Exogenous endophthalmitis initially treated without systemic antibiotics

Consensus and controversies in the science of endophthalmitis management: Basic research and clinical perspectives

Infectious endophthalmitis is a severe intraocular infection caused by bacteria, or less commonly by fungi. It can occur after penetrating eye procedures, trauma, or the spread of infection from contiguous structures or via emboli from distant organs. Because of the time-critical nature of the treatment, endophthalmitis is treated with the clinical diagnosis and modified by the microbiological report of the intraocular contents. The current strategy for managing endophthalmitis relies on pre-clinical literature, case series, and one large multi-center randomized clinical trial on post-cataract surgery endophthalmitis. Culture-susceptibility of the microorganisms from undiluted vitreous guides the definitive treatment in non-responsive cases. Strategies to reduce the incidence of endophthalmitis after penetrating eye procedures have been developed concurrently with refined means of treatment. Despite these advances, outcomes remain poor for many patients. Although consensus articles have been published on managing endophthalmitis, treatment patterns vary, and controversies remain. These include (1) the use of newer methods for early and precise microbiological diagnosis; (2) the choice of intravitreal antibiotics; (3) the need for systemic therapy; (4) early and complete vitrectomy. Here, we review the current consensus and address controversies in diagnosing and managing endophthalmitis. This review is intended to familiarize physicians and ophthalmologists with different aspects of endophthalmitis management to make informed decisions.

Intraocular Foreign Bodies: Myths and Truths

Over the centuries, the management of eyes with intraocular foreign bodies (IOFB) has posed a special challenge to the physician, and the anxiety created by such injuries has never abated. During the past few decades, several new diagnostic tests, IOFB removal techniques, and methods to treat the complications of the injury have been introduced. Nevertheless, old habits die hard: many of the management options that used to be standard are not appropriate any more but have proved difficult to change. This article reviews over forty of these die-hard myths and confronts them with factual statements published in the peer-review international literature.

Ocular microdialysis: a continuous sampling technique to study pharmacokinetics and pharmacodynamics in the eye

The unique anatomy and physiology of the eye present many challenges to the successful development and delivery of ophthalmic drugs. Any therapeutic strategy developed to control the progression of anterior and posterior segment diseases requires continuous monitoring of effective drug concentrations in the relevant ocular tissues and fluids. Ocular microdialysis has gained popularity in recent years due to its ability to continuously monitor drug concentrations and substantially reduce the number of animals needed. The intrusive nature of ocular microdialysis experimentation has restricted these studies to animal models. This review article intends to highlight various aspects of ocular microdialysis and its relevance in examining the disposition of drugs in the anterior and posterior segments.

Orbital cellulitis and endophthalmitis in pseudomonas septicemia

We report a case of concurrent orbital cellulitis and endophthalmitis that resulted from endogenous complications of community-acquired Pseudomonas aeruginosa bacteremia in an apparently healthy individual. Pseudomonas pneumonia and extensive focal skin lesions of ecthyma gangrenosum also complicated the condition. The presence of drug-induced neutropenia was a risk factor in this patient. Simultaneous orbital cellulitis and endophthalmitis developed and rapidly progressed. Intravenous, intravitreal, and topical antibiotics were administered along with frequent eye wash with normal saline to dilute copious purulent discharge from a deep subcutaneous abscess of lower eyelid. Because of the exocellular products of Pseudomonas aeruginosa, the sclera and corneal stroma were degraded, resulting in nearly perforated cornea. Tarsoconjunctival flap from the upper eyelid was performed to reconstruct the thinning areas. After the infection was controlled, the patient's ultimate visual acuity was light perception.

SUBCONJUNCTIVAL ANTIBIOTICS IN THE TREATMENT OF ENDOPHTHALMITIS MANAGED WITHOUT VITRECTOMY

PURPOSE

To determine if the treatment outcomes for endophthalmitis are influenced by subconjunctival antibiotics.

