Dome-Shaped Macular Configuration: LongitudinalChanges in the Sclera and Choroid by Swept-SourceOptical Coherence Tomography Over Two Years

ABDALLAH A. ELLABBAN, AKITAKA TSUJIKAWA, YUKI MURAOKA, KENJI YAMASHIRO, AKIO OISHI,SOTARO OOTO, HIDEO NAKANISHI, YOSHIMASA KURODA, MASAYUKI HATA, AYAKO TAKAHASHI, AND

NAGAHISA YOSHIMURA

� PURPOSE: To study longitudinal changes in the poste-rior pole in eyes with dome-shaped macular configurationwithin the staphyloma.� DESIGN: Prospective, longitudinal study.� METHODS: We prospectively examined the maculararea in 35 eyes (26 patients) with dome-shaped macularconfiguration and high myopia (mean sphericalequivalent, L14.83 ± 4.50 diopters) using swept-source optical coherence tomography. Scleral andchoroidal thicknesses were measured at the fovea and at4 parafoveal locations 2000 mm from the foveal center.Height of the macular bulge was measured as well.� RESULTS: During the mean follow-up of 24.8 ±2.5 months, the scleral thickness significantly decreasedat the fovea from 496.1 ± 95.7 mm to 484.7 ± 96.2 mm(P < .001) and at all 4 parafoveal locations (P <.001, respectively). The scleral thinning was asymmetric,with an estimated decrease per year of 5.6 mm at thefoveal center, 11.1 mm superiorly, 12.1 mm inferiorly,10.4mm temporally, and 5.8mmnasally. The ocular con-cavities deepened over time, and mean macular bulgeheight increased from 136.5 ± 60.9 mm to 157.6 ±67.0mm (P< .001). The choroid within the staphylomashowed generalized thinning during follow-up. Meanchoroidal thickness decreased significantly at the foveafrom 28.3 ± 17.2 mm at baseline to 22.9 ± 17.2 mm (P< .001).� CONCLUSIONS: Progressive asymmetric scleral thin-ning occurred in the macular region of eyes withdome-shaped macular configuration. The scleral thin-ning was more pronounced in the parafoveal areathan at the foveal center, resulting in an increase ofthe macular bulge height. (Am J Ophthalmol 2014;-:-–-. � 2014 by Elsevier Inc. All rights reserved.)

Supplemental Material available at AJO.com.Accepted for publication Aug 5, 2014.

From the Department of Ophthalmology and Visual Sciences, KyotoUniversity Graduate School of Medicine, Kyoto, Japan (A.A.E.,A.Tsujikawa, Y.M., K.Y., A.O., S.O., H.N., Y.K., M.H., A.Takahashi,N.Y.); and Department of Ophthalmology, Suez Canal University,Faculty of Medicine, Ismailia, Egypt (A.A.E.).

Inquiries toAkitakaTsujikawa, Department ofOphthalmology andVisualSciences, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto606-8507, Japan; e-mail: tujikawa@kuhp.kyoto-u.ac.jp

0002-9394/$36.00http://dx.doi.org/10.1016/j.ajo.2014.08.006

� 2014 BY ELSEVIER INC.

DOME-SHAPED MACULAR CONFIGURATION IS A

distinctive entity in eyes with high myopia wheremacular curvature shows an inward convexity

within the posterior staphyloma, as opposed to the physio-logic curvature of the posterior pole.1–4 It is now recognizedthat dome-shaped macular configuration is not a rarefinding in highly myopic eyes, with estimated prevalenceof 10.7% in a European study2 and 9.3% in a Japanesestudy.4 Although it was first described as dome-shapedmac-ula,2 later, 3-dimensional (3D) image reconstruction of theposterior pole topography by optical coherence tomogra-phy (OCT) showed that dome-shaped macula may involveseveral patterns: typical dome-shaped convexity,2 the morecommon horizontal band-shaped ridge traversing the pos-terior staphyloma,1 and the rare vertical oval-shapeddome.5

The mechanisms that underlie this unusual tomographicfeature remain unknown. Several hypotheses have beenassumed, such as localized choroidal2 or scleral thick-ening,3 ocular hypotony,6 tangential vitreomacular trac-tion,6 and resistance to staphylomatous deformation.2

