Purpose
To investigate the morphologic changes along the edge of posterior staphyloma in highly myopic eyes with patchy chorioretinal atrophy and to identify the relationship between retinal thinning and the visual field (VF) defects found in these eyes.
Design
Retrospective, observational case series.
Methods
Twenty eyes (17 patients) with pathologic myopia (myopic refractive error ≥ 8 diopters or an axial length ≥ 26.5 mm) and patchy atrophy along the staphyloma edge were analyzed retrospectively. The VFs were obtained by Goldmann kinetic perimetry.
Results
In the area of patchy atrophy, the inner retinal tissue was very thin or completely absent. Any remnants of the retinal tissue appeared to be adherent to the layer of large choroidal vessels or to the sclera. The mean thickness of the retina at its thinnest point in the area was 51.6 ± 29.0 μm in 20 eyes. The retina was thinner than 50 μm at its thinnest point in 12 (60.0%) of the 20 eyes, and the mean retinal thickness at its thinnest point in these 12 eyes was 32.1 ± 16.0 μm (range, 4 to 49 μm). Nineteen eyes (VF of 1 eye was not determined) had very similar VF findings by Goldmann perimetry, that is, a defect of the sector corresponding to the course of retinal nerve fiber over the patchy atrophy.
Conclusions
The results show that the thickness of not only the outer retina, but also of most of the inner retina, including the nerve fiber layer, is significantly thinner at the staphyloma edge. Such damage to the inner retina along the staphyloma edge causes the VF defects in highly myopic eyes.
Pathologic myopia is characterized by an excessive increase in the axial length and deformity of the globe, including the formation of posterior staphylomas. After the increase in the length and deformity of the globe, various kinds of chorioretinal atrophy develop in and around the macular area. The myopic chorioretinal atrophies are classified into 2 types based on the funduscopic findings: diffuse chorioretinal atrophy and patchy chorioretinal atrophy. Diffuse chorioretinal atrophy is an ill-defined yellowish-white atrophy, and patchy chorioretinal atrophy is a grayish-white lesion with well-defined borders. Fluorescein angiography shows that patchy atrophy has choroidal filling defects resulting from a complete loss of the choriocapillaris. Optical coherence tomographic (OCT) images show a loss of photoreceptors, retinal pigment epithelium (RPE), and inner choroid in the area of patchy atrophy in the macular area. Thus, the inner retina appears to be attached directly to the sclera. Despite the loss of outer retinal tissue, the inner retinal layer is maintained in the area of patchy atrophy.
We reported that patchy atrophy can be subdivided into 3 different types according to its location or origin based on the findings in a long-term natural course study ( Supplemental Figure 1 , available at AJO.com ). One type of patch atrophy develops as a circular lesion in eyes with advanced diffuse chorioretinal atrophy. The second type of patchy atrophy progresses by an increase in the width of the lacquer cracks. This type of atrophy has a horizontal or vertical orientation with less severe diffuse atrophy. The third type of patchy atrophy develops along the edge of a posterior staphyloma.
The morphologic features of patchy atrophy along the staphyloma edge have not been studied in detail by OCT. This is probably because this type of patchy atrophy develops away from the macular area, and thus does not affect the central vision. In addition, obtaining clear OCT images away from the macula is difficult and requires skill and experience.
In long-term studies of patients in the High Myopia Clinic at Tokyo Medical and Dental University, we examined the area of patchy atrophy along the staphyloma edge by OCT and found an extreme thinning of the inner retina, including the nerve fiber layer. In some cases, almost the entire retina seemed to be absent. Thus, the purpose of this study was to analyze the OCT findings of the retina in the area of patchy atrophy along the staphyloma edge and also to determine the correlation of such retinal changes and the visual field (VF) findings in these eyes.
Methods
This was a retrospective observational case series. Approval was obtained from the Ethics Committee of the Tokyo Medical and Dental University to perform this retrospective study, and the procedures used during the examinations conformed to the tenets of the Declaration of Helsinki. Written informed consent was obtained from all participants not only for the examination, but also for the use of all data collected for future investigations.
OCT examinations along the staphyloma edge had been performed between October 5, 2012, and April 5, 2013, in the High Myopia Clinic of the Tokyo Medical and Dental University, and these data were analyzed retrospectively. The OCT examination was performed through a dilated pupil using the Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, California, USA). The retinal thickness was measured using the built-in software of the OCT instrument. In the OCT examination, 5 horizontal and vertical scan lines were recorded over the area of the patchy atrophy along the staphyloma edge by 1 of the authors (Y.T.).
All of the participants underwent a comprehensive ocular examination, including the measurement of refractive error (spherical equivalent), measurement of axial length with the IOL Master (Carl Zeiss Meditec, Jena, Germany), and fundus photography. Fundus images and fundus autofluorescence images were obtained with the Optos Optomap Panoramic 200A imaging system (Optos PLC, Dunfermline, United Kingdom) or with a fundus camera (TRC-50DX; Topcon, Tokyo, Japan). The presence and types of staphyloma were determined by the presence and the extent of pigmentary abnormalities along the assumed edge of a staphyloma in the eyes examined by Optos device. The pigmentary abnormalities of our earlier study were well correlated with the eye shape determined by 3-dimensional magnetic resonance imaging. For the eyes without Optos data, the presence and the types of staphyloma were determined by stereoscopic fundus examinations. The types of staphylomas were classified into 6 types according to our earlier study : wide macular, narrow macular, peripapillary, nasal, inferior, and others.
The VFs were determined by Goldmann kinetic perimetry, and the VFs were recorded with the refractive errors corrected by disposable soft contact lenses. The astigmatic refractive errors were corrected by spectacles if they were more than 1 diopter (D) with the wearing soft contact lenses.
Results
Between October 5, 2012, and April 5, 2013, a total of 1121 patients with pathologic myopia visited the High Myopia Clinic. The definition of pathologic myopia was a refractive error (spherical equivalent) of more than −8.00 D or an axial length of more than 26.5 mm. The mean age of the 1121 patients was 50.2 ± 18.3 years, with a range of 6 to 84 years. After excluding 21 non–highly myopic eyes of the 21 patients with unilateral high myopia, the mean axial length was 29.6 ± 2.1 mm with a range of 26.7 to 35.3 mm in the 2221 eyes of 1121 patients. A posterior staphyloma was found in 989 (44.5%) of the 2221 highly myopic eyes. Twenty eyes of 17 patients with pathologic myopia had patchy atrophy along the staphyloma edge, which was 20 (2.0%) of the 989 highly myopic eyes with a staphyloma and 20 (0.9%) of the 2221 highly myopic eyes with or without a staphyloma.
The mean age of the 17 patients was 65.5 ± 10.7 years, with a range of 50 to 86 years. The mean refractive error of 12 eyes (8 eyes were pseudophakic) was −17.1 ± 2.6 D, with a range of −9.5 to −22.0 D. The mean axial length was 30.5 ± 1.9 mm, with a range of 27.4 to 34.1 mm. The types of posterior staphyloma were wide macular in 6 eyes (30.0%), narrow macular in 12 eyes (60.0%), peripapillary in 1 eye (5.0%), and inferior in 1 eye (5.0%).
A patchy atrophy along the staphyloma edge was observed funduscopically as a horizontally long, well-demarcated whitish lesion and as a uniform are of hypo-autofluorescence in the fundus autofluorescence images ( Figures 1, 2, and 3 ). The patchy atrophy was present along the upper temporal edge of the staphyloma in 14 eyes and along the lower temporal edge in the other 6 eyes.
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