canis - Articles
Lens: congenital primary cataract
Introduction
- A cataract is an opacification of the lens.
- May be primary (inherited) or secondary due to disease (uveitis, diabetes, PRA).
- Developmentally staged as incipient, immature (tapetal reflex present), mature (no tapetal reflex/blindness) and hypermature (wrinkled lens capsule).
- Either congenital, eg Miniature Schnauzer, Boston Terrier, Welsh Springer Spaniel, at early age, eg Afghan Hound, German Shepherd dog or at later stage, eg Standard Poodle.
- Usually inherited (autosomal recessive).
- Inherited as incomplete dominant in Labrador Retriever, Golden Retriever (posterior subcapsular opacity).
- Good prognosis if phacoemulsification performed and if no other ocular structures involved.
- Early developing cataract: remove at an early stage either by irrigation, aspiration, extracapsular extraction or phacoemulsification → prevents lens-induced uveitis.
Presenting signs
- Blindness.
- Ocular pain from associated uveitis.
- Lacrimation.
- Corneal edema.
- Cloudy eye.
Age predisposition
- Older dog can develop nuclear sclerosis , which can resemble a cataract, but sight is normal.
- Cataracts can be congenital, eg Miniature Schnauzer, develop at young age, eg American Cocker Spaniel or occur in old dogs, eg Poodles.
Breed/Species predisposition
- Miniature Poodle: miniature and Toy Poodle Poodle: Toy.
- American Cocker Spanial American Cocker Spaniel.
- Labrador Retriever Retriever: Labrador.
- Golden Retriever Retriever: Golden.
- Boston Terrier Boston Terrier.
- Miniature Schnauzer Schnauzer: miniature.
- Husky Siberian Husky.
Cost considerations
- Cataract surgery is expensive.
Pathogenesis
Etiology
- Genetic defects.
- Secondary to uveitis, involving changes such as:
- Posterior synechiae
. - Altered aqueous humor in uveitis.
- Posterior synechiae
- Radiation.
- Diabetes mellitus Diabetes mellitus.
- Hypocalcemia Hypocalcemia.
- Senile cataracts.
- Progressive Retinal Atrophy (PRA) / Generalized Progressive Retinal Atrophy (GPRA) Retina: generalized progressive retinal atrophy.
- Nutritional (milk replacers).
Predisposing factors
- Breeds at risk.
- Old age.
Pathophysiology
- Lens opacification is termed a cataract.
- Disruption of lens proteins causes lens opacification.
Timecourse
- Incipient cataracts can progress to immature, mature and hypermature stages, although these stages are not mutually exclusive .
- Nuclear cataracts may become relatively smaller with time as the lens cortex grows in size
. - Cortical cataracts almost always progress.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Krishnan H, Hetzel S, McLellan G J & Bentley E (2019) Comparison of outcomes in cataractous eyes of dogs undergoing phacoemulsification versus eyes not undergoing surgery. Vet Ophthalmol 23 (2), 286–291 PubMed.
- Fischer M C and Meyer-Lindenberg A (2018) Progression and complications of canine cataracts for different stages of development and aetiologies. J Small Anim Pract 59, 616-624 PubMed.
- Williams D L, Boydell I P & Long R D (1996) Current concepts in the management of canine cataract: a survey of techniques used by surgeons in Britain, Europe and the USA and a review of recent literature. Vet Rec 138 (15), 347-53 PubMed.
Other sources of information
- Gelatt K N and Plummer C E (2017) Color Atlas of Veterinary Ophthalmology Appendix C: Inherited Cataracts in the Dog.
- Gelatt K N (1998) Veterinary Ophthalmology. 3rd edn. Williams & Wilkins.