Rectifying calibration error of Goldmann applanation tonometer is easy.
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Date
2014-11
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Abstract
Purpose: Goldmann applanation tonometer (GAT) is the current Gold standard tonometer. However,
its calibration error is common and can go unnoticed in clinics. Its company repair has limitations.
The purpose of this report is to describe a self‑taught technique of rectifying calibration error of GAT.
Materials and Methods: Twenty‑nine slit‑lamp‑mounted Haag‑Streit Goldmann tonometers (Model AT
900 C/M; Haag‑Streit, Switzerland) were included in this cross‑sectional interventional pilot study. The
technique of rectification of calibration error of the tonometer involved cleaning and lubrication of the
instrument followed by alignment of weights when lubrication alone didn’t suffice. We followed the South
East Asia Glaucoma Interest Group’s definition of calibration error tolerance (acceptable GAT calibration
error within ±2, ±3 and ±4 mm Hg at the 0, 20 and 60‑mm Hg testing levels, respectively). Results: Twelve
out of 29 (41.3%) GATs were out of calibration. The range of positive and negative calibration error at the
clinically most important 20‑mm Hg testing level was 0.5 to 20 mm Hg and ‑0.5 to ‑18 mm Hg, respectively.
Cleaning and lubrication alone sufficed to rectify calibration error of 11 (91.6%) faulty instruments. Only
one (8.3%) faulty GAT required alignment of the counter‑weight. Conclusions: Rectification of calibration
error of GAT is possible in‑house. Cleaning and lubrication of GAT can be carried out even by eye care
professionals and may suffice to rectify calibration error in the majority of faulty instruments. Such an
exercise may drastically reduce the downtime of the Gold standard tonometer.
Description
Keywords
Calibration error, calibration, goldmann applanation tonometer
Citation
Choudhari Nikhil S, Moorthy P Krishna,Tungikar Vinod B, Kumar Mohan, George Ronnie, Rao Harsha L, Senthil Sirisha, Vijaya Lingam, Garudadri Chandra Sekhar. Rectifying calibration error of Goldmann applanation tonometer is easy. Indian Journal of Ophthalmology. 2014 Nov ; 62 (11): 1082-1085.