**5. Predisposing factors**

Endoftalmitis: Present with severe pain, decreased vision, and redness and discharge, may exist hypopyon, and variable amounts of granulomatous keratitic precipitates. Moderate vit‐

Keratitis: The greatest number of recent clinical reports of nontuberculous Mycobacteria oc‐ ular infections are of keratitis, as seen in our hospital (Asociación Para Evitar La Ceguera en México "Dr. Luis Sánchez Bulnes" I.A.P. [APEC]). Keratitis most commonly follows trauma or surgery and has been associated with penetrating keratoplasty and refractive surgery.

Nontuberculous Mycobacteria keratitis is characterized by a delayed onset of symptoms that range typically from 1 to 3 weeks following the exposing event. There is decreased vi‐ sion and an indolent course and some cases various degrees of pain, ranging from indolent

Presenting symptoms can include any of the following: pain, redness, photophobia, de‐ creased vision, foreign body sensation and/or mild irritation. Presenting clinical signs in‐ clude infiltrates in the corneal interface that can either be multiple white granular opacities <0.5mm in diameter with well defined borders or radiating projections, or a single white round lesion (0.1-2 mm in diameter) which may progress to satellite lesions. These infiltrates spread subsequently into the corneal stroma posteriorly and anteriorly and can result in per‐ foration though the flap to surface. [Table 2].A hypopyon is often found in untreated or

Lazar and colleagues first described the presence of a "cracked windshield" appearance to the cornea around the edge of the central area of ulceration and infiltrate, seen transiently early in the course of the infection. [25,27,28] This sign consist of radiating lines from the central infiltrate in the middle third of the corneal stroma. It is important to mention that NTM keratitis has also been noted in the abscence of epithelial defect with deep stromal ker‐

> Pain (mild) Redness Photophobia Tearing

Foreign body sensation Decreased visual acuity

reous inflammation is present in most cases.

to severe.

152 Common Eye Infections

poorly treated cases. [25,26]

atitis. The corneal infiltrate may show irregular margins.

**Signs Symptoms**

**Table 2.** Signs and symptoms of keratitis caused by mycobacterias

Single or multiple white granular opacities with well

defined borders or radiating projections

Mild or absent anterior chamber reaction

"Cracked windshield" appearance

Satellite infiltrates

Hypopyon

Nontuberculous Mycobacteria are opportunistic pathogens that require an alteration in the ocular barriers to produce infection. In nearly all reports, a previous history of minor to severe trauma is the common denominator.Men and women are equally affected among NTM keratitis patients who have had LASIK, in contrast to a 70% male prepon‐ derance among patients who have not had LASIK, the result of a higher prevalence of trauma in males. [Table 3] [5,29]


**Table 3.** Risk factors for the development of nontuberculous mycobacterial keratitis.

**Post-LASIK NTM keratitis:** Laser in situ keratomileusis (LASIK) is the most commonly performed refractive surgical procedure, since it offers rapid visual rehabilitation, de‐ creased stromal scarring, less postoperative pain, and the ability to treat a wider range of refractive disorders. LASIK preserves the integrity of Bowman's membrane and the overly‐ ing epithelium, thus decreasing the risk for microbial keratitis. Several studies have report‐ ed an incidence of bacterial infection following LASIK procedures varying between 0% to 1.5%. [29,31,32] Solomon et. al published the first survey that provides information about post-LASIK infectious keratitis. The most common organisms cultured were nontubercu‐ lous mycobacteria (48%) and staphylococci (33%).. These findings are consistent with Chang's research, where he found that nearly 47% of infectious keratitis cases after LASIK appear to be caused by NTM; 32% being caused by *Mycobacterium chelonei* alone. In con‐ trast to the acute or subacute onset of symptoms generally seen postoperatively in bacteri‐ al and fungal keratitis, rapid growing atypical mycobacteria may present with a slower onset of clinical disease, from 3 to 14 weeks (3.5 weeks in average) after the procedure. It is important to keep in mind that this is not a rule, and more rapidly growing NTM such as the *Mycobacterium chelonae-abscessus* group may present as soon as 10 days posterior to the refractive surgery. [1,33,34]

Innoculation of NTM to the flap-stromal interface probably takes place at the time of sur‐ gery, therefore, it is infrequent to find an epithelial defect, being present in less than half of cases. Corneal infiltrates appear to be entirely within the lamellar flap or at the flap inter‐ face and may be either multiple, tiny, white, granular opacities less than 0.5mm in diame‐ ter or a single white lesion ranging between 0.1-0.2mm in diameter. Anterior extension of infiltrate with ulceration or anterior perforation of the corneal flap or posterior extension in‐ to the stroma is a rare finding and is usually associated with a delay in diagnosis and the beginning of therapy. Anterior chamber reaction is not a common finding, occurring in on‐ ly 20% of cases.[1,29]
