A pilot study on the corneal curvatures and ocular dimensions of horses less than one year of age.
Authors: Townsend W M, Wasserman N, Jacobi S
Journal: Equine veterinary journal
Summary
# Editorial Summary Cataract surgery in foals and weanlings is common, yet the suitability of intraocular lenses (IOLs) designed for adult horses remained unestablished due to potential developmental differences in juvenile ocular anatomy. Townsend and colleagues measured five key ocular parameters in young horses using A and B scan ultrasonography (10 foals) and photokeratometry (7 weanlings), providing the first systematic data on anterior chamber depth, lens thickness, vitreous chamber depth, axial globe length and corneal curvature in horses under one year of age. Foals demonstrated significantly smaller axial dimensions than adults—mean anterior chamber depth of 4.94 mm, lens thickness of 9.38 mm, vitreous depth of 18.96 mm and total globe length of 33.32 mm—whilst corneal curvature (15.4 diopters) fell within the adult range reported in literature. These morphometric differences suggest that adult IOL power calculations would produce substantial refractive errors in juvenile patients, potentially leaving operated foals hyperopic and compromising visual function throughout life. Practitioners considering IOL implantation in young horses should recognise that paediatric-specific lens selection or alternative surgical approaches may be necessary to achieve appropriate refractive outcomes, though further research is needed to establish optimal IOL specifications for this population.
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Practical Takeaways
- •Current adult equine IOL designs may not be suitable for cataract surgery in foals and weanlings due to smaller eye dimensions; consultation with ophthalmologists is essential before implanting adult IOLs in young horses
- •Practitioners should be aware that juvenile equine eyes have different optical properties than adult eyes, which may affect surgical planning and visual outcomes in young animals requiring cataract surgery
- •Further research is needed to develop appropriate IOL specifications for the juvenile equine eye
Key Findings
- •Foals less than one year of age have significantly smaller axial dimensions than adult horses: mean ACD 4.94 mm, CLT 9.38 mm, VCD 18.96 mm, and AGL 33.32 mm
- •Mean corneal curvature in juvenile horses is 15.4 diopters, similar to some reported adult values
- •Differences in axial dimensions between juvenile and adult equine eyes suggest that IOLs designed for adult horses may not provide appropriate refractive correction in foals and weanlings