Characteristics and Prevalence of Staphyloma Edges at Different Ages in Highly Myopic Eyes

Abstract

Purpose: The purpose of this study was to determine the characteristics of staphyloma edges in highly myopic eyes and how they progress.

Methods: We conducted a cross-sectional analysis using baseline data and a longitudinal study with follow-up data from 256 patients (447 eyes) with high myopia, with a mean (SD) follow-up of 3.79 (0.78) years. Participants were divided into four age groups: children (<13), youth (13-24), mature (25-59), and elderly (>60). Ultrawide-field swept-source optical coherence tomography was used to analyze staphyloma edges, which were divided into four areas: nasal to the optic disc (OD), superior to the macula, inferior to the macula, and temporal to the macula.

Results: Staphylomas were significantly more prevalent in the mature (42.49%) and the elderly (51.35%) groups than in the children (13%) and youth (9%) groups. Staphyloma edges were predominantly superior to the macula in the mature and elderly groups. In contrast, staphylomas were rare in children and youth, with their edges mainly located nasal to the OD. The edges of staphylomas located superior and temporal to the macula were more likely to be associated with myopic traction maculopathy. During the follow-up period, 11 new staphyloma edges developed primarily in the mature group (64%). Additionally, 12 edges had an increased degree of protrusion over time, with most cases occurring in the mature (75%) group.

Conclusions: The prevalence and location of staphyloma edges show significant variations depending on age. As time progresses, staphyloma edges manifest at distinct sites and increase their protrusion, potentially playing a role in the emergence of fundus complications.

Posterior staphylomas, defined as a posterior outpouching of the ocular wall of the eye with a shorter radius of curvature than the surrounding regions, is a hallmark finding in eyes with pathologic myopia (PM).^1–3 During the development of the human eye, normal eyes increase in size, primarily in the equatorial region.^4–7 In contrast, staphylomas stretch the posterior segment of the eye, encompassing the macular region and the optic disc (OD). The mechanical tension on these tissues caused by the abnormal expansion can cause vision-threatening complications, including myopic maculopathy, myopic traction maculopathy, and damage to the OD.^2,8–12 

Ultra-widefield optical coherence tomography (UWF-OCT), with its scanning range of 23 mm by 5 mm, can record images of the entire extent of staphylomas.^10,13,14 This ability overcame the limitations of previous methods with conventional fundus cameras, which lacked sufficient width for thorough examinations of staphylomas. This is also true for optical coherence tomography (OCT) with a standard field of view of 6- to 9-mm. Furthermore, unlike three-dimensional (3D) magnetic resonance imaging (MRI), UWF-OCT offered a greater time efficiency and was suitable for staphyloma examinations and screening, especially in young children. Importantly, the UWF-OCT findings have been shown to be significantly correlated with the 3D MRI findings of staphylomas.¹³ This indicated that UWF-OCT can be used instead of 3D MRI for the detection and analysis of staphylomas. 

It would be ideal to treat and prevent the development of staphylomas to prevent blindness. Several approaches are being considered, for example, scleral collagen crosslinking, scleral reinforcement,^15–18 and scleral regeneration.^19,20 However, a less invasive and more effective method would be ideal. To accomplish this, knowing how and where staphyloma edges begin and how they progress with increasing time is essential. 

Thus, the purpose of this study was to analyze where staphyloma edges develop and how they progress during aging. In addition, we determined the factors that were significantly associated with the presence of staphylomas. 

Methods

The procedures used in this study conformed to the Declaration of Helsinki and were approved by the Tokyo Medical and Dental University Ethics Committee. Our study consisted of two parts: part 1 = a cross-sectional analysis of the prevalence and locations of the staphyloma edges, and part 2 = a longitudinal study that analyzed the progression of staphyloma edges. 

The patients with high myopia who had undergone UWF-OCT imaging between 2017 and 2022 with at least 2 UWF-OCT images recorded at least 2 years apart were studied. High myopia was defined as a refractive error (Supplementary Methods) with a spherical equivalent less than −6.00 diopters (D) or an axial length (AL) exceeding 26.5 mm at the baseline or the last visit. Eyes with poor-quality OCT images, prior vitreous surgery, and patients with systemic or ocular diseases associated with high myopia or posterior staphylomas were excluded. 

