- Email: [email protected]
Rebound tonometry measurements over extended-wear bandage contact lenses
Contact Lens and Anterior Eye xxx (xxxx) xxx–xxx
Contents lists available at ScienceDirect
Contact Lens and Anterior Eye journal homepage: www.elsevier.com/locate/clae
Rebound tonometry measurements over extended-wear bandage contact lenses Corrina P. Azarcon*, Romeo C. dela Cruz University of the Philippines - Philippine General Hospital, Manila, Philippines
A R T I C LE I N FO
A B S T R A C T
Keywords: Rebound tonometry Intraocular pressure Bandage contact lens Lotrafilcon A contact lens iCare PRO Oxygen transmissibility
Background: The aim of this study was to assess the validity of rebound tonometry measurements obtained over eyes wearing extended-wear bandage contact lenses with the highest oxygen transmissibility (Dk/t) value of 175 @ -3.00 D. Methods: A total of 151 normal eyes were included in this prospective pretest-posttest study. A rebound tonometer (iCare PRO) was used to collect intraocular pressure readings from “naked” eyes (eyes without contact lenses) and the same eyes wearing extended-wear lotrafilcon A bandage contact lenses (Alcon Air Optix Night & Day Aqua Contact Lenses). The mean pre- and post-application values were pooled and compared using the paired t-test. Results: The application of extended-wear lotrafilcon A contact lenses over normal eyes did not cause a statistically significant change in the intraocular pressure measurements obtained using an iCare PRO tonometer (13.74 ± 2.15 mm Hg vs. 13.77 ± 2.26 mm Hg, p-value = 0.6506). Conclusion: Based on this study conducted on normal eyes, the removal of extended-wear bandage contact lenses is not necessary when taking intraocular pressure measurements using the iCare PRO rebound tonometer.
1. Introduction Therapeutic bandage contact lenses are used to promote corneal epithelial healing and to diminish pain signals generated from the ocular surface. [1] It has been found to be effective in alleviating ocular symptoms among patients with dry eye disease, bullous keratopathy, corneal ulcers, and corneal lacerations [1,2]. It has also been used to relieve post-operative discomfort among patients who underwent cataract surgery [1], corneal transplantation [2], photorefractive keratectomy [3], amniotic membrane transplantation, and limbal autograft transplantation [4]. In certain cases, the extended use of these therapeutic contact lenses is warranted [5]. Kanpolat and Ucakhan demonstrated the safety and effectiveness of extended-wear contact lenses with oxygen transmissibility (Dk/t) value of 175@ -3.00 D. The infrequent need for replacement of these contact lenses decreases the risk for epithelial trauma, pain, and infection among contact lens users [4]. Routine intraocular pressure monitoring may be necessary for patients who are for regular follow-up examination. Among patients wearing soft contact lenses, concurrent need for accurate intraocular pressure monitoring poses a problem since the presence of a contact lens is known to alter pressure readings obtained using the Goldmann Applanation Tonometer [6]. Contact lens manipulation prior to or ⁎
during intraocular pressure measurement has also been found to cause significant changes in intraocular pressure readings [7]. The risk for infection is also theoretically increased. This has led authors to study various methods in obtaining intraocular pressure measurements over eyes wearing bandage contact lenses. Goldmann applanation tonometry remains to be the gold standard in measuring intraocular pressure over the corneal surface [8], however, it is not ideal for contact-lens wearers since fluorescein dye tends to stain soft contact lenses. Hence, removal of the lenses would be necessary prior to intraocular pressure measurement using this method. Other instruments that allow intraocular pressure measurement over contact lenses are available. The utility of the non-contact air-puff tonometer and the Tono-Pen in measuring intraocular pressure among contact lens wearers has been well documented by several authors [9–15]. The use of rebound tonometry to measure intraocular pressure over soft contact lenses has also been described [16,17]. The aim of this study was to determine if rebound tonometry measurements obtained from eyes wearing extended-wear bandage contact lenses would yield valid measurements which are similar with those collected from “naked” eyes (eyes without contact lenses). The Alcon AirOptix Night & Day Aqua Contact Lens was selected since it has the highest Dk/t value at 175 @ -3.00 D, allowing it to be worn for up to
Corresponding author. E-mail address: [email protected] (C.P. Azarcon).
