Impact of Tear Break-up Time Test Results on Corneal Imaging Using Scheimpflug-based Technology in Patients with Dry Eye

Background: Unstable tear film in dry eye can produce corneal thinning and surface irregularity which cause optical aberrations like erroneous keratometric measurements and altered central corneal thickness. A reduction in the accuracy and repeatability of these measurements is known in these pathologic cases (DED) and results are expected to be unpredictable, unreliable. Objective: To compare between the keratometry readings and central corneal thickness values before and after installation of tear substitute in patients with abnormally short tear break-up time. Patients and Methods: This is a prospective comparative non-interventional controlled study in which a total of (180) eyes of (180) patients were divided into (2) groups of (90) patients in each subgroup. Patients with normal eyes (90 patients) without dry-eye syndrome, and those with mild to moderate dry-eye syndrome (90 patients). All patients undergone Pentacam corneal tomography before and after tear substitute instillation. Results: A sequential capturing of Pentacam photos before and after the use of artificial tears was taken and results for keratometry,astigmatic amount and central corneal thickness were observed. A greater variability (highly significant)was recorded among dry eye patients (with short TBUT) than in healthy controls, regarding the keratometric values, astigmatic amount and central corneal thickness after using artificial tears. This study shows the importance of and the relation between TBUT test and the data got by Pentacam. It also shows how beneficial the use of the Pentacam as a diagnostic and a follow up tool in dry eye disease. Conclusion: In our study we emphesize the routine TBUT test prior to keratometric or pachymetric measurements to diagnose and exclude dry eye disease, to avoid any measurement errors, to treat the patient and to save the time for the doctor and patient. In patients with short TBUTT, the keratometric measurements and the astigmatic amount can increase or decrease significantly immediately when using artificial tears in dry eye and this effect could last for 5 minutes or more,before values return to its native measurements. Pachymetric measurements before and after the use of artificial tears could be used as a tool for diagnosis, treatment and follow up in dry eye patients due to the finding that the cornea may be thinned out in dry eye and it could increase significantly with the use of artificial tears.