The patients were divided into four groups based on their ages according to the World Health Organization (WHO) classification²¹: children (<13 years), youth (13–24 years), mature (25–59), and elderly (≥60 years). 

Ultra-Widefield Optical Coherence Tomography

UWF-OCT images were acquired using the Xephilio OCT-S1 instrument (Canon, Japan) with an A-scan repetition rate of 100,000 Hz and scan angles of 78 degrees horizontally, 68 degrees vertically, and 55 degrees intraocularly. The images obtained consisted of a 23.0 × 20.0 mm field of view and 5.3 mm depth (Supplementary Methods). 

Posterior Staphylomas

The diagnosis of staphyloma edges using UWF-OCT images was based on the study by Shinohara et al.: a gradual “thick-thin-thick” change in the choroidal thickness from the periphery to the edge of the staphyloma and then to the posterior pole and an inward protrusion of the sclera at the edge of the staphyloma.¹³ We used the images of 12 radial horizontal and vertical scans across the fovea obtained by the UWF-OCT. We determined the staphyloma edges in both horizontal and vertical OCT sections. Adjacent serial sections were examined to confirm the presence of staphyloma edges. Each eye could have up to four edges: nasal to the OD, superior to the macula, inferior to the macula, and temporal to the macula. If at least one staphyloma edge was identified, the eye was classified as having a staphyloma. 

Types of Staphyloma Edges in UWF-OCT Images

The staphyloma edges were further classified into two types according to the protrusion of the overlying retinal pigment epithelium (RPE; Fig. 1). Type 1 edges had OCT features of staphyloma edges, according to earlier studies,¹³ but the overlying RPE did not protrude. In contrast, the type 2 edges had a protrusion of the overlying RPE at the staphyloma edges in addition to the OCT features present in type 1 edges. 

Figure 1.

 

Examples of the two types of staphyloma edges. (A) and (B) Type 1 edge. (A) Horizontal ultra-widefield optical coherence tomography (UWF-OCT) image across the fovea of an 11-year-old girl with a refractive error of −8.5 diopters (D) and an axial length (AL) of 27.0 mm. The OCT image shows a staphyloma edge (arrow) on the nasal side of the optic disc. A gradual “thick-thin-thick” change of the choroidal thickness from the periphery toward the edge of the staphyloma and then to the posterior pole, and the inward protrusion of the scleral-choroidal interface can be seen. However, the line of the retinal pigment epithelium (RPE) does not protrude. (B) Magnified view of image A. The RPE line does not protrude despite the choroidal “thick-thin-thick” pattern and inward protrusion of the choroid-scleral interface (arrow). (C) and (D) Type 2 edge. (C) Horizontal UWF-OCT section across the fovea of a 47-year-old woman with a refractive error of −13.5 D and an AL of 28.7 mm. A staphyloma edge is seen temporal to the macula (arrow). In addition to the choroidal “thick-thin-thick” pattern and the inward protrusion of scleral-choroidal interface, the RPE line also protrudes inwardly. (D) Magnified view of image C.

Thickness of Subfoveal Choroid and Sclera

The thickness of the subfoveal choroid and subfoveal sclera was measured by the measurement tool embedded in the swept-source OCT (Triton, Topcon, Japan; Supplementary Methods) device at the same time as the UWF-OCT. An extremely thin choroid was defined as a subfoveal choroidal thickness <50 µm. 

Scleral Visibility

In healthy eyes, the sclera is usually not visible in the OCT images. A uniform, hyper-reflective scleral structure appears in the OCT images only when the choroid and/or sclera is thin.²² Therefore, we determined the visibility of the scleral outer surface instead of the actual measurement of the scleral thickness to determine if the sclera was thin. The thickness of the sclera was only measured in eyes whose outer scleral surface was visible. 

Statistical Analyses

The descriptive parameters are presented as the means (standard deviations [SDs]). Kruskal-Wallis tests were used to determine the significance of differences in continuous variables. Chi-square tests were used to examine differences in categorical variables. McNemar's test was used to examine paired dichotomous data during the follow-up period. Wilcoxon signed-rank test was used to assess the variations in the number of staphyloma edges during the follow-up period. Binary logistic regression was used to compare several ocular parameters in patients with and without staphylomas. All statistical analyses were performed with SPSS software (version 22.0; IBM-SPSS, Chicago, IL, USA). A P < 0.05 × (2-sided) was taken to be significant. 

