Reports Imaging of the Temporal Raphe with Optical Coherence Tomography There has been considerable debate about the arrangement and composition of the temporal raphe in the human retina. In postmortem studies, Vrabec1 showed that axons of retinal ganglion cells temporal to the fovea are forced to take an arched course above and below the papillomacular bundle and that the temporal raphe generally represents a watershed midline. However, there is scarce published literature on the relationship between the orientation of the papillomacular bundle and the temporal raphe. It is logical to assume that, if the papillomacular bundle defines the geometric axis of the axon bundles and if axons cannot cross the midline, the orientation of the temporal raphe should be very similar to that of the papillomacular bundle. This report had 2 objectives. First, we present images acquired with a spectral-domain optical coherence tomographyebased technique to visualize the temporal raphe (Fig 1). Second, we report the orientation of the temporal raphe with respect to (i) the orientation of the image frame and (ii) the axis connecting the fovea and the center of Bruch’s membrane opening (FoBMO; the anatomic outer limits through which axons exit the eye), termed the FoBMO axis,2 which can vary by as much as 20 in normal eyes (Chauhan BC, et al. Characteristics of an anatomically and geometrically accurate neuroretinal rim parameter in a normal population: A multi-centre study. Paper presented at the Annual ARVO Meeting, May 7, 2014, Orlando, Florida). This study enrolled 15 healthy subjects (median age, 48 years; range, 21e70) with a normal ophthalmic examination and visual field (Mean Deviation and Glaucoma Hemifield Test within normal limits). They gave informed consent and the study was approved by the Capital Health Ethics Review Board. One randomly selected eye was imaged with spectral-domain optical coherence tomography (Spectralis, Heidelberg Engineering, Heidelberg, Germany) with 2 scanning protocols. In the first, 24 radial B-scans through the optic nerve head were obtained. The BMO was segmented in each of the 48 positions (2 per scan) and the center of the closed surface defined by the BMO points was taken as the BMO center. Next, the position of the foveal pit was determined with a B-scan that originated at the BMO center, establishing the FoBMO axis.2 In the second, a 30 15 highdensity volume scan centered on the fovea consisting of 391 horizontal B-scans, 11 mm apart, was obtained. Eye tracking was enabled to ensure optimal registration of the B-scans and each B-scan was averaged from 9 individual scans. Analysis software (Transverse Section Analysis v. 6.0.0.6, Heidelberg Engineering) utilized the method for en face visualization of reflectance images at the various reference planes determined by retinal layer segmentation.3 In this case, the reference plane was set at the nerve fiber layer. Each image was triplicated and the resulting 45 images coded and presented randomly to 2 independent observers who identified the fovea and then extended a line along the temporal raphe and computed the temporal raphe angle (TRA), relative to the fovea and the fixed horizontal of the image frame, with computer
Figure 1. En face visualization of the temporal raphe of the right eye of a 52-year-old healthy subject. The en face image is generated from high density (11 mm separation) horizontal spectral-domain optical coherence tomography B-scans between the 2 dashed white lines. The papillomacular bundle is visible around the fovea (arrow), while temporally, the nerve fiber bundles assume a more horizontal course above and below the temporal raphe. The image is very similar to the histological studies of Vrabec,1 including the triangular area of irregular bundles temporal to the fovea (T).
software (Fig 2, available at www.aaojournal.org). All data were converted to right eye format. The orientation of the temporal raphe could not be made on the pattern of the retinal vasculature because of the significant interdigitation of the vessels originating from the superior and inferior hemiretinas, leading to a large variability in the subjective assessment of the angle. The en face visualization technique clearly shows the orientation of the papillomacular bundle and the temporal raphe, not visible in the infrared image (Fig 1). We believe this technique also enables, for the first time, in vivo visualization of the “triangular area” containing irregular bundles temporal to the fovea (Fig 1), described by Vrabec1 in postmortem human retinas stained supravitally with methylene blue. The mean within-observer unsigned difference between the 3 possible paired TRA estimates was 0.35 and 0.61 for observers 1 and 2, respectively, and the maximum and minimum differences were 0.52 and 0.92 , and 0.15 and 0.23 , respectively. The mean between-observer unsigned difference in mean TRA was 0.72 , and the minimum and maximum were 0.03 and 2.67 , respectively. The orientation of the temporal raphe is neither maintained according to the FoBMO axis, nor is it horizontal (Fig 3A, available at www.aaojournal.org). Instead, it is oriented more positively relative to the FoBMO axis (Fig 3B, available at www.aaojournal.org). There was a significant relationship between the FoBMO axis and
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Ophthalmology Volume 121, Number 11, November 2014 the TRA (P < 0.01 for each observer; Fig 3A, available at www.aaojournal.org), but the TRA, relative to the FoBMO axis, was independent of the FoBMO axis (Fig 3B, available at www.aaojournal.org; P > 0.55). Because of the large interindividual variation in the FoBMO axis, we have previously argued that image acquisition and regionalization of the optic nerve head and the retinal nerve fiber layer (RNFL) should be performed relative to the FoBMO axis.2 The current data illustrate the separate and considerable interindividual variability in the TRA, even relative to the FoBMO axis (Fig 3B; available at www.aaojournal.org). Interindividual variability of the TRA has a bearing on how accurately the visual field is mapped to optic nerve head and RNFL sectors. Currently, most mapping methods assume there is no variation in the correspondence between the visual field and neuroretinal rim and RNFL sectors. Some investigators have proposed customized visual field maps based on axial length, optic nerve head position, and dimension.4 The large interindividual variation in the FoBMO axis and TRA underscores the importance of their inclusion into customized visual field mapping to increase its clinical utility and allow better elucidation of the relationship between visual field loss and neuroretinal rim or RNFL loss in glaucoma. The major finding of this reportdthat the temporal raphe does not conform to the geometric axis defined by the papillomacular bundle, is perplexing from the standpoint of ocular development. It suggests that, if the FoBMO axis and TRA are determined from the time neural connections in the visual pathway are established, then axons of retinal ganglion cells situated temporal to the fovea would not necessarily course along the shortest path to the optic nerve head, given the constraints of the watershed midline defined by the raphe and the papillomacular bundle, neither of which can presumably be traversed by these axons. These findings could suggest acquired changes in the relative positions of the optic nerve head and fovea, with the temporal retina being relatively less affected. Recent data indicate no relationship between the FoBMO angle and age in healthy adults (Chauhan BC, et al. Characteristics of an anatomically and geometrically accurate neuroretinal rim parameter in a normal population: A multi-centre study. Paper presented at the Annual ARVO Meeting, May 7, 2014, Orlando, Florida); therefore, these structural alterations may occur in early development, perhaps as the fovea is being established. Profound changes in optic nerve head configuration, initiated by scleral stretching in childhood myopia, have been reported5; hence, other positional changes could also occur.
BALWANTRAY C. CHAUHAN, PHD GLEN P. SHARPE, MSC DONNA M. HUTCHISON, BSC Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada Financial Disclosure(s): B.C. Chauhan: Grant Support e Heidelberg Engineering; Honoraria, Speaker Fees, Travel e Allergan. Supported by grants MOP11357 (B.C.C.) from the Canadian Institutes of Health Research, Ