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Peripapillary Changes Detected by Optical Coherence Tomography in Eyes with High Myopia
Peripapillary Changes Detected by Optical Coherence Tomography in Eyes with High Myopia Noriaki Shimada, MD, Kyoko Ohno-Matsui, MD, Akinobu Nishimuta, MD, Takashi Tokoro, MD, Manabu Mochizuki, MD Objective: To investigate the morphologic alterations around the optic disc by optical coherence tomography (OCT) in eyes with high myopia. Design: Observational case series. Participants: One hundred twenty-seven eyes (69 patients) with high (ⱖ⫺8.00 diopters [D]) myopia were included. In addition, 46 emmetropic (⫹1.00 to ⫺1.00 D) eyes and 40 eyes with low (⬍⫺6.00 D) myopia were examined as controls. Methods: The participants had ophthalmologic examinations including stereoscopic fundus observations, OCT examinations, and perimetry. For OCT, multiple horizontal and vertical OCT scans were obtained around the optic disc and fovea in each patient. Main Outcome Measures: The presence of a peripapillary detachment in eyes with pathologic myopia (PDPM) around and within the area of myopic conus, and the vascular microfolds and retinoschisis at the site of the retinal vessels at the conus edge were evaluated. Results: A PDPM was detected by OCT in 14 eyes (11.0%). A PDPM was seen in the OCT images as a hyporeflective space intrachoroidally and subretinally. Hyporeflective spaces resembling PDPMs were also observed within the tissue posterior to the conus in eyes without the typical ophthalmoscopic yellow-orange lesions. Eyes with PDPM had glaucomalike visual field defects more frequently than eyes without PDPM. Pitlike structures within the conus were observed ophthalmoscopically in 3 eyes with high myopia, and OCT examinations revealed the presence of cystic structures with an opening toward the vitreous cavity at the corresponding sites. Microfolds in the retinal vessels were detected at the conus edge in 58 of the highly myopic eyes (45.0%), and 28 of these eyes had retinoschisis at the site of the retinal vessels. Fifteen of these 28 eyes showed an extension of the retinoschisis along the temporal retinal vessels toward the macula, and 9 of these 15 eyes had myopic foveoschisis. None of these changes (PDPM, pitlike structures, microfolds, and retinoschisis) were detected in controls. Conclusions: The OCT examinations demonstrated different types of abnormalities around the optic disc in highly myopic eyes. These changes might be related to the visually disabling complications, such as visual field loss and myopic foveoschisis, seen in highly myopic eyes. Ophthalmology 2007;114:2070 –2076 © 2007 by the American Academy of Ophthalmology.
High myopia is a major cause of legal blindness in developed countries.1,2 Pooled data from 6 population-based eye studies conducted on persons ⱖ40 years showed that approximately 1 of every 24 (4.2%) persons in the United Originally received: September 21, 2006. Final revision: January 18, 2007. Accepted: January 19, 2007. Available online: May 31, 2007. Manuscript no. 2006-1071. From the Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University, Tokyo, Japan. Supported in part by the Japan Society for the Promotion of Science, Tokyo, Japan (research grant nos. 16390495, 17591823). The authors have no financial interest in any products or drugs discussed in the article. Correspondence to Kyoko Ohno-Matsui, MD, Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113, Japan. E-mail: [email protected].
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© 2007 by the American Academy of Ophthalmology Published by Elsevier Inc.
States and Western Europe had myopia ⱖ5 diopters (D).3 A population-based cohort study of 4439 adult subjects in northern China reported that the frequency of myopia ⬎ 8 D was 1.5%.4 In Japan, the incidence of myopia has still not been determined, but myopia ⬎ 8 D affects 6% to 18% of the myopic population and 1% of the general population.5 In some of the highly myopic eyes, various visually disabling complications develop in the posterior fundus that result from an elongation of the axial length or the formation of a posterior staphyloma.6 These eyes tend to develop chorioretinal atrophy in the posterior pole,6 choroidal neovascularization in the macular region,7 and macular holes.8 Previous studies have demonstrated that eyes with high myopia have a greater susceptibility of developing optic nerve fiber loss resembling that in glaucomatous eyes.9,10 Recent advancements in optical coherence tomography (OCT) have enabled ophthalmologists to perform detailed ISSN 0161-6420/07/$–see front matter doi:10.1016/j.ophtha.2007.01.016
Shimada et al 䡠 Peripapillary Changes in High Myopia examinations of the retina and choroid that can identify the pathologic changes in eyes with high myopia, including those with macular retinoschisis.11 Macular retinoschisis or myopic foveoschisis has been identified in 9% to 34% of highly myopic eyes with a posterior staphyloma.11,12 The exact pathogenesis of the myopic foveoschisis has not been fully determined, but the detection of retinal microfolds by OCT suggested an inward traction on the retinal vasculature as the cause of the foveoschisis.13 Most of the OCT examinations of eyes with high myopia have focused on the macula, and the changes around the optic disc (e.g., tilting of the optic disc and myopic conus) have not been investigated in detail. The only exceptions to this are the studies of the peripapillary detachments in pathologic myopia (PDPMs). A PDPM appears ophthalmoscopically as a yellowish-orange lesion around the optic disc conus, and OCT images of this area have shown a localized detachment of the retinal pigment epithelium (RPE) from the choroid.14 However, a recent study using the Stratus OCT3000 demonstrated that the PDPM was a peripapillary intrachoroidal cavity separating the RPE from the sclera.15 The pathogenesis of PDPMs is still unknown. During our examination of many highly myopic eyes by OCT, we noticed that the abnormalities present around the optic disc could be classified into distinct groups. Because examining the abnormalities around the optic disc in highly myopic eyes may provide clues to the development of various vision-threatening alterations in high myopia (e.g., foveoschisis and glaucoma), we examined the peripapillary area in eyes with high myopia in more detail by OCT. The purpose of this study was to examine the abnormalities detected by OCT around the optic disc in eyes with high myopia, and to relate these changes to the other changes found in eyes with high myopia.
