Intraocular pressure readings obtained through soft contact lenses using four types of tonometer

Figures & data

Table 1 Subject demographics

Parameter	Average	Range
Age, years	21.9±1.1	20–24
Sex, F/M	15/11	–
CCT, µm	536.3±29.2	484–582
Corneal curvature, mm	7.8±0.2	7.5–8.2
Spherical equivalent, D	−4.5±2.7	−8.8–0

Note: The values are presented as the mean ± standard deviation.

Abbreviations: F/M, female/male; CCT, corneal central thickness.

Table 2 Intraocular pressure differences in the subjects wearing soft contact lenses compared to that obtained without contact lenses measured using the Goldmann applanation tonometer

Contact lens power (diopter)	NCT		GAT		RBT		Tono-Pen XL
	Difference (mmHg)	P-value	Difference (mmHg)	P-value	Difference (mmHg)	P-value	Difference (mmHg)	P-value
−5.00	−0.5	0.42	−1.5	0.03	+0.5	0.49	+2.6	<0.01
−0.50	+0.3	0.70	−0.6	0.36	−0.2	0.75	+2.5	<0.01
+5.00	+2.0	<0.01	+2.3	<0.01	+1.1	0.18	+4.8	<0.01

Abbreviations: NCT, non-contact tonometer; GAT, Goldmann applanation tonometer; RBT, iCare rebound tonometer.

Figure 1 Bland–Altman plot showing the relationship between the IOP values of the naked eyes measured using GAT and those obtained while wearing SCLs measured using NCT.

Notes: (A) Wearing −5.00 D SCLs. (B) Wearing −0.50 D SCLs. (C) Wearing +5.00 D SCLs.
Abbreviations: IOP, intraocular pressure; GAT, Goldmann applanation tonometer; SCLs, soft contact lenses; NCT, non-contact tonometer; CL, contact lens; D, diopter.

Figure 2 Bland–Altman plot showing the relationship between the IOP values of the naked eyes and those obtained while wearing SCLs measured using GAT.

Notes: (A) Wearing −5.00 D SCLs. (B) Wearing −0.50 D SCLs. (C) Wearing +5.00 D SCLs.
Abbreviations: IOP, intraocular pressure; GAT, Goldmann applanation tonometer; SCLs, soft contact lenses; CL, contact lens; D, diopter.

Figure 3 Bland–Altman plot showing the relationship between the IOP values of the naked eyes measured using GAT and those obtained while wearing SCLs measured using RBT.

Notes: (A) Wearing −5.00 D SCLs. (B) Wearing −0.50 D SCLs. (C) Wearing +5.00 D SCLs.
Abbreviations: IOP, intraocular pressure; GAT, Goldmann applanation tonometer; SCLs, soft contact lenses; CL, contact lens; D, diopter; RBT, iCare rebound tonometer.

Figure 4 Bland–Altman plot showing the relationship between the IOP values of the naked eyes measured using GAT and those obtained while wearing SCLs measured using the Tono-Pen XL.

Notes: (A) Wearing −5.00 D SCLs. (B) Wearing −0.50 D SCLs. (C) Wearing +5.00 D SCLs.
Abbreviations: IOP, intraocular pressure; GAT, Goldmann applanation tonometer; SCLs, soft contact lenses; CL, contact lens; D, diopter.

Table 3 Results of the regression analysis of the intraocular pressure values of the naked eyes measured using the Goldmann applanation tonometer, and those obtained while wearing contact lenses measured with various tonometers

Tonometer	r value	P-value	Regression equation
NCT	0.78	<0.0001	y=0.72x+4.47
NCT CL −5.00 D	0.60	<0.0001	y=0.59x+5.10
NCT CL −0.50 D	0.44	0.0002	y=0.64x+5.22
NCT CL +5.00 D	0.52	<0.0001	y=0.70x+6.08
GAT CL −5.00 D	0.36	0.0013	y=0.56x+4.55
GAT CL −0.50 D	0.27	0.0060	y=0.41x+7.54
GAT CL +5.00 D	0.34	0.0017	y=0.65x+7.15
RBT	0.60	<0.0001	y=1.00x+1.47
RBT CL −5.00 D	0.46	0.0001	y=0.73x+4.20
RBT CL −0.50 D	0.44	0.0002	y=0.74x+3.35
RBT CL +5.00 D	0.32	0.0028	y=0.68x+5.52
Tono-Pen XL	0.51	<0.0001	y=0.59x+9.54
Tono-Pen XL CL −5.00 D	0.32	0.0027	y=0.37x+11.3
Tono-Pen XL CL −0.50 D	0.09	0.1288	y=0.23x+13.1
Tono-Pen XL CL +5.00 D	0.35	0.0014	y=0.71x+8.78

Abbreviations: NCT, non-contact tonometer; GAT, Goldmann applanation tonometer; RBT, iCare rebound tonometer; CL, contact lens; D, diopter.