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C.I. Zoumalan, J.D. Bullock, R.E. Warwar, B. Fuller, T.J. McCulley; The Relationship Between Orbital Pressure and Intraocular Pressure Following Orbital Hemorrhage: An Experimental Model . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3786.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the relationship between orbital and intraocular pressure in an experimental model for orbital hemorrhage.
Retrobulbar hemorrhage was simulated by injecting 22 ml of whole blood into the retrobulbar (intra–conal) space of four orbits of two fresh, unfixed human cadavers. At each 1 ml increment, exophthalmometry measurements (using a Hertel TM exophthalmometer), orbital pressure (using a Stryker Intracompartmental Pressure Monitor System TM) and intraocular pressure (using a Tonopen TM) were documented. Pearson correlation was used to assess the relationship between orbital and intraocular pressure. Additionally, the average differences for the first and last 7 ml of whole blood injection were determined and compared using a two–sided T–test.
Mean exophthalmometry measurements at 0 and 22 cc were 14.25 + 0.5 and 24 + 1.4 mm, respectively. Mean orbital pressure at 0 and 22 cc was 4 +1.83 and 52 + 15.8 mmHg, respectively. Mean intraocular pressure at 0 and 22 cc was 14 + 0.5 and 67 + 6.9 mmHg, respectively. There was a close correlation between orbital and intraocular pressure (Pearson coefficient = 0.97) with an average difference of 15 + 3 mmHg. This remained similar for the initial and final 7 ml, 16 + 2 mmHg and 14 + 4 mmHg, respectively (p=0.70). Changes in exophthalmometry values less closely paralleled changes in orbital and intraocular pressure (both with Pearson coefficient = 0.84). Initially, exophthalmometry measurements increased with little change in orbital and intraocular pressure. As exophthalmometry values began to plateau, a substantial rise in orbital and intraocular pressure was observed.
In our experimental model for orbital hemorrhage, a close correlation between orbital and intraocular pressure was observed, with orbital pressure remaining roughly 15 mmHg less than intraocular pressure. Therefore, our data suggests that intraocular pressure can be used to estimate orbital pressure.
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