Fig. 2.1
(a) Top: B-scan in endophthalmitis showing multiple low to medium reflective echoes in the vitreous cavity. Bottom–left: B-scan in endophthalmitis showing membrane-like echoes in the vitreous cavity. Bottom-right: minimal echoes on B-scan in a case of resolved endophthalmitis. (b) Top: endophthalmitis progressed to panophthalmitis with vitreous echoes and T-sign suggestive of sub-Tenon’s fluid. Bottom: endophthalmitis following open-globe injury showing a high reflective echo with posterior shadowing suggestive of a retained intraocular foreign body
Fig. 2.2
Ocular fluid collection. Left—aqueous humor collection; right: vitreous humor collection
Fig. 2.3
Left: butterfly needle. Right—vitreous humor collection using a butterfly needle and 10 ml syringe (Courtesy: Harry W. Flynn Jr., MD)
Fig. 2.4
Injection of intravitreal antibiotic into the mid-vitreous cavity
Fig. 2.5
Macular infarction after intravitreal amikacin 0.4 mg in Staphylococcus epidermidis endophthalmitis. Left—color photo shows attenuated vessels and edema of the posterior pole; right: fluorescein angiography shows nonfilling of the posterior pole arteries even in the late phase (Courtesy: Avinash Pathengay, MD)
Prior to deciding the treatment plan and discussing with the patient (and the family), one must know the following details because it could impact in decision-making:
- 1.
What is the duration between the event (surgery/trauma/systemic disease) and the manifestation? Usually virulent organisms manifest faster than less virulent infection. A chronic infection could be due to a slow-growing organism or even a fungus.
- 2.
In event of trauma, what was the scene of injury? A metal foreign body is different than a vegetative one, and a road traffic injury is different than injury in a relatively clean work place. This helps in suspecting infective organism.
- 3.
Is this bilateral? This could be endogenous in nature.
The First Management Steps
The five essential management principles in management of infectious endophthalmitis are (1) collection of ocular fluid (aqueous/vitreous) specimen for microbiological study; (2) injection of intravitreal antibiotics; (3) intravitreal corticosteroid, when required; (4) vitrectomy, when required; and (5) care of all associated eye injuries.
Collection of Ocular Fluid Specimen
The aqueous humor collection is similar to a paracentesis (Fig. 2.2 left). Following appropriate anesthesia of the eye (usually topical anesthesia) and eye surface sterilized (typically with 5% povidone-iodine), the eye is stabilized with a pair of forceps, and the sample is taken with a small gauge (23–27 gauge) needle attached to a tuberculin syringe. The needle is kept over the iris to avoid trauma to the crystalline lens. It is not ideal to disturb the hypopyon, for fear of creating a tract. A 0.2 ml of fluid is ideal and is processed for microbiology (see the microbiology section of the book).
The mid-vitreous is the ideal location for vitreous humor collection, and when not possible, it is collected from the anterior vitreous. A 0.5 ml undiluted vitreous is ideal. This can be collected manually using a 2 ml syringe or using a vitreous cutter. The eye is anesthetized (usually a peribulbar block), the ocular surface is sterilized (typically, with 5% povidone-iodine), the instrument (needle mounted on a syringe or the vitreous cutter) is inserted in the pars plana region (3.5–4 mm from the limbus), and the required sample is withdrawn for microbiological study. When vitreous surgery is a part of the management, the vitreous fluid is collected using a vitreous cutter. In this case, the vitrector is placed in the mid-vitreous cavity, and a manual suction could be applied over the aspiration port of the vitrector. In either case, it is necessary that the needle/vitrector tip is visible to the surgeon (Fig. 2.3 right).
A safe vitreous aspiration method has been described using a butterfly needle [3]. In this case the 23 gauge butterfly needle is inserted in the pars plana region to the mid-vitreous cavity, and using a manual suction with a 10 ml syringe, vitreous fluid is collected in the silicone tubing of the butterfly needle system (Fig. 2.3). The collected vitreous sample is sent directly for microbiological processing. This could be safely used for aqueous humor collection.
