高齢期の眼科疾患：白内障について
Eye Disease in Old Age: Cataracts
山下真 ファーブル動物病院 眼科 獣医師
Makoto YAMASHITA Veterinarian at Fabre Animal Hospital, Ophthalmology

T o d a y, w i t h p e t s l i v i n g l o n g e r,

cataracts tend to appear at a young age. In general,

incidences of eye problems in older

juvenile cataracts progress very rapidly and they aredogs are increasing. Cataracts are one

often associated with the eye infection known as uveitis,of the most common of thesewhich can lead to a number of complications including

problems. Pet owners often notice aglaucoma, retinal detachment, etc. On the other hand,murkiness in the pupils of their dogʼs

although the progress of the disease is generally slow ineyes, which is often accompanied byolder dogs (over 6 years of age), sometimes cataracts

a change in the animalʼs behavior at home or when out

progress rapidly in older animals too. In many cases,

walking. Unlike diseases that exhibit rapid visualcataracts in elderly dogs have been observed together

changes such as glaucoma or retinal detachment, in thewith non-hereditary systemic diseases such as diabetes.

case of cataracts, the progression of symptoms isAnd apart from diabetes, endocrine disease, liver orgenerally quite slow. Accordingly, abnormalities in thekidney disease and infectious diseases can also lead todogʼs behavior also tend to appear slowly. In this talk, Iʼ

cataracts. Moreover, cataracts are often observed tod like to focus on and explain about cataracts in dogs.

occur in the wake of other eye diseases such as retinaldegeneration (a disease in which the retina becomes[Slide 1] “Cataracts” is a collective term for the clouding

dysfunctional due to atrophy), etc. Accordingly, whenof the eyeʼs crystalline lens due to any of a number ofcataracts are found in older dogs, it is necessary to carrycauses (Fig. 1). The crystalline lens performs the sameout a general examination of the animal in addition tofunction as the lens in a camera. If the lens is not clear,an eye examination.

light ceases to pass through efficiently. This causes adiﬀused reﬂection inside the eye, which is perceived as[Slide 2] Cataracts in animals can be divided into twoa dazzling light and prevents the eyeʼs distancetypes̶“cataracts that require treatment” and “cataracts

accommodation from functioning correctly. There is athat do not require treatment”. The latter type inwide range of variation among cataract symptoms, andparticular is referred to medically as “nuclear sclerosis”,

the degree of visual difficulty experienced by anwhich means clouding of the ocular lens due to age-

individual animal will vary depending on its age andrelated changes. In nuclear sclerosis, the entire lenstemperament as well as on environmental factors. Inbecomes hazy in time, but unlike in the case of genuine

terms of general behavior, the animal may become

cataracts, this does not usually aﬀect the dogʼs vision, so

more cautious and it may ﬁnd it impossible to walk up

it is rarely treated as an eye disease.

or down stairs. In many cases there are differences
between daytime and nighttime behavior.

When pet owners notice that their dog has cataracts,
they are recommended to visit a family veterinarian as

In the case of cataracts, differentiation is madesoon as they can. It is possible to perform a sufficientaccording to the age of onset, the site of occurrence,

examination at an ordinary veterinary hospital, but if

the rate of progress and the diagnosis provided

that hospital doesnʼt have special equipment for(example: juvenile immature cortex cataracts, etc.) (Fig.

conducting ophthalmic examinations, the pet owner1). In dogs, geriatric cataracts caused in much the same

will need to be introduced to a specialized hospital.

way as in humans are observed, while the mostcommonly observed cases of genetically linked

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高齢犬のケアThere is no “medical therapy” that can restore the(Slide 5). After surgery, the dog must continue to receive

transparency of a lens once it has become cloudy. Ateye-drops for two or three months, and as soon as thepresent, the only way to improve vision compromised

inﬂammation clears up and the eye pressure becomesby such clouding is by means of surgery. In the case ofstable, the animal can go out for walks and play activelyanimals, as I mentioned earlier, there are juvenile

in the same way as before.

cataracts that have a genetic component and adultcataracts that are the result of what I call “rust”, which

Finally, the causes of human and canine cataracts diﬀer.

causes progressive deterioration in the course of

In dogs, the disease progresses swiftly, so when you

systemic illness and aging. This “rust” is the result of thenotice the presence of clouding in your petʼs eye, it isaction of active oxygen, also known as free radical

important to consult your family vet. In addition, it isaction, which promotes eye damage, particularly to theimportant to pay attention to an elderly dog to see if itlens and retina. A variety of supplements have been

is exhibiting any other changes apart from eye

developed and are on sale as animal-use drugs for use

symptoms, because in many cases cataracts in older

against this “rust”. Also, the “rust” is considered to bedogs are related to systemic disease. (For example, thecontrollable to a certain extent using eye-drops.

dog may exhibit such symptoms as constant hunger,

However, it is important to administer these things ondrinking abnormally large amounts of water, increased

the understanding that they will not cure existing

urination, extensive hair loss, or significant weightcataracts but will merely slow the progress of thevariation.)

disease. [Slide 3]
There are no eye-drops or medicinal drinks that can heal
In considering cataract surgery, ﬁrst of all it is necessary

a clouded iris cleanly. When cataracts are advanced andto examine whether improved vision can be achieved

visual disability is observed, it is vital for the dog toby means of surgery or not. For instance, in the casereceive treatment quickly. As a dog owner, if you sensethat the animal already exhibits retinal detachment or athat there is something wrong with your pet, pleasedisease such as retinal degeneration, unfortunately,

consult a veterinarian as soon as possible. If cataract

surgery is not a valid option. Unlike with humansurgery cannot be performed in that particular hospital,patients, intraocular surgery cannot be performed on

obtain an introduction to a diﬀerent veterinary hospitalanimals under local anesthetic. Instead, generalthat can perform such surgery. Since the success rate foranesthetic is required, so it is also necessary to checkcataract surgery performed on dogs is now very high, I

that the animal will be able to tolerate general

would recommend that you consult a veterinarian

anesthetic by conducting a systematic examination.

positively.

The actual surgery is performed in the same way as on
human patients. Nowadays, cataract surgery can beperformed by cutting into the upper side of the eye,making an incision a little over 3mm long at theboundary between the white sclera and the iris. The
method employed is to break up and suck out thecataract using an ultrasonic instrument. After the cloudy
matter is removed, an artificial lens (IOL) (Slide 4)
especially for dog use is inserted into the crystalline
lens, then the incision is sewn up and the operation
completed. In recent years, the procedure for inserting
an artificial lens has become routine and the animalʼsvision after surgery is usually dramatically improved

Workshop Ⅵ Caring for Older Dogs19䇼Slide 㪈䇽䇼Slide 㪌䇽䇼Slide 㪉䇽䇼Slide 㪍䇽䇼Slide 㪊䇽䇼Slide 㪋䇽20

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高齢犬のケア