https://doi.org/10.1016/j.clae.2020.02.019 Received 22 November 2019; Received in revised form 24 February 2020; Accepted 25 February 2020 1367-0484/ © 2020 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Please cite this article as: Corrina P. Azarcon and Romeo C. dela Cruz, Contact Lens and Anterior Eye, https://doi.org/10.1016/j.clae.2020.02.019
Contact Lens and Anterior Eye xxx (xxxx) xxx–xxx
C.P. Azarcon and R.C. dela Cruz
pressure of the eye wearing the contact lens was measured after an equilibration period of 15 min from the time that the contact lens was placed. The means of the intraocular pressures pre-and post-contact lens application were determined. The values obtained from the “naked” eyes were compared to those obtained from the same set of eyes wearing contact lenses. The paired t-test was used to determine the degree of significance between the two data sets.
Nomenclature Units of Measurement mm Mg
millimeters mercury
Abbreviations Dk/t
oxygen transmissibility
3. Results A total of 151 adults with ages ranging from 18–59 years old were recruited in the study. A larger proportion of the participants were females (57.6 %). The right eye was tested in 75 participants and the left eye was tested in 76 participants. Both pre- and post-contact lens application intraocular pressure measurements were normally distributed on histogram and formal test (Fig. 2). The ranges of the pre- and postcontact lens application measurements were 8.1–19.6 mm Hg and 6.3–20.3 mm Hg, respectively. The mean pre- and post-contact lens application IOP were 13.77 + 2.26 mm Hg and 13.74 + 2.15 mm Hg. The p-value of 0.6506 showed no statistically significant difference between the two data sets.
thirty days. This study was done on normal eyes. 2. Methods This a prospective single-group pretest-posttest study approved by a local Research Ethics Board. It was conducted in full compliance with the tenets of the Declaration of Helsinki. Written informed consent forms were obtained from each volunteer prior to their participation. Data forms containing patient information were made accessible only to the primary researcher and the research assistant. Records containing personal participant data were anonymized before being transferred to a secure digital database. A total of 151 individuals were recruited from the Ophthalmology department of a tertiary hospital in the Philippines. Participants were required to satisfy the following inclusion criteria: 1. they must be 18–59 years old, 2. they must have at least one eye with normal ocular surface and anterior segment anatomy, 3. their ocular media should be sufficiently clear to allow adequate evaluation of the optic disc and the posterior pole, and 4. the average intraocular pressure reading of both eyes should not be greater than 21 mm Hg. Participants who had clinical findings that warranted the diagnosis of glaucoma or glaucoma suspect on either eye were excluded. Those who were taking any medications that have documented effects on the intraocular pressure were likewise excluded. Only one eye, which satisfied the characteristics described in the inclusion criteria, was tested for each volunteer. The examination proper consisted of six parts, as shown in the schematic diagram (Fig. 1). Slit lamp examination was performed to examine the ocular surface and the anterior segment anatomy before and after contact lens application. Posterior pole and optic disc evaluation were conducted using a fundus lens. Intraocular pressure measurements were determined using an iCare PRO tonometer. Bandage contact lenses (Alcon AirOptix Night & Day Aqua Contact Lens) with Dk/t of 175 @ -3.00 D were used. The schematic diagram of the procedure is shown in Fig. 1. Intraocular pressure readings were obtained in triplicates for each eye. Measurements were recorded only if the participant was able to sustain primary gaze without straining, moving, and squinting. The intraocular
4. Discussion The therapeutic use of hydrogel silicone contact lenses has been found to hasten the healing of the corneal surface, improve visual acuity, diminish surface pain after ocular surgery, and reduce the risk for postoperative infection. The use of these lenses facilitates earlier visual rehabilitation and improves patient comfort [3]. One of the problems encountered with the extended use of soft contact lenses is the risk for corneal hypoxia. Corneal hypoxia leads to the development of corneal neovascularization among contact-lens wearers. Patients who are at higher risk for these complications include those who sleep with contact lenses on, those who use contact lenses with low Dk/t values, and those who use therapeutic contact lenses [18]. Over the years, contact lens manufacturers have developed contact lenses with high oxygen transmissibility that allows sufficient oxygen to reach the corneal surface. At present, the highest oxygen transmissibility value achieved is with lotrafilcon A contact lenses with Dk/t value of 175 @ -3.00 D. During a period of continuous contact lens wear, the measurement of intraocular pressure is often considered by ophthalmologists to be unreliable. The importance of accurate intraocular pressure measurement cannot be overemphasized especially among post-operative patients and glaucoma patients [5]. Previous studies have compared intraocular pressure measurements obtained over soft contact lenses using different kinds of tonometers. Using the Goldmann applanation tonometer as a standard, Scibilia et al. used the Tono-Pen and
Fig. 1. Schematic diagram of the pretest-posttest study. 2
Contact Lens and Anterior Eye xxx (xxxx) xxx–xxx
C.P. Azarcon and R.C. dela Cruz
Fig. 2. Frequency of intraocular pressure (IOP) values taken from a. the “naked” eyes and b. the eyes with contact lens. Both data sets followed normal distribution.
