small-gauge surgery
Endophthalmitis After Pars Plana Vitrectomy
Is small-gauge surgery associated with higher
risk
INGRID U.
SCOTT, MD, MPH, & HARRY W. FLYNN, JR, MD
At
the recent combined meeting of the American Society of Retina Specialists and the
European Vitreoretinal Society, authors of at least 5 presentations reported an
endophthalmitis rate of approximately 1% following 25-g (Figure 1) or 23-g pars
plana vitrectomy (PPV). This rate is much higher than endophthalmitis rates reported
for 20-g pars plana vitrectomy, which range from 0.03% to 0.15% (Table 1).1-7
In previous reports, the rates of endophthalmitis after PPV were lower than rates
after other intraocular surgical procedures.
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Figure
1. Transconjunctival sutureless 25-g pars planavitrectomy.
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For example, in a 7-year study (1995-2001) from the Bascom Palmer
Eye Institute in Miami, the incidence of acute-onset postoperative endophthalmitis
following PPV was 2 in 7429 (0.03%), which was a lower rate than the incidence rate
over the same 7-year time period for cataract surgery (0.04%), glaucoma surgery
(0.2%), penetrating keratoplasty (0.08%), and secondary intraocular lens placement
(0.2%).5 Sakamoto et al reported
that the incidence of acute endophthalmitis following triamcinolone acetonide-assisted
PPV was 1 in 1,886 (0.05%).7
Thus, while traditional 20-g PPV has been reported to be associated
with a lower rate of endophthalmitis compared with other intraocular surgeries including
cataract surgery, these most recently reported rates of endophthalmitis associated
with small-gauge PPV (approximately 1/100) are significantly higher than endophthalmitis
rates following cataract surgery (<1/1000). Why might this be the case?
PREDISPOSING ENDOPHTHALMITIS FACTORS
AFTER SMALL-GAUGE PPV
The unsutured sclerotomy wounds in small-gauge vitrectomy
may provide a conduit for bacterial entry. Early postoperative hypotony, which has
been reported as a frequent occurrence following small-gauge vitrectomy, may facilitate
this ingress, similar to the mechanism described by Taban et al in the context of
sutureless clear corneal cataract wounds.8
When using smaller-gauge vitrectomy, angled sclerotomy incisions may reduce the
incidence of postoperative leaking sclerotomies. In cases with an obvious leaking
sclerotomy at the end of surgery, suture closure can be considered. The vitreous
wick syndrome9
may represent a more significant risk in sutureless vitrectomies, in which wound
stabilization in the early postoperative period may, in some cases, be due to plugging
of the wound with vitreous.
|
Table
1. Incidence of Acute-onset Endophthalmitis Following 20-g Pars Plana Vitrectomy |
|
Authors
(year)* |
#/total |
Incidence |
Dates/comment |
|
Ho (1984)1 |
NA |
0.14% |
NA |
|
Bacon (1993)2 |
NA |
0.15% |
1986-1990 |
|
Aaberg (1998)3 |
3/6557 |
0.05% |
1984-1994 |
|
Zhang (2003)4 |
3/7000 |
0.04% |
1988-2000 |
|
Eifrig (2003)5 |
2/7429 |
0.03% |
1995-2001 |
|
Eifrig (2004)6 |
6/15,326 |
0.04% |
1984-2003** |
|
Sakamoto (2004)7 |
1/1,886 |
0.05% |
2002-2003/
triamcinolone-assisted
pars plana vitrectomy |
*Reference number
**Reference 6 includes data from references 3 and 5 |
These sclerotomy issues may be associated with higher rates of
bacterial entry into the vitreous cavity such that even the smallest bacterial innoculum
may be sufficient to initiate endophthalmitis in certain patients. Diabetic and
elderly patients with relative immune compromise may be at greater risk for endophthalmitis,
especially in this context of leaking sclerotomies and with the use of multiple
intraocular instruments in more complex cases. Although the use of subconjunctival
antibiotics has not been demonstrated to be significantly associated with a reduced
risk of endophthalmitis,10
the less frequent usage of subconjunctival antibiotics following sutureless vitrectomy
(due to the risk of intraocular migration of antibiotic) may contribute to this
higher rate of endophthalmitis. The increasing use of intravitreal adjuvants
such as triamcinolone acetonide may also predispose to a higher risk of endophthalmitis
(Table 2).
