Tear Film Osmolarity in Horses With Bacterial Conjunctivitis

Conjunctivitis is an inflammation of the conjunctiva caused by infectious or non-infectious factors. Infectious conjunctivitis comes in two forms: viral and bacterial. Bacterial conjunctivitis is commonly caused by organisms such as Staphylococcus and Streptococcus, with the severity of the disease influenced by the specific bacterial species involved. Because both viral and bacterial conjunctivitis are highly contagious, preventive measures are essential to reduce transmission-especially to the unaffected eye.

To evaluate the tear film osmolality in horses with bacterial conjunctivitis.

A total of 40 healthy horses and those with conjunctivitis were included in the study. Tear samples were collected from both eyes with microcapillary tubes three times at 5-min intervals. The tear samples for each horse were pooled, and the osmolality and electrolyte concentrations were measured. The mean (SD) was calculated for each variable to establish preliminary guidelines for tear film osmolality and electrolyte composition in healthy horses.

The mean (SD) tear film osmolality was 283.51 (9.33) mmol/kg, and the mean (SD) sodium, potassium, magnesium and calcium concentrations were 134.75 (10), 16.3 (5.77), 3.48 (1.97) and 1.06 (0.42) mmol/L, respectively. The sodium concentration in the tear film was similar to that in serum, whereas the potassium concentration in the tear film was approximately 4.75 times that of serum.

Measuring tear-film osmolality offers a non-invasive, easy and practical approach to gaining valuable insights into baseline conditions and potential changes in ocular diseases. However, its true clinical utility requires integration with other ocular parameters and further controlled studies in horses suffering from conjunctivitis. The development of such tools could lead to more accurate diagnoses and more comprehensive treatment strategies.