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

many research workers all over the globe. Kamman and Cumming have modifed the traditional plate haptic silicon IOL to allow for movement of the IOL within the capsular bag after insertion. This intriguing design has demonstrated initial success in restoring presbyopic accommodation. Accommodative amplitudes of approximately 2 to 3 diopters have been observed. However, long-term studies have to be done before the clinical efficacy of these lenses is established.

TORIC INTRAOCULAR LENSES

The plate haptic IOL design has been modified to produce a toric IOL with the correction cylinder added along the long axis of the IOL. This is marked on the surface of the lens optic. For the toric design to be effective, the lens should not rotate within the eye after implantation. Rotation is relatively unusual but can occur during the first 4 to 6 weeks after implantation, prior to fibrosis around the lens and through the large positioning holes. After this 4 to 6-week period the lens fixates in the capsular bag via the fibrosis through the positioning holes and fusion of the anterior and posterior capsules. This helps to prevent long-term rotation as well as decentration and dislocation of the IOL.

PIGGYBACK INTRAOCULAR LENSES

This concept involves the use of two intraocular lenses placed one on top of the other (piggyback). This may be done as a primary procedure to obtain an optimal refractive result in highly ametropic eyes (e.g. high hypermetropia) where sufficiently high power in a single IOL may not be available. The second IOL can also be implanted at a later date as a secondary procedure to correct for a poor refractive result of the previous cataract surgery. Both the lenses can be placed in the capsular bag or one can be placed in the bag and the second IOL in the ciliary sulcus. The main complication with use of piggyback lenses is interlenticular opacification or interpseudophakic opacification of polypseudophakia (opacification between the two IOLs) which may require both IOLs to be explanted.

COMPLICATIONS OF

FOLDABLE INTRAOCULAR LENSES

Descemet’s Membrane Detachment Caused by IOL during Insertion

When inserting an IOL the lower edge of the optic can cause a Descemet’s membrane detachment. This

Descemet’s membrane detachment is likely to occur if IOL is inserted just parallel to the scleral tunnel incision and where a detached scroll of membrane is already present. In such cases the membrane can be repositioned through the injection of air or expanding gas into the anterior chamber.

Posterior Capsular Rupture during IOL Insertion

The posterior capsule can be ruptured during IOL insertion and a if there is a pre-existing tear in the posterior capsule, it can extend. Such a complication can occur if adequate quantity of viscoelastic has not been inserted in the bag or there is considerable leakage of viscoelastic substance during IOL insertion. The use of a passport system with plate haptic lenses is more likely to cause this problem. If there is a tear in the posterior capsule prior to IOL insertion, the injector/passport system should not be used at all. If a tear occurs during IOL insertion, the IOL may be left in the bag if the tear is small and the viscoelastic removed manually with a Simcoe cannula or using bimanual irrigation-aspiration. However if there is a large tear then the IOL should be placed on the margin of the capsulorhexis.

IOL Damage during Insertion

The haptics may be damaged during IOL insertion through a small wound and one of the haptics may be broken. In such cases it is essential to remove and replace the IOL. During insertion care should be taken to adequately extend the incision so as not to force the IOL through a small and tight wound. Special caution is warranted when a high power IOL is injected. Use of a wrong forceps for holding the IOL may cause compression marks on the IOL optic and may even crack the IOL requiring explantation of the IOL.

Bag Sulcus Fixation

During insertion of the IOL, the lower haptic may be placed in the bag and the upper haptic may lie in the ciliary sulcus. This can lead to IOL decentration and the haptic may also cause a chronic uveitis/pigment dispersion by rubbing on the iris tissue. Asymmetric loop placement can also cause the windshield wiper syndrome with the superior loop and optic shifting position with eye movements and causing damage to the corneal endothelium. To avoid this complication the upper loop of the IOL should be carefully dialed in the bag and the surgeon should check that both haptics are in the bag before concluding the surgery.

