Myopia, Axial Length, and OCT Characteristics of the Macula in Singaporean Children

Abstract

purpose. The purpose of this study was to evaluate the associations between macular volume and thickness, as assessed by optic coherence tomography (OCT), with refraction and axial length (AL) in children.

methods. A total of 104 Chinese school children (51 girls and 53 boys) 11 to 12 years of age were randomly selected from one school during the 2005 examination in the Singapore Cohort Study of the Risk Factors for Myopia (SCORM). Cycloplegic autorefraction was performed to obtain refraction (defined as spherical equivalent [SE]) and ultrasound biometry performed to obtain the AL. Macular volume and thickness were then measured (StratusOCT3; Carl Zeiss Meditec, Dublin, CA).

results. Children with moderate myopia (SE at least −3.0 D) tended to have smaller total macular volume and thinner quadrant-specific macular thickness (except in the inferior and superior inner quadrants), followed by children with low myopia (−0.5 ≤ SE < −3.0 D), compared with children with no myopia (SE > −0.5 D). Total macular volume was positively associated with SE (β = 1.58, 95% CI, 0.84 to 2.32, standardized β = 0.14, P < 0.001) and negatively associated with AL (β = −1.20, 95% CI, −1.62 to −0.79, standardized β = 0.45, P < 0.001) in multiple linear regression models controlling for age and gender.

conclusions. In children, increasing axial myopia was associated with reduced macular volume and thickness. These findings suggest that early anatomic changes may be present in the retinas of children with axial myopia.

Myopia is a common condition affecting a significant proportion of the population, particularly in East Asian countries. In Singapore, Hong Kong, and Taiwan, the prevalence of high myopia (at least −6.0 D) appears to be rising and may lead to a future increase in the incidence of potentially blinding ocular morbidity such as glaucoma, cataract, retinal detachment, and myopic neovascular macular degeneration. ^{1 2 3 4 5} Retinal changes in persons with high myopia include peripapillary atrophy, peripheral lattice degeneration, tilting or malinsertion of the optic disc, posterior staphyloma, and breaks in Bruch’s membrane. ^{1 6}  

Few studies have evaluated possible structural retinal changes in individuals with low to moderate myopia without evidence of clinically overt retinal disease. In adults, studies based on the use of optical coherence tomography (OCT) to detect subtle macular changes have shown inconsistent results. ^{7 8} In two Asian adult OCT studies in Japan and Singapore, the average macular retinal thickness did not vary with refraction. ^{9 10} However, in the Singapore study, minimum (foveal) macular thickness was greater in adults with longer axial lengths (ALs), whereas the parafoveal macular layers in the superior and inferior quadrants were thinner. Macular thickness of the nasal and superior quadrants were greater than the temporal and inferior parts. ^{9 10}  

There are few studies in children in which early macular anatomic features have been examined in myopic eyes. In a study using OCT among Polish adolescents 14 to 18 years of age, macular thickness decreased with increasing myopic refraction, with a mean macular retinal thickness of 231.0 μm in eyes with low myopia, 218.0 μm in moderate myopia, and 178.0 μm in high myopia. ¹¹  

To our knowledge, however, there are no reports of the correlations of OCT-defined parameters with ocular biometry in children. The purpose of this study was to investigate the associations of OCT measurements of macular volume and macular thickness with refractive error and AL in Singaporean children. 

Methods

Study Population

The methodology of the Singapore Cohort Study of the Risk Factors of Myopia (SCORM) has been described previously. ^{12 13} The study commenced in 1999, and schoolchildren in grades 1 to 3 (ages 7–9 years), attending three schools (located in the Eastern, Northern, and Western Singapore) were recruited. Subjects with media opacity, pseudoexfoliation, uveitis, or pigment dispersion syndrome and a history of intraocular surgery or refractive surgery, glaucoma, or retinal disease were excluded from the study. 

This cohort was examined yearly. During the 2005 (fourth year) examination, 104 Chinese children randomly selected from 561 children in the Western school who were in grades 5 and 6 (ages 11 and 12 years) had OCT measurements. The mean age of this sample was 11.5 ± 0.5 years (51 girls and 53 boys). The mean spherical equivalent (SE) refraction was −1.38 ± 1.58 D (range, −4.5 to +1.10). Comparison of this random sample with those not selected for this study showed that it was similar by age (P = 0.42) and gender (P = 0.91), but the mean SE of this group was less myopic (−1.38 D vs. −2.20 D) and they had shorter ALs (23.87 mm vs. 24.23 mm) compared with those not selected. 

