We checked 190 tonometers every month and repaired faulty ones. Calibration error (CE) frequency reduced from 23% to 0.6% at 1 year. Tonometers needing one or >1 CE repair differed in survival but not in age.
The purpose of this study was to report the outcomes of a comprehensive program to maintain calibration status of the Goldmann applanation tonometer.
This prospective cohort study was carried out at 2 tertiary eye care referral centers. We included 190 slit-lamp mounted Goldmann applanation tonometers (Model AT 900 C/M). Health care providers (error checking and reporting) and clinical engineers (maintenance) participated. The team carried out CE check once a month, and repair of faulty tonometers, if any, within 24 hours. Failure of tonometer was defined as development of unacceptable CE beyond the third repair. The main outcome measures were the frequency of CE and survival function of the tonometer over 1 year.
The median age of the tonometers was 10.7 (range, 0.2 to 25.1) years. The total number of repairs was 86. The proportion (95% confidence interval) of faulty tonometers reduced from 23.1% (17.7, 29.6) in the first month to 0.6% (0.1, 3.3) at 1 year (P<0.01). The median age of the tonometer did not differ between those needing (n=63, 9.4 y) and not needing (n=127, 10.7 y; P=0.24) repair. All tonometers requiring 1 CE repair (n=49, 25.7%) survived until 1 year. The survival of tonometers requiring >1 CE repair (n=14, 7.3%) was 40% at 1 year.
Our in-house program maintained 92.6% tonometers error free. Number of repairs rather than age determined the need for replacement/sending back the tonometer to the manufacturer. Our simple and easy to follow maintenance program has the potential for wide application.
*V S T Glaucoma Center, Dr. Kallam Anji Reddy Campus
†Ophthalmic Engineering Group-Srujana Center for Innovation, L V Prasad Eye Institute, Hyderabad, Telangana
‡Smt. Jadhavbai Nathamal Singhvee Department of Glaucoma, Medical Research Foundation, Sankara Nethralaya, Chennai, Tamil Nadu, India
The pilot data for this study were presented at the Annual Meeting of the Glaucoma Society of India in September 2017. It was the winner of the “Best Paper Award.”
The study has been presented at the annual meeting of the Association for Research in Vision and Ophthalmology (ARVO) at Vancouver, Canada on April 29, 2019.
N.S.C. and A.R. are joint first authors of this manuscript.
Disclosure: The authors declare no conflict of interest.
Reprints: Nikhil S. Choudhari, DNB, Dr. Kallam Anji Reddy Campus, L V Prasad Eye Institute, L V Prasad Marg, Banjara Hills, Hyderabad 500 034, Telangana, India (e-mails: email@example.com, firstname.lastname@example.org).
Received January 10, 2019
Accepted March 24, 2019