knife. The features of this incision are:
- 1.5–2 mm from limbus
- 6–7 mm in length (Fig. 1.3)
- Depth should be one-third to one-half thickness of the sclera.
As frown incision is technically difficult to make, beginners can start with a straight tunnel incision first and then later shift to a frown-shaped incision.
Dissection of Sclerocorneal Pocket Tunnel
Once the external incision is made, dissection is extended anteriorly by a wriggling movement with a crescent knife lifting its heel and keeping the tip down till it reaches the limbus (Fig. 1.4A).
The curvature of the cornea is different from that of the sclera. At the limbus, the direction of movement of the crescent knife should be changed. The tip of the crescent is lifted up following the curvature of the cornea (Fig. 1.4B) and dissection is continued till 1.5–2 mm into the clear cornea.
With sideways-sweeping movements of the crescent, the dissection is extended on either side along the length of the incision (Figs. 1.4C and E).
Following points should be kept in mind during sideways dissection:
- Remain in the same plane.
- Follow the curvature of the cornea.
- Create a larger internal incision as compared to the external incision. This will give a funnel-shaped tunnel. For this, the crescent is swept about 45° sideways at the ends of the tunnels.
- At the ends of this internal lip, carry out the dissection in the sclera in an obliquely backward manner. This will create side-pockets (Figs. 1.4D and F). These side-pockets facilitate nucleus delivery out of the anterior chamber.
Internal Incision: Entry into the Anterior Chamber
Before entering into AC, one side port entry is made at the 9 o'clock position in the clear cornea just inside the limbus using a 15° blade. This 1.6-mm stab entry is done parallel to iris.
Through the side port, AC is filled with viscoelastics. A 2.8-mm angled keratome is introduced in the tunnel with a slight sideways movements taking care not to cut the floor or roof of the tunnel. The keratome is advanced till it reaches the inner end of the tunnel. At this point, the tip of the keratome is10 tilted down. This creates a dimple in the cornea (Fig. 1.5A). A gentle forward push results into AC entry (Fig. 1.5B). Care should be taken so as not to have a sudden jerky entry which may result in injury to the iris or lens capsule. After AC entry, the keratome is made straight and parallel to the plane of the tunnel. The internal incision is enlarged by forward and sideways movements of the keratome, taking care to cut only while going in. The movements of the keratome should respect the curvature of the cornea and limbus. At the ends of the tunnel, keratome is turned 45° sideways to accomplish the lateral ends (Figs. 1.5C and D).
The tissue should be cut only with forward movement of keratome, because cutting of tissue with backward movements creates an irregular internal wound that may cut across the limbus.
To stabilize the globe during tunnel construction, the lips of the tunnel should not be held as it damages the tunnel. The globe is stabilized by holding the limbus.
However, the temporal approach of the scleral tunnel is preferred in certain situations such as:
- Pre-existing against-the-rule astigmatism
- Superior filtering bleb
- Deep-seated eyes.
Technique: The technique is the same as described earlier but the dissection into the cornea should be more anterior to get a better self-sealing incision as the surgical limbus width is shorter in horizontal meridian.
Pearls and Pitfalls
- When we begin the sclerocorneal tunnel with a crescent knife, it is suggested that it should be started in the center of the groove as the depth in the center is adequate. The depth of groove may not be appropriate at its ends due to the hesitation while beginning it and haste to finish it.
- During sclerocorneal dissection, the blade should be “just visible” (Figs. 1.4A to F). The tunnel is superficial, if it is very clearly visible, and too deep, if hardly visible.
- A superficial external wound will cause buttonholing of the tunnel. In such cases, a new tunnel can be constructed at a deeper plane after deepening the incision.
- A deep external incision may cause premature entry. In such cases, dissection is done in a superficial plane. If a premature entry has happened, the wound should be sutured and the tunnel should be constructed at another site.
- A very deep external incision may cause scleral disinsertion. In this scenario, the wound should be sutured and the tunnel should be constructed at another site.
- A blunt keratome will require extra force for AC entry. This can cause Descemet's detachment or sudden jerky entry into AC, damaging the iris and the lens.
- The bleeding during tunnel construction stains the anterior end of the tunnel. This helps to identify the anterior end of tunnel during AC entry.
CAPSULAR OPENING
Instruments: A cystotome or Utrata forceps, toothed forceps.
