High resolution ultrasonic biometry was performed on 25 normal eyes of presbyopic volunteers (60 to 80 years old) prior to and at 15-minute intervals after topical instillation of 2% pilocarpine hydrochloride. Every eye measured demonstrated an axial thickening of the lens (average 0.25 mm) and 85% of the eyes demonstrated a shallowing of the anterior chamber (average 0.19 mm).
Pilocarpine has a measureable effect within 15 minutes on the anterior chamber and lens thickness in some patients. Its maximal effect is 45 to 60 minutes after instillation. The elderly presbyopic lens is able to be deformed under pilocarpine stimulation.
Abramson DH, Franzen LA, Coleman DJ. Pilocarpine in the PresbyopeDemonstration of an Effect on the Anterior Chamber and Lens Thickness. Arch Ophthalmol. 1973;89(2):100-102. doi:10.1001/archopht.1973.01000040102006