Clinical features of normal buffalo eye (Bubalus bubalis): reference ranges

Introduction - The water buffalo (Bubalus bubalis) is a ruminant species important in the economy of several countries, including Brazil, China, India, Vietnam and some regions of central and southern Italy. Considering the health implications and the economic potential of water buffaloes, the issue of investigating the clinical characteristics of buffalo eye is of considerable relevance. Aim - The aim of this study is to report the morphological and functional features of buffalo eye, in order to know the clinical aspect of the ocular structures and the normal range of ocular parameters, such as Schirmer tear test and intraocular pressure. The electrophoresis of tear protein also was investigated. Materials and methods - The study was conducted on 40 subjects: 30 females aged between 6 and 11 years and 10 calves, 5 females and 5 males, approximately 2 months of age. At the examination all the animals in good health showed no clinical symptoms referable to eye disease or a specific organ injury secondary to systemic diseases. The animals were divided into 2 groups: the first consisting of 20 adult females and 5 calves was subjected to ophthalmological examination; on the second consisting of 10 adult females and 5 calve was performed electrophoresis of the tear fluid. Results - The buffaloes globes are positioned laterally within their skull; the cornea and the pupil are very large, with a mean distance between the medial and lateral canthus of 5.6 cm in adult buffaloes and 4.3 cm in calves. The superior pupil edge is equipped with some uveal structures called "corpora nigra". Schirmer tear test provided these mean values: 22.37 +/- 5.44 (SD) mm/min; the IOP (intraocular pressure) evaluation provided these mean values: 20.12 +/- 3.44 mm/Hg (SD). Discussion - The buffalo cornea is broader than it is high, which enhances their lateral view of the world. To further increase their panoramic view of the world, buffalo's globes are positioned laterally and their pupil is horizontally elongated. Corpora nigra located on the upper pupillary margin, likely have the function of "barrier" of solar radiation. The statistical evaluation of STT and IOP values showed no significant differences between the right eye and left eye, or between subjects of different ages (p > 0.05). Statistical analysis of data on tear protein electrophoresis was shown a highly significant difference between subjects of different ages on protein migrated rapidly (PMR), which are even absent in young subjects (p <= 0.01). Conclusions - The results of this study are presented as reference values for the ophthalmic parameters in the buffalo species; to determine their variability within a given species is very important to carry out a specialist examination.