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Daniel R. LaMothe; Intraocular Air Volume Estimates Using Computed Tomography Scan A Combat Scenario. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4971.
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To determine if military ophthalmologists and ophthalmology residents can accurately estimate volumes of intraocular air under the premise of a combat scenario with limited quality CT images in order to determine if casualties can be moved by air out of a combat zone. Current guidelines within the Department of Defense limit all air travel for personnel with any intraocular air. The medical literature supports the safety of air travel for patients with less than 0.6 mLs of intraocular air. Additionally, case reports have shown that volumes greater than this are also safe during air travel.
A total of 12 cadaveric heads were used during this study, and both eyes were utilized for each head studied. The eyes were injected with a known amount of intraocular air or saline. The volumes used were 0.25, 0.50, 0.75, and 1.00 mLs of air or enough saline to re-form the globes. The heads underwent immediate CT scanning using a CereTom portable CT scanner. Given the disorganized nature of the cadaveric eyes and the fact that a portable CT scanner was used, a combat scenario was developed to simulate military medical practice in an austere environment. The images were loaded into the Impax viewing system at Wilford Hall Medical Center. Ophthalmology staff and residents were asked to review all CT images and estimate the volume of intraocular air in each eye. The results were analyzed to determine if the estimates were accurate.
The volume estimates for all eyes tested fell within a small range of values with rare outliers. The means for each test volume were then used for analysis to determine whether estimates were statistically significantly different from the known test volumes. Analysis was completed with a t test for the equality of means, and the data showed that the estimates taken as a whole were accurate for all known test volumes (control eyes p value=0.474, 0.25 mL test eyes p value=0.563, 0.50 mL test eyes p value=0.971, 0.75 mL test eyes p value=0.698, 1.00 mL test eyes p value=0.624).
Current aeromedical evacuation guidelines limit air travel for personnel injured in a combat zone who have persistent intraocular air. Medical literature supports the safety of air travel for patients with less than 0.6 mLs of intraocular air. Individual case reports have shown the safety of greater volumes or air as well. This study was designed to determine if based on poor quality CT scans, to simulate the austere military deployed environment, volumes of intraocular air could be determined with accuracy. The results support the ability of military ophthalmologists to determine the volume of intraocular air based on these poor quality CT scans, and whether a given injured service member can safely travel out of a combat zone via air.
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