This research followed the tenets of the Declaration of Helsinki. Informed written consent was obtained from parents of each subject, and each procedure was performed with the subjects’ consent. The study was approved by the ethics committee of the Singapore Eye Research Institute. 

Eye Examinations

All children had a standardized examination as follows. Cycloplegic refraction was performed after instillation of 3 drops of 1% cyclopentolate 5 minutes apart. At least 30 minutes after the last drop, five consecutive refraction and keratometry readings were obtained with one of two calibrated autokeratorefractometers (model RK5; Canon, Inc. Ltd., Tochigiken, Japan). AL measurements were obtained using one of two contact ultrasound biometry machines (Echoscan model US-800, probe frequency of 10 mHz; Nidek Co., Ltd., Tokyo, Japan), after 1 drop of 0.5% proparacaine was administered. The average of six measurements was taken if the standard deviation was <0.12 mm. If the standard deviation was ≥0.12 mm, the data were not included, and the measurements were repeated until the standard deviation reached <0.12 mm. 

The OCT measurements (StratusOCT3; Carl Zeiss Meditec, Dublin, CA) were performed in a dim room after cycloplegia. The pupils were dilated to at least 5 mm diameter before the measurements. The measurements of AL and refractive error were entered into the OCT software. The OCT examination was performed by the same ophthalmologist (AF) and analyzed (ver. 4.1 software; Carl Zeiss Meditec, Dublin, CA). Scans were performed using the Fast Macular Thickness protocol and were repeated six times until three good-quality horizontal and three good-quality vertical scans were achieved for each child. Twenty-three parameters were measured by the Fast Macular Thickness scan protocol: the volume and average retinal thickness of the macula, the thickness of four quadrants of the inner and outer macula in the parafoveal area; the minimum macular thickness in the foveal area; and ratios of superior–inferior outer macular thickness and temporal–nasal inner and outer macular thickness by horizontal and vertical 6-mm scans centered against the point of fixation of each eye. 

Definitions and Data Analysis

Spherical equivalent was defined as spherical power plus half-negative cylinder power. Myopia was defined as an SE of at least −0.5 D. Levels of myopia included low myopia, defined as SE ≤ −0.5 D and > −3 D, and moderate myopia, defined as SE of at least −3 D. ¹² The OCT measurements of macular volume and macular thickness were normally distributed. The ANOVA procedure was used to compare the differences in OCT parameters among groups of children with no myopia, low myopia, and moderate myopia and among groups with AL in the highest, middle, and lowest tertiles. Multiple linear regression models were conducted with OCT parameters as the dependent variable, with SE, AL, age, and gender as the covariates. All data were analyzed with statistical software (SPSS ver. 12.0; SPSS Inc., Chicago, IL), and statistical significance was assumed at P < 0.05. However, for multiple comparisons among the 23 parameters measured by the OCT Fast Macular Thickness scan protocol, a Bonferroni correction was applied with resultant significance of P< 0.0022. 

Results

The mean SE was −1.38 ± 1.57 D (median, −1.28; range, −4.57 to +1.10). There were 39 (38%) subjects without myopia (+1.10 to −0.49 D), 43 (41%) with low myopia (−0.50 D to −2.99 D), and 22 (21%) with moderate myopia (−3.00 D to −4.57 D). The mean (±SD) AL was 23.87 ± 1.00 mm (median, 23.91; range, 21.22–26.59). 

The average total macular volume, average foveal volume, overall average macula thickness (overall), and foveal minimum thickness, were 6.65 ± 0.39 mm³ (median, 6.57; range, 5.99–7.67), 0.15 ± 0.01 mm³, 171.4 ± 35.8 μm (median, 169.8; range, 101.3–241.3), and 157.0 ± 19.2 μm (median, 155.8; range, 122.0–208.7), respectively. The boys had higher foveal minimum thickness (162.1 ± 17.5 μm vs. 151.4 ± 19.6 μm) than did the girls. Inner and outer macular thicknesses were significantly positively correlated with inner and outer macular volume in all quadrants (linear regression, P < 0.001). The average inner macular thicknesses of the superior, inferior, temporal, and nasal quadrants were 271.4 ± 14.3, 261.8 ± 13.2, 255.4 ± 13.4, and 266.2 ± 16.2 μm, respectively, and the average outer macular thicknesses were 234.5 ± 13.2, 230.2 ± 14.1, 214.6 ± 13.5, and 254.6 ± 14.9 μm, respectively. 