Capsular opening is an important step of SICS because a good and an adequate capsular opening makes the subsequent steps easy. Three types of capsular openings that we commonly do depending upon the cases are: (1) continuous curvilinear capsulorhexis (CCC), (2) can-opener capsulotomy, and (3) envelope capsulotomy.
In absence of red reflex, as is the case with advanced cataracts, the visibility of the anterior capsule is poor. In such cases, making a good capsular opening becomes challenging. A compromised capsular opening makes the subsequent steps of the surgery difficult. To improve the visibility of capsule in such cases, the capsule is stained with the help of dyes. Various dyes that are commonly used include sodium fluorescein, indocyanin green, and trypan blue. Trypan blue is the preferred and most commonly used dye as it is cheap, does not stain the vitreous and endothelium, and is not endotheliotoxic.
The lens capsule is stained under air bubble. Through the side port, air is injected in AC. Under the air bubble, 0.1 mL of dye is injected over the anterior lens capsule. After 15–30 seconds, the dye is washed out of the AC. Viscoelastic is injected and the AC is formed.12
CAPSULORHEXIS
The technique of capsulorhexis was described by Gimbel and Neuhann independently.
The Japanese surgeon Shimizu called it circular capsulotomy.
Technique
A rhexis can be made by cystotome or Utrata forceps. A cystotome is prepared from a 26G needle by making two bends. The first one is a 90° bevel down-bend near the tip of the needle and the second one is an obtuse-angled bend near the hub of the needle, exactly opposite to the direction of the first bend. After filling the AC with viscoelastic, the sharp cutting tip of the cystotome is used to first make a radial incision over the anterior capsule starting from the center of the capsule (Fig. 1.6A). Then the cystotome is engaged under the capsule at the junction of outer one-third and inner two-thirds and pulled to raise a flap of the capsule. The tip of the cystotome is placed on the flap (Figs. 1.6B and C) and the flap is moved in an anticlockwise manner, 1–2 clock hours at a time. This way the cystotome and the flap are repositioned five to six times to create a capsular opening of the desired diameter. The point at which the capsule is grasped by the cystotome is always adjusted, so that it stays 2–3 clock hours away from the base of the flap (Figs. 1.6B and C). The size of the capsulorhexis is modified depending on the size of nucleus. Generally, a 6-mm rhexis suffices for most of the cases. At the end, the capsulorhexis should be completed by the outside-in movement of the flap.
While using Utrata forceps (Fig. 1.7), the flap is grasped near its base and advanced. The advantage with Utrata forceps is that it does not require support from the cortex below the capsule for the advancement of the flap. Therefore, it is usually employed in cases of hypermature or morgagnian cataract and for posterior capsulorhexis in pediatric cataract.
Pearls and Pitfalls
The flap should not be perforated and the underlying cortex should not be disturbed during capsulorhexis with cystotome.
- The anterior chamber must be maintained deep all the time because shallowing of AC may lead to run away and extension of capsulorhexis. In case of extension, it is managed by any of the following methods:
- Little's technique:9 Anterior chamber should be deepened by injecting viscoelastics. The capsular flap is unfolded and should lie flat over the lens. Then, holding the flap near its base with the forceps, it is pulled backward. This maneuver will re-direct the flap toward the center and then can proceed in the routine manner. If the capsule is not torn easily or the entire lens is pulled centrally, this technique should be stopped immediately to prevent wrap-around capsule tear.
- Alternatively, one can cut the capsule at the escape point using Vannas scissors and direct the opening back to the initial route.
- Another option is to raise another flap at the starting point of capsulorhexis and advance the flap in the opposite direction than that of the escaped flap and join them at the point of escape.
- The escaped capsulorhexis can also be managed by completing the remaining part of the rhexis in a can-opener fashion.
- If the capsulorhexis size is too small, it can be managed by:
- Multiple radial relaxing incisions
- Double capsulorhexis: A small nick is made with Vannas scissors at any site and a small flap is raised which is advanced with a Utrata forceps or cystotome.
- The nucleus can be managed by doing hydrodelineation so as to debulk the nucleus.
Advantages of Continuous Curvilinear Capsulorhexis
- Continuous curvilinear capsulorhexis can be stretched considerably limiting the risk of radial tears.
- It eases subsequent steps like hydrodissection, cortical aspiration, and in-the-bag intraocular lens (IOL) implantation.
- Helps in stability and centration of the IOL.
- In cases of posterior capsular rupture, the IOL can be placed over the rhexis with capture of optic in the CCC margin for better IOL centration.
Disadvantages of Continuous Curvilinear Capsulorhexis
- Requires more experience to master it adequately.
