To analyze the morphologic features of peripapillary staphylomas associated with high myopia by swept-source optical coherence tomography (OCT).
Highly myopic patients (refractive error >8.0 diopters or axial length >26.5 mm) with a peripapillary staphyloma who had undergone swept-source OCT were studied. The non–highly myopic fellow eyes in patients with unilateral high myopia were also studied. The presence of a peripapillary staphyloma was determined by stereoscopic ophthalmoscopic examinations. The OCT features of the peripapillary staphylomas and other peripapillary lesions were evaluated.
Twenty-five eyes of 16 patients were studied. Twenty-two eyes were highly myopic and the remaining 3 eyes of the patients with unilateral high myopia were non–highly myopic. A peripapillary staphyloma was seen in the swept-source OCT images as a gently sloping excavation around the optic disc in all 25 eyes. The posterior sclera in the area of a peripapillary staphyloma was observed to bow posteriorly, with the local curvature steeper than the curvature of the adjacent scleral regions. The sclera at the edge of a peripapillary staphyloma appeared to be elevated inward from the surrounding sclera, and the choroid at the staphyloma edge appeared to be compressed and thinned. A peripapillary intrachoroidal cavitation was a frequent complication and was found in 13 eyes with a peripapillary staphyloma (52.5%).
Swept-source OCT can detect the slight changes of the sclera and choroid in the area of a peripapillary staphyloma, and we recommend its use in determining the presence of a peripapillary staphyloma.
A posterior staphyloma is an important feature of eyes with pathologic myopia. Curtin classified posterior staphylomas in eyes with pathologic myopia into 10 different types. The peripapillary staphyloma (type 3) was reported to be a rare type of posterior staphyloma, and its incidence was approximately 1.5% of all staphylomas. Other investigators have reported that the incidence of a peripapillary staphyloma was 4.3% and 6.9% of highly myopic eyes based on Curtin’s classification. Curtin’s classification was made by ophthalmoscopic observations and chart drawings, so the findings are considered to be relatively subjective.
To analyze an eye deformity caused by a staphyloma more objectively, Moriyama and associates performed 3-dimensional magnetic resonance imaging (3D MRI). Later, Ohno-Matsui used a combination of 3D MRI and ultra-wide-field fundus imaging and classified posterior staphylomas into 6 different types according to their size and location (wide macular, narrow macular, peripapillary, nasal, inferior, and other). Ohno-Matsui reported that peripapillary staphylomas were observed in only 5 of 198 eyes (2.5%). However, because the outpouching of a peripapillary staphyloma can be slight and narrow, eyes with a peripapillary staphyloma had a nasally distorted shape that was different from other types of a staphyloma, and they did not show clear outpouching of the globe in the 3D MRI images. Thus, the diagnosis of peripapillary staphylomas was mainly based on the presence of pigmentary abnormalities around the optic disc in the wide-field fundus images.
Recent advances in optical coherence tomography (OCT) have enabled clinicians to investigate the structure of the fundus in more detail. Current swept-source OCT instruments use a longer central wavelength, generally in the 1 μm range, which has improved their ability to penetrate deeper into tissues than the conventional spectral-domain OCT instruments. Owing to its deep penetration, swept-source OCT can obtain images of deeper tissues, such as the choroid, sclera, and optic nerve, more clearly. Although the scan length of currently available OCT instruments is still limited, we believed that staphylomas in a restricted area, such as peripapillary staphylomas, might be suitable for detection by swept-source OCT.
A PubMed search on March 2016 using the keywords “peripapillary staphyloma” or “type 3 staphyloma” and “optical coherence tomography” detected 5 articles; however, 4 articles were analyses of congenital peripapillary changes, and only 1 article was a report about a peripapillary staphyloma associated with high myopia. In addition, the OCT features of peripapillary staphylomas have not been examined in detail in any of the earlier studies. Therefore, reports about the morphologic characteristics of a peripapillary staphyloma associated with high myopia are limited.
The purpose of this study was to determine the morphologic characteristics, especially the sclera and choroid, of peripapillary staphylomas in the swept-source OCT images.
The procedures used in this study adhered to the tenets of the Declaration of Helsinki, and they were approved by the Ethics Committee of Tokyo Medical and Dental University. An informed consent was obtained from each of the subjects to perform all of the examination procedures.
Highly myopic patients who visited the High Myopia Clinic at Tokyo Medical and Dental University between February 2, 2015 and September 25, 2015 were analyzed for the presence of a peripapillary staphyloma. High myopia was defined as a myopic refractive error (spherical equivalent) greater than 8.0 diopters (D) or an axial length >26.5 mm. For the patients with unilateral high myopia, the non–highly myopic fellow eyes were also studied in the same way. The diagnosis of a peripapillary staphyloma was based on the detection of an excavation and edge around the optic disc by stereoscopic fundus examination with agreement of 2 of the authors (K.S. and K.O.-M.). The staphyloma was also identified by the presence of pigmentary changes along the presumed edge of the staphyloma as reported by Ohno-Matsui. The exclusion criteria included a lack of OCT images centered on the optic disc and a history of vitreoretinal surgery. The patients with a history of a reduction of the best-corrected visual acuity (BCVA) and a history of fundus abnormalities in the papillary and peripapillary region in childhood were excluded.