Based on 3D reconstructed images, we previously hypothe-sized that dome-shaped macular configuration occurs as apart of the process of asymmetric expansion of the globe,secondary to regional differences in the structural strengthof the sclera at the macula. This may lead to formation of ahorizontal ridge by uneven scleral thinning.1 Because thesclera is the primary determinant of eyeball shape andthe main changes in ocular elongation in high myopiatake place at the scleral coat,7–9 tracking changes in thesclera may help to elucidate the mechanism underlyingthe formation of a dome-shaped macular configuration.With the advances in OCT, the third-generation swept-

source OCT at 1 mm wavelength allows deep penetrationimaging of the choroid and sclera in highly myopiceyes.1,4,10,11 The higher imaging speed allows for densescanning over large areas and subsequent 3D imagereconstruction of posterior pole topography. With the useof this noninvasive OCT technology, it is possible totrack the longitudinal changes in the posterior segmenttopography in vivo. We previously reported markedregional scleral thinning in the superior and inferiorparafoveal areas in eyes with dome-shaped macular

1ALL RIGHTS RESERVED.

configuration within the posterior staphyloma.1 The cur-rent prospective study aims to analyze changes to thechoroid and sclera and morphologic changes in the shapeof the posterior pole over the course of 2 years in eyeswith a dome-shaped macular configuration.

FIGURE 1. Measurement protocol from multi-averaged verti-cal scans obtained with swept-source optical coherence tomogra-phy (OCT) in eyes with dome-shaped macular configuration.Three parameters were measured at the fovea: retinal thickness(blue line), choroidal thickness (black line), and scleral thick-ness (dashed white double arrow). Choroidal (black line) andscleral (dashed white double arrow) thicknesses were measuredat points 2000 mm superior and 2000 mm inferior to the fovea.White arrowheads indicate the outer border of the sclera. Retro-ocular fat can be seen (white asterisk). In the horizontal scan,choroidal and scleral thicknesses were also measured at2000 mm temporal and nasal to the fovea. Macular bulgeheight—the height of the inward bulge of the retinal pigmentepithelium (RPE) (yellow double arrow)—was measured abovethe tangent plane (red dashed line A) at the bottom of the pos-terior staphyloma in the most convex vertical or horizontalscan. To highlight changes at the bottom of the staphylomaover time, a second line (B) was drawn parallel to line A atthe outer surface of the RPE, at the fovea (dashed red line B).The distance between lines A and B is equivalent to macularbulge height. White arrow shows the direction of the OCT scan.

PATIENTS AND METHODS

THIS PROSPECTIVE STUDY WAS APPROVED BY THE ETHICS

Committee at Kyoto University Graduate School of Med-icine and conducted in accordance with the tenets of theDeclaration of Helsinki. The nature of the current studyand the implications of participating in this researchwere explained to all study candidates, after which a writ-ten informed consent was obtained from each participantbefore any study procedures or examinations wereperformed.

In the current study, we prospectively followed 35 eyes(26 patients) with dome-shaped macular configuration us-ing swept-source OCT at Kyoto University Hospital fromthe beginning of October 2010 to the end of January2014. The diagnosis of dome-shaped macular configurationwas based on the presence of an inward bulge of the retinalpigment epithelium (RPE) line, greater than 50 mm on themost convex vertical or horizontal OCT sections above apresumed line tangent to the outer surface of the RPE atthe bottom of the posterior staphyloma in highly myopiceyes. We refer to the latter measurement as ‘‘macular bulgeheight.’’1 The results of 3D OCT imaging performed atbaseline were presented in our previous report.1

High myopia was defined as refractive error of�6.0 diop-ters or more and/or an axial length of 26.5 mm or greater.The exclusion criteria were poor image quality owing tomedia opacity (eg, cataracts or corneal opacity) and/or ahistory of ocular surgery, other than cataract surgery. Theoriginal refractive error was used for eyes that underwentcataract surgery. Curtin’s classification was used to classifyposterior staphylomas based on location and size.12 Wefurther excluded eyes with inferior posterior staphyloma(type V). In the current study, all eyes had a posteriorstaphyloma of type I, II, III, or IX.

All subjects underwent a comprehensive ocular exami-nation, including autorefractometry, best-corrected visualacuity measurement with a 5 m Landolt chart, corneal cur-vature, axial length measurement using partial coherenceinterferometry (IOL-Master; Carl Zeiss Meditec, Jena, Ger-many), slit-lamp examination, intraocular pressure mea-surement, dilated color fundus photography (TRC-NW8For TRC50LX; Topcon Corp, Tokyo, Japan), and swept-source OCT examination. All eyes with macular complica-tions underwent simultaneous fluorescein angiography andindocyanine green angiography, using the SpectralisHRAþOCT (Heidelberg Engineering, Heidelberg,Germany).

