Acute post-op endophthalmitis 1 week after uncomplicated extracapsular cataract surgery with severe corneal edema and melting at the limbus (Source: Rezende and Kickinger. Infectious Endophthalmitis. Essentials of Opthalmology, Vitreo-retinal surgery progress 3)
Acute post-op endophthalmitis 36 h after uncomplicated temporal clear corneal phacoemulsification without corneal involvement (Source: Rezende and Kickinger. Infectious Endophthalmitis. Essentials of Opthalmology, Vitreo-retinal surgery progress 3)
The only strongly supported method of preoperative (pre-op) prophylaxis, besides field sterilization, is pre-op povidone-iodine 5–10 % drops [15, 16]. Other techniques such as antibiotics intra-op, subconjunctival, in irrigation solutions, and intracameral are still controversial and lack randomized research support, but there is no evidence of these precautions causing any harm .
The most commonly implicated organisms in acute post-op cases are coagulase-negative gram-positive Staphylococcus, mostly Staphylococcus epidermidis (S. epidermidis). Other organisms include other gram-positive bacteria such as Staphylococcus aureus (S. aureus), Streptococcal sp., Enterococcus, and Propionibacterium acnes (P. acnes). Gram-negative organisms include Pseudomonas aeruginosa (P. aeruginosa), Proteus, Haemophilus, Enterobacter, and others, but these are much less commonly involved [17, 18]. The VA outcome depends largely, among other factors, on the causative agent, with better outcomes reported in culture-negative cases or cases growing coagulase-negative gram-positive species without corneal infiltrates . Factors associated with poor VA outcome include VA at presentation, corneal infiltrates/melting, other gram-positive or gram-negative species, dense vitreous debris or membranes, lid swelling, and retinal and/or choroidal detachment [18, 19].
Despite the advances in cataract surgery and the various precautions to prevent post-op infections, the rate of endophthalmitis has significantly risen during this decade compared to the previous one [11, 20, 21] with a reported incidence ranging between 0.076 % and 0.3 % [20, 22, 23].
Main EVS Recommendations
This study included 420 patients diagnosed with acute endophthalmitis after cataract surgery with IOL implantation or secondary IOL implantation.
All patients presenting with acute post-op endophthalmitis should receive intravitreal vancomycin 1 mg/0.1 ml and amikacin 0.4 kg/0.1 ml regardless of their presenting VA.
The use of systemic antibiotics had no beneficial effect on the final VA. Medications evaluated were intravenous ceftazidime and amikacin, with oral ciprofloxacin replacing ceftazidime in case of penicillin allergies.
Anterior chamber (AC): aqueous humor samples were positive in 26.9 % of cases. In 4.2 % of cases, aqueous was positive and undiluted vitreous sample was negative.
Vitreous: non-diluted samples had 58.9 % positive cultures. Another 8.9 % had positive cultures from the vitrectomy cassette fluid alone.
Vitreous tap/biopsy: yielded 67.4 % of positive cultures.
Vitrectomy: yielded 73.5 % of positive cultures. There was no statistical significance between vitrectomy and vitreous tap/biopsy culture yield.
Microorganisms: among the 291 eyes with positive cultures, 68 % showed coagulase-negative gram-positive organisms (S. epidermidis); 22 % showed other gram-positive organisms, like S. aureus and Streptococcus; and only 6 % showed gram-negative organisms.
Outcomes at 9–12 months: 53 % achieved 20/40 or better, 74 % achieved 20/100 or better, and 15 % had severe vision loss of worse than 5/200.
Only 5 % of patients had final VA of no light perception (NLP).
Based on presenting VA, patients with light perception (LP) or NLP had a threefold higher chance to achieve 20/40 or better (33 vs. 11 %) and a 50 % lower chance to suffer from severe visual loss if treated with immediate vitrectomy and intravitreal antibiotics versus vitreous tap and inject.
There was no statistical significance between the two treatment groups in patients presenting with VA of hand motions (HM) or better when treated with either protocol.
Better VA outcomes were achieved in cases that had no growth or grew coagulase-negative Staphylococcus sp. compared to other organisms.
