Aim: To measure the stimulus and response AC/A ratios using the distance prism cover test gradient method in young adults without strabismus or ocular abnormality. Methods: AC/A ratios were measured in a group of orthoptic students. The distance deviation (at 3.8 m) was measured with an alternate prism cover test using a Gulden prism bar with and without À3.00DS lenses. A Shin-Nippon SRW-5000 autorefractor [Grand Seiko Company, Fukuyama, Japan] (open view) was used to measure the refractive state with and without a À3.00DS lens. The stimulus and response AC/A ratios were calculated. Results: Data were analysed for 16 participants. The mean and standard deviations (SD) of the distance stimulus gradient AC/A ratio were 1.98:1 (1.30) and the mean (SD) distance response gradient AC/A ratio were 2.43:1 (1.60). A paired t-test found a significant difference between the distance response and stimulus gradient AC/A ratio values (t = 3.58, p = 0.003). A Bland-Altman plot suggested that the difference increased as the size of AC/A ratio increased. Conclusion: The response gradient AC/A ratio when measured using the prism cover test at a distance of 3.8 m was found to be higher than the stimulus AC/A ratio in a group of normal participants who were orthoptic students. This is due to the accommodative lag which normally occurs when viewing through minus lenses.

Aim: To report the alignment, visual outcome and surgical strategy for severe bilateral congenital esotropia caused by a congenital cranial dysinnervation disorder (CCDD). This was successfully treated with a combination of interventions that included alternate occlusion, botulinum toxin, and conventional and augmented transposition procedures. Methods: A girl presented at 2 months of age with a marked esotropia and severe bilateral impairment of abduction of both eyes, and an inability to fix with either eye in the primary position. Her investigation and treatment are described. Results: The patient initially underwent alternate daily occlusion to prevent the development of amblyopia, followed by simultaneous bilateral medial rectus (MR) botulinum toxin and large bilateral MR recessions based on pre-operative forced duction testing (FDT). This operation was performed at 1 year of age with the aim of releasing the tight MR and reducing the esotropia. After initial improvement, the impairment of abduction gradually increased over the next month. She subsequently underwent sequential inferior oblique myectomy and augmented transposition procedures, which enabled her to fix in the primary position with either eye and with a small-angle esotropia. Conclusion: Substantial improvement in the alignment of the eyes in a child with a complex congenital esotropia secondary to a CCDD is achievable.