Reports Discrepancy in Subfoveal Choroidal Thickness in Healthy Adults with Isometropia With the introduction of enhanced depth imaging optical coherence tomography (OCT), there have been a few studies investigating interocular differences in choroidal thickness.1e4 Previous studies have demonstrated interocular symmetry of choroidal thickness, and interocular difference seems to be correlated with interocular difference of axial length in adults1,2 and children.3 However, in our clinical setting, interocular differences of choroidal thicknesses are greater in some individuals, although these patients do not seem to have definite anisometropia. Thus, we investigated the interocular discrepancy in subfoveal choroidal thickness in healthy volunteers with isometropia in this study. This prospective study included 100 healthy volunteers between 20 and 50 years of age. The inclusion criteria were (1) no history of vitreoretinal disease or intraocular surgery and (2) no systemic diseases such as diabetes or hypertension. The exclusion criteria were (1) anisometropia showing interocular difference of >1.00 diopters in spherical equivalent refraction and (2) axial length of >26.5 mm or any sign of pathologic myopia, such as lacquer cracks. The study protocol was approved by the Institutional Review Board of the Catholic Kwandong University College of Medicine, and adhered to the tenets of the Declaration of Helsinki. Informed consent was obtained from all participants. Baseline examination included slit-lamp examination, intraocular pressure measurement using a noncontact tonometer, fundus examination, and axial length measurement by partial coherence interferometry (IOLMaster; Carl Zeiss, Dublin, CA). Refractive errors were measured using an autorefractor, and then converted to spherical equivalents. Choroidal thickness was measured using spectral domain OCT (Spectralis; Heidelberg Engineering, Dossenheim, Germany) with enhanced depth imaging. Using digital calipers provided by the Heidelberg Spectralis OCT software, choroidal thickness was measured at the subfoveal region in each trans-sectional image of the horizontal, vertical, and 6-radial macular scan and then averaged. Two independent observers blinded to the clinical data of each patient (H.M.K., S.J.K.) measured subfoveal choroidal thickness. Estimated interocular difference of subfoveal choroidal thickness was calculated as follows: calculated correlation factor of axial length with subfoveal choroidal thickness (mm/mm) difference of axial length (mm). We defined the presence of a discrepancy as when the gap between the estimated and measured difference of subfoveal choroidal thickness was >10 mm. Then, the difference of subfoveal choroidal thickness was further classified by 10-mm intervals: difference within 10 mm as group 1, difference >10 and 50 mm was classified as group 6. We used IBM SPSS Statistics Version 18.0 software for Windows (IBM Corporation, Somers, NY) for statistical analyses. The Mauchly test of sphericity and Kolmogorov-Smirnov analyses were used to confirm statistical validity. We used the Student t test
was used for continuous variables and the independent c2 test for categorical variables. For comparison among 6 groups, the Kruskale Wallis test was performed. Stepwise multiple regression analysis was used to analyze correlations between baseline factors and subfoveal choroidal thickness. Interobserver agreement was calculated using the Kappa statistics. Results with P < 0.05 were considered significant. A total of 100 volunteers (200 eyes) participated in this study. Mean age was 31.38.4 years (range, 20e49), and baseline characteristics of the study subjects are summarized in Table 1 (available at www.aaojournal.org). Baseline factors including axial length, sex, and age were used for correlation analyses with subfoveal choroidal thickness by stepwise multiple regression analysis. Among the factors, axial length thickness (B ¼ 32.2; P < 0.001) and sex (B ¼ 45.4; P ¼ 0.019) were correlated with subfoveal choroidal thickness. The estimated difference of subfoveal choroidal thickness was calculated using these coefficient constants. Among 100 subjects, 73 (73%) showed a discrepancy in subfoveal choroidal thickness (interobserver agreement k ¼ 0.98). There was no difference between baseline values for age, sex, or axial lengths between the discrepancy and the no discrepancy group (Table 2; available at www.aaojournal.org). When comparing the mean difference of subfoveal choroidal thicknesses, the discrepancy group showed significantly greater differences in subfoveal choroidal thickness by using the pairedeye comparison (P ¼ 0.001; Student t test). We classified the discrepancy of subfoveal choroidal thicknesses into 6 subgroups, with good interobserver agreement (k ¼ 0.96). Group 1 was the no discrepancy group (n ¼ 27). There were 17 subjects (17%) in group 2; 14 each (14%) in groups 3 and 4; and 8 (8%) in group 5. Twenty subjects (20%) showed a difference of >50 mm and were included in group 6. Comparison among the 6 groups showed that there were no differences in the estimated differences of subfoveal choroidal thickness (P ¼ 0.330, Kruskal-Wallis test) or axial length (P ¼ 0.329, Kruskal-Wallis test). However, the real difference of subfoveal choroidal thickness was significantly different among the groups (P < 0.001, Kruskal-Wallis test), as well as the gap between the estimated and real subfoveal choroidal thickness (P < 0.001, Kruskal-Wallis test; Fig 1). In this study, we sought to determine whether there was interocular discrepancy in the subfoveal choroidal thickness. Among 100 subjects, 73 participants (73%) showed discrepancy in the subfoveal choroidal thickness, and 20 subjects (20%) showed a discrepancy of >50 mm. Although the difference of axial lengths was not different between the discrepancy and no discrepancy groups, the difference of the subfoveal choroidal thickness was significant between the 2 groups: mean of 51.748.5 mm in the discrepancy group and 13.513.7 mm in the no discrepancy group. Furthermore, there was no difference in age, sex, axial length, or refractive error between the 2 groups. We found that some individuals have interocular discrepancy in subfoveal choroidal thickness. This may be a variation of normal phenomenon, or it may be an underlying causative factor for some diseases. Although we cannot identify the exact mechanisms and
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Ophthalmology Volume -, Number -, Month 2015
Figure 1. Discrepancy in subfoveal choroidal thickness. This 27-year-old woman had refractive errors of 5.25 diopters in the both eyes. Axial length was 26.32 mm in the right eye and 26.45 in the left. The subfoveal choroidal thickness on horizontal scan was 284.0 mm in the right eye (A) and 393.0 mm in the left (B). The mean subfoveal choroidal thickness was 284.5 mm in the right eye and 381.5 mm in the left, showing 97.0 mm of difference between the eyes.
clinical meaning of discrepancy in subfoveal choroidal thickness at this point, we believe that further investigations with long-term follow-up may answer these questions. 1,2
HAE M. KANG, MD SUK J. KIM, MD3 HYOUNG J. KOH, MD, PHD2 CHRISTOPHER S. LEE, MD, PHD2 SUNG C. LEE, MD, PHD2 1 Department of Ophthalmology, Catholic Kwandong University College of Medicine, International St. Mary’s Hospital, Incheon, Republic of Korea; 2Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Republic of Korea; 3Department of Ophthalmology, Saevit Eye Hospital, Goyang-shi, Republic of Korea
Financial Disclosure(s): The authors made the following disclosures: H.J.K.: Consultant e Allergan and Novartis Korea. Author Contributions: Conception and design: Kang Analysis and interpretation: Kang, Kim, Koh, C. Lee, S. Lee
2
Data collection: Kang, Kim Overall responsibility: Kang, Kim, Koh, C. Lee, S. Lee Correspondence: Hae Min Kang, MD, Department of Ophthalmology, Catholic Kwandong University College of Medicine, International St. Mary’s Hospital, 100 Simgok-ro, Seo-gu, Inchoen, 120-752, Republic of Korea. E-mail: [email protected].
References 1. Spaide RF, Koizumi H, Pozzoni MC. Enhanced depth imaging spectral-domain optical coherence tomography. Am J Ophthalmol 2008;146:496–500. 2. Chen FK, Yeoh J, Rahman W, et al. Topographic variation and interocular symmetry of macular choroidal thickness using enhanced depth imaging optical coherence tomography. Invest Ophthalmol Vis Sci 2012;53:975–85. 3. Al-Haddad C, El Chaar L, Antonios R, et al. Interocular symmetry in macular choroidal thickness in children. J Ophthalmol 2014;2014:472391. 4. Vincent SJ, Collins MJ, Read SA, Carney LG. Retinal and choroidal thickness in myopic anisometropia. Invest Ophthalmol Vis Sci 2013;54:2445–56.
was used for continuous variables and the independent c2 test for categorical variables. For comparison among 6 groups, the Kruskale Wallis test was performed. Stepwise multiple regression analysis was used to analyze correlations between baseline factors and subfoveal choroidal thickness. Interobserver agreement was calculated using the Kappa statistics. Results with P < 0.05 were considered significant. A total of 100 volunteers (200 eyes) participated in this study. Mean age was 31.38.4 years (range, 20e49), and baseline characteristics of the study subjects are summarized in Table 1 (available at www.aaojournal.org). Baseline factors including axial length, sex, and age were used for correlation analyses with subfoveal choroidal thickness by stepwise multiple regression analysis. Among the factors, axial length thickness (B ¼ 32.2; P < 0.001) and sex (B ¼ 45.4; P ¼ 0.019) were correlated with subfoveal choroidal thickness. The estimated difference of subfoveal choroidal thickness was calculated using these coefficient constants. Among 100 subjects, 73 (73%) showed a discrepancy in subfoveal choroidal thickness (interobserver agreement k ¼ 0.98). There was no difference between baseline values for age, sex, or axial lengths between the discrepancy and the no discrepancy group (Table 2; available at www.aaojournal.org). When comparing the mean difference of subfoveal choroidal thicknesses, the discrepancy group showed significantly greater differences in subfoveal choroidal thickness by using the pairedeye comparison (P ¼ 0.001; Student t test). We classified the discrepancy of subfoveal choroidal thicknesses into 6 subgroups, with good interobserver agreement (k ¼ 0.96). Group 1 was the no discrepancy group (n ¼ 27). There were 17 subjects (17%) in group 2; 14 each (14%) in groups 3 and 4; and 8 (8%) in group 5. Twenty subjects (20%) showed a difference of >50 mm and were included in group 6. Comparison among the 6 groups showed that there were no differences in the estimated differences of subfoveal choroidal thickness (P ¼ 0.330, Kruskal-Wallis test) or axial length (P ¼ 0.329, Kruskal-Wallis test). However, the real difference of subfoveal choroidal thickness was significantly different among the groups (P < 0.001, Kruskal-Wallis test), as well as the gap between the estimated and real subfoveal choroidal thickness (P < 0.001, Kruskal-Wallis test; Fig 1). In this study, we sought to determine whether there was interocular discrepancy in the subfoveal choroidal thickness. Among 100 subjects, 73 participants (73%) showed discrepancy in the subfoveal choroidal thickness, and 20 subjects (20%) showed a discrepancy of >50 mm. Although the difference of axial lengths was not different between the discrepancy and no discrepancy groups, the difference of the subfoveal choroidal thickness was significant between the 2 groups: mean of 51.748.5 mm in the discrepancy group and 13.513.7 mm in the no discrepancy group. Furthermore, there was no difference in age, sex, axial length, or refractive error between the 2 groups. We found that some individuals have interocular discrepancy in subfoveal choroidal thickness. This may be a variation of normal phenomenon, or it may be an underlying causative factor for some diseases. Although we cannot identify the exact mechanisms and
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Ophthalmology Volume -, Number -, Month 2015
Figure 1. Discrepancy in subfoveal choroidal thickness. This 27-year-old woman had refractive errors of 5.25 diopters in the both eyes. Axial length was 26.32 mm in the right eye and 26.45 in the left. The subfoveal choroidal thickness on horizontal scan was 284.0 mm in the right eye (A) and 393.0 mm in the left (B). The mean subfoveal choroidal thickness was 284.5 mm in the right eye and 381.5 mm in the left, showing 97.0 mm of difference between the eyes.
clinical meaning of discrepancy in subfoveal choroidal thickness at this point, we believe that further investigations with long-term follow-up may answer these questions. 1,2
HAE M. KANG, MD SUK J. KIM, MD3 HYOUNG J. KOH, MD, PHD2 CHRISTOPHER S. LEE, MD, PHD2 SUNG C. LEE, MD, PHD2 1 Department of Ophthalmology, Catholic Kwandong University College of Medicine, International St. Mary’s Hospital, Incheon, Republic of Korea; 2Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Republic of Korea; 3Department of Ophthalmology, Saevit Eye Hospital, Goyang-shi, Republic of Korea
Financial Disclosure(s): The authors made the following disclosures: H.J.K.: Consultant e Allergan and Novartis Korea. Author Contributions: Conception and design: Kang Analysis and interpretation: Kang, Kim, Koh, C. Lee, S. Lee
2
Data collection: Kang, Kim Overall responsibility: Kang, Kim, Koh, C. Lee, S. Lee Correspondence: Hae Min Kang, MD, Department of Ophthalmology, Catholic Kwandong University College of Medicine, International St. Mary’s Hospital, 100 Simgok-ro, Seo-gu, Inchoen, 120-752, Republic of Korea. E-mail: [email protected].
References 1. Spaide RF, Koizumi H, Pozzoni MC. Enhanced depth imaging spectral-domain optical coherence tomography. Am J Ophthalmol 2008;146:496–500. 2. Chen FK, Yeoh J, Rahman W, et al. Topographic variation and interocular symmetry of macular choroidal thickness using enhanced depth imaging optical coherence tomography. Invest Ophthalmol Vis Sci 2012;53:975–85. 3. Al-Haddad C, El Chaar L, Antonios R, et al. Interocular symmetry in macular choroidal thickness in children. J Ophthalmol 2014;2014:472391. 4. Vincent SJ, Collins MJ, Read SA, Carney LG. Retinal and choroidal thickness in myopic anisometropia. Invest Ophthalmol Vis Sci 2013;54:2445–56.