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� SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHYAND SCAN PROTOCOLS: The prototype swept-sourceOCT used in the current study has been previouslydescribed1,13–16 and has recently become commerciallyavailable (DRI OCT-1; Topcon Corp, Tokyo, Japan). Allswept-source OCT examinations were performed by atrained examiner after pupillary dilation. For all patients,horizontal and vertical line scans (12 mm) through thefovea were obtained. For each scan, w50 B-scan imageswere obtained and averaged to reduce speckle noise. Thevertical scan was centered on the fovea; the horizontalscan was centered on the midpoint between the foveaand optic disc. 3D imaging datasets were acquired using araster scan protocol of 512 (horizontal) 3 128 (vertical)A-scans per dataset. Each raster scan consisted of 128 B-scans and covered an area of 12 3 8 mm2 or 12 39 mm2, centered on the fovea. In each of the 128 B-scansused for 3D analysis, the RPE line was segmented automat-ically with manual corrections if necessary to construct 3Dimages of posterior pole curvature.

� SCLERAL AND CHOROIDAL THICKNESS MEASUREMENTPROTOCOL: We measured the choroidal and scleral thick-nesses at the center of the fovea and at surrounding paraf-oveal regions at points 2000 mm superiorly, inferiorly,

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FIGURE 2. Longitudinal increases in macular bulge height and deepening of the ocular concavities over time in eyes with a dome-shaped macular configuration. Left eye with high myopia in a 43-year-old man (decimal visual acuity[ 0.1 [Snellen: 20/200], axiallength [ 29.70 mm, and refractive error [ L15.50 diopters). (Top, left) Fundus photograph showing a tessellated fundus withdiffuse atrophic changes of the retinal pigment epithelium (RPE) and a posterior staphyloma. (Middle and Bottom, left) RPE atrophicchanges become more diffuse over time, particularly at the edge of the posterior staphyloma (yellow arrowheads). (Top, right) Avertical-scan swept-source optical coherence tomography (OCT) image shows dome-shaped macular configuration (macular bulgeheight [ 262 mm). (Middle, right) Macular bulge height has increased to 304 mm. Analysis of the OCT images shows 2 outwardconcavities within the staphyloma have increased in depth under the dashed red line (B) as compared to the initial examination. Innerscleral contour is steeper with more posterior bowing (block white arrows). (Bottom, right) At the end of the follow-up period,macular bulge height has increased to 326 mm and ocular concavities appear deeper with steepened contour. White arrows showthe direction of the OCT scan.

temporally, and nasally in the multi-averaged OCT scans(Figure 1), with a built-in caliber tool within the software.Retinal thickness was defined as the distance between thevitreoretinal interface and the outer border of the RPE;choroidal thickness was defined as the distance betweenthe outer border of the RPE line and the chorioscleral inter-face; scleral thickness was defined as the distance betweenthe chorioscleral interface and the outer scleral border.Retinal, choroidal, and scleral thicknesses at the fovealcenter were calculated as the average of the measurementsin the vertical and horizontal OCT images.

We measured the macular bulge height as the height ofthe inward bulge of the RPE above a presumed line tangentto the RPE (dashed red line A) at the fovea within the bot-tom of the posterior staphyloma in the most convex verti-cal or horizontal scans (Figure 1). Macular bulge heightdepends mainly on 2 parameters. One is the difference be-tween scleral and choroidal thicknesses at the fovea andparafoveal regions, and the second is the change in depth

VOL. -, NO. - LONGITUDINAL CHANGES IN DOME-SH

of ocular concavities within the staphyloma. To highlightthese dynamic changes at the bottom of the staphyloma,a second line (B) was drawn parallel to the line (A) tangentto the outer surface of the RPE at the fovea (dashed red lineB, Figures 1–4 and Supplemental Figure, available at AJO.com). The distance between lines A and B is equivalent tothe macular bulge height.The outer scleral border was carefully identified in the

OCT scans from retro-ocular structures such as the Tenoncapsule, episcleral tissue, inferior oblique aponeurosis, andorbital fat. Scleral tissues were identified by their lamellarmorphology, the continuity of the outer surface of thesclera within the raster lines in the vertical and horizontalscans, and high reflectivity values.1,17

In the follow-up examinations, the choroidal and scleralthicknesses were measured again with careful attention tomeasure at the exact location from the initial visit. In 6eyes, the outer border of the sclera was not clearly visibleat the fovea, either at the first visit or at follow-up, which