Patients and Methods The procedures used conformed to the guidelines of the Declaration of Helsinki, and an informed consent was obtained from each patient. The study protocol was approved by the Ethics Committee of the Tokyo Medical and Dental University. This study included 127 eyes from 69 patients with high myopia. Eleven eyes were excluded because of a history of retinal detachment surgery or dense cataract that prevented a detailed examination by OCT. For control, 46 eyes from 23 patients with emmetropia, and 40 eyes from 20 patients with low myopia were evaluated. These patients were examined in the Tokyo Medical and Dental University Hospital from October 2005 to August 2006. The definition of high myopia was a refractive error ⱖ ⫺8.00 D or an axial length ⬎ 26.5 mm. The definitions of emmetropia and low myopia were a refractive error from ⫹1.00 to ⫺1.00 D and from ⫺2.00 to ⫺6.00 D, respectively. The refractive errors are expressed as the spherical equivalent. All of these patients consented to be examined by OCT. All of the patients received a complete ophthalmologic examination, including best-corrected visual acuity, intraocular pressure (IOP) measurements, axial length measurements, anterior segment biomicroscopy, dilated fundus examination by indirect ophthalmoscopy, OCT examination, color fundus photography, and visual field testing. The OCT examinations were performed through a
dilated pupil using a commercially available OCT ophthalmoscope (C7, NIDEK, Aichi, Japan). Ten or more horizontal and vertical OCT scans (about 7 mm in length) were recorded around the optic disc and also at the fovea in each patient. One of the authors (NS) who was masked to the refractive error and ophthalmoscopic findings in each patient read the OCT images. Visual fields were determined by Goldmann kinetic perimetry with the patients’ refractive errors fully corrected with disposable soft contact lenses. For patients ⬎40 years old, a correction was made for the testing distance of 30 cm. The patient was classified as having a glaucomalike visual field loss when ⱖ1 of the following perimetric defects was present: nasal step, arcuate scotoma, double arcuate scotomas, generalized constriction relative to the fellow eye, and temporal wedge. In each case, the visual field defect could not be explained by the myopic fundus changes. Statistical analyses were performed using the Fisher exact probability test, chi-square test, and Mann–Whitney U test. A P value ⬍ 0.05 was considered significant.
Results The clinical characteristics of the 127 eyes (69 patients) with high myopia were studied. There were 25 men and 44 women with a mean age of 56.5⫾11.1 years (range, 27–78 years). The mean refractive error was ⫺13.4⫾3.76 D (range, ⫺8.25 to ⫺23.0 D), and the mean axial length was 28.7⫾1.52 mm (range, 25.1–32.5 mm). In the emmetropia group, the mean age was 60.4⫾11.2 years (range, 35–79 years), the mean refractive error was 0.25⫾0.46 D (range, ⫹0.88 to ⫺0.75D), and the mean axial length was 23.8⫾0.47 mm (range, 22.3–24.6 mm). In the low myopia group, the mean age was 53.9⫾12.8 years (range, 30 –78 years), the mean refractive error was ⫺3.6⫾1.05 D (range, ⫺2.25 to ⫺5.5 D), and the mean axial length was 25.0⫾0.37 mm (range, 24.1–25.8 mm). The mean axial length of the emmetropia group and the low myopia group was significantly shorter than that of the high myopia group (P⬍0.05, Mann–Whitney U test). In eyes with high myopia, a myopic conus was detected in all 127 eyes and a posterior staphyloma in 88 eyes (69.3%) by indirect ophthalmoscopy. In controls, a myopic conus was observed in 10 eyes (25.0%) with low myopia; however, a posterior staphyloma was not detected in any eyes in the emmetropia or low myopia groups. The OCT images were examined especially for the presence of PDPM around and within the area of myopic conus, and for vascular microfolds and retinoschisis at the site of the retinal vessels at the conus edge.
Peripapillary Detachments in Eyes with Pathologic Myopia Ophthalmoscopically, PDPMs were seen as yellow-orange lesions around the myopic conus in 12 highly myopic eyes (9.4%). In contrast, PDPMs were not observed in any eyes in the emmetropia and low myopia groups. The OCT images of PDPMs showed a hyporeflective space between the RPE and choroid, and possibly intrachoroidally in most patients (Figs 1, 2). A hyporeflective area was also observed in the subretinal space in some patients (Fig 2). Peripapillary detachments in pathologic myopia seemed to consist of cystoid spaces (Figs 1, 2), and in 5 of 12 eyes, the hyporeflective space corresponding to the PDPM extended below the area of myopic conus (Fig 2). An intrachoroidal hyporeflective space resembling a PDPM was also detected below the myopic conus in the OCT images of 2 eyes without the typical yellow-orange lesion around the conus ophthalmoscopically (Fig 3). Therefore, a PDPM was detected by OCT in a total of 14 highly myopic eyes (11.0%).
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Shimada et al 䡠 Peripapillary Changes in High Myopia The OCT examinations and stereoscopic fundus observations revealed excavations or posterior extensions in the area of the myopic conus in 23 of the 127 highly myopic eyes (18.1%). A PDPM was observed in 10 of these 23 eyes (43.5%), and in 4 of 104 eyes (3.8%) without an excavation. This difference in the incidence was significant (P⬍0.001, Fisher exact probability test). Glaucomalike visual field defects were detected in 9 of 14 eyes (64.3%) with a PDPM, and in 22 of 113 eyes (19.5%) without a PDPM. This difference was also significant (P⬍0.001, Fisher exact probability test). The mean IOP was 15.3⫾2.7 mmHg in eyes with a PDPM and 14.7⫾2.2 mmHg in eyes without PDPM. This difference was not significant (P ⫽ 0.4, Mann–Whitney U test).
Optical Coherence Tomography Findings within Areas of Myopic Conus Stereoscopic observations using a ⫹78-D lens revealed focal pitlike structures within the area of the myopic conus in 3 highly myopic eyes (2.4%; Fig 1A). Optical coherence tomography examination of these structures demonstrated cystic spaces posterior to the conus alongside the retrobulbar optic nerve (Fig 1C) in 1 of these 3 eyes. In this patient, the cyst was opened to the vitreous body (Fig 1C). This eye had a prominent posterior excavation of myopic conus and a wide area of the PDPM. We previously reported the PDPM findings in this patient.16 The other 2 eyes did not show any obvious cystic spaces corresponding to the pitlike structure by OCT and were not accompanied by posterior excavation of the conus. In contrast, these findings were not detected in any eyes in the emmetropia and low myopia groups.
