Inter-optometrist variability of IOP measurement for modern tonometers and their agreement with Goldmann Applanation Tonometry

• Published in: Clinical and experimental optometry 2021-07, Vol.104 (5), p.602-610
• Main Authors: Campbell, Peter, Edgar, David F, Shah, Rakhee
• Format: Article
• Language: English
• Subjects: Comparison; Cornea; Eye diseases; Glaucoma; Humans; Intraocular Pressure; Manometry; Medical treatment; Optometrists; Optometry; Reproducibility of Results; Statistical analysis; tonometer; Tonometry, Ocular
• ISSN: 0816-4622; 1444-0938
• DOI: 10.1080/08164622.2021.1878831

Clinical relevance: Accuracy of tonometers is of vital importance in the detection and treatment of glaucoma. Background: This study investigates: agreement in intraocular pressure measurements between three tonometers and Goldmann applanation tonometry (GAT); inter-optometrist agreement for each tonometer; intra-optometrist agreement for GAT; association between central corneal thickness (CCT) and IOP measurements with each tonometer. Methods: IOP was measured using: CT-1P Non-Contact Tonometer (NCT) (Topcon Corporation, Tokyo, Japan), Pulsair IntelliPuff (Keeler Ltd., Windsor, UK) and Icare rebound tonometer (Icare, Helsinki, Finland) by two optometrists in a random order. Two GAT readings were obtained by each optometrist in a randomised masked manner. Mean differences, and 95% limits of agreement (LoA) for each measurement were calculated. CCT was measured by CT-1P pachymeter. Results: Forty-one participants' IOPs were measured. Mean differences (95% LoA) between NCT, Pulsair, Icare compared to GAT for one optometrist were: 0.8 (−5.4 to 6.9) mmHg, −1.7 (−8.2 to 4.8) mmHg, −1.6 (−9.0 to 5.9) mmHg. Mean differences (95% LoA) in inter-optometrist agreement for GAT, NCT, Pulsair and Icare were: 0.3 (−6.7 to 7.3) mmHg, 0.4 (−2.1 to 2.9) mmHg, −0.9 (−3.6 to 1.9) mmHg and −0.2 (−4.9 to 4.5) mmHg, respectively. Mean differences (95% LoA) for intra-optometrist agreement for GAT were 0.2 (4.3 to −4.7) mmHg and 0.1 (3.6 to −3.9) mmHg for each optometrist, respectively. There was a weak positive association between CCT and both GAT (r 2  = 0.11) and NCT (r 2  = 0.12). Conclusion: Pulsair and Icare may measure IOP lower than GAT. Mean differences for inter-optometrist agreement for all tonometers were < 1 mmHg; Pulsair showed a statistically significant difference. Intra-optometrist agreement for GAT was good. IOP measurements taken by two community optometrists are comparable using tonometers used in community practice.