3APED MACULAR CONFIGURATION

FIGURE 3. Asymmetric scleral thinning at the macular region in dome-shapedmacular configuration. Right eye of a 41-year-old manwith high myopia (decimal visual acuity[ 0.5 [Snellen: 20/40], axial length[ 29.2 mm, and refractive error[L15.70 diopters).(Left column)At the initial examination. (Right column)At the end of the follow-up period. (Top, left) Fundus photograph showing atessellated fundus with diffuse retinal pigment epithelium (RPE) atrophic changes and a scleral thickness map of the right eye. Scleralthickness was measured at the foveal center and 4 parafoveal locations at 2000mm from the foveal center (C[ center; S[ superior,I [ inferior, T [ temporal, N [ nasal). (Middle, left) A vertical-scan swept-source optical coherence tomography (OCT) imageshows dome-shaped macular configuration. The sclera is relatively thicker at the fovea as compared to the areas of outward concavitiessuperiorly and inferiorly (white arrowheads).Macular bulge height was 255mm. (Bottom, left) Horizontal OCT scan shows an almostflat contour of the RPE. The sclera appears thicker at the fovea as compared to parafoveal measurement points at 2000mmnasally andtemporally (white arrowheads). (Top, right)A fundus photograph taken at the end of the follow-up period shows that theRPE atrophicchanges have become more diffuse (yellow arrowheads). Scleral thickness map shows scleral thinning at the 5 locations studied.(Middle, right) A follow-up vertical OCT scan shows increased macular bulge height (281 mm) and scleral thinning at parafoveal lo-cations 2000mm superiorly and inferiorly. By analysis of the OCT images, the dashed red line (B) is seen to traverse the bottom of thestaphyloma at higher level. (Bottom, right) A follow-up horizontal OCT scan shows scleral thinning at the parafoveal locations2000mm temporally and nasally, as compared to the initial scan. The scleral thinning is seen more clearly on the temporal side (whitearrowheads). White arrows show the direction of the OCT scan.

precluded comparison. These eyes were excluded from thestudy. In all recruited subjects, the outer border of the scleraat the fovea and at the 4 parafoveal locations was identifiedclearly at the initial and follow-up visits.

� STATISTICAL ANALYSIS: Statistical analysis was per-formed using SPSS statistical software (version 20; SPSSInc, Chicago, Illinois, USA). All values are expressed asmean 6 standard deviation. The measured visual acuitywas converted to the logarithm of the minimal angle ofresolution (logMAR) for statistical analysis. The pairedt test was used to compare numerical variable means forbaseline and follow-up measurements. Choroidal andscleral thicknesses at various parafoveal regions werecompared to that of the foveal center using 1-way analysisof variance with least significant difference post hoc

4 AMERICAN JOURNAL OF

analysis. A P value of less than .05 was considered to bestatistically significant.

RESULTS

IN THE CURRENT STUDY, 35 EYES (26 SUBJECTS; 6 MEN AND 20

women) with dome-shaped macular configuration wereexamined by swept-source OCT. The mean follow-upperiod was 24.8 6 2.5 months (range: 20–30 months).All patients were Japanese. Table 1 shows the baselinecharacteristics for this patient population. At the initialvisit, mean age was 65.96 12.7 years (range: 41–86 years);mean refractive error was �14.83 6 4.50 diopters(range: �7.5 to �27.0 diopters); mean axial length was

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FIGURE4. Longitudinal changes in scleral thickness andmacular bulge height in dome-shapedmacular configuration. Right eye ofa 63-year-old woman with high myopia (decimal visual acuity [ 0.40 [Snellen: 20/50], axial length [ 30.14 mm, refractiveerror [ L17.50 diopters). (Upper row) Fundus photograph and scleral thickness map at the initial examination (C [ center,S[ superior, I [ inferior, T [ temporal, N [ nasal). Vertical-scan swept-source optical coherence tomography (OCT) imageshows a dome-shaped macular configuration. Measured macular bulge height (yellow double arrow) was 151 mm. (Bottom row)At the end of follow up. Fundus photograph shows progression of the atrophic changes. Scleral thickness map shows scleral thin-ning at the 5 measured locations as compared to the initial examination. A follow-up vertical OCT scan shows scleral thinning atthe area of outward concavities (white arrowheads). Despite the overall scleral thinning, macular bulge has increased to 171 mm.By analysis of the OCT images, the 2 outward concavities are seen to be deeper within the staphyloma under the dashed red (B) line(white block arrows). White arrows show the direction of the OCT scan.

