Effects of Static Accommodation Versus Repeated Accommodation on Intraocular Pressure

PURPOSE: To compare the influences of static and repeated accommodation on the intraocular pressure (IOP). MATERIALS AND METHODS: A randomized, single-blind study was carried out on 33 healthy volunteers aged 20 to 29 years. Baseline IOP was measured after 10 minutes of viewing a distant target. Static accommodation was achieved by letting the volunteers focus for 3 minutes on a near target, which was individually adjusted to induce a 3 D accommodative demand. For the repeated accommodation, the volunteers were instructed to alternately focus on the near and distant target for 3 minutes. The accommodative responses were continuously monitored by an infrared photorefractor (PowerRef II), and Goldmann tonometry was performed immediately after the accommodative procedures. RESULTS: The IOP values (mean±SD) measured after static and repeated accommodation were 13.4±2.4 mm Hg and 12.7±2.3 mm Hg, respectively (P=0.04). The IOP decreased significantly from baseline after both the static and repeated mode of accommodation with a mean change of -1.76±1.17 mm Hg (range, 0 to 4 mm Hg) and -2.06±1.48 mm Hg (range, 0 to 5 mm Hg), respectively. The IOP drop seemed to be greater after repeated accommodation compared with static accommodation; however, the difference was not statistically significant (P=0.35). CONCLUSIONS: The IOP was significantly reduced after both static and repeated accommodation. Compared with static accommodation, the repetitive mode of accommodation did not induce a statistically significant additional IOP drop, indicating that aqueous humor outflow is relatively unaffected by frequent ciliary muscle contractions.