Microfolds and Retinoschisis of Peripapillary Retinal Vessels The retinal vessels around the myopic conus were investigated by OCT. Vertical scans at the edge of the conus showed that the incidence of microfolds in the peripapillary retinal vessels was high at 45.0% (58 eyes; Fig 4) in highly myopic eyes. This incidence was significantly higher than that of retinal microfolds identified in the vertical OCT scan across the fovea centralis (10 eyes; 7.8%). Retinal microfolds were not observed in any eyes in the emmetropia and low myopia groups. Microfolds of the arterioles around the myopic conus were observed in only 8 eyes, retinal venules in none, and both arterioles and venules in 50 eyes. The microfolds around the myopic conus were observed in the upper temporal vessels in 48 eyes, lower
temporal vessels in 51 eyes, upper nasal vessels in 27 eyes, and lower nasal vessels in 25 eyes. The characteristics of the 58 eyes with vascular microfolds at the conus edge and of 69 eyes without vascular microfolds are summarized in Table 1. The patients with vascular microfolds at the conus edge were significantly older, were more myopic, and had longer axial lengths (P⬍0.05, Mann– Whitney U test). A posterior staphyloma was observed more frequently in eyes with vascular microfolds at the conus edge than in eyes without microfolds (P⬍0.05, chi-square test). Twenty-eight of the 58 eyes with vascular microfolds had retinoschisis at the site of the retinal vessels (Fig 4). The peripapillary retinal vessels with microfolds associated with the retinoschisis were seen more frequently along the lower temporal vessels (21 eyes) than the upper temporal vessels (19 eyes), the upper nasal vessels (6 eyes), and the lower nasal vessels (4 eyes; overlapped). Among the 28 eyes with retinoschisis of retinal vessels at the conus margin, 8 eyes showed an extension of the retinoschisis towards the upper or lower portion of the conus (Fig 4B). Fifteen of these 28 eyes showed an extension of the retinoschisis along the temporal retinal vessels toward the macular area (Fig 4C), and 9 of these 15 eyes eventually developed myopic foveoschisis (Fig 4D). Only 1 eye had a myopic foveoschisis without a peripapillary retinoschisis. However, this eye had a tractional epiretinal membrane in the macular area (not shown).
Discussion The examination of the peripapillary area of eyes with high myopia by OCT showed different types of alterations in the ocular structures. One of the peripapillary alterations was the PDPM, a newly recognized lesion around the optic disc that is found in some eyes with high myopia.14 The PDPMs are seen as yellow-orange lesions surrounding the myopic conus by ophthalmoscopy, and OCT demonstrated a localized detachment of the RPE. We have reported that a PDPM is not rare; we have found a PDPM in 4.9% of eyes with pathologic myopia.16 In the present study, a PDPM was observed ophthalmoscopically at a slightly higher prevalence of 9.4% of highly myopic eyes. The reason for the discrepancy of the prevalence of PDPM is not known; however, a difference in the distribution of the ages in the 2 studies might be a reason. We reported that a PDPM was never observed in patients ⬍30 years old,16 and in this study, the age range was 27 to 78 years, and only 1 patient was ⬍30 years old.
4™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™ Figure 1. Peripapillary detachment in pathologic myopia (PDPM) and cystic spaces within the area of the conus from the right eye of a 62-year-old man. A, Fundus photograph of the right eye with a refractive error of ⫺9.5 diopters and axial length of 27.8 mm. The yellow-orange lesion around the optic disc suggests a PDPM (arrowheads). Within the area of the conus, 3 focal pitlike structures are observed (*). The temporal conus is deeply excavated and the optic disc is almost invisible. B, Photograph of the optic disc of the right eye and orientation of the 2 scans of optical coherence tomography (OCT) shown in C and D. C, Horizontal OCT scan shows hyporeflective space intrachoroidally (arrow) at the site of the PDPM seen in A. The cystic space (*) is seen at the site corresponding to the pitlike structures observed ophthalmoscopically in A. Cystic space extends posteriorly to the conus, and the cyst is opened to the vitreous body (arrowhead). D, Vertical OCT scan through a PDPM showing that this lesion consists of multiple cystic structures in the choroid (*). Figure 2. Characteristics of peripapillary detachment in pathologic myopia (PDPM) located subretinally and intrachoroidally. A, Right fundus photograph of a 62-year-old man with a refractive error of ⫺12.0 diopters and axial length of 28.7 mm showing a yellow-orange lesion inferior to the optic disc suggestive of a PDPM (arrowheads). Orientation of the 2 scans of optical coherence tomography (OCT) in B and C are shown. B, Vertical OCT scan shows a hyporeflective space intrachoroidally (arrowheads). Hyporeflective space also exists superior to the myopic conus and extends to the area within the conus. Hyporeflective space is also seen subretinally (arrow), and consists of cystic spaces (*) within the area of the conus. C, Horizontal OCT scan shows the detachment of the neural retina in the area of myopic conus (arrow). Posterior excavation of the temporal conus is prominent (arrowheads).
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Figure 3. Intrachoroidal cavity within the area of myopic conus in eyes without a yellow-orange lesion observed ophthalmoscopically. A, Right fundus of a 65-year-old woman with a refractive error of ⫺17.5 diopters and an axial length of 28.1 mm shows a large conus and diffuse chorioretinal atrophy in the posterior fundus. A yellow-orange lesion suggestive of peripapillary detachment in pathologic myopia is not observed. Orientation of the scan of optical coherence tomography (OCT) in B is shown. B, Vertical OCT scan across the nasal edge of the optic disc reveals intrachoroidal cavity (*) within the area of myopic conus.
We also reported that glaucomalike visual field defects were frequently detected in eyes with a PDPM.16 The results of the present study supported this finding, and IOP was not significantly different between eyes with and without a PDPM. Although the mechanism(s) for the concomitant visual field defects in eyes with PDPM is not clear, our findings suggest that the distorted structure of the neurosensory retina caused by the marked tilting of the optic disc might be a more important factor than the IOP. From the results obtained by Stratus OCT 3000, Toranzo et al15 reported that a PDPM was not a detachment of the RPE but a peripapillary intrachoroidal cavity separating the RPE from the sclera. In this study, OCT ophthalmoscopy showed that the yellow-orange lesion around the optic disc was an intrachoroidal hyporeflective space consisting of cystic spaces in most patients. However, in some patients the hyporeflective space was also observed between the
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RPE layer and the neural retina. In addition, a hyporeflective space was seen in some patients only posterior to the myopic conus, and the yellow-orange lesion was not seen ophthalmoscopically in these cases. These observations suggest that PDPMs may be present more frequently in eyes with high myopia than might be expected by the ophthalmoscopic observations alone. Although the pathogenesis of PDPMs has not been conclusively determined, they were frequently detected in eyes with a posterior excavation of the conus. Why a conus protrudes posteriorly is unclear; however, this area of the conus lacks the RPE and choroid and may thus be structurally weak. Therefore, when a conus enlarges, this structure might protrude posteriorly in response to the enlargement. Then, when the posterior excavation of the conus occurs, the conus and the surrounding peripapillary tissue are mechanically stretched, and this mechanical force might cause
Shimada et al 䡠 Peripapillary Changes in High Myopia
Figure 4. Peripapillary vascular microfolds and retinoschisis in eyes with myopic foveoschisis. A, Left fundus of a 44-year-old man with a refractive error of ⫺18.0 diopters and an axial length of 29.6 mm shows a large temporal conus and diffuse chorioretinal atrophy in the posterior fundus. Orientation of the scans of optical coherence tomography (OCT) in B, C, and D are shown. B, Vertical OCT scan near the temporal edge of myopic conus shows vascular microfolds (arrows) and retinoschisis (*). Retinoschisis is observed within the area of the conus as well (arrowhead). C, Vertical OCT scan between the fovea centralis and the conus shows slight vascular microfolds (arrows) and retinoschisis (*). D, Vertical OCT scan at the fovea centralis shows myopic foveoschisis (*) as well as multilayered schisis (arrowheads). Slight vascular microfolds are still observed (arrow).
a splitting of the intrachoroidal structures to produce the cystoid spaces. Later, the cystoid spaces enlarge and coalesce, and finally develop a large cystic area seen as a hyporeflective space on OCT. A splitting of the tissue in or around the peripapillary choroid in eyes with high myopia then might result in a structural weakening of the peripapillary tissue. This might decrease the ability of the tissue to absorb the mechanical pressure of the IOP changes, and thus might lead to optic nerve damage or expulsive hemorrhages in eyes with high myopia. More extensive research is required to determine whether this description is accurate. We also observed pitlike structures within the conus ophthalmoscopically, and OCT examination of these areas demonstrated the presence of cystic structures at the corresponding sites. Some of these cysts were opened to the vitreous cavity. We are unaware of any previous reports describing similar cystic structures in eyes with high myopia. The OCT images of these cystlike structures seemed similar to those of optic pits. Todokoro and Kishi17 reported
the OCT findings in a case with these pits, and they demonstrated that they were not true pits but cystic spaces covered by a superficial layer of the optic disc. The cysts were not connected to the vitreous because of the overlying superficial retinal layer. Because our patients were not examined at a younger age, we were not able to determine whether the cysts are a congenital anomaly or developed secondarily during the progression of myopia. However, the cystic space observed in our patients had 2 differences from optic pits. First, the location was different; the optic pit exists within the area of the optic disc whereas the cyst in our patients existed within the conus outside the optic disc. And second, the cyst was not covered by a superficial layer of the optic disc and was thus opened to the vitreous cavity. Also, 1 patient had a prominent excavation of the conus and a wide area of PDPM, which might suggest that a prominent mechanical extension around the optic disc might be related to the secondary development of cystic structure within the conus.
Table 1. Characteristics of Eyes with or without Vascular Microfolds at the Edge of Myopic Conus
Age (yrs) (mean ⫾ SD) Refractive error (D) (mean ⫾ SD) Axial length (mm) (mean ⫾ SD) Posterior staphyloma
With Vascular Microfolds (77 Eyes)
Without Vascular Microfolds (50 Eyes)
P Value
59.5 ⫾ 8.3 ⫺14.2 ⫾ 3.9 28.9 ⫾ 1.4 60 eyes (77.9%)
51.8 ⫾ 13.2 ⫺12.1 ⫾ 3.2 28.3 ⫾ 1.6 28 eyes (56.0%)
0.0007* 0.005* 0.02* 0.01†
D ⫽ diopters; SD ⫽ standard deviation. *Mann–Whitney U test. † Chi-square test.
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Ophthalmology Volume 114, Number 11, November 2007 However, more studies are necessary to investigate the pathogenesis of cystic structures. Sayanagi et al13 reported on the results of their OCT studies on 7 highly myopic eyes with vascular microfolds along the retinal vessels in the macular area. They suggested that the formation of the microfolds indicated a strong inward traction that resulted from an elongation of the axial length in eyes with high myopia and may be related to the pathogenesis of pathologic myopia-specific alterations such as myopic foveoschisis.13 Although they reported that the incidence of vascular microfolds in OCT scans across the fovea centralis was 2.9%, our vertical OCT scans across the fovea demonstrated that vascular microfolds were detected in 7.8%, a higher incidence than that of Sayanagi et al.13 Interestingly, our study revealed that the incidence of vascular microfolds at the conus edge was significantly higher at 45.0%. This suggests that the vascular microfolds might first develop at the edge of the conus in eyes with high myopia. Retinoschisis was detected in more than one third of the eyes at the site of the retinal vessels with microfolds. In these cases, the vascular microfolds and accompanying retinoschisis extended continuously along the retinal vessels towards the macular area, and 9 eyes eventually had myopic foveoschisis. This indicates that the inward traction of the retinal vessels in addition to the vitreoretinal traction and posterior staphyloma might be important in the pathogenesis of myopic foveoschisis. These observations also suggest that the vascular microfolds may gradually extend from the conus edge toward the macular region. This would then suggest that the vascular microfolds at the conus edge might be the first sign of an inward traction of retinal vessels, and might be a risk for the development of myopic foveoschisis. In conclusion, OCT examination identified different types of abnormalities around the optic disc in eyes with high myopia. Presumably, the formation of a posterior staphyloma and subsequent excavation of the conus might cause severe mechanical stress around the optic disc that leads to a splitting or cavitation of the subretinal tissue, mainly intrachoroidally. Also, vascular microfolds of retinal vessels frequently develop at the conus edge, and might progress toward the macula. These changes might be related to visually disabling conditions such as visual field loss or myopic foveoschisis in eyes with high myopia. Because myopic conus is one of the earliest changes seen in highly myopic eyes, the mechanical stretch might be especially prominent at and around the optic disc. Because our results revealed that the various abnormalities detected by OCT around the optic disc were related to the development of visually disabling conditions in high myopia, it is important to detect these peripapillary changes by OCT to be able to predict the later development of visually disabling conditions. Although further studies are necessary, OCT exami-
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nation has provided valuable evidence on the underlying changes that occur around the optic disc in eyes with high myopia. Acknowledgment. The authors thank Professor Duco Hamasaki for critical reading of and suggestions for the manuscript.
