Effects of Hemodialysis on Intraocular Pressure in a University Hospital Located in Midwestern Brazil

This cross-sectional observational study followed the guidelines of the Declaration of Helsinki, and all patients signed an informed consent form approved by the Ethics and Research Committee of the Pontifical Catholic University of Goiás (Pontifícia Universidade Católica de Goiás - PUC-GO). The inclusion criteria were chronic renal patients, who were older than 18 years of age, were part of the hemodialysis program of the Santa Casa de Misericordia de Goiânia (SCMG) hospital, signed the informed consent form and were able to undergo a physical examination. Exclusion criteria were patients on hemodialysis who were not chronic renal patients; patients who refused to participate in the study or could not undergo a physical examination; patients who did not undergo hemodialysis in the week of the study; prior ophthalmic eye disease or surgery; and patients allergic to anesthetic drops or dyes.

Patients were divided into groups according to the days on which they underwent hemodialysis. A total of 39 patients who were on hemodialysis at SCMG for six days in the month of June 2014 were analyzed. The patient's eye fundus was evaluated through direct ophthalmoscopy with a PanOptic device (Welch Allyn). Intraocular pressure was measured with a Kowa HA-2 Perkins applanation tonometer. The tonometry included three measurements in the central region of the cornea before and after hemodialysis. In all patients, the measurements were performed three times on the days when hemodialysis sessions were performed, with 24 hours between each session, and the means of the measurements were obtained. All parameters were measured under prior corneal anesthesia with 0.1% proparacaine and 0.25% fluorescein eye drops.

The variables studied were age, gender, base etiology for CKD, and variations in body weight and IOP before and after hemodialysis. Mean blood pressure (MBP), systolic blood pressure (SBP), diastolic blood pressure (DBP), and ocular perfusion pressure (OPP) were obtained before and after hemodialysis. The following mathematical models were used: MBP = (DBP) + 1/3 (SBP) - (DBP) and OPP = 2/3 (MBP-IOP), as described in the literature (18-20). The data were collected using a form devised for the study from the medical records of the chronic renal patients undergoing hemodialysis at SCMG and registered in the system.

The data were tabulated in a Microsoft© Excel 2007 spreadsheet and analyzed using the Statistical Package for the Social Sciences, version 20 (SPSS, Chicago, IL). The mean, standard deviation, median IOP measurements, blood pressure, and weight were obtained. Data normality was assessed by the Kolmogorov-Smirnov test. The significance of differences between measurements obtained before and after hemodialysis was assessed by the Wilcoxon test. The relationship between IOP and weight was assessed by Pearson's or Spearman's correlation. P-values <0.05 were considered significant.