Assessing reproducibility and the effects of demographic variables on the normal macular layers using the Spectralis SD-OCT

Figures & data

Figure 1 The ETDRS sectors at the posterior pole. The center circle is 1 mm, the inner circle is 1–3 mm and the outer circle is 3–6 mm.

Note: The green line corresponds to the cut section shown on the B scan.

Figure 2 Retinal layers that were quantified are shown.

Table 1 General characteristics

Age group (Y)	Patients (N)	Gender (M/F)	Refractive error (D)	IOP (mmHg)	Axial length (mm)
20–29	55	27/28	−0.6± 1.5	14.3±2.5	23.4±1.0
30–39	64	21/43	−0.5± 1.2	15.1 ±3.2	23.7±1.7
40–49	41	24/17	−0.0± 1.3	15.5±2.7	23.5±0.9
50–59	42	24/18	1.2± 1.0	14.2±2.9	23.1±0.7
60+	40	30/10	0.9± 1.1	15.4±3.l	23.2±0.8
Total	242	126/116	−0.0± 1.5	14.9±2.9	23.5±1.2

Note: Data presented as mean ± SD.

Abbreviations: Y, years; N, number; M, male; F, female; D, diopter; IOP, intraocular pressure; mmHg, millimeter of mercury; mm, millimeter.

Table 2 Individual retinal layer thickness stratified by the ETDRS sectors

Layer (µm)	Foveal	Inner circle				Outer circle
		Upper	Lower	Nasal	Temporal	Upper	Lower	Nasal	Temporal	Mean
Single layers
RNFL	N/A	24.5±3.3	26.4±3.8	21.3±1.9	17.7± 1.1	37.4±5.7	39.6±7.0	48.7±7.0	18.8±1.9	27.4±3.7
GCL	N/A	51.9±4.3	51.1 ±4.8	50.1 ±5.2	46.9±4.9	33.7±3.1	32.0±3.5	38.0±3.3	34.2±3.7	39.1 ±4.0
IPL	N/A	40.2±2.9	40.1 ±3.3	40.9±3.0	40.4±3.2	27.0±2.7	25.7±2.9	29.1±2.7	30.6±2.6	32.6±5.8
INL	N/A	41.8±3.5	41.0±3.7	40.8±3.6	38.0±2.8	32.1 ±2.5	31.3±3.0	34.6±2.7	32.5±2.2	34.5±3.1
OPL	24.3±5.3	37.2±8.6	31.4±6.2	34.3±9.0	30.0±4.3	27.6±2.7	26.3±2.5	29.0±2.5	26.7±1.8	29.5±6.1
ONL	87.2±3.5	61.7±11.6	65.1 ±9.9	69.2±10.4	68.5±8.9	55.9±7.0	50.4±6.4	54.6±7.3	54.0±6.4	63.0±11.0
RPE	16.7±2.2	15.1±1.9	15.1 ±5.6	15.3±1.7	14.3±1.6	13.1±1.3	12.8±2.3	13.1 ±2.6	12.6±1.5	14.2±2.3
Combined layers
IRL	172.2±19.1	256.6±14.8	254.7±17.2	256.0±20.2	242.1±3.1	213.9±13.0	204.8±14.6	233.6±14.9	197.5±13.2	225.7±15.5
PL	88.0±4.4	80.0±3.3	78.9±2.9	81.5±3.1	80.0±3.1	77.3±2.5	75.7±2.5	76.7±4.0	76.4±2.5	79.4±3.1
TRT	259.9±19.3	337.3±14.8	334.7±14.7	334.7±15.6	322.5±15.6	290.3±23.5	281.4±16.7	310.9±18.9	276.3±21.9	305.6±17.8

Notes: The values are mean ± SD. Center, fovea, inner circle 1–3 mm from fovea; outer circle 3–6 mm from fovea.

Abbreviations: GCL, ganglion cell layer; INL, inner nuclear layer; IPL, inner plexiform layer; IRL, inner retinal layer; OPL, outer plexiform layer; ONL, outer nuclear layer; PL, photoreceptor layer; RNFL, retinal nerve fiber layer; RPE, retinal pigment epithelium; TRT, total retinal thickness.

