Health Bulletin No 22, May 2014.
Previously in Bulletin No13, the number of cases of posterior polar sub-capsular cataract (PPSC) diagnosed from 2009 to 2011 was reported. Initially only six cases were reported by the BVA at that time but this has now been amended to seven. Over 2012-2013 a further two cases have been reported so these will be combined with previous figures.
Thus from 2009 to 2013, nine cases of PPSC have been reported from a total of 1262 adult eye tests giving an incidence of 0.7%; we do not know exactly how many of the total dogs are retests, nor if any cases were detected in dogs being retested, but as retests have been estimated to be perhaps about 10% of the total, we can be confident that the incidence among dogs being tested is less that 1.0%. Data from Finland indicates that six cases were found among 651 dogs tested between the same years, 2009-2013, giving a similar incidence of 0.9%.
Of the nine UK cases, six were one year olds when diagnosed, and the remaining three were 3yo, 5yo and 8yo respectively. The one year old dogs would almost certainly be diagnosed at their first adult eye examination. The same may be true for the dog aged three if testing was delayed until being bred for the first time, and even the five year old. As for the eight year old dog, one would have expected it to have had its eyes tested on a previous occasion especially if its owner was a show breeder, although it is possible that the dog was undergoing a full eye examination for another reason and finding PPSC was co-incidental.
Initial thoughts were that PPSC tended to develop mainly in older dogs but this is clearly refuted by finding two thirds of these cases in dogs aged less than two years. PPSC has been found in numerous breeds and may be there from six months of age upwards although it is considered it may develop at any age. It was always considered that dogs with PPSC suffer little, if any, visual impairment but there have been a few reports of it progressing to affect sight although we do not know in what breeds nor how often this has actually occurred.
Labrador Retrievers are one of the main breeds associated with PPSC. On one relevant site, no information is given on its incidence although considered to be the most common type of cataract in that breed and may usually be diagnosed from about 12m old. It would also appear that PPSC may progress in less than 5% of affected Labradors. Extrapolating data from one breed to another requires the greatest caution, but if the risk of progression was the same it would mean that the chance of a Stafford having sight problems with PPSC is approximately only 1:2000 We are aware, anecdotally, of one case being found in a 5yo SBT which had had a couple of previous clear eye tests, but there would appear to be no reports of any PPSC affected Stafford developing visual impairment as a consequence.
These figures suggest PPSC is not common in SBTs although determining its incidence accurately would require the examination of a large number of older dogs perhaps aged ten or more to see how many have actually developed it and if it had caused any sight problems. Clearly they have implications for future eye testing policies but this is a matter to be discussed by the Clubs.