Intravitreal Antibiotic Injection
Intravitreal antibiotics are given after withdrawal of intraocular fluid, preferably vitreous, or at least aqueous humor, and after vitrectomy, when this is done. The preparation of the antibiotic is described in another chapter (Chap. 22). They are taken in individual syringe and injected slowly in the mid-vitreous cavity with the beveled of the needle pointed to the pupillary area (Fig. 2.4). It is necessary to inject the correct dose of antibiotic, and hence a correct preparation is imperative. Some antibiotics are known to be retina toxic, especially the aminoglycosides, and hence one must not inject the incorrect dose, inject in the mid-vitreous cavity, and take precaution that the drug does not settle on the macula. Two antibiotics are injected, typically one against gram-positive bacteria and one against gram-negative bacteria. In case of fungal infection, only one antifungal antibiotic is injected. The volume of each antibiotic is 0.1 ml, and when required, they could be repeated 36–72 h after the first injection.
Macular infarction is not uncommon with wrong dosage or incorrect method of injection (Fig. 2.5). So as to reduce the dilution error for the commonly used antibiotics (vancomycin, ceftazidime, and voriconazole), the recently introduced E-Kit (Aurolab, Madurai, India; available in India currently) has made the dilution steps easier—add 10 ml of BSS to the antibacterial antibiotic and add 1 ml for the antifungal antibiotic to withdraw 0.1 ml for intravitreal injection [4] (Table 2.1). The current E-Kit contains only four standard intravitreal drugs—two antibacterial antibiotics (ceftazidime and vancomycin), one antifungal antibiotic (voriconazole), and one corticosteroid (dexamethasone) (Fig. 2.6).
Table 2.1
Traditional and E-Kit dilution steps of three common antibiotics
Antibiotic | Traditional | E-Kit | |
|---|---|---|---|
Vancomycin | Vial size | 500 mg | 100 mg |
Dilution steps | 1. Add 10 ml BSS 2. Withdraw 0.2 ml 3. Add 0.8 ml to make it to 1 ml 4. Keep 0.1 ml | 1. Add 10 ml BSS 2. Withdraw 0.1 ml | |
Final dose | 1 mg in 0.1 ml | ||
Ceftazidime | Vial size | 500 mg | 250 mg |
Dilution steps | 1. Add 2.2 ml BSS 2. Withdraw 0.1 ml 3. Add 0.9 ml to make it to 1 ml Keep 0.1 ml | 1. Add 10 ml BSS 2. Keep 0.1 ml | |
Final dose | 2.25 mg in 0.1 ml | ||
Voriconazole | Vial size | 200 mg | 1 mg |
Dilution steps | 1. Add 20 ml BSS 2. Withdraw 0.1 ml 3. Add 0.9 ml to make it to 1 ml 4. Keep 0.1 ml | 1. Add 1 ml BSS 2. Keep 0.1 ml | |
Final dose | 0.1 mg in 0.1 ml | ||
Fig. 2.6
E-Kit
Intravitreal Corticosteroid Injection
Dexamethasone is the commonest intravitreal corticosteroid used in endophthalmitis. The intravitreal dose is 0.4 mg in 0.1 ml; it is directly withdrawn from the vial that contains 4 mg dexamethasone phosphate. The details of dexamethasone and other corticosteroid injection are described in another chapter (Chap. 23). Intravitreal dexamethasone helps reduce the inflammation element in endophthalmitis without compromising the final visual acuity irrespective of the culture positivity [5] (Fig. 2.7).
Fig. 2.7
Inflammation is reduced faster in eyes that received intravitreal dexamethasone irrespective of culture positivity, and at end of 3 months, the regained vision was similar to eyes that did not receive intravitreal dexamethasone (Courtesy: Taraprasad Das, MD; reproduced with permission from Br J Ophthalmology 1999; 83: 1050–55)
Vitrectomy
Vitrectomy (Fig. 2.8) is the second key to management of endophthalmitis after intravitreal antibiotics. A three-port vitrectomy is an ideal method of vitrectomy. A longer infusion cannula, such as 6 mm cannula, or use of anterior chamber maintainer is the safer way to avoid suprachoroidal infusion. Vitreous is collected before the infusion begins, and the tip of infusion cannula must be visualized before the infusion is started. The EVS recommended removal of 50% of vitreous and not to induce posterior vitreous detachment for fear of causing retinal detachment. But with the greater safety of vitreous surgery technique and technology, such as smaller gauge vitrector, more distal position of the cutter port, faster cutting rates, and superior fluidics management have made a complete vitreous surgery in endophthalmitis a distinct possibility.
