Visual prognosis in eyes with post-keratoplasty graft infection is poor even after a successful medical therapy due to corneal scarring after resolution of keratitis and a high rate of graft decompensation. A repeat kerato-plasty is required in almost half of the cases.4,10 Clear grafts following graft infection has been reported in 23 to 67 percent cases in various studies.5,6,15,20 A best corrected visual acuity (BCVA) of better than 6/60 on Snellen’s acuity chart is seen in only 14 to 30 percent of the eyes and only 6 percent of patients achieved a best corrected visual acuity of > 6/18 at the final follow up in one study.10 Infections after lamellar keratoplasty are associated with grave prognosis and may not be amenable to antimicrobial therapy.8 This may necessitate the removal of the graft or a therapeutic penetrating keratoplasty.8
MICROBIAL KERATITIS AFTER REFRACTIVE SURGERY
Microbial keratitis has been reported after radial keratotomy, photorefractive keratectomy, laser in situ keratomileusis and laser subepithelial keratectomy.
Microbial Keratitis After LASIK
Microbial keratitis following LASIK is a rare compli-cation but can be sight-threatening and can lead to devastating consequences. The incidence of microbial keratitis varies between 1:1000 and 1:5000.22 Most cases present within the first week after surgery; however cases have been reported even after 1 month.
147 Infectious keratitis following LASIK may be early
onset (occurring within the first 2 weeks of surgery) or late onset (occurring 2 weeks to 3 months after surgery).
The organisms seen in early-onset infectious keratitis are common bacterial pathogens such as staphylococcal streptococcal and Pseudomonas (Figs 14.3A and B) species. Gram-negative organisms are rare. The organisms seen in late-onset infectious keratitis are usually opportunistic such as fungi (Fig. 14.4), nocardia, and atypical mycobacteria.
Infectious keratitis following LASIK often presents with inflammation in the corneal interface, which can mimic diffuse lamellar keratitis (DLK). Because of this,
many cases are typically treated with frequent topical corticosteroid therapy that may obscure the clinical picture with transient improvement in the inflammation.
However, unlike DLK, the inflammation associated with LASIK-associated infections usually persists despite topical corticosteroids, and the underlying infections can potentially worsen with corticosteroid tapering.
The appearance of an interface inflammation more than 1 week after LASIK should be presumed to be of an infectious etiology until proven otherwise. Diffuse lamellar keratitis characteristically has a diffuse appearance , while infectious keratitis has a focal area of infiltration surrounded by diffuse inflammation
Figures 14.12A and B: Dandrities due to herpes simplex keratitis following penetrating keratoplasty stained with Rose Bengal dye (A) and florescien (B)
Figures 14.13A and B: Post LASIK keratitis due to Pseudomonas (A) healed on topical therapy (B)
(Figs 14.13A and B) or even focal inflammation limited to the area of the infiltrate. Any focal infiltrate surrounded by inflammation should be presumed infectious until proven otherwise.
Microbiologic Examination
Any focal infiltrate following LASIK should be considered infectious, and the practice of empirical antibiotic treatment without performing cultures of microorganisms should be avoided.
Scraping should be sent for Gram-stain, Gomori-methenamine silver stain, and Ziehl-Neelsen stain to rule out unusual pathogens such as nocardia, atypical mycobacteria, and fungi.The culture media which should be inoculated include blood agar, chocolate agar, Sabouraud’s agar, and thioglycolate broth and Lowenstein-Jensen or Middlebrook 7H-9 agar. If these special media are unavailable, blood agar may be used as atypical media. Mycobacteria grow quite well in this media also. In cases in which cultures are negative and the infection continues to worsen, a corneal biopsy or polymerase chain reaction should be contemplated.
Treatment
The topical corticosteroids should be discontinued. In cases of Post LASIK keratitis fortified cefazolin sodium 5% eyedrops along with tobramycin sulphate 1.3% eye drops are instilled hourly. In cases where there is no response to above therapy and where the flap is edematous irrigation of the flap interface with an appro-priate antibiotic solution (fortified vancomycin 50 mg/
mL for rapid-onset keratitis and fortified amikacin 35 mg/mL for delayed-onset keratitis) may be helpful.
In patients who work in a hospital environment, there is an added risk for methicillin-resistant Staphylococcus aureus (MRSA). In these patients, fortified vancomycin 50 mg/mL may be given instead of cefazolin every 30 minutes to provide more effective therapy against MRSA. In addition, oral doxycycline 100 mg twice a day may be used to inhibit collagenase production.