Capsular Bag Distension Syndrome

This problem arises when a small capsulorhexis completely covers the optic and thereby seals the capsular bag. There is sequestration of fluid secreted from the remnant epithelial cells within the capsular bag and a progressive inflation of the capsular bag. Retained viscoelastic material behind the IOL can also lead to this condition by creating an osmotic gradient and drawing more fluid from across the capsule. This creates to an anterior shift of the IOL and progressive myopia. The condition can be prevented by performing a large capsulorhexis. The treatment of this capsular distension syndrome is done by doing a Nd-YAG laser capsulotomy of the anterior capsule. A nick is created at the edge of the capsulorhexis at 2/3rd locations, which allows fluid trapped within the capsular bag to escape into the anterior chamber.

IOL Decentration

Implanting a small diameter IOL (which is meant to go in the capsular bag) in the ciliary sulcus can lead to a severe decentration of the IOL. This is especially seen when a rent in the posterior capsule occurs and the small diameter IOL is placed over the margin of the capsulorhexis by the surgeon. It is important to remember that plate haptic lenses which do not have open loops should never be placed over the capsulorhexis. The surgeon should always have a large diameter (6.5 mm optic, overall diameter 13 mm) IOL available for implanting in the ciliary sulcus in the event of a large posterior capsular rupture. In cases of zonular dehiscence, a PMMA endocapsular ring should be implanted within the capsular bag and then the IOL inserted, to prevent decentration of the IOL.

Lens Dislocation

Complete lens dislocation into the vitreous is a rare complication. It may occur due to the presence of an unrecognized zonular dialysis during surgery or the presence of pre-existing zonular deficiency such as in posttraumatic eyes or eyes that have undergone previous vitreoretinal surgery. Such a complication has also been reported after YAG capsulotomy, especially with plate haptic lenses. A pars plana vitrectomy is necessary for removal of lenses dislocated into the vitreous and the intraocular lens may then be repositioned with iris or scleral suturing or substituted with an anterior chamber IOL.

Silicone Oil Adherence to IOL

Irreversible silicone oil adhesion to the optic of a silicone foldable IOL may occur during vitreoretinal surgery. The silicone oil droplets condense on to the optic of the IOL and lead to a severe degradation of the optics of the IOL. This condition can be avoided by not implanting silicone IOLs in eyes with present or potential vitreoretinal disease.

Capsular Contracture Syndrome

The anterior capsulorhexis can undergo a progressive contracture leading to a capsular phimosis with obscuration of the visual axis and decentration of the IOL. This occurs due to a fibrous metaplasia of the residual lens epithelial cells and is aggravated if the original capsulorhexis is small. This complication is most frequently seen with the silicone plate haptic lenses. The contracture can be relieved by performing a YAG capsulotomy at the margin of the anterior capsule.

Uveitis

Polypropylene haptics can activate complement and induce white cell chemotaxis and thus incite an inflammatory reaction. IOLs with polypropylene haptics are also a risk factor for endophthalmitis with a risk 4 ½ times that of all PMMA posterior chamber lenses.

Endophthalmitis

Delayed onset endophthalmitis, which has a delayed onset and an indolent course, has been described in eyes with intraocular lenses. The most common responsible organism is Staphylococcus epidermidis. A more indolent from caused by Propionibacterium acnes may present as chronic granulomatous uveitis with white plaques on the posterior capsule. This infection appears to be enhanced by localized entrapment of organisms within the capsule and has been reported only in eyes with intraocular lenses. Adherence of organisms to lenses may play some role. If Propionibacterium is suspected vancomycin is the treatment of choice, although some cases may not respond to medical management and require an IOL explantation with excision of the involved capsule.

IOL Discolouration

IOL discolouration has been reported with the first generation silicone IOLs. The discolouration of the optic varies from light tan to a brown colour and appears from

15 months to 5 years after implantation. It can also be seen in the IOLs in vitro if the lenses have not been used for a long time. Although this colouration does not affect the visual acuity, it can cause a fall in the contrast sensitivity.

IOL Glistenings

This complication has been reported with the AcrySof IOL especially if AcryPak packaging has been used instead of the traditional wagon wheel packaging. These glistenings are basically microvacuole formation within the lens optic and are influenced by temperature changes. This can cause a significant decrease in the contrast sensitivity and induce glare.

Glare

Use of small optics (<5.5 mm) can cause an edge glare, especially during conditions of decreased illumination, which cause a pupillary dilatation. This is a serious problem with square edge lenses such as the AcrySof with a 5.5 mm optic. It can cause a significant visual disability to the patients, especially during night driving. A trial of 0.5-1 per cent pilocarpine may be done to decrease the symptoms in such patients, although the IOL may even have to be explanted due to this problem.