29.86 6 2.16 mm (range: 26.68–34.65 mm). Three-dimensional images revealed a band-shaped ridgetraversing the bottom of the posterior staphyloma in 30eyes (85.7%) and a dome-shaped bulge in 5 eyes(14.3%). In all eyes, macular bulge height was greater inthe vertical scan as compared to the horizontal scan.None of the eyes examined had a vertically oriented ovaldome. Among our patients, choroidal neovascularization(CNV) was seen in 17 eyes (48.6%), serous retinal detach-ment in 2 eyes (5.7%), lamellar hole in 3 eyes (8.6%), full-thickness macular hole in 1 eye (2.9%), extrafoveal schisisin 9 eyes (25.7%), and foveal schisis in 1 eye (2.9%). Fiveeyes with CNV received anti–vascular endothelial growthfactor treatments during the follow-up period.

� LONGITUDINAL CHANGES IN MACULAR BULGEHEIGHT: Swept-source OCT examinations showed the dy-namic changes of the posterior pole over time in patientswith dome-shaped macular configuration. Table 2 showsthe changes in macular bulge height observed over a meanfollow-up period of 2 years. Mean macular bulge heightincreased significantly from 136.5 6 60.9 mm at baselineto 157.6 6 67.0 mm at the end of the follow-up period (P< .001) (Figure 2). Mean macular bulge height hadincreased 21.1mm at the end of the study’s follow-up period.

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� LONGITUDINAL CHANGES IN SCLERAL THICKNESS: Inmost eyes, swept-source OCT allowed us to visualize theouter boundary of the sclera and thus measure scleralthickness. At the initial examination, scleral thicknesswas significantly greater at the fovea compared to all 4parafoveal locations (Figure 3, P < .01, respectively).Table 2 shows the change in scleral thickness during the2-year follow-up period. The sclera became entirelythinner during the follow up period (Figures 3 and 4, P <.001, respectively). Mean scleral thickness at the foveahad decreased from 496.1 6 95.7 mm to 484.7 696.2 mm at the end of the follow-up period (P < .001).During follow-up, the mean decrease in scleral thickness

was 11.4 mm at the fovea, 22.7 mm at 2000 mm superiorly,24.1mm at 2000mm inferiorly, 21.3mm at 2000mm tempo-rally, and 11.8 mm at 2000 mm nasally. The estimateddecrease in scleral thickness per year was 5.6 mm at thefoveal center, 11.1 mm at 2000 mm superiorly, 12.1 mm at2000 mm inferiorly, 10.4 mm at 2000 mm temporally, and5.8mmat 2000mmnasally (Table 3). The decrease in scleralthickness at the fovea was significantly smaller thanwere thedecreases in inferior (P < .001) and temporal (P ¼ .009)scleral thickness. The decrease in nasal scleral thicknesswas significantly smaller than was the decrease in inferior(P ¼ .001) or temporal (P ¼ .012) scleral thickness.

5APED MACULAR CONFIGURATION

TABLE 1. Characteristics of Eyes With Dome-ShapedMacular Configuration

Number of eyes/patients 35/26

Mean follow-up (mo) 24.8 6 2.5 (20 to 30)

Sex, male/female (%) 6/20 (23.1 %/76.9 %)

Age (y)a 65.9 6 12.7 (41 to 86)

Axial length (mm)a 29.86 6 2.16 (26.68 to 34.65)

Refractive error (diopters)a �14.83 6 4.50 (�7.50 to �27.0)

Visual acuity (logMAR)a 0.37 6 0.49 (�0.18 to 1.70)

Intraocular pressure (mm Hg)a 14.5 6 3.0 (9 to 22)

Average corneal

curvature (mm)a7.72 6 0.24 (7.30 to 8.30)

Macular bulge configuration

Band-shaped ridge 30 (85.7%)

Dome-shaped bulge 5 (14.3%)

Type of posterior staphyloma,

eyes (%)

I 12 (34.3%)

II 20 (57.1%)

III 1 (2.9%)

IX 2 (5.7%)

LogMAR ¼ logarithm of minimal angle of resolution.aMeasurement values at the initial visit.

