Skip to main content

Table 3 Informative morphological characters and measurements of different stage of helminths infecting human eyes [41, 63].

From: Zoonotic helminths affecting the human eye

Parasite Location Size Comments Stage*
Toxocara canis Intraocular ≤ 400 μm × 15-21 μm Smallest of the nematode larvae encountered in the eye ML
Baylisascaris spp. Intraocular 1-2 mm × 50-60 μm Relatively small but easily recognized as being larger than Toxocara larvae ML
Gnathostoma spp. Intraocular 1-5 mm × 200-600 μm Much more robust than other nematode larva; presence of cuticular spines and head bulb distinctive ML
Angiostrongylus spp. Intraocular ≤1-2 cm × 200-300 μm One of the larger, more robust worms found in intraocular location L, SA
Thelazia callipaeda Eye socket 5-20 mm × 250-800 μm Distinct morphologic features; free in orbit A, L
Philophthalmus Intraocular 2-3 mm × 600-800 μm Ovoid to oblong, flat, solid body ML, SA
Spargana Intraocular or eyelid 5-20 mm × 1-2 mm Long, flat solid body with pseudosegmentation ML
Coenurus Intraocular < 1 cm Fluid filled cyst ovoid in shape and of variable size L
Dirofilaria tenuis/Dirofilaria repens Conjunctiva 2-15 cm × 150-400 μm Males smaller than females; most often closely associated with conjunctiva; worms in the eye are appreciably smaller than those on conjunctiva L
Dirofilaria immitis Intraocular 1-1.65 cm × 160-400 μm Not a common location for this worm and very few confirmed cases exist L
  Conjunctiva 10 cm × 300 μm   SA
Onchocerca spp. Intraocular 3-5 cm × 80-100 μm   L
  Conjunctiva total length unknown but several cm or more × 150-250 μm   L, SA
Acanthocheilonema spp. Intraocular 1.6 - 2.1 cm × <100 μm Accurate identification to species has been L, SA
  Conjunctiva 3.2 cm × <150 μm   
  1. *Larva = L; Migrating larva = ML; SA = Subadult; A = Adult