Episcleral Venous Pressure in Normal Eyes and in Eyes with Thyroid Ophthalmopathy

Abstract

Abstract: : Purpose: To determine if episcleral venous pressure (EVP) is elevated in subjects with thyroid eye disease compared to age-, race-, and gender-matched controls. Methods: Subjects with thyroid eye disease were prospectively identified by an orbital surgeon. IRB-approved informed consent was obtained from each subject prior to their participation. Subjects with ocular disease processes likely to be associated with abnormalities of episcleral venous pressure or intraocular pressure were excluded. The EVP was measured using an episcleral venomanometer (Model EV-310; Eye Tech Ltd, Morton Grove, IL). Subjects underwent two EVP measurements for each eye. This was performed by an observer masked to the subject's diagnosis. The EVP was measured after instillation of topical proparacaine HCl 0.5% by placing the tip of the silastic membrane of the episcleral venomanometer perpendicular to the globe, temporal to the limbus, such that the flexible tip was in contact with the conjunctival surface. When the episcleral vein was viewed through the silastic membrane, pressure was applied until half-blanching of the observed vesssel occurred. The pressure was read on a scale by an observer other than the one performing episcleral venomatometry. Healthy, normal volunteers (age-, gender-, and race-matched with subjects with orbital disease) who were not receiving ocular or systemic vasoactive medications served as controls. To minimize bias, the episcleral venomanometry operator who performed the EVP measurements was masked as to subject characteristics. To maintain consistency all measurements were performed by the same investigator. Results: Reliabe data were obtained for 21 eyes of 12 subjects with thyroid eye disease and 8 eyes of 5 control subjects. The mean EVP for eyes with thyroid ophthalmopathy was 10.70 (SD ±2.02) mm Hg (range 7.5-15.25 mm Hg). The mean EVP for control eyes was 8.87 (SD ±1.10) mm Hg (range 7-10 mm Hg). There was a statistically significant difference between the two groups (p=0.023). Conclusions: We observed a significantly higher EVP in eyes with thyroid ophthalmopathy compared to normal control eyes.

Keywords: clinical research methodology • orbit