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

Phacoemulsification offers the advantages of rapid wound healing and early visual rehabilitation. However, economic constraints in developing countries place phacoemulsification beyond the reach

of many ophthalmic surgeons.

The manual phacofragmentation is the alternative technique to solve many problems. So, we created a new method called “Phaco–drainage”. I have used this technique since 1998 and have done more than 100 operations by this technique.

Preoperative Assessment

Cataract with nucleus grading I-III and no weakness of zonules are selected. Complete ocular examination, endothelial cell counts and IOP are measured in every case. Three special instruments are required:

1.Anterior chamber maintainer

2.Aspiration cannula and

3.Nucleus removal tube (Amporn–tube)

Fig. 25.1: Nucleus removal tube (Amporn-tube)

Idea Concept

1.Crack the nucleus into small pieces

2.Remove the pieces of nucleus through 3.5 mm long corneal wound.

3.Use passive–aspiration force to remove the pieces of nucleus.

Fig. 25.2: Corneal wound is made

Fig. 25.3: Hydrodissection

After peribulbar anaesthesia is given, I perform paracentesis at 2 sites at 6 and 12 O’clock. Six O’clock is used for inserting A/C maintainer and 12 O’clock for viscoelastic injection. After viscoelastic injection, make a 3.5 mm long corneal wound at temporal site. A large

capsulorhexis (5.5–6.5 mm) is performed. Hydrodissection and hydrodelineation are carried out.

Cracking the nucleus into 4 pieces in the capsular bag with capsulorhexis forceps and Sinskey hook (very similar to pre–chop technique). The advantage of this technique is reduced corneal endothelium trauma.

Insert the nuclear removal tube through corneal wound (3.5 mm) for removing the pieces of nucleus by this tube. The advantages are reduced wound size and wound trauma.

Open the infusion line, BSS goes into the anterior chamber via A/C maintainer. When I open the valve, (at

handle of the nuclear removal tube) passive aspiration force occurs; and when I close the valve, the passive force is stopped. That means I can control passive aspiration force by closing and opening the valve. The advantage is, I do not need any machines for suction force , decrease chance of A/C collapse , and decrease turbulence flow.

We can increase the passive aspiration force by increasing the height of bottle. Almost the height 60–70 cm is enough for creating the passive aspiration force.

If the pieces of nucleus are too large, two Sinskey hooks are used to crack it into smaller pieces again. So that they it can pass through the tube.

Fig. 25.8: Remove the remaining cortex

After removal of all nuclear pieces, I clean the remaining cortex by aspiration cannula.

Turn off BSS line and reinject the viscoelastic substance into anterior chamber. Next, insert the foldable IOL as regular method.

No serious complications are seen. A few cases of iris trauma and corneal wound oedema in the early period are found.

Advantages

Result

On first postoperative day, the central corneas were clear and cells or flasre were minimal (no difference from phacoemulsification).

1.No ultrasound—No heat.

2.Cheap (do not need complicated machine).

3.Less wound trauma (because pieces of nucleus pass through tube and not through corneal wound).

Fig. 25.10: First postoperative day

4.Minimal turbulence flow (decreased BSS to be used).

5.Can be inserted the foldable IOL.

Disadvantages

1.Selected cases (NS grade 1+ to 3+).

2.More total operation time (average ≈ 30-40 min./case).

3.Need learning period.

4.Need special instruments (The nuclear removal tube).

CONCLUSION

I can perform cataract surgery with small incision without phaco–machine in normal cataract cases (NS 1+ – 3+), Improving the quality of nuclear removal tube is recommended for improving the efficacy of operation (The nuclear removal tube is handmade , and the reusable tube is not of good quality).

The concept of surgically induced astigmatism has added an entirely unique dimension to cataract surgery with emphasis more focussed on the

refractive aspect of the surgery in present era.

Over the years, the better understanding of various preoperative and intraoperative determinants of surgically induced astigmatism has made it possible to actually plan out the surgical intervention and their modifications according to preoperative state of astigmatism of the patient in order to achieve minimum possible or nil postoperative astigmatism.

