Comparison of IOP Measurement by Goldmann Applanation Tonometer, ICare Rebound Tonometer, and Tono-Pen in Keratoconus Patients after MyoRing Implantation.

Mahmoud Rateb,Asaad Noor El Din,Mohamed Nagy Elmohamady,Zeiad Eldaly,Mahmoud Abdel-Radi

doi:10.1155/2019/1964107

Mahmoud Rateb, Asaad Noor El Din + Show 3 more

Open Access

https://doi.org/10.1155/2019/1964107

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Abstract

Purpose To evaluate the different IOP readings by Goldmann applanation tonometer (GAT), ICare rebound tonometer, and Tono-Pen in keratoconus patients after MyoRing implantation. To assess the influence of central corneal thickness (CCT) and thinnest corneal location (TCL) on IOP measurements by different tonometers. Setting Prospective observational study was conducted in two private centers in Egypt from February 2015 to November 2016. Methods Seventeen eyes of 10 patients suffering from keratoconus and who underwent MyoRing implantation were recruited. All subjects underwent GAT, ICare, and Tono-Pen IOP measurements in random order. Central corneal thickness and thinnest corneal location were assessed by Pentacam. Difference in mean in IOP readings was assessed by T-test. Correlation between each pair of devices was evaluated by Pearson correlation coefficient. The Bland–Altman analysis was used to assess intertonometer agreement. Results Seventeen eyes (10 patients) were evaluated. The mean IOP reading was 13.9 ± 3.68, 12.41 ± 2.87, and 14.29 ± 1.31 mmHg in GAT, ICare, and Tono-Pen group, respectively. There was a significant difference between IOP readings by GAT/ICare and Tono-Pen/ICare (p value: 0.032 and 0.002, respectively) with no significant difference between GAT/Tono-Pen (p value: 0.554). Mean difference in IOP measurements between GAT/ICare was 1.49 ± 2.61 mmHg, Tono-Pen/ICare was 1.89 ± 2.15 mmHg, and GAT/Tono-Pen was −0.39 ± 2.59 mmHg. There was no significant correlation between the difference in IOP readings among any pair of devices and CCC or TCL. The Bland–Altman analysis showed a reasonable agreement between any pair of tonometers.

Highlights

Keratoconus (KC) is a progressive ectatic corneal disease characterized by corneal thinning associated with ametropia, mostly irregular astigmatism and myopia [1]
It usually occurs in the teenagers and affects both males and females [2]. e rigid gas permeable (RGP) contact lenses have been used to regularize the corneal surface in those patients, but the implantation of intracorneal ring segments (ICRS) is gaining more popularity to achieve that purpose with resultant improved patient’s visual acuity and quality [3]
intraocular pressure (IOP) measurement is markedly affected by the central corneal thickness (CCT) and corneal curvature (CC) which show marked variation in patients with keratoconus and after implantation of corneal rings. ough Goldmann applanation tonometry (GAT) is the gold standard for IOP measurement by many ophthalmologists, its accuracy is questionable in such patients [9,10,11]

Summary

Introduction

Keratoconus (KC) is a progressive ectatic corneal disease characterized by corneal thinning associated with ametropia, mostly irregular astigmatism and myopia [1]. We compared IOP readings recorded by three types of tonometers (Goldmann tonometer, Tono-Pen, and Impact rebound tonometer) in keratoconus patients who underwent MyoRing implantation. E Tono-Pen tonometer is thought to be more accurate in irregular corneas as it used a smaller area of the cornea compared to GAT and depends on an electronic endpoint; its readings are affected with the corneal thickness [17, 18].

Results

Conclusion