by rebound tonometry and the Goldmann applanation tonometer was not significant [20]. The iCare model used in these published studies (iCare TA01i) was an older version released by iCare Finland in 2003. Based on the manufacturer website, the more recent model (iCare PRO) has an enhanced measurement algorithm that provides more accurate measurements [21]. The findings of this study indicate that the iCare PRO, when used over lotrafilcon A contact lenses, yields measurements that are more similar to the “naked” values. Thus, removal of this type of contact lens is not needed prior to intraocular pressure measurement using the iCare PRO tonometer.
pneumatonometer to determine intraocular pressure measurements over three brands of contact lenses: ACUVUE, 04, and Permalens. The authors found that intraocular pressure measurements using the two instruments over the three types of therapeutic contact lenses were reliable [14]. In a more recent study, Takenaka et al. compared the accuracy and reliability of intraocular pressure measurements taken over hydrogel ACUVUE contact lenses using four different types of tonometers: non-contact tonometer, Goldmann applanation tonometer, iCare rebound tonometer, and Tono-Pen XL. Measurements were made over three selected powers: -5.00 D, -0.50 D, and +5.00 D. Intraocular pressure readings over +5.00 D lenses were higher than values obtained from the “naked” eyes using the Tono-Pen XL and non-contact tonometer. Rebound tonometry measurements recorded from “naked” eyes and eyes wearing contact lenses were similar across the three lens powers. It was concluded that intraocular pressure measurements using rebound tonometry and non-contact tonometry over hydrogel soft contact lenses were reliable [17]. Anton et al. compared the intraocular pressure values obtained using air puff tonometry and rebound tonometry over a Pure Vision 2 HD (balafilcon A) soft contact lens. Results showed that the values obtained using both methods were accurate enough for clinical use [5]. In a study conducted by Zeri et al., intraocular pressure measurements were obtained over disposable hydrogel (etafilcon A) and silicon hydrogel (senofilcon A) contact lenses using rebound tonometry. The study tested lenses with powers of +2.00 D, −2.00 D, and −6.00 D. It was found that the values were reliable for silicone hydrogel contact lenses, however, readings over the hydrogel contact lenses tended to be lower than the actual values. The study concluded that the difference was not statistically and clinically significant [16]. The studies cited above show that the difference of the intraocular pressure measurements obtained over “naked” eyes to those obtained over eyes wearing contact lenses mainly depends on the following parameters: kind and composition of contact lens, the power of the contact lens, and the kind of tonometer being used. This is the first study with a large sample size to examine the use of the iCare PRO rebound tonometer over lotrafilcon A silicon hydrogen contact lenses. No statistically and clinically significant difference was seen between the values obtained before and after contact lens application. An earlier study conducted by García-Resúa et al. compared measurements obtained using iCare, Tonopen, and Perkins on “naked” eyes and eyes wearing lotrafilcon A contact lenses. It was found that iCare tended to overestimate the intraocular pressure values by 1 mm Hg (p < 0.001), whereas no significant difference was observed using Perkins and Tonopen XL [19]. Nacaroglu et al. also published a study that evaluated intraocular pressure measurements over contact lenses in comparison to Goldmann applanation tonometry. It was found that the mean of the measurements taken over contact lenses was higher than measurements taken without contact lenses. The difference of the measurements taken