Posterior Capsule Opacification

Posterior capsular opacification (PCO) is currently the most important issue in modern day cataract surgery. Residual lens epithelial cells at the equator and the anterior capsule proliferate and cause an opacification of the posterior capsule after cataract surgery. This leads to a decrease in the visual acuity, contrast sensitivity and causes glare. Silicone and PMMA lenses have higher rates of PCO as compared to acrylic lenses. A YAG laser capsulotomy has to be performed in such cases but it can cause damage to the optic of the IOL and opening up of the posterior capsule increases the risk of a subsequent retinal detachment. PCO can be reduced by the following factors:

1.Adequate hydrodissection for facilitating a complete cortical clean up.

2.An in-the-bag fixation of the IOL.

3.Diameter of the capsulorhexis slightly smaller than the optic (seals the bag).

4.High biocompatibility of the IOL.

5.Maximal IOL optic-posterior capsule contact.

6.Square truncated edge of the IOL optic.

7.Primary posterior capsulorhexis with optic capture in pediatric cases.

It is a foregone conclusion that, if the surgery has been uneventful till this stage, there are unlikely to be many hiccups on your way to successfully completing sutureless cataract extraction with IOL implantation. Probably that is why there is so little literature available

on techniques of IOL implantation.

Nevertheless, a few pertinent points need to be elicited here, for the benefit of the beginner, or for those converting from conventional ECCE to SICS.

The peculiarities of IOL implantation in SICS arise out of the specific nature of the passageway. At 3.5 to 4.5 mm, the sclerocorneal tunnel of SICS is the longest passageway the IOL must traverse before being implanted. By comparison, the passageway in conventional ECCE is barely 1.5 mm, and even the clear corneal tunnel, favoured by today’s phaco surgeons, is a mere 2 to 2.5 mm (Fig. 29.1). Also, the SICS tunnel traverses two different tissues, the sclera, and the cornea. Therefore, certain differences exist in the technique of implantation of the IOL in SICS, vis a vis the conventional ECCE, or the phacoemulsification.

Fig. 29.1: Comeoscleral tunnel for SICS

Within the SICS also, there are some subtle differences. While most of the SICS techniques involve the use of viscoelastics, the Blumenthal technique (my technique of choice) uses BSS itself to keep the AC formed for implantation. This gives rise to another set of problems which unfold as you proceed with implantation. As the IOL is pushed through the tunnel, due to positive pressure in the AC, the leading haptic tends to bend strongly. On entering the AC, this haptic springs free suddenly. At this stage, the AC tends to become shallow, with the escaping of the BSS. So if you continue pushing the IOL, you may be trying to introduce it into the bag when the posterior capsule may be convex, and not concave. The consequences are well-imaginable. Even with the IOL in the AC, and the leading haptic in the bag, introducing any instrument through the tunnel to manipulate the upper haptic into the bag also results in a shallowing of the AC. Though mostly harmless, this is alarming enough to induce tachycardia in the surgeon.

After 4 incidents of near disaster, I changed my technique of IOL implantation, from Push and Dial, to Pull and Dial. This has saved me from many an anxious moment since then. I will now describe both the techniques, step by step.

The Technique

Step 1

This will apply to those SICS techniques where viscoelastic is used. Fill the AC and the capsular bag with visco. Preferably, introduce your visco cannula through the main tunnel, and not the side port. Keep injecting visco as you withdraw your cannula after filling the AC and the bag. Make sure that you inject some visco in the tunnel also. This will keep the tunnel slightly gaping, as well as act as a lubricant for the passage of a rigid IOL.

Step 2

Here it is presumed that rigid IOLs are being used. The use of foldable IOLs in SICS is unnecessary and unwarranted, since the tunnel is at least 5.5 mm wide, and can accommodate most of the rigid lenses.

Hold the IOL with McPherson’s forceps near the upper dialing hole. Alternatively, the vertical Daljeet Singh IOL forceps could be used to grasp the lens longitudinally. This would be useful for the push and dial, but not for the pull and dial technique.