METHODS

A retrospective, nonrandomized consecutive series of patients with clinically diagnosed bacterial endophthalmitis confirmed with positive cultures who presented between December 1, 1995, and February 28, 2002, was studied. Patients with cataract surgery, glaucoma filtering blebs, or trauma who presented with visual acuity of hand motions or better were included. All patients received intravitreal and topical antibiotics. Management by pars plana vitrectomy or vitreous tap and use or nonuse of subconjunctival antibiotics were at the discretion of the treating physician.

RESULTS

There were 59 patients identified; 54 met the follow-up criteria. These patients were divided into two groups based on whether subconjunctival antibiotics were used (group ABX; n = 21) or not used (group noABX; n = 33). The median pretreatment visual acuity was hand motions in both groups. The median age in both groups was 74 years. Etiology, duration of symptoms, vitreous culture organisms, percentage of cases with wound complications such as leaks or vitreous incarceration, and intraocular lens type were similar in the two study groups. Intravitreal and topical antibiotics and corticosteroids used were not significantly different in the two groups, except that topical ceftazidime was used less frequently in group ABX than in group noABX (43% vs. 82%, respectively; P = 0.007). The median follow-up was 13 months in both groups (range: 3-87 months for group ABX and 3-63 months for group noABX). Final visual acuity in groups ABX and noABX was at least 20/50 (33% vs. 39%, respectively), 20/60 to 5/200 (29% vs. 39%, respectively), 4/200 to better than hand motions (0 vs. 3%, respectively), or hand motions or worse (38% vs. 18%, respectively). These differences were not significant (P = 0.37). Reinjection rates (14% vs. 15%, respectively) were also similar in groups ABX and noABX. The additional procedures rate was significantly higher in group ABX than in group noABX (P = 0.024), with cumulative rates of 33% and 3%, respectively, at the 12-month follow-up.

CONCLUSIONS

These data suggest that subconjunctival antibiotics may not be necessary to treat infectious endophthalmitis managed with otherwise standard tap and injection techniques and topical antibiotics.

Ocular pharmacokinetics in rabbits using a novel dual probe microdialysis technique

Ocular infections involve delicate internal structures of the eye that often require treatment with antimicrobial agents. A major constraint to the study of ocular drug absorption from systemic administration is the inaccessibility of the vitreous for continuous serial sampling. A novel dual probe microdialysis technique has been employed in our laboratory, which will enable the delineation of complete ocular pharmacokinetics of a drug. New Zealand albino rabbits weighing 2--2.5 kg were used. The animals were kept under anesthesia throughout the experiment. A concentric probe was implanted in the vitreous chamber about 3 mm below the corneal scleral limbus. Simultaneously a linear probe was implanted in the anterior chamber across the cornea. Intraocular pressure (IOP) was measured using Schiotz tonometer. The total protein concentrations in the aqueous and vitreous humors were determined using the Bio-Rad protein assay method. The aqueous and vitreous elimination kinetics of fluorescein were studied after intravitreal and systemic administrations over a period of 10 hr. Microdialysis technique was also compared to the conventional direct sampling technique by determining the intravitreal kinetics of fluorescein. Results suggest that IOP reverted to normal within 2 hr after the implantation of the probes. The increase in the vitreal total protein concentration was not significantly different from the baseline. The increase in the aqueous total protein concentration was less than five times the basal concentration throughout the experiment. The blood-aqueous and blood-retinal barrier integrity was delineated by determining the permeability index for fluorescein and were found to be 9.48 +/- 4.25% and 1.99 +/- 0.66% for the anterior and vitreous chamber, respectively. The rate constant of penetration of fluorescein into the anterior chamber was found to be 8.48 +/- 1.33 x 10(-2) min(-1), which was significantly higher than into the vitreous i.e. 4.34 +/- 2.82 x 10(-2) min(-1). The terminal elimination rate constant of fluorescein from the anterior chamber (1.48 +/- 0.79 x 10(-2) min(-1)) was found to be similar to that of the plasma terminal elimination rate constant (1.57 +/- 0.25 x 10(-2) min(-1)), but significantly higher than from the vitreous (3.0 +/- 0.7 x 10(-3) min(-1)). The terminal vitreal elimination rate constant of fluorescein after intravitreal administration was found to be similar by both microdialysis (3.98 +/- 0.6 x 10(-3) min(-1)) and direct sampling (4.38 +/- 1.4 x 10(-3) min(-1)) techniques. In case of direct sampling technique the area under the vitreous concentration-time curve was higher compared to that obtained by the microdialysis technique. There was no breakdown of the blood ocular barriers as shown by a very small change in the intraocular fluid protein concentrations. This was also confirmed by the fluorescein kinetics, which were in accordance with the previous studies. IOP data suggests that the intraocular fluid dynamics were not affected and the animals stabilized within 2 hr after the implantation of the probes. Fluorescein data suggests that the vitreous compartment is surrounded by a tighter barrier compared to the anterior chamber. This technique appears to be more sensitive, reproducible and requires only one animal for the determination of entire ocular pharmacokinetic profile.

