Ординатура / Офтальмология / Английские материалы / Moorfields Manual of Ophthalmology_Jackson_2007

Step 3: Deliberately tilt the keratome posteriorly before advancing the blade to enter the AC (note corneal striae on entry). A temporal incision is preferred as it is astigmatically neutral

(if <3.4 mm) and allows better access. The site of incision may be tailored to reduce preexisting corneal astigmatism (p. 232).

Side port incision

Inject viscoelastic to stabilize the AC. Create a second, limbal side-port incision (paracentesis) 45–90° from the main wound using a diamond keratome or 15° blade; do not make this too wide to avoid leaking or iris prolapse.

Continuous circular capsulorrhexis

Use a cystatome (preformed or bent insulin syringe needle) and/or rhexis forceps (Figs. 6.8, 6.9). Puncture the capsule at the centre and extend radially, ending with a ‘J’-turn to create a curvilinear fold in the favoured direction (clockwise or anticlockwise). Grasp the capsular flap just in front of the tearing point, then pull

SURGERY CATARACT 6 Chapter

of the cannula under the rhexis margin, immediately adjacent to the capsule, advance slightly, then gently inject BSS. A ‘fluid wave’ behind the lens confirms the correct cleavage plane (Fig. 6.10). Gently depress the nucleus to help move fluid around the lens. A single injection is preferred, but repeat the hydrodissection if necessary at a different site until the lens is freely mobile. Hydrodelineation cleaves the adult nucleus from the epinucleus: inject BSS into the lens matter and watch for ‘golden ring’ sign – epinuclear shell may not be easy to remove later but provides useful protection to the posterior capsule for phako-chop techniques.

Phakoemulsification

Know your machine! Piezoelectric crystal in the hand-piece oscillates the titanium phako needle at 35–45 KHz, generating ultrasonic energy in front of the tip. Emulsified lens matter is removed via a central aspiration port. The AC is maintained by fluid entering via the irrigation sleeve, also serving to cool the phako needle (ensure the holes of the sleeve are positioned horizontally so flow is not impeded and is away from the corneal endothelium). Phako machines are flow-based (usually a peristaltic

SURGERY CATARACT 6 Chapter

Basic surgical techniques

pump) or vacuum-based (usually Venturi). Standard linear foot pedal control positions are:

■Position 1: off.

■Position 2: irrigation on (set by the infusion bottle height) with aspiration (set by flow rate and vacuum) increasing with pedal depression.

■Position 3: phakoemulsification increasing to maximum energy set.

Phako techniques A variety of methods are possible according to the type of cataract and surgical skill. Aim to develop an adaptable technique, minimize phako energy and fluid flow, and maintain a stable AC. AC stability is determined by irrigation (height of infusion bottle), vacuum setting, and wound integrity.

■ Divide and conquer

1.Aims to split the nucleus into quadrants for emulsification. The easiest technique to master. Set 60–70% phako

power and 30–50 mmHg vacuum for the first stage. Make a central groove 1.5 times the width of phako tip

(Fig. 6.11), sculpting deeper centrally than peripherally;

beware the rhexis margin. Advance the tip at same speed as emulsification (increase power as required) to avoid pushing the lens. Rotate the nucleus 180° to complete a long groove before sculpting a second long groove at right angles to the first. Alternatively, rotate the nucleus 90° at a time dividing into quadrants with four short grooves. Bimanual rotation minimizes zonular stress; if there is resistance to rotation repeat the hydrodissection. The depth of the groove for successful cracking varies with nucleus density; when the red reflex becomes apparent through the base of the groove, the depth is usually sufficient (Fig. 6.12).

2.To crack the nucleus (Fig. 6.13) make certain the second instrument and phako tip are at the base of the groove. Separate the instruments using an upward pivoting motion (rather than pure lateral movement); this is mechanically more efficient and reduces zonular stress. Ensure the crack extends along the full length. If unsuccessful, the groove is usually not deep enough. For quadrant removal, use 40–60% phako power but increase the vacuum to 140–350 mmHg (flow rate 25–35 mL/min). Position the quadrant to be removed opposite the phako tip. Use

SURGERY CATARACT 6 Chapter

flat under the capsulorrhexis edge, engage opposite the equator of the nucleus, then pull the chopper toward the phako tip to split the nucleus (Fig. 6.14). Just before the instruments meet, move the chopper at right angles to release the wedge of nucleus for emulsification. For a vertical chop technique, use sharp tipped chopper to vertically incise the heminucleus (within the capsulorrhexis) toward the embedded phako tip. Lift the engaged nucleus slightly to facilitate cleavage before lateral separation of the chopper and phako tip to complete fracture. Rotate the nucleus clockwise and repeat the chopping action until the nucleus is completely removed.