References 1. Ghafour IM, Allan D, Foulds WS. Common causes of blindness and visual handicap in the west of Scotland. Br J Ophthalmol 1983;67:209 –13. 2. Sperduto RD, Seigel D, Roberts J, Rowland M. Prevalence of myopia in the United States. Arch Ophthalmol 1983;101: 405–7. 3. Eye Diseases Prevalence Research Group. The prevalence of refractive errors among adults in the United States, western Europe, and Australia. Arch Ophthalmol 2004;122: 495–505. 4. Xu L, Li J, Cui T, et al. Refractive error in urban and rural adult Chinese in Beijing. Ophthalmology 2005;112:1676 – 83. 5. Tokoro T. On the definition of pathologic myopia in group studies. Acta Ophthalmol Suppl 1988;185:107– 8. 6. Curtin BJ. The Myopias: Basic Science and Clinical Management. Philadelphia: Harper & Row; 1985:277–347. 7. Ohno-Matsui K, Yoshida T, Futagami S, et al. Patchy atrophy and lacquer cracks predispose to the development of choroidal neovascularization in pathological myopia. Br J Ophthalmol 2003;87:570 –3. 8. Kobayashi H, Kobayashi K, Okinami S. Macular hole and myopic refraction. Br J Ophthalmol 2002;86:1269 –73. 9. Jonas JB, Budde WM. Optic nerve damage in highly myopic eyes with chronic open-angle glaucoma. Eur J Ophthalmol 2005;15:41–7. 10. Podos SM, Becker B, Morton WR. High myopia and primary open-angle glaucoma. Am J Ophthalmol 1966;62:1038 – 43. 11. Takano M, Kishi S. Foveal retinoschisis and retinal detachment in severely myopic eyes with posterior staphyloma. Am J Ophthalmol 1999;128:472– 6. 12. Baba T, Ohno-Matsui K, Futagami S, et al. Prevalence and characteristics of foveal retinal detachment without macular hole in high myopia. Am J Ophthalmol 2003;135:338 – 42. 13. Sayanagi K, Ikuno Y, Gomi F, Tano Y. Retinal vascular microfolds in highly myopic eyes. Am J Ophthalmol 2005; 139:658 – 63. 14. Freund KB, Ciardella AP, Yannuzzi LA, et al. Peripapillary detachment in pathologic myopia. Arch Ophthalmol 2003; 121:197–204. 15. Toranzo J, Cohen SY, Erginay A, Gaudric A. Peripapillary intrachoroidal cavitation in myopia. Am J Ophthalmol 2005; 140:731–2. 16. Shimada N, Ohno-Matsui K, Yoshida T, et al. Characteristics of peripapillary detachment in pathologic myopia. Arch Ophthalmol 2006;124:46 –52. 17. Todokoro D, Kishi S. Reattachment of retina and retinoschisis in pit-macular syndrome by surgically-induced vitreous detachment and gas tamponade. Ophthalmic Surg Lasers 2000;31:233–5.
High myopia is a major cause of legal blindness in developed countries.1,2 Pooled data from 6 population-based eye studies conducted on persons ⱖ40 years showed that approximately 1 of every 24 (4.2%) persons in the United Originally received: September 21, 2006. Final revision: January 18, 2007. Accepted: January 19, 2007. Available online: May 31, 2007. Manuscript no. 2006-1071. From the Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University, Tokyo, Japan. Supported in part by the Japan Society for the Promotion of Science, Tokyo, Japan (research grant nos. 16390495, 17591823). The authors have no financial interest in any products or drugs discussed in the article. Correspondence to Kyoko Ohno-Matsui, MD, Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113, Japan. E-mail: [email protected].
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© 2007 by the American Academy of Ophthalmology Published by Elsevier Inc.
States and Western Europe had myopia ⱖ5 diopters (D).3 A population-based cohort study of 4439 adult subjects in northern China reported that the frequency of myopia ⬎ 8 D was 1.5%.4 In Japan, the incidence of myopia has still not been determined, but myopia ⬎ 8 D affects 6% to 18% of the myopic population and 1% of the general population.5 In some of the highly myopic eyes, various visually disabling complications develop in the posterior fundus that result from an elongation of the axial length or the formation of a posterior staphyloma.6 These eyes tend to develop chorioretinal atrophy in the posterior pole,6 choroidal neovascularization in the macular region,7 and macular holes.8 Previous studies have demonstrated that eyes with high myopia have a greater susceptibility of developing optic nerve fiber loss resembling that in glaucomatous eyes.9,10 Recent advancements in optical coherence tomography (OCT) have enabled ophthalmologists to perform detailed ISSN 0161-6420/07/$–see front matter doi:10.1016/j.ophtha.2007.01.016
Shimada et al 䡠 Peripapillary Changes in High Myopia examinations of the retina and choroid that can identify the pathologic changes in eyes with high myopia, including those with macular retinoschisis.11 Macular retinoschisis or myopic foveoschisis has been identified in 9% to 34% of highly myopic eyes with a posterior staphyloma.11,12 The exact pathogenesis of the myopic foveoschisis has not been fully determined, but the detection of retinal microfolds by OCT suggested an inward traction on the retinal vasculature as the cause of the foveoschisis.13 Most of the OCT examinations of eyes with high myopia have focused on the macula, and the changes around the optic disc (e.g., tilting of the optic disc and myopic conus) have not been investigated in detail. The only exceptions to this are the studies of the peripapillary detachments in pathologic myopia (PDPMs). A PDPM appears ophthalmoscopically as a yellowish-orange lesion around the optic disc conus, and OCT images of this area have shown a localized detachment of the retinal pigment epithelium (RPE) from the choroid.14 However, a recent study using the Stratus OCT3000 demonstrated that the PDPM was a peripapillary intrachoroidal cavity separating the RPE from the sclera.15 The pathogenesis of PDPMs is still unknown. During our examination of many highly myopic eyes by OCT, we noticed that the abnormalities present around the optic disc could be classified into distinct groups. Because examining the abnormalities around the optic disc in highly myopic eyes may provide clues to the development of various vision-threatening alterations in high myopia (e.g., foveoschisis and glaucoma), we examined the peripapillary area in eyes with high myopia in more detail by OCT. The purpose of this study was to examine the abnormalities detected by OCT around the optic disc in eyes with high myopia, and to relate these changes to the other changes found in eyes with high myopia.