Risk factors for reduced final VA included symptoms within 2 days of surgery, LP on presentation, relative afferent pupillary defect, non-intact posterior capsule, IOP less than five or more than 25 mmHg, rubeosis iridis, corneal infiltrate, melting and/or ring ulcer, and an absent red reflex.
At the final visit, the media was clearer in the vitrectomy group versus the tap group regardless of presenting VA (90 vs. 83 %).
Most common causes of poor final VA were macular complications including epiretinal membrane, edema, pigmentary changes, and ischemia.
One-third of patients had to undergo a second procedure (vitrectomy or tap) within 36–60 h in eyes that did poorly.
The value of intravitreal corticosteroids was not assessed.
All patients received prednisone 30 mg PO bid for 5–10 days and received subconjunctival injection of dexamethasone 6 mg/0.25 ml.
All patients received subconjunctival vancomycin, 25 mg/0.5 ml, and ceftazidime, 100 mg/0.5 ml.
Summary for the Surgeon
Patients presenting with LP VA should undergo immediate pars plana vitrectomy and intravitreal antibiotics (vancomycin and ceftazidime).
If patients present with VA of hand motions or better post-op phaco and secondary IOL implantation, there is no difference between vitreous tap and vitrectomy with injection of antibiotics.
Remaining media opacities were significantly less in the vitrectomy group, but this was not found to be a reason for a low final VA.
Intravenous ceftazidime and amikacin are not recommended as adjunctive systemic therapy as they did not show any benefit.
There is a higher chance of having a positive culture with a vitreous than with an anterior chamber sample, but overall positive results were 67.3–73.5 %.
More favorable outcomes are associated with culture-negative or cases caused by coagulase-negative S. epidermidis, which are the most commonly encountered microorganism.
10.2.2 Chronic Postoperative Endophthalmitis
Chronic post-op endophthalmitis is diagnosed in cases that present beyond 6 weeks of the inciting event. The clinical picture is usually more subtle and is often misdiagnosed and treated as a sterile anterior uveitis. The signs are usually more subtle, including anterior chamber reaction responsive to corticosteroids but recurrent after cessation of treatment, granulomatous keratic precipitates, IOL precipitates, endocapsular hypopyon (Fig. 10.3), vitritis, or simply as an isolated disk edema [1, 22, 28]. The most common microorganisms involved are coagulase-negative S. epidermidis, Propionibacterium acnes (P. acnes), fungi (e.g., Candida parapsilosis), anaerobic Streptococcus species, Nocardia asteroides, Actinomyces sp., and Corynebacterium sp. . Visual outcomes are generally better than acute cases because these are lower-virulence microorganisms [1, 3, 22, 29]. In P. acnes chronic endophthalmitis, the endocapsular hypopyon represents colonies of the microorganism and inflammatory cells situated between the posterior surface of the IOL and the posterior capsule (Fig. 10.3). This peculiar location is thought to protect the bacteria from antibiotics and host defense mechanisms and could explain the high recurrence rate in cases where the lens and capsule are left in place . In large series evaluating the best treatment option, the following are the recurrence rates of different techniques [22, 29, 30]:
Chronic post-op endophthalmitis with endocapsular hypopyon (arrow) (Source: Rezende and Kickinger. Infectious Endophthalmitis. Essentials of Opthalmology, Vitreo-retinal surgery progress 3)
Injection of intravitreal antibiotic: 93 %
Pars plana vitrectomy (PPV) with intravitreal antibiotic: 50 %
Pars plana vitrectomy with partial capsulectomy, intravitreal antibiotic, and retention of IOL: 26 %
Pars plana vitrectomy with total capsulectomy, IOL removal or exchange, and intravitreal antibiotic: 0 %
The antibiotic of choice is intravitreal vancomycin 1 mg/0.1 ml. The average time for growth in cultures was between 8 and 10 days .
10.2.3 Bleb-Associated Endophthalmitis
The result of trabeculectomy surgery for glaucoma is a filtering bleb over the trabeculectomy site providing an alternative drainage route of aqueous humor, thus reducing IOP. This bleb should be water tight to function properly and prevent bacterial access to the intraocular environment (Fig. 10.4). The conjunctiva carries normal flora capable of causing post-op endophthalmitis including S. epidermidis, S. aureus, group C Streptococcus, Bacillus sp., Haemophilus influenzae (H. influenzae), and P. aeruginosa . It has been documented that leaky filtering blebs allow access of the tear film into the AC  along with the ocular surface bacteria.