Step 3

Push and Dial Introduce the leading haptic into the tunnel. As you see the leading haptic enter the AC, tilt the lens downwards so that the haptic is directed towards the six O’clock pole. Keep pushing the lens till the leading haptic is completely in the bag, and the lower dialing hole is also at the pupillary border at six O’clock. Gently release the IOL and withdraw the forceps. You may now introduce the Sinskey hook from the side port, or the main tunnel, and dial the IOL into the bag. Alternatively, you may grasp the upper haptic with McPherson’s forceps, and rotate the lens as you tuck the upper haptic under the edge of the capsule or the pupillary border. At any stage, if the AC becomes shallow, cease, and reform the AC with more viscoelastic. Once the IOL is in place and well-centered, removing the viscoelastic, and corneal hydration of the sideports if any, will complete the last steps of a successful SICS.

Step 4

Pull and Dial This is an excellent procedure for the Blumenthal technique where hydrostatic pressure is used to form the AC and fill the capsular bag for implantation. When you start implanting, the tunnel is tightly closed due to the BSS flowing into the AC through the Anterior Chamber Maintainer. Hence the leading haptic bends dangerously (and may even break!) when you push the IOL into the tunnel. As the lens enters the AC and you keep pushing the lens, the haptic suddenly springs free. This is accompanied by a slight shallowing of the AC as the BSS gushes out of the tunnel. Push the IOL a little more till the main body of the lens is blocking the tunnel, and the gush of BSS diminishes. As you now release the IOL from the McPherson’s forceps, use the other hand with a plane micro-forceps, to hold the upper haptic and to tilt the lens slightly downwards. Now introduce a

Sinskey hook from the side port with your first hand. The lower dialing hole should be visible at the internal (corneal) incision. Engage this hole with the hook and drag or pull the lens into the AC, directing the lower haptic into the bag at six O’clock (Fig. 29.2). The upper haptic may sometimes tend to snag in the tunnel at this stage, but can be easily guided with the plane forceps in the other hand. When the leading haptic is safely in the bag, you may disengage the Sinskey hook from the lower dialing hole and engage it in the upper dialing hole (Fig. 29.3). By this time, the entire IOL is in the AC, and the tunnel is sealed, giving you a deep AC. You can now easily dial the upper haptic into the bag.

Fig. 29.2: Implantation technique

CONCLUSION

This modification of the technique for Blumenthal becomes necessary as the AC shallows as soon as you introduce any instrument or the IOL through the tunnel into the AC. If you try to introduce much of the IOL into the AC as you did in the Push and Dial technique, the risk of traumatizing the posterior capsule or the corneal endothelium is high. Hence it is better to Pull and Dial, rather than Push and Dial, for the Blumenthal technique.

Fig. 29.3: Implantation technique drawing the lens downwards from upper hole

CARE TO BE TAKEN

For any SICS procedure, a good and clean tunnel is an absolute must. The importance of using a sharp (or new) crescent knife for each case cannot be overemphasised.

An uneven tunnel, or a rough floor of the tunnel, can cause much difficulty, particularly in the implantation of the IOL.

At no stage should you try to continue pushing the IOL if the AC has shallowed. You must cease, but need not withdraw the IOL. Rather, deepen the chamber by pushing more viscoelastic from the side port, over the IOL. Then you can carry on from where you left the IOL.

The dictum ‘Better Safe Than Sorry’ would be a useful one to memorise and recall.

REFERENCES

1.Thomas R, Kuriakose T, George R: Efficient small-incision cataract surgery, Indian J Ophthalmol 48: 145-51, 2000.

2.Blumenthal M, Askenazi I, Fogel R et al: The Gliding Nucleus,

J Cataract Refract Surg 19: 435-37, 1993.

3.Lahane TP: The incision-structural principles, Opthalmology Today 2: 93-95, 2001.

4.Blumenthal M: Surgical principles and techniques for small incision ECCE. Mini Highlights of Ophthalmology 21: 5(1- 8), 1993.

