|Year : 2013 | Volume
| Issue : 2 | Page : 13-17
Optical coherence tomography findings in high myopia
Amir Ramadan Gomaa, Mahmoud Alaa Abouhussein
Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt
|Date of Web Publication||24-Jun-2014|
Mahmoud Alaa Abouhussein
9, Emarat Hayat Eltadress, Smoha, Alexandria
Source of Support: None, Conflict of Interest: None
Purpose: The purpose of this study is to describe the incidence and features of macular abnormalities in high myopic eyes detected by optical coherence tomography (OCT). Patients and Methods: This was a prospective observational study that involved 100 eyes of 100 patients with high myopia complaining of recent diminution of vision. OCT examination was done through dilated pupils, OCT examination was done through a dilated pupil using commercially available Cirrus HD-OCT Model 4000 - Carl Zeiss Meditec, Inc., Dublin, California, USA or Spectralis OCT Heidelberg Engineering, Heidelberg, Germany. Results: A total of 100 eyes of 100 patients were studied. There were 45 males and 55 females. The mean age of the patients was 52.9 ± 12.9 (range: 33-70) years. Mean spherical equivalent in these eyes was 14.5 ± 5.8 (range: 8.75-22.75) diopters. Epiretinal membrane was present in 65 eyes. Vitreomacular traction (anteroposterior traction) was detected in 10 eyes. Macular retinoschisis was present in 33 eyes. Conclusion: Macular changes detected by OCT are common pathological findings in high myopia.
Keywords: High myopia, optical coherence tomography, retinoschisis
|How to cite this article:|
Gomaa AR, Abouhussein MA. Optical coherence tomography findings in high myopia. Egypt Retina J 2013;1:13-7
| Introduction|| |
Degenerative myopia also called pathologic or high myopia is defined as a myopic refractive error of more than 6 diopters (D) associated with degenerative fundus changes. The main feature of degenerative myopia is a congenital scleral weakness leading to progressive globe enlargement, axial lengthening, and finally the formation of posterior staphyloma. 
Following this scleral stretching, degenerative changes such as progressive atrophy of the choriocapillaris and choroid, linear ruptures of the Bruch membrane (lacquer cracks), and retinal thinning can occur. Other typical features of degenerative myopia are vitreous degeneration and high frequency of peripheral retinal lesions such as lattice degeneration and retinal tears. 
Apart from these causes of visual loss in eyes with high myopia, the posterior retina can also be damaged by the presence of traction induced by the epiretinal membrane (ERM) or residual focal vitreoretinal adhesion (vitreomacular traction), which in these eyes is combined by the presence of posterior staphyloma and progressive global scleral stretching. This unique combination of retinal traction mixed with the complex and distinctive anatomy of degenerative myopia leads to the frequent presence of myopic traction maculopathy (MTM) such as retinoschisis, lamellar holes, or shallow detachment and may also play an important role in the pathogenesis of macular hole formation and posterior retinal detachment. 
Because of the characteristic and confounding features of the choroid, retina, and vitreoretinal interface in degenerative myopia (tigroid fundus, thin retina, areas of choriocapillaris atrophy, retinal pigment epithelium (RPE) hypopigmentation and/or hyperpigmentation, posterior staphyloma), the early stages of traction maculopathy can be easily underestimated by biomicroscopy, angiography, or ultrasonography, and consequently, its presence can remain undiagnosed. Optical coherence tomography (OCT) greatly facilitates the study of the posterior vitreoretinal anatomy in eyes with high myopia and allows the detection of subtle macular changes that are otherwise undetectable. 
The purpose of this study is to describe the incidence and features of macular abnormalities in high myopic eyes detected by OCT.
| Patients and Methods|| |
This was a prospective observational study that involved 100 eyes of 100 patients with high myopia complaining of recent diminution of vision. Patients were recruited from the outpatient clinic of Alexandria University Hospital.
The research protocol was approved by the Alexandria University Institutional Review Board and Ethics Committee.
Inclusion criteria were a minimum spherical equivalent (SE) of -6.0 D and recent complaint of diminution of vision. Patients with ocular or systemic disease that could affect the retina (glaucoma-diabetic mellitus) were excluded from the study. All patients with previous intraocular surgery or history of trauma were also excluded. We excluded 130 eyes due to lack of recent complaint of diminution of vision.
