HOW-TO SESSION: OPHTHALMOLOGY How to Diagnose the Cloudy Eye Caroline Monk, DVM*; Nicole Scherrer, DVM; and Mary L. Utter, DVM, Diplomate ACVO Authors’ addresses: University of Florida, College of Veterinary Medicine, 2015 SW 16th Ave., Gainesville, FL 32608 (Monk); University of Pennsylvania, New Bolton Center, 382 West Street Road, Kennett Square, PA 19348 (Scherrer, Utter); e-mail: monkc@ufl.edu. *Corresponding and present- ing author. © 2013 AAEP. 1. Introduction ● Stromal abscess ● Diagnosing the cloudy equine eye is often met with Calcific band keratopathy ● trepidation in the field setting because of the variety Eosinophilic keratitis ● Nonulcerative keratouveitis of differentials for this condition, many of which ● are clinically difficult to distinguish. Most equine Onchocerciasis ● Squamous cell carcinoma veterinarians feel comfortable with diagnosis and ● Subepithelial keratomycosis treatment of uncomplicated corneal ulceration be- ● Immune-mediated keratitis cause of its high prevalence in equine practice. ● Equine recurrent uveitis However, the cloudy eye with intact epithelium is a ● Glaucoma less common complaint and can prove to be a diag- nostic challenge. Furthermore, accurate diagnosis 2. Materials and Methods is vital. Treatment for one condition is often con- For the initial ophthalmic examination, the same traindicated for another, particularly with regard to basic tools are needed as for any ophthalmic ambu- the use of corticosteroids. The importance of accu- latory procedure. rate diagnosis and treatment is accentuated by the ● fact that maintenance of a clear visual axis is often Fluorescein stain ● Mepivicaine or lidocaine for local nerve blocks a necessity for the career of the equine patient. ● ␣ Equine eyes have the propensity to degenerate rap- Chemical restraint: 2-agonist sedation (xy- lazine, detomidine) idly, leaving very little room for error. The objec- ● Focal light source with cobalt-blue filter tive of this report is to present a stepwise approach ● Dimly lit area to diagnosis of the cloudy equine eye. Correct diag- nosis will allow accurate treatment. Step 1: Is the Eye Painful? The disease processes that will be discussed in- Examination should start with a patient who has clude the following: not yet been sedated and whose eyelids have not NOTES AAEP PROCEEDINGS ր Vol. 59 ր 2013 181 HOW-TO SESSION: OPHTHALMOLOGY Fig. 1. Determining the degree of ocular pain. been blocked, to allow accurate assessment of ocular pain. Hallmark clinical signs of ocular pain include epiphora and blepharospasm. Determining the de- gree of ocular pain is important for formulation of differential diagnoses of corneal opacity (Fig. 1). Fig. 2. Corneal edema. After gross assessment for pain through a visual examination, the function of cranial nerves II, III, V, and VII is assessed by the menace response, dazzle reflex, pupillary light reflexes (direct and indirect), ● Edema: hazy gray-blue, can be focal or dif- and palpebral reflex. Pupil size, shape, and symme- fuse (Fig. 2) try between right and left pupils should be evalu- ● Vessels: originate from the limbus ated. Miosis, mydriasis, and anisocoria may occur ● Perfused or ghost coincident with corneal disease, the most common ● Depth indicates location of inciting lesion examples being when the corneal opacity is associ- ● Superficial–branching ated with anterior uveitis, synechia, or glaucoma. ● Deep–hedge ● Fibrosis: gray, may note associated ghost Step 2: Is There an Ulcer? vessels After assessment of vision and reflexes, the horse ● Inflammatory cell infiltrate: yellow to green can be sedated and perineural anesthesia can be discoloration performed if needed. If corneal culture is war- ● Lipid or mineral infiltrate: shiny white, crys- ranted, that should occur before instilling any topi- talline (cholesterol or calcium) cal solutions into the eye. The eye must be stained with fluorescein, even if it does not appear that a It is vital to be able to recognize these processes corneal ulcer is present. The only way to determine when examining an eye with corneal disease. fluorescein stain uptake accurately is with use of a cobalt-blue filter light. Use of a focal light source is Step 4: Making the Diagnosis key to careful examination of corneal opacities. A systematic approach should be used every time, so (1) Diseases Generally Characterized by a that no area is missed, even if the lesion is immedi- Nonpainful Eye ately apparent. Start at the limbus and examine If initial assessment shows the patient to have nor- circumferentially, moving axially toward a more mal ocular comfort, the differential diagnosis list is central part of the cornea as you proceed. Often significantly shortened. Any disease that has a dimming the focal light source and taking breaks component uveitis is excluded from this category, will improve the tractability of the patient. Be sure because the condition is typically painful (Fig. 3). to examine both eyes. (a) Immune-mediated keratitis (IMK) should be considered as a differential for a nonpainful eye with Step 3: What Color Is the Opacity? corneal vascularization.1 In IMK, vascularization The cornea readily displays pathologies as the result depth generally corresponds to the depth of the le- of its biologically clear appearance. Furthermore, sion. There are often striking corneal changes it has a limited number of characteristic reactions while the eye is quiet and comfortable (Fig. 4). to disease. The ability to visually recognize these The specific pathogenesis of this disease is not reactions allows for accurate differentiation of kera- known, and the clinical presentation can be highly topathies. The following is a list of the equine cor- variable. The unifying characteristics of the dis- nea reaction to disease accompanied by its clinical ease are the ocular comfort of the patient and the appearance: lesion response to immunosuppressive therapy. 182 2013 ր Vol. 59 ր AAEP PROCEEDINGS HOW-TO SESSION: OPHTHALMOLOGY Fig. 3. Differentials for the non-painful, cloudy eye. Ruling out an infectious cause through culture or opacities that resolve with anti-fungal therapy. Cul- empirical antimicrobial therapy is important when ture results of these lesions are variable. There- making this diagnosis because the cornerstone of fore, it is important to rule out an infectious disease therapy for IMK is immunosuppression with such as this, for example, with initial treatment of corticosteroids. empirical antimicrobial therapy before treating for (b) Similar in appearance to IMK but of in- immune-mediated disease. 2 fectious origin is subepithelial keratomycosis. (c) Another differential for a nonpainful corneal Horses with this disease only exhibit mild to no opacity is the most common tumor of the equine blepharospasm. Hallmark corneal changes are cornea—corneal squamous cell carcinoma.3 This multifocal punctate to geographic cellular infiltrate can originate from the cornea, conjunctiva, or lim- bus. Although lesions commonly appear nodular and elevated, some may appear simply as stromal infiltrate (Fig. 5). Notably, all of the forms should cause little to no discomfort. When squamous cell carcinoma is high on the differential diagnosis list, biopsy is needed for diagnosis. This may be in the form of keratectomy under general anesthesia if the lesion is smooth and cannot be grasped for easy removal. (d) End-stage glaucoma can manifest as a com- fortable, cloudy eye. The corneal opacity in this case is usually edema.4 This corneal change is of- ten accompanied by other gross changes such as buphthalmos and striae, and the eye is usually blind. (e) Despite its chronicity, fibrosis may be newly noted by a client or seen on initial examination such Fig. 4. IMK of manifests with striking corneal changes. as during a pre-purchase exam. Corneal scars vary AAEP PROCEEDINGS ր Vol. 59 ր 2013 183 HOW-TO SESSION: OPHTHALMOLOGY characteristic of these diseases. This infiltrate may be located in any area of the cornea and at any depth. Nonspecific signs of ocular pain and severe inflammation are concurrent. The gold standard for diagnosis and differentiation of both diseases is histopathology; however, this requires general an- esthesia. Therefore, often the diagnosis may be made by response to therapy because the intact ep- ithelium usually prevents adequate cytology and culture. (c) A differential for the cloudy, painful eye with diffuse or focal corneal edema is uveitis. Anterior uveitis alone without primary corneal disease may manifest as the result of equine recurrent uveitis8 or ocular trauma. In these cases, the predominant Fig. 5. Some neoplastic lesions appear as stromal infiltrate. corneal change is diffuse corneal edema. Extensive neovascularization or cellular infiltrate should not be present. Clinical signs of note are miosis, often severe, and circumlimbal vascularization. Careful significantly in size and density. The deeper the inspection of the quality, opacity, and coloration of injury, the denser the scar; they should appear the cornea should allow for differentiation. white, consolidated, and smooth, with no ocular dis- (d) Early glaucoma is another differential for comfort (see Fig. 6). painful, diffuse corneal edema, especially that which (2) Diseases Generally Characterized by a Painful does not respond to anti-inflammatory medication. Eye In the early, acute stage, the eye may be painful. Measurement of intraocular pressure is the gold If the eye is painful, a wide variety of conditions are standard for diagnosis of this disease and will be possible