Purpose
The purpose of the study is to quantify retinal venous pressure (RVP) in a healthy population and its influence on ocular perfusion pressure (OPP) calculation. Retinal venous pressure is assumed to be equal to intra ocular pressure (IOP) and therefore a visible spontaneous venous pulsations (SVP) should be observed. Due to this assumption the currently used calculation of ocular perfusion pressure is equal 2/3 Mean Arterial Pressure (MAP) - IOP. We have clinical and scientific evidence that this assumption, IOP = RVP, however, is not always correct. Neither is spontaneous venous pulsation always visible in healthy people, nor in diseased eyes, especially in glaucomateous eyes (Morgan et al. 2004, Seo et al. 2012, Stodtmeister et al. 2013).
Methods
160 healthy volunteers between the age of 18 and 80 years were recruited for this descriptive, clinical series study. As an age effect was expected, all volunteers were divided into three age groups. Age group 1 18-39 years, age group 2 40-59 years and age group 3 60-80 years of age. Exclusion criteria are a history of any ocular or systemic diseases. Averaged intra ocular pressure was measures by non-contact tonometry (NIDEK Tonoref II) and retinal venous pressure was measured by digital Ophthalmo-Dynamometry by Dr. Loew. The results are presented as differences of means (p = 0.05) and the prevalence of RVP higher than IOP as histogram. Influence of age and IOP on RVP is presented as linear regression model.
Results
Of the 160 volunteers, 58.1% were female and 41.9% were male. Mean age was 37.9 years (SD 15.5). 96 persons are in age group 1, 45 in group 2 and 19 in group 3. 25.3% of all eyes did show an equal RVP, 74.7% did present a higher RVP as their actual IOP. The mean for IOP in all groups was 15.15mmHg (SD 3.06) and for RVP 23.03mmHg (SD 7.1) and were statistically different to each other (p=0.00). The groupwise means for RVP were 22.4mmHg (group 1), 24.05mmHg (group 2) and 21.6mmHg (group 3) and only siginificant for group 2 (p=0.019 resp. 0.013). There was no statistical significance between age groups for IOP (15.13mmHg; 15.08mmHg; 15.11mmHg).
Conclusions
In our cohort of healthy volunteers only a minority did show a RVP equal to IOP. Therefore the current formula to calculate OPP seem to be questionable. Age had no specific influence on RVP or IOP, but higher IOP correlated with higher RVP.
Keywords: 436 blood supply