- Small CCC can prevent safe prolapse of the nucleus out of the capsular bag.
ENVELOPE TECHNIQUE
It was proposed by Sourdilla and Baikuff in 1979.10 A linear incision of 4–5 mm is made on the anterior capsule at the junction of the superior one-third and inferior two-thirds which is extended inferiorly on both sides by Vannas scissors and torn off with Utrata forceps.
Advantages
- Simple and efficient technique
- Can be done in cases of morgagnian cataract, intumescent cataract where CCC is difficult.
Disadvantages
- Risk of anterior capsular tear leading to PCR during forceful uncontrolled manipulation inside the AC.
- Incomplete overlap of IOL optic.
CAN-OPENER TECHNIQUE
The can-opener technique, though less commonly used in MSICS, can come handy in cases like hypermature cataract or intumescent cataract where15 making the rhexis is difficult, or in case of the extension of rhexis to complete the remaining part of the rhexis.
It involves placing multiple tiny cuts in the peripheral part of the capsule so as to create a capsular opening of desired diameter. The cuts are made from uncut to cut end on the capsule and joining them.
Advantages
- Precisely easier to master than CCC
- Can be sized properly depending on the hardness of the cataract.
Disadvantages
- The opening created has got irregular margins which carry the risk of tear during succeeding steps like hydroprocedures and nucleus prolapse.
- Cortex aspiration is challenging due to the presence of anterior capsular tags.
- Restricted opportunity for optic capture with sulcus placement.
HYDROPROCEDURES
Hydroprocedures were first described by Michael Blumenthal. Hydroprocedures separate different layers of the lens from the capsule (as in hydrodissection) or from each other (as in hydrodelineation) by creating a cleavage plane. This makes the nucleus and cortex management easier. It facilitates nucleus prolapse into AC and also facilitates cortex wash.
Thorough hydroprocedures play an important role in MSICS. Hydroprocedures comprise hydrodissection and hydrodelineation.
Hydrodissection
Hydrodissection refers to creating a cleavage plane between the anterior lens capsule and the cortical matter by a fluid wave. Conventional hydrodissection was done between the superficial cortex and the epinuclear sheet. Cortical cleaving hydrodissection refers to the separation of the cortex from the anterior lens capsule. It was first described by Howard and Fine.11 It has largely replaced conventional hydrodissection.
Before performing hydroprocedures, viscoelastic is washed out of AC. This prevents rise in pressure while doing hydroprocedures. An irrigating solution (Ringer lactate/BSS) is loaded in a 2-mL syringe. The smaller syringe has the advantage of better control while injecting the fluid. The tip of the cannula is introduced under the capsulorhexis margin. The rim is tented a little with the tip of the cannula and the cannula is advanced till it is halfway between the capsulorhexis margin and the equator. Tenting ensures that there is no layer of cortex between the anterior capsule and cortex and a slow and steady stream of fluid is injected to produce a fluid wave.16
This stream of fluid traverses under the capsular bag and separates it from the corticonuclear mass, thereby facilitating nuclear rotation and manipulation out of its bag. Signs that indicate that hydrodissection has happened:
- Visual confirmation of the fluid wave
- Shallowing of the AC.
Gentle taps on the central part of nucleus help to release the fluid behind the lens, complete the hydrodissection and deepen the AC. After successful hydrodissection, the nucleus is freely mobile and most of the time one pole of the nucleus will prolapse in the AC with the fluid wave (Fig. 1.8).
In cases with capsulorhexis extension, hydroprocedures should be performed carefully with minimal fluid.
Hydrodelineation
Hydrodelineation is also known as hydrodelamination/hydrodemarcation. In hydrodelineation, the cleavage plane is between the epinucleus and endonucleus. Hydrodissection causes separation of the lens matter from the capsule, whereas hydrodelineation results in debulking of the nucleus. The cannula tip is introduced in the lens matter and gently moved forward till the resistance of the central hard nucleus is felt. The cannula is withdrawn a little and the fluid is injected in small pulsed jerky doses. This will create a cleavage plane between the nucleus and the epinuclear sheet. The edge of the nucleus and the cleavage plane will be appreciated as a golden ring. The appearance of the golden ring indicates successful hydrodelineation. Soft cataracts may have multiple cleavage planes resulting in significant debulking of the nucleus. Hard cataracts may not have any cleavage plane.
