Description:
<jats:title>Abstract</jats:title><jats:sec><jats:title>Purpose</jats:title><jats:p>The tonographic effect has been observed in several studies in occulopression, repeated tonometry or ophthalmodynamometry. It describes an intraocular pressure (IOP) decrease caused by an artifical IOP increase. In healthy eyes, an IOP drop of 2–3 mmHg/min was reported. However, there are studies that show a reduced decrease of the IOP drop for instance in glaucoma patients. In this work, we present a proof of principle to determine the tonographic effect in healthy eyes by utilizing a novel pneumatic pressure modulator.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>The study was conducted on 8 healthy subjects (4 m, 4 f, 1 eye each, mean age 27.4 ± 7.1 yr). All subjects passed an ophthalmic examination procedure, including visual acuity determination, tonometry, objective refraction, slit lamp examination. Exclusion criteria were myopia < ‐8 dpt, anamnestic surgeries, corneal scars, eye diseases, ocular hypertension, and ongoing ocular local therapy. No anaesthetics were used. A pressure modulator (IOPstim, Imedos Systems GmbH, Jena, Germany) was used to increase the IOP to initially pathologic IOP values of about 35 mmHg (36.6 ± 2.5 mmHg). The applied pressure was kept constant for 2 minutes. The IOP was measured 4 times (at 0s, 40s, 80s, and 120s) using a rebound tonometer (Icare PRO, Icare Finland Oy, Helsinki, Finland). Linear regression was performed to calculate the average IOP decrease within the 2‐minutes interval.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>For all 8 subjects, a typical decrease of the IOP was observed during a 2 min constant pressure stimulation. The mean decrease of the pressure profiles was 2.77 mmHg/min (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.94).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>We successfully applied a pneumatic pressure modulator to determine the tonographic effect in the human eye. For 2 min we measured the mean decrease of the IOP drop with similar values known by the literature. Application of the pneumatic pressure modulator allows the investigation of pathological reduced IOP drops that differ from normal values as shown in this study.</jats:p></jats:sec>