All patients were subjected to a detailed history taking, refraction using Topcon autorefractometer and best corrected visual acuity (VA) measurement. All patients had complete ophthalmic examination including biomicroscopic fundus examination with 90 D lens and indirect ophthalmology with 20 D, fundus photography, and fluorescein angiography using Topcon camera.
Optical coherence tomography examination was done through dilated pupils, OCT examination was done through a dilated pupil using commercially available Cirrus HD-OCT Model 4000 - Carl Zeiss Meditec, Inc., Dublin, California, USA or Spectralis OCT Heidelberg Engineering, Heidelberg, Germany. We used the vertical and horizontal 6-mm line scans. All abnormal macular findings were documented, and all the images were evaluated by two-blinded graders.
Macular retinoschisis was defined as a separation of intraretinal layers, predominantly outer layers by a low reflective space that is separated by an erect columnar microstructure. The ERMs observed in this study appeared as noticeable layer over the inner surface of the retina, and at the same time, internal limiting membrane (ILM) could be distinguished as well at the same cut below the ERM. ILM detachment was associated with Mόller cell columns that bridge from ILM to the rest of the retinal layers. Dome shaped macula was characterized as an inward convexity of the macula that occurred within the concavity of a posterior staphyloma. Myopic choroidal neovascularization (CNV) was defined by OCT as the neovascular tuft with a highly reflective dome-shape elevation above the RPE.
| Results|| |
A total of 100 eyes of 100 patients were studied. We included only eyes with a recent complaint of diminution of vision. There were 45 males and 55 females and 60% of the studied eyes were the right eyes. The mean age of the patients was 52.9 ± 12.9 (range: 33-70) years. Mean SE in these eyes was 14.5 ± 5.8 (range: 8.75-22.75) D. The mean best corrected VA was 0.235 ± 0.2 (0.05-0.5).
All eyes had one or more chorioretinal features typical of degenerative myopia (tigroid fundus, stretched vascular arcades, peripapillary atrophy, chorioretinal atrophy, and lacquer cracks). On biomicroscopy, complete posterior vitreous detachment with a Weiss ring which was mobile in the vitreous cavity was obvious in 15 eyes. Posterior staphyloma was detected in 75 eyes. Greyish lesion at the macula was detected in 12 eyes.
Optical coherence tomography macular findings were recorded [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]. ERM was present in 65 eyes. Vitreomacular traction (anteroposterior traction) was detected in 10 eyes. Macular retinoschisis was present in 33 eyes. Multiple columnar structures were seen widely within the retinoschisis as long straight highly reflective lines at the fovea and throughout the retinoschisis.
Lamellar macular hole was present in 10 eyes. Full-thickness macular hole was present in four eyes. Posterior sensory retinal detachment was present in two eyes. ILM detachment was present in seven eyes. Dome shaped macula was detected in five eyes. Myopic CNV was present in 15 eyes. Atrophy of retinal layers was detected in 10 eyes [Table 1].
| Discussion|| |
Spectral domain (SD)-OCT has made it possible to discover macular changes which go unseen in conventional biomicroscopic examination and which give rise to unexplained low VA values. 
In 2004, Panozzo and Mercanti  retrospectively reviewed their medical records and OCT findings for 125 eyes with high myopia. They found epiretinal traction in 58 eyes (46.4%) and retinal damage in 43 eyes (34.4%), of which 36 had epiretinal traction (83.7%). They were the first to use the term "MTM" to refer to these pathologies of the posterior pole in high myopia, such as macular retinoschisis, shallow retinal detachment without retinal holes, lamellar macular holes, and macular holes with or without retinal detachment. Distinguishing these conditions from epiretinal traction syndromes found in eyes without myopia was an important advancement because their distinct features have significantly different clinical effects on retinal tissue and visual function. Tangential traction in the form of ERM was the most common finding in our study group.
