Changes in Intraocular Pressure and Ocular Pulse Amplitude with Accommodation

Aims: To investigate the change that occurs in intraocular pressure (IOP) and ocular pulse amplitude (OPA) with accommodation in young adult myopes and emmetropes.

Methods: Fifteen progressing myopic and 17 emmetropic young adult subjects had their IOP and OPA measured using the Pascal dynamic contour tonometer. Measurements were taken initially with accommodation relaxed, and then following 2 min of near fixation (accommodative demand 3 D). Baseline measurements of axial length and corneal thickness were also collected prior to the IOP measures.

Results: IOP significantly decreased with accommodation in both the myopic and emmetropic subjects (mean change -1.8+/-1.1 mm Hg, p<0.0001). There was no significant difference (p>0.05) between myopes and emmetropes in terms of baseline IOP or the magnitude of change in IOP with accommodation. OPA also decreased significantly with accommodation (mean change for all subjects -0.5+/-0.5, p<0.0001). The myopic subjects (baseline OPA 2.0+/-0.7 mm Hg) exhibited a significantly lower baseline OPA (p=0.004) than the emmetropes (baseline OPA 3.2+/-1.3 mm Hg), and a significantly lower magnitude of change in OPA with accommodation.

Conclusion: IOP decreases significantly with accommodation, and changes similarly in progressing myopic and emmetropic subjects. However, differences found between progressing myopes and emmetropes in the mean OPA levels and the decrease in OPA associated with accommodation suggested some changes in IOP dynamics associated with myopia.