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S. A. Read, M. J. Collins, H. Becker, J. Cutting, D. Ross, A. Savill-Inns, B. Trevor; The Influence of Accommodation on Intraocular Pressure and Ocular Pulse Amplitude. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2807.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the influence of accommodation on intraocular pressure (IOP) and ocular pulse amplitude (OPA) in myopic and emmetropic subjects.
Fourteen progressing myopic and eighteen emmetropic young adult subjects (mean age 23 ± 3 years) had their IOP and OPA measured using the Pascal dynamic contour tonometer. Baseline IOP and OPA were initially taken following seven minutes of viewing of a distant target. Subjects then fixated on a near target (accommodative demand 3D) for 2 minutes and measures of IOP and OPA were repeated. Baseline measurements of axial length were also captured using the IOLMaster instrument prior to the IOP measures.
IOP exhibited a significant decrease with accommodation in both myopic and emmetropic subjects (mean change: -1.8 ± 1.2 mmHg, p<0.001). There was no significant difference (p>0.05) between the myopic and emmetropic subjects in terms of baseline IOP (mean myopic baseline IOP 17.7 ± 2.0 mmHg, mean emmetropic IOP 16.80 ± 2.9 mmHg) or in the magnitude of change in IOP with accommodation (mean change in IOP -1.7 ± 0.8 mmHg and -1.9 ± 1.4 mmHg for the myopic and emmetropic groups respectively ). OPA also exhibited a significant decrease with accommodation (mean change for all subjects -0.5 ± 0.5, p<0.001). The myopic subjects (baseline OPA 2.05 ± 0.66 mmHg) exhibited a significantly lower baseline OPA (p=0.016) than the emmetropic subjects (baseline OPA 3.06 ± 1.36 mmHg), and a significantly lower magnitude of change in OPA with accommodation (mean change in OPA with accommodation was -0.2 ± 0.4 mmHg and -0.6 ± 0.5 mmHg for the myopic and emmetropic subjects respectively, p=0.015).
IOP decreased significantly with accommodation, and exhibited no significant difference between progressing myopic and emmetropic subjects. These findings do not support a simple mechanical role for IOP in myopic axial elongation. However, the differences found between myopes and emmetropes in baseline OPA and in the change in OPA with accommodation suggest some changes in IOP dynamics associated with myopia.
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