Design of an intraocular pressure curve protocol for use in dogs

Abstract

Objectives: To establish an intraocular pressure curve protocol that is safe for corneal health and detects harmful elevations of intraocular pressure outside normal clinic hours. To determine inter-user variability and if repeated measurements affect intraocular pressures. Materials and Methods: Intraocular pressures were measured in dogs with glaucoma using three protocols: Protocol 1 used applanation tonometry every 2 hours over a 24-hour period; Protocols 2 and 3 used applanation or rebound tonometry, respectively, and measured intraocular pressures every 3 hours over a 30-hour period. A total of 60 additional intraocular pressure curves from dogs with glaucoma and 20 from healthy dogs were then analysed for inter-user variability. Results: A total of 128 intraocular pressure curves were determined in 30 dogs. Protocol 1 resulted in one ulcer in five pressure curves, Protocol 2 in one ulcer in 62 pressure curves and Protocol 3 in no ulcers in 61 pressure curves. Elevated intraocular pressures were detected on 61 occasions, of which 26 developed outside normal clinic hours. A total of 61 additional intraocular pressure curves revealed that repeated measurements had no effect on intraocular pressure. Clinical Significance: Protocol 3, using rebound tonometry every 3 hours for 30 hours is safe corneal health and identified elevated intraocular pressures outside normal clinic hours in 12 of 30 (40%) patients that single intraocular pressure measurement during consultation hours would not have identified. Intraocular pressure curves may be recommended for clinical practice and glaucoma studies.