If the lens of the eye loses its transparency, for whatever reason, one can speak of a cataract.  Please understand that this is quite distinct from the normal increase in opacity that occurs in older animals.

Scientists tend to classify everything.  So too they have differentiated different types of cataracts according to (i) age of the animal at the onset of the condition (newborn, juvenile, senile), (ii) location, (iii) cause, (iv) degree of opaqueness (incipient, immature, mature, hypermature, and (v) shape.  Well, all of this is quite fine, but also quite meaningless to the practical owner of a pet stricken with cataracts.

Similarly, the cause of the cataract is only of marginal importance to the pet owner (dogs seem to have cataracts more than any other species, with the possible exception of the horse).  The process starts with the coagulation of plasma in the cells of the lens, followed by a further degeneration and shrinking (accompanied by a hardening) of the tissue, all leading to the loss of transparency.

What can precipitate this development of events?  Well, any condition which interferes with the nutrition of the lens must be considered the causative agent.  For example

(i) an inflammation of the iris, (ii) pressure created by swellings (= tumours) of any origin, (iii) a hard blow to the eyeball, (iv) haemorrhaging in the eye; (v) glaucoma (see last week’s Pet Corner).

All could represent possible triggering causes.

Other more organic problems, like diabetes, are implicated in cataract formation.  Some poisons too (eg the eating of naphthalene balls) seem to cause cataract development.  And of course, general malnutrition and senility could result in cataract formation.

How do we recognise a cataract?
Well, sometimes it is very obvious, in that one can immediately discern the milky-grey/bluish-white opacity, visible through the pupil.  On other occasions, the cataract is represented just by a spot on the lens that is not so easily visible.  Later, instead of just the one small spot, there are several white flecks on the lens. If there is a difficulty seeing the lens, your vet can administer drops which would cause the pupils to enlarge, so that you (and the vet) can have a clear look at the lens.

I had said, in the third paragraph above, the cause of the cataract is relatively unimportant to the owner.  Actually, I was referring mainly to the biochemistry gone awry.  The importance of knowing the origin of the cataract becomes clear, if the underlying cause is organic in nature.  For example, if diabetes is the original problem, then it is important that we recognise that and treat this initial problem.

Similarly, if the cataract is genetic in origin (breed anchored – eg in Poodles, Cocker Spaniels, etc), then we would not want such an animal giving birth to offspring which can perpetuate the bad genes.

The treatment will mirror the precipitating cause.  Malnutrition and poisoning, for example, may be corrected.  Cataracts resulting from diabetes and senility will have to be treated by a special management regime.  In cats (and horses), it is usually an inflammatory process (caused by an infection) that results in the cataracts, so we can treat this infectious condition.  Juvenile cataracts may go away on their own without too much veterinary intervention, and congenital cataracts may get better as the animal grows and the lens become larger.

Finally, one can remove the lens surgically.  The owner should discuss this option in depth with his/her veterinarian.  Really, only the inevitability of total blindness should bring a consideration of the surgical option to the fore.

Since we are talking about the lens, perhaps I should mention that there is a condition whereby there is a lens displacement. This condition is seem in all species, but is common as a primary inherited defect in several Terrier breeds. What happens is that the lens ‘falls’ into the front or rear chamber of the eyeball.

The causes of the lens displacement can, inter alia, be produced by (i) a blow to the eyeball/head; (ii) stretching/weakening
of the apparatus on which the lens hangs; (iii) degenerative conditions within the eyeball (eg chronic cataracts).

The treatment (which can only be surgery) will be based on whether the dog is being affected severely. Since this is hardly ever the case, I advise that you live with the peculiar look in the animal’s eyes – what with the lens visible in the front chamber of the eyeball. Don’t let it worry you; it surely is not disturbing the dog/cat.

Have a pleasant week.

Please implement disease preventative measures (vaccinations, routine dewormings, monthly anti-heartworm medication, etc) and adopt-a-pet from the GSPCA’s Animal Clinic and Shelter at Robb Street and Orange Walk, if you have the wherewithal to care well for the animals.  Do not stray your unwanted pets, take them to the GSPCA’s Clinic and Shelter instead.  If you see anyone being cruel to an animal, or if you need any technical information, please get in touch with the Clinic and Shelter by calling 226-4237.

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