The methods used to apply the ink to the cornea differ. In one such method, the physician applies the ink into the cornea stroma by multiple punctures, covering the needle with ink each time. In another method, the physician would cover a three-edged spatula needle with ink before each puncture. He would then apply the ink into the anterior corneal stroma with each puncture. Samuel Theobald would inject the eye first with a needle and then rub in the ink with a Daviel curet. This would prevent against the often obscure field of operation known to other physicians and also prevent against repetitive irrigation sometimes needed.