'Mutton Fat' Corneal Keratic Precipitates and Lens Induced Uveitis in a Poodle puppy.

     Lens-induced uveitis is a common complication of cataracts in dogs. Although it was initially associated with hyper mature cataracts, many ophthalmologists opine that all stages of cataracts have some degree of subclinical uveitis present. Two distinct types of LIU are recognized in the dog

1. Phacolytic Lens-induced uveitis - mostly occurs in young dogs with rapidly developing cataracts where small quantities of soluble lens protein leak through an intact capsule. These 'proteins' induce a T-cell / humoral antibody response and produce anti-crystallin antibodies leading to non-granulomatous lymphocytic-plasmacytic uveitis. 

2. Phacoclastic Lens induced uveitis - occurs after rupture of the anterior lens capsule releasing a large quantity of lens protein at once. There may be a history of recent ocular trauma, hyphema, varying degrees of anterior uveitis, and the presence of inflammatory/fibrinous material in the anterior chamber. With chronicity, posterior synechiae, and secondary glaucoma occur leading to complete vision loss. 

        Treatment for both types of LIU is aimed at correcting the primary cause. i.e., the lens. Lensectomy using phacoemulsification is the ideal therapy for lens rupture while Phacoemulsification works well for cataractous lenses.  The prognosis of dogs after phacoemulsification without LIU tends to be better than dogs that have LIU. Simultaneously, uveitis must be looked into but it is recorded that the anterior uveitis persists months after the correction of the primary cause.

            Keratic precipitates are inflammatory cellular deposits on the corneal endothelium. the inflammatory cells gain entry into the aqueous humor after a break in the blood-aqueous barrier secondary anterior uveitis. The corneal endothelium exposes adhesion molecules during inflammation that bind to the leucocytes and fibrin forming the keratic precipitates. Furthermore, the engulfed fat within macrophages also bind to the corneal endothelium forming the so-called 'mutton fat precipitates' owing to its appearance. The presence of these mutton fat precipitates often represents a granulomatous inflammation and are usually present in the lower half or third of the cornea because of the aqueous humor thermal convention currents.

 

Large Keratic 'Mutton fat' precipitates on the ventral half of the corneal endothelium visible as diffuse punctate opacities, and corneal vascularization. L- a reflection of the flashlight used for photography. 

Lens - Cataractous opaque lens at the center of the pupil. H - hemorrhagic foci on the iris secondary to the Lens induced uveitis. L - a reflection of the flashlight used for photography. Also note the episcleritis and conjunctivitis at the limbal margin secondary to LIU and keratitis. 

        The poodle puppy was presented with a complaint of 'abnormal eyes' for a fortnight. The contralateral eye was apparently normal. The IOP of the affected eye was 12 mm H2O while that of the other eye was 15 mm H2O. It was prescribed oral Doxycycline at 10mg/Kg, topical atropine eye drops, and Moxifloxacin eye drops. The owner never returned for a review. However, the prognosis for vision irrespective of medical treatment was guarded owing to the severity and chronicity of the pathology.

References 

        1. Townsend W. M. (2008). Canine and feline uveitis. The Veterinary clinics of North     America. Small animal practice, 38(2), 323–vii. https://doi.org/10.1016/j.cvsm.2007.12.004

       2. Maggs, D., Miller, P., & Ofri, R. (2017). General Pathology of the eye. In Slatter's fundamentals of veterinary ophthalmology (6th ed., pp. 60-78). Saunders.

        3. Gelatt, K. N., Gilger, B. C., & Kern, T. J. (2013). Diseases and Surgery of the Canine Anterior Uvea. In Veterinary ophthalmology: Two volume set (5th ed., pp. 1146-1198). John Wiley & Sons.