Normal filtering bleb. Note the good height of the functional bleb and the normal vascularity surrounding the central avascular bleb (Courtesy of Dr. Mark Lesk, Maisonneuve-Rosement Hospital, University of Montreal, Montreal, Canada)
Blebitis is diagnosed when the filtering bleb becomes infected without an associated vitritis; the risk of progressing into an endophthalmitis is high if not treated urgently and properly. Bleb-associated endophthalmitis (BAE) is diagnosed when blebitis is associated with vitritis and intraocular inflammation . In such cases, the most common symptoms are pain and redness. Other symptoms include blurred vision, tearing, purulent discharge, lid edema, and photophobia [1, 33] (Fig. 10.5). Risk factors include the use of 5-fluorouracil or mitomycin-C, bleb leaks, conjunctivitis, bleb manipulation, inferior location of bleb, trauma, and contact lens use [33–37]. The incidence of BAE ranges from 0.2 % to 9.4 % which is higher than other intraocular surgeries and is believed to be largely due to the use of antifibrotic agents [33–35]. Bleb-associated endophthalmitis is divided into early, if presented within 6 weeks post-op, or late (may happen even many years after surgery). In the early period, the most common microorganisms are S. epidermidis and S. aureus, while in late cases Streptococcus sp. and H. influenzae are more frequently cultured [34, 36, 37]. Cultures were found to be positive in 67–97 % of cases . Visual acuity outcome is generally poor with final VA better than 20/400 ranging between 31 % and 65 %. Outcomes post-Staphylococcal endophthalmitis seem to be more favorable than post-Streptococcalcendophthalmitis [34, 36]. The EVS did not include patients undergoing filtering glaucoma surgery, and extrapolation of its data should be done carefully. Although no randomized controlled clinical trial has been conducted to date, the surgical outcomes for BAE seem to be better with prompt pars plana vitrectomy and intravitreal antibiotics than with vitreous tap and intravitreal antibiotics regardless of time of onset and pre-op VA . Besides intravitreal antibiotics, topical fortified drops (vancomycin 50 mg/ml and gentamicin 15 mg/ml) and oral fourth-generation fluoroquinolones are used to treat the infected bleb [35, 37, 38]. If a leaky bleb is present in association with blebitis and endophthalmitis, it is recommended to perform a bleb excision and conjunctival advancement in addition to pars plana vitrectomy with topical and intravitreal antibiotics [36, 39].
Bleb-associated endophthalmitis 3 years after trabeculectomy with mitomycin. Culture was positive for Streptococcus sp. (Source: Rezende and Kickinger. Infectious Endophthalmitis. Essentials of Opthalmology, Vitreo-retinal surgery progress 3)
10.2.4 Post-intravitreal Injection Endophthalmitis
The number of intravitreal injections performed has increased significantly over the last decade, and, accordingly, the rate of post-intravitreal injection endophthalmitis (IVIE) has also increased. In a recent review by Moshfeghi et al., the rate of IVIE was 0.02–0.14 % . The most common organisms are S. epidermidis, S. aureus, Streptococcus sp., and, usually in case of drug contamination, fungal species. The rate of postinjection Streptococcal endophthalmitis is three times higher than that in post-op cases . This could be explained by the fact that surgical masks were not routinely worn during the office-based procedure. In an experiment simulating the setting of intravitreal injections, oral flora was found to grow on culture plates significantly higher when the surgeon and the patient were not wearing surgical masks than in cases when they wore them, avoided talking, or turned their faces away while talking; the rate of Streptococcal sp.-positive cultures was found to be 67–83 % [42, 43]. In another study, they compared bacterial growth on culture plates while wearing surgical masks, in silence, and with pretreatment of the plates with 5 % povidone-iodine without surgical masks or silence. The least growth was found on the povidone-iodine pretreated plates . In comparing office-based setting versus operating room-based setting, there does not seem to be a significant difference in the rate of endophthalmitis or the causative microorganisms when surgical masks are used during office-based intravitreal injections . Another important cause of IVIE is the contamination of the medications prepared at compounding pharmacies. Several outbreaks have been reported with mainly Streptococcal or fungal species resulting in very poor outcomes [45–47]. If contamination is suspected, testing of unused syringes containing the medication from the same lot is warranted, and it should be reported to the local authorities.
