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Botulinum toxin type A (BTXA) injections to the extraocular muscles have been well described in the treatment of strabismus. However, evidence on inferior rectus (IR) injection is scarce.Retrospective review of patients who underwent IR BTXA between 2001 and 2024 for vertical strabismus. Natural Language Processing using language model, Mixtral-8x7B, identified eligible patients.Seventy-one patients (n=85 eyes) were identified. Cases were classified into comitant (n=41 eyes), incomitant (n=29 eyes), and restrictive strabismus (n=15 eyes). The average pre-injection deviation at near was 13.0±7.1PD, 11.2±11.1PD and 14.1±8.3PD respectively, and 13.5±8.7PD, 9.0 ±7.3PD and 14.2±9.8PD respectively at distance. The average post-injection deviation at near was 9.2±6.3PD, 10.0±10.4PD, 7.5±8.1PD respectively, and 9.3±6.6PD, 7.5 ±7.5PD and 7.8±5.7PD respectively at distance. Treatment success, which was defined as recorded satisfactory improvement or resolution of symptoms, was reported in 23 (56.1%), 9 (32.1%) and 11 (73.3%) cases in the comitant, incomitant and restrictive groups respectively.IR BTXA had the highest success rate in restrictive strabismus, followed by comitant strabismus and incomitant strabismus. The observed outcome is presumably due to the gradual onset in most restrictive cases with enlarged fusion ranges. The majority of cases in the incomitant group had a history of previous strabismus surgery, which makes BTXA less favourable.IR BTXA injection is an effective option for patients with vertical strabismus, especially with restrictive strabismus.