Abstract
Purpose :
To compare the results in retinal venous pressure (RVP) in healthy subjects measured by a contact lens dynamometer (CLD) and by a new method in which the cornea remains untouched and the pressure is measured by a generally available tonometer.
Methods :
Measurements were carried out at a biomicroscope in mydriasis left eyes of 36 healthy volunteers as described in table 1. RVP measurement was done by the Loew CLD and by a new device called IOPstim. In this method a collapsible pelotte of 8mm diameter is positioned in deflated state on the lateral sclera. The pelotte is mounted on a frame which is fixed on the head of the patient. It is inflated by the basic unit operated by a pedal. In measuring the RVP the examiner observes the central retinal vein (CRV) and its branches on or near the optic disc by a 90 diopter lens. The filling of the pelotte induces a rise in intraocular pressure (IOP). As soon as one of the observed vessels pulsates the inflation is stopped and the IOP is measured by a commercially available tonometer. Examination procedure: Rebound tonometry (RT), mydriasis, RT, systemic blood pressure (BP) randomisation of the procedures: IOPstim or CLD first, IOP, 3 RVP measurements (RVPM) in quick succession during Valsalva maneuver (VM). The air pressure (AirP) of 20mmHg was visually controlled by the subject on a manometer), BP, IOP, 5 minutes break, IOP, second method CLD or IOPstim, 3 RVPMs under the same conditions as in first method. IOP, BP.
Results :
The RVPM values are given in table 2. The 3 single RPMs show a very good reliability with an intra-class correlation coefficient above 0.8 with each method. Their means don’t differ widely (ANOVA: p<0.05). The RVPM values by CLD are 13mmHg higher than by the IOPstim. The minimal increase of IOP by mere attachment of the device is 10.1 mmHg in the CLD and 2.6 mmHg in the IOPstim.
Conclusions :
This is the first study in which the new IOPstim was compared with the CLD. In order to stop the spontaneous pulsation of the CRV the AirP was risen to 20 mmHg during the RVPMs. We know from earlier studies that under these conditions the RVP shows a wide scatter which may be a major reason for the scatter obtained here. The reliability of the measured values, however, is very good. In the CLD method the main force vector is directed to the apex of the orbit whereas in the IOPstim method to the nasal orbital wall. this may explain the different results obtained by the two methods.
This is a 2020 ARVO Annual Meeting abstract.