Results

Demographics of Participants at the Baseline

The medical records of 636 eyes of 318 patients were initially collected. After applying exclusion criteria, 189 eyes from 95 patients were excluded, leaving 447 eyes from 256 patients included in the study. The baseline characteristics of these patients are presented in Table 1. 

Table 1.

 

Baseline Characteristics in Different Age Groups

 

Axial Length and Refractive Error

The baseline characteristics of the four age groups are presented in Table 1. Statistical analyses revealed significant differences in AL and refractive errors among the four age groups (P < 0.001; see Table 1). The mean AL in both the children and youth groups was significantly shorter than in the mature and elderly groups (all P < 0.001, Kruskal-Wallis tests). Moreover, both the children and youth groups were significantly less myopic than the mature and elderly groups (all P < 0.001, Kruskal-Wallis tests). 

Choroidal Thickness and Scleral Visibility

There were significant differences in the subfoveal choroidal thickness and the visibility of the outer scleral surface in the four age groups (both P < 0.001; see Table 1). The subfoveal choroidal thickness was thinner in the two older groups compared to nearly one-half of the two younger age groups (see Table 1). The proportion of the visible outer scleral surface varied across age groups, with the two older groups having a thinner sclera compared to that of the two younger groups (see Table 1). 

Prevalence of Staphylomas

At the baseline, a posterior staphyloma was present in 180 of 447 eyes (40.27%). More specifically, a staphyloma was present in 13% of the children group, 9% of the youth group, 42.49% of the mature group, and 51.35% of the elderly group. The prevalence of staphylomas was significantly higher in the mature and elderly groups than in the children and youth groups (P < 0.001, Chi-square test; see Table 1). 

Types of Staphyloma Edges

Staphyloma edges were classified into type 1 and type 2 based on their OCT characteristics (see Fig. 1). Of 304 staphyloma edges observed in 180 eyes, 123 (40.46%) were categorized as type 1, and 181 edges (59.54%) were classified as type 2. For the different age groups, type 2 edges were present in 61.93% of the edges in the mature group and in 57.58% in the elderly group, both of which were significantly more frequent than the type 1 edges in these two age groups (P < 0.001 and P = 0.03, respectively, Chi-square tests). The type 1 edges were more common than the type 2 edges in the children group (4/5, 80%) and the youth group (2/3, 67%), although the number of eyes was very low. 

Prevalence of Staphyloma Edges at Different Locations

One hundred eighty eyes had a staphyloma, and there were 304 staphyloma edges. The edges were predominantly situated superior to the macula in 42.43% (P < 0.001; Table 2), followed by temporal to the macula in 30.92%, inferior to the macula in 13.49%, and nasal to the optic disc in 13.16%. In the mature (Fig. 2) and the elderly (Fig. 3) groups, the distribution of staphyloma edges was significantly more frequent in the superior to macula and temporal to macula areas than in the inferior to macula and nasal to the optic disc areas (both P < 0.001, Chi-square tests; see Table 2). The number of staphyloma edges in the children (n = 5) and the youth (n = 3) groups was very low. Most of the staphyloma edges in the children group (80%) and in the youth group (66.7%) were found nasal to the optic disc (Fig. 4). 

Table 2.

 

Prevalence of Staphyloma Edges in Four Areas in Different Age Groups at Baseline

 

Figure 2.