Table 3 The effect of gender on individual retinal layers

Layer (µm)	Total (N=242)	Men (n=126)	Women (n= 116)	P-value
Single layers
Retinal nerve fiber layer
Whole	27.4±2.5	27.8±2.7	27.0±2.4	0.030
Inner circle	22.5± 1.6	23.0±1.8	22.1±1.5	<0.001
Outer circle	36.2±4.5	36.4±4.7	36.0±4.3	0.489
Ganglion cell layer
Whole	39.1 ±2.9	39.7±3.1	38.6±2.8	0.006
Inner circle	49.5±4.2	51.0±4.3	49.1±4.1	0.002
Outer circle	34.4±2.9	34.5±3.0	34.4±2.8	0.739
Inner plexiform layer
Whole	32.6±2.1	33.1±2.1	32.2±2.2	0.006
Inner circle	40.4±2.7	41.0±2.7	39.8±2.8	0.002
Outer circle	28.0±2.4	28.1 ±2.4	28.0±2.4	0.738
Inner nuclear layer
Whole	34.5±2.1	34.8±2.0	34.2±2.3	0.100
Inner circle	40.3±2.8	40.8±2.5	39.9±3.1	0.091
Outer circle	32.6±2.2	32.5±2.2	32.7±2.3	0.385
Outer plexiform layer
Whole	30.1 ±2.5	30.3±2.5	30.0±2.5	0.419
Inner circle	32.8±3.7	33.1±3.7	32.6±3.8	0.311
Outer circle	27.4± 1.6	27.4± 1.6	27.4± 1.7	0.869
Outer nuclear layer
Whole	59.9±6.6	60.6±6.1	59.3±7.1	0.172
Inner circle	66.1 ±7.7	67.0±7.4	65.3±8.1	0.130
Outer circle	53.7±6.1	54.2±5.7	53.3±6.6	0.294
Retinal pigment epithelium
Whole	13.8± 1.4	14.0±1.5	13.7±1.4	0.162
Inner circle	14.8± 1.6	15.0±1.7	14.7±1.5	0.142
Outer circle	12.9± 1.6	13.0±1.6	12.8± 1.6	0.291
Combined layers
Inner retinal layer
Whole	232.4±11.4	234.2±11.1	230.7±11.7	0.030
Inner circle	252.4±12.8	255.6±11.8	249.3±13.8	0.001
Outer circle	212.4±12.3	212.8±12.2	212.1±12.4	0.689
Photoreceptor layer
Whole	78.3±2.4	79.0±2.5	77.7±2.4	<0.001
Inner circle	80.1±2.8	80.7±2.8	79.5±2.9	0.003
Outer circle	76.6±2.3	77.3±2.4	75.9±2.3	<0.001
Total retinal thickness
Whole	311.4±13.2	314.5±13.0	308.4±13.4	0.001
Inner circle	333.1±13.6	337.3±13.0	328.9±14.2	<0.001
Outer circle	289.8±15.7	291.7±16.1	287.9±15.4	0.080

Notes: The values are in mean ± SD. Center, fovea, inner circle 1–3 mm from fovea; outer circle 3–6 mm from fovea.

