Ординатура / Офтальмология / Учебные материалы / Vitreo-retinal Surgery Springer

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inoculated microbes and the patients’ immune state. Under unfortunate clinical conditions those phases will develop faster and the destructive power of the inflammation will be stronger.

the virulence of the pathogen the earlier and the more serious the inflammatory response.

6.1.2.1.1 Incubation Phase

The first step of exogenous endophthalmitis after cataract surgery is clinically unapparent and develops in the earliest postoperative period. It lasts at least 16–18 h even in patients with highly virulent pathogens. The generation time of the microbes is the main determinant for the duration of this phase.

6.1.2.1.3 Destructive Phase

Destruction of retinal tissue is the catastrophic injury eventually leading to the bad functional outcome of endophthalmitis. The cytotoxic properties of some microbes, as well as the inflammation itself, may lead to substantial disorganization and necrosis of the retina [14, 18, 26]. If this phase of endophthalmitis is reached, the chance of successful treatment will diminish rapidly.

6.1.2.1.2 Acceleration Phase

Dependent on the inoculated number and virulence of the microbes, endophthalmitis becomes symptomatic by breakdown of the blood–aqueous barrier. Increasing inflammatory reactions cause fibrin exudation and leukocyte migration into the anterior chamber and vitreous. These signs are predominantly accompanied by individual symptoms like visual loss and pain. The higher

6.1.3 Clinical Diagnosis

Most of the patients with acute endophthalmitis after cataract surgery become symptomatic between 1 day and 2 weeks after surgery. Reduced vision after initially good visual acuity is present in virtually all of these cases [10, 35]. Table 6.1 lists the most important clinical signs arranged by their incidence. Figure 6.2 gives a representative illustration of acute postoperative endophthalmitis.

6.1.3.1 Role of Ultrasonography

In the case of opaque media, ophthalmic ultrasound may give valuable information about the clinical situation of the posterior segment in acute endophthalmitis. A recent ultrasonographic study of 137 eyes suggested that some echographic parameters might help to assess the functional outcome of infectious endophthalmitis [5]. There was a positive correlation between poor visual outcome and the presence of dense vitreous opacities and choroidal detachment. Furthermore, the authors found an association between the grade of vitreous opacity, choroidal detachment, and the causative group of bacteria. Longitudinal examination by ultrasound may also be useful to follow treatment effects and to decide whether additional therapy is needed in due course. The different echographic appearance of diverse microbes is illustrated in Figs. 6.3 and 6.4.

Gram-positive bacteria cause by far the most cases of acute endophthalmitis after cataract surgery. The number of Gram-negative cases is decreasing and current data suggest an incidence of considerably less than 10% [11]. A survey of studies investigating the microbiologic aspects of postoperative endophthalmitis reveals that co- agulase-negative staphylococci represent about half of all culture-positive acute endophthalmitis cases, followed by Staphylococcus aureus and β- hemolytic streptococci [1, 9, 11]. Figures 6.5–6.7 give an idea of the microbiologic view of endophthalmitis.

The frequent use of antibiotics in medicine has led to growing resistance of pathogens [17]. In endophthalmitis, bacteria have become increasingly resistant to ciprofloxacin and cefazolin, a tendency that may be caused by the growing preoperative use of fluoroquinolones [22].

6.1.4 Microbial Spectrum

If a vitreous tap is taken, up to two-thirds of all cultures are expected to be positive and only in those cases is exact antibiotic therapy possible [12]. Hence, comprehensive information about the spectrum of microorganisms causing postsurgical endophthalmitis is necessary for the selection of appropriate antibiotic cocktails.

Summary for the Clinician

■After cataract surgery the presence of bacteria in the anterior chamber is common.

■Postoperative endophthalmitis is rare and is maintained by surgical technique and patient-related risk factors.

■Visual loss in the early postoperative period is a warning symptom for endophthalmitis, even in the absence of pain.

Fig. 6.3 Ocular echography of acute enterococcus endophthalmitis. Consecutive B-scans (10-MHz probe) of an eye with acute endophthalmitis due to enterococcus species within 2 days of phacoemulsification with IOL implantation are shown. Top: on echography several hours after the onset of symptoms severe intravitreal infiltrates and thickening of the choroidal layer are visible. Note that there is a “T-sign” due to increased fluid in the sub-Tenon space, which indicates the beginning of panophthalmitis. Middle: 1 day later the situation has worsened in spite of intravitreal antibiotics. There is major thickening of the choroid and the beginning of retinal detachment. Bottom: 5 days later diffuse panophthalmic infiltration is present despite a second intravitreal injection of specific antibiotics (courtesy of Dr. A.M. Verbeek, Nijmegen)

Fig. 6.4 Ocular echography of acute staphylococcus epidermidis endophthalmitis. Consecutive B-scans (10-MHz probe) of an eye with acute endophthalmitis because of Staphylococcus epidermidis are presented. a The initial echographic situation 3 days after phacoemulsification with IOL implantation shows moderate intravitreal membranes and infiltrates. b Four days later the situation has improved after a single intravitreal injection of ceftazidime and vancomycin. Note that the initial choroidal thickening has disappeared (courtesy of Dr. A.M. Verbeek, Nijmegen)

Summary for the Clinician

■T he onset of symptoms mainly depends on the generation time of the causal microbe.

■About one-third of all vitreous taps in endophthalmitis remain culture-nega- tive.

■The predominant microbes in endophthalmitis after cataract surgery are Gram-positive bacteria and among these, coagulase-negative staphylococci are the most common.

■The frequent preoperative use of antibiotics has led to growing bacterial resistance.

