We have previously discussed many aspects of creating phaco incisions with a keratome and you can find those articles / videos here. One critical error that I see novice surgeons make is inserting the keratome too far into the eye, often going across the anterior chamber.
Good Form: The keratome is inserted only until the widest part of the blade hits Descemet’s membrane and enters the anterior chamber. The blade is then withdrawn in the same path that it was inserted to avoid widening the incision.
Bad Form: When the keratome is inserted deep within the eye so that the entire sharp tip enters the eye and often goes across the anterior chamber. This has the potential for many issues such as damaging the lens capsule or other delicate intra-ocular structures and inadvertently widening the incision as it is withdrawn.
Note: Some experienced surgeons do a technique where they use the keratome to intentionally puncture the anterior lens capsule to start the capsulorhexis. This is not commonly performed and I do not recommend it for surgeons who have done less than 1000 cataract surgeries. Personally, I do not perform this technique since I find it imprecise and not the best tool for the job.
Click below to learn (again) proper form for keratome use: