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CLAE-811; No. of Pages 5
Contact Lens & Anterior Eye xxx (2015) xxx–xxx
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Central corneal thickness evaluation in healthy eyes with three different optical devices Michele Lanza a,b,∗ , Erica Paolillo a , Ugo Antonello Gironi Carnevale a , Alessandro Lanza a , Carlo Irregolare b , Luigi Mele a , Mario Bifani a a b
Dipartimento Multidisciplinare di Scienze Mediche, Chirurgiche e Odontoiatriche, Seconda Università di Napoli, Napoli, Italy Centro Grandi Apparecchiature, Seconda Università di Napoli, Napoli, Italy
a r t i c l e
i n f o
Article history: Received 22 December 2014 Received in revised form 29 March 2015 Accepted 13 May 2015 Keywords: Central corneal thickness Optical pachymetry Scheimpflug camera Orbscan II
a b s t r a c t Purpose: To compare corneal pachymetry values measured by three different optical devices: Orbscan II, Pentacam HR and Sirius in healthy eyes. Methods: The central corneal thickness (CCT) of 102 eyes of 102 healthy subjects (mean age of 33.09 ± 8.72 years and mean refractive defect −4.11 ± 4.74 D) was measured by three different physicians using Orbscan II, Pentacam HR and Sirius. The normality of the distribution was evaluated by with Kolmogorov–Smirnov test. The correlations between CCT obtained from each device and refractive defect and age were evaluated using the Pearson test. The differences were evaluated by the Student paired t-test using SPSS 18.0 (IBM Corp. Armonk, New York). Results: Orbscan II provided significant (p < 0.0001) lower CCT measurements then both Pentacam HR (−13.66 ± 16.53 m) and Sirius (−15.18 ± 17.16 m); Sirius showed values slightly higher than Oculus Pentacam HR (+1.52 ± 6.21 m) that appeared to be statistically significant (p < 0.015). Conclusions: The measurement of CCT by Sirius and Pentacam HR provides similar results. By contrast, the results obtained by Orbscan II are different from those obtained from both Sirius and Pentacam HR. © 2015 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
1. Introduction Central corneal thickness (CCT) evaluation is becoming increasingly important in ophthalmic practice [1]. An accurate CCT measurement is essential because this parameter influences the measurement of intraocular pressure by Goldmann applanation tonometry [2]. Therefore, it is mandatory to screen patients undergoing refractive surgery [1,3]. Finally, CCT evaluation has a key role in the management of such corneal diseases, as keratoconus, contact lens-related complications and dry-eye [4,5]. So far ultrasound pachymetry (USP) has been the most commonly used method to measure CCT and it is still considered the gold-standard [6]. In recent years, several optical devices have been developed to measure CCT such as Orbscan II (Bausch & Lomb, Rochester, NY, USA), Pentacam HR (Oculus Inc, Wetzlar, Germany), Sirius (CSO, Firenze, Italy), Galilei (Ziemer, Port, Switzerland) and Optical Coherence Tomography [7–16]. USP is a contact method,
∗ Corresponding author at: Multidisciplinary Department of Medical, Surgical and Dental Sciences, Seconda Università di Napoli, Via de Crecchio 16, 80100 Napoli, Italy. Tel.: +39 0815666768; fax: +39 0815666775. E-mail address: [email protected] (M. Lanza).
which requires corneal anesthesia and can cause corneal discomfort and infections. In addition, the reproducibility of the technique is operator dependent and only one corneal point can be measured at once. By contrast the optical devices, instead, do not require anesthesia. They do not cause corneal discomfort and there is no risk of infections; furthermore, they are less operator-dependent. For those above reasons, the no-contact devices are becoming increasingly common in the clinical practice [6–18]. Several authors have started to investigate the reproducibility of corneal pachymetry of those different optical devices. The results comparing different devices have provided contrasting results [6–18]. This prospective study was undertaken to compare CCT measurements obtained with Orbscan II, Pentacam HR and Sirius in healthy eyes.
2. Subjects and methods In this study, 102 eyes of 102 healthy subjects (51 males and 51 females) screened to undergo refractive surgery with a mean age of 33.09 ± 8.72 years (range from 20 to 56 years old) and a mean refractive defect, measured as spherical equivalent, of −4.11 ± 4.74 D (range from −18 to +5.5 D) were evaluated. Participants with
http://dx.doi.org/10.1016/j.clae.2015.05.006 1367-0484/© 2015 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Lanza M, et al. Central corneal thickness evaluation in healthy eyes with three different optical devices. Contact Lens Anterior Eye (2015), http://dx.doi.org/10.1016/j.clae.2015.05.006
G Model
ARTICLE IN PRESS
CLAE-811; No. of Pages 5
M. Lanza et al. / Contact Lens & Anterior Eye xxx (2015) xxx–xxx
2
systemic and ocular diseases such as diabetes, connective tissue diseases, dry eyes, keratoconus, uveitis, corneal and lens opacities, glaucoma, retinal pathologies, previous intraocular or corneal surgery, trauma or pregnancy that could interfere with the purpose of the study were excluded. Every subject was asked to stop wearing contact lenses for at least 1 month before undergoing a complete ophthalmic evaluation, which included CCT measurements with Orbscan II, Pentacam HR and Sirius. Three different physicians performed CCT evaluation and no one knew the other ones results. Data were collected by a fourth physician to avoid operator-related bias. The original version of Orbscan slit-scanning topography system was introduced in 1995. In the subsequent version, Orbscan II, the Placido disc technique was incorporated to enable direct measurement of corneal curvature. During data acquisition, 20 slits are projected onto the cornea from each side for a total of 40 slits. Data from 240 points are extracted from each slit, and processed by the software to calculate different variables. Some of the most important variables that are measured indirectly include the corneal thickness and anterior chamber depth. In this study, CCT was measured using the acoustic equivalent correction factor [9]. Oculus Pentacam HR is a combined device consisting of a slit illumination system and a Scheimpflug camera which rotates around the eye. This camera is oriented according to the Scheimpflug principle, thus creating an image of the illuminated plane which appears completely sharp from the anterior surface of the cornea right up to the posterior surface of the crystalline lens. Eye movements during image acquisition are captured by a second camera (pupil camera) and taken into account in the mathematical evaluation. This produces a set of three-dimensional measurement data which gives a precise geometric description of the anterior eye segment [6–9]. Sirius is a diagnostic device of the latest generation combining a 3D rotating Scheimpflug camera with a Placido disc topographer with 22 rings. This “two in one system” allows a fast and complete analysis of both the entire cornea and the anterior segment in one step. A pachymetry map is then reconstructed using the point-bypoint anterior and posterior corneal surface data [12–18]. Every scan has been performed three times and the average of them has been used for statistical evaluation.
Table 1 Means, standard deviations and ranges of central corneal thickness values obtained with the different devices.
Pentacam (m) Orbscan II (m) Sirius (m)
Mean
SD
Range
541.02 527.36 542.54
31.58 37.78 32.09
From 472 to 634 From 438 to 610 From 479 to 629
Although every subject underwent evaluation in both eyes, only the right ones were included in the study to avoid the introduction of bias depending on the strong relation that is usually possible to observe between the right and left eye of the same patient. The normality of the distribution was tested with Kolmogorov–Smirnov test; the correlations between CCT obtained from every device and refractive defect and age were statistically evaluated using the Pearson test. The differences between groups were evaluated with the Student paired t-test using SPSS 18.0 (IBM Corp. Armonk, New York). The study was performed in accordance with the ethical standards stated in the 1964 Declaration of Helsinki and approved by the local clinical research ethics committee. Informed consent was obtained from all patients. 3. Results Values of CCT provided by Orbscan II, Oculus Pentacam HR and Sirius are summarized in Table 1. Differences among values provided by each devices are summarized in Fig. 1 and Table 2. Orbscan II provided significant (p < 0.0001) lower CCT measurements than both Oculus Pentacam HR (−13.66 ± 16.53 m, Fig. 1A) and Sirius (−15.18 ± 17.16 m, Fig. 1B). Sirius provided values slightly higher than Oculus Pentacam HR (+1.52 ± 6.21 m, Fig. 1C) that appeared to be statistically significant (p < 0.015) but not clinically relevant. Values provided by the three devices showed an high correlation when compared each others (Figs. 2–4) and this tendence appeared to be constant both for lower CCT values both for higher ones. Differences between Sirius and Orbscan II and between Oculus Pentacam HR and Orbscan II showed a significant correlation with age (Table 3) and spherical defect (Table 3). No significant
Table 2 Means, standard deviations, ranges and significances of central corneal thickness differences obtained comparing the different devices.