Incision being the first and the most important determinant of postoperative astigmatism which can be modified in various ways in terms of size, site, shape, axis, etc. to reduce the degree of postoperative astigmatism. Placement of incision temporally along the vertical meridian is one modification to minimise the high pre-existing against the rule (ATR) astigmatism, thereby improving the visual outcome.

Besides, a temporal incision has other advantages too, it induces less amount of astigmatism as compared to superior one and has a better wound strength due to minimal separational force of lid pressure and gravity. The temporal limbus being farther from visual axis it causes less distortion of central corneal curvature, particularly in cases of secondary IOL implantation or in eyes with previous surgery at 12 O’clock position

A temporal incision offers a distinct advantage of avoidance of incision being placed over the compromised scar tissue or preservation of functioning filtering bleb in previous glaucoma surgery. The incision on temporal side is also preferable in deeply seated eyes of operational case and in cases of coloboma of iris.

ADVANTAGE OF TEMPORAL INCISION

Reduction against the Rule (ATR) Astigmatism

With the rule (WTR) astigmatism was found in 90 per cent of population which shifts to against the rule (ATR),

as the age advances, so that incidence of ATR is 5 to 6 times higher in age above 50 years (Duke Elder, 1969).

Jaffe (1975) observed prevalence of astigmatism as WTR 30 per cent, ATR 42.5 per cent and oblique in 17 per cent in preoperative cases and similar observation by Singh and Kumar (1976) ATR 45 per cent, WTR 30 per cent and oblique in 15 per cent.

Cornea flattens over any incision and this effect increases as incision approaches near the visual axis thus superior incision results in postoperative ATR. This effect in terms of visual gain is beneficial to preoperative WTR case, but unfavourable visual results in cases having high ATR preoperatively.

Therefore, the property of cornea to flatten along the incision can be used to flatten the steeper horizontal meridian in cases of preoperative ATR astigmatism by placing temporal incision.

For many years the superior site has been favourable approach in most of intraocular surgical procedure and it continues to be favoured location even today. In 1993, Joel C performed surgery of cataract by lateral incision and found net reduction of ATR by 0.72D—statistically a significant amount. Thereafter, many other workers advocated this approach to reduce or nullify ATR astigmatism (Nelson PJ, 1995; Haberle H et al, 1995; Volkmer C, 1996; Weindler J 1996; Antoni HJ, 1997; Lyhne N et al, 1998; Schuler 1998).

Bohm B et al (1997) reported lateral approach with scleral tunnel to be safe procedure and suggested it to be used routinely in all patient having preoperative ATR astigmatism.

Useful in Secondary and Combined Procedure

Masket S (1986) in his study on secondary IOL implantation demonstrated overall reduction or corneal cylinder from modest flattening of surgical axis with a temporally oriented scleral pocket incision and found it water tight stable wound with astigmatic control.

Gayton JL (1996) found a substantially greater number of cases receiving a temporal cataract incision with a superonasal trabeculectomy.

Caprioli J et al (1997) and Rossetti L et al (1997) also found the temporal incision advantageous in cases where superior limbus used for glaucoma surgery. It not only preserves the functioning bleb, but also minimises the ATR astigmatism resulted from previous surgery.

Stable Incision

Cravy TV (1991) found a statistically significant and prolonged stabilisation of keratometric astigmatism in planned ECCE via a lateral approach as compared to identical surgery performed in vertical meridian.

Vazquez LA et al (1993) concluded that horizontal 5 mm sutureless scleral tunnel incision showed less induced astigmatism with most rapid stable refraction. Similar observation by Wong HC et al (1994) and Haberle H (1995).

Zheng et al (1997) found a 3 mm temporal pocket incision tube astigmatically neutral. Simsek S et al (1998) concluded that upper lid pressure on superior corneal incision led to fluctuating ATR astigmatism. Wollensack J et al (1995) and Anders N et al (1997) reported scleral tunnel incision has highest wound stability as compared to incision at 12 O’clock.