ClosureWound 30

MP Tandon

TN Vyas

The main function of a tunnel incision is to provide watertight self-sealing valved wound. By pressing against the dome of cornea and on the limbus one can check the integrity of wound. Sealing can be

done by hydration of corneal stroma, which is achieved by injecting irrigating fluid into the external tip of the side port wound. The integrity is tested by applying pressure with a sponge against the posterior lip of the wound to make the incision leak. In the absence of leak, the incision is covered with the conjunctival flap.Suturing is required if:

a.There is a leaking tunnel.

b.Tunnel is more than 6.5 mm in length, even if it is self-sealing in order to avoid against the rule astigmatism.

c.Premature entry.

d.Triple procedure has been done.

e.Paediatric cataract (due to thin sclera). Suturing techniques can be divided into:

1.Appositional/Radial/Vertical sutures.

2.Horizontal.

Both can be either interrupted, figure of eight or conti-

nuous. Interrupted sutures give better control through individual suture cutting while continuous suture equalises the tension across the wound.

Vertical Sutures

They appose the external lip of the wound, which results in internal separation of the corneal lip because of pulling of the sclera and cornea. They are separated by the normal physiological gape, and this pulling of external wound creates a new un-physiological position. The internal entry site, which is the true astigmatism control site is separated and disturbed. This can be reduced by taking deep bites in the scleral bed, which brings proper apposition of the scleral bed to the superficial flap.

Horizontal Sutures

They are less likely to disturb the alignment of internal entry incision so as to cause less astigmatism than radial sutures. They make the incision watertight by flattening the scleral tunnel types of horizontal sutures.

1.Shepherd’s single horizontal suture This suture was introduced by shepherd primarily for closure of scleral tunnel of 5 mm width, which were weak. This consists of a single bite starting at one end of the wound entering the roof and floor of pocket vertically, passing it horizontally to the other end along the floor of the pocket and then bringing it externally through the roof of the pocket on the other side of the tunnel. The externalised sutures are then tied, thus closing the incision. But this technique was not appropriate for longer incisions, besides it resulted in an externalised knot, and passage of suture through the deep layer of the scleral pocket cannot be seen (Figs 30.1a to e).

Fig. 30.1a: Enter roof and floor of the pocket vertically at one end

2.Horizontal anchor suture was introduced by Masket for incisions between 4.0 to 7.0 mm in length to allow direct visualisation of the horizontal suture within the

Fig. 30.1c: Bring out the suture through the roof of pocket on the other end and tie it

deep layer of scleral pocket. It also had the advantage to close the incisional “Dead space”, to prevent internal wound gape and “fish-mouthing”, to bury the knot within the pocket, to provide a central “anchor” against

Figs 30.1d and e: The suture being tied closes the incision

anterior placement of the external layer of the scleral pocket and the induction of an “against-the-rule” astigmatic change (Figs 30.2a to h).

The technique consists of applying the suture in the deep bed of the pocket with a miniradial bite taken towards the cornea and externalised through the outer layer of the pocket. The suture then passed horizontally to the right extreme of the pocket and pierced through the outer layer or roof of the pocket to enter the wound space. The horizontal or circumferential portion of suture continued from right to left under direct visualisation in two bites, creating a safety loop over the initial mini-radial pass. The extreme left of the deep layer or floor of the pocket is reached, the suture then brought externally and carried to the centre of the incision where it was passed through the roof of the pocket into the floor of the bed under the safety loop, matching the original mini-radial bite and completing the suture course. The knot is buried within the scleral pocket to prevent conjunctival irritation.

Fines Infinity Sutures

Resembles mathematical symbol for infinity in cross section. It was introduced for closure of tunnel of 6.5 mm. It consists of two loops each covering approximately 40 per cent of tunnel width. The first loop enters the wound space through the roof, pierces the floor of the pocket and is their passed horizontally along the floor of the pocket. It thin exits just left of the midline, through the roof in the pocket. The second loop is similarly made at the other end of the incision, again exiting just right to the midline. The two ends of the sutures are tied externally closing the incision (Figs 30.3a to i).

Fig. 30.2h: The knot is burried in the scleral pocket, preventing conjunctival irritation

Fig. 30.3a: Enter the tunnel through the roof

Fig. 30.3b: Pass the suture horizontally along the floor of tunnel and take it out just to the other side of midline

Fig. 30.3e: Run the suture along the floor of tunnel and take out just beyond the midline

Alternatively the second bite of the suture can be taken with the second needle of a double-armed suture, just to the right of the exit point of the first bite and advancing the needle from right to left.

Figs 30.3h and i: In cross-section this suture resembles the mathematical symbol for infinity