Lens

Chapter 8 Lens

INTRODUCTION

Most pathology that affects the lens, aside from rare congenital defects, is described as a cataract. A cataract is an opacity in the lens that can vary from a small defect visible only under magnification to an opacity that affects the entire lens and causes blindness. Most cataracts in dogs of any age are hereditary. Diabetic cataracts are also fairly common. Most cataracts in cats are secondary to uveitis.

Descriptions of cataracts include the location of the cataract, the causes of the cataract, and the stage of cataract development. Early, small opacities that do not interfere with vision and may not progress are referred to as incipient. Cataracts that are immature involve more of the lens and, depending on their size and location, may affect vision. When the entire lens is involved and no tapetal reflex is seen through the lens, the cataract is called mature. Immature and mature cataracts can liquefy, and lens proteins can leak out of the lens capsule, leading to shrinkage of the lens. At this stage the cataract is called hypermature.

Figure 8-2 Close-up of Figure 8-1 that shows intact zonules nasally in a Labrador retriever.

Figure 8-1 Microphakia and cataract in a Labrador retriever. Zonules are seen nasally.

Figure 8-3 Lens coloboma and microphakia. A lens coloboma is a congenitally missing section of lens and often zonules. Here the coloboma is visible as a malformed lens equator in the superior sector.

Figure 8-4 Microphakia in an Australian shepherd. Stretched ciliary processes can be seen.

Figure 8-5 Nuclear sclerosis. The nucleus of the lens becomes sclerotic with age and is visible as a circular area of “frosted glass” inside the “clear glass” of the lens equator. No visual impairment occurs in animals.

Figure 8-6 Nuclear sclerosis.

Figure 8-7 Nuclear sclerosis.

Figure 8-8 Nuclear sclerosis and asteroid hyalosis. Asteroid hyalosis produces “stars” in the vitreous—calcium-lipid complexes that do not interfere with vision.

Figure 8-9 Incipient posterior cortical cataract in a cat.

Figure 8-10 Nuclear sclerosis with focal anterior cortical cataracts.

Figure 8-11 Peripheral vacuolar cataracts.

Figure 8-12 Posterior Y-suture cataract in a golden retriever.

Figure 8-13 Posterior polar Y-suture cataract in a retriever.

Figure 8-14 A-B Incipient anterior and posterior cortical cataracts in a standard poodle.A, The anterior cataracts in focus. B, Feathering of the posterior Y sutures in focus.

Figure 8-15 Incipient cataracts (vacuoles) positioned equatorially in a dog with hypertensive retinopathy.

Figure 8-16 Diffuse posterior cataracts with peripheral equatorial vacuoles in a dog with diabetes mellitus.

Figure 8-17 Incipient posterior polar, Y-suture cataract in a rottweiler.

Figure 8-18 Nuclear cataract caused by a milk supplement that was given when this dog was a puppy.

Figure 8-19 Incipient cataract in the lens periphery associated with progressive retinal atrophy (PRA) in a dog.

Figure 8-20 Incipient cortical cataract associated with PRA in a dog.

Figure 8-21 Posterior axial cortical cataract in a Siberian husky.

Figure 8-22 Nuclear and posterior subcapsular cataract in a 7-year-old Siberian husky.

Figure 8-23 Immature cataract.

Figure 8-24 Immature cataract in a Siberian husky.

Figure 8-25 Immature cataract in a miniature poodle.

Figure 8-26 Immature cataract in a 2-year-old Boston terrier.

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Tags: Color Atlas of Canine and Feline Ophthalmology

Jul 31, 2016 | Posted by admin in INTERNAL MEDICINE | Comments Off

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