For delayed-onset keratitis, which is commonly due to atypical mycobacteria,22 nocardia, and fungi, therapy should be commenced with amikacin 35 mg/mL every hour, alternating with a fourth-generation fluoroquino-lone (gatifloxacin 0.3% or moxifloxacin 0.5%).
Clarithromycin 1 percent and Oral Clarithromycin may also be tried in cases which do not respond to amikacin.
Topical medications are generally given for 4 months and systemic medications are given for 2 months.
In cases where total melting of the cornea occurs despite amputation of the flap and maximal medical therapy, a therapeutic keratoplasty may be required to save the eye.
References
1. Garg P, Mahesh S, Bansal AK, Gopinathan U, Rao GN.
Fungal infection of sutureless self-sealing incision for cataract surgery. Ophthalmology 2003;110:2173-7.
2. Cosar CB, Cohen EJ, Rapuano CJ, Laibson PR. Clear corneal wound infection after phacoemulsification. Arch Ophthalmol 2001;119:1755-9.
3. Al-hazzaa SAF, Tabbara KF. Bacterial keratitis after penetrating keratoplasty. Ophthalmology 1988;95:1504-4. Akova YA, Onat M, Koc F, Nurozler A, Duman S.8.
Microbial keratitis following penetrating keratoplasty.
Ophthalmic Surg Lasers 1999;30:449-55.
5. Tavakkoli H, Sugar J. Microbial keratitis following keratoplasty. Ophthalmic Surg 1994;25:350-60.
6. Bates AK, Kirkness CM, Ficker LA, Steele AD, Rice NSC.
Microbial keratitis after penetrating keratoplasty. Eye 1990;4:74-8.
7. Lamensdorf M, Wilson LA, Waring GO III, Cavanagh HD. Microbial keratitis after penetrating keratoplasty.
Ophthalmology 1982;89:124.
8. Sharma N, Gupta V, Vanathi M, Agarwal T, Vajpayee RB, Satpathy G. Microbial keratitis following lamellar keratoplasty. Cornea 2004;23:472-8.
9. Saini JS, Rao GN, Aquavella JV. Post-keratoplasty corneal ulcers and bandage lenses. Acta Ophthalmo-logica 1988;66:99-103.
10. Vajpayee RB, Boral SK, Dada T, Murthy GVS, Pandey RM, Satpathy G. Risk factors for graft infection in India:
A case control study. Br J Ophthalmol 2002;86:261-5.
11. Rehany U, Balut G, Lefler E, Rumelt S. The prevalence and risk factors for donor corneal button contamination and its association with ocular infection after trans-plantation. Cornea 2004;23:649-54.
12. Chittum ME, Grutzmacher RD, Oiland DM, Kalina RE.
Contamination of corneal tissue from infected donors.
Arch Ophthalmol 1985;103:802-5.
13. Driebe WT, Stern GA. Microbial keratitis following corneal transplantation. Cornea 1983;2:41.
14. Dana MR, Goren MB, Gomes AP, Laibson PR, Rapuano CJ, Cohen EJ. Suture Erosion after penetrating kerato-plasty. Cornea 1995;14:243-8.
15. Harris DJ Jr, Stulting RD, Waring GO 3rd, Wilson LA.
Late bacterial and fungal keratitis after corneal transplantation. Spectrum of pathogens, graft survival, and visual prognosis. Ophthalmology 1988;95:1450-7.
149
16. Leahey AB, Avery RL, Gottsch JD, Mallette RA, Stark WJ. Suture abscesses after penetrating keratoplasty.
Cornea 1993;12:489-92.
17. Christo CG, van Rooij J, Geerards AJ, Remeijer L, Beekhuis WH. Suture-related complications following keratoplasty: A 5-year retrospective study. Cornea 2001;
20:816-9.
18. Dandona L, Naduviath TJ, Janarthanan H, et al. Causes of corneal graft failure in India. Indian J Ophthalmol 1998;46:149-52.
19. Dandona L, Naduvilath TJ, Janarthanan M, et al. Survi-val analysis and visual outcome in a large series of
corneal transplants in India. Br J Ophthalmol 1997;
81:726-31.
20. Tseng SH, Ling KC. Late microbial keratitis after corneal transplantation. Cornea 1995;14:591-4.
21. Satpathy G, Vishalakshi P. Microbial profile and sensitivity pattern – a five-year study. Ann Ophthalmol 1995;27:301-6.
22. Daines BS, Vroman DT, Sandoval HP, Steed LL, Solomon KD. Rapid diagnosis and treatment of mycobacterial keratitis after laser in situ keratomileusis.
J Cataract Refract Surg 2003;29:1014-8.