4 Small Pupil Recognition and Management The prevalence of visual impairment secondary to cataract increases with age and is expected to grow dramatically in the coming decades due to increased life expectancy and population growth. Intraoperative lens replacement for cataract extraction and intraocular lens (IOL) implantation are the most common surgical procedures performed worldwide. Sufficient mydriasis during cataract surgery is imperative for a favorable outcome, thus providing good visualization of the lens structures, adequate space for surgical instruments and manipulations, and good red reflex. Pupil dilation is usually achieved by preoperative topical application of mydriatic agents.1,2 Many patients who present for cataract removal surgery have small pupils that do not adequately dilate despite several pharmacological attempts with topical mydriatic agents. Additionally, in some patients the initial mydriatic effect achieved may not last throughout the surgery, especially in patients who are treated with systemic α1-adrenergic antagonist medications and in cases of surgical trauma that may induce intraoperative miosis through prostaglandin-related stimulation of the iris,2–4 Inadequately dilated pupil might complicate and challenge surgery. The causes of small pupil are numerous and include iris sphincter sclerosis from aging, pseudoexfoliation, posterior synechiae, previous trauma or surgery, diabetes, chronic syphilis, iridoschisis, uveitis, chronic miotic therapy, and systemic α1-adrenergic antagonists medications for the treatment of lower urinary tract symptoms of benign prostatic hyperplasia (BPH).3 There is no strict definition of what is considered a small pupil. In practice, for the inexperienced surgeon a 4.0 to 5.0 mm is considered small, whereas an experienced surgeon may consider a pupil as being constricted only if the diameter is 3.5 to 4.0 mm or smaller. Small pupils may entail risks at any step of surgery, from capsulorrhexis and lens particle removal to cortical aspiration and IOL implantation. If the pupil is not adequately dilated, surgeons tend to create a capsulorrhexis smaller than desired, which may further complicate surgery due to intraoperative difficulty in extracting nuclear fragments from within the capsular bag, and increased risk of postoperative capsule phimosis. Pseudoexfoliation (PXF) is the most common cause of small pupil during cataract surgery. PXF is an age-related abnormal fibrillopathy that has been linked to the lysyl oxidase-like 1 (LOXL1) gene. It is characterized by the gradual synthesis, accumulation, and deposition of exfoliation material in the anterior segment of the eye and other tissues in the body.5 PXF is associated with an increased incidence of cataract formation, including nuclear and subcapsular opacities.6–8 It is estimated that 60 to 70 million people worldwide are affected by PXF. Prevalence of PXF increases with older age,9 and it varies among geographic regions. In cataract surgery patients, the PXF prevalence ranges from 0.4% in the Chinese10 up to 30.2% in the Estonian population.11 Besides a nondilating pupil, PXF is often associated with weakened zonules and phacodonesis, which may further complicate surgery. The influence of PXF on cataract surgery has been considerably documented. Earlier studies report a five- to 10-fold increased risk for surgical complications in eyes with PXF versus non-PXF eyes undergoing cataract surgery.5,12,13 However, more recent studies report this difference to be smaller using technique modifications and devices.14,15 Favorable outcomes can be achieved in cataract surgery in PXF syndrome as reviewed by Shingleton et al.16 Another common cause of small pupil or miosis during cataract surgery is intraoperative floppy iris syndrome (IFIS). Chang and Campbell3 first described it in 2005 as occurring in 2% of cataract surgery patients, and Chang et al17 further reviewed the topic in 2008. The syndrome is characterized by the following intraoperative triad: (1) a floppy iris that billows in response to normal irrigation in the anterior chamber; (2) a marked propensity for the floppy iris stroma to prolapse toward and into the corneal incisions; and (3) a progressive pupillary constriction during surgery. The syndrome has been documented to occur in patients with BPH treated with systemic α-antagonists in general and tamsulosin (Flomax, Boehringer-Ingelheim Pharmaceuticals, Ridgefield, CT) in particular. A recent retrospective study reported that 86% of the patients using tamsulosin had IFIS compared with 15% of those using alfuzosin (Uroxatral; Sanofi-Aventis, Bridgewater, NJ).18 These findings are supported by those of a recent meta-analysis that found the risk of IFIS to be 16.5- to 40-fold higher in cases of previous tamsulosin use when compared with alfuzosin.19 During cataract surgery, IFIS can lead to many complications such as significant progressive pupil miosis, iris stromal atrophy, iris prolapse, capsulorrhexis tear, rupture of the