5. Conclusion Rebound tonometry measurements obtained over extended-use lotrafilcon A bandage contact lenses (Alcon Air Optix Night & Day Aqua Contact Lenses) using the iCare PRO tonometer are statistically similar to those obtained from “naked eyes.” The removal of this type of soft contact lens before intraocular pressure measurement is not necessary when using this type of rebound tonometer. A major limitation of this study is that it was conducted only on normal eyes. Future studies must be done on patients with abnormal ocular surface and intraocular pressure to assess the applicability of the results to these populations. Funding The contact lenses were sponsored by Alcon Research, Limited. The iCare probes were provided by Medilight, Incorporated. Disclaimer The sponsors had no role in the design or conduct of this research. Ethics approval This study was approved by an Ethics Board. The study was conducted in accordance with the tenets of the Declaration of Helsinki. Provenance and peer review Not commissioned; externally peer reviewed. Data availability statement Data are available on request. Declaration of Competing Interest None declared. 3
Contact Lens and Anterior Eye xxx (xxxx) xxx–xxx
C.P. Azarcon and R.C. dela Cruz
References
(January (1)) (1990) 62–65, https://doi.org/10.1016/s0002-9394(14)75580-1. [11] P. Schollmayer, M. Hawlina, Effect of soft contact lenses on the measurement of intraocular pressure with non-contact pneumotonometry, Klin Monatsbl Augenheilkd 220 (December (12)) (2003) 840–842, https://doi.org/10.1055/s2003-812564. [12] S. Patel, G. Stevenson, Influence of lens material and intra-ocular pressure on the outcome of non-contact tonometry over soft contact lenses, Contact Lens Anterior Eye 32 (April (2)) (2009) 68–72, https://doi.org/10.1016/j.clae.2008.08.005. [13] Y.C. Liu, J.Y. Huang, I.J. Wang, F.R. Hu, Y.C. Hou, Intraocular pressure measurement with the noncontact tonometer through soft contact lenses, J Glaucoma 20 (March (3)) (2011) 179–182, https://doi.org/10.1097/IJG.0b013e3181aae90c. [14] G.D. Scibilia, W.H. Ehlers, P.C. Donshik, The effects of therapeutic contact lenses on intraocular pressure measurement, CLAO J 22 (October (4)) (1996) 262–265 Cited in: PubMed; PMID: 8906384. [15] R. Sugimoto-Takeuchi, R. Yamamoto, Y. Kuwayama, S. Kinoshita, Effect of intraocular pressure measurement through therapeutic soft contact lenses by noncontact tonometer, Nippon Ganka Gakkai Zasshi 95 (September (9)) (1991) 869–872 Cited in PubMed; PMID: 1796769. [16] F. Zeri, M. De Cusatis, L. Lupelli, P.G. Swann, The measurement of intraocular pressure over soft contact lenses by rebound tonometry, J Optom 9 (July-September (3)) (2016) 182–188, https://doi.org/10.1016/j.optom.2015.09.001. [17] J. Takenaka, E. Kunihara, U. Rimayanti, J. Tanaka, M. Kneko, Y. Kiuchi, Intraocular pressure readings obtained through soft contact lenses using four types of tonometer, Clin Ophthalmol 9 (October) (2015) 1875–1881, https://doi.org/10.2147/ OPTH.S84953 eCollection 2015. [18] K.K. Yeung, H.J. Yang, A.L. Nguyen, B.A. Weissman, Critical contact lens oxygen transmissibility and tear lens oxygen tension to preclude corneal neovascularization, Eye Contact Lens 44 (September (Supl. 1)) (2018) S291–S295. [19] C. Garcia-Resua, S. Garcia-Montero, H. Pena-Verdeal, J. Gilino, et al., Effect of lotrafilcon A silicone hydrogel contact lens on intraocular pressure measurement, Optom Rep 4 (June) (2014) 1846, https://doi.org/10.4081/optometry.2014.1846 10.1097/ICL.0000000000000412. [20] S.A. Nacaroglu, E.S. Un, M.G. Ersoz, Y. Tasci, Intraocular pressure measurement over soft contact lens by rebound tonometer: a comparative study, Int J Ophthalmol 8 (June (3)) (2015) 540–543, https://doi.org/10.3980/j.issn.2222-3959.2015.03. 18 eCollection 2015. [21] Icare, Icare® PRO tonometer [Internet], Available from: Icare, Oy (Finland), 2015https://www.icaretonometer.com/products/icare-pro/.
