Tonographic Effect of Ocular Response Analyzer in Comparison to Goldmann Applanation Tonometry

Abstract

AimsThe tonographic effect is a phenomenon of intraocular pressure (IOP) reduction following repeated tonometry. This study examines whether the tonographic effect occurs following IOP measurement performed with Ocular Response Analyzer (ORA).MethodsBoth eyes of 31 glaucoma patients and 35 healthy controls underwent nine IOP-measurements performed with GAT and ORA. The number of GAT and ORA measurements performed on each eye differed depending on the randomly allocated investigation scheme. Central corneal thickness (CCT), anterior chamber volume (ACV) and anterior chamber depth (ACD) were assessed with Pentacam before and after the repeated GAT/ORA measurements.ResultsThere was no statistically significant tonographic effect for IOP readings obtained by the ORA: corneal compensated intraocular pressure (IOPcc) (-0.11 ± 3.06 mmHg, p = 0.843 in patients and -0.71 ± 3.28 mmHg, p = 0.208 for controls) and Goldmann-correlated intraocular pressure (IOPg) (-0.31 ± 2.38 mmHg, p = 0.469 in patients and -0.31 ± 2.37 mmHg, p = 0.441 in controls) measured with ORA. There was a significant IOP reduction from the first to the second GAT measurement, i.e. tonographic effect (-0.55 ± 2.00 mmHg, p = 0.138 in patients and -1.15 ± 1.52 mmHg, p < 0.001 in controls). CCT, corneal hysteresis (CH) and corneal resistance factor (CRF) were lower in glaucoma patients. The repeated IOP measurements resulted in an increase of CCT in all subjects (but no change of ACV and ACD). The tonographic effect of GAT correlated with CCT in glaucoma patients (r = 0.37).ConclusionIn contrast to GAT, repeated ORA measurements do not result in the tonographic effect. Repeated IOP measurements resulted in an increase of central corneal thickness, but did not influence the volume and depth of anterior chamber.

Relationship of corneal hysteresis and optic nerve parameters in healthy myopic subjects

“…According to the methodology of the EPIC-Norfolk Eye Study, both healthy eyes and eyes with glaucomatous damage were included in the analysis 9 . Previous studies have shown that CH is significantly lower in glaucomatous eyes 3 , 5 . A positive correlation found between CH and RNFL measurement in their study might at least partially be explained by the effect of glaucoma damage on CH and RNFL.…”

“…Corneal biomechanics has been an area of much recent interest as a risk factor for glaucoma development and progression 1 – 3 , 5 – 7 . In the present study, we aimed to evaluate the relationship between CH and quantitative measurements of the RNFL and optic disc.…”

“…The association between corneal biomechanical properties and glaucoma is an area of much interest 1 – 3 . The Ocular Response Analyzer (ORA) has been developed to analyze in vivo corneal biomechanical properties including the corneal hysteresis (CH) and the corneal resistance factor (CRF) 4 .…”

The influence of the tonometer position on canine intraocular pressure measurements using the Tonovet^® rebound tonometer

“…No disturbance or damage to the cornea was observed. However, it is well known that some applanation tonometers produce the tonographic effect, which is a phenomenon in which IOP values decline with repeated tonometry (Stocker, 1958;Moses, 1961;Krakau and Wilke, 1971;Gaton et al, 2010;Zimmermann et al, 2017). In a study of repeated rebound tonometry in children, the tonographic effect did not occur (Dosunmu et al, 2014).…”

Intraocular pressure remote photonic biomonitoring based on temporally encoded external sound wave stimulation

“…It was found that biochemical cornea properties influence the accuracy of applanation tonometry. 20,21 The ocular response analyzer [22][23][24][25] allows adjustment of IOP taking into consideration the biomechanical properties of the cornea. An alternative way of measuring IOP is by air puff tonometer.…”