Factors affecting intraocular pressure in lions

The aim of this study was to conduct a detailed analysis of the relationship between age and intraocular pressure (IOP) in lions. Tonometry was conducted in 33 lions aged 5 days to 80 months. Age was significantly associated with IOP (P < 0.005). Mean IOP was 12.8 ± and 23.9 ± 4.1 mmHg in lions ⩽1 year old and >1 year old, respectively. IOP linearly rose with age during the first 20 months of life, plateaued until approximately 40 months, and then gradually declined (r = 0.85). Age-related changes in IOP were highly correlated with ultrasonographic measurements of intraocular dimensions (r ⩾ 0.72), and may be a determinant factor in developmental ocular growth. The dramatic rise in IOP of young lions is similar to that observed in children, but has not been previously demonstrated in animals. Significant IOP differences between lion sub-species were also demonstrated.