A pilot study on the corneal curvatures and ocular dimensions of horses less than one year of age.

Intraocular lenses (IOLs) have been implanted in adult equine eyes after cataract surgery. Foals and weanlings comprise a large proportion of those horses undergoing cataract surgery. Due to potential differences in the size and corneal curvature of the juvenile eye, it is not currently known whether implantation of adult IOLs is appropriate in foals and weanlings. The objective of the study was to measure the anterior chamber depth (ACD), central lens thickness (CLT), vitreous chamber depth (VCD), axial globe length (AGL) and corneal curvature of horses less than one year of age. The axial dimensions from one eye of 10 foals were measured using simultaneous A and B scan ultrasonography. The corneal curvature from one eye of 7 weanlings was determined using a modified photokeratometer. Ultrasonography revealed a mean ACD of 4.94 mm, mean CLT of 9.38 mm, mean VCD of 18.96 mm and mean AGL of 33.32 mm for the foals. The mean corneal curvature was 15.4 diopters (D). The mean ACD, CLT, VCD and AGL of the foals were less than the measurements reported in the literature for adult horses. The mean corneal curvature was similar to the values reported by some authors for adult horses. Due to the differences in axial dimensions between adult and juvenile eyes, an IOL that corrects vision in an adult horse might not adequately correct vision in a horse less than one year of age.