The lens and cataracts.

The research article discusses the occurrence of lens opacity, ranging from minor opacities to extensive cataract, in horses with clinically normal eyes, and the impact of complete and incomplete cataracts on the vision of the affected horses.

Prevalence of Lens Opacity

• It is estimated that 5% to 7% of horses with clinically normal eyes have some form of lens opacity. This means that even in cases where the horse appears to be visually healthy, there’s a chance of occurrence of lens opacity.

Variety in Opacities

• The opacities can vary greatly in size and intensity, starting from minor remnants of the fetal vasculature, called epicapsular remnants, to dense and extensive cataracts which can significantly affect the horse’s vision.

Categorization of Cataracts

• A technical definition for cataracts in this study is described as any alteration or opacity in the lens’s optical homogeneity that involve one or more segments like the anterior epithelium, capsule, cortex, or nucleus.
• In horses, cataracts are seldom full or complete, affecting the entire lens. Most of the time, they are localized to a specific sector or anatomic landmark in the lens.

Impact on Vision

• Complete or full cataracts in horses lead to significant visual disability. This is because the opacity affects the entire lens, hindering the full transmission of light, thus disrupting the visual ability of the animal.
• On the other hand, horses with localized cataracts, also referred to as focal or incomplete cataracts, don’t typically show apparent signs of visual dysfunction. This is because the opacity or alternation affects only a part of the lens, allowing for most light to transmit for vision.