Patients and Methods The procedures used conformed to the guidelines of the Declaration of Helsinki, and an informed consent was obtained from each patient. The study protocol was approved by the Ethics Committee of the Tokyo Medical and Dental University. This study included 127 eyes from 69 patients with high myopia. Eleven eyes were excluded because of a history of retinal detachment surgery or dense cataract that prevented a detailed examination by OCT. For control, 46 eyes from 23 patients with emmetropia, and 40 eyes from 20 patients with low myopia were evaluated. These patients were examined in the Tokyo Medical and Dental University Hospital from October 2005 to August 2006. The definition of high myopia was a refractive error ⱖ ⫺8.00 D or an axial length ⬎ 26.5 mm. The definitions of emmetropia and low myopia were a refractive error from ⫹1.00 to ⫺1.00 D and from ⫺2.00 to ⫺6.00 D, respectively. The refractive errors are expressed as the spherical equivalent. All of these patients consented to be examined by OCT. All of the patients received a complete ophthalmologic examination, including best-corrected visual acuity, intraocular pressure (IOP) measurements, axial length measurements, anterior segment biomicroscopy, dilated fundus examination by indirect ophthalmoscopy, OCT examination, color fundus photography, and visual field testing. The OCT examinations were performed through a
dilated pupil using a commercially available OCT ophthalmoscope (C7, NIDEK, Aichi, Japan). Ten or more horizontal and vertical OCT scans (about 7 mm in length) were recorded around the optic disc and also at the fovea in each patient. One of the authors (NS) who was masked to the refractive error and ophthalmoscopic findings in each patient read the OCT images. Visual fields were determined by Goldmann kinetic perimetry with the patients’ refractive errors fully corrected with disposable soft contact lenses. For patients ⬎40 years old, a correction was made for the testing distance of 30 cm. The patient was classified as having a glaucomalike visual field loss when ⱖ1 of the following perimetric defects was present: nasal step, arcuate scotoma, double arcuate scotomas, generalized constriction relative to the fellow eye, and temporal wedge. In each case, the visual field defect could not be explained by the myopic fundus changes. Statistical analyses were performed using the Fisher exact probability test, chi-square test, and Mann–Whitney U test. A P value ⬍ 0.05 was considered significant.
Results The clinical characteristics of the 127 eyes (69 patients) with high myopia were studied. There were 25 men and 44 women with a mean age of 56.5⫾11.1 years (range, 27–78 years). The mean refractive error was ⫺13.4⫾3.76 D (range, ⫺8.25 to ⫺23.0 D), and the mean axial length was 28.7⫾1.52 mm (range, 25.1–32.5 mm). In the emmetropia group, the mean age was 60.4⫾11.2 years (range, 35–79 years), the mean refractive error was 0.25⫾0.46 D (range, ⫹0.88 to ⫺0.75D), and the mean axial length was 23.8⫾0.47 mm (range, 22.3–24.6 mm). In the low myopia group, the mean age was 53.9⫾12.8 years (range, 30 –78 years), the mean refractive error was ⫺3.6⫾1.05 D (range, ⫺2.25 to ⫺5.5 D), and the mean axial length was 25.0⫾0.37 mm (range, 24.1–25.8 mm). The mean axial length of the emmetropia group and the low myopia group was significantly shorter than that of the high myopia group (P⬍0.05, Mann–Whitney U test). In eyes with high myopia, a myopic conus was detected in all 127 eyes and a posterior staphyloma in 88 eyes (69.3%) by indirect ophthalmoscopy. In controls, a myopic conus was observed in 10 eyes (25.0%) with low myopia; however, a posterior staphyloma was not detected in any eyes in the emmetropia or low myopia groups. The OCT images were examined especially for the presence of PDPM around and within the area of myopic conus, and for vascular microfolds and retinoschisis at the site of the retinal vessels at the conus edge.
Peripapillary Detachments in Eyes with Pathologic Myopia Ophthalmoscopically, PDPMs were seen as yellow-orange lesions around the myopic conus in 12 highly myopic eyes (9.4%). In contrast, PDPMs were not observed in any eyes in the emmetropia and low myopia groups. The OCT images of PDPMs showed a hyporeflective space between the RPE and choroid, and possibly intrachoroidally in most patients (Figs 1, 2). A hyporeflective area was also observed in the subretinal space in some patients (Fig 2). Peripapillary detachments in pathologic myopia seemed to consist of cystoid spaces (Figs 1, 2), and in 5 of 12 eyes, the hyporeflective space corresponding to the PDPM extended below the area of myopic conus (Fig 2). An intrachoroidal hyporeflective space resembling a PDPM was also detected below the myopic conus in the OCT images of 2 eyes without the typical yellow-orange lesion around the conus ophthalmoscopically (Fig 3). Therefore, a PDPM was detected by OCT in a total of 14 highly myopic eyes (11.0%).
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Shimada et al 䡠 Peripapillary Changes in High Myopia The OCT examinations and stereoscopic fundus observations revealed excavations or posterior extensions in the area of the myopic conus in 23 of the 127 highly myopic eyes (18.1%). A PDPM was observed in 10 of these 23 eyes (43.5%), and in 4 of 104 eyes (3.8%) without an excavation. This difference in the incidence was significant (P⬍0.001, Fisher exact probability test). Glaucomalike visual field defects were detected in 9 of 14 eyes (64.3%) with a PDPM, and in 22 of 113 eyes (19.5%) without a PDPM. This difference was also significant (P⬍0.001, Fisher exact probability test). The mean IOP was 15.3⫾2.7 mmHg in eyes with a PDPM and 14.7⫾2.2 mmHg in eyes without PDPM. This difference was not significant (P ⫽ 0.4, Mann–Whitney U test).
Optical Coherence Tomography Findings within Areas of Myopic Conus Stereoscopic observations using a ⫹78-D lens revealed focal pitlike structures within the area of the myopic conus in 3 highly myopic eyes (2.4%; Fig 1A). Optical coherence tomography examination of these structures demonstrated cystic spaces posterior to the conus alongside the retrobulbar optic nerve (Fig 1C) in 1 of these 3 eyes. In this patient, the cyst was opened to the vitreous body (Fig 1C). This eye had a prominent posterior excavation of myopic conus and a wide area of the PDPM. We previously reported the PDPM findings in this patient.16 The other 2 eyes did not show any obvious cystic spaces corresponding to the pitlike structure by OCT and were not accompanied by posterior excavation of the conus. In contrast, these findings were not detected in any eyes in the emmetropia and low myopia groups.