Pharmacokinetics of 0.5 mg of a single and a multiple dose of intravitreal vancomycin in infected rabbit eyes

The purpose of this study was to determine the pharmacokinetics governing distribution and elimination of 0.5 mg of intravitreal vancomycin in a single dose and in a multiple therapeutic regime in infected rabbit eyes. A total of 96 rabbits was injected with approximately 200 CFU of S. aureus intravitreally. Four days later, a single dose of 0.5 mg of vancomycin was administered to Group I (n=36). Group II (n=60) was injected with a maximum of 4 doses of 0.5 mg every 36 hr. Four animals were sacrificed at different time points in each group. Samples of vitreous, aqueous and blood were taken from each animal for analyses by HPLC. These results were evaluated using the RSTRIP program. High vancomycin concentrations were demonstrated in the vitreous of Group I, with a calculated half-life of 12 hr. In Group II, vancomycin levels were within the therapeutic range during the entire experiment. There was minimal accumulation of the drug, and the half-life did not seem to be longer with multiple doses. In conclusion, the pharmacokinetics do not change significantly when a multidose regime is used compared with a single dose. Therapeutic intravitreal concentrations of vancomycin can be achieved by using repeated doses of 0.5 mg of vancomycin.

Controversies in the management of open-globe injuries involving the posterior segment

There are numerous unresolved issues and controversies regarding the management of open-globe injuries involving the posterior segment. These areas include, but are not limited to, the following issues. Although vitrectomy has been shown to improve visual outcomes and allow retention of the eye in many cases, the extent of visual improvement is often limited because of the nature of the injury. Timing of vitrectomy surgery has been and will continue to be debated by proponents of early versus delayed intervention. The multiple features of acute ocular injury make it very difficult to interpret retrospective data regarding the most appropriate timing for surgical intervention. The use of prophylactic cryotherapy, in the setting of a scleral laceration with possible retinal damage, is not as controversial at present, as there is now sufficient data indicating that cryotherapy may actually exacerbate intraocular proliferation and worsen the situation. The role and benefit of a prophylactic scleral buckle is very widely contested, and it is not known if it truly decreases the risk of subsequent retinal detachment. Another area of debate centers on the use of antibiotics. When there is a known clinical infection, intravitreal antibiotics are the mainstays of therapy. However, in the absence of clinical infection, the use of prophylactic antibiotics and their routes of administration are quite controversial. Although there are significant data regarding the use of antibiotics in the postoperative setting, this information cannot be extrapolated into the setting of open-globe injuries, as organisms and virulence factors differ. Similarly, the use of vitrectomy versus vitreous tap in the setting of traumatic endophthalmitis is not fully resolved, although vitrectomy is used in most cases to repair concurrent damage from the injury itself. Finally, the placement of intraocular lenses in the acute trauma setting is controversial, as the risk of complications is quite high. Prospective, controlled clinical studies have not been done. This article reviews pertinent data regarding these management issues and controversies, and provides recommendations for treatment based on the available published data and the authors' personal experience.

