patients will develop retinal detachment either at the time of or after the vitrectomy for the retained lens material, whereas only 2% develop retinal detachment associated with dislocated posterior chamber lens implants (Table 26–5). Possible reasons for the disparity include less inflammation with IOL dislocation relative to lens nuclear and cortical materials. Also, primary vitrectomy is often performed from the limbus at the time the lens fragment is lost, whereas with the dislocated IOL this is less usually aggressively performed. The surgical approach typically involves standard vitreoretinal surgical techniques, but perfluorocarbon liquids may be useful in selected cases to better manipulate the IOL while avoiding retinal trauma.

RECOMMENDATION FOR MANAGEMENT

OF DISLOCATED IOLS

For the anterior segment surgeon, avoiding PC IOL dislocation depends on accurate assessment of posterior capsule status intraoperatively. The anterior segment surgeon must take care to evaluate the integrity of the peripheral capsule carefully before implanting a PC IOL in the presence of a posterior capsular rupture. Generally, at least six clock hours of peripheral capsular support (including the inferior meridians) are necessary to maintain IOL positioning. Retracting the iris may be necessary to directly visualize the extent of peripheral capsular support before placing the PC IOL. Once it is determined safe to proceed with IOL placement, it is vital that the haptics are placed precisely. Viscoelastic and iris retraction (using iris hooks) may facilitate this.

Recommendations to the anterior segment surgeon encountering PC IOL dislocation intraoperatively include performing anterior vitrectomy to avoid vitreous incarceration in the wound. Postoperatively, frequent topical corticosteroids, nonsteroidal antiinflammatory drugs (NSAIDs), and, as clinically

indicated, IOP-reducing agents should be prescribed. For most cases, vitreoretinal referral for definitive management is advisable, although, as described above, some cases are best observed or may be amenable to management with limbal incisions. Careful attention is necessary to evaluate for other complications such as retinal detachment.

Recommendations to the vitreoretinal surgeon include careful assessment of existing capsular anatomy and coexisting complications to formulate a treatment plan in terms of timing and technique options. Generally, allowing a week or more for treatment and resolution of acute postoperative inflammation is advisable. The vitreoretinal surgeon should also be aware of IOL calculations from the cataract surgeon so that appropriate IOL power can be accurately selected if necessary.

POSTOPERATIVE ENDOPHTHALMITIS

Infectious endophthalmitis following ocular surgery is an uncommon clinical entity often causing severe visual loss.79 Because approximately 1.35 million cataract operations1 are performed each year in the United States, pseudophakic endophthalmitis is the most frequently encountered category in reported series. This complication is not specific to phacoemulsification or cataract surgery. Other categories of intraocular surgery may also lead to endophthalmitis but are less frequent in clinical series. Endophthalmitis after secondary IOL implantation, corneal transplant, pars plana vitrectomy, and glaucoma filtering surgery is reported less often in large series.80–82

Incidence

In a survey of postoperative endophthalmitis at the Bascom Palmer Eye Institute over a 10-year period (1984–1994), the incidence of nosocomial endophthalmitis was reported83 (Table 26–6). The incidence of endophthalmitis after penetrating ocular trauma

TABLE 26–6 INCIDENCE OF ENDOPHTHALMITIS IN A 10-YEAR STUDY83 FROM THE BASCOM PALMER EYE INSTITUTE (1984–1994)

(3 to 30% of patients in reported trauma series) is much higher than in the postoperative categories.84–86 Clinical factors associated with a higher frequency of endophthalmitis include vitreous loss (cataract surgery), repeat incisions in the surgical limbus with potential poor wound healing (secondary IOL), and use of adjunctive antimetabolites (glaucoma filtering

surgery).

Clinical Diagnosis and Microbiological

Confirmation

The diagnosis of postoperative endophthalmitis is made by recognition of clinical features and by microbiologic confirmation. The clinical features of postcataract surgery endophthalmitis include marked intraocular inflammation (Fig. 26–8) often with hypopyon.79 In addition, conjunctival congestion, corneal edema, and lid edema are traditional signs associated with intraocular infection. Symptoms often include pain and marked loss of vision. Although endophthalmitis caused by less virulent organisms may have minimal or no pain, some degree of pain is still present in the majority of postoperative endopthalmi-

FIGURE 26–8 Acute-onset endophthalmitis caused by Staphylococcus aureus presenting 3 days following cataract surgery with posterior chamber implant. (From Regillo CD, Brown GC, Flynn HW Jr. Vitreoretinal Disease: The Essentials. New York: Thieme; 1999:559, Fig. 35–1.)

tis patients. The loss of vision is usually profound and out of proportion to the typical postoperative vision measured during the first days or weeks after intraocular surgery.