Hydrodissection can be routinely done in all cases except for posterior polar cataracts and mature cataracts. Hydrodissection provides the ease of removing the nucleus, the epinuclear plate, and the cortical matter at one go. After cortical cleaving hydrodissection, there is hardly any cortex left for aspiration. Hydrodelineation is performed in posterior polar cataract cases as it provides epinuclear cushion.
Pearls and Pitfalls
There are certain points to remember while performing hydroprocedures.
- Any compromise in the rhexis warrants extra caution by avoiding hydroprolapse to prevent extension of the tear.
- Intermittent gentle taps at the center of the nucleus decompress the bag. Injection of excess fluid without decompression may cause PC to give away, resulting in PC rupture.
In posterior polar cataracts, hydrodissection is better avoided. It may result in PC rupture. In such cases, hydrodelineation is done. The epinucleus sheet between the cleavage plane and the PC will act as a cushion, increasing the safety of this procedure.
- Hydrodissection should be performed with care in cases where PC weakness/defect is anticipated (e.g. vitrectomized eyes, traumatic cataracts, and pseudoexfoliation).
- Hydroprocedures are not required for hypermature cataracts as the cortical matter is liquefied.
- Insufficient hydrodissection makes subsequent manipulation of the nucleus difficult and provokes excess strain on the bag and zonules.
NUCLEUS MANAGEMENT
Nucleus management consists of:
- Prolapse of nucleus into AC from the bag
- Delivering the nucleus out of the AC through the tunnel
Nucleus handling in absence of adequate hydroprocedures leads to excess stress on the zonular apparatus, which may lead to zonular dialysis. The completion of a successful hydroprocedure can be confirmed by rotating the nucleus in the bag with the tip of the hydro cannula or with a Sinskey hook. If the nucleus is not rotating freely, hydroprocedure must be repeated. Free rotation of the nucleus indicates that the nucleus is completely free from the bag and can now be maneuvered out of the bag.
Prolapsing the Nucleus in the Anterior Chamber
Hydroprolapse: At the end of hydrodissection, one of the poles of nucleus prolapses out of the capsular bag. The prerequisites for this to happen are adequate capsulorhexis size and good hydrodissection. The prolapsed pole is engaged with a Sinskey hook (Figs. 1.9A to D) and cartwheeled in a clockwise or anticlockwise manner. This will prolapse the nucleus out of the bag into the AC. If the nucleus pole does not prolapse out after hydroprocedures, it can be prolapsed using the bimanual technique.18
Bimanual Technique
The bimanual technique requires some degree of expertise and experience to practice. Fill the AC with viscoelastics. Introduce one Sinskey hook and a spatula into the AC through the main tunnel. Keeping the spatula near the rhexis margin at 3 o'clock or 9 o'clock, place the Sinskey hook at the center of the nucleus. Move the Sinskey hook radially (toward 3 o'clock or 9 o'clock) on the surface of the nucleus making a track on the nucleus till it goes 1 mm below the rhexis margin.
The nucleus is engaged with a Sinskey hook and pulled toward the center. This brings the equator of the lens near the capsulorhexis margin. At this point, a spatula is passed under the lens equator and it is nudged out of the capsular bag. Viscoelastic is injected above and below this prolapsed tip of the nucleus. It is supported by the spatula underneath it and cartwheeled out of the bag with the help of the Sinskey hook (Fig. 1.10). The bimanual technique is useful in cases with capsulorhexis extension and can-opener capsulotomy as it puts minimal stress on zonules.
Viscoprolapse
Viscoprolapse is similar to hydroprolapse. In this technique, viscoelastic is injected under the capsulorhexis margin.19
This creates a cleavage plane separating the lens matter from capsule and also prolapses the pole of the nucleus on the opposite side. This technique is useful for soft cataracts. Adequate size of capsulorhexis is an important prerequisite for this procedure.
Difficult Situations
- Hard-large nucleus (brown–black cataracts)—A larger capsulorhexis should be made and a bimanual prolapse as described above should be done in such cases. If the capsulorhexis is small, it can be enlarged or multiple relaxing incisions can be made.
- Hypermature cataract—A small, free-floating nucleus in the bag and absence of counter support makes the nucleus prolapse difficult in these cases. In such cases, after filling the AC with viscoelastics, the capsulorhexis margin is pressed with the visco-cannula as the viscoelastic is injected in the capsular bag. This will bring the small, free-floating nucleus into the AC.
