{"id":5024,"date":"2015-06-19T16:29:50","date_gmt":"2015-06-19T16:29:50","guid":{"rendered":"http:\/\/phosdev.com\/todaysveterinarypractice\/?p=5024"},"modified":"2022-02-18T15:09:00","modified_gmt":"2022-02-18T15:09:00","slug":"observations-ophthalmology-answers-corneal-opacities-dogs-cats","status":"publish","type":"post","link":"https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/ophthalmology\/observations-ophthalmology-answers-corneal-opacities-dogs-cats\/","title":{"rendered":"Answers to What, Where, Why, and When? Corneal Opacities in Dogs and Cats"},"content":{"rendered":"

The cornea is transparent, densely innervated, avascular, and the major refractive structure of the eye. A healthy cornea achieves and maintains transparency due to the organization of constituent cells and collagen fibers, as well as its relatively dehydrated state. Anything that alters this organization or deturgescence leads to development of a corneal opacity.1<\/sup><\/p>\n

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Welcome to Observations in Ophthalmology<\/strong>, a new column in Today\u2019s Veterinary Practice<\/em><\/strong>. The articles in this column will provide succinct nuggets of knowledge about common (and sometimes uncommon) ophthalmic conditions seen in general practice. Authors will share clinical tools, including their own approaches to diagnosis and treatment, that practitioners can use to better care for their patients.<\/p>\n

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As the outer and most exposed structure of the globe, the cornea is not only at risk for trauma, but also often receives close attention from clients. As such, a presenting complaint of corneal opacity is common in veterinary practice.<\/p>\n

Correct interpretation of corneal changes is critical for diagnosing corneal disease as well as many other ocular and some systemic diseases. Therefore, appropriate diagnostic tests and prompt initiation of optimal therapy are required to maximize the chance of saving vision, producing a comfortable globe and, occasionally, saving the patient\u2019s life.<\/p>\n

The following questions should be asked when a patient with a corneal opacity is presented for evaluation.<\/p>\n

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Tools for Ophthalmic Examinations<\/strong><\/h2>\n

Fortunately, diagnosis of corneal opacities is possible with just a few pieces of inexpensive equipment. Among these, a dark room, magnification, and a bright and focal light source are key for a good ophthalmic examination.2<\/sup><\/p><\/blockquote>\n

Question 1. What Is the Appearance of the Opacity?<\/h2>\n

Causes of corneal opacities, which are often seen in various combinations, are listed in Table 1<\/strong>.2<\/sup> Each of these pathologic changes is associated with a specific appearance\u2014especially color. However, assessment of texture, depth, location, pattern, shape, and outline of the region of opacification is also important as some colors can look similar.<\/p>\n

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Edema<\/strong><\/h3>\n

A blue, \u201ccobblestoned\u201d appearance of the cornea\u2014whether focal or diffuse\u2014is indicative of corneal stromal edema, and results from loss of corneal epithelial or endothelial cell function.<\/p>\n

Focal Edema.<\/strong> Specific causes of focal edema include focal corneal epithelial dysfunction (due to corneal ulceration), or focal endothelial cell damage (due to blunt corneal trauma, lens luxation, or keratic precipitates) (Figure 1<\/strong>).2<\/sup><\/p>\n

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FIGURE 1. Focal corneal edema secondary to corneal ulceration in a dog. The pupil has been pharmacologically dilated. Note the loose epithelial edges of the corneal ulcer suggestive of a superficial chronic corneal epithelial defect (SCCED). Resolution was achieved by debridement (using a sterile cotton-tipped applicator) and topically applied antibiotics and atropine. Courtesy University of California\u2013Davis Comparative Ophthalmology Service<\/em><\/p><\/div>\n

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Diffuse Edema.<\/strong> Diffuse corneal edema (Figure 2<\/strong>) is more consistent with intraocular disease, such as glaucoma or uveitis, but may also indicate breed-related endothelial dystrophy or age-related endothelial degeneration. These conditions can usually be differentiated by assessing for signs of pain or inflammation: the latter 2 conditions are nonpainful and noninflammatory, whereas glaucoma and uveitis are painful and associated with other signs of inflammation.<\/p>\n

Whenever possible, treatment for diffuse corneal edema should always be directed at the underlying disease process, especially since both glaucoma and uveitis are vision-threatening diseases, and some causes of uveitis can even be life-threatening.2,3<\/sup> When no cause is found or the underlying disease is untreatable, symptomatic treatment with hypertonic sodium chloride (NaCl) ophthalmic ointment may be attempted, but it often has little to no effect, may irritate the eye, and requires administration at least 4 to 6 times daily.<\/p>\n

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FIGURE 2. Diffuse corneal edema in a dog with a penetrating corneal cat claw injury and secondary uveitis. The wound from the cat claw can be seen on the ventromedial paraxial cornea. Courtesy University of California\u2013Davis Comparative Ophthalmology Service<\/em><\/p><\/div>\n

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Diffuse Edema in Cats.<\/strong> Cats are rarely affected with endothelial dystrophy or senile endothelial degeneration. Instead, severe, diffuse corneal edema in cats is typically seen with acute bullous keratopathy (Figure 3<\/strong>). This condition, which is more common in younger cats, has no recognized predisposing cause and an extremely acute onset that leads to massive stromal edema and, sometimes, corneal rupture. The dysfunction may involve the stroma itself rather than the endothelium or epithelium. Treatment involves emergency surgical support\u2014either conjunctival grafting or placement of a third eyelid flap.4,5<\/sup><\/p>\n

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FIGURE 3. Feline acute bullous keratopathy. Note the large corneal stromal bulla protruding outwards. The lack of corneal vascularization confirms the acute nature of the disease. Mucous discharge covers some of the dorsomedial cornea and bulla. Courtesy University of California\u2013Davis Comparative Ophthalmology Service<\/em><\/p><\/div>\n

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Inflammatory Cell Infiltration<\/strong>
\nA yellow, green, or tan corneal stromal opacity suggests white blood cell (WBC) infiltration, which is most frequently caused by bacterial infection of the cornea, often Pseudomonas<\/em> or beta-hemolytic Streptococcus<\/em> species (Figure 4<\/strong>). Melting of the corneal stroma (keratomalacia), sometimes with associated stromal loss, often is seen in conjunction with WBC infiltration. Keratomalacia is evident as loss of normal corneal curvature and architecture with \u201coozing\u201d of softened sections of the cornea over the more dependent regions (Figure 4<\/strong>). It occurs as a result of enzymatic breakdown of corneal collagen by collagenases of WBC and bacterial origin, especially Pseudomonas<\/em> species.6<\/sup><\/p>\n

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Therapeutic Approach.<\/strong> Cytology, aerobic bacterial culture, and sometimes fungal culture are strongly recommended to help guide therapy. Infected corneas require intensive medical therapy, including:<\/p>\n