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Argon laser photocoagulation is a standard and effective clinical technique for a variety of disease conditions. However there is evidence that coagulation produces more widespread alterations in the retina than the local scarring at the injury site. For example, in diabetic retinopathy multiple photocoagulations in the retinal periphery can control blood vessel growth in the central retina. Therefore we have studied the changes in retinal glial cells following photocoagulation using immunocytochemical techniques with an emphasis on the spread of cellular reactions by using whole, flatmounted retinal preparations. Muller glial cells do not normally express the cytoskeletal protein GFAP (glial fibrillary acidic protein) but do so after a variety of injuries. We found that there is a very widespread expression of GFAP by Miller cells even after very focal coagulations and that this persists for 1-1. 5 months after coagulation. The microglial cells are primed to react to injury and can release very powerful effector molecules and we therefore also examined the microglial reaction to see whether it correlated with the Muller cell reaction. However, we found that the microglial response, in terms of anatomical changes, was very focally confined to regions of direct cellular injury. We also examined MI-IC II expression to see whether microglia expressed this activity related protein without anatomical changes but we found no evidence of wide spread changes. In summary we find that inflammatory reactions are very localised after coagulation but the macroglial changes are more widespread and therefore the distant effects ofphotocoagulation may be more related to macroglial reactions.

An 11‐year‐old, male, neutered American bulldog presented with a 3‐month history of intermittent vomiting and concurrent hyporexia. Abdominal ultrasonography identified concentric thickening of the tunica muscularis at the ileo–caeco–colic junction, which was confirmed with computed tomography. An exploratory coeliotomy was undertaken, where a solitary caecal mass was identified. An end‐to‐side enterocolostomy was performed and resected tissue submitted for histopathology. Histopathology was consistent with diffuse smooth muscle hyperplasia of the tunica muscularis. Two months later, the patient re‐presented with profuse watery diarrhoea. Low vitamin B12 was identified on biochemistry, and supplementation was commenced. In the following 3 months, no further clinical signs were reported.