Microfolds and Retinoschisis of Peripapillary Retinal Vessels The retinal vessels around the myopic conus were investigated by OCT. Vertical scans at the edge of the conus showed that the incidence of microfolds in the peripapillary retinal vessels was high at 45.0% (58 eyes; Fig 4) in highly myopic eyes. This incidence was significantly higher than that of retinal microfolds identified in the vertical OCT scan across the fovea centralis (10 eyes; 7.8%). Retinal microfolds were not observed in any eyes in the emmetropia and low myopia groups. Microfolds of the arterioles around the myopic conus were observed in only 8 eyes, retinal venules in none, and both arterioles and venules in 50 eyes. The microfolds around the myopic conus were observed in the upper temporal vessels in 48 eyes, lower
temporal vessels in 51 eyes, upper nasal vessels in 27 eyes, and lower nasal vessels in 25 eyes. The characteristics of the 58 eyes with vascular microfolds at the conus edge and of 69 eyes without vascular microfolds are summarized in Table 1. The patients with vascular microfolds at the conus edge were significantly older, were more myopic, and had longer axial lengths (P⬍0.05, Mann– Whitney U test). A posterior staphyloma was observed more frequently in eyes with vascular microfolds at the conus edge than in eyes without microfolds (P⬍0.05, chi-square test). Twenty-eight of the 58 eyes with vascular microfolds had retinoschisis at the site of the retinal vessels (Fig 4). The peripapillary retinal vessels with microfolds associated with the retinoschisis were seen more frequently along the lower temporal vessels (21 eyes) than the upper temporal vessels (19 eyes), the upper nasal vessels (6 eyes), and the lower nasal vessels (4 eyes; overlapped). Among the 28 eyes with retinoschisis of retinal vessels at the conus margin, 8 eyes showed an extension of the retinoschisis towards the upper or lower portion of the conus (Fig 4B). Fifteen of these 28 eyes showed an extension of the retinoschisis along the temporal retinal vessels toward the macular area (Fig 4C), and 9 of these 15 eyes eventually developed myopic foveoschisis (Fig 4D). Only 1 eye had a myopic foveoschisis without a peripapillary retinoschisis. However, this eye had a tractional epiretinal membrane in the macular area (not shown).
Discussion The examination of the peripapillary area of eyes with high myopia by OCT showed different types of alterations in the ocular structures. One of the peripapillary alterations was the PDPM, a newly recognized lesion around the optic disc that is found in some eyes with high myopia.14 The PDPMs are seen as yellow-orange lesions surrounding the myopic conus by ophthalmoscopy, and OCT demonstrated a localized detachment of the RPE. We have reported that a PDPM is not rare; we have found a PDPM in 4.9% of eyes with pathologic myopia.16 In the present study, a PDPM was observed ophthalmoscopically at a slightly higher prevalence of 9.4% of highly myopic eyes. The reason for the discrepancy of the prevalence of PDPM is not known; however, a difference in the distribution of the ages in the 2 studies might be a reason. We reported that a PDPM was never observed in patients ⬍30 years old,16 and in this study, the age range was 27 to 78 years, and only 1 patient was ⬍30 years old.
4™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™™ Figure 1. Peripapillary detachment in pathologic myopia (PDPM) and cystic spaces within the area of the conus from the right eye of a 62-year-old man. A, Fundus photograph of the right eye with a refractive error of ⫺9.5 diopters and axial length of 27.8 mm. The yellow-orange lesion around the optic disc suggests a PDPM (arrowheads). Within the area of the conus, 3 focal pitlike structures are observed (*). The temporal conus is deeply excavated and the optic disc is almost invisible. B, Photograph of the optic disc of the right eye and orientation of the 2 scans of optical coherence tomography (OCT) shown in C and D. C, Horizontal OCT scan shows hyporeflective space intrachoroidally (arrow) at the site of the PDPM seen in A. The cystic space (*) is seen at the site corresponding to the pitlike structures observed ophthalmoscopically in A. Cystic space extends posteriorly to the conus, and the cyst is opened to the vitreous body (arrowhead). D, Vertical OCT scan through a PDPM showing that this lesion consists of multiple cystic structures in the choroid (*). Figure 2. Characteristics of peripapillary detachment in pathologic myopia (PDPM) located subretinally and intrachoroidally. A, Right fundus photograph of a 62-year-old man with a refractive error of ⫺12.0 diopters and axial length of 28.7 mm showing a yellow-orange lesion inferior to the optic disc suggestive of a PDPM (arrowheads). Orientation of the 2 scans of optical coherence tomography (OCT) in B and C are shown. B, Vertical OCT scan shows a hyporeflective space intrachoroidally (arrowheads). Hyporeflective space also exists superior to the myopic conus and extends to the area within the conus. Hyporeflective space is also seen subretinally (arrow), and consists of cystic spaces (*) within the area of the conus. C, Horizontal OCT scan shows the detachment of the neural retina in the area of myopic conus (arrow). Posterior excavation of the temporal conus is prominent (arrowheads).
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Figure 3. Intrachoroidal cavity within the area of myopic conus in eyes without a yellow-orange lesion observed ophthalmoscopically. A, Right fundus of a 65-year-old woman with a refractive error of ⫺17.5 diopters and an axial length of 28.1 mm shows a large conus and diffuse chorioretinal atrophy in the posterior fundus. A yellow-orange lesion suggestive of peripapillary detachment in pathologic myopia is not observed. Orientation of the scan of optical coherence tomography (OCT) in B is shown. B, Vertical OCT scan across the nasal edge of the optic disc reveals intrachoroidal cavity (*) within the area of myopic conus.