Corneal Topographic Changes

Vass C and Menapace RJ (1994) have reported in their computerised statistically analysis of corneal topography for changes after temporal incision resulted in mean flattening of 0.4 to 1.4 D in temporal region but no significant vertical steepening or nasal flattening noticed, hence less effect on visual axis.

Hoffer KJ (1994) has reported that the temporal incision induced minimal central endothelial cell loss compared to a superior incision group since superior cornea is closer to central cornea.

SURGICAL STEPS

There is no more difference in surgical steps of temporal tunnel as compared to small incision cataract surgery from superior incision. Before considering surgery through a temporal incision, certain modifications of the surgical set-up and adjustments are necessary.

•Surgeon is required to perform the surgery from the side and hence instead of sitting towards the head of the patient, sits by his corresponding side

•Operating microscope needs to be positioned accordingly

•As there is no support for the surgeon’s wrist, some kind of support (e.g. in the form of two cushions) has to be used

•Bridle suture is passed underneath the lateral rectus muscle instead of superior rectus suture (optional)

•All the steps of the surgery are the same as those being performed from 12 O’clock position, but the incision has to be bevelled more anteriorly as the temporal limbus is away as compared to the superior limbus

•Lastly, performing the surgery from temporal aspect changes the functional angle, to which the surgeon has to adjust himself initially. But after some practice this position becomes less awkward and tedious (Fig. 26.1).

Fig. 26.1: Temporal incision: extending the incision

COMPLICATIONS

Complications are few and manageable and are similar to SICS preformed from superior sector, but once the technique is mastered, it is very safe and rewarding. Intraoperative complications in our series of first 100 cases were noticed as:

Premature anterior chamber entry 7.5 per cent, iridodialysis 7.5 per cent, posterior capsular rent 2.5 per cent.

Postoperative complications includes-striate keratopathy 45 per cent on 1st day which is always reversible, fibrinoid reaction in 10 per cent, which responds quickly to subconjunctival steroids + antibiotics injection. Pigment dispersion in 5 per cent cases. Conjunctival flap retraction was more common 10 per cent as compared to SICS for superior site as the conjunctival flap has no support of lid pressure and gravity force.

Postoperative astigmatic control in our series of 100 initial cases 70 per cent was astigmatism upto 0.5 D and rest 30 per cent upto 1.0D.

Thus showing a significant and favourable postoperative refractive condition, which gives an edge over other surgical site.

There is WTR shift in temporal tunnel sutureless surgery. A 6 mm to 6.5 mm temporal incision produced a mean surgically induced astigmatism (SIA) was 0.6 D while same size of incision superiorly produces mean astigmatism 0.98 D ATR (Similar observation by Neilson PJ (1995), Ullern M (1997) Chou JC (1997), Huang F (1998).

Thus significantly minimum produced astigmatism has always resulted in better unaided visual acuity. The basic principle of “Incision causing flattening along the meridian in which it is placed” has been utilized for management of moderate to high degree of preoperative astigmatism. The temporal incision was a neutralising effect on preoperative ATR.

CONCLUSION

Preoperatie determinants form a major factor in final visual outcome following cataract surgery a meticulous work-up of preoperative astigmatism is necessary in order to reduce it, by suitable plan.

Entire surgical set-up and adjustment of surgeon’s positions, support to wrist, etc. are necessary before proceeding to surgery from temporal side.

Incision has to be bevelled more anteriorly as temporal limbus is farther from visual axis. Due to change in functional angle this approach of surgery may require little practice.

Mean surgically induced astigmatism was 0.6 D. There is WTR shift in all cases of temporal incision. Confirming this technique as “add” to refractive surgery while performing SICS, apart from this the temporal wound was found to be more stable. This is a incision of choice in all cases who have undergone previous surgery from 12 O’clock position.