In 2007, Panozzo and Mercanti  suggested that the term "retinoschisis" used in the literature for high myopic maculopathy was not appropriate as the terms inner or outer retinal schisis suggested a complete separation between the retinal layers that resulted in the irreversible and total loss of retinal function. Since all of the previously published case series of foveal retinoschisis reported good visual improvement without fixed scotoma, this retinal damage is not a schisis, but rather due to retinal swelling with the accumulation of fluid. Smiddy  supported this theory and suggested that myopic maculoschisis, foveal schisis, and vitreoschisis in high myopia should all fall under the family of MTM. In support of this idea, we noticed that all macular retinoschisis cases in our study had columnar structures bridging the hyporeflective space.
Optical coherence tomography has shown that myopic macular retinoschisis (also called foveoschisis) is not uncommon in highly myopic eyes. Retinoschisis was detected in 9-34% of highly myopic eyes with a posterior staphyloma. Based on the OCT features of untreated and treated eyes, the pathogenesis of myopic macular retinoschisis has been attributed to strong traction on the retina exerted by residual posterior vitreous cortex, an ILM, retinal vessels, or a combination of these. ,,,,,,,
Axial length elongation and/or formation of posterior staphyloma in highly myopic eyes may generate the inward tractional force exerted by these factors. This is strongly supported by the remission of the retinoschisis after vitrectomy combined with ILM peeling, which theoretically releases the tractional forces exerted by the posterior vitreous cortex and the ILM and partly by the retinal vessels in the area from which the ILM was peeled. 
Enhanced SD-OCT images enabled improved visualization of the fine structures associated with macular retinoschisis, such as multiple columnar structures. Shimada et al.  suggested in a longitudinal study of five eyes with retinoschisis that progressed to a foveal retinal detachment using time-domain OCT that inward traction was transmitted to the outer retina through the foveal columnar structures in the retinoschisis layer.
The cause of the ILM detachment is still uncertain. In the current study, the ILM detachments were always in the peripheral macula where there were retinal vessels including arterioles. Inward traction generated by retinal vasculature as a result of ocular elongation may cause myopic macular retinoschisis. Ikuno et al.  showed that retinal microfolds commonly form after vitrectomy combined with ILM peeling as a result of residual inward traction exerted by the retinal arterioles in highly myopic eyes. We recorded ILM detachment in seven eyes all extrafoveal in location.
Several other studies have attempted to determine the prevalence of macular changes in high myopia by OCT. Baba et al.  looked at 134 eyes of 78 consecutive patients with high myopia, with and without visual symptoms, attending a high myopia clinic in Tokyo. This study looked for the particular feature of foveal retinal detachment without macular hole, which is thought to be a precursor to macular hole formation. They found the prevalence for foveal retinal detachment of 9% (seven eyes). All seven eyes with foveal retinal detachment also showed severe myopic fundus changes (focal chorioretinal atrophy or bare sclera), with vision ranging from better than 20/50 to below 20/200. Surprisingly, two eyes showed better VA than 20/50, suggesting that in eyes with shallow retinal detachments, oxygen and nutrient diffusion from the choriocapillaris to the photoreceptors might be sufficient, allowing the photoreceptors to survive to some extent. 
Takano and Kishi  found a much higher prevalence of foveal retinal detachment, with 34% of highly myopic eyes with posterior staphyloma showing foveal retinal detachment or retinoschisis. However, the study group was much smaller, only 32 eyes, and also included pseudophakic patients, who are at a greater risk of retinal detachment following cataract surgery. In our study, we excluded pseudophakic cases and we had posterior sensory retinal detachment in only two eyes.
Based on OCT, a dome-shaped macula was first described by Gaucher et al.  as an unexpected finding in myopic staphyloma and was characterized as an inward convexity of the macula that occurred in highly myopic eyes within the concavity of a posterior staphyloma. They suggested that the dome-shaped macula may be the result of changes in choroidal thickness or to changes in scleral shape in highly myopic eyes. Subsequently, Imamura et al.,  by using enhanced depth imaging OCT, reported that the dome-shaped macula is the result of a localized variation in thickness of the sclera in the macular area. In our study, we found dome shaped macula in five eyes.
| Conclusion|| |
Macular changes detected by OCT are common findings in patients with high myopia, and should be considered as a separate cause of visual loss. Accordingly, it would be recommendable to routinely obtain high definition OCT macular images for all high myopic patients in the context of their routine ophthalmological examination to detect early changes.