TABLE 2. Longitudinal Changes in Scleral Thickness in EyesWith Dome-Shaped Macular Configuration

At Initial Visit At End of Follow-up P Valuea

Visual acuity (logMAR) 0.37 6 0.49 0.36 6 0.45 .804

Foveal retinal thickness

(mm)

178.6 6 69.9 175.8 6 65.2 .713

Foveal scleral thickness

(mm)

496.1 6 95.7 484.7 6 96.2 <.001

Macular bulge height

(mm)b136.5 6 60.9 157.6 6 67.0 <.001

Scleral thickness in the

parafoveal region

At 2000 mm superiorly

(mm)

280.9 6 87.1 258.2 6 87.2 <.001

At 2000 mm inferiorly

(mm)

263.1 6 68.7 239.0 6 66.7 <.001

At 2000 mm

temporally (mm)

307.6 6 97.3 286.3 6 95.5 <.001

At 2000 mm nasally

(mm)

372.7 6 88.2 360.9 6 90.1 <.001

aPaired t test.bMacular bulge height, height of the inward macular bulge

measured from a presumed line tangent to the outer surface of

retinal pigment epithelium at the bottom of the posterior staphy-

loma on the most convex vertical or horizontal optical coherence

tomography scan.

� LONGITUDINAL CHANGES IN CHOROIDAL THICKNESS:

Table 4 shows the overall decrease in choroidal thicknessobserved during follow-up. Mean choroidal thicknessdecreased significantly at the fovea from 28.3 617.2 mm to 22.9 6 17.2 mm (P < .001). Mean choroidalthickness decreased significantly at all 4 parafoveal loca-tions (P < .05, respectively). The mean decreases inchoroidal thickness during follow-up were 5.4 mm atthe fovea, 5.1 mm at 2000 mm superiorly, 5.3 mm at2000 mm inferiorly, 6.7 mm at 2000 mm temporally,and 2.0 mm at 2000 mm nasally. The estimated decreasein choroidal thickness per year was 2.80 mm at the fovea,2.43 mm at 2000 mm superiorly, 2.59 mm at 2000 mm infe-riorly, 3.27 mm at 2000 mm temporally, and 0.91 mm at2000 mm nasally.

DISCUSSION

SWEPT-SOURCE OCT AT A LONG WAVELENGTH HAS

several potential advantages when imaging highly myopiceyes. It allows deeper penetration into the choroid andsclera with less sensitivity roll-off with depth, reduced scat-tering in tissues, and better visualization of the chorioscl-eral interface.10,11,18 Additionally, it is possible to acquirelong scans spanning the entire length of the staphylomawithout image inversion or mirror-image artifacts.1,19

The high acquisition speed in the current swept-sourceOCT allows for dense scanning and 3D image reconstruc-tion over a wide area of the posterior pole. Our results

6 AMERICAN JOURNAL OF

showed that the sclera generally becomes thinner overtime in the macular region in eyes with dome-shapedmacular configuration; however, the degree of scleral thin-ning is not uniform throughout the posterior pole. The pro-gression of such asymmetric scleral thinning leads to thedome-shaped tomographic appearance. Whereas the scleraasymmetrically thins over time, the height of the macularbulge increases and ocular concavities within the posteriorstaphyloma deepen.Recently, Hayashi and associates20 showed that mean

subfoveal scleral thickness in highly myopic eyes (meanage, 62.3 6 11.3 years; mean axial length, 30.24 61.68 mm) was 284.06 70.4 mm. Clinical and experimentalstudies demonstrated scleral thinning in eyes with highmyopia, especially at the posterior pole.21–25 Imamuraand associates3 previously reported that dome-shaped mac-ular configuration results from localized variation in scleralthickness at the macula. In the current study, the sclera wassignificantly thicker at the subfovea (496.16 95.7mm) andnasal quadrant (372.7 6 88.2 mm) as compared to otherquadrants (280.9–307.6 mm). Scleral thickness values inthe superior, inferior, and temporal quadrants were similaramong our patients and those with similar degrees of highmyopia in previous reports.20

It is still unknown precisely whether the scleral thinningoccurs simply through passive redistribution of the existingcollagen lamellae and extracellular matrix as the eye

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TABLE 3. Decline in Scleral Thickness per Year at VariousMacular Points in Eyes With Dome-Shaped Macular

Configuration

Scleral Thickness Decline

Per Year (mm) P Valuea

Foveal center 5.6 -

At 2000 mm superiorly 11.1 .002

At 2000 mm inferiorly 12.1 <.001

At 2000 mm temporally 10.4 .009

At 2000 mm nasally 5.8 .907

aComparisons with the foveal center (using 1-way analysis of

variance with least significant difference post hoc analysis).

