Microbial Keratitis in Thyroid Eye Disease: Clinical Features, Microbiological Profile, and Treatment Outcome
Authors: Naik Milind N. , Vasanthapuram Varshitha Hemanth , Joseph Joveeta , Murthy Somasheila I. 
Published: March 2019

Microbial Keratitis occurs in 1.3% cases of Thyroid Eye Disease. It is more common in men, and in active disease. The microbiological spectrum and possible clinical risk factors are presented.

Purpose:
To report the incidence, clinical features, microbiologic profile, and risk indicators in the development of microbial keratitis in Thyroid Eye Disease (TED).

Methods:
All patients who were diagnosed to have TED and developed microbial keratitis between the years 2009 to 2017 at the Ophthalmic Plastic Surgery service, LV Prasad Eye Institute were included in this retrospective interventional study. The clinical features, microbiological profile, and treatment outcome of the infection were studied. Possible risk factors leading to the development of microbial keratitis were studied.

Results:
A total of 1,000 patients of TED were evaluated in the 10-year period. Of the 1,000, 13 patients (14 eyes, 1.4%) were diagnosed with microbial keratitis. The average age at presentation was 44 years (range 1969 years). Of the 13 patients, 10 (77%) were men, 12 (92%) were hyperthyroid, and 12 (92%) were active (average clinical activity score 3) at presentation. Average exophthalmometry value in the involved eye was 24.75mm, and severe eyelid retraction (>2mm scleral show) was noted in 13 of 14 eyes. None of the patients had optic nerve compression. Moderate motility restriction (2 in all gazes) was noted in 6 eyes, and severe motility restriction (4 in all gazes) in 8 eyes. At presentation, 11 (85%) had visual acuity of counting fingers at 1 meter or less, The mean follow up from the time of presentation was 18.3 months (range 566 months). Majority of the eyes (8/14) presented with severe infection (panophthalmitis with microbial keratits = 1, total corneal infiltrate with/without melt = 4, severe thinning/perforation = 4). Microbiological work up of 14 eyes revealed presence of gram-negative bacteria in 5 eyes which included Escherichia coli, Pseudomonas sp., and Acinetobacter sp., and gram-positive bacteria in 4 eyes including Streptococcus pneumoniae, Corynebacterium sp., and Staphylococcus sp. Three eyes revealed a mixed infection of E. coli with Alternaria sp, and E. coli with Corynebacterioum amycolatum while 1 had Corynebacterium pseudodiptheriticum, and S. pneumoniae. Two eyes of the bilateral case showed no growth. Antibiotic susceptibility revealed 6 of the 7 gram-negative isolates were multidrug resistant, whereas the gram-positive isolates were susceptible to most drugs tested. Surgical procedures required were tarsorrhaphy in 7 eyes, tissue adhesive with bandage contact lens in 4, evisceration in 4, levator recession in 2, 3-wall orbital decompression in 2, and penetrating keratoplasty in 1 eye. The visual acuity at presentation was counting fingers or worse in 10/14 eyes. Posttreatment, 10 eyes achieved resolution of infiltrate (with visual improvement in 2), and 4 required evisceration.

Conclusions:
In the authors large series of TED, microbial keratitis was noted in 1.3% of patients presenting to a tertiary eye center. Majority presented with advanced diseases and ended with a poor outcome. Gram-negative isolates showed multidrug resistance. An association with early phase of active TED (CAS 3 or more), severe eyelid retraction, and moderate-severe motility restriction is suggested.