[1] D.N. Shi, H. Song, T. Ding, W.Q. Qui, W. Wang, Evaluation of the safety and efficacy of therapeutic bandage contact lenses on post-cataract surgery patients, Int J Ophthalmol 11 (February (2)) (2018) 230–234, https://doi.org/10.18240/ijo.2018. 02.08. eCollection 2018. [2] J. Shimazaki, C. Shigeyasu, Y. Saijo-Ban, M. Dogru, S. Den, Effectiveness of bandage contact lens application in corneal epithelialization and pain alleviation following corneal transplantation; prospective, randomized clinical trial, BMC Ophthalmol 16 (October (1)) (2016) 174, https://doi.org/10.1186/s12886-016-0346-6. [3] J.M. Sanchez-Gonzales, I. Lopez-Izuierdo, B. Gargallo-Martinez, C. De-Hita Cantalejo, M.J. Bautista-Llamas, Bandage contact lens use after photorefractive keratectomy, J Cataract Refract Surg 45 (August (8)) (2019) 1183–1190, https:// doi.org/10.1016/j.jcrs.2019.02.045. [4] A. Kanpolat, O.O. Ucakhan, Therapeutic use of Focus Night & Day contact lenses, Cornea 22 (November (8)) (2003) 726–734, https://doi.org/10.1097/00003226200311000-00004. [5] A. Anton, M. Neuberger, D. Bohringer, J.F. Jordan, Comparative measurement of intraocular pressure by Icare tonometry and Airpuff tonometry in healthy subjects and patients wearing therapeutic soft contact lenses, Graefes Arch Clin Exp Ophthalmol 251 (July (7)) (2013) 1791–1795, https://doi.org/10.1007/s00417013-2329-0. [6] M. Mahjoob, A. Azimi, H. Momeni-Moghadam, M. Mohamadian, R. Yousofi, The effect of various contact lenses on intraocular pressure measurement by Goldmann Tonometer, ZJRMS 16 (6) (2014) 33–35 [cited 2019 Jul 13], Available from: http://zjrms.ir/article-1-1670-fa.pdf. [7] J.A. Khan, C.E. Graham, Effect of contact lens removal or displacement on intraocular pressure, Arch Ophthalmol 109 (June (6)) (1991) 825–828, https://doi. org/10.1001/archopht.1991.01080060089031. [8] K.J. Patel, S.P. Jain, P.R. Kapadia, N.V. Patel, S. Patel, V. Patel, Can higher end tonometers be used interchangeably in routine clinical practice? Indian J Ophthalmol 64 (February (2)) (2016) 132–135, https://doi.org/10.4103/03014738.179723. [9] J.B. Rubenstein, T.A. Deutsch, Pneumatotonometry through bandage contact lenses, Arch Ophthalmol 103 (November (11)) (1985) 1660–1661, https://doi.org/ 10.1001/archopht.1985.01050110054023. [10] W.C. Panek, W.A. Boothe, D.A. Lee, E. Zemplenyi, T.H. Pettit, Intraocular pressure measurement with the Tono-Pen through soft contact lenses, Am J Ophthalmol 109
4
Contents lists available at ScienceDirect
Contact Lens and Anterior Eye journal homepage: www.elsevier.com/locate/clae
Rebound tonometry measurements over extended-wear bandage contact lenses Corrina P. Azarcon*, Romeo C. dela Cruz University of the Philippines - Philippine General Hospital, Manila, Philippines
A R T I C LE I N FO
A B S T R A C T
Keywords: Rebound tonometry Intraocular pressure Bandage contact lens Lotrafilcon A contact lens iCare PRO Oxygen transmissibility
Background: The aim of this study was to assess the validity of rebound tonometry measurements obtained over eyes wearing extended-wear bandage contact lenses with the highest oxygen transmissibility (Dk/t) value of 175 @ -3.00 D. Methods: A total of 151 normal eyes were included in this prospective pretest-posttest study. A rebound tonometer (iCare PRO) was used to collect intraocular pressure readings from “naked” eyes (eyes without contact lenses) and the same eyes wearing extended-wear lotrafilcon A bandage contact lenses (Alcon Air Optix Night & Day Aqua Contact Lenses). The mean pre- and post-application values were pooled and compared using the paired t-test. Results: The application of extended-wear lotrafilcon A contact lenses over normal eyes did not cause a statistically significant change in the intraocular pressure measurements obtained using an iCare PRO tonometer (13.74 ± 2.15 mm Hg vs. 13.77 ± 2.26 mm Hg, p-value = 0.6506). Conclusion: Based on this study conducted on normal eyes, the removal of extended-wear bandage contact lenses is not necessary when taking intraocular pressure measurements using the iCare PRO rebound tonometer.