A simple modification in incision placement produced comparable results to other sophisticated procedure and hence offers a way to attain better surgical outcome with limited resources available in most of the set-up.

BIBLIOGRAPHY

1.Anders N et al: Postoperative astigmatism and relative strength of tunnel incision: A prospective clinical trial. J Cataract Refract Surg 23(3): 332-36, 1997.

2.Antoni HJ et al: 3½ years experience with ECCE with tunnel incision. Ophthalmologe 94(1): 12-15, 1997.

3.Bohm B et al: 7 mm tunnel incision with lateral approach as routine intervention in cataract surgery. Ophthalmologe 94(1): 3-5 1997.

4.Caprioli J et al: Temporal corneal phacoemulsification in filtered glaucoma patients. Trans Am Ophthalmol Soc 95:, 153-67; Discussion 167-70 1997.

5.Chou JC et al: Cornea refractive changes after clear cornea phacoemulsification with foldable intraocular lens. Chung Hua I. Hsuch Tsa Chih (Taipei) (Taiwan), 60(4): 195-98, 1997.

6.Cravy TV: Routine use of a lateral approach to cataract extraction to achieve rapid and sustained stabilization of postoperative astigmatism. J Cataract Refract Surg 17(4): 41523, 1991.

7.Duke-Elder WS: System of Ophthalmology, Henry Kempton London: 5: 95-102 274-80, 370-76, 1959.

8.Gayton JL et al: Combined cataract and glaucoma procedures using temporal cataract surgery. J Cataract Refract Surg 22(10): 1485-91, 1996.

9.Haberle H et al: Induced astigmatism in extracapsular cataract extraction with tunnel incision and various wound closures.

Klin Monatsbl Augenheilkd 207(3): 176-79, 1995.

10.Heider W et al: Corneal topography after cataract surgery with tunnel incision on a steeper meridian in inverse and oblique astigmatism. Ophthalmologe 1997.

11.Hoffer KJ: Cell loss with temporal and superior incisions. J Cataract Refract Surg 20: 308, 1994.

12.Huang FC et al: Comparison of surgically induced astigmatism after sutureless temporal clear corneal and scleral frown incision. J Cataract Refract Surg 24(4): 477-81, 1998.

13.Jaffe N: Cataract Surgery and its Complications. CV Mosby and Co: St. Louis 111-12, 127, 246-53, 1984.

14.Joel C Axt et al: Reduction of postoperative against-the-rule astigmatism by lateral incision technique. J Cataract Refract Surg 19(3): 380-86, 1993.

15.Lee T Nordan: The surgical rehabilitation of vision: An integrated approach to anterior segment surgery. Gower Medical Publishing: London, 23, 1992.

16.Liekfeld A et al: Self-closing corneoscleral tunnel incision in cataract surgery. Ophthalmologe 93(1): 8-11, 1996.

17.Lyhne N: Relationship between preoperative axis of astigmatism and postoperative astigmatic changes after superior scleral incision phacoemulsification. J Cataract Refract Surg 24(7): 435-39, 1998.

18.Masket S: Temporal incision for astigmatic control in secondary implantation. J Cataract Refract Surg 12(2): 17981, 1986.

19.Nielson PJ: Prospective evaluation of surgically induced astigmatism and astigmatic kerototomy effects of various self sealing small incision. J Cataract Refract Surg 27(1): 43-48, 1995.

20.Simsek S et al: Effect of superior and temporal clear corneal incisions on astigmatism after sutureless phacoemulsification.

J Cataract Refract Surg 24(4): 515-18, 1998.

21.Singh D, Kumar K: Keratometric changes after cataract extraction. BJO 60: 638-41, 1976.

22.Vazquez LA et al: Surgically induced astigmatism: A comparison of different cataract incision and closures PK Health Sci J 12(2): 99-103, 1993.

23.Volkmer C et al: Minimising astigmatism by controlled localization of cataract approach with the no stitch technique: A prospective study. Klin Monatsbl Augenheilkd 209(2-3): 100-04, 1996.