Comparisons of differences in macular volume and thickness among the children with moderate myopia, low myopia, and no myopia are shown in Table 1 . The children with moderate and mild myopia had significantly lower total macular volume and superior inner, temporal inner, nasal inner, temporal outer, nasal outer, and inferior outer macular volumes than did the children with no myopia. The children with moderate and mild myopia also had higher minimum macular thickness and lower quadrant-specific macular thickness (except inferior inner) than did those with low myopia and no myopia. After the application of the Bonferroni correction for multiple comparisons, only the differences in total macular volume, temporal outer, nasal outer, and inferior outer macular volumes and macular thicknesses remained statistically significant among the three groups. 

Comparisons of the differences in macular volume and thickness among children with highest, middle, and lowest tertiles of AL are shown in Table 2 . The children in the highest tertile had a smaller total macular volume and all outer and inner macular volumes in the four quadrants than did the children in the middle and lowest tertiles. Those in the highest tertile also showed thicker minimum macular thickness and thinner quadrant-specific macular thickness than did the other children. The children in the middle tertile had smaller total macular volume, and all outer and inner macular volumes in four quadrants than did those in the lowest and also had thicker minimum macular thickness and thinner quadrant-specific macular thickness. After the application of the Bonferroni correction, only the differences in total macular volume, all outer macular volumes and outer macular thicknesses, temporal inner macular volume and thickness, nasal inner macular volume, and superior inner macular thickness remained statistically significant among the three groups. 

The changes in total macular volume and foveal minimum macular thickness among different SE and AL groups were small but highly consistent and statistically significant, and the differences in SE and AL among the groups were relatively small as well. The mean total macular volumes in the moderate myopia, low myopia, and nonmyopia groups were 6.48, 6.56, and 6.84 mm³, respectively. The foveal minimum macular thicknesses in the moderate myopia, low myopia, and nonmyopia groups were 167.2, 156.3, and 152.3 μm, respectively (Tables 1 2) . It should be pointed out that the foveal change was in the opposite direction to the rest of the macula in this study (Tables 1 2) . 

Figure 1depicts scatterplots of SE with selected OCT measurements, and Figure 2depicts scatterplots of AL with selected OCT measurements. The Pearson correlation coefficients were 0.44 for total macular volume and SE, −0.07 for average macular thickness versus SE, and −0.26 for minimum macular thickness versus SE. The Pearson correlation coefficients were −0.48 for total macular volume and AL, 0.02 for average macular thickness versus AL, and 0.30 for minimum macular thickness versus AL. 

Table 3shows the results of multiple linear regression models with macular estimates as the dependent variables, and SE and AL as the independent variables, adjusting for age and gender. Figure 3demonstrates a schematic diagram of the OCT macular scan area. The regression coefficients are given for quadrant-specific macular volumes and thicknesses for spherical equivalent in the multiple linear regression model, with macular estimates as the dependent variables and spherical equivalent, axial length, age, and gender as the independent variables. Total macular volume correlated positively with SE—regression coefficients were 1.58 (95% CI, 0.84–2.32, P = 0.0005)—and correlated negatively with AL—regression coefficient = −1.20 (95% CI, −1.62 to −0.79, P = 0.0001). The standardized coefficients of AL and SE in a model with total macular volume as the dependent variable were −0.45 and 0.14, respectively. Moreover, outer and inner macular volume and thickness measurements were significantly positively correlated with SE and negatively with AL, though inner macular volumes and thicknesses were not statistically significant after the application of the Bonferroni correction. There was no linear relationship between average macular thickness with SE (P = 0.80) or AL (P = 0.53). 

The relationships between absolute cylinder and OCT estimates of macular volume and macular thickness were also examined in multiple linear regression models. No OCT measurements significantly correlated with absolute cylinder (P > 0.05). 

