Phaco complications

Published on 08/03/2015 by admin

Filed under Opthalmology

Last modified 08/03/2015

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CHAPTER 19 Phaco complications

Local anesthesia

Needle injury

Any needle can damage an extraocular muscle, perforate the globe or, if it is long enough, enter the optic nerve via the intraconal space. High risk orbital apex injections have now largely been abandoned and superceded by safer topical, peribulbar, and subTenon’s anesthesia. Consequently subarachnoid infiltration and brainstem anesthesia are almost unheard of today. The incidence of single penetration or double perforation with peribulbar anesthesia is less than 1 in 20002 but increases to around 1 in 150 with larger myopic eyes3. If a short disposable sharp 25 mm needle is used and the surgeon is familiar with the anatomy of the orbit then it is difficult to inadvertently enter a normally sized eye without adequate warning signs. First, you will meet with a significant increase in resistance to the passage of the needle as you tangentially catch the sclera. This is often associated with some pain. However the key sign is that the impaled eye rotates with advancement of the needle. If any of these three things happen then stop, withdraw, and enter more peripherally with the needle directed parallel with the orbital wall.

If it is suspected that the needle has penetrated full-thickness then the surgeon needs to carefully examine the peripheral retina or ask a vitreoretinal colleague to do so before proceeding. The retinal holes in such cases are usually small and often self-sealing, although prophylactic retinopexy is usually applied.

Incisions

Problems with wound construction and architecture are fairly common as a reproducibly ‘perfect’ incision is difficult to achieve. The ‘Rule of Too’s’ describes most of the root causes: too short, too long, too wide, too narrow, too central, too peripheral, too superficial, or too deep.

If it is too short then intraoperative wound leakage with chamber instability will be a problem, as well as an increased risk of iris prolapse and a leaking wound at the end that requires suturing. It will be clear from the start that there is a problem and the best option is to suture the wound and make a better incision at a different site.

A peripheral wound will have breached the conjunctival insertion and is therefore prone to progressive conjunctival ballooning. This leads to fluid pooling on the cornea with resulting poor visibility from distortion and reflections. This is best resolved by extending the conjunctival incision and retracting the back edge of the conjunctiva so that the incisional outflow is no longer sequestered into the subconjunctival space. Firmly massaging already ballooned conjunctiva with a squint hook effectively disperses excess fluid.

Wounds that start peripherally also usually enter the chamber peripherally, so they are additionally prone to iris prolapse. Best to reposit the iris, suture the wound, and make a new incision.

A wound that is too long or too central makes the rhexis difficult and usually undersized as well as eccentric. It also leads to corneal distortion when pointing the phaco tip downwards (so-called ‘roofing’) causing impaired visibility. Such distortion can even tear the back edge of the roof of the incision. A long wound as well as a narrow one will increase the likelihood of a corneal burn, despite modern power modulations such as pulse, burst, and torsional modes. Most significant wound burns result in tissue contraction and wound-gape and need a mattress suture to close them on the table, which may be difficult. The majority will settle over subsequent weeks with conservative management on topical steroids and antibiotic cover. Very rarely scleral patching may be required.

A small dehiscence of Descemet’s membrane related to the internal front edge of the main wound is fairly common. This produces a hinged flap which spontaneously falls back into place and is of no consequence. A larger flap can, on most occasions, be persuaded to lie flat again. If not then an air bubble, SF6 gas, viscoelastic, or rarely suturing have all been used to successfully re-attach hanging flaps. The problem arises when a sizeable flap is stripped off and then completely detaches, never to be seen again. This is rare. The defect is usually triangular in shape with its base the width of the incision and its apex towards the center of the cornea (Fig. 19.2). Nothing to do here except wait and see how well the remaining endothelial cells respond to the greater demand on them. If over one fifth of the endothelium is gone then grafting is likely to be needed. Wait at least 3 months before considering endothelial grafting since slow recovery is the usual course with smaller defects.

When using scleral tunnels caution is needed to avoid cutting the groove too deep otherwise the choroid and suprachoroidal space can be exposed. The sclera should be sutured and a new site used. Scleral tunnels also carry a risk of tunnel hemorrhage, which occurs in up to 10% of such incisions. These are usually obvious at the time of surgery but can be delayed and associated with large postoperative hyphemas. Hemorrhage can be limited by rapid tamponade using viscoelastic. Fastidious hemostasis at the time of surgery is mostly successful in avoiding further problems.