Spring loaded mouth gags are a recognised cause for cats to wake up with cortical blindness. This unnecessary complication is thought to arise from excess tension created by the springs, leading to Maxillary artery compression. The subsequent hypoxia results in central blindness that can be temporary or permanent.
It is recommended to use nail clippers to cut a 25g needle cap into 20mm length and use this between the canine teeth instead. Studies have shown that this length is safe.