Discussion

Our study demonstrated that, in these Singaporean Chinese children aged 11 and 12 years, axial myopia was associated with lower total macular volume and reduced quadrant-specific macular thickness (excepting in the inferior inner and superior inner quadrants). We found significant correlations between total macular volume, quadrant-specific macular volume, and quadrant-specific macular thickness with both SE and AL, after controlling for age and gender. These findings highlight anatomic differences in the macula between the children with moderate myopia, mild myopia, and no myopia. 

One of the key findings of our study is that three-dimensional OCT macular measurement parameters such as total macular volume and outer and inner macular volume decreased with more myopic refraction and increasing AL. The difference in total macular volume among the nonmyopic, low myopic, and high myopic children was small but statistically significant (6.84 ± 0.37 mm³ vs. 6.56 ± 0.37 mm³ vs. 6.48 ± 0.32 mm³, P = 0.0002). To our knowledge, there have been no previous reports regarding differences in macular volume measured by OCT between myopic and nonmyopic subjects. Hess et al. ¹⁴ showed that macular volume was smaller in glaucomatous (6.57 ± 0.85 mm³) than in normal (7.01 ± 0.42 mm³) eyes in white children (P < 0.001). 

The two-dimensional OCT measurements of macular thickness and its correlation with myopia in our study are in agreement with previous reports. ^{9 10} Our findings should be compared with findings from a recent OCT study in a Singaporean adult population. ¹⁰ Both studies show that the thickest point at the parafoveal region decreased with myopia, whereas foveal thickness increased. The reduction in the difference in thickness between the foveal pit and parafoveal crest with increasing myopic refraction in adults ¹⁰ was also observed in our study. 

An interesting observation in our study is that the minimum macular thickness at the foveal region increased, whereas overall macular thickness decreased with increasing myopic refraction and AL. This somewhat paradoxical finding is not easily explainable. Thinner maculae could be due to the stretching of a similar volume of retina over a larger area or a decreased number of photoreceptors. Even early chorioretinal atrophy in high myopia, which had been described in the posterior pole in eyes, has been associated with longer AL and increased retinal thinning with myopia. ^{6 15 16} However, there were few highly myopic children in our study, and it would be surprising if chorioretinal atrophy were present in children with such small amounts of myopia. In contrast, the increased macular thickness in the foveal region may be related to other mechanisms. In a form-deprivation model of myopia of tree shrews, ¹⁷ subfoveal blood-retinal barrier permeability in form-deprived myopic animals was significantly higher than in the control group. It is possible that the increase in minimum macular thickness (in the foveal area), which was associated with increasing myopic SE and AL in our study, may be due to pathologic subfoveal chorioretinal changes. ¹⁸ An alternative explanation for the decreased macular crest thickness along with increased foveal thickness was suggested by Springer and Hendrickson in their experiments of macular modeling during a period of experimentally induced myopia progression in young animals. The absence of vasculature in the foveal area may lead to foveal pits that are very deformable in response to intraocular pressure, and ocular growth-induced retinal stretch may contribute to the formation of foveal pits in primates. ^{19 20 21} The significance of these OCT findings may require further research. 

The similar pattern of associations of OCT measurements with SE and AL in our study was, of course, related to the close correlation between SE and AL (Pearson coefficient = 0.6, P < 0.001), ^{12 22} and indicates that the OCT findings reflect axial myopia. The standardized coefficient of AL was higher than that of SE (0.45 vs. 0.14) in the multiple linear regression model for the prediction of total macular volume. It is well known that more highly myopic eyes have longer AL, which is largely contributed by a greater vitreous chamber depth. ²³ Thus, AL possibly contributes to a relatively larger variation of total macular volume than does just the SE. The “stretch effect” from the elongation of AL in myopic progression may thus in part explain the reduction of macular retinal thickness and macular volume, aspects of an overall stretching process of ocular structures in both myopic human subjects and animal models. ^{23 24}  

We did not find significant correlation between the absolute cylinder reading and the OCT measurements (both macular volume and macular thickness), indicating that the major factor affecting variations in OCT parameters is axial refraction. The overall average macular thickness did not show a significant relationship with refractive error. The measurements were not influenced by the refractive state of the eye. The counteracting effects of the decrease of parafoveal thickness and the increase of foveal thickness with increasing myopic SE and AL may explain the insignificant changes in overall average macular thickness in our study. It should be stated that magnification error may be present in transverse measurements in this StratusOCT study, as the manufacturer (Carl Zeiss Meditec, Inc.) did not control for error in the current version of the instrument. The StratusOCT does not provide correction of the actual scan itself. Future refinement of the instrument should include some estimation of this error introduced by refractive error. Despite this, OCT provided quantification of retinal thickness with the excellent reliability reported in previous studies. ^{7 8 10 25 26} In one study, coefficients of variation of macular thickness measurements by OCT within the same subjects were 10%, decreasing to 9% when scans were repeated five times. ²⁶  

Early macular changes such as peripapillary atrophy have been documented in young myopic children in an Asian country in which high myopia (SE at least −6 D) develops even in young children. ¹² To our knowledge, this is the first report of myopia-related variations in macular anatomy in young children determined by OCT measurement. Because high myopia has been reported to be associated with ocular disease including myopic macular degeneration, macular retinoschisis, and macular holes, the early identification of children with possible myopia-related macular changes is important. ^{3 27 28} It has been shown that kinetics of cone pigments become abnormal preceding the loss of cone cells or chorioretinal degeneration in high myopia. ²⁸ It is uncertain whether there are any direct links between reductions in macular thickness and the subsequent onset of clinically significant macular disease. 

The OCT is a commonly used method in the documentation of retinal diseases. It provides detailed measurements of the optic disc and retinal nerve fiber layer and the detection of decreased macular thickness may provide a sensitive method for the detection and monitoring of early glaucomatous tissue loss in the posterior pole. ²⁹ Our study shows that because macular thickness is influenced by the degree of refractive error, any interpretations of retinal changes should be made only after the refractive error of the individual is considered. Possible limitations of this study include the small number of children with high myopia, the unknown effect of the transverse magnification error, and the possible lack of generalizability of our study to other non-Asian or adult populations. 

In summary, the myopic children in our study had reduced macular volumes and parafoveal thickness. The findings suggest that the three-dimensional OCT may serve as a useful tool in the evaluation of early macular changes in myopic children, although the ultimate clinical significances of these changes require further evaluation. Nonetheless, the degree of refractive error should be considered in all OCT assessments of macular changes in children with other eye diseases. 

 Supported by Singapore National Medical Research Council Grant NMRC/0695/2002.

 Submitted for publication October 24, 2005; revised December 29, 2005, and January 26, 2006; accepted April 26, 2006.

 Disclosure: H.-D. Luo, None; G. Gazzard, None; A. Fong, None; T. Aung, None; S.T. Hoh, None; S.-C. Loon, None; P. Healey, None; D.T.H. Tan, None; T.-Y. Wong, None; S.-M. Saw, None

 The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.

 

Table 1.

 

Macular Volume and Thickness in All Subjects, and in Those with Moderate Myopia, Low Myopia, or No Myopia

OCT Measurements	All Subjects	Moderate Myopia	Low Myopia	No Myopia	P
Macular volume (mm3)
Fovea	0.15 ± 0.01	0.16 ± 0.01	0.15 ± 0.01	0.15 ± 0.02	0.13
	(0.13–0.17)	(0.13–0.18)	(0.13–0.19)	(0.12–0.18)
Temporal inner	0.40 ± 0.02	0.39 ± 0.02	0.40 ± 0.02	0.41 ± 0.02	0.03
	(0.36–0.44)	(0.36–0.42)	(0.35–0.46)	(0.38–0.46)
Superior inner	0.42 ± 0.03	0.41 ± 0.04	0.42 ± 0.02	0.43 ± 0.02	0.01
	(0.36–0.48)	(0.30–0.46)	(0.36–0.47)	(0.40–0.51)
Nasal inner	0.42 ± 0.03	0.41 ± 0.02	0.42 ± 0.03	0.43 ± 0.02	0.03
	(0.36–0.48)	(0.35–0.44)	(0.34–0.49)	(0.38–0.50)
Inferior inner	0.41 ± 0.02	0.41 ± 0.02	0.41 ± 0.02	0.42 ± 0.02	0.11
	(0.37–0.45)	(0.38–0.44)	(0.37–0.45)	(0.37–0.48)
Temporal outer	1.14 ± 0.07	1.10 ± 0.07	1.13 ± 0.07	1.17 ± 0.07	0.001
	(1.00–1.28)	(0.96–1.21)	(1.00–1.32)	(1.06–1.29)
Superior outer	1.25 ± 0.07	1.22 ± 0.07	1.24 ± 0.06	1.27 ± 0.07	0.10
	(1.11–1.39)	(1.10–1.32)	(1.13–1.36)	(1.11–1.50)
Nasal outer	1.36 ± 0.08	1.32 ± 0.07	1.35 ± 0.08	1.39 ± 0.08	0.002
	(1.20–1.52)	(1.14–1.42)	(1.13–1.54)	(1.25–1.67)
Inferior outer	1.22 ± 0.07	1.19 ± 0.07	1.20 ± 0.06	1.27 ± 0.07	0.0003
	(1.08–1.36)	(1.03–1.31)	(1.10–1.35)	(1.14–1.43)
Total	6.65 ± 0.39	6.48 ± 0.32	6.56 ± 0.37	6.84 ± 0.37	0.0002
	(5.89–7.41)	(5.99–7.03)	(6.01–7.53)	(6.24–7.67)
Macular thickness (μm)
Foveal minimum	157.0 ± 19.2	167.2 ± 17.3	156.3 ± 18.8	152.3 ± 19.1	0.02
	(119.4–194.6)	(134.0–206.7)	(124.7–208.7)	(122.0–196.0)
Overall average	171.4 ± 35.8	178.8 ± 39.2	170.9 ± 35.9	168.1 ± 34.3	0.56
	(101.2–241.6)	(102.3–226.0)	(101.3–241.3)	(102.7–232.0)
Temporal inner	255.4 ± 13.4	250.0 ± 11.4	254.5 ± 14.8	259.4 ± 11.9	0.03
	(229.1–281.7)	(228.3–268.7)	(222.7–290.3)	(240.7–291.3)
Superior inner	271.4 ± 14.3	266.0 ± 12.8	270.3 ± 14.8	275.3 ± 13.7	0.05
	(243.4–299.4)	(243.3–293.3)	(239.0–310.7)	(252.7–321.7)
Nasal inner	266.2 ± 16.2	259.0 ± 15.3	265.8 ± 16.8	270.5 ± 14.8	0.03
	(234.4–298.0)	(221.3 ± 279.3)	(218.0–312.0)	(240.3–319.3)
Inferior inner	261.8 ± 13.2	257.7 ± 11.3	260.8 ± 13.3	265.1 ± 13.7	0.12
	(236.0–287.7)	(241.3–279.7)	(237.3–287.3)	(236.0–304.0)
Temporal outer	214.6 ± 13.5	207.6 ± 12.7	212.5 ± 13.0	220.7 ± 12.3	0.001
	(188.1–241.1)	(180.7–227.7)	(188.7–248.7)	(199.3–242.3)
Superior outer	234.5 ± 13.2	228.7 ± 12.8	233.1 ± 11.8	239.0 ± 13.6	0.01
	(208.6–260.4)	(206.7–249.0)	(212.7–256.3)	(210.0–281.7)
Nasal outer	254.6 ± 14.9	247.9 ± 13.6	251.8 ± 12.9	261.2 ± 15.4	0.001
	(225.4–283.8)	(212.7–264.3)	(212.7–273.0)	(235.3–314.7)
Inferior outer	230.2 ± 14.1	223.2 ± 13.4	225.8 ± 11.0	238.7 ± 13.4	0.0003
	(202.6–257.8)	(193.7–245.7)	(206.3–253.7)	(214.3–269.0)
Thickness ratio
Superior/inferior outer	1.02 ± 0.04	1.03 ± 0.04	1.03 ± 0.04	1.00 ± 0.03	0.002
	(0.94–1.10)	(0.94–1.10)	(0.97–1.18)	(0.92–1.08)
Temporal/nasal inner	0.96 ± 0.03	0.97 ± 0.05	0.96 ± 0.03	0.96 ± 0.03	0.53
	(0.90–1.02)	(0.90–1.11)	(0.90–1.08)	(0.88–1.03)
Temporal/nasal outer	0.83 ± 0.07	0.84 ± 0.05	0.83 ± 0.09	0.84 ± 0.04	0.54
	(0.69–0.97)	(0.74–0.96)	(0.29–0.98)	(0.76–0.92)

 Data are the mean ± standard deviation (range). Low myopia was defined as SE ≤−0.5 D and >−3 D, and moderate myopia was defined as SE at least −3 D.

