CANADIAN MANCHESTER TERRIER CLUB HEALTH SURVEY: CATARACTS
General Information
Data was collected October, 2003 until December 31, 2003. The main method of collection was via an electronic survey posted on the CMTC website, however, paper copies of the survey were also sent out when requested.
Incidence of CataractsData was reported for a total of 284 Manchester Terriers. Of the responses, 169 individuals were identified as Toy Manchester Terriers (79 males, 90 females) and 115 as standard Manchester Terriers (55 males, 60 females). Of these, seventeen individuals were reported as suffering from cataracts. This represents only a slight increase from the larger, more general Health Survey conducted in 2002, in which 14 Manchester Terriers were reported to suffer from cataracts. Cataracts were reported in 15 Toy Manchester Terriers and 3 standard Manchester Terriers. Because of the low number of standard Manchester Terriers suffering from cataracts, the majority of the following analyses will involve all Manchesters, rather than analyzing by variety.
Because the data from the current survey is small in number, one must be cautious in drawing strong conclusions from it. However, it is nonetheless interesting to note patterns of cataracts between the sexes. As the table below demonstrates, cataracts appear to be more common in females than in males. It should be noted that the sex of 1 Toy Manchester Terrier was no identified.
Table One. Manchester Terriers with Cataracts
Number of Males with Cataracts
Number of Females with Cataracts
Toy Manchester Terriers
3
(3.8% of male TMTs)
11
(12.2% of female TMTs)
Standard Manchester Terriers
1
(1.8 % of male SMTs)
2
(3.3 % of female SMTs)
Age of Onset
Overall, Manchester Terriers seem to develop cataracts later in life. The average age of onset in this survey was 8.9 years (SD= 1.87). The age of onset ranged from 4 to 11 years. Only 2 animals were reported to have developed cataracts under 7 years of age. This is good news, as many types of strongly heritable cataracts, are associated with an early onset.
Unilateral and Bilateral Cataracts
Most respondents (78%) indicated that their Manchester Terrier suffered from bilateral cataracts. Interestingly, all 3 standard Manchester Terriers with cataracts were reported as having bilateral cataracts.
The Diagnosis
The majority of the “diagnoses” were made by the individual. Eight individuals (44% of respondents) indicated that the diagnosis was made by “breeder/self (condition suspected but not confirmed)”. Thirty-three percent indicated that the diagnosis was made by a board-certified veterinary ophthalmologist, while the remaining 22% of diagnoses were made by the individual’s regular veterinarian. Interesting, several individuals who self-diagnosed some of their Manchester Terriers for cataracts also brought other individual MTs to Board-certified veterinary ophthalmologists for diagnosis.
Most respondents (39%) reported that their MTs had immature cataracts, in which the retina can still be seen through an ophthalmoscope and the dog may or may not be blind. A smaller number (17%, 3 cases) reported incipient cataracts (small cataracts which do not usually affect vision), and 17% reported mature cataract, where the entire lens is cloudy, the retina cannot be seen, and the dog is blind.
Precipitating Conditions
Interestingly, most respondents did not report any precipitating conditions to cataract formation. The medical literature suggests that some conditions, such as eye infections, old age, diabetes, or eye injuries, can lead to the development of cataracts. In the current survey, 83% of responses indicated no precipitating conditions. For 3 individual MTs (17% of those suffering from cataracts) a previous eye injury was reported.
Progression
Eighty-nine percent of the cases reported involved a slow progression of the development of the cataract(s). Only 2 cases reported rapid progression. This is a notable, as rapid progression is often associated with more serious forms of the disorder, and also with forms that are suspected of having a stronger hertitable basis.
Treatment
Most owners (89%) reported not treating their Manchester Terriers cataracts. Only 2 individuals report electing to have surgerical treatments. Of these two cases, one was a 4-year old MT with bilateral cataracts and the other an 8.5-year old MT with unilateral cataracts. Given that most Manchester Terriers were reported to have incipient or immature cataracts, it seems likely that most owners deemed that the risks associated with surgery were not warranted for the severity of the cataracts present.
First Signs of the Disease
The strongest first indicator of the disorder was the owner detecting changes (i.e. cloudiness) in the eye, with 88.9% of respondents selecting this as the first symptom. Only 1 individual indicated behavioural symptoms, such as clumsiness, bumping into furnature & walls, fear of being left alone, failure to retrieve favourite toys, etc. One respondent failed to indicate the first signs of the disorder. No one indicated the disorder was first detected during a regular visit to the veterinarian.
Conclusions
The data from the current survey are generally in agreement with the findings from the 2002 Health Survey regarding the number of Manchester Terriers afflicted with cataracts. Although the current survey indicates a slight increase in the number of Manchester Terriers suffering from cataracts, it is possible that some individuals who had self-diagnosed their Manchester Terriers were reluctant to report these cases in the previous survey. It is also possible that the slight increase simply reflects one or two owners who failed to respond to the previous survey.
Overall, the findings from this survey are encouraging. Generally, the disorder appears to have a late onset and be of a lesser severity. These findings are encouraging as they suggest that many of the cases are likely the result of normal aging processes rather than inherited forms of the disorder.