 

Staphyloma edges in two eyes from patients in the mature age group. (A) Fundus photograph of the right eye of a 37-year-old man with a refractive error of -16.5 diopters (D) and an axial length (AL) of 30.7 mm showing tessellated fundus. (B) Horizontal ultra-widefield optical coherence tomography (UWF-OCT) image across the fovea shows a staphyloma edge temporal to the macula (arrow). In addition to the inward protrusion of the sclera, the line of the retinal pigment epithelium (RPE) protrudes slightly anteriorly indicating a type 2 edge. (C) Fundus photograph of the right eye of a 47-year-old woman with a refractive error of −13.75 D and an AL of 28.1 mm showing mild diffuse choroidal atrophy in the macula. (D) Vertical UWF-OCT section across the fovea shows a very steep staphyloma edge superior to the macula (white arrow) and a mild staphyloma edge inferior to the macula (red arrow). Both edges show RPE protrusions indicating type 2 edges. (E) Lateral view of 3D reconstruction of widefield OCT images of the same eye in C showing the steep edge (white arrowhead) along the upper margin and mild edge (red arrowhead) along the lower margin of the staphyloma.

Figure 3.

 

Staphyloma edges in the elderly group. (A) Fundus photograph of the right eye of a 63-year-old man with a refractive error of −11.125 diopters (D) and an axial length (AL) of 26.8 mm showing macular atrophy. The margin of the narrow macular staphyloma is de-pigmented. (B) Arrows indicate ultra-widefield optical coherence tomography (UWF-OCT) scan lines for images C and D. (C) An oblique UWF-OCT image across the fovea shows type 2 staphyloma edge (arrow), which is present in the temporal fundus. (D) Vertical UWF-OCT image across the fovea shows type 2 staphyloma edges superior (red arrow) and inferior to the macula (white arrow). (E) Lateral view of 3D reconstructed optical coherence tomography image shows staphyloma edges along the superior border (red arrowhead) and the inferior border (white arrowhead) of the staphyloma. The inferior edge is steeper than the superior edge. (F) Fundus photograph of the left eye of a 67-year-old woman with an AL of 26.1 mm showing a narrow macular staphyloma as a de-pigmented line. (G) Arrows indicate UWF-OCT scan lines for images H and I. (H) Horizontal UWF-OCT image across the fovea shows a steep type 2 edge in the temporal fundus (arrow). (I) Vertical UWF-OCT image across the fovea shows a type 2 staphyloma edge superior to the macula (arrow). (J) Fundus photograph of the right eye of a 58-year-old woman with a refractive error of −9.75 D and an AL of 26.7 mm showing macular atrophy. The upper edge of the staphyloma appears to be de-pigmented. (K) Arrows indicate the UWF-OCT scan lines for images L and M. (L) Horizontal UWF-OCT image across the fovea of a type 2 staphyloma edge (arrow) located temporal to the macula. (M) Vertical UWF-OCT image across the fovea shows two type 2 edges with one superior (red arrow) and the other inferior (white arrow) to the macula. (N) Lateral view of 3D reconstructed OCT image shows staphyloma edges along the superior border (red arrowhead) and the inferior border (white arrowhead) of a staphyloma. The upper edge is steeper than the lower edge.

Figure 4.

 

Staphyloma edges in the children and youth groups. (A) Fundus photograph of the right eye of an 11-year-old girl with a refractive error of -8.5 diopters (D) and an axial length (AL) of 27.0 mm showing mild tessellation. (B) Widefield fundus image of the same eye showing OCT scan lines for images C and D. (C) and (D) Ultra-widefield optical coherence tomography (UWF-OCT) images showing a staphyloma edge nasal to the optic disc (arrows). The RPE line protrudes slightly suggesting a type 2 edge. (E) Fundus photograph of the right eye of an 11-year-old girl with a refractive error of −7.5 D and an AL of 26.8 mm showing a tessellated fundus. (F) Widefield fundus image of the same eye showing OCT scan lines for images G and H. (G) and (H) UWF-OCT images showing a staphyloma edge nasal to the optic disc (arrows). The RPE line protrudes slightly suggesting a type 2 edge. (I) Fundus photograph of the left eye of a 15-year-old boy with a refractive error of −15.0 D and an AL of 29.2 mm showing peripapillary diffuse atrophy. (J) Widefield fundus photograph of the same eye showing OCT scan lines for images K and L. (K) and (L) Widefield OCT images show staphyloma edge nasal to the optic disc (arrows). Serous retinal detachment is seen in the foveal region.

Staphyloma Edges and Fundus Complications

Significant differences were observed in the ALs, the prevalence of myopic traction maculopathy (MTM), the prevalence of myopic maculopathy equal to or more serious than diffuse atrophy, and the visibility of the sclera among the four staphyloma edge locations (see Table 3). The occurrence of MTM was significantly higher in eyes with staphyloma edges situated superior, lower, or temporal to the macula compared to those located nasal to the optic disc (P = 0.009, Chi-square test). 

Table 3.

 

Comparing the PM Complications and Ocular Parameters in Four Staphyloma Edge Locations at the Baseline

 

Of the 181 type 2 staphyloma edges, 125 (69.06%) had MTM, and among the 123 type 1 staphyloma edges, only 71 (57.72%) had MTM. The presence of MTM was significantly greater in type 2 edges than in type 1 edges (P = 0.04, Chi-square test). 

Binary Logistic Regression of Eyes With Staphyloma Edges

The results of the univariate regression analysis indicated that age, AL, subfoveal choroid thickness, and scleral visibility were significantly correlated with the presence of staphyloma edges (all P < 0.001). The results of multivariate logistic regression analyses indicated that scleral visibility (odds ratio [OR] = 2.76, 95% confidence interval [CI] = 1.57–4.83, P < 0.001), subfoveal choroid thickness (OR = 0.99, 95% CI = 0.985–0.996, P = 0.001), and age (OR = 1.02, 95% CI = 1.005–1.040, P = 0.01) were associated with the presence of staphyloma edges (Table 4). In contrast, the AL was not associated with a significant probability of the presence of a staphyloma edge. 

Table 4.

 

Binary Logistic Regression of Ocular Parameters in Patients With and Without Staphyloma

 

Longitudinal Study

Axial Length and Refractive Error During Follow-Up Period

The mean interval between the first and the last UWF-OCT images was 3.79 ± 0.78 years with a range of 2.0 to 5.7 years. During the follow-up period, the AL, myopic refractive error, and scleral visibility significantly increased in all groups (Table 5). The subfoveal choroidal thickness significantly decreased in all subjects and in each age group (all P < 0.001; see Table 5). 

Table 5.

 

Changes of Prevalence of Ocular Parameters in Different Age Groups During Follow-Up

 

Development of Staphylomas During the Follow-Up Period

During the follow-up period, the incidence of a staphyloma edge significantly increased from 40.27% to 41.61% among all 447 eyes (P = 0.03, McNemar's test; Table 6). Moreover, 6 of the 447 eyes (1.34%) that initially did not have a staphyloma developed a staphyloma. 

Table 6.

 

Longitudinal Changes of Posterior Staphylomas in Different Age Groups

 

The total number of staphyloma edges increased from 304 edges (in 180 eyes) at the baseline to 315 edges (in 186 eyes) at the final visit (Z = −3.32, P = 0.001, Wilcoxon signed-rank test). Additionally, the number of staphyloma edges increased from 197 edges (in 116 eyes) at the baseline to 204 edges (in 118 eyes) at the final visit in the mature group (Z = −2.65, P = 0.008, Wilcoxon signed-rank test). 

A total of 11 new edges developed (Fig. 5), with the most common location being nasal to the optic disc (45%), followed by inferior to the macula (27%), superior to the macula (18%), and temporal to the macula (9%). Newly developed staphyloma edges were more common in the mature group (64%, P = 0.003, Fisher's exact test). 

Figure 5.

 

Development of new staphyloma edges in eyes of the mature group. (A) Fundus photograph of the left eye of a 40-year-old woman with a refractive error of −12.0 diopters (D) and an axial length (AL) of 28.6 mm at the baseline. (B) Fundus photograph of the left eye 3.5 years later. The myopic refractive error has increased to −12.87 D and the AL increased to 28.8 mm. (C) Horizontal ultra-widefield optical coherence tomography (UWF-OCT) image across the fovea at the baseline. The scleral curvature is bowed posteriorly, however, there are no OCT features suggesting staphyloma edges. (D) Horizontal UWF-OCT image across the fovea at the final visit. A type 2 staphyloma edge with a choroidal “thick-thin-thick” pattern, inward scleral protrusion, and slight protrusion of the overlying retinal pigment epithelium can be seen temporal to the macula. (E) Fundus photograph of the left eye of a 44-year-old woman with a refractive error of −13.375 D and an AL of 30.8 mm at the baseline. (F) Fundus photograph of the left eye 4.4 years later. The myopic refractive error increased to −14.25 D and the AL increased to 30.9 mm. (G) Vertical UWF-OCT across the fovea at baseline. Panel I shows a magnified image. There are no OCT features suggesting staphyloma edges. (H) Vertical UWF-OCT section across the fovea at the final visit. Panel J shows a magnified image. An inward protrusion of sclera suggesting a staphyloma edge has formed.

