You are buyding on a used Heidelberg intraoperative pachymeter /thickness gauge using OCT. The unit comes with its user manual. I am not familiar with this piece of equipment, but my understanding is that it uses OCT to measure corneal thickness during refractive corneal surgery. Not sure if it is fully functional or not so it is being sold as is.
Items are sold as-is with no returns or refunds available unless explicitly stated.