Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001

PHACOEMULSIFICATION IN DIFFICULT CASES 233

Fig. 22.18: Use of Kuglein hooks to enlarge small pupil

Another method of judging where the tear is occurring behind the pupil is to use a collar-stud button or a Kuglein hook to stretch the pupil in the quadrant of the advancing tear. It is important that the tear is not made excessively large and, in fact, it is prudent to make the initial capsulorrhexis smaller than one would ideally want to in a large pupil phacoemulsification.

A secondary capsulorrhexis can be done if the original size of the capsulotomy was too small. This can be achieved by making a snip on the edge of one side of the capsulorrhexis and using a capsulorrhexis forceps to tear off a ribbon of the capsule, enlarging the opening of the capsulorrhexis.

If too small a capsulorrhexis is made

it can end up postoperatively with a small fibrosed capsular opening. This can lead to subluxation of the IOL. This problem is most evident in cases of pseudoexfoliation (Fig. 22.20).

234 THE ART OF PHACOEMULSIFICATION

Fig. 22.20: Excessively small CCC causing capsular phimosis and contraction

Hydrodissection

Hydrodissection is possibly one of the most important steps in the entire procedure as unless the nucleus is easily rotatable the rest of the phacoemulsification becomes virtually impossible. This is particularly true in small pupil phacoemulsification where the quadrants have to be manipulated to a zone which is not only safe but easily visible.

Hydrodissection would be noted to be complete once there is anterior movement of the lens-iris-diaphragm with egress of viscoelastic. There is enlargement of the pupil with this maneuver. If necessary, it is important that the rotation of the lens is checked using two hooks prior to the insertion of the phacoemulsification tip.

Phacoemulsification

As discussed earlier, it is important that safe, repeatable maneuver for phacoemulsification is used. It is recommended that a form of split and lift technique be used where the nucleus is divided into four quadrants and each apex of the quadrant is then lifted in the central safe zone of the pupil for phacoemulsification.

Cortical Clean-up

Cortical clean-up using an irrigation/aspiration cannula is undertaken. It is important that the port of the cannula be always visible to the surgeon. The cannula must be placed deep in the capsular bag to prevent any incarceration of the iris. To deepen the capsular bag it may be necessary to raise the height of the irrigating solution bottle.

PHACOEMULSIFICATION IN DIFFICULT CASES 235

The individual quadrants of the pupils can be retracted using a second instrument and the cortex grasped with the cannula and aspirated once the cannula is brought into view within the pupillary area. The port of the cannula must be rotated superiorly before full aspiration is undertaken.

The most difficult area to remove cortex, especially in small pupils, is the subincisional cortex. The problems include overhanging of the pupillary margin and the anterior capsulotomy edge. A two-instrument technique is used here whereby

a 90 degree curved I/A cannula (Alcon, Fortworth, Texas) is used with retraction of the iris superiorly using a second instrument (e.g. Kuglein hook). It is important

that the anterior chamber, especially the capsular bag, is kept well inflated in order the 90 degree I/A tip clears both the pupil and the anterior capsular edge before any aspiration is actually done of the subincisional cortex (Fig. 22.21).

Fig. 22.21: Varieties of I/A tips. Angled 90o tip is useful for subincisional cortical removal

A second method is to use an aspiration cannula through the side port incision and irrigating cannula placed in the cataract incision.

Postoperatively the stretched pupil appears round and is cosmetically very acceptable. It is only with magnification can notches on the pupillary margin be seen.

The added advantage of this technique is that most of these pupils are still functioning pupils (Fig. 22.22).

Discussion

There is no doubt that a small pupil presents a significant challenge to the cataract surgeon. Phacoemulsification is probably the method of choice in dealing with patients with small pupils. It is imperative that any pupil measuring less than 3 mm would require some pupil enlarging surgery. However, this can be minimized by using the pupil stretch technique or some modification of that method. This enables the phacoemulsification to be done in the bag and the IOL inserted well within the bag and minimal postoperative complications with glare and with an acceptable cosmetic result and a round pupil.

