Characterisation of corneal impression cytology in dogs and its application in the diagnosis of keratoconjunctivitis sicca

Abstract

ObjectiveDetermine morphological and morphometric parameters of corneal epithelium in dogs, and determine the cellular alterations that occur in canine keratoconjunctivitis sicca (KCS) using impression cytology.Study animals60 dogs divided into two groups: dogs with Schirmer tear test (STT) at least 15 mm/minute and absence of ocular disease, and dogs with STT less than 15 mm/minute and clinical signs of KCS.ProceduresImpression cytology was used to collect corneal samples. The percentage of eyes with cell changes, the number of such cells and the percentage of cells with structural alterations in each group were determined. The possible correlation between corneal epithelium alterations and decreased tear production was evaluated.ResultsA significant positive correlation existed between STT and the area of the cytoplasm and nucleus of corneal cells. A significant negative correlation was found between STT ​​and the nucleus/cytoplasm ratio, and the presence of cellular changes. A significant difference existed between the numbers of pyknotic nuclei, being higher among animals with all stages of KCS.ConclusionCorneal impression cytology can be used to assess the corneal epithelium in healthy eyes and eyes with KCS, demonstrating its usefulness as a diagnostic tool especially in mild and early cases.

Difference in cytological findings of healthy and conjunctivitis/keratoconjunctivitis affected canine eyes between variably experienced evaluators

“…The agreement between the two evaluators in our study on these sample parameters was better in the affected eyes group than in the healthy eyes group. This difference could be explained by the presence of healthy cells in larger clusters or sheets [10] compared to the high proportion of individual inflammatory cells in the affected eyes. Cytology textbooks and materials available online contain few pictures of normal cells and mostly focus on the pathologies that can be observed.…”

Improving the diagnosis of canine keratoconjunctivitis sicca

“…Morphological changes were found to be more frequent in dogs with lower STT values, and it was observed that the number of altered cells increased in proportion to a decrease in STT value. A significant difference was also observed in the number of pyknotic nuclei, with the number being higher in dogs with all stages of KCS than in healthy dogs 13 …”

“…A signiicant diference was also observed in the number of pyknotic nuclei, with the number being higher in dogs with all stages of KCS than in healthy dogs. 13 Lejarza-Illaro and colleagues' results demonstrate that corneal impression cytology may be a useful additional diagnostic procedure that can be used to conirm a diagnosis of KCS. It may also have the potential to diferentiate between mild, moderate and severe cases of KCS.…”

“…11,12 In a paper summarised on p 678 of this issue of Vet Record, Lejarza-Illaro and colleagues used impression cytology to examine the characteristics of corneal epithelial cells in healthy canine eyes as well as those with various severities of KCS. 13 In this study, the morphological and morphometric parameters of corneal epithelial cells in healthy dogs with STT values greater than 15 mm/minute and dogs with STT values between 0 and 14 mm/minute and one clinical sign of KCS were examined. The dogs with STT values between 0 and 14 mm/minute were subdivided into three groups: less than 5 mm/minute, between 6 and 10 mm/minute and between 11 and 14 mm/minute.…”

“…A small number of previous studies have examined the cellular changes associated with KCS, but most of these have focused on the conjunctiva 11, 12 . In a paper summarised on p 678 of this issue of Vet Record , Lejarza‐Illaro and colleagues used impression cytology to examine the characteristics of corneal epithelial cells in healthy canine eyes as well as those with various severities of KCS 13 …”