Superficial punctate keratitis: A diagnostic dilemma.

A30-year-old immunocompetent male presented to our outpatient department with complaints of pain, redness, and watering and hazy vision in the left eye for the past 1 week. He had a history of swimming in a pond 10 days back. Visual acuity was 6/6 in the right eye and 6/9 in the left eye. Slit-lamp biomicroscopic examination revealed diffuse, multifocal, coarse, raised, punctate epithelial lesions on the cornea that stained negatively with fluorescein [Figure 1]. The underlying stroma was normal. The conjunctiva showed a papillary response. The raised corneal lesions were scraped using number 15 blade, smeared on a glass slide, and stained with Gram stain. Microbiology examination of the slide revealed numerous Gram-positive, oval, nonbudding bodies under ×100 oil immersion field [Figure 2]. The oval bodies were 1% acid fast. He was treated with topical gatifloxacin 0.5% eye drops six times a day for 10 days. The lesions healed completely, and vision returned to 6/6 after 10 days.

Figure 1

Slit-lamp photograph in diffuse illumination showing punctate epithelial lesions with a “stuck-on appearance” on the cornea

Figure 2

Microbiology examination of the corneal smear (Gram stain, ×100, oil immersion) demonstrating multiple Gram-positive, oval, nonbudding structures

What is the diagnosis?

Microsporidial epithelial keratoconjunctivitis

Adenoviral keratoconjunctivitis (AK)

Thygeson's superficial punctate keratopathy (TSPK)

Keratitis medicamentosa.

Which is the peak season for this condition?

Winter

Summer

Rainy

Spring.

What is the best treatment option for this patient?

Observation

Topical antibiotics plus steroids

Corneal scraping alone

Scraping plus topical antibiotics.

Answers

a

c

d.

Discussion

Microsporidia are unicellular, spore-forming parasites. Conventionally, these were considered as Protozoans, but, more recently, these have been classified as fungi.[1] There are two distinct forms of keratitis caused by this organism – epithelial keratoconjunctivitis and stromal keratitis. Keratoconjunctivitis is more common form of the disease. Contrary to the olden belief, this infection can be seen in immunocompromised as well as immunocompetent individuals.[123] The incidence rises dramatically during the rainy season, as contaminated water is the most common source of infection.[123] Clinically, it needs to be differentiated from other causes of superficial punctate keratitis such as AK and TSPK. Microsporidial keratoconjunctivitis is characterized by unilateral, diffuse, monomorphic, coarse, elevated SPKs with round borders. There is no associated lymphadenopathy, and all lesions heal well with supportive therapy alone, without any scarring. Corneal scraping helps in laboratory diagnosis as well as debulks the infectious load.[123] Prophylactic topical antibiotics prevent secondary infection. Topical steroids should be avoided as they can lead to persistence of the organism within the epithelial cells. In contrast, SPKs of AK are less coarse and are usually associated with subepithelial infiltrates involving the anterior stroma. This can be very well appreciated on anterior segment optical coherence tomography. Lesions are pleomorphic and are usually associated with preauricular lymphadenopathy. Treatment usually requires antibiotics and steroids and scarring is common despite adequate treatment. TSPK, on the other hand, presents with chronic remissions and exacerbations. SPKs are typically central, are monomorphic, and have “crenated” edges. They respond dramatically to topical steroids and heal without scarring.

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Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.