All of the patients underwent comprehensive ophthalmologic examinations, including measurements of the refractive error (spherical equivalent) and axial length with the IOLMaster (Carl Zeiss Meditec, Jena, Germany) and stereoscopic fundus examination with pupillary dilation. Swept-source OCT (DRI OCT-1; Topcon Corp, Tokyo, Japan) was performed by radial scans with 12 equal meridian scans centered on the optic disc. This swept-source OCT system has an A-scan repetition rate of 100 000 Hz, and its light source operates in the 1 μm wavelength region. The light source is a wavelength tunable laser centered at 1050 nm with a 100 nm tuning range. The scan line length was 6 or 9 mm, and 32 B-scan images were averaged to improve the signal-to-noise ratio. The OCT features of peripapillary staphylomas were analyzed, and other peripapillary lesions such as intrachoroidal cavitations (ICCs) were also evaluated.
Clinical and Fundus Features of Patients With Peripapillary Staphyloma
Thirty-four eyes of 21 patients were diagnosed ophthalmoscopically as having a peripapillary staphyloma. Among them, 9 eyes (5 patients) were excluded: 8 eyes (4 patients) owing to a lack of OCT images centered on the optic disc and 1 eye (1 patient) owing to a history of vitreoretinal surgery. There were no patients who were suspected to have a congenital staphyloma. In the end, 25 eyes of 16 patients were enrolled and the swept-source OCT images of these cases were examined in more detail. There were 2 men and 14 women with a mean age of 68.3 ± 6.6 years and a range of 55–78 years. In the stereoscopic fundus examinations, a peripapillary staphyloma was observed as a slight excavation around the optic disc, and the edge of the excavation had pigmentary abnormalities ( Figure 1 ) as reported. In all cases, the peripapillary staphyloma extended beyond the margin of the peripapillary conus; thus it differed from the excavation of the peripapillary gamma zone ( Figure 1 ). The mean refractive error (spherical equivalent), except for the pseudophakic eyes, was −9.0 ± 3.3 D with a range of −1.5 to −13.0 D. The mean axial length was 27.6 ± 1.6 mm with a range of 22.5–30.5 mm.
Among the 16 patients, 9 had a peripapillary staphyloma bilaterally and 7 had a peripapillary staphyloma unilaterally. Of the 9 patients who had a peripapillary staphyloma bilaterally, 8 patients had bilateral high myopia and 1 patient had unilateral high myopia. Of the 7 patients who had a peripapillary staphyloma unilaterally, 4 patients had bilateral high myopia and 3 patients had unilateral high myopia. Therefore, in the total of 25 eyes with a peripapillary staphyloma, 22 eyes were highly myopic and the remaining 3 eyes were not highly myopic. The mean age was 68.2 ± 7.0 years with a range of 55–78 years in the patients with high myopia and 70.7 ± 4.5 years with a range of 66–75 years in those without high myopia. The mean axial length was 28.1 ± 1.0 mm with a range of 26.8–30.5 mm in the eyes with high myopia and 24.0 ± 1.3 with a range of 22.5–25.0 mm in the eyes without high myopia. The clinical characteristics of the eyes with a peripapillary staphyloma are shown in the Table .
|Characteristic||Eyes With Peripapillary Staphyloma|
|Highly Myopic (N = 22)||Not Highly Myopic (N = 3)|
|Refractive error, mean ± SD (range)||−10.0 ± 2.0 (−5.75 to −13.0)||−3.5 ± 2.8 (−1.5, IOL, −5.5)|
|Axial length, mean ± SD (range)||28.1 ± 1.0 (26.8–30.5)||24.0 ± 1.3 (22.5, 24.4, 25.0)|
|ICC, n (%)||12 (54.5%)||1 (33.3%)|
|Type of myopic conus||21 (95.5%)||2 (66.7%)|
|Annular||8 (36.4%)||2 (66.7%)|
Optical Coherence Tomographic Features of Peripapillary Staphyloma
In the OCT images centered on the optic disc, a gently sloping excavation was clearly observed around the optic disc in all 25 eyes ( Figures 2 and 3 ). This excavation was observed at least 180 degrees around the optic disc in all 25 eyes. The posterior sclera in the area of the peripapillary staphyloma was seen to bow posteriorly, with the local curvature steeper than that of the adjacent scleral regions. Similar changes of the scleral curvature have been reported in the area of a peripapillary ICC by Spaide and associates. However, the curvature of the sclera at the edge of the peripapillary staphyloma appeared to be elevated inwardly, and the choroid at the site of the staphyloma edge appeared to be compressed and thinned ( Figures 2 and 3 ).