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

The study explores the differences in eye size and corneal curvature between adult horses and horses less than a year old (foals and weanlings) to assess whether adult intraocular lenses (IOLs) can be implanted in younger horses following cataract surgery.

Study Objective and Methodology

• The research aimed to measure various aspects of a young horse’s eye such as the anterior chamber depth (ACD), central lens thickness (CLT), vitreous chamber depth (VCD), axial globe length (AGL) and corneal curvature. These measurements would help determine if adult IOLs are suitable for implantation in younger horses.
• The researchers used A and B scan ultrasonography to measure the axial dimensions of the eye in 10 foals. This method allows an in-depth look at intraocular structures without any invasive procedure to the eye.
• In addition, they measured corneal curvature of 7 weanlings’ eyes using a modified photokeratometer, a device that measures the curvature of the anterior surface of the cornea.

Study Findings

• The study found that the mean ACD was 4.94 mm, mean CLT was 9.38 mm, mean VCD was 18.96 mm and mean AGL was 33.32 mm for the foals.
• The corneal curvature of the weanling group had a mean result of 15.4 diopters.
• The mean measures for ACD, CLT, VCD and AGL in foals are smaller than the measurements reported for adult horses. Conversely, the mean corneal curvature is similar to the values found in adult horses.

Implications of the Findings

• The differences in axial dimensions between adult and juvenile eyes suggest that an IOL designed for adult horses may not adequately correct vision in a horse less than one year old.
• This highlights the importance of considering age and size before choosing an IOL for implantation, and further studies may be needed to create IOLs that are suitable for young horses.