ORGANISMS CULTURED FROM ENDOPHTHALMITIS
AFTER PPV
While most studies reporting the incidence
rate of clinically diagnosed endophthalmitis postvitrectomy do not specify the causative
organisms, a 20-year study reported from Bascom Palmer Eye Institute identifies
the following organisms cultured from the 6 eyes with post-vitrectomy endophthalmitis:
Staphylococcus aureus (n=3), Proteus mirabilus (n=1), and S aureus
and Pseudomonas aeruginosa (n=1) (one case was culture-negative).6
The case of endophthalmitis following triamcinolone acetonide assisted PPV was caused
by Staphylococcus epidermidis.7
VISUAL ACUITY OUTCOMES ASSOCIATED WITH ENDOPHTHALMITIS
FOLLOWING PPV
The visual acuity outcomes associated with
endophthalmitis following PPV are generally poor. Among the3 cases of postvitrectomy
endophthalmitis reported by Zhang et al, visual outcomes were light perception in
2 patients and 0.02 (20/1000) in 1 patient.4
In a 10-year survey of postoperative endophthalmitis (1984-1994) reported from the
Bascom Palmer Eye Institute, visual acuity outcomes were worse in the patients who
developed endophthalmitis after pars plana vitrectomy than after cataract surgery,
glaucoma procedures, or secondary intraocular lens placement.3
Similarly, in a 7-year study of postoperative endophthalmitis (1995-2001) reported
from the Bascom Palmer Eye Institute, visual acuity outcomes after treatment for
postvitrectomy endophthalmitis (median = hand motions) were generally worse compared
to endophthalmitis after cataract surgery, glaucoma surgery, and secondary intraocular
lens categories.5
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Table 2. Potential Predisposing Factors for Endophthalmitis Following Small-gauge Pars Plana Vitrectomy
|
• Leaking sclerotomies causing
early postoperative hypotony
•
Vitreous wick in sclerotomies
•
Any bacterial innoculum into the vitreous cavity in patients with relative immune
compromise (eg, patients with diabetes mellitus and the elderly)
•
Non-use of subconjunctival antibiotics
•
Increasing use of intravitreal adjuvants such as triamcinolone acetonide |
In the 20-year overall study, visual acuity after treatment for
postvitrectomy endophthalmitis ranged from 20/200 to no light perception, with a
final vision of light perception or no light perception in 4 of 6 (67%) eyes.6
A case of endophthalmitis following triamcinolone acetonide assisted PPV and caused
by S epidermidis reported a preoperative visual acuity of 20/200 and a final
visual acuity of 20/100.11
In one reported case of endophthalmitis (culture-negative) following 25-g PPV, a
20/20 visual acuity outcome was achieved after treatment with intravitreal vancomycin
(Vancocin, ViroPharma) and amikacin (Amakin, Bedford Labs), oral ciprofloxacin (Cipro,
Bayer), and oral prednisolone.12
In another reported case of endophthalmitis (culture-negative) following 25-g PPV,
a 20/70 visual acuity outcome was achieved after treatment with intravitreal vancomycin
and ceftazidime (decreased final vision attributed to history of vitreomacular traction
syndrome and retinal damagesecondary to endophthalmitis, with foveal hypopigmentation
noted at the last follow-up examination).13
RECOMMENDATIONS TO REDUCE RATES OF ENDOPHTHALMITIS
FOLLOWING PPV
To try to reduce rates of endophthalmitis
following PPV, povidone-iodine is applied preoperatively directly to the eyelid
margins, eyelashes, and conjunctival ocular surface. A sterile drape is used to
cover the eyelashes and eyelid margins and to direct the eyelashes away from the
surgical field. Although many vitreoretinal surgeons do not use preoperative topical
antibiotics, a topical antibiotic postvitrectomy is commonly utilized, although
there are no definitive studies proving efficacy of postvitrectomy antibiotic administration.
TREATMENT OF ENDOPHTHALMITIS FOLLOWING
PPV
|
Table
3. Treatment Options for Endophthalmitis Following Pars Plana Vitrectomy |
• Intravitreal antibiotics in all cases
(optional intravitreal
dexamethasone)
•
Consider repeat pars plana vitrectomy (in most severe cases)
•
In cases with concurrent retinal detachment and gas-filled eye:
►
Consider antibiotics in the infusion fluid
►
Consider 50% gas fill and lower or standard dosages of intravitreal antibiotics
►
Consider use of systemic antibiotics |
Similar to treatment of other types of postoperative
endophthalmitis, management options for postvitrectomy endophthalmitis are summarized
in Table 3. In all clinically diagnosed cases, anterior chamber and vitreous cultures
are obtained first and then intravitreal injections of vancomycin (1 mg/0.1 cc),
ceftazidime (2.25 mg/0.1 cc), and optional dexamethasone (400 μg/0.1 cc) are
administered. In more severe cases, repeating PPV and administration of the aforementioned
intravitreal medications should be considered. The best treatment option for a gas-filled
eye with postvitrectomy endophthlamitis is not known;14
intravitreal antibiotics are generally recommended in such eyes but the dosage may
vary. To reduce the risk of retinal toxicity from intraocular antibiotics in a 50%
gas-filled eye, reduced dosages of the medications could be considered; alternatively,
standard antibiotic dosages may be used. Another option used by the authors is to
inject vancomycin (1 mg) alone into a gas-filled vitreous cavity and to administer
systemic antibiotics. An option for eyes with endophthalmitis in the setting of
concurrent retinal detachment is to add antibiotics to the vitrectomy infusion fluid
after intraocular cultures have been obtained and before the fluid-gas exchange
is performed.15
SUMMARY
While the reported incidence of endophthalmitis
following 20-g PPV is lower compared to other types of intraocular surgeries, recently
reported rates of endophthalmitis following small-gauge PPV are higher. Whether
these higher reported rates are associated with ocular hypotony, vitreous wick,
relative immune compromise, or non-use of subconjunctival antibiotics is not known.