We conducted a retrospective chart review of acute endophthalmitis (AE) post-intravitreal bevacizumab injection in cases done by one surgeon. The surgeon, nurses, and patients wore surgical masks during the procedures done in the minor procedure room at the Department of Ophthalmology ambulatory clinic, Maisonneuve-Rosemont Hospital, University of Montreal, Quebec, Canada. The rate of IVIE was found to be 0.13 % (4 of 3,088 injections); two were culture-positive for coagulase-negative S. epidermidis, and two had no growth (Table 10.1). All patients underwent tap and injection of vancomycin 1 mg/0.1 ml and ceftazidime 2.25 mg/0.1 ml upon diagnosis of IVIE. Three of them underwent a later 25-gauge (25g) MIVS to clear vitreous opacities. The fourth patient developed a central retinal artery occlusion during the period of recovery from IVIE and refused to undergo further procedures. All four patients improved after tap and injection of antibiotics, two out of four (culture-negative) patients improved better than their VA before endophthalmitis had developed, and three out of four continued to receive intravitreal bevacizumab (IVB) without any further infectious complications .
Visual acuities and culture results of the four patients that had post-IVB endophthalmitis
VA at AE
The outcomes of IVIE also depend on the causative organism, where coagulase-negative S. epidermidis cases or culture-negative cases have a better final VA outcome than post-Streptococcal cases. The final VA post-IVIE when surgical mask is used was found to be as favorable as post-phaco and IOL implantation acute endophthalmitis with a good percentage of patients returning to baseline VA . Treatment may be guided by the EVS study, but surgeons should carefully extrapolate these results and decide on each patient’s treatment individually. In this particular entity, we prefer to start the treatment with tap/inject to try to preserve the vitreous as the pharmacokinetics of intravitreal injections may be significantly altered in vitrectomized eyes (Fig. 10.6) .
On the left, 4 days post-ranibizumab intravitreal injection-related infectious endophthalmitis. On the right, good response after 2 weeks post-tap/inject with vancomycin 1 mg/0.1 ml and ceftazidime 2.25 mg/0.1 ml. Culture grew Staphylococcus epidermidis. Patient continued to receive regular anti-VEGF injections without any subsequent infection
10.2.5 Post-vitrectomy Endophthalmitis
This clinical entity is rare and carries poor prognosis for the affected eye. More detailed discussion will follow in the MIVS section.
10.2.6 Post-Type-1 Boston Keratoprosthesis Endophthalmitis
Type-1 Boston permanent keratoprosthesis is a polymethylmethacrylate device in a collar button shape that is used to restore the clarity of the visual axis in cicatricial corneal diseases that are not amenable to conventional corneal transplant  (Fig. 10.7). This procedure allows a connection between the sterile anterior chamber environment and the ocular surface with its flora and external pathogens . In a review of literature from 2001 to 2011 by Robert et al., the prevalence of post-permanent KPro endophthalmitis (KPE) was found to range from 0.0 % to 12.5 %. Risk factors include Steven-Johnson syndrome, ocular cicatricial pemphigoid, noncompliance with antibiotics, nonuse of vancomycin, poor contact lens hygiene, corneal melting, and infectious keratitis. The most common causative agents are gram-positive bacteria (60 %)  with one study reporting that 10 out of 15 gram-positive cultures grew Streptococcus viridans . Other organisms include Staphylococcal sp., gram-negative bacteria, and fungi (Fig. 10.8). The most important prevention method is using vancomycin drops in addition to the traditional quinolones; this has significantly reduced the prevalence of KPE [52, 53]. This entity tends to present in the late post-op period, and the outcomes depend on the causative microorganism but are usually poor due to the higher prevalence of Streptococcus sp. A high index of suspicion is important in cases of retroprosthesis membrane and vitritis with or without pain, and B-scan ultrasound is an important diagnostic tool in cases of poor visualization [54, 55].
