Ординатура / Офтальмология / Английские материалы / Moorfields Manual of Ophthalmology_Jackson_2007

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Fig. 6.16: Insertion intraocular lens. (A) Manual insertion of an Acrysof MA60 IOL. (B) Injection of Akreos Adaption. (Note leading haptic orientation curving to left being introduced beneath anterior capsule rim).

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Difficult cases

Difficult Cases

Small pupil Anticipate in diabetes, pseudoexfoliation syndrome (PXF), chronic miotic use, advanced age, and posterior synechniae. Consider the following:

■Optimise mydriasis : stop miotics in advance, dilate with cyclopentolate 1%, phenylephrine 2.5% (or 10% but beware BP elevation) plus G. NSAID (e.g. flurbiprofen 0.03%) three times preoperative. If the pupil is still light responsive, give more drops. Intracameral dilute adrenaline is also useful (0.5 mL 1 : 1000 epinephrine in 500 mL BSS).

■Highly cohesive viscoelastic : e.g. Healon GV or 5 helps to splint the pupil open.

■Posterior synechiolysis : inject viscoelastic under the pupil margin and sweep the iris free with a cannula or iris repositor. Consider pupil stretch. Remove any pupillary membrane with forceps.

■Iris hooks (Fig. 6.17): make limbal stab incisions parallel to the iris (or angled slightly posteriorly) with a 25-gauge orange needle or the tip of an MVR blade; avoid the main wound or side ports. Ensure the proximal two hooks are close to the

main incision to avoid ‘tenting’ and consequent iris trauma by the phako tip. Insert the hooks into the AC, engage the pupil margin and retract. Only adjust to final tension after all hooks are in situ – do not overstretch. If placing hooks is difficult due to a deep AC, indent the globe at the limbus for easier iris capture. To remove hooks, simply disengage the iris and pull. Alternatives include bimanual pupil stretch, multiple small sphincterotomies, and pupil ring expanders.

Zonular weakness/dehiscence Beware in PXF, advanced age, previous trauma or surgery, vitrectomized eyes, high myopia, Marfan’s syndrome, homocysteinuria, WeillMarchesani syndrome, and sulfite-oxidase deficiency. Look for phakoor iridodonesis and identify the location of zonular deficiency preoperatively. Aim to minimize zonular stress. Use viscoelastic generously to tamponade areas of zonular dehiscence. Consider each surgical step in turn:

■Main incision : place opposite the zonular weakness if possible.

■Capsulorrhexis : initiate the capsulorrhexis toward the weak zonules using the intact zonules for counter-traction. Iris hooks or a second instrument at the capsulorrhexis margin can provide extra stability. Ensure an intact capsulorrhexis is large enough for easy removal of nuclear fragments.

■Hydrodissection : ensure good cortical cleavage and hydrodelineation but inject extremely gently.

■Phako : use sufficient phako power to avoid ‘pushing’ the nucleus during sculpting and rotate carefully. Horizontal phako-chop technique produces less zonular stress (p. 248). Beware floppy posterior capsule when removing the last fragments; lower the vacuum and flow rate and consider pulse mode.

■Cortical removal : strip the SLM tangentially (c.f. radial) to spread forces. Consider using viscoelastic to keep the capsular bag open or stabilize by preplacing an IOL or capsular tension ring (CTR, see below).

■IOL implantation : insert the leading haptic into the bag towards the area of zonular weakness and gently direct the trailing haptic into the bag with MacPherson’s forceps (avoid aggressive dialling). Alternatively, inject the IOL so both haptics unfold directly in the bag. Position the IOL with haptics on the axis of zonular weakness to achieve the best

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PMMA, available in a range of sizes denoted by the diameter of the open ring/compressed ring in millimetres, e.g. 12/10. Insert as large a ring as possible, especially in high myopes. Overlapping of the ends of the CTR is acceptable.

Contraindications include incomplete capsulorrhexis or anterior capsule tear, posterior capsule tear if not concentric, and ≥180° zonular dialysis. Insert intact into the bag at any point after capsulorrhexis using forceps or injector. Aspiration of soft lens matter (SLM) trapped under the CTR may be difficult, so delay insertion until after cortical clearance if possible. If zonular loss is marked consider a modified CTR with one or two eyelets positioned anterior to the capsule to allow scleral fixation (e.g. Cionni ring) or, alternatively, consider a sutured PCIOL or ACIOL.

Brunescent lens Dense, large nuclei are at high risk of posterior capsular tear, zonular dehiscence, corneal endothelial damage, and phako wound burns. Use a ‘soft shell’ viscoelastic technique (see below). Ensure a large capsulorrhexis for safer phako and manipulation. Keep the bottle height low to reduce irrigation volume if surgery is prolonged. Chop techniques reduce phako time and zonular stress. Move the phako tip slowly when sculpting; avoid pushing lens and use sufficient power to emulsify. Beware grooving too deep as the epinucleus is thin or absent. Reduce the total phako time using burst mode or pulse mode (also reduces ‘chatter’ during fragment removal, i.e. fragments being pushed away from the tip). Dense adhesions may preclude adequate cracking/chopping and residual plate may require separate phako removal.

White cataracts Absent red reflex, release of ‘lens milk’, and risk of peripheral capsular tears makes capsulorrhexis difficult (Fig. 6.19). Use trypan blue 0.06% (Vision BlueTM ) to improve capsule visualization. Increased pressure from the intumescent lens may cause the capsulorrhexis to tear peripherally, so aim to make a slightly smaller capsulorrhexis and consider higher-density viscoelastic. See also brunescent lenses above.

