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S. R. Gatla, A. L. Williams, I. Fahmy, D. Borros, S. Dubey, R. Ramakrishnan, R. Khandelwal, A. Bayer, A. Biswas, G. L. Spaeth; Does Iop Asymmetry Have a Diagnostic Value?. Invest. Ophthalmol. Vis. Sci. 2010;51(13):585.
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To investigate the amount of intraocular pressure (IOP) asymmetry between fellow eyes in patients with and without glaucoma.
Materials and Methods: :
Collaborative retrospective study of 389 glaucoma patients and 389 controls. Data was collected from the medical records of various clinics in several countries. The investigators (former Wills Eye Institute Fellows) collected single measurements of pre-treatment levels of IOP in patients who were diagnosed as having primary open-angle glaucoma based on characteristic optic nerve damage and characteristic confirmatory glaucomatous visual field damage. Patients with all other types of glaucoma and previous ocular surgery were excluded. Patients with refractive error, cataract or with a normal eye examination, who had an IOP measurement in each eye below 25 mmHg, and who had normal appearing optic discs and no apparent glaucoma, were used as controls.
Regarding the glaucoma patients: average age 69 years, 46% female, average IOP of right eye 24 mmHg and left eye 23 mmHg. Regarding controls: average age 61 years, females 55%, average IOP 16 mmHg in both eyes. Ethnicities included Asian (26%), Black (21%), Caucasian (26%) Latino (8%) and North African (19%). The frequency of cases with a particular amount of apparent asymmetry is shown in Table1.Table1.
These results show a direct relationship between the amount of IOP asymmetry between the fellow eyes and the likelihood of having glaucoma(p=0.000). Absence of IOP asymmetry between the fellow eyes is associated with a 0.5% probability of having glaucoma. A difference of 3 mmHg is associated with a 10% probability of having glaucoma, a difference of 6 mmHg with a 50% probability and difference of >6 mmHg a 100% probability of having glaucoma. The unadjusted odds ratio was 2 (p=0.000), indicating that with every 1 mmHg rise of IOP asymmetry the risk of glaucoma doubles.
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