We also reported that glaucomalike visual field defects were frequently detected in eyes with a PDPM.16 The results of the present study supported this finding, and IOP was not significantly different between eyes with and without a PDPM. Although the mechanism(s) for the concomitant visual field defects in eyes with PDPM is not clear, our findings suggest that the distorted structure of the neurosensory retina caused by the marked tilting of the optic disc might be a more important factor than the IOP. From the results obtained by Stratus OCT 3000, Toranzo et al15 reported that a PDPM was not a detachment of the RPE but a peripapillary intrachoroidal cavity separating the RPE from the sclera. In this study, OCT ophthalmoscopy showed that the yellow-orange lesion around the optic disc was an intrachoroidal hyporeflective space consisting of cystic spaces in most patients. However, in some patients the hyporeflective space was also observed between the
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RPE layer and the neural retina. In addition, a hyporeflective space was seen in some patients only posterior to the myopic conus, and the yellow-orange lesion was not seen ophthalmoscopically in these cases. These observations suggest that PDPMs may be present more frequently in eyes with high myopia than might be expected by the ophthalmoscopic observations alone. Although the pathogenesis of PDPMs has not been conclusively determined, they were frequently detected in eyes with a posterior excavation of the conus. Why a conus protrudes posteriorly is unclear; however, this area of the conus lacks the RPE and choroid and may thus be structurally weak. Therefore, when a conus enlarges, this structure might protrude posteriorly in response to the enlargement. Then, when the posterior excavation of the conus occurs, the conus and the surrounding peripapillary tissue are mechanically stretched, and this mechanical force might cause
Shimada et al 䡠 Peripapillary Changes in High Myopia
Figure 4. Peripapillary vascular microfolds and retinoschisis in eyes with myopic foveoschisis. A, Left fundus of a 44-year-old man with a refractive error of ⫺18.0 diopters and an axial length of 29.6 mm shows a large temporal conus and diffuse chorioretinal atrophy in the posterior fundus. Orientation of the scans of optical coherence tomography (OCT) in B, C, and D are shown. B, Vertical OCT scan near the temporal edge of myopic conus shows vascular microfolds (arrows) and retinoschisis (*). Retinoschisis is observed within the area of the conus as well (arrowhead). C, Vertical OCT scan between the fovea centralis and the conus shows slight vascular microfolds (arrows) and retinoschisis (*). D, Vertical OCT scan at the fovea centralis shows myopic foveoschisis (*) as well as multilayered schisis (arrowheads). Slight vascular microfolds are still observed (arrow).
a splitting of the intrachoroidal structures to produce the cystoid spaces. Later, the cystoid spaces enlarge and coalesce, and finally develop a large cystic area seen as a hyporeflective space on OCT. A splitting of the tissue in or around the peripapillary choroid in eyes with high myopia then might result in a structural weakening of the peripapillary tissue. This might decrease the ability of the tissue to absorb the mechanical pressure of the IOP changes, and thus might lead to optic nerve damage or expulsive hemorrhages in eyes with high myopia. More extensive research is required to determine whether this description is accurate. We also observed pitlike structures within the conus ophthalmoscopically, and OCT examination of these areas demonstrated the presence of cystic structures at the corresponding sites. Some of these cysts were opened to the vitreous cavity. We are unaware of any previous reports describing similar cystic structures in eyes with high myopia. The OCT images of these cystlike structures seemed similar to those of optic pits. Todokoro and Kishi17 reported
the OCT findings in a case with these pits, and they demonstrated that they were not true pits but cystic spaces covered by a superficial layer of the optic disc. The cysts were not connected to the vitreous because of the overlying superficial retinal layer. Because our patients were not examined at a younger age, we were not able to determine whether the cysts are a congenital anomaly or developed secondarily during the progression of myopia. However, the cystic space observed in our patients had 2 differences from optic pits. First, the location was different; the optic pit exists within the area of the optic disc whereas the cyst in our patients existed within the conus outside the optic disc. And second, the cyst was not covered by a superficial layer of the optic disc and was thus opened to the vitreous cavity. Also, 1 patient had a prominent excavation of the conus and a wide area of PDPM, which might suggest that a prominent mechanical extension around the optic disc might be related to the secondary development of cystic structure within the conus.
Table 1. Characteristics of Eyes with or without Vascular Microfolds at the Edge of Myopic Conus
Age (yrs) (mean ⫾ SD) Refractive error (D) (mean ⫾ SD) Axial length (mm) (mean ⫾ SD) Posterior staphyloma
With Vascular Microfolds (77 Eyes)
Without Vascular Microfolds (50 Eyes)
P Value
59.5 ⫾ 8.3 ⫺14.2 ⫾ 3.9 28.9 ⫾ 1.4 60 eyes (77.9%)
51.8 ⫾ 13.2 ⫺12.1 ⫾ 3.2 28.3 ⫾ 1.6 28 eyes (56.0%)
0.0007* 0.005* 0.02* 0.01†
D ⫽ diopters; SD ⫽ standard deviation. *Mann–Whitney U test. † Chi-square test.
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Ophthalmology Volume 114, Number 11, November 2007 However, more studies are necessary to investigate the pathogenesis of cystic structures. Sayanagi et al13 reported on the results of their OCT studies on 7 highly myopic eyes with vascular microfolds along the retinal vessels in the macular area. They suggested that the formation of the microfolds indicated a strong inward traction that resulted from an elongation of the axial length in eyes with high myopia and may be related to the pathogenesis of pathologic myopia-specific alterations such as myopic foveoschisis.13 Although they reported that the incidence of vascular microfolds in OCT scans across the fovea centralis was 2.9%, our vertical OCT scans across the fovea demonstrated that vascular microfolds were detected in 7.8%, a higher incidence than that of Sayanagi et al.13 Interestingly, our study revealed that the incidence of vascular microfolds at the conus edge was significantly higher at 45.0%. This suggests that the vascular microfolds might first develop at the edge of the conus in eyes with high myopia. Retinoschisis was detected in more than one third of the eyes at the site of the retinal vessels with microfolds. In these cases, the vascular microfolds and accompanying retinoschisis extended continuously along the retinal vessels towards the macular area, and 9 eyes eventually had myopic foveoschisis. This indicates that the inward traction of the retinal vessels in addition to the vitreoretinal traction and posterior staphyloma might be important in the pathogenesis of myopic foveoschisis. These observations also suggest that the vascular microfolds may gradually extend from the conus edge toward the macular region. This would then suggest that the vascular microfolds at the conus edge might be the first sign of an inward traction of retinal vessels, and might be a risk for the development of myopic foveoschisis. In conclusion, OCT examination identified different types of abnormalities around the optic disc in eyes with high myopia. Presumably, the formation of a posterior staphyloma and subsequent excavation of the conus might cause severe mechanical stress around the optic disc that leads to a splitting or cavitation of the subretinal tissue, mainly intrachoroidally. Also, vascular microfolds of retinal vessels frequently develop at the conus edge, and might progress toward the macula. These changes might be related to visually disabling conditions such as visual field loss or myopic foveoschisis in eyes with high myopia. Because myopic conus is one of the earliest changes seen in highly myopic eyes, the mechanical stretch might be especially prominent at and around the optic disc. Because our results revealed that the various abnormalities detected by OCT around the optic disc were related to the development of visually disabling conditions in high myopia, it is important to detect these peripapillary changes by OCT to be able to predict the later development of visually disabling conditions. Although further studies are necessary, OCT exami-
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nation has provided valuable evidence on the underlying changes that occur around the optic disc in eyes with high myopia. Acknowledgment. The authors thank Professor Duco Hamasaki for critical reading of and suggestions for the manuscript.
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