This is anterior lens luxation, seen most commonly in cats secondary to chronic anterior uveitis.
With anterior lens luxation look for increased intraocular pressure due to blockage of the iridocorneal drainage angle, corneal edema, and ocular pain characterized by blepharospasm and tearing. The lens displacement may also cause an aphakic crescent as seen in this case.
Nuclear sclerosis is a normal aging change of the lens which causes it to appear cloudy, but does not impair vision.
A cataract is an opaque (cloudy, milky) lens, which affects vision. With cataracts look for absence of a tapetal reflection due to light failing to pass through the opaque lens. A tapetal reflection is present with nuclear sclerosis.
Think of orbital cellulitis in large and hunting dog breeds with acute pain on opening the mouth, eyelid swelling, protrusion of the globe, unilateral prolapse of the nictitating membrane, and conjunctivitis.
Image courtesy of Dr. Kim Stanz, copyright 2014, all rights reserved.