Technique

The first problem the surgeon is going to meet is a poor red reflex, particularly if the eye is darkly pigmented. The anterior capsule is very thin and atrophic and is likely to be on a stretch which can lead to the capsular tear running out to the periphery of the capsular bag. It is imperative that the anterior chamber is kept deep all the time and a retentive viscoelastic that is going to allow a smooth capsulorrhexis but at the same time being retentive has to be used. A

combination viscoelastic is probably the best in this sort of situation, e.g. Duovisc (Alcon, Fortworth, Texas).

In most instances it is possible with minor movements of the eye to view the edge of the capsulorrhexis tear as it is reflected by the microscope light. In some situations staining techniques of the capsule may be required and this will be discussed in further detail when white cataract phacoemulsification is discussed. It is important that a sufficiently large capsulorrhexis is made in order that the phacoemulsification tip does not inadvertently hit the capsular edge.

The best phacoemulsification technique is still some form of divide and conquer, preferably dividing the lens into four quadrants and then engaging the apex of each quadrant and phacoemulsifying the quadrants deep in the capsular bag furthest away from the corneal endothelium. A phaco-chop maneuver of each quadrant can also be combined with this technique. Once the nucleus is cracked it allows easier access to each quadrant to carry out the phaco-chop. A 45-degree tip is used as it gives much better cutting power. It is important not to move the dense hard nucleus excessively and thus to minimize the movement, a shaving maneuver is used with the phacoemulsification tip. It is not advisable to engage the nucleus in any large chunk but to gradually trench the nucleus by shaving the surface and going deeper in that manner. It is important to be very patient in this technique as it will take time to achieve a deep enough trench. The depth of the trench can be judged by a white leathery reflex from the thick cortical plate. Once this reflex is obtained, cracking of the nucleus can then be undertaken. It is important also that when the cracking is done that all fibrotic bridges between the pieces are also broken. Any fibrotic bridge left will make it extremely difficult to manipulate the quadrants into the phacoemulsification tip. For further protection of the capsule it is possible to use viscoelastic as a pseudocortex and by injecting viscoelastic between the nucleus and the posterior capsule (Fig. 22.24).

There should be free usage of the second instrument to stabilize the nucleus and the nuclear fragments in quadrants to prevent tumbling which might not only rupture the posterior capsule but also cause traumatic injury to the corneal endothelium.

MATURE WHITE CATARACT

The problem the surgeon faces in this sort of situation is that the white fluffy cortex obscures a clear view of the capsule. The capsule itself is thin and stretched and it is usually difficult to tell what type of nucleus lies within the capsular bag. The nucleus could be very dense or small and partially absorbed or large

238 THE ART OF PHACOEMULSIFICATION

Fig. 22.24: Splitting of hard nucleus. All bridges between pieces must be broken by wide separation of the pieces

and flaky (Figs 22.25A and B). Once must also note that there is no epinuclear cortex to cushion the capsular bag. In general terms if the capsulorrhexis can be done then the phacoemulsification can be done.

Capsulorrhexis

Capsulorrhexis is the main problem as there is hardly any red reflex. Some steps that can be taken to minimize the chances of a poor capsulorrhexis is to use high magnification, have a very darkroom, start the capsulorrhexis in definite steps in the central portion of the capsule first. If the cortical “milk” starts to obscure the view of the tear then this can be flushed out or pushed to one side with the viscoelastic. Keep looking for the edge of the fold which is more easily seen as a linear reflex in the microscope light. Again, in this situation do not attempt to do too large a capsulorrhexis, in fact, err on the side of a small capsulorrhexis which can be extended if need be once the IOL has been inserted in the bag.

Other Techniques of Visualization of the Anterior Capsule

Other techniques that can be used are by

•Using a retinal endoilluminator held outside the eye to enhance sclerotic scatter and therefore give a clearer view of the capsule.