6.2 Therapeutical Approaches

6.2.1 Basics

When the diagnosis endophthalmitis has been made a medical emergency is present and the next diagnostic and therapeutic steps do not permit any delays. We strongly advise carrying out a vitreous tap and injecting antibiotics into the vitreous cavity within less than an hour of the clinical diagnosis. Only adequate treatment in the early hours of the disease may protect the eye from substantial inflammation of the posterior segment and might limit toxic bacterial damage.

To allow a specific treatment of the causal microbe it is important to obtain vitreous for Gram staining, microbial culture, and an antibiogram before the instillation of antibiotics. It is therefore essential to perform a vitreous tap immediately, independent of the availability of an operation theater or a specialized vitreoretinal surgeon. We advise against an anterior chamber puncture only, as pathogen identification from anterior chamber specimens is less successful. Corneal or conjunctival swabs are useless as well, as there is no convenient correlation between microbes found in those swabs and pathogens causative of the accompanying endophthalmitis [2, 31].

It is helpful to cooperate with a microbiologist to get reliable microscopy results of Gramstained vitreous specimens within an hour. After

24 h the first findings of the microbiological cultures are available and antibiotic sensitivity testing is achievable within 6–48 h, depending on the method used [21]. Equal microbiologic results can be expected by samples obtained by a vitreous cutter or by needle aspiration [13].

6.2.2 Early Pars Plana Vitrectomy

Since the results of the Endophthalmitis Vitrectomy Study [10] have been published it has generally been believed that immediate pars plana vitrectomy (PPV) is not advantageous over simple intravitreal administration of antibiotics. However, some surgeons still prefer early PPV, possibly together with extraction of the intraocular lens implant, in the case of endophthalmitis af ter cataract surgery. Early PPV supports the ancient surgical principle of relieving an abscess immediately (“Ubi pus, ibi evacua”). On the other hand, vitreoretinal surgery in the severely inflamed endophthalmitis eye includes a number of significant risk factors.

First, there will be bad visibility caused by fibrin, cells, pus, synechia, corneal edema, and vitreous haze. Good visibility of the intraocular structures is crucial for safe PPV with a favorable surgical outcome. If PPV is performed early in endophthalmitis subtotal vitrectomy has to be achieved, which cannot be done safely with poor retinal visibility.

Second, the retina in cases of endophthalmitis is very fragile and possibly necrotic. Even though in the Endophthalmitis Vitrectomy Study retinal detachment in the vitrectomy group was as frequent as in the no vitrectomy group [8], in study patients no posterior vitreous separation and only a limited vitrectomy of “at least 50% of the vitreous” were carried out. In contrast, a PPV fulfilling the intention of total abscess removal with vitreous separation and shaving will probably lead to retinal tear formation and subsequent retinal detachment.

Third, in heavy inflammation like endophthalmitis the choroid is thickened and the ocular blood f low is increased. Together with poor visibility the latter enlarges the risk of choroidal detachment, sub-choroidal infusion and severe hemorrhages during surgery.

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all over the world have been divided into two camps: those who avoided early vitrectomy and those who claimed the obligation of immediate complete pars plana vitrectomy. Even though recent peer-reviewed literature includes numerous publications on the treatment of postoperative endophthalmitis, none of the papers offers a prospective, randomized study of modern, complete pars plana vitrectomy versus vitreous tap and intravitreal antibiotics only.

Most patients with acute postoperative endophthalmitis will present in the phase of exponential bacterial growth (n×2t) when bacteria will duplicate per time unit. That means, the earlier antibiotics are administered the less bacteria will be present in the eye and the more ef fective the antibiotic treatment will be. Intravitreal injection of potent antibiotics is the most ef fective way of reaching the greatest concentration of therapeutics in the eye. In addition, the simple surgical procedure of a pars plana injection af ter a vitreous tap can be performed as an office procedure, which guarantees rapid performance without time loss.

6.3.4.2 Results in Our Department

We analyzed 83 eyes of 83 patients treated in our department for acute infectious endophthalmitis following phacoemulsification between 1 January 1998 and 31 December 2004. All eyes had initial diagnostic vitrectomy and all were administered intravitreal antibiotics (vancomycin and ceftazi-

dime) immediately, as described earlier. In 29 eyes (35%) intravitreal prednisolone was injected according to the physician’s preference. Immediate three-port pars plana vitrectomy was not performed in any of the patients. If necessary, a second and third intravitreal injection of antibiotics was given, depending on the clinical course and bacterial sensitivity testing. All patients with positive microbiological testing had bacterial infections, and none had a fungal infection.

Pathogens could be cultured from the vitreous taps of 56 out 83 patients (67.5%), 52% of which were coagulase-negative staphylococci, 21.5% were streptococci, and 14% Staphylococcus aureus. Other pathogens found were Pseudomonas aeroginosa, Enterococcus faecalis, Achromobacter xylosoxidans, and Haemophilus influenzae. Streptococci (45.5%) were the most frequently found bacteria in eyes with bad visual outcome, followed by Staphylococcus aureus (27.3%).

There was a trend toward better visual recovery if the bacterial culture was negative; however, the difference was not statistically significant. Diabetes mellitus and the intravitreal administration of prednisolone did not appear to have a significant impact on the final visual outcome. The mean course of visual acuity in our patients is shown in Fig. 6.10. In our series, 59% of all patients gained a useful final visual acuity of 20/40 or more and 18% of all eyes ended up with 20/200 or less. In 21.7% of the eyes pars plana vitrectomy was performed in due course to treat vitreous floaters. Detailed clinical data on our patients are listed in Table 6.2.