Page 348 - Cote clinical veterinary advisor dogs and cats 4th

Cataracts 147

• The use of orthotics has shown promise loss in range of motion (flexion) is to be SUGGESTED READING
(11/14 cases back to full function) in manag- • In racing greyhounds, treatment of radial Kapatkin AS, et al : Carpus, metacarpus, and digits.
expected.
VetBooks.ir be used to support hyperextension injuries carpal or accessory carpal bone fractures with AUTHOR: Louis Huneault, DMV, MSc, DES, DACVS Diseases and Disorders
ing mediolateral instabilities. They can also
In Tobias KM, et al, editors: Veterinary surgery
small animal, St. Louis, 2012, Elsevier, pp 789-798.
lag-screw fixation (preferred) or fragment
if surgery is not possible.
• Intraarticular fractures treated conservatively
rarely heal with osseous bridging, leading to excision can provide a return to competitive EDITOR: Kathleen Linn, DVM, MS, DACVS
performance.
degenerative joint disease.
• Consider CT if a fracture is still suspected Technician Tips
despite normal radiographs. After case evaluation, prepare for modified
• Partial carpal arthrodesis can promote a Robert Jones bandaging with/without splinting
return to most preinjury activities, but some and wound management if applicable.

Cataracts Client Education
Sheet

BASIC INFORMATION ○ Nucleus: nuclear cataracts are always causing excess glucose to be shunted to the
congenital, but not all congenital cataracts sorbitol pathway, which forms polyols and
Definition are nuclear. subsequently osmotically draws water into
Any opacity, regardless of size, of the ocular • Severity the lens, causing opacification (dogs). All
lens or its capsule is called a cataract. A cata- ○ Incipient: <10% of retinal examination dogs with diabetes mellitus develop cataracts:
ract results from a change in the lens protein obstructed 50% by 170 days and 80% by 470 days after
composition or lens fiber arrangement, and ○ Immature: early, 10%-50% of retinal the onset of diabetes mellitus.
it is one of the most common canine ocular examination obstructed; late, 50%-99% • Secondary to intraocular disease: uveitis,
abnormalities. of retinal examination obstructed glaucoma, intraocular neoplasia, retinal
○ Mature: 100% of retinal examination degeneration/detachment, lens luxation
Epidemiology obstructed • Trauma to lens: blunt or penetrating
SPECIES, AGE, SEX ○ Hypermature: liquefaction/resorption with • Age related
• Dogs and cats associated lens-induced uveitis (p. 1023) • Nutritional: in puppies and kittens fed milk
• Age of onset depends on breed and cause. ○ Morgagnian (cortex has liquefied and the replacer. Proposed mechanism is amino acid
• Cataracts affect 16.8% of mixed-breed dogs nucleus falls ventrally in the capsule) deficiency, such as arginine, at crucial stage
ages 7-15+ years. during lens development
HISTORY, CHIEF COMPLAINT • Hypocalcemia
GENETICS, BREED PREDISPOSITION • Vision disturbance • Radiation therapy/injury when primary beam
• In dogs, most cataracts have an inherited • Cloudy white pupil near or on globe
component; the most common mode of • Pain, redness, epiphora may be noted if the • Medications (e.g., long-term oral ketocon-
inheritance is autosomal recessive. cataract results in secondary anterior uveitis. azole; mostly in young, large-breed dogs
• Highest prevalence in dogs: smooth fox • The chief complaint may reflect a systemic given higher doses [6-13.9 mg/kg/day])
terrier, Havanese, Bichon frisé, Boston cause of cataracts (e.g., polyuria/polydipsia, • Toxins (e.g., dinitrophenol, diazoxide)
terrier, poodles (toy, miniature, standard), weight loss with diabetes mellitus). • Electric shock
silky terrier, American cocker spaniel, and Not all cataracts are progressive. Cataracts can
miniature schnauzer PHYSICAL EXAM FINDINGS progress to become hypermature and result in
• Canine cataracts can also occur secondary • Opacity of the lens (unilateral or bilateral) lens-induced uveitis and increased risk of vitreal
to diabetes mellitus, which has a genetic with any or all of the following: degeneration, retinal detachment, and secondary
predisposition in some breeds. ○ Anterior uveitis (p. 1023) glaucoma.
• Presumed congenital feline cataracts: Persian, ○ Glaucoma (p. 387)
Birman, Himalayan, and domestic shorthair ○ Lens subluxation/luxation (p. 581) DIAGNOSIS
○ Retinal degeneration, retinal detachment
RISK FACTORS (pp. 883 and 885) Diagnostic Overview
See Etiology and Pathophysiology below. ○ Systemic abnormalities may be present The diagnosis of cataract is suspected based on
when cataracts are caused by a generalized observation of a cloudy pupil in an animal that
Clinical Presentation disorder (e.g., weight loss with diabetes may be visually compromised. It is confirmed
DISEASE FORMS/SUBTYPES mellitus). by the finding of a lens opacity after complete
Cataracts are classified by age at onset, location, dilation of the pupil using a short-acting
severity, and cause. Etiology and Pathophysiology mydriatic (1% tropicamide).
• Age at onset Regardless of the cause, all cataracts occur
○ Congenital (present at birth) through a change in the lens protein composi- Differential Diagnosis
○ Juvenile (few months to 6 years) tion or lens fiber arrangement. • Nuclear/lenticular sclerosis: normal aging
○ Senile (>6 years) • Inherited change; seen in all animals ≥ 7 years old;
• Location • Diabetes mellitus: increased blood glucose does not cause vision loss; center of lens
○ Capsule (anterior/posterior) results in diffusion of glucose into the lens, becomes opalescent to hazy, but tapetal
○ Cortex (anterior/posterior or equatorial) overwhelming standard lens metabolism, reflection (usually yellow greenish) is still

www.ExpertConsult.com