Many of Asian patients have small eyes with narrow eyelid fissures. When you have a patient with a small eyelid opening, you will have difficulty putting the suction ring onto the eyeball. In patients whose eyelid fissure is narrow, usually the lid speculum will fit, but the eyelid cannot open wide, so the suction ring cannot get past the lid speculum to work properly. The applanation tonometer helps to find a safe pressure before cutting the cornea. When the darker contact circle is larger than the white reference circle, the IOP is too low.
Cutting can result in a poor corneal flap.
When the darker contact circle is smaller than the white reference circle, cutting will result in a good corneal flap. The cause of the low IOP must be checked before making the corneal flap. The eyeball will protrude. This will allow the suction ring to be in contact with the eyeball. When suction is turned on, the eyeball can be lifted gently in the orbit.