Type-1 Boston keratoprosthesis
Candida albicans endophthalmitis post-type-1 Boston keratoprosthesis. Note inflammatory debris accumulated at the posterior surface of the prosthesis
10.2.6.1 Summary for the Surgeon
In chronic endophthalmitis, PPV with total capsulectomy and intraocular lens removal plus intravitreal vancomycin injection is the procedure associated with the lowest recurrence rate.
Bleb-associated endophthalmitis is characterized by pain and decreased vision with mucopurulent infiltrate within the bleb, hypopyon, and vitritis.
Risk factors for BAE include the use of antifibrotic agents, blebitis, inferiorly located blebs, conjunctivitis, bleb manipulation, leaky blebs, and contact lens use.
In post-intravitreal injection endophthalmitis, there is a threefold higher risk of Streptococcus sp. when compared to post-op endophthalmitis, and this is most likely due to contamination by oral flora if surgical mask is not used. Precautions, such as avoiding speaking or using surgical masks, should be taken to minimize injection-field contamination. Compounding pharmacy contamination is another cause of virulent microorganisms with poor-outcome IVIE.
Most patients should be encouraged to resume intravitreal injections, if still indicated, after the resolution of endophthalmitis.
No significant differences were found between the rate and causative microorganism of IVIE when office-based setting versus operating room-based setting was compared when surgical masks were used.
Endophthalmitis post-KPro is mostly due to gram-positive bacteria, mainly Streptococcus sp. and Staphylococcal sp., with generally poor outcomes.
Post-KPro surgery prophylaxis with vancomycin drops in addition to quinolones has significantly reduced the prevalence of PKE.
As the EVS included only acute post-op cases after cataract surgery or secondary IOL, extrapolation of its data should be done carefully for other entities. The surgical outcome for BAE seems to be better with prompt pars plana vitrectomy and intravitreal antibiotics, while there is no consensus on the best treatment for IVIE or PKE.
10.2.7 Ultrasound in Endophthalmitis
The diagnosis of endophthalmitis is mainly done on clinical examination, but valuable information can be obtained from A- and B-scan ultrasonography of the affected eye at presentation. Echographic findings include vitreous opacities; vitreous membranes (Fig. 10.9); vitreous incarceration; location of persistent vitreous attachments; vitreoretinal traction; retinal detachment (RD) (Fig. 10.10) and its extent; subretinal opacities; presence of choroidal detachment (CD) and its size, location, and type (serous vs. hemorrhagic); retinochoroidal thickening; choroidal calcification; optic nerve swelling; scleral thickening; lens status; IOL location; retained nuclear fragments; globe size; and orbital inflammation [19, 56, 57]. The gain should be increased between 84 and 90 dB, as inflammatory cells and membranes have low reflectivity . Several study groups found significant negative correlation between these signs and the final VA [19, 57, 59].
Severe vitreous opacities and membranes in a case of acute endophthalmitis post-intravitreal injection of bevacizumab
Tractional retinal detachment in a case of endophthalmitis post-type-1 Boston keratoprosthesis
A study by Dacey et al. reviewed records of 137 endophthalmitis patients. They found that 69 % (24/35) of eyes with vitreous opacities of severe density had a final VA worse than 1/200 versus 33 % (10/30) of eyes with mild opacities. Also, 91 % (30/33) of eyes with final VA of NLP had moderate to severe opacities density on the initial echography. When they compared the final VA of eyes that had vitreous membranes on the initial echography (20/137) to those that had none, 55 % (11/20) versus 25 % (29/116) had final VA of NLP, respectively. In eyes that had RD on initial echography (25/137), none had final VA better than 20/200. Fifty-six percent of eyes with RD had final VA of NLP versus 21 % of eyes without RD. Of note, the status of the macula (macula-on vs. macula-off) had no statistical significance on final VA. The coexistence of choroidal detachment on presentation had a significant impact on final VA. Eighty-one percent (22/27) of eyes with CD on the initial ultrasound had final VA worse than 1/200 versus 47 % (50/106) of eyes that had no CD. Choroidal detachment was the strongest indicator of final VA worse than 20/100. They also found a correlation between B-scan findings and the infecting microorganism. Streptococcal endophthalmitis cases were at least twice more likely to develop severe vitreous opacities or vitreous membranes on the initial presentation than other infecting microorganisms (56 % and 45 %, respectively). Gram-negative endophthalmitis was significantly correlated with the presence of choroidal detachment but with less significant vitreous opacities . Another valuable use of pre-op ultrasound is to confirm the location of retinal and/or choroidal detachment in relation to the area of intended sclerotomy placement, for either a vitreous sample or surgery, thus avoiding more potential serious complications .
10.3 Current Surgical Techniques
10.3.1 Office-Based Vitreous Tap/Biopsy
Explain to the patient the steps of the procedure, risks, and benefits and obtain a consent form.
Apply topical proparacaine 0.5 % drops followed by povidone-iodine 5 % solution.
The authors prefer using retrobulbar/peribulbar anesthesia (as described below). As the eye is usually markedly inflamed, this type of anesthesia helps the patient to be more comfortable during the procedure and will relieve his/her pain for approximately 2 h.
Under sterile technique, withdraw 0.1 ml of vancomycin (1 mg) and 0.1 ml of ceftazidime (2.25 mg) and place them on a sterile drape.
Place a sterile lid speculum and apply another drop of 5 % povidone-iodine at the site of entry.
A transconjunctival vitreous tap is done using a 25-g or 26-g needle on a 1-ml syringe. We recommend entering in an oblique fashion to avoid wound leakage; stabilizing the eye with a sterile cotton-tipped applicator will facilitate this maneuver.
In case of pseudophakia, aspirate in the anterior vitreous right behind the lens where the anterior liquefied vitreous is usually located. This will minimize the chance of causing vitreous traction and vitreous strand incarceration at the entry wound. In case of phakic patients, this is not recommended due to the risk of traumatic cataract formation.
Withdraw 0.2–0.5 ml of liquefied vitreous while gauging the IOP with the cotton-tipped applicator then remove the needle and roll the conjunctiva over the wound site.
The vitreous sample should be capped, labeled with the patient’s information, and placed on the sterile drape.
Using a 30-g needle, the antibiotics should be injected consecutively at the same distance from the limbus. The first entry site should be avoided, and if the eye is too soft, we recommend counter traction with toothed forceps.
The obtained sample should be inoculated directly onto culture media including blood, chocolate, and Sabouraud agars and meat broth media. An inoculum should also be placed onto a glass slide for gram staining and microscopy.
In case of an available microbiology lab, the sample should be taken there directly and labeled as urgent. Communication with the microbiology team could not be overemphasized.
Alternatively, portable vitrectomy systems used in an ambulatory setting may be used for safer vitreous biopsy, minimizing vitreous traction. Currently there are two systems available. One is a 25-g sutureless Retrector® system (Insight Instruments, Stuart, FL). This is a portable, battery-powered system with a maximum cut rate of 600–1,250 cpm that features a single-use retractable sheathed guillotine 25-g cutter with a built-in 23-g needle. The needle is introduced bevel down through displaced conjunctiva in an oblique one-plane tunnel into the vitreous cavity 3–4 mm from the limbus. This one-port technique can be done using the light source from the surgical microscope or using the indirect ophthalmoscope for visualization (Figs. 10.11 and 10.12). A newer system using a larger vitrectomy unit is also now available for office-based vitreous biopsy (VersaVIT®, Synergetics Inc, O’Fallon, MO). An additional interesting feature of this equipment includes the usage of 27-g valved cannulas. This allows surgeons, through the same one-port sclerotomy, to perform the vitreous biopsy and inject antibiotics. In an office-based environment, the presence of valves and the smaller diameter of the cannulas may increase safety and decrease contamination from external sources.
One-port 23-g Intrector® system (Insight Instruments, Stuart, FL) using the indirect ophthalmoscopy for vitreous biopsy
Portable vitrectomy machine with small-gauge valved cannulas/trocars (bottom left) and small-gauge vitrectomy kit (VersaVIT®, Synergetics Inc, O’Fallon, MO)
The undiluted sample is cut and aspirated using a sterile 1.0-ml syringe connected to the aspiration line of the portable vitrector. A minimum of 0.3–0.5 ml of undiluted vitreous fluid is cut and removed from the mid-vitreous through controlled manual aspiration. No infusion line is necessary for this biopsy procedure.