Progression of Staphyloma Edges

At the last visit, 315 edges were observed in the 4 regions of 186 eyes, with 118 (37.46%) classified as type 1 and 197 (62.54%) as type 2 edges. Among the 304 staphyloma edges determined at the baseline, 12 edges (3.9%) had a significant increase in protrusion during the inter-examination interval (Fig. 6). This change was predominantly seen in the mature group with nine edges (75%, P < 0.001, Fisher's exact test). In contrast, two edges were observed in the children group (17%) and one in the youth group (8%; Table 7). None of theeyes of the elderly group had an increased protrusion of the edge during the inter-examination interval. 

Figure 6.

 

Progression of a staphyloma edge during the follow-up period. (A) Fundus photograph of the right eye of a 49-year-old woman at the baseline with a refractive error of −12.75 diopters (D) and an axial length (AL) of 30.1 mm showing a scarred macular neovascularization (MNV) with pigmentation. (B) Fundus photograph of the same eye 3.1 years later. The refractive error did not change but the AL increased to 30.3 mm. Macular atrophy developed around the scarred MNV. (C) Oblique ultra-widefield optical coherence tomography (UWF-OCT) image across the fovea at the baseline shows a slight and gradual protrusion of the sclera superior to the macula suggesting a type 1 staphyloma edge (arrow). MNV is also seen. (D) Oblique UWF-OCT image at the final visit shows an increased protrusion of the staphyloma edge (arrow). Retinoschisis is also present in the lower fundus.

Table 7.

 

Number of Two Types of Staphyloma Edges at the Baseline and the Last Visit

 

Discussion

Our findings indicated that 180 (40.27%) of the 447 highly myopic eyes had a posterior staphyloma. The percentage of staphylomas was significantly lower in the children and youth groups at approximately 11%. The percentage was significantly higher in the mature group at 42.49% and in the elderly group at 51.35%. Although staphylomas were found in children and youth groups, as reported by Tanaka et al.²³ and Chen et al.,²⁴ the results confirmed that staphylomas are significantly more common in the older age groups. 

The most prevalent location for staphyloma edges was superior to the macula, followed by temporal to the macula, nasal to the optic disc, and inferior to the macula. To the best of our knowledge, there has been no prior study that accurately determined the location and characteristics of the staphyloma edges using UWF-OCT. Most earlier studies, even those using UWF-OCT or 3D MRI, primarily reported on the presence and the extent of staphylomas.^8,13,25 Liu et al. analyzed the OCT features of staphyloma edges in detail; however, they did not analyze the location of the edges.²⁶ 

The results of our study indicated that the location of staphyloma edges was not uniform in all four quadrants of the fundus but was more frequent in the superior and temporal regions adjacent to the macula. The higher incidence in these locations warrants further investigations to determine if they are associated with the asymmetric expansion of the ocular wall. 

Our study also showed that staphyloma edges located superior and temporal to the macula were significantly associated with a higher incidence of MTM and longer ALs. Moreover, eyes with type 2 staphyloma edges had a significantly higher incidence of MTM, suggesting that the stretching of the retina as the staphyloma edges protruded affected the morphology of the retina. Further investigations are necessary to explore this relationship in greater detail. 

The underlying mechanism for the site of the development of staphyloma edges was not determined. Chen et al.²⁴ studied children and adolescents and found that the scleral curvature patterns in the vertical OCT sections changed over time and became asymmetrical around the fovea. This coincided with an upward shift of the fovea, indicating that the lower sclera protrudes farther back than the upper sclera. This uneven curvature may have contributed to the formation of the superior staphyloma edges. 