posterior capsule, loss of lens material into the vitreous cavity, and others.1,19–21 Patients with poor pupillary dilation should be questioned about the use of αla-adrenergic antagonists. Cessation of the drug before surgery may reduce the risk of IFIS. However, IFIS may still develop after patients discontinue systemic αla-adrenergic antagonist medications.22 Overall, it appears that discontinuation of tamsulosin preoperatively is of unpredictable value and does not reliably prevent IFIS or reduce its severity. Small pupil was reported in 1 to 11% of cataract operations, and varies by location and by definition of the term. IFIS was shown to occur in ∼ 2% of men, and much less in women. The overall incidence of small pupil is probably around 3 to 5% of cataract operations. This may sum up to an annual rate of 150,000 cases in North America or Europe and probably more than 500,000 operations per year worldwide. The small pupil can be dilated pharmacologically or mechanically. Preoperative topical nonsteroidal anti-inflammatory drugs (NSAIDs) in combination with mydriatic agents may help to reduce intraoperative miosis.4,23,24 Srinivasan and Madhavaranga4 compared the effect of preoperative treatment of topical ketorolac tromethamine 0.5% solution and topical diclofenac sodium 0.1% solution on the inhibition of surgically induced miosis. Topical ketorolac was found to be a more effective inhibitor of miosis than topical diclofenac during extracapsular cataract extraction and IOL implantation. It also provided a more stable mydriatic effect throughout surgery. A recent prospective study evaluated intracameral phenylephrine and ketorolac injection (Overutilization Monitoring System [OMS]302) for maintenance of intraoperative pupil diameter compared with placebo during IOL replacement.25 OMS302 was superior to placebo in maintaining mydriasis and preventing pupil miosis. Experienced surgeons often opt to perform surgery through a relatively small pupil in spite of limited visualization. However, the challenging surgery is often associated with an increased risk of iris and sphincter tears, bleeding, iris emulsification, ruptured posterior capsule, dropped nucleus or lens particles, and vitreous prolapse. Alternatively, surgeons may mechanically dilate the constricted pupil using a variety of instruments such as iris dilators and spatula. This is especially useful in cases of fibrotic pupillary membrane or posterior synechiae in posttraumatic or postuveitic constricted pupil. A fibrotic band at the pupillary margin may occasionally be stripped off using intraocular forceps to enable the pupil to properly dilate, but the sphincter function of the pupil is typically lost. The Beehler pupil dilator has three microfingers with iris hooks and an additional hook on the tube. It is inserted into the anterior chamber through the main clear corneal incision, and the pupil is stretched in four quadrants. After the pupil is fully stretched, the prongs of the Beehler instrument are retracted, and the instrument is removed from the eye (Fig. 4.1). Multiple iris sphincter tears with scissors, creating partialthickness sphincterotomies, is effective in cases of fibrotic pupil. Many surgeons abandoned this technique because of postoperative aesthetically and functionally unacceptable iris irregularities. This technique is not effective in functional miosis such as IFIS and may actually aggravate pupil constriction. Ophthalmic viscosurgical devices (OVDs) play an important role in managing the small pupil. An OVD with dispersive qualities is helpful to adequately coat the cornea during surgical maneuvers to protect the corneal endothelium. It may also help to create compartmentalization and prevent sucking a flail iris into the phacoemulsification tip. On the other hand, highly cohesive OVDs are very important for space maintenance, separation of posterior synechiae, and viscodilation of the pupillary margin. A combination of both cohesive and dispersive OVDs, such as the “soft shell” technique or using a “viscoadaptive” OVD, provides the advantages of both materials (see Chapter 33). As initially reported by Chang and Campbell,3 partial-thickness sphincterotomies and mechanical pupil stretching are ineffective for IFIS and may exacerbate the condition and therefore are not recommended. Many surgical strategies have been proposed to minimize the occurrence and the severity of IFIS with variable success. Among them are the use of atropine,26,27 intracameral epinephrine,27,28 iris retractors,29 dilator rings,30–32 and OVDs.32,33 Employment of highly retentive OVDs such as Healon 5 (Abbott Medical Optics, Abbott Park, IL) to viscodilate the pupil and maintain a concave iris near the incisions without preventing egress of irrigating fluid and use of low-flow settings and lens removal techniques can minimize anterior chamber turbulence (see Chapter 23).
Managing the Small Pupil
Intraoperative Floppy Iris Syndrome Management
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