■‘Primary chop’: no sculpting required for this technique. Impale the nucleus with the phako tip just proximal to the centre and immobilize with high vacuum (phako power 40–60% on burst and vacuum 250–350 mmHg). Follow with either horizontal or vertical chop (as above).

■‘Taco’ technique : useful for soft nuclei that are too soft to crack after sculpting a central groove. Fold the nucleus into the groove using aspiration and second instrument manipulation to ‘tyre iron’ the heminucleus into the phako tip (minimal or no phako energy is required).

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Basic surgical techniques

Cortical clean up

Residual cortical or soft lens matter (SLM) is removed using manual (Simcoe) or automated irrigation and aspiration (I&A) systems (Fig. 6.15). The authors favour the Simcoe. Engage SLM beneath the anterior capsule with the tip of the cannula and use aspiration to strip from the periphery to the centre. Excessive pulling (c.f. aspiration) risks PC rupture if the capsule is inadvertently engaged (indicated by star-shaped capsular striae). If the capsule is engaged, keep the instrument still and reflux immediately (if using automated I&A check the correct pedal action beforehand). Proceed circumferentially until all SLM is cleared. Difficult-to-remove subincisional SLM can be tackled with the Simcoe via the second instrument port or a second side port placed opposite the main incision. Ninety degree angled tips for the automated I&A are also available. Alternatively, remove the remaining SLM after IOL insertion – dialling the IOL can loosen material with the optic protecting the PC. Residual SLM may prolong postoperative inflammation and cause early PCO, but better to leave small amounts than risk PC tear.

Capsule polishing : The PC can be polished with automated I&A or a dedicated polisher with a roughened surface under viscoelastic. Manual focal irrigation after filling the bag with hypromellose is also effective at stripping residual cortex/plaque (‘jetwash’ technique). If there is a resistant plaque, try viscodissection to raise the edge then peel with rhexis forceps (very risky). Routine removal of residual lens epithelium from the equator (and anterior capsule) may reduce the risk of capsular fibrosis/PCO.

Basic surgical techniques

avoiding contact between the IOL and ocular surface, and usually permit smaller incisions (Fig. 6.16).

Final steps

Remove all viscoelastic from the AC and behind the IOL to minimize postoperative IOP rise or capsular distension syndrome. Tilt the optic gently with the cannula (‘rock and roll’) to dislodge viscoelastic from behind the IOL or place the tip behind the optic. Finally, deepen the AC with BSS via a side port and check wound integrity with a sponge. A well-constructed incision is self-sealing and stromal hydration is unnecessary. If wound leaks, suture with 10/0 Nylon or 10/0 Vicryl. Inject subconjunctival antibiotic (cefuroxime 250 mg or gentamicin 25 mg) and steroid (betamethasone 2–4 mg). Protect the eye with a clear shield alone if the blink reflex is present, or else use a pad and shield.

Postoperative care Prescribe oral acetazolomide 250 mg stat and at 6 hours postoperatively, G. dexamethasone 0.1% q.d.s. 4 weeks then taper; G. chloramphenicol 0.5% q.d.s. 2 weeks. Not all surgeons prescribe acetazolamide routinely. Use 6 per day steroids for the first week in Asian, Afro-Caribbean, and diabetic patients who are prone to more vigorous postoperative inflammation. Where the iris has been manipulated (e.g. hooks, iris prolapse) some surgeons add G. ketorolac 0.5% (Acular) q.d.s. 1 month to reduce the risk of cystoid macular oedema.

Patient advice Advise patients to return immediately if they experience visual loss, pain, or redness. Wear the shield at night for 2 weeks. Avoid splashing or rinsing water in the eye for 1 week; avoid swimming until off steroid drops. With self-sealing incisions, limiting heavy lifting and bending is less important, but avoid for 2 weeks.

Follow–up Review on the day of surgery or postoperative day 1 to check IOP, IOL position, and wound integrity. Thereafter, review on day 7–21 primarily to assess visual outcome and inflammation as well as dilated retinal examination. If there are no problems, discharge or list for second eye surgery. Recommend refraction 4–8 weeks postoperatively in routine cases.