Table 2.

 

Macular Volume and Thickness in All Subjects, and in Those in the Highest, Middle, and Lowest Tertile of AL

OCT Measurements	Highest Tertile (21.22–23.23 mm)	Middle Tertile (23.24–24.30 mm)	Lowest Tertile (24.31–26.59 mm)	P
Macular volume (mm3)
Fovea	0.15 ± 0.01	0.15 ± 0.01	0.15 ± 0.02	0.28
	(0.13–0.18)	(0.13–0.17)	(0.12–0.19)
Temporal inner	0.39 ± 0.02	0.40 ± 0.02	0.41 ± 0.02	0.001
	(0.35–0.42)	(0.35–0.44)	(0.38–0.46)
Superior inner	0.42 ± 0.02	0.42 ± 0.03	0.43 ± 0.02	0.007
	(0.33–0.46)	(0.30–0.46)	(0.40–0.51)
Nasal inner	0.41 ± 0.02	0.42 ± 0.02	0.43 ± 0.03	0.002
	(0.34–0.45)	(0.35–0.45)	(0.38–0.50)
Inferior inner	0.40 ± 0.02	0.41 ± 0.02	0.42 ± 0.02	0.007
	(0.37–0.45)	(0.38–0.45)	(0.37–0.48)
Temporal outer	1.10 ± 0.06	1.14 ± 0.06	1.18 ± 0.07	0.0002
	(0.96–1.24)	(1.04–1.23)	(1.06–1.32)
Superior outer	1.21 ± 0.07	1.24 ± 0.05	1.29 ± 0.07	0.0008
	(1.10–1.32)	(1.15–1.33)	(1.15–1.50)
Nasal outer	1.31 ± 0.08	1.35 ± 0.05	1.41 ± 0.08	0.0001
	(1.13–1.45)	(1.23–1.44)	(1.28–1.67)
Inferior outer	1.18 ± 0.07	1.21 ± 0.05	1.27 ± 0.07	0.0007
	(1.03–1.35)	(1.10–1.31)	(0.96–1.24)
Total	6.49 ± 0.30	6.52 ± 0.32	6.94 ± 0.38	0.0001
	(5.99–7.21)	(6.01–7.17)	(6.03–7.67)
Macular thickness (μm)
Foveal minimum	163.3 ± 16.8	156.0 ± 18.5	151.6 ± 20.9	0.04
	(127.3–206.7)	(129.0–208.7)	(122.0–208.0)
Overall average	173.5 ± 40.2	170.2 ± 33.3	170.6 ± 34.8	0.92
	(101.3–232.7)	(102.7–223.0)	(104.3–241.3)
Temporal inner	249.6 ± 11.9	255.2 ± 13.0	261.5 ± 13.0	0.001
	(222.7–268.7)	(224.3–282.3)	(240.7–291.3)
Superior inner	265.8 ± 12.3	270.1 ± 13.0	278.2 ± 15.1	0.001
	(239.0–293.3)	(240.0–292.7)	(252.7–321.7)
Nasal inner	260.4 ± 15.8	264.7 ± 13.9	273.6 ± 16.3	0.003
	(218.0–284.3)	(224.3–288.3)	(240.3–319.3)
Inferior inner	257.3 ± 12.5	260.9 ± 11.4	267.2 ± 14.2	0.008
	(237.3–284.7)	(241.7–286.3)	(236.0–304.0)
Temporal outer	206.9 ± 12.0	213.9 ± 10.8	223.1 ± 12.9	0.0002
	(180.7–234.0)	(195.0–231.0)	(199.3–248.7)
Superior outer	228.0 ± 12.3	232.8 ± 9.5	242.6 ± 13.3	0.0009
	(206.7–249.0)	(217.0–251.0)	(216.3–281.7)
Nasal outer	246.8 ± 14.5	252.9 ± 9.7	264.1 ± 14.9	0.0003
	(212.7–272.7)	(231.7–270.7)	(242.0–314.7)
Inferior outer	222.4 ± 13.2	228.6 ± 9.3	239.5 ± 13.8	0.0007
	(193.7–254.3)	(206.3–246.7)	(214.7–269.0)
Thickness ratio
Superior/inferior outer	1.02 ± 0.04	1.02 ± 0.03	1.01 ± 0.04	0.42
	(0.94–1.18)	(0.94–1.11)	(0.92–1.11)
Temporal/nasal inner	0.96 ± 0.04	0.97 ± 0.03	0.96 ± 0.03	0.57
	(0.90–1.11)	(0.88–1.02)	(0.91–1.03)
Temporal/nasal outer	0.84 ± 0.05	0.82 ± 0.10	0.84 ± 0.03	0.55
	(0.74–0.98)	(0.29–0.91)	(0.76–0.92)

 Data are the mean ± standard deviation (range).