Table 4 The effect of age on individual retinal layers

Layer (µm)	Regression equation	R-value	P-value	Adjusted P-valuea
Single layers
Retinal nerve fiber layer
Whole	27.5–0.00aage	0.004	0.849	0.909
Inner circle	22.0+0.01aage	0.039	0.266	0.243
Outer circle	37.3–0.02aage	0.029	0.397	0.448
Ganglion cell layer
Whole	42.1–0.07aage	0.078	0.001	0.001
Inner circle	53.1–0.08aage	0.191	<0.001	<0.001
Outer circle	38.0–0.09aage	0.284	<0.001	<0.001
Inner plexiform layer
Whole	34.6–0.05aage	0.079	0.001	0.001
Inner circle	42.2–0.04aage	0.185	<0.001	<0.001
Outer circle	30.9–0.07aage	0.269	<0.001	<0.001
Inner nuclear layer
Whole	35.1–0.01aage	0.028	0.224	0.167
Inner circle	40.4–0.00aage	0.000	0.990	0.810
Outer circle	35.1–0.06aage	0.274	<0.001	<0.001
Outer plexiform layer
Whole	29.9–0.01aage	0.022	0.332	0.366
Inner circle	33.8–0.02aage	0.041	0.232	0.253
Outer circle	28.0–0.01aage	0.073	0.036	0.035
Outer nuclear layer
Whole	64.3–0.03aage	0.025	0.281	0.196
Inner circle	66.5–0.00aage	0.010	0.774	0.616
Outer circle	57.7–0.10aage	0.183	<0.001	<0.001
Retinal pigment epithelium
Whole	14.0+0.00aage	0.028	0.234	0.309
Inner circle	14.3+0.01aage	0.092	0.008	0.011
Outer circle	12.9–0.00aage	0.000	0.994	0.859
Combined layers
Inner retinal layer
Whole	232.9–0.18a age	0.072	0.002	0.001
Inner circle	256.4–0.10a age	0.074	0.034	0.023
Outer circle	226.8–00.37a age	0.239	<0.001	<0.001
Photoreceptor layer
Whole	80.5–0.02aage	0.076	0.001	0.001
Inner circle	81.5–0.03aage	0.139	<0.001	<0.001
Outer circle	77.2–0.01aage	0.067	0.055	0.057
Total retinal thickness
Whole	314.9–0.23a age	0.090	<0.001	<0.001
Inner circle	340.6–0.19a age	0.150	<0.001	<0.001
Outer circle	304.8–0.38a age	0.200	<0.001	<0.001

Notes:

a Adjusted for axial length. Center, fovea, inner circle 1–3 mm from fovea; outer circle 3–6 mm from fovea.

Table 5 The effect of axial length on individual retinal layers

Layer (µm)	Regression equation	R-value	P-value	Adjusted P-valuea
Single layers
RNFL	20.9+0.27a axial length	0.029	0.217	0.221
GCL	39.2–0.00a axial length	0.000	0.988	0.824
iPL	34.3–0.06a axial length	0.011	0.637	0.492
INL	42.9–0.35a axial length	0.060	0.010	0.008
OPL	26.6+0.12a axial length	0.025	0.272	0.298
ONL	87.6–1.04a axial length	0.078	0.001	0.001
RPE	17.1–0.12a axial length	0.066	0.004	0.005
Combined layers
IRL	250.2–1.03a axial length	0.041	0.079	0.051
PL	78.4+0.04a axial length	0.011	0.621	0.769
TRT	323.2–0.74a axial length	0.028	0.218	0.139

Notes:

a Adjusted for age. Center, fovea, inner circle 1–3 mm from fovea; outer circle 3–6 mm from fovea.

Abbreviations: GCL, ganglion cell layer; INL, inner nuclear layer; IPL, inner plexiform layer; IRL, inner retinal layer; OPL, outer plexiform layer; ONL, outer nuclear layer; PL, photoreceptor layer; RNFL, retinal nerve fiber layer; RPE, retinal pigment epithelium; TRT, total retinal thickness.

Table 6 The reproducibility individual retinal layer measurements

Layer (µm)	Coefficient of variation				Intraclass correlation coefficient
	Inner	Outer	Whole	Center	Inner	Outer	Whole	Center
Single layers
RNFL	0.038	0.030	0.039	0.038	0.958	0.992	0.994	0.918
GCL	0.019	0.022	0.023	0.045	0.973	0.960	0.996	0.963
IPL	0.019	0.019	0.021	0.035	0.909	0.971	0.990	0.925
INL	0.031	0.020	0.032	0.066	0.883	0.951	0.981	0.885
OPL	0.078	0.033	0.059	0.087	0.731	0.839	0.830	0.802
ONL	0.035	0.022	0.029	0.028	0.925	0.967	0.976	0.947
RPE	0.046	0.029	0.040	0.060	0.805	0.857	0.903	0.900
Combined layers
IRL	0.007	0.007	0.007	0.010	0.995	0.994	0.996	0.974
PL	0.009	0.006	0.008	0.014	0.937	0.942	0.973	0.870
TRT	0.006	0.006	0.006	0.005	0.924	0.990	0.990	0.989

Abbreviations: RNFL, retinal nerve fiber layer; GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; RPE, retinal pigment epithelium; IRL, inner retinal layer; PL, photoreceptor layer; TRT, total retinal thickness.