TABLE 4. Longitudinal Changes in Choroidal Thickness inEyes With Dome-Shaped Macular Configuration

At Initial Visit At End of Follow-up P Valuea

Foveal choroidal

thickness (mm)

28.3 6 17.2 22.9 6 17.2 .002

Choroidal thickness in

the parafoveal

region

At 2000 mm superiorly

(mm)

40.0 6 26.9 34.9 6 21.7 .006

At 2000 mm inferiorly

(mm)

32.3 6 20.1 27.0 6 19.8 <.001

At 2000 mm temporally

(mm)

35.7 6 22.2 29.0 6 19.9 .002

At 2000 mm nasally

(mm)

14.2 6 8.8 12.2 6 8.3 .039

aPaired t test.

enlarges25–28 and/or whether an active remodeling processis at work.8,29,30 In eyes with dome-shaped macular config-uration, we speculate that relatively preserved sclera at thehorizontal ridge in conjunction with the optic nerve mayserve like a ‘‘macular pillar’’ to mechanically support themacula of the expanding globe. Notably, the prevalenceof dome-shaped macular configuration in highly myopiceyes is estimated to range from 9.3% to 10.7%.2,4 Thereason for the formation of a horizontal ridge in only aportion of these eyes remains to be determined. Furtherinvestigation of morphologic changes to the optic discmay help to validate this speculation.

Our two years results showed greater scleral thinning inthe superior, inferior, and temporal regions (22.7 mm,24.1 mm, and 21.3 mm) as compared to the subfoveal andnasal regions (11.4 mm and 11.8 mm, respectively). Thecurrent longitudinal data showed that dome-shaped macu-lar configuration represents a novel characteristic of somehighly myopic eyes where the scleral thinning is asym-metric around the macula and not just simple expansion.The ultrastructural mechanism underlying this process isstill unknown. We speculate that there is a difference instructural strength of the sclera at the fovea, possibly owingto regional difference in the organization of the collagenbundles and/or the biomechanical structure of sclerallamellae. So far, the histopathologic nature of dome-shaped macular configuration is still lacking and furtherspeculation into its pathogenic mechanisms is difficult.

Based on 3D image reconstruction of the posterior pole,we previously reported that dome-shaped macular configu-ration has 2 patterns: typical dome-shaped convexity(17.6%) and the more common horizontal band-shapedridge (82.4%) traversing the posterior staphyloma.1

Recently, Caillaux and associates5 showed a third patternwith a vertically oriented oval dome dividing the posteriorstaphyloma into 2 parts, nasal and temporal. However, wedid not observe this configuration in any of our patients.Similarly, Ohsugi and associates4 studied 49 Japaneseeyes with dome-shaped macular configuration, none ofwhich exhibited the vertical oval dome configuration.

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The difference in the ethnicity may explain the variationin the phenotype of dome-shaped macular configuration.Posterior staphyloma formation is a complex process. The

shape of the staphyloma varies among individuals and maychange over time.12,17,31 The staphyloma often becomeevident during the fourth decade of life,31 but the timingof macular bulge formation remains unknown. Curtin previ-ously classified staphylomas into 10 types12; however, thisclassification is rather subjective, based only on the resultsof ophthalmoscopy. So far, there is still an argument whetherdome-shaped macula is a feature of Curtin’s subtypes I and IImodified by the macular bulge,2,5 or a special subtype ofposterior staphyloma,3,4 or is not related to any specifictype of staphyloma. Rather, this phenomenon may berelated to an anatomic or structural change within thesclera and can occur in eyes with any type of staphyloma.1

Based on our findings and the observation that macularbulge configuration may differ between eyes in the same pa-tient,1,5 we support the latter speculation that dome-shapedmacula is an independent scleral change.So far, dome-shaped macular configuration is an OCT-

based diagnosis and it is difficult to make the diagnosis basedon clinical examination. Moreover, there is no exact agree-ment in the definition of dome-shaped macula.1–5,19,32–34 Inthe study herein, we used the numerical data based on themacular bulge height of >50 mm in the most convex scanand expanded the definition to either vertical orhorizontal scan or both to include all possible subtypes.We further excluded eyes with inferior staphylomas (typeV in Curtin’s classification12), which can be diagnosed anddifferentiated by indirect ophthalmoscopy. These eyes oftenhave low to moderate myopia and the staphyloma lies at theinferior region. When the upper edge of the staphylomacrosses the macula, vertical OCT scans depict a convexconfiguration of the macula.14 Long OCT scans that cover

7APED MACULAR CONFIGURATION

a wide area of the posterior pole will be useful to differentiatebetween these conditions.14,19

The current study had some limitations. The number ofeyes with dome-shaped macular configuration was rela-tively small. The duration of follow-up was approximately2 years; little is known about the natural progression ofdome-shaped macular configuration over longer time pe-riods or when the eye starts to develop a macular bulge.All subjects were Japanese, and it is possible that thephenotype of dome-shaped macular configuration mayvary with ethnicity. Choroidal and scleral thicknesseswere measured manually using a built-in caliper owing tothe lack of automated software program.

8 AMERICAN JOURNAL OF

In conclusion, the current study confirms that dome-shaped macular configuration is secondary to asymmetricscleral thinning. In eyes with dome-shaped macular config-uration, scleral thinning was more pronounced in the peri-foveal area than at the macular center, resulting in anincrease of the bulge height. Macular bulge is a useful mea-surement with which to study dynamic changes in the pos-terior pole and may be linked to the incidence of certaincomplications. Understanding the mechanism of ocularexpansion in high myopia may help in finding new thera-peutic approaches. Further longitudinal studies to examinelong-term changes in scleral shape and optic discmorphology are recommended.

ALL AUTHORSHAVE COMPLETED AND SUBMITTED THE ICMJE FORM FOR DISCLOSUREOF POTENTIAL CONFLICTS OF INTEREST.Financial disclosures: N. Yoshimura, Topcon Corp, Tokyo, Japan (Financial Support), Nidek Co, Ltd, Gamagori, Japan (Financial Support, Consultant),Canon Inc, Tokyo, Japan (Financial Support). This study was supported in part by the Japan Society for the Promotion of Science (JSPS), Tokyo, Japan(Grant-in-Aid for Scientific Research, no. 24592625) and by the Japan National Society for the Prevention of Blindness, Tokyo, Japan (Grant-in-Aid,no.116). Contributions of authors: conception and design of the study (A.A.E., A. Tsujikawa, N.Y.); analysis and interpretation (A.A.E., A. Tsujikawa,Y.M., K.Y., A.O., S.O., H.N., Y.K., M.H., A. Takahashi); writing of the article (A.A.E., A. Tsujikawa); critical revision of the article (Y.M., K.Y., A.O.,S.O., H.N., Y.K., M.H., A. Takahashi, N.Y.); final approval of the article (A.A.E., A. Tsujikawa, Y.M., K.Y., A.O., S.O., H.N., Y.K., M.H., A. Takahashi,N.Y.); data collection (A.A.E., A. Tsujikawa, Y.M., K.Y., A.O., S.O., H.N., Y.K., M.H., A. Takahashi, N.Y.).

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Biosketch

Abdallah A. Ellabban, MD, graduated from the Suez Canal University (Egypt) and obtained his MD in 2003. He completed

a residency program and obtained a masters degree in ophthalmology from the Suez Canal University in 2007. Dr Ellabban

is now in a PhD program in the Department of Ophthalmology and Visual Sciences at Kyoto University (Japan). He is

particularly interested in imaging of the deep ocular layers, the choroid and sclera, using swept-source optical coherence

tomography.

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SUPPLEMENTAL FIGURE. Longitudinal changes in scleral thickness and macular bulge height in dome-shaped macular configu-ration with myopic choroidal neovascularization (CNV). Right eye of a 60-year-old woman (decimal visual acuity[ 0.10 [Snellen:20/200], axial length[ 30.9mm, refractive error[L17.00 diopters). (Upper row) Fundus photograph and scleral thickness map atthe time of the initial examination. Vertical-scan swept-source optical coherence tomography (OCT) image shows a dome-shapedmacular configuration and the presence of CNV.Macular bulge height (yellow double arrow) was 64mm. (Bottom row) Fundus imageshows atrophic changes in the retinal pigment epithelium have become more diffuse (yellow arrowhead). The patient received 1injection of intravitreal ranibizumab during follow-up; visual acuity improved to 0.3 (Snellen: 20/67). Scleral thickness map showsscleral thinning at the 5 measured locations at the end of follow-up as compared to the initial examination. Macular bulge height hasincreased to 129 mm. The sclera appears thinner at the outward concavities. The 2 outward concavities are seen to be deeper withinthe staphyloma, and the contour is steeper with more posterior bowing.

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