24.Weindler J et al: Is cranial corneoscleral 6 mm ‘no-stitch’ tunnel incision contraindicated in against-the-rule astigmatism?

Klin Monatsbl Augenheilkd 208(6): 428-30, 1996.

25.Wong HC et al: Corneal astigmatism induced by superior versus temporal corneal incisions for extra-capsular cataract extraction. Aust NZ J Ophthalmol 22(4): 237-41, 1994.

26.Zheng L et al: Astigmatism and visual recovery after ‘large incision’ extracapsular cataract surgery and ‘small’ incision for phacoemulsification. Trans Am Ophthalmol Soc 95: 387410, Discussion 410-15, 1997.

Delivery of the nucleus either in one piece or in fragments marks the beginning of cortical aspiration. The cortex is also referred to as soft lens matter and its adequate removal is a very important

step in present day cataract surgery, be it a conventional extracapsular cataract extraction, phacoemulsification or small incision cataract surgery. Ability to ensure its complete removal distinguishes the modern cataract surgery from its earlier version. Successful cortical clean-up involves adequate cortical removal while preserving the capsular bag, suspensory ligaments of the lens (no zonular dialysis) and the integrity of corneal endothelium. Complete removal of the cortex goes a long way in restoring quicker and better visual acuity. It also reduces the chances of uveitis, posterior capsular opacification and IOL decentration. It also greatly enhances the visibility of the posterior segment in the event of any posterior segment pathology like retinal detachment, diabetic retinopathy, etc.

For the removal of the cortex, coaxial retroillumination is invaluable. However, with proper regard for the macula, this illumination must be used for as short a time as possible. This type of illumination should end as soon as the lens is implanted by either turning the eye away from the upward direction by tightening the superior rectus bridle suture or by changing to oblique illumination or by both.

Cortical removal can be accomplished using either the automated systems or manual irrigation aspiration (I/A) devices depending upon the preference of the surgeon or the demands of the situation. Each method has got its merits and demerits. No single technique is suitable in all circumstances. Each surgeon has got his own likes and dislikes and selects a technique that suits him the best. Even for those surgeons who are using an automated system for irrigation aspiration, it is imperative that instruments for manual cortex removal be at hand since a machine can fail. Familiarity with instruments for manual cortex removal is also essential. If the surgeon is unprepared for machine failure and it occurs in an eye

with small pupil and stringy cortex (which is difficult to aspirate by any technique) then the patient is in serious jeopardy. Every surgeon without a back-up I/A unit must master a manual cortical aspiration technique (Fig. 27.1).

Fig 27.1: I/A of cortex technique by simcoe

The main advantages of automated I/A system include removal of the cortex in a tightly closed anterior chamber as a result anterior chamber remains deep, fornices remains open and easily accessible. There is no forward movement of the vitreous and posterior capsule and less chances of choroidal effusion or haemorrhage. Chances of endothelial damage are less as the anterior chamber remain deep all the time. The automated system however, is not free from certain disadvantages like it is a difficult procedure, requires prior setting and it lacks the instantaneously variable intraoperative control by the surgeon. In a tightly closed chamber, a sudden surge of machine controlled infusion pressure can rupture the posterior capsule. Outflow around a cannula in a less tightly closed chamber decreases the chances of rupture but increases irrigation volume requirement and causes more endothelial damage. Conversely, manual cortical clean-up can be easily mastered ensures self-reliance, and offers greater safety, sensitivity, flexibility and reliability.

With patience a surgeon can gradually learn to apply a degree of suction appropriate to the quality of cortical matter to be aspirated. The cortical material in the fornix has a very dense and mucoid consistency and therefore needs a higher level of aspiration which is immediately administered by a thumb pull. In the case of granular cortical material, less suction is required and a more delicate pull is used. With experience one gets to know almost intuitively how much suction to apply to each of the cortical presentations. There is no machine that can produce the delicate control of cortical aspiration that the human brain, coordinating with a hand, can sustain. Therefore, we strongly favour manual aspiration as opposed to the insensitive machine aspiration in small incision cataract surgery.