REFERENCES
1. Ho PC, Tolentino FI. Bacterial endophthalmitis
after closed vitrectomy. Arch Ophthalmol. 1984;102:207-210.
2. Bacon AS, Davison CR, Patel BC, Frazer DG, Ficker LA, Dart
JK. Infective endophthalmitis following vitreoretinal surgery. Eye. 1993;7:529-534.
3. Aaberg TM Jr, Flynn HW Jr, Schiffman J, Newton J. Nosocomial
acute-onset postoperative endophthalmitis survey. A 10-year review of incidence
and outcomes. Ophthalmol. 1998;105:1004-1010.
4. Zhang S, Ding X, Hu J, Gao R. Clinical features of endophthalmitis
after vitreoretinal surgery. Eye Sci. 2003;19:39-43.
5. Eifrig CW, Flynn HW Jr, Scott IU, Newton J. Acute-onset postoperative
endophthalmitis: review of incidence and visual outcomes (1995-2001). Ophthalmic
Surg Lasers. 2002;33:373-378 (erratum in Ophthalmic Surg Lasers 2003;34:80).
6. Eifrig CW, Scott IU, Flynn HW Jr, et al. Endophthalmitis after
pars plana vitrectomy: incidence, causative organisms, and visual acuity outcomes.
Am J Ophthalmol. 2004;138:799-802.
7. Sakamoto T, Enaida H, Kubota T, et al. Incidence of acute
endophthalmitis after triamcinolone-assisted pars plana vitrectomy. Am J Ophthalmol.
2004;138:137-138.
8. Taban M, Sarayba MA, Ignacio TS, et al. Ingress of India ink
into the anterior chamber through sutureless clear corneal cataract wounds. Arch
Ophthalmol. 2005;123:643-648.
9. Venkatesh P, Verma L, Tewari H. Posterior vitreous wick syndrome:
a potential cause of endophthalmitis following vitreo-retinal surgery. Med Hypotheses.
2002;58:513-515.
10. Ciulla TA, Starr MB, Masket S. Bacterial endophthalmitis prophylaxis
for cataract surgery: an evidence-based update. Ophthalmol. 2002;109:13-24.
11. Yamashita T, Doi N, Sakamoto T. Weak symptoms of bacterial
endophthalmitis after a triamcinolone acetonide-assisted pars plana vitrectomy.
Graefes Arch Clin Exp Ophthalmol. 2004;242:679-681.
12. Taylor SR, Aylward GW. Endophthalmitis following 25-gauge
vitrectomy. Eye. 2005;19:1228-1229.
13. Taban M, Ufret-Vincenty RL, Sears JE. Endophthalmitis after
25-gauge transconjunctival sutureless vitrectomy. Retina. 2006;26:830-831.
14. Foster RE, Rubsamen PE, Joondeph BC, et al. Concurrent endophthalmitis
and retinal detachment. Ophthalmol. 1994;101:490-498.
15. Morgan BS, Larson B, Peyman GA, West CS. Toxicity of antibiotic
combinations for vitrectomy infusion fluid. Ophthalmic Surg. 1979;10:74-77.
Ingrid U. Scott, MD, MPH, is professor of ophthalmology
and health evaluation sciences at the Milton S. Hershey Medical Center College of
Medicine at Pennsylvania State University. Harry W. Flynn, Jr, MD, is professor
and J. Donald M. Gass Distinguished Chair of Ophthalmology at the Bascom Palmer
Eye Institute at the Leonard M. Miller School of Medicine at the University of Miami.
The authors have no financial interest in information presented in this article.
Retinal Physician, Issue: November 2006