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