Predicting Prognosis Based on Regional Prevalence, Ulcer Morphology and Treatment Strategy in Vision-Threatening Pythium insidiosum Keratitis

Figures & data

Figure 1 (a) Digital slit-lamp image of the right eye of the patient depicting diffuse conjunctival congestion, 8×8 mm creamy white full-thickness infiltrate (black arrowhead), stromal melt and nasal peripheral furrowing (white arrowhead) with guttering along with 3 mm anterior chamber hypopyon (severe ulcer). (b) Digital slit-lamp image of the right eye of the patient depicting diffuse conjunctival congestion, crescentic eccentric 7×7 mm mid to posterior stromal infiltrate (black arrowhead), inferonasal full-thickness infiltrate, nasal limbal spread (white arrowhead), and central corneal thinning with impending perforation (severe ulcer).

Figure 2 (a) Digital slit-lamp image of the patient depicting diffuse conjunctival congestion, superficial vascularization, total full-thickness corneal infiltrate with 360-degree limbal infiltrate and paralimbal thinning (black arrowhead) with central impending perforation (white arrowhead) (severe ulcer). (b) Digital slit-lamp image of the patient depicting diffuse conjunctival congestion, total graft infiltrate (black arrowhead), graft host junction melt from 1 to 7 o’clock (white arrowhead) and loose sutures along with superficial vascularization.

Table 1 Proposed Modified Jones Criteria for Pythium insidiosum Keratitis (Gurnani and Kaur Severity Grading of Pythium insidiosum Keratitis)^3,5,11

S. No	Feature	Severity Grade of Pythium Ulcer*
		Mild	Moderate	Severe (Figures 1a, b and 2a)
1	Infiltrate size	Less than 2×2 mm	2×2–4×4 mm	Greater than 4×4 mm
2	Depth of infiltrate	Superficial 1/3 (33%)	Up to mid stroma (33–50%)	Mid stroma and beyond (>50%)
3	Depth of ulcer	Superficial 1/3 (33%)	Up to mid stroma (33–50%)	Mid stroma and beyond (>50%)
4	Scleral involvement	Absent	Absent	Present
5	Perforation	Absent	Unlikely	Impending or present
6	Presence of hallmark features	Absent	Reticular dots, tentacles	Peripheral furrowing, limbal spread, early corneal melt
7	Hypopyon	Absent	May or may not be present	Present in most cases

Notes: *Ulcer is labelled as severe when three or more features are present.

Table 2 Hallmark Clinical Features of Pythium insidiosum Keratitis and Its Masqueraders

S. No	Microorganism	Predisposing Risk Factor	Clinical Features
1	Pythium keratitis (hallmark features)^Citation3,Citation5,Citation11,Citation24	Dust, bathing in pond water, stick injury, clay injury	Reticular dot infiltrates, tentacular lesions, multifocal infiltrate, peripheral furrowing, stromal infiltrate with hyphated edges, guttering, early limbal spread, corneal melt
Masqueraders*
1	Fungal keratitis^Citation3,Citation5,Citation11	Vegetative matter trauma, steroids, malnourishment, surgery	Epithelial defect, subepithelial and stromal infiltrate with feathery margins, satellite lesions, endo-exudates, hypopyon, ring infiltrate, perforation, gradual limbal involvement
2	Bacterial keratitis^Citation38	Insect, fall, surgery, blunt trauma, steroids, contact lens	Symptoms more than signs, greenish discharge, epithelial defect, stromal infiltrate, corneal melt, dense white cheesy suppuration, corneal abscess, endo-exudates, hypopyon, perforation
3	Acanthamoeba keratitis^Citation36	Contact lens (West), mud injury, bathing in pond water (India)	Satellite lesions, focal infiltrates, ring infiltrates, stromal infiltrates, radial keratoneuritis
4	Atypical mycobacterial keratitis^Citation31	Post-LASIK, trauma, steroids, contact lens	Epithelial defect, dry greyish white stromal infiltrate and oedema, Descemet folds, cracked windshield appearance
5	Peripheral ulcerative keratitis^Citation37	Connective tissue disease, idiopathic	Peripheral guttering, crescentic stromal infiltrate, cellular reaction, stromal oedema, stromal melt, corneal perforation

Notes: *All of these clinical features can be present in Pythium keratitis besides the hallmark features listed above.

Figure 3 The novel diagnostic and management protocol of Pythium insidiosum keratitis.

Abbreviations: KOH, potassium hydroxide; IKI-H₂SO₄, iodine potassium iodide–sulfuric acid; BA, blood agar; CA, chocolate agar; PDA, potato dextrose agar; RX, treatment; TPK, therapeutic keratoplasty.

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