Although some surgeons advocate general anesthesia for longer pars plana vitrectomy cases because of the difficulty in achieving adequate anesthesia in an inflamed, painful eye, we advocate performing this surgery under retro-/peribulbar anesthesia. Injection of 5 ml of 2 % lidocaine without epinephrine mixed with 5 ml of bupivacaine 0.5 % in a 10-ml syringe and 1.5-in 25-g hypodermic needle is used in combination with light sedation of the patients. This usually achieves the desired anesthesia keeping them comfortable throughout the procedure. Care should be taken not to have subconjunctival anesthetic infiltration, as this could render placement of the cannulas more difficult and increases the risk of cannula extrusion during surgery.
10.3.2.1 Key Concepts for MIVS in Endophthalmitis
Always begin by securing the original surgical wound with sutures even if it appears stable (Fig. 10.13).
Clear corneal wound closure with 10-0 nylon (Source: Rezende and Kickinger. Infectious Endophthalmitis. Essentials of Opthalmology, Vitreo-retinal surgery progress 3)
In case of reduced visibility of the posterior segment, it is safer to place the infusion line in the AC until the visual axis is cleared.
In case of post-trabeculectomy endophthalmitis with conjunctival dehiscence, start with delicate closure of the conjunctiva paying extra attention not to manipulate the tissues excessively to avoid tearing the friable conjunctiva. In case of pus collection within the bleb, it should be excised, and if necessary, the sclera sutured close with a scleral patch graft.
Eyes with endophthalmitis can be hypo- or hypertensive. Wound structuring and transconjunctival suturing are more challenging in cases of low IOP and inflamed conjunctiva.
Caution should be exercised to avoid excessive infiltration of the conjunctiva and Tenon’s capsule during retrobulbar anesthesia as this will render surgical wound construction and placement of the cannulas at the proper distance from the limbus quite difficult. In addition, this increases the risk of extrusion of cannulas during the procedure.
Avoid using the original wound for working in the anterior segment as this increases risk of endophthalmitis .
Retinal detachment in an infected eye is a very serious complication with limited visual recovery.
10.3.3 MIVS for Infectious Endophthalmitis
Over the last decade, the technology used in vitrectomy surgery has evolved, and the safety of MIVS has strong support in the literature [60, 61]. This section will address MIVS for infectious endophthalmitis after various surgical procedures, its outcomes, as well as endoscopy-guided MIVS. The authors use the Constellation ULTRAVIT 25+ system (Alcon Labs, Fort Worth, TX, USA).
10.3.3.1 Surgical Preparation
10.3.3.2 Acute Infectious Endophthalmitis
For eyes that had undergone phaco and IOL implantation or secondary IOL implantation, the first step is to secure the surgical wound by placing 10-0 nylon sutures (Fig. 10.13) for either corneal or limbal incisions.
Start by collecting a non-dilute vitreous sample.
Keep the infusion line primed and within the operating field to avoid complications secondary to ocular hypotension while obtaining the non-dilute sample.
Using the 25-g valved cannula system, first create a scleral tunnel in the inferotemporal quadrant at 3.0–3.5 mm from the limbus and place the infusion line closed.
Place the second sclerotomy in the superotemporal quadrant and insert the vitrector with a 3-ml syringe connected to its aspiration line and start collecting the specimen at a cut rate of 5,000 cpm and aspiration of 650 mmHg from the mid-vitreous cavity. The assistant starts withdrawing the non-diluted sample judiciously to obtain 0.2–0.5 ml. Monitor IOP using a cotton-tipped applicator.
Next step is to clean the anterior chamber.
Clamp the infusion line to disconnect it and place a plug on its cannula (in case there is no valved system).
With the infusion line placed anteriorly and set at 35 mmHg, create a second corneolimbal paracentesis to introduce your instruments.
Start by clearing the hypopyon/debris using the vitrector at a maximum cut rate and aspiration. At this point, the infusion may be raised to 60 mmHg.
In case of posterior synechiae, place a bent 26-g needle on a viscoelastic syringe to dissect away the iris from the IOL/anterior capsule/fibrin. Use the needle tip to cut the synechiae while injecting the viscoelastic to lift up the iris.