Delivery of Nucleus
The nucleus can be delivered out of the AC by any one of the below-mentioned techniques:
- Irrigating vectis technique
- Phacosandwich technique
- Phacofracture technique
- Modified Blumenthal technique
- Fishhook technique
- Viscoexpression.
Irrigating Vectis Technique
This is the technique that we use in our hospital, the reason being that it is simple and can be done with the aid of a single instrument. Viscoelastic is injected first above the nucleus to protect the corneal endothelium and then below the nucleus to push the iris and bag down to prevent them from engaging in the vectis. An irrigating vectis mounted on a 5-cc syringe filled with BSS or RL is introduced in the AC under the nucleus to engage superior one-third to one-half part of the nucleus (Fig. 1.11). The vectis along with the nucleus is withdrawn back till the nucleus is engaged in the inner lip of the tunnel. Pull the bridle suture tight. Pressing the posterior lip of tunnel with the vectis, start injecting the fluid through the vectis and slowly bring the vectis along with nucleus out of the AC.
Pearls and Pitfalls
- If the nucleus is not engaging into the inner lip of the tunnel, reasons may be:
- Small, irregular tunnel
- Premature entry in the AC where the iris may plug the tunnel.
- In cases of a small tunnel, it must be enlarged. For this, AC is filled with viscoelastics. A 2.8-mm keratome is introduced in the tunnel and moved sideways, cutting the corneoscleral tissue following the three planar architecture of the tunnel and the curvature of the cornea.
- One should never struggle in a small tunnel and shallow AC as it causes damage to corneal endothelium.
- The size of the initial incision should be planned based on the size of the nucleus so as to facilitate the smooth passage of the nucleus through the tunnel and avoid undue struggle in nucleus delivery.
- In hard brown or mature cataracts, it is better to have a larger external incision with large side-pockets.
- The irrigating vectis should not be introduced more than half way through the nucleus as it may catch the iris or posterior capsule during delivery leading to iridodialysis or a posterior capsular rent.
- In cases of soft cataract, the vectis is visible under the nucleus while it may not be distinctly visible in harder cataracts (Fig. 1.12). Hence, adequate care should be taken during delivery of such cases.
CORTEX ASPIRATION
A thorough cortex clean-up is a must to prevent the occurrence of postoperative iritis, PCO formation, and cystoid macular edema. After a good cortical cleaving hydrodissection, very minimum cortex is left which is aspirated with Simcoe's cannula.
The structure of cortical matter comprises an anterior leaf underneath the rhexis margin and a posterior leaf oriented along the posterior capsule. The body of the cortical matter lies in the fornix of the bag. The basic principle of the cortex removal is to engage the anterior leaf using the aspiration force and use it to peel the body and posterior leaf from the capsule. This is accomplished using Simcoe's cannula. The anterior leaf is engaged in the tip of the cannula; with gentle side-to-side movements and pulling movements, the cortex is loosened and stripped off from the capsule.
The cortical matter should be approached in a systemic manner.
- Inferior three to four clock hours of cortex is approached from the main tunnel. It is removed first.
- The area opposite to the side port (2–5 o'clock area for side port at 8–9 o'clock) should be approached through the side port.
- The cortical matter under the side port is approached through the main tunnel.
- The subincisional cortex is approached through the side port (Fig. 1.13).
Difficult Situations
Subincisional Cortex
- The subincisional cortex is commonly removed through the side port.
- The other option is to use specially designed cannulas—“J” or “U” cannula.
- Minimal residual cortex can be removed after IOL implantation by rotating the lens in the bag.
Small Pupil
Pupil may constrict after nucleus removal. The common reason for this is the shallowing of the AC and hypotony. Injecting the viscoelastics will reform the AC and dilate the pupil to some extent. One may inject adrenaline in the AC to dilate a very small pupil. To prevent shallowing of the AC, care should be taken so as not to press the posterior lip of the tunnel. The Simcoe cannula should slightly lift the anterior lip of the tunnel. This will keep the AC well-formed and prevent AC shallowing.
Pseudoexfoliation Syndrome
The deposition of pseudoexfoliative material weakens the zonules, making these eyes more prone to zonular dialysis. Following care should be taken in such cases:
- The anterior chamber should be well-maintained throughout the surgery.
- The nucleus should be prolapsed using the bimanual technique, exerting minimal stress on the zonules.
- The direction of stripping the cortical matter from the lens capsule should be tangential/circumferential. The radial pull will cause zonular dialysis.