Presumed noninfectious endophthalmitis after cataract surgery

PURPOSE

To study the clinical features and results of conservative management in cases of presumed noninfectious endophthalmitis after cataract surgery.

SETTING

L.V. Prasad Eye Institute, Hyderabad, India.

METHODS

This retrospective study evaluated cases of presumed noninfectious endophthalmitis occurring after cataract surgery in a hospital-based population. Patients with minimal hypopyon and decreased visual acuity unassociated with pain, lid edema, conjunctival chemosis, corneal abscess, and obvious vitreous involvement were treated conservatively. The mainstays of treatment were topical and systemic steroids. Four eyes with clinical evidence of worsening required surgical intervention. Main outcome measures were resolution of inflammation and final visual acuity.

RESULTS

In 23 of 27 patients, the inflammation resolved with medical therapy alone; 21 had a final visual acuity of 20/50 or better. In 3 of the 4 eyes that had surgery, the culture was positive for low virulent organisms; all had a satisfactory outcome. One eye with preoperative glaucoma developed absolute glaucoma with resolution of inflammation.

CONCLUSION

Noninfectious endophthalmitis invariably presents with hypopyon and decreased vision unassociated with pain and lid edema. A trial of medical therapy with corticosteroids as the mainstay of treatment is often rewarding. Frequent monitoring and preparation for surgical intervention if required are key.

Aminoglycoside levels in the rabbit vitreous cavity after intravenous administration

PURPOSE

To determine the penetration of gentamicin and amikacin into the rabbit vitreous cavity after their intravenous administration.

METHODS

Gentamicin (1.6 mg/kg every 8 hours) and amikacin (6 mg/kg every 12 hours) were administered intravenously to 25 rabbits that had previously had the lens and vitreous removed from 43 eyes. For each drug, ocular inflammation was induced in one group of eyes by injection of heat-killed Staphylococcus epidermidis, while the other group was maintained as a control. Samples from the vitreous cavity were taken at regular intervals for 72 hours after beginning the intravenous medications and were analyzed for drug concentrations.

RESULTS

The maximum intravitreal concentration +/- SD achieved for gentamicin was 1.8 +/- 0.5 microgram/ml. The maximum intravitreal concentration for amikacin was 8.5 +/- 3.2 micrograms/ml. Inflamed eyes demonstrated higher concentrations than did those without inflammation.

CONCLUSIONS

In a rabbit model with conditions optimized to enhance penetration of antimicrobials into the vitreous cavity after intravenous administration, neither gentamicin nor amikacin penetrated sufficiently to reach potentially therapeutic concentrations consistently for either Pseudomonas or S epidermidis organisms.

Acute endophthalmitis outbreak after cataract surgery

PURPOSE

To evaluate the source of organisms causing an epidemic of postoperative endophthalmitis and to emphasize the importance of prompt intervention with an early diagnosis.

SETTING

S.B. Ankara Hospital Eye Department, Ankara, Turkey.

METHODS

Thirteen patients who had surgery on the same day and developed acute postoperative endophthalmitis were evaluated. Clinical patterns were observed and intraocular cultures and stains performed in 10 eyes. Broad-spectrum intravitreal antibiotics were injected on an empirical basis.

RESULTS

Intravitreal cultures showed Pseudomonas aeruginosa in four cases and coagulase-negative staphylococci in three cases; three cases were culture negative. P. aeruginosa were also isolated from irrigation solutions used on the same day. Two patients with P. aeruginosa had a visual acuity of 20/200 and 20/300, respectively.

CONCLUSION

The different culture results were probably related to the amount of inoculation, individual risk factors, and the subconjunctival antibiotic injection given at the end of surgery. That one patient with P. aeruginosa endophthalmitis retained a visual acuity of 20/200 shows the importance of rapid intravitreal antibiotic treatment.