Ultrasound after Iridotomy didn't work for Narrow Angles

I'm 44 and diagnosed with Narrow Angles. Iridotomy was not successful. The holes are open but channels are still narrow with a 5% opening. Why would they schedule an ultrasound if I do not have cataracts? What will an ultrasound reveal that they don't already know about the Narrow Angle?

[John C Hagan III, MD, FACS, FAAO]

You may have an unusual iris configuration called plateau iris which needs a different type of laser, you may have an incomplete hole, you may have scars holding the ange shut. Anterior segment ultrasound can help determine

JCH MD