1. Introduction Therapeutic bandage contact lenses are used to promote corneal epithelial healing and to diminish pain signals generated from the ocular surface. [1] It has been found to be effective in alleviating ocular symptoms among patients with dry eye disease, bullous keratopathy, corneal ulcers, and corneal lacerations [1,2]. It has also been used to relieve post-operative discomfort among patients who underwent cataract surgery [1], corneal transplantation [2], photorefractive keratectomy [3], amniotic membrane transplantation, and limbal autograft transplantation [4]. In certain cases, the extended use of these therapeutic contact lenses is warranted [5]. Kanpolat and Ucakhan demonstrated the safety and effectiveness of extended-wear contact lenses with oxygen transmissibility (Dk/t) value of 175@ -3.00 D. The infrequent need for replacement of these contact lenses decreases the risk for epithelial trauma, pain, and infection among contact lens users [4]. Routine intraocular pressure monitoring may be necessary for patients who are for regular follow-up examination. Among patients wearing soft contact lenses, concurrent need for accurate intraocular pressure monitoring poses a problem since the presence of a contact lens is known to alter pressure readings obtained using the Goldmann Applanation Tonometer [6]. Contact lens manipulation prior to or ⁎
during intraocular pressure measurement has also been found to cause significant changes in intraocular pressure readings [7]. The risk for infection is also theoretically increased. This has led authors to study various methods in obtaining intraocular pressure measurements over eyes wearing bandage contact lenses. Goldmann applanation tonometry remains to be the gold standard in measuring intraocular pressure over the corneal surface [8], however, it is not ideal for contact-lens wearers since fluorescein dye tends to stain soft contact lenses. Hence, removal of the lenses would be necessary prior to intraocular pressure measurement using this method. Other instruments that allow intraocular pressure measurement over contact lenses are available. The utility of the non-contact air-puff tonometer and the Tono-Pen in measuring intraocular pressure among contact lens wearers has been well documented by several authors [9–15]. The use of rebound tonometry to measure intraocular pressure over soft contact lenses has also been described [16,17]. The aim of this study was to determine if rebound tonometry measurements obtained from eyes wearing extended-wear bandage contact lenses would yield valid measurements which are similar with those collected from “naked” eyes (eyes without contact lenses). The Alcon AirOptix Night & Day Aqua Contact Lens was selected since it has the highest Dk/t value at 175 @ -3.00 D, allowing it to be worn for up to
Corresponding author. E-mail address: [email protected] (C.P. Azarcon).
https://doi.org/10.1016/j.clae.2020.02.019 Received 22 November 2019; Received in revised form 24 February 2020; Accepted 25 February 2020 1367-0484/ © 2020 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Please cite this article as: Corrina P. Azarcon and Romeo C. dela Cruz, Contact Lens and Anterior Eye, https://doi.org/10.1016/j.clae.2020.02.019
Contact Lens and Anterior Eye xxx (xxxx) xxx–xxx
C.P. Azarcon and R.C. dela Cruz
pressure of the eye wearing the contact lens was measured after an equilibration period of 15 min from the time that the contact lens was placed. The means of the intraocular pressures pre-and post-contact lens application were determined. The values obtained from the “naked” eyes were compared to those obtained from the same set of eyes wearing contact lenses. The paired t-test was used to determine the degree of significance between the two data sets.