Positive Pressure
Positive ocular pressure during cortical aspiration increases the chances of PC rupture. In such cases, the underlying reason for positive pressure should be identified and addressed. Some of the reasons include:
- Valsalva maneuver due to pain
- Tight lid speculum
- Injection of an excessive quantity of anesthetic drug for peribulbar/retrobulbar block
- Obese patients.
In such cases, most of cortical matter should be removed through the side port. The use of the main port will cause shallowing of the AC and bulging of the PC forward, increasing the risk of PC rupture. The other option is to inject viscoelastics, which will form the AC and push the PC back. Then the cortex should be removed by dry aspiration (aspiration without switching on the irrigation).
Traumatic Cataract
Traumatic cataract can often be associated with PC rupture or zonular dialysis. In cases with PC rupture, the cortex should be removed by dry aspiration after injection of viscoelastics in the AC. In cases with suspected zonular weakness or zonular dialysis, the cortex should be removed by tangential pulling. Radial pull is best avoided.
Posterior Capsular Rupture
The key to good outcome in cases with PC rupture is early identification. After PC rupture is noted, the AC is filled with viscoelastics. The cortical matter is removed using dry aspiration. Automated vitrectomy is performed to remove vitreous from the AC.
Pearls and Pitfalls
- Cortex aspiration should be performed with utmost care in cases with rhexis extension or capsular tags. Caution should be exercised to not engage the tags in the tip of the cannula.
INTRAOCULAR LENS IMPLANTATION
The commonly used IOL with MSICS is rigid PMMA IOL with 6 mm optic size. For IOL implantation, the AC is filled with viscoelastics and the bag is inflated with viscoelastics. The lens is held longitudinally, using a McPherson forceps or a lens-holding forceps. The IOL is introduced into the AC and advanced forward till the leading haptic reaches the inferior capsulorhexis margin (near the 6 o'clock position). Then, the IOL is tilted downward by lifting the trailing haptic near the tunnel and gently pushed forward. This will cause the leading haptic to pass under the capsulorhexis margin and go into the capsular bag. Once the leading haptic is inside the bag, the IOL is released and the forceps withdrawn. Then, the positioning hole is engaged with a Sinskey hook and the IOL is rotated in a clockwise direction with a simultaneous downward push till the trailing haptic slips into the bag (Figs. 1.14A to F).
The correct implantation of IOL in the bag can be confirmed by the appearance of a “‘stretch line” in the posterior capsule caused by the tips of both haptics resting on posterior capsule (Fig. 1.15).
The viscoelastic is washed out of the AC and capsular bag. The side port is hydrated. Due to the self-sealing nature of the tunnel, sutures are not required. The adequacy of the closure is checked by a gentle tap on the cornea to check for wound leak. The conjunctiva is closed by cautery (Fig. 1.16).
WOUND CLOSURE
A well-constructed SICS tunnel of size less than 7 mm does not require sutures. The tunnel may require sutures in cases with premature entry, buttonholing, leaking tunnel, and positive pressure. High myopes and pediatric patients have thin sclera with low scleral rigidity, which may require tunnel suturing. The tunnel should be closed with either vertical interrupted sutures or infinity suture.
PRE- AND POSTOPERATIVE MEDICATIONS
Preoperatively, as a routine we start topical antibiotics on the day before surgery eight times and nonsteroidal anti-inflammatory drug (NSAID) eye drops four times a day.
In cases with intumescent cataract or cases with a low axial length, shallow AC, where a positive vitreous pressure is anticipated intraoperatively, we give 30 cc oral glycerol 15–20 minutes before surgery.25
Uveitic cataracts are done under the cover of corticosteroids. The cases with a history of viral keratitis or keratouveitis are done under the cover of antivirals.
Postoperatively, as a routine we prescribe a topical steroid-antibiotics combination starting from five times a day, tapered every 10 days over a period of 6 weeks. Along with this combination, topical NSAIDs are also prescribed to reduce the chances of postoperative CME. The cases with PCR or vitreous disturbance are also given oral fluoroquinolones for 5 days.
REFERENCES
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- Venkatesh R, Tan CSH, Singh GP, et al. Safety and efficacy of manual small incision cataract surgery for brunescent and black cataracts. Eye. 2009;23:1155–7.
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- Basti S, Vasavada A, Thomas R, et al. Extracapsular cataract surgery: Surgical techniques. Indian J Ophthalmol. 1993;41(4):195–210.
- Fine IH. Cortical cleaving hydrodissection. J Cataract Refract Surg. 1992;18(5): 508–12.