An attempt is made to confirm the clinical diagnosis by microbiologic growth from intraocular specimens. Vitreous specimens are more likely to yield a positive culture result than simultaneously obtained aqueous specimens.87 Many different techniques have been described for obtaining these specimens. The anterior chamber specimen is typically obtained using a syringe with a 30-gauge needle. The vitreous specimen can be obtained either by a needle tap or by a vitrectomy instrument. The needle tap technique generally employs a 22-gauge needle introduced through the pars plana and directed toward the mid-vitreous cavity. Neither a conjunctival incision nor a suture closure is necessary for the needle entry site. A small specimen (0.2 to 0.5 mL) is obtained and is directly inoculated into culture media or delivered to the laboratory without delay. If a vitrectomy instrument is utilized, the specimen may be passed through a membrane filter system to concentrate the microorganisms on the filter paper. Using sterile techniques, the filter paper sections are placed on appropriate culture media. Alternatively, freshly collected vitrectomy specimen can be injected directly into blood culture bottles for analysis by the microbiology department as growth occurs. In a reported study comparing membrane filter cultures versus blood culture bottles, similar rates of positive cultures were obtained from both culture techniques.88 At night or on the weekends when the microbiological staff are not available to process the vitrectomy specimen, the blood culture bottles are particularly useful.

The source of the infecting organisms causing postoperative endophthalmitis is generally felt to be the patient’s own flora from the lids, conjunctiva, and periocular tissues. Molecular epidemiologic techniques have demonstrated that the genetic identity of bacteria from vitreous aspirates is the same as those from eyelid or conjunctival isolates in 82% of 17 cases in one study of endophthalmitis.89 Similarly, in an analysis of 105 coagulase-negative staphylococcus endophthalmitis cases with paired isolates from the individual patient’s eyelid and intraocular compartments, pulsed-field gel electrophoresis demonstrated genetically identical organisms in 67.6%.90 These results reinforce the necessity of following stringent surgical site preparation prior to eye surgery. Many surgeons also now routinely instill half-strength Betadine (povidone-iodine 5%) solution at the beginning of an intraocular procedure to further reduce resident flora and, it is hoped, the risk of endophthalmitis.

The Endophthalmitis Vitrectomy Study (EVS) was a randomized prospective, clinical trial evaluating treatment strategies for acute-onset endophthalmitis following cataract surgery or secondary IOL surgery.91–94 The EVS compared treatment outcomes between immediate three-port pars plana vitrectomy and immediate vitreous tap/biopsy, and between the use and nonuse of intravenous antibiotics. The systemic antibiotics selected by the EVS investigators were amikacin and ceftazidime for a minimal 5-day course.

The EVS entry criteria are listed in Table 26–7. A double-randomization scheme allowed four groups for analysis: immediate three-port pars plana vitrectomy with intravenous antibiotics, immediate threeport pars plana vitrectomy without intravenous antibiotics, immediate tap/biopsy with intravenous antibiotics, and immediate tap/biopsy without intravenous antibiotics.91

The microbiologic results of the EVS showed confirmed bacteria growth in 69.3% of intraocular cul- tures.92–94 The coagulase-negative micrococci comprised 70% of the EVS isolates. Staphylococcus aureus

(9.9%), Streptococcus species (9.0%), Enterococcus species (2.2%), gram-negative organisms (5.9%), and miscellaneous gram-positive organisms (3.1%) occurred less often. All gram-positive organisms were sensitive to vancomycin, but two of the gramnegative organisms were resistant to both amikacin and ceftazidime.