The present chapter is designed to help define manual cortical removal technique. It may also stir interest in surgeons who are “married to the machine” to stimulate them to try something new. Some surgeons may even be converted to the manual technique.

Cortical aspiration in small incision cataract surgery is much different than cortical aspiration in extracapsular cataract extraction procedure. For one thing, there is much less cortex to remove. Some of it was washed away with the hydrodissection, and some of it came out with the outer nucleus. Secondly the closed chamber technique in small incision cataract surgery also helps to maintain the depth of the anterior chamber and that makes it easier to get out the cortex. Deep anterior chamber also helps to avoid corneal endothelial damage from instruments or excessive irrigation as well as capsule or vitreous injury. If a continuous curvilinear capsulorhexis has been done instead of a can-opener capsulotomy it makes the cortical aspiration much more easier because it eliminates the capsular flaps that may interfere with the aspiration. Subincisional cortex is however most difficult to remove in small incision cataract surgery.

A large variety of manual irrigation aspiration cannula are available in the market, but the most commonly used one is Simcoe cannula. It is a small calibre (thin wall 23 gauge) twin barrel I/A unit, one for aspiration and another for irrigation. Aspiration port is situated anteriorly where as infusion port is situated on the side. Simcoe cannula are available in various gauges from 21 to 24, but 23 gauge is probably the best, because port size is such that it is occluded by one tissue at a time either cortex, capsule or vitreous. Its port size is large enough for quick and safe cortical aspiration.

Irrigation aspiration in Simcoe cannula is independently variable: control is sensitive, instantaneous, and

immediately reversible. This inexpensive, autoclavable unit can be reused for a large number of times.

Simcoe cannula is of two types—direct and reverse depending on the mode of infusion aspiration. In Simcoe reverse cannula aspiration is bimanual and infusion is either through a separate syringe connected to the cannula by a silastic tubing and held by an assistant or through a gravity infusion, in which silastic tubing of the cannula is connected by a drip set to the infusion bottle held high-up in a drip set stand. Infusion rate in the later veriety is controlled by a stop attached with the drip set. In Simcoe direct type surgeon holds the cannula in one hand (right hand for a right handed person) and aspiration is through the adjacent twin cannula connected by silastic tubing to a syringe isolated in the other hand. Infusion in this type is either from a silastic squeeze bulb or directly through an infusion bottle connected to the cannula by a dripset. Infusion through a silastic squeeze bulb is directly under the control of the surgeon, as a result it is gentle, minimal and just sufficient to replace the aspirated volume thereby avoiding turbulence in the anterior chamber. On the other hand gravity infusion lacks the sensitive, variable control of the bulb.

The syringe used for cortical aspiration has to be capable of providing proper suction. Leaking plungers, tight syringes too large or too small syringes do not work properly.

Once the surgeon has got the instruments of his liking the process of cortical clean-up begins. Curved Simcoe cannula is gently slipped into the anterior chamber and the loose cortical material floating in the anterior chamber is gently aspirated. Remove as much large cortical material as possible before turning to fine cortical remnants. Because in the event of vitreous loss fine cortical remnants in the vitreous will get absorbed, where as larger cortical fragments can lead to a very severe inflammatory response. Once the free floating cortical material has been aspirated, cannula is placed beneath the margin of the anterior capsule and the cortical mater is engaged by applying gentle suction through the syringe and by a combination of rotation and translation pulled and brought into the centre of the pupil before finally aspirating it (Fig. 27.2). Aspiration always proceeds from periphery to the centre of the pupil, never in the reverse direction. Only material that is clearly visible should be aspirated. Tissue in the blind, under the iris, should be moved to the pupillary area before the aspiration is done. While aspirating the porthole must be visible, i.e. it must face vertically upwards. This technique exploits the fact