Ophthalmology Challenge: Aggressive ulcerative keratitis in a dog - Veterinary Medicine
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Ophthalmology Challenge: Aggressive ulcerative keratitis in a dog

Diagnosis and additional treatment

We diagnosed keratomycosis based on the clinical presentation and the fungal culture and corneal cytology results. Unfortunately, because of this dog's fractious nature, we could not perform corneal cytology at the initial presentation, so specific antifungal therapy was delayed until culture results were available. We modified the therapy on Day 3 by initiating 5% natamycin suspension (Natacyn—Alcon Laboratories) given in the left eye three times a day and decreasing the tobramycin administration to three times a day.


Figure 3. The left eye on Day 5 stained with fluorescein stain. Note the brown-pigmented ring around the center of the corneal opacity and limbal vessels migrating toward the lesion.
On Day 5, the ulcerated corneal stroma appeared firmer and less gelatinous, the pupil was 75% dilated, the limbal vessels continued to migrate toward the lesion, and the blepharospasm and conjunctival hyperemia had improved slightly. A brown-pigmented ring had formed around the edge of the corneal opacity (Figure 3). We increased the natamycin administration frequency to every four to six hours in the left eye, and we discontinued the acetylcysteine. Schirmer tear test results in the left eye had decreased to 8 mm/min.

On Day 9, Schirmer tear test results had increased to 16 mm/min in the left eye and 14 mm/min in the right eye. A brown corneal lesion had formed in the center of the corneal opacity of the left eye; the lesion had a rough center and a smooth peripheral ring. The dog appeared to be more comfortable, and the peripheral cornea was smoother. Both superficial and deep corneal vessels continued to migrate toward the lesion. We decreased the atropine administration frequency to once a day and continued the remaining treatments in the left eye (natamycin every four hours, autogenous canine serum q.i.d., tobramycin t.i.d.). We also continued the oral carprofen.

On Day 12, the fluorescein-positive area had decreased to 9 x 6 mm, and the brown ring had become more prominent. Schirmer tear test values were 9 mm/min in the right eye and 15 mm/min in the left eye. Peripheral corneal neovascularization had extended 3 mm from the limbus. A repeat corneal culture produced scant growth of Acremonium species. Therapy was unchanged except for adding artificial tears in the right eye twice a day.


Figure 4. The left eye on Day 15 stained with fluorescein. Corneal vessels have reached the lesion's edge. Clearing in the periphery is present, and the brown-pigmented ring is no longer apparent.
On Day 15, the left eye appeared less painful and had less discharge. Corneal vessels had reached the edge of the lesion. Clearing in the periphery was present, and the brown-pigmented ring was gone (Figure 4); however, the plaque was still present. The fluorescein-positive area measured 9 x 5 mm. Therapy was continued unchanged.


Figure 5. The left eye on Day 19 stained with fluorescein. The fluorescein-positive area measures 8 x 6 mm. Corneal vessels remain at the lesion's edge, with the limbal cornea continuing to clear.
On Day 19, the owner reported that the dog exhibited fewer signs of pain and held the eye open more frequently. The iris was now clearly visible. The fluorescein-positive area measured 8 x 6 mm. Corneal vessels remained at the edge of the stained region, with the limbal cornea continuing to clear (Figure 5). No changes were made in the treatment plan.


Figure 6. The left eye on Day 26 stained with fluorescein. The fluorescein-positive area has decreased markedly, measuring only 6 x 3 mm with corneal vessels perfused to the lesion's edge. The corneal stroma is continuing to clear peripherally.
On Day 26, Schirmer tear test values were 14 mm/min in the right eye and 12 mm/min in the left eye. The owner reported that the dog was squinting occasionally. Applanation tonometry showed an intraocular pressure of 13 mm Hg in both eyes. The left pupil was widely dilated. The fluorescein-positive area had decreased markedly, measuring only 6 x 3 mm. Corneal vessels had progressed to the edge of the plaque, and the corneal stroma was continuing to clear peripherally (Figure 6). We modified the therapy by decreasing carprofen administration to once a day and discontinuing the artificial tears in the right eye.


Figure 7. The left eye on Day 43 stained with fluorescein. The cornea is fluorescein-negative with only ghost vessels and granulation tissue remaining.
On Day 33, the owner reported that the dog's left eye appeared comfortable and was always wide open. The entire cornea was fluorescein-negative. We decreased both the natamycin and autogenous canine serum frequencies to three times a day, decreased atropine administration to every other day, continued tobramycin at three times a day, and discontinued the oral carprofen.


Figure 8. The left eye on Day 82. A white stromal scar remains with few perfused vessels and no granulation tissue.
On Day 43, the left cornea remained fluorescein-negative. The dog showed no discomfort in the left eye, and only ghost vessels and granulation tissue remained (Figure 7). We discontinued all medication at this point. A final visit on Day 82 revealed only a white stromal scar with few perfused vessels and no granulation tissue (Figure 8).


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Source: VETERINARY MEDICINE,
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