Difference pentacam − orbscan II (m) Difference sirius − Orbscan II (m) Difference Sirius − Pentacam (m)
Mean
SD
Range
p
+13.66 +15.18 +1.52
16.53 17.16 6.21
From −52 to +58 From −47 to +57 From −14 to +14
ARTICLE IN PRESS
CLAE-811; No. of Pages 5
Contact Lens & Anterior Eye xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Contact Lens & Anterior Eye journal homepage: www.elsevier.com/locate/clae
Central corneal thickness evaluation in healthy eyes with three different optical devices Michele Lanza a,b,∗ , Erica Paolillo a , Ugo Antonello Gironi Carnevale a , Alessandro Lanza a , Carlo Irregolare b , Luigi Mele a , Mario Bifani a a b
Dipartimento Multidisciplinare di Scienze Mediche, Chirurgiche e Odontoiatriche, Seconda Università di Napoli, Napoli, Italy Centro Grandi Apparecchiature, Seconda Università di Napoli, Napoli, Italy
a r t i c l e
i n f o
Article history: Received 22 December 2014 Received in revised form 29 March 2015 Accepted 13 May 2015 Keywords: Central corneal thickness Optical pachymetry Scheimpflug camera Orbscan II
a b s t r a c t Purpose: To compare corneal pachymetry values measured by three different optical devices: Orbscan II, Pentacam HR and Sirius in healthy eyes. Methods: The central corneal thickness (CCT) of 102 eyes of 102 healthy subjects (mean age of 33.09 ± 8.72 years and mean refractive defect −4.11 ± 4.74 D) was measured by three different physicians using Orbscan II, Pentacam HR and Sirius. The normality of the distribution was evaluated by with Kolmogorov–Smirnov test. The correlations between CCT obtained from each device and refractive defect and age were evaluated using the Pearson test. The differences were evaluated by the Student paired t-test using SPSS 18.0 (IBM Corp. Armonk, New York). Results: Orbscan II provided significant (p < 0.0001) lower CCT measurements then both Pentacam HR (−13.66 ± 16.53 m) and Sirius (−15.18 ± 17.16 m); Sirius showed values slightly higher than Oculus Pentacam HR (+1.52 ± 6.21 m) that appeared to be statistically significant (p < 0.015). Conclusions: The measurement of CCT by Sirius and Pentacam HR provides similar results. By contrast, the results obtained by Orbscan II are different from those obtained from both Sirius and Pentacam HR. © 2015 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
1. Introduction Central corneal thickness (CCT) evaluation is becoming increasingly important in ophthalmic practice [1]. An accurate CCT measurement is essential because this parameter influences the measurement of intraocular pressure by Goldmann applanation tonometry [2]. Therefore, it is mandatory to screen patients undergoing refractive surgery [1,3]. Finally, CCT evaluation has a key role in the management of such corneal diseases, as keratoconus, contact lens-related complications and dry-eye [4,5]. So far ultrasound pachymetry (USP) has been the most commonly used method to measure CCT and it is still considered the gold-standard [6]. In recent years, several optical devices have been developed to measure CCT such as Orbscan II (Bausch & Lomb, Rochester, NY, USA), Pentacam HR (Oculus Inc, Wetzlar, Germany), Sirius (CSO, Firenze, Italy), Galilei (Ziemer, Port, Switzerland) and Optical Coherence Tomography [7–16]. USP is a contact method,
∗ Corresponding author at: Multidisciplinary Department of Medical, Surgical and Dental Sciences, Seconda Università di Napoli, Via de Crecchio 16, 80100 Napoli, Italy. Tel.: +39 0815666768; fax: +39 0815666775. E-mail address: [email protected] (M. Lanza).
which requires corneal anesthesia and can cause corneal discomfort and infections. In addition, the reproducibility of the technique is operator dependent and only one corneal point can be measured at once. By contrast the optical devices, instead, do not require anesthesia. They do not cause corneal discomfort and there is no risk of infections; furthermore, they are less operator-dependent. For those above reasons, the no-contact devices are becoming increasingly common in the clinical practice [6–18]. Several authors have started to investigate the reproducibility of corneal pachymetry of those different optical devices. The results comparing different devices have provided contrasting results [6–18]. This prospective study was undertaken to compare CCT measurements obtained with Orbscan II, Pentacam HR and Sirius in healthy eyes.