Usually, a cyclitic membrane forms across the pupil and over the crystalline lens/IOL/iris affecting visualization of the posterior segment. This layer is sometimes hard to recognize, but if the IOL seems blurry, there is a good chance that it is covered with fibrin.
Using a 25-g end-grasping membrane forceps, the authors prefer using Alcon 25-g MAXGRIP forceps (Alcon Labs, Fort Worth, TX, USA), peel that layer off the IOL and iris. A bimanual approach is sometimes necessary to dissect these membranes using the forceps and the vitrector.
When working with the vitrector over the iris, it is safer to turn the port 90–180° away to avoid inadvertent trauma.
In case of significant AC bleeding, viscoelastic can be used as a tamponade to control bleeding and be able to complete the posterior segment surgery. Always keep in mind to remove the viscoelastic from the AC at the conclusion of surgery to decrease immediate post-op pressure spikes.
When the AC work is done, return the infusion to the inferotemporal pars plana cannula and close all paracentheses with 10-0 nylon sutures. Before opening the infusion, confirm that it is still placed within the vitreous cavity. If visualization is still poor, the light pipe can be passed through the cannula to confirm its position.
Place the third 25-g valved cannula on the superonasal quadrant at 3.0–3.5 mm from the limbus for the light pipe. In case of poor visualization due to severe corneal edema, and in the lack of an endoscopy unit, only two ports are sufficient to carry out a “blind” core vitrectomy.
Newer and stronger light sources are preferred due to media opacities. A noncontact wide-angle viewing system is recommended to avoid corneal abrasion in an infected eye (some surgeons remove the corneal epithelium to improve visualization and penetration of topical medications, but we strongly discourage it).
Carry on core vitrectomy to remove as much inflammatory debris as possible, but the extent of peripheral vitrectomy is governed by the clarity of the media. Attempts to detach the posterior vitreous and peripheral vitreous shaving are risky and can induce tears due to the friable and inflamed retina. These steps are rarely attempted in such conditions without endoscopy use.
Inspect the retina looking for tears or areas of necrosis. If present, they should be treated with laser photocoagulation (to encircle the lesions).
At the conclusion of vitrectomy, perform a partial air-fluid exchange (one-third air) for internal wound tamponade.
To avoid the syringe-plunger effect while removing the cannulas, use the angulated McPherson forceps to slide the cannula over the light pipe, withdraw the light pipe in the same orientation of the scleral tunnel, and roll the conjunctiva over the wound using a cotton-tipped applicator. This reduces vitreous prolapse from the wound, thus reducing the risk of post-op hypotony and reinfection [62, 63].
The antibiotics (vancomycin 1 mg/0.1 ml and ceftazidime 2.25 mg/0.1 ml) can be injected through a valved cannula.
Remove the infusion line along with the cannula at once, using the angulated forceps.
Careful wound examination for leakage should be done prior to conclude the case. We recommend cauterizing each transconjunctival wound to seal them and avoid further contamination. One should have a low threshold to suture a suspicious wound using 6-0 or 7-0 Vicryl.
Take care when removing the lid speculum. It may compress the eye and be responsible for immediate post-op hypotony.
The non-dilute vitreous along with the vitrectomy cassette should be labeled and sent for microbiological examination. Report to microbiology any prior antibiotics usage.
Prescribe moxifloxacin or gatifloxacin drops every 2 h, prednisolone acetate 1 % q1 h, atropine 1 % BID, and oral prednisone 4–60 mg QD along with a proton pump inhibitor to protect the patient’s stomach.
In case of contraindication to systemic prednisone, sub-Tenon injection of 1-ml triamcinolone acetate 40 mg/ml could be used, but periocular or intraocular steroids are not used routinely.
All patients should be followed up closely to evaluate the evolution of their disease. Usually, if the microorganism is sensitive to the injected antibiotics, the patient should feel significantly less pain the next day.
In cases where severe corneal edema or even corneal melting is present, a two-port 25-g core vitrectomy or even only the office-based vitreous biopsy will suffice to obtain a sample for microbiological analysis and intravitreal antibiotics injection. Care should be taken to stay within the center of the vitreous cavity and avoid unnecessary movements to avoid inadvertent retinal breaks. Another valuable option that we prefer is to perform endoscopic-guided MIVS that will be described in details in the next section.