The EVS treatment outcomes demonstrated no difference in final visual acuity or media clarity outcomes whether or not systemic antibiotics were employed (Table 26–8). Likewise, if the patient had hand motion or better visual acuity on the initial ex-

TABLE 26–7 ENDOPHTHALMITIS VITRECTOMY

STUDY ENTRY CRITERIA

Clinical diagnosis of endophthalmitis within 6 weeks of cataract surgery or secondary IOL

Hypopyon or clouding of anterior chamber (AC) or vitreous media sufficient to obscure clear visualization of second-order retinal arterioles

The cornea and AC were clear enough to visualize some part of iris

The cornea was clear enough to allow the possibility of pars plana vitrectomy

Visual acuity: worse than 20/50 but at least light perception

No serious coexisting diseases that might compromise visual outcomes; immediate three-port pars plana vitrectomy

No difference in final visual acuity or media clarity whether or not EVS systemic antibiotics were employed

For patients with hand motion or better vision, no difference in outcomes between immediate three-port pars plana vitrectomy and tap/biopsy

For patients with initial visual acuity of light perception (LP) only, better visual results occurred in the immediate three-port pars plana vitrectomy group (versus tap/biopsy group)

•Three times more likely to achieve 20/40 (33% vs. 11%)

•Two times more likely to achieve 20/100 (56% vs. 30%)

•Less likely to incur <5/200 (20% vs. 47%)

amination, the EVS showed no difference in these outcomes between the immediate three-port pars plana vitrectomy group and the immediate tap/ biopsy group. However, for patients with initial vision of light perception only (26% of patients in the EVS), much better outcomes occurred in the immediate three-port pars plana vitrectomy group. Using multivariate analysis, the presenting visual acuity was the single most important factor in predicting EVS outcomes regardless of the treatment group.

The EVS visual acuity outcomes can be stratified by microbiologic results.93,94 The best EVS outcomes occurred in the groups with either no or equivocal growth and in the coagulase-negative microcococci group (Table 26–9). EVS patients with gram-negative organisms had intermediate visual outcomes compared to the “other” gram-positive category (composed mainly of S. aureus and Streptococcus species), which had the poorest outcomes. These outcomes stratified by microbiologic isolates are similar to a previous report that showed visual acuity outcomes of 20/400 or better in more than 80% of endophthalmitis cases caused by the coagulase-negative staphylococci.95 Less favorable outcomes occurred in the S. aureus and gram-negative groups, but the worst outcomes occurred in the Streptococcus species group.95

Because the EVS selected amikacin and ceftazidime for systemic use, some authors have questioned whether these EVS results can be extended to other systemic antibiotics.96–98 Amikacin was selected for coverage of the gram-positive organisms but the penetration of amikacin into the vitreous cavity has been shown to be poor in an experimental model.99 Ceftazidime also has a broad coverage of gram-negative organisms but its effectiveness against gram-positive organisms is variable. Notably absent for systemic use in the EVS, vancomycin has excellent coverage of

gram-positive organisms and has been shown in an experimental model to penetrate well into the vitreous cavity.100 Orally administered antibiotics, such as ciprofloxacin, were also not evaluated in the EVS. Therefore, the EVS outcomes with systemically administered amikacin and ceftazidime may not reflect the outcomes obtained with other antibiotics currently available or potentially available in the future.

The drug dosages used in the EVS and alternative drugs recommended by the authors are listed in Table 26–10. When rapid-onset ( 2 days), endophthalmitis cases with very severe intraocular inflammation are encountered, the use of systemic vancomycin should be considered. However, no systemic antibiotics are recommended in the majority of postoperative endophthalmitis patients.

Systemic corticosteroids were used in all patients in the EVS. In the elderly post–cataract surgery pop-

ulation, the use of systemic corticosteroids may often be contraindicated because of the high prevalence of diabetes mellitus and other medical risks from the use of systemic corticosteroids. Intravitreal corticosteroids have been used as an adjunct to intraocular antibiotics in reported clinical series.95,101 The authors currently recommend intravitreal dexamethasone 0.4 mg in 0.1 mL as a part of the initial treatment in postoperative endophthalmitis.

There were 10 patients among the 420 EVS patients who developed acute postoperative endophthalmitis in spite of having used antibiotics in the irrigation solution during the cataract surgery. Because of the ineffectiveness of this approach, the risk of antibiotic toxicity, the tendency to foster the emergence of vancomycinresistant organisms, and the increased risk of CME,102 the use of irrigating solution antibiotics for routine cataract surgery is generally discouraged.103,104