Nomenclature Units of Measurement mm Mg
millimeters mercury
Abbreviations Dk/t
oxygen transmissibility
3. Results A total of 151 adults with ages ranging from 18–59 years old were recruited in the study. A larger proportion of the participants were females (57.6 %). The right eye was tested in 75 participants and the left eye was tested in 76 participants. Both pre- and post-contact lens application intraocular pressure measurements were normally distributed on histogram and formal test (Fig. 2). The ranges of the pre- and postcontact lens application measurements were 8.1–19.6 mm Hg and 6.3–20.3 mm Hg, respectively. The mean pre- and post-contact lens application IOP were 13.77 + 2.26 mm Hg and 13.74 + 2.15 mm Hg. The p-value of 0.6506 showed no statistically significant difference between the two data sets.
thirty days. This study was done on normal eyes. 2. Methods This a prospective single-group pretest-posttest study approved by a local Research Ethics Board. It was conducted in full compliance with the tenets of the Declaration of Helsinki. Written informed consent forms were obtained from each volunteer prior to their participation. Data forms containing patient information were made accessible only to the primary researcher and the research assistant. Records containing personal participant data were anonymized before being transferred to a secure digital database. A total of 151 individuals were recruited from the Ophthalmology department of a tertiary hospital in the Philippines. Participants were required to satisfy the following inclusion criteria: 1. they must be 18–59 years old, 2. they must have at least one eye with normal ocular surface and anterior segment anatomy, 3. their ocular media should be sufficiently clear to allow adequate evaluation of the optic disc and the posterior pole, and 4. the average intraocular pressure reading of both eyes should not be greater than 21 mm Hg. Participants who had clinical findings that warranted the diagnosis of glaucoma or glaucoma suspect on either eye were excluded. Those who were taking any medications that have documented effects on the intraocular pressure were likewise excluded. Only one eye, which satisfied the characteristics described in the inclusion criteria, was tested for each volunteer. The examination proper consisted of six parts, as shown in the schematic diagram (Fig. 1). Slit lamp examination was performed to examine the ocular surface and the anterior segment anatomy before and after contact lens application. Posterior pole and optic disc evaluation were conducted using a fundus lens. Intraocular pressure measurements were determined using an iCare PRO tonometer. Bandage contact lenses (Alcon AirOptix Night & Day Aqua Contact Lens) with Dk/t of 175 @ -3.00 D were used. The schematic diagram of the procedure is shown in Fig. 1. Intraocular pressure readings were obtained in triplicates for each eye. Measurements were recorded only if the participant was able to sustain primary gaze without straining, moving, and squinting. The intraocular
4. Discussion The therapeutic use of hydrogel silicone contact lenses has been found to hasten the healing of the corneal surface, improve visual acuity, diminish surface pain after ocular surgery, and reduce the risk for postoperative infection. The use of these lenses facilitates earlier visual rehabilitation and improves patient comfort [3]. One of the problems encountered with the extended use of soft contact lenses is the risk for corneal hypoxia. Corneal hypoxia leads to the development of corneal neovascularization among contact-lens wearers. Patients who are at higher risk for these complications include those who sleep with contact lenses on, those who use contact lenses with low Dk/t values, and those who use therapeutic contact lenses [18]. Over the years, contact lens manufacturers have developed contact lenses with high oxygen transmissibility that allows sufficient oxygen to reach the corneal surface. At present, the highest oxygen transmissibility value achieved is with lotrafilcon A contact lenses with Dk/t value of 175 @ -3.00 D. During a period of continuous contact lens wear, the measurement of intraocular pressure is often considered by ophthalmologists to be unreliable. The importance of accurate intraocular pressure measurement cannot be overemphasized especially among post-operative patients and glaucoma patients [5]. Previous studies have compared intraocular pressure measurements obtained over soft contact lenses using different kinds of tonometers. Using the Goldmann applanation tonometer as a standard, Scibilia et al. used the Tono-Pen and
Fig. 1. Schematic diagram of the pretest-posttest study. 2
Contact Lens and Anterior Eye xxx (xxxx) xxx–xxx
C.P. Azarcon and R.C. dela Cruz
Fig. 2. Frequency of intraocular pressure (IOP) values taken from a. the “naked” eyes and b. the eyes with contact lens. Both data sets followed normal distribution.
