Eye myiasis is the infestation of the eye by the larval stage, or maggots, of certain fly species. Though uncommon globally, it is a significant medical concern. This parasitic infestation involves larvae developing within or on ocular tissues, potentially causing discomfort and damage. Prompt medical attention is crucial due to the potential for serious complications.
Understanding Eye Myiasis
Eye myiasis, also known as ophthalmomyiasis, is a parasitic infestation caused by the larval stage of various fly species, such as the sheep bot fly (Oestrus ovis). It is classified based on the anatomical location of the infestation within or around the eye.
Ophthalmomyiasis Externa
This involves the outer structures of the eye, including the conjunctiva and eyelids. Larvae are often found on the surface or within the conjunctival sac, deposited directly by the adult fly. This form is generally less severe but can cause considerable irritation.
Ophthalmomyiasis Interna
This refers to larvae within the eyeball itself, affecting the vitreous humor, retina, or subretinal space. This internal form is less common but carries a higher risk of severe visual impairment, often resulting from larvae migrating from the external surface or even from distant sites through the bloodstream.
Orbital Myiasis
This is the most severe classification, where larvae infest the tissues surrounding the eyeball, causing extensive tissue destruction. Larvae can enter the eye through direct deposition by the adult fly or migrate from other infested areas of the face or body.
How Myiasis Affects the Eye
The presence of fly larvae within or around the eye causes a range of symptoms and significant tissue damage, depending on the myiasis type and location. For ophthalmomyiasis externa, common symptoms include a foreign body sensation, intense itching, redness, tearing, eyelid swelling, and a visible crawling sensation.
Larvae cause mechanical irritation as they move and feed on superficial tissues. Their movement can abrade the conjunctiva and cornea, leading to inflammation and predisposing the eye to secondary bacterial infections.
Ophthalmomyiasis Interna Symptoms
Symptoms are often more severe, including significant vision impairment, floaters, and severe pain. Larvae within the globe can cause inflammation of the retina or choroid. Their activity can directly damage delicate intraocular structures, potentially resulting in retinal detachment or vitreous hemorrhage.
Orbital Myiasis Symptoms
This presents with severe pain, extensive swelling of the eyelids and surrounding facial tissues, and proptosis (eyeball protrusion). Larvae burrow deeply into periorbital tissues, consuming tissue. This destructive process can lead to significant tissue loss, orbital cellulitis, and may even extend into the brain.
Identifying and Treating Eye Myiasis
Identifying eye myiasis typically begins with a thorough visual examination of the affected eye.
Diagnosis
For ophthalmomyiasis externa, the larvae are often directly visible on the conjunctiva or eyelids, appearing as small, motile, translucent or white organisms up to 5mm in length. An ophthalmologist will use a slit lamp to magnify the ocular surface and identify the larvae, which may be difficult to remove due to their strong attachment. For suspected ophthalmomyiasis interna or orbital myiasis, more advanced diagnostic imaging techniques may be employed. Ultrasound can reveal the presence and movement of larvae within the globe or orbital tissues, while CT scans or MRI may be used to assess the extent of tissue destruction and identify larvae in deeper structures. These imaging modalities help determine the precise location and number of larvae, guiding the treatment approach.
Treatment
The primary treatment for eye myiasis involves the careful and complete removal of the larvae. For external infestations, this can often be done manually using forceps under topical anesthesia, ensuring all larvae are extracted to prevent recurrence. The removal process aims to minimize further tissue damage while ensuring no larval fragments remain, which could continue to cause irritation or infection. Following larval removal, adjunctive medical treatments are frequently administered to manage associated symptoms and prevent complications. Antibiotics are commonly prescribed to address or prevent secondary bacterial infections that can arise from the compromised ocular surface. Anti-inflammatory medications, such as corticosteroids, may be used to reduce swelling and discomfort. Prompt medical attention is important, as delayed treatment can lead to more extensive tissue damage, permanent vision loss, or in severe orbital cases, even systemic complications.
Preventing Eye Myiasis
Preventing eye myiasis involves implementing several practical measures, particularly in regions where myiasis-causing flies are prevalent. Maintaining good personal hygiene is a fundamental step, including regular washing of the face and hands, which can help remove any eggs or newly hatched larvae before they can establish an infestation. Avoiding direct contact with flies, especially those known to cause myiasis, is also important.
Using insect repellents containing active ingredients like DEET or picaridin on exposed skin can deter flies from landing and depositing eggs or larvae. When spending time outdoors, particularly in rural or agricultural areas where myiasis is more common, wearing protective clothing such as wide-brimmed hats and sunglasses can provide a physical barrier. Fine-mesh netting over windows and doors can also prevent flies from entering homes and other enclosed spaces.
Proper care for open wounds or skin lesions, especially those located on the face, is also a significant preventive measure. Wounds should be promptly cleaned and covered with sterile dressings to prevent flies from being attracted to the site and laying eggs. Flies are often drawn to open sores, and larvae from these sites could potentially migrate to the eye.