OBJECTIVES: Equine recurrent uveitis (ERU) is the most common cause of blindness in horses world-wide. Several organisms have been associated with ERU, with leptospires being the most commonly reported agent. Irrespective of substantial treatment costs, the value of affected horses is progressively reduced as ocular involvements (unilateral or bilateral visual impairment or blindness) increase. This study aimed to estimate the number of horses affected by ERU in the U.S, and approximate the associated depreciation due to vision impairment. METHODS: The U.S. horse population size was estimated by market research. Published sources allowed the estimation of (1) the risk of ERU, (2) the associated visual impairments, accounting for breed differences, and (3) the loss of value in function of different ocular involvements and variable uses of a horse. Considering U.S. horse breeds and use distributions, the number of horses allocated to different levels of vision impairment and associated relative depreciations were calculated. Average value of horses was derived from official sources, conservatively excluding very high-priced competition/race horses. RESULTS: It was estimated that 576,000 horses are currently affected by ERU in the U.S. Based on retrospective studies, 198,513 and 104,269 of these horses are or are expected to become blind in one or both eyes during the next 11 years, respectively. From those horses being impaired but maintaining vision, 151,046 horses are unilaterally and 122,172 bilaterally affected. Depreciation in horses currently affected by ERU was conservatively calculated to $802,482,773.  It was estimated that 70% of those losses are caused by leptospires. CONCLUSIONS: Approximately 576,000 horses are currently affected by ERU in the U.S., from which more than 300,000 horses will become blind in one or both eyes. ERU represents a substantial economic burden which conservatively calculates to more than $800 MM due to the loss of horse value, not considering treatment costs.