A challenging case: A dog with a painful red eye - Veterinary Medicine
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A challenging case: A dog with a painful red eye
This dog's problem was not conjunctivitis—as was first thought–but something much more serious.


VETERINARY MEDICINE


Diagnosis

Intraocular foreign bodies are diagnosed based on a combination of appropriate history, clinical signs, and ocular imaging. As in the case presented here, there may be a history of the dog running through grass, and grass awns may have been found in the ears or coat or between the toes.

Clinical signs usually start as conjunctival and episcleral hyperemia, prolapse of the third eyelid secondary to enophthalmos (due to pain or a retrobulbar mass), blepharospasm, and epiphora. The signs frequently progress to severe hyperemia, mucopurulent discharge, possible exophthalmos, and severe pain around the face and upon opening the mouth. The dog is often febrile, anorectic, and depressed.

In this case, the clinical signs and history were compatible with a diagnosis of infectious panophthalmitis, and the dog was blind and in severe pain. Thus, a grave prognosis for saving the eye was given, and enucleation was performed without further diagnostic tests. Other causes of panophthalmitis in dogs include deep fungal infections or ophthalmomyiasis interna.7 A diagnosis of ophthalmomymiasis carries a fair prognosis because the larvae can be surgically removed if caught early.7 However, if panophthalmitis develops, salvaging the eye is unlikely.

In cases in which intraocular foreign bodies are suspected, the signs are less severe, and the eye potentially retains vision, ocular imaging techniques should be used to better determine the feasibility of salvaging vision. That is true in cases of suspected intraorbital foreign bodies, as well.

Ultrasonographic examination of the globe and orbit is the most useful technique for determining the amount and type of damage.8 Glass, metallic or plastic objects, and porcupine quills can be easily located with ultrasonography since these objects prevent penetration of the ultrasound waves beyond them and, thus, cast a hypoechoic shadow.8 On the other hand, organic material cannot be imaged as well since it is often of a similar consistency as the tissue around it. However, ultrasonography is valuable in these cases as it can detect prognostic indicators such as retinal detachment and the status of the lens capsule. When information is needed about the complete orbit and globe, a combination of modalities is recommended since intraocular structures are better seen with high-resolution ultrasonography, while periocular structures are better imaged with magnetic resonance imaging (MRI).9

Computed tomography (CT) and MRI are frequently used to detect intraocular foreign bodies in people. In a study comparing these two techniques, MRI was able to accurately detect eight of eight nonmetallic foreign bodies (wood, glass, plastic, rock) planted into enucleated sheep eyes while CT was able to detect seven of eight.10 CT was unable to detect the wood foreign body. Both techniques could resolve objects as small as 3 mm. If a metallic foreign object is suspected, MRI is contraindicated since the magnetic field will attract the metal and potentially traumatically extract it from the tissue.

Prognosis and treatment

The prognosis and treatment of a canine eye with intraocular foreign bodies depend greatly on the initial damage done to the eye, the type of material present, the duration of time from insult to treatment, and the skill of the person treating the eye.

If the foreign body has only penetrated the cornea and has not reached the lens and the trauma is recent, its removal, corneal repair, and topical and systemic antibiotic therapy are indicated. In addition, treatment for the resultant secondary uveitis should be initiated with topical atropine and nonsteroidal anti-inflammatory drugs. Without direct involvement of intraocular structures and given prompt, appropriate therapy, the prognosis is good.

If there is perforation of the sclera and uvea, retinal damage is likely to be present. In these cases, referral to a veterinary ophthalmologist is highly recommended. The prognosis in cases of perforation depends greatly on the location of the object within the eye. If the object can be readily removed from the eye surgically (e.g. if it is in the anterior chamber), the prognosis for vision is good. If it is in the posterior segment, the prognosis—even with surgery—is guarded to poor. However, resolution of hemorrhage and surgical retinal reattachment is possible.4

If perforation of the lens capsule has occurred, a guarded prognosis must also be given. Rapid leakage of lens proteins induces phacoclastic uveitis, which is often progressive and can destroy the eye. Immediate diagnosis and aggressive anti-inflammatory treatment along with the surgical removal of the lens is necessary to have any chance at all of saving the eye.4 Thus, emergency referral to a veterinary ophthalmologist is important in most cases of ocular perforation. If an eye containing a foreign body is blind and painful, enucleation should be performed as soon as possible.

In some cases, it is possible to leave the foreign material in the eye and retain vision.5 In a series of case reports of four eyes of three dogs containing lead shot, intensive antibiotic and anti-inflammatory therapy was used to control the signs and prevent infection. All dogs recovered but not without sequelae, such as cataracts, retinopathies, and posterior synechiae. The fact that the foreign bodies in these dogs was made of lead afforded a better prognosis since "inert metallic foreign bodies with smooth edges such as gunshot are well-tolerated in the anterior chamber, iris, vitreous, and lens."5

In people, the most common intraocular foreign bodies are metal from hammering metal on metal.11 These foreign bodies usually enter the eye through the cornea and progress to varying depths within the eye. Because most of these metallic objects are small, reported immediately by the patient, and, thus, removed rapidly, there is a good prognosis for a positive visual outcome. In a retrospective study of 59 people undergoing foreign body removal, the best results were obtained when there was vision at the time of presentation, hammering metal on metal was the mechanism of injury, and surgical removal, which included vitreous removal (vitrectomy), was within 24 hours.12 Poor prognostic factors were absence of vision at presentation, posterior location of the foreign body, and large size of the foreign object.12 Unfortunately, because dogs are unable to report trauma to their owners and are prone to larger intraocular foreign bodies than people are and because of the relative paucity of veterinarians who are able to do posterior ocular segment surgeries, the prognosis is much worse in veterinary patients.

Juliet R. Gionfriddo, DVM, MS, DACVO
Department of Clinical Sciences
College of Veterinary Medicine and Biomedical Sciences
Colorado State University
Fort Collins, CO 80523

Thomas Chen, DVM
Department of Clinical Sciences
College of Veterinary Medicine and Biomedical Sciences
Colorado State University
Fort Collins, CO 80523


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Source: VETERINARY MEDICINE,
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