2. Subjects and methods In this study, 102 eyes of 102 healthy subjects (51 males and 51 females) screened to undergo refractive surgery with a mean age of 33.09 ± 8.72 years (range from 20 to 56 years old) and a mean refractive defect, measured as spherical equivalent, of −4.11 ± 4.74 D (range from −18 to +5.5 D) were evaluated. Participants with
http://dx.doi.org/10.1016/j.clae.2015.05.006 1367-0484/© 2015 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Lanza M, et al. Central corneal thickness evaluation in healthy eyes with three different optical devices. Contact Lens Anterior Eye (2015), http://dx.doi.org/10.1016/j.clae.2015.05.006
G Model
ARTICLE IN PRESS
CLAE-811; No. of Pages 5
M. Lanza et al. / Contact Lens & Anterior Eye xxx (2015) xxx–xxx
2
systemic and ocular diseases such as diabetes, connective tissue diseases, dry eyes, keratoconus, uveitis, corneal and lens opacities, glaucoma, retinal pathologies, previous intraocular or corneal surgery, trauma or pregnancy that could interfere with the purpose of the study were excluded. Every subject was asked to stop wearing contact lenses for at least 1 month before undergoing a complete ophthalmic evaluation, which included CCT measurements with Orbscan II, Pentacam HR and Sirius. Three different physicians performed CCT evaluation and no one knew the other ones results. Data were collected by a fourth physician to avoid operator-related bias. The original version of Orbscan slit-scanning topography system was introduced in 1995. In the subsequent version, Orbscan II, the Placido disc technique was incorporated to enable direct measurement of corneal curvature. During data acquisition, 20 slits are projected onto the cornea from each side for a total of 40 slits. Data from 240 points are extracted from each slit, and processed by the software to calculate different variables. Some of the most important variables that are measured indirectly include the corneal thickness and anterior chamber depth. In this study, CCT was measured using the acoustic equivalent correction factor [9]. Oculus Pentacam HR is a combined device consisting of a slit illumination system and a Scheimpflug camera which rotates around the eye. This camera is oriented according to the Scheimpflug principle, thus creating an image of the illuminated plane which appears completely sharp from the anterior surface of the cornea right up to the posterior surface of the crystalline lens. Eye movements during image acquisition are captured by a second camera (pupil camera) and taken into account in the mathematical evaluation. This produces a set of three-dimensional measurement data which gives a precise geometric description of the anterior eye segment [6–9]. Sirius is a diagnostic device of the latest generation combining a 3D rotating Scheimpflug camera with a Placido disc topographer with 22 rings. This “two in one system” allows a fast and complete analysis of both the entire cornea and the anterior segment in one step. A pachymetry map is then reconstructed using the point-bypoint anterior and posterior corneal surface data [12–18]. Every scan has been performed three times and the average of them has been used for statistical evaluation.
Table 1 Means, standard deviations and ranges of central corneal thickness values obtained with the different devices.
Pentacam (m) Orbscan II (m) Sirius (m)
Mean
SD
Range
541.02 527.36 542.54
31.58 37.78 32.09
From 472 to 634 From 438 to 610 From 479 to 629
Although every subject underwent evaluation in both eyes, only the right ones were included in the study to avoid the introduction of bias depending on the strong relation that is usually possible to observe between the right and left eye of the same patient. The normality of the distribution was tested with Kolmogorov–Smirnov test; the correlations between CCT obtained from every device and refractive defect and age were statistically evaluated using the Pearson test. The differences between groups were evaluated with the Student paired t-test using SPSS 18.0 (IBM Corp. Armonk, New York). The study was performed in accordance with the ethical standards stated in the 1964 Declaration of Helsinki and approved by the local clinical research ethics committee. Informed consent was obtained from all patients. 3. Results Values of CCT provided by Orbscan II, Oculus Pentacam HR and Sirius are summarized in Table 1. Differences among values provided by each devices are summarized in Fig. 1 and Table 2. Orbscan II provided significant (p < 0.0001) lower CCT measurements than both Oculus Pentacam HR (−13.66 ± 16.53 m, Fig. 1A) and Sirius (−15.18 ± 17.16 m, Fig. 1B). Sirius provided values slightly higher than Oculus Pentacam HR (+1.52 ± 6.21 m, Fig. 1C) that appeared to be statistically significant (p < 0.015) but not clinically relevant. Values provided by the three devices showed an high correlation when compared each others (Figs. 2–4) and this tendence appeared to be constant both for lower CCT values both for higher ones. Differences between Sirius and Orbscan II and between Oculus Pentacam HR and Orbscan II showed a significant correlation with age (Table 3) and spherical defect (Table 3). No significant
Table 2 Means, standard deviations, ranges and significances of central corneal thickness differences obtained comparing the different devices.
Difference pentacam − orbscan II (m) Difference sirius − Orbscan II (m) Difference Sirius − Pentacam (m)
Mean
SD
Range
p
+13.66 +15.18 +1.52
16.53 17.16 6.21
From −52 to +58 From −47 to +57 From −14 to +14
