Transpalpebral measurement of intraocular pressure with the Tono-Pen XL, in a young, healthy, adult population

Identification of increased intraocular pressure has been conventionally limited by direct, corneal applanation, and indentation measurement procedures, conducted by highly trained eye-care specialists e.g. optometrists and ophthalmologists. This practice greatly limits the numbers of individuals which can and need to be screened, for increased intraocular pressures. Increased intraocular pressure is the second leading cause of preventable, irreversible blindness throughout the world and a major modifiable risk factor for the development and progression of glaucoma. Current screening practices are inadequate, leaving many undetected, resulting in high base-rates of unnecessary and preventable blindness worldwide. Three primary research questions are investigated: Can intraocular pressures be measured through the eyelid, using the Tono-Pen XL tonometer? If yes, can the transpalpebral values be transformed to approximate corneal values? If yes, are the transformed values sufficiently precise, accurate, and reliable to substitute for intraocular pressure values measured directly from the cornea, for screening purposes?. Ninety (n = 90), healthy, young, adults completed measurement of intraocular pressures, from each eye (n = 180 eyes), using the Tono-Pen XL tonometer. Intraocular pressures were measured directly from the cornea and then directly from the closed eyelid. Transpalpebral measurements were transformed by simple linear regression to estimate direct corneal measurements. Transformed values were assessed for accuracy, precision, reliability, and agreement with direct corneal measurements. Findings revealed high accuracy, precision, reliability, and agreement between direct corneal and transpalpebral measurements. Transformed transpalpebral measurements correctly classified 95% and 93% of subjects, within 4 mm Hg or less of direct corneal measurements, when intraocular pressures were measured from the right and left eyes, respectively. Intraocular pressures measured directly from the closed eyelid, using the Tono-Pen XL, can be linearly transformed, using simple linear regression, to estimate intraocular pressure values measured directly from the cornea with high agreement, precision, and reliability, in a healthy, young, adult population. Findings have implications for non-eye-care specialists e.g. primary care physicians, choosing to quickly, accurately, and reliably screen individuals for normal intraocular pressures, without the need to anesthetize the eyes or use expensive, office-bound. equipment.