by rebound tonometry and the Goldmann applanation tonometer was not significant [20]. The iCare model used in these published studies (iCare TA01i) was an older version released by iCare Finland in 2003. Based on the manufacturer website, the more recent model (iCare PRO) has an enhanced measurement algorithm that provides more accurate measurements [21]. The findings of this study indicate that the iCare PRO, when used over lotrafilcon A contact lenses, yields measurements that are more similar to the “naked” values. Thus, removal of this type of contact lens is not needed prior to intraocular pressure measurement using the iCare PRO tonometer.
pneumatonometer to determine intraocular pressure measurements over three brands of contact lenses: ACUVUE, 04, and Permalens. The authors found that intraocular pressure measurements using the two instruments over the three types of therapeutic contact lenses were reliable [14]. In a more recent study, Takenaka et al. compared the accuracy and reliability of intraocular pressure measurements taken over hydrogel ACUVUE contact lenses using four different types of tonometers: non-contact tonometer, Goldmann applanation tonometer, iCare rebound tonometer, and Tono-Pen XL. Measurements were made over three selected powers: -5.00 D, -0.50 D, and +5.00 D. Intraocular pressure readings over +5.00 D lenses were higher than values obtained from the “naked” eyes using the Tono-Pen XL and non-contact tonometer. Rebound tonometry measurements recorded from “naked” eyes and eyes wearing contact lenses were similar across the three lens powers. It was concluded that intraocular pressure measurements using rebound tonometry and non-contact tonometry over hydrogel soft contact lenses were reliable [17]. Anton et al. compared the intraocular pressure values obtained using air puff tonometry and rebound tonometry over a Pure Vision 2 HD (balafilcon A) soft contact lens. Results showed that the values obtained using both methods were accurate enough for clinical use [5]. In a study conducted by Zeri et al., intraocular pressure measurements were obtained over disposable hydrogel (etafilcon A) and silicon hydrogel (senofilcon A) contact lenses using rebound tonometry. The study tested lenses with powers of +2.00 D, −2.00 D, and −6.00 D. It was found that the values were reliable for silicone hydrogel contact lenses, however, readings over the hydrogel contact lenses tended to be lower than the actual values. The study concluded that the difference was not statistically and clinically significant [16]. The studies cited above show that the difference of the intraocular pressure measurements obtained over “naked” eyes to those obtained over eyes wearing contact lenses mainly depends on the following parameters: kind and composition of contact lens, the power of the contact lens, and the kind of tonometer being used. This is the first study with a large sample size to examine the use of the iCare PRO rebound tonometer over lotrafilcon A silicon hydrogen contact lenses. No statistically and clinically significant difference was seen between the values obtained before and after contact lens application. An earlier study conducted by García-Resúa et al. compared measurements obtained using iCare, Tonopen, and Perkins on “naked” eyes and eyes wearing lotrafilcon A contact lenses. It was found that iCare tended to overestimate the intraocular pressure values by 1 mm Hg (p < 0.001), whereas no significant difference was observed using Perkins and Tonopen XL [19]. Nacaroglu et al. also published a study that evaluated intraocular pressure measurements over contact lenses in comparison to Goldmann applanation tonometry. It was found that the mean of the measurements taken over contact lenses was higher than measurements taken without contact lenses. The difference of the measurements taken
5. Conclusion Rebound tonometry measurements obtained over extended-use lotrafilcon A bandage contact lenses (Alcon Air Optix Night & Day Aqua Contact Lenses) using the iCare PRO tonometer are statistically similar to those obtained from “naked eyes.” The removal of this type of soft contact lens before intraocular pressure measurement is not necessary when using this type of rebound tonometer. A major limitation of this study is that it was conducted only on normal eyes. Future studies must be done on patients with abnormal ocular surface and intraocular pressure to assess the applicability of the results to these populations. Funding The contact lenses were sponsored by Alcon Research, Limited. The iCare probes were provided by Medilight, Incorporated. Disclaimer The sponsors had no role in the design or conduct of this research. Ethics approval This study was approved by an Ethics Board. The study was conducted in accordance with the tenets of the Declaration of Helsinki. Provenance and peer review Not commissioned; externally peer reviewed. Data availability statement Data are available on request. Declaration of Competing Interest None declared. 3
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C.P. Azarcon and R.C. dela Cruz
References
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