•To use various dyes and stains. Currently ICG has been described as being very successful in this technique. A few drops of dilute ICG are massaged onto the anterior capsule under air initially. The air is then exchanged and replaced with viscoelastic. Initially the capsule does not appear to be very easily seen but once a tear is made the dye enhances the edge of the torn capsule and it can be seen very easily.

PHACOEMULSIFICATION IN DIFFICULT CASES 239

Figs 22.25A and B: Mature white cataract. Liquid cortex. Flaky, friable nucleus

Other dyes that have been described as being useful are gentian violet and methylene blue, trypan blue (Melles et al: JCRS 25:7-9, 1999).

Hydrodissection

Do not forget that there is no epinucleus to cushion the wave of fluid so hydrodissection has to be done very carefully. Also the nucleus can be small, hard and partially absorbed and this can float around the anterior chamber.

Phacoemulsification

The phacoemulsification in the vast majority of these white cortical cataracts is quite easy as the nucleus is usually very chalky and friable. However in some

240 THE ART OF PHACOEMULSIFICATION

instances in the hard, partially absorbed nucleus this may have to be prolapsed into the anterior chamber to successfully phacoemulsify. Under these circumstances it is important that the corneal endothelium has been assessed in detail before any phacoemulsification in the anterior chamber is attempted.

PSEUDOEXFOLIATION SYNDROME (PES)

The increased risk of cataract surgery in patients with pseudoexfoliation is well known. Potential causes of this increased risk include inadequate pupillary dilatation and a tendency for weak zonular attachment. There has also been recent articles which point to a significantly higher incidence of complications in patients with PES. Complications include zonular dialysis, posterior capsule rupture, an increased fibrinous reaction with posterior synechiae and IOL cell deposits. There is also a finding of increased postoperative inflammatory response in patients with PES.

These studies have also found an impaired blood-aqueous barrier in these patients. Considering all the above it is important that the cataract surgery itself goes

as smoothly as possible with minimum amount of trauma to tissue.

The most pressing problem intraoperatively is one of loose zonular attachments. The important features pointing to weak zonular attachments intraoperatively include the following: a very fine powder-like deposits instead of flaky-like deposits on the anterior capsule; excessive folding of the anterior capsule as the capsulorrhexis is being done; excessive give in the capsular equator as irrigation aspiration is being done.

If there is any concern that the zonules are loose then the options to the surgeon include the following

•Place the IOL implant in the sulcus on top of the capsular bag (Fig. 22.26A).

•Use a capsular tension ring, e.g. Morcher ring. These rings help to stabilize

the lens in the capsule. The ring will spread out the capsule and distribute zonular force at the equator. In fact these rings act as pseudozonules. The ring itself can be put in the capsular bag at any time during the surgery

and currently there are several injectors, e.g. Geuder Shooter which is used fairly successfully in placing the rings in the bag without difficulty.

Capsulorrhexis

It is always wise to start the capsulorrhexis away from the weak zonular zone. The initial zonular tear has been found to be the most stressful on the zonules and if a quadrant of capsule can be identified as having weak zonules.

If an area of capsule can be identified as having weak zonules the capsular tear should be started 180° away from this area.

Phacoemulsification

In these situations where the zonules are weak it is important that not too much flow of fluid be going to the eye as this might cause further rupture of zonules and vitreous prolapse. It is imperative that the power of the phacoemulsification

PHACOEMULSIFICATION IN DIFFICULT CASES 241

Fig. 22.26A: Pseudoexfoliation syndrome (PES). Weak zonules, IOL placed in sulcus

Fig. 22.26B: Late dislocation of IOL and capsular bag in PES

machine is increased but the flow within the eye is decreased. It is also important that the bimanual technique of phacoemulsification be used to help stabilize the cataractous lens.

In summary, the key features in this type of case are

•Proper placement of incision

•Low flow phaco

•High phaco energy

•Use capsular tension ring.