| References|| |
|1.||Balacco-Gabrieli C. Aetiopathogenesis of degenerative myopia. A hypothesis. Ophthalmologica 1982;185:199-204. |
|2.||Takano M, Kishi S. Foveal retinoschisis and retinal detachment in severely myopic eyes with posterior staphyloma. Am J Ophthalmol 1999;128:472-6. |
|3.||Panozzo G, Mercanti A. Optical coherence tomography findings in myopic traction maculopathy. Arch Ophthalmol 2004;122:1455-60. |
|4.||Smiddy WE, Kim SS, Lujan BJ, Gregori G. Myopic traction maculopathy: spectral domain optical coherence tomographic imaging and a hypothesized mechanism. Ophthalmic Surg Lasers Imaging 2009;40:169-73. |
|5.||Panozzo G, Mercanti A. Vitrectomy for myopic traction maculopathy. Arch Ophthalmol 2007;125:767-72. |
|6.||Benhamou N, Massin P, Haouchine B, Erginay A, Gaudric A. Macular retinoschisis in highly myopic eyes. Am J Ophthalmol 2002;133:794-800. |
|7.||Bando H, Ikuno Y, Choi JS, Tano Y, Yamanaka I, Ishibashi T. Ultrastructure of internal limiting membrane in myopic foveoschisis. Am J Ophthalmol 2005;139:197-9. |
|8.||Matsumura N, Ikuno Y, Tano Y. Posterior vitreous detachment and macular hole formation in myopic foveoschisis. Am J Ophthalmol 2004;138:1071-3. |
|9.||Polito A, Lanzetta P, Del Borrello M, Bandello F. Spontaneous resolution of a shallow detachment of the macula in a highly myopic eye. Am J Ophthalmol 2003;135:546-7. |
|10.||Sayanagi K, Ikuno Y, Gomi F, Tano Y. Retinal vascular microfolds in highly myopic eyes. Am J Ophthalmol 2005;139:658-63. |
|11.||Sayanagi K, Ikuno Y, Tano Y. Reoperation for persistent myopic foveoschisis after primary vitrectomy. Am J Ophthalmol 2006;141:414-7. |
|12.||Shimada N, Ohno-Matsui K, Baba T, Futagami S, Tokoro T, Mochizuki M. Natural course of macular retinoschisis in highly myopic eyes without macular hole or retinal detachment. Am J Ophthalmol 2006;142:497-500. |
|13.||Gaucher D, Haouchine B, Tadayoni R, Massin P, Erginay A, Benhamou N, et al. Long-term follow-up of high myopic foveoschisis: Natural course and surgical outcome. Am J Ophthalmol 2007;143:455-62. |
|14.||Ikuno Y, Sayanagi K, Ohji M, Kamei M, Gomi F, Harino S, et al. Vitrectomy and internal limiting membrane peeling for myopic foveoschisis. Am J Ophthalmol 2004;137:719-24. |
|15.||Shimada N, Ohno-Matsui K, Yoshida T, Futagami S, Tokoro T, Mochizuki M. Development of macular hole and macular retinoschisis in eyes with myopic choroidal neovascularization. Am J Ophthalmol 2008;145:155-61. |
|16.||Ikuno Y, Gomi F, Tano Y. Potent retinal arteriolar traction as a possible cause of myopic foveoschisis. Am J Ophthalmol 2005;139:462-7. |
|17.||Baba T, Ohno-Matsui K, Futagami S, Yoshida T, Yasuzumi K, Kojima A, et al. Prevalence and characteristics of foveal retinal detachment without macular hole in high myopia. Am J Ophthalmol 2003;135:338-42. |
|18.||Gaucher D, Erginay A, Lecleire-Collet A, Haouchine B, Puech M, Cohen SY, et al. Dome-shaped macula in eyes with myopic posterior staphyloma. Am J Ophthalmol 2008;145:909-14. |
|19.||Imamura Y, Iida T, Maruko I, Zweifel SA, Spaide RF. Enhanced depth imaging optical coherence tomography of the sclera in dome-shaped macula. Am J Ophthalmol 2011;151:297-302. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]