Abstract
Purpose::
To evaluate the relationship between orbital and intraocular pressure in an experimental model for orbital hemorrhage, and to evaluate the effectiveness of canthotomy, cantholysis, and subsequent septolysis.
Methods::
Orbital hemorrhage was simulated by injecting 22 ml of whole blood into the retrobulbar (intra-conal) space of eight orbits of four fresh, unfixed human cadavers. At each 1 ml increment, orbital pressure (using a Stryker Intracompartmental Pressure Monitor System TM) and intraocular pressure (using a Tonopen TM) were documented. Canthotomy and cantholysis was then performed followed by septolysis. Intraocular and orbital pressure were recorded following each step. To evaluate the effect a canthotomy and cantholysis in the setting of continued hemorrhage, an additional 10 ml was injected with similar measurements taken at 1 ml increments.
Results::
Mean orbital pressure at 0 and 22 ml was 4.9 +2.2 and 62.4 + 33.5 mmHg, respectively. Mean intraocular pressure at 0 and 22 ml was 12.8 + 3.4 and 67.9 + 20.0 mmHg, respectively. There was a close correlation between orbital and intraocular pressure (Pearson coefficient = 0.97) with an average difference of 11.4 + 4.3 mmHg. Mean (+ standard deviation) orbital pressure before and after canthotomy and cantholysis (62.4 + 33.5 and 23.6 + 11.0 mmHg, respectively) was significantly different (p=0.002). There was a small but significant improvement in orbital and intraocular pressure after performing a septolysis, such that orbital and intraocular pressure decreased by an average of 3.4 mmHg and 6.3 mmHg, respectively (p=0.001 and p<0.05). Injection of an additional 10 ml resulted in a dramatic rise in orbital and intraocular pressure at an incremental rate similar to that seen pre-cantholysis.
Conclusions::
A close correlation between orbital and intraocular pressure (average difference of 11.4 mmHg) was observed. Moreover, there was a significant reduction of orbital pressure (62% decrease) after following lateral canthotomy and cantholysis. Septolysis further reduced orbital and intraocular pressure. However, the effect of canthotomy and cantholysis are short lived in the setting of continued bleeding with pressures increasing at a similar rate to that seen pre-cantholysis.
Keywords: trauma • orbit • intraocular pressure