High myopia Exclude peripheral retinal breaks preand postoperatively. Discuss refractive targeting and the risk of retinal detachment. If the patient desires unaided reading vision, aim for −2.50 DS; for emmetropia aim for − 0.50 DS. Beware posterior staphyloma so consider a B-scan cross-check to confirm the axial length (p. 257). Avoid sharp needle LA techniques. The AC is deep, so make a short tunnel incision to avoid distorting the cornea. Capsulorrhexis is more difficult with a deep AC but keep fully formed with viscoelastic to avoid a peripheral tear and do not make it too large. A steep approach with phako makes sculpting

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Fuchs’ endothelial dystrophy/Guttatae Minimizing endothelial cell loss is paramount. Use a ‘soft-shell’ technique : inject dispersive viscoelastic (e.g. Viscoat) adjacent to the endothelium then expand the AC below using cohesive viscoelastic, thus spreading dispersive agent against endothelium. Phako as far from the endothelium as safely possible and reduce total energy with phako-chop and cool/pulse/burst mode. Avoid applying phako power within dispersive viscoelastics as they may coagulate, block aspiration, and cause a phako burn.

Uveitis Explain the increased risks of surgery (relapse of uveitis/cystoid macular oedema, CMO) and the need for careful follow-up. Ideally, uveitis should be controlled for 3 months preoperatively and treatment stable. Pre operative steroids are indicated in patients with posterior uveitis, a history of CMO with anterior uveitis, or CMO following surgery in the first eye. The regimen is usually prednisolone EC 40 mg o.d. for 2 weeks preoperatively and tapered by 5 mg/week postoperatively to the preoperative dose, or, if contraindicated, consider intravitreal triamcinolone at the time of surgery (if not a steroid responder). Use a clear corneal incision, acrylic foldable IOLs, and intensive postoperative topical steroids (G. dexamethasone 0.1% 1–2- hourly). Patients with a history of anterior uveitis not associated with CMO do not usually require prophylactic systemic or topical steroids, but those with chronic anterior uveitis should receive dexamethasone 0.1% b.d.–q.d.s. preoperatively. Patients with Fuchs’ heterochromic cyclitis require no topical steroids preoperatively but will require at least q.d.s. dexamethasone 0.1% or equivalent postoperatively.

Glaucoma Be aware that nuclear sclerosis may give the false impression of preserved neuroretinal tissue at the optic disc. Patients with a past history of angle closure glaucoma are likely to have a shallow AC and may get postoperative corneal decompensation. Those with advanced glaucoma may lose VA if postoperative IOP elevation ‘snuffs out’ the small remaining island of vision; however, avoid oral acetazolamide in those with functioning trabeculectomies as reduced aqueous flow may promote fistula closure. Small pupils are common in those on miotics; where possible discontinue 2 weeks preoperatively. Temporal clear corneal incisions help avoid conjunctival manipulation at the site of existing or future trabeculectomy blebs. Those with functioning trabeculectomy blebs require longer and more intensive postoperative steroids, e.g. dexamethasone 0.1%, 2-hourly for the first week then q.d.s., tapering off over 3 months. Some clinicians advocate subconjunctival 5FU at the time of surgery.

Diabetes See page 469.

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Intraoperative complications

Intraoperative Complications

When complications occur during surgery: stop, take a deep breath, and think clearly about what to do next.

Posterior capsule tears

Posterior capsule tears (PCT) during phakoemulsification occur at <1% amongst experienced surgeons, and up to 15% amongst juniors. Identification of predisposing factors, timely recognition, and appropriate management significantly minimizes the associated morbidity. Signs of PCT include sudden deepening of the anterior chamber (AC) and momentary pupil dilatation, direct visualization of the capsule defect or vitreous prolapse, sudden shallowing of the AC during hydrodissection, unstable or immobile lens, and occlusion of the phako handpiece (vitreous occlusion).

Figure 6.20 outlines the management of PCT. If suspected, do not immediately remove instruments from eye; instead, lower the bottle height to minimum and assess:

■Extent of the PCT and vitreous loss into the AC.

■Amount of residual lens matter – if the nucleus is remaining, the priority is to safely prevent dropped fragments.

■Remaining capsular support – is sufficient capsule present to secure a PCIOL either in the bag or sulcus?

The key principles are to stabilize the AC, preventing extension of the PCT/further vitreous prolapse, and to perform as few manoeuvres as possible to achieve the desired repositioning of the vitreous. If no vitreous prolapses from a small PCT with intact anterior hyaloid face, it may be possible to convert to a primary posterior capsulorhexis after visco-tamponade and residual nucleus may be removed by careful phako (low vacuum/flow rate), thus avoiding anterior vitrectomy entirely. If there is vitreous loss into the AC, retrieve any free lens fragments manually (Fig. 6.21) but perform anterior vitrectomy (Box 6.3) before attempting to remove any lens material trapped by vitreous. Scissor/swab vitrectomy may be sufficient if the prolapse is minimal (Fig.

6.22).

Posterior capsular tear (PCT)?:

Keep instruments in eye, lower bottle height to minimum and assess.

Stabilise AC with viscoelastic via side port before removing phako probe.

Check wounds: with dry swab; residual vitreous wick betrayed by peaked or moving pupil. Cut strand with Ong scissors, sweep centrally with iris repositor then recheck wound/pupil. Additional anterior vitrectomy occasionally required after IOL insertion. Suture using 10/0 Nylon, remove viscoelastic anterior to IOL, subconjunctival antibiotic and steroid, post-op Diamox 250–500mg po stat.

* Alternatively, some prefer secondary sutured PCIOLs (e.g. in corneal decompensation, guttatae, shallow AC, angle pathology, glaucoma) but beware of associated complications (e.g. subluxation, vitreous haemorrhage, RD).

Fig. 6.20: Algorithm for management of posterior capsule rupture.

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