Our findings indicated that there was a significant decrease in choroidal thickness from the youth group to the older groups. Multiple logistic regression analyses established a connection among the thin choroid, increased visibility of the sclera, and a higher incidence of staphylomas, whereas AL showed no significant correlation. The decline in the choroidal thickness between the youth and mature groups may result in the thinning of the inner scleral layer that is dependent on nourishment from choroidal vessels. This could then contribute to the increased irregularities of the scleral curvature and the higher incidence of staphylomas in the older age groups. Further investigations with a larger population are necessary to examine this idea in more detail. 

Six (1.3%) of the 447 examined eyes developed a staphyloma during a mean follow-up of 3.79 ± 0.87 years. This increased the incidence of staphylomas from 40.3% to 41.6%. During this same period, 11 new edges developed. Interestingly, no new staphyloma edges were observed in the elderly group. Given the relatively large number of eyes (n = 111) in the elderly group, we can conclude that the formation of new staphyloma edges tends to occur before reaching the elderly age and up to the mature period. This timeframe aligns with the onset of choroidal and scleral thinning, which typically begins around 25 to 30 years, as our current results show. 

During the follow-up period, we observed an increase in the protrusion of the staphyloma edges in 12 cases. To the best of our knowledge, previous studies have not reported the progression of staphyloma edges, which is probably due to the recent availability of UWF-OCT for detecting such changes. Furthermore, only UWF-OCT, as opposed to fundus photography or 3D-MRI, can reveal the details of staphyloma progression over a short period. 

This study has several limitations. First, our study was conducted at a single-center high myopia clinic, which might have introduced some selection bias. Second, the UWF-OCT images may have exhibited certain levels of shape distortion and magnification effects, particularly in the peripheral fundus. Third, the sample size in the children and youth groups was small, posing challenges for strong statistical conclusions. Future research should prioritize expanded data collection to enhance the statistical power and reliability of findings in these age groups. Fourth, we did not analyze the staphyloma edges located temporal to the optic disc to avoid potential confusion with temporal ridges. This resulted in a lack of data for this specific location. Fifth, the developmental progression of superior and temporal staphyloma edges was not illustrated, as these edges were already present at the baseline in most cases among the older age groups. Sixth, the relatively short observation period may not have fully recorded the long-term development of staphyloma edges. Extended investigations over a more extended time period would provide a more in-depth exploration of the temporal aspects of staphyloma progression, enriching our understanding of its evolution. 

In summary, our findings revealed a higher prevalence of staphylomas in the mature and elderly age groups. This was accompanied by a significant reduction in the choroidal thickness in these age groups. The location of staphyloma edges was significantly different in the different age groups: they were predominantly located nasal to the optic disc in children and superior and temporal to the macula in mature and elderly individuals. Staphyloma edges located superior, temporal, and inferior to the macula have a higher potential to damage the retina. 

Acknowledgments

The authors thank Duco Hamasaki of the Bascom Palmer Eye Institute, University of Miami, FL, for his discussions and thorough manuscript editing without managing data. 

Supported by the Japanese Society for the Promotion of Science (JSPS), Grant No. 19H03808 (KOM); and by the Pioneering Research Initiated by the Next Generation (SPRING) under the Japan Science and Technology Agency (JST) Grant No. JPMJSP2120 (CC). No role was played by the funding organization in the design or conduct of this study. 

Author Contributions: C.C. and K.O.M. conceptualized and designed the study. C.C., Z.W., and S.X. collected and analyzed the data. C.C. drafted the manuscript. S.X., Z.W., H.L., Y.W., J.X., N.N., T.Y., K.U., T.T., K.S., K.K., and K.O.M. edited and critically reviewed the manuscript. All authors approved the final version of the manuscript for submission and agreed to be accountable for their contributions. 

Access to Data and Data Analysis: Kyoko Ohno-Matsui had complete access to all the study data and assumes responsibility for the data's integrity and the accuracy of the data analysis. 

Disclosure: C. Chen, None; Z. Wang, None; S. Xie, None; H. Lu, None; Y. Wang, None; J. Xiong, None; N. Nakao, None; T. Igarashi-Yokoi, None; T. Yoshida, None; K. Uramoto, None; T. Takahashi, None; K. Sugisawa, None; K. Kamoi, None; K. Ohno-Matsui, None