Figure 1.

 

Scatterplots of SE and OCT measurements.

Figure 2.

 

Scatterplots of AL and OCT measurements.

Table 3.

 

Relationship of Macular Volume and Thickness with SE and AL

OCT Measurements	Spherical Equivalent Regression Coefficient β (95% CI)	P	Axial Length Regression Coefficient β (95% CI)	P
Macular volume (mm3)
Fovea	−28.11 (−52.70 to −3.52)	0.03	10.30 (−4.63 to 25.23)	0.17
Temporal inner	20.66 (6.37 to 34.94)	0.005	−18.22 (−26.30 to −10.13)	0.0002
Superior inner	16.71 (5.32 to 28.10)	0.004	−12.38 (−19.01 to −5.74)	0.0004
Nasal inner	17.24 (5.16 to 29.32)	0.006	−13.26 (−20.27 to −6.25)	0.0003
Inferior inner	17.89 (2.89 to 32.88)	0.02	−15.96 (−24.59 to −7.34)	0.0004
Temporal outer	8.31 (4.26 to 12.36)	0.001	−6.86 (−9.08 to −4.64)	0.0002
Superior outer	7.35 (3.03 to 11.67)	0.001	−6.11 (−0.54 to −3.68)	0.0003
Nasal outer	6.82 (3.17 to 10.47)	0.0004	−5.26 (−7.33 to −3.19)	0.0002
Inferior outer	9.40 (5.60 to 13.20)	0.0004	−6.64 (−8.79 to −4.48)	0.0002
Total	1.58 (0.84 to 2.32)	0.0005	−1.20 (−1.62 to −0.79)	0.0001
Macular thickness (μm)
Overall average	−0.03 (−0.01 to 0.006)	0.53	−0.0007 (−0.006 to 0.005)	0.80
Foveal minimum	−0.02 (−0.04 to −0.007)	0.006	0.01 (0.002 to 0.022)	0.02
Temporal inner	0.03 (0.01 to 0.05)	0.005	−0.03 (−0.04 to −0.02)	0.0002
Superior inner	0.03 (0.01 to 0.05)	0.005	−0.03 (−0.04 to −0.01)	0.0006
Nasal inner	0.03 (0.008 to 0.046)	0.006	−0.02 (−0.03 to −0.01)	0.0003
Inferior inner	0.03 (0.004 to 0.05)	0.02	−0.02 (−0.04 to −0.01)	0.0005
Temporal outer	0.04 (0.02 to 0.07)	0.001	−0.04 (−0.05 to −0.02)	0.0002
Superior outer	0.04 (0.02 to 0.06)	0.001	−0.03 (−0.05 to −0.02)	0.0003
Nasal outer	0.04 (0.02 to 0.06)	0.0002	−0.03 (−0.04 to −0.02)	0.0002
Inferior outer	0.05 (0.03 to 0.07)	0.0003	−0.04 (−0.05 to −0.02)	0.0002
Thickness ratio
Superior/inferior outer	−8.46 (−15.80 to −1.11)	0.03	3.99 (−0.44 to 8.43)	0.08
Temporal/nasal inner	−4.20 (−13.77 to 5.38)	0.39	0.28 (−5.46 to 6.02)	0.92
Temporal/nasal outer	0.36 (−4.42 to 5.15)	0.88	−1.11 (−3.96 to 1.74)	0.44

Figure 3.

 

Map of the fovea and four quadrants of the inner and outer macula. *Regression coefficient of macular volume; **regression coefficient of macular thickness as for SE in the multiple linear regression model with macular estimates as the dependent variables and SE, axial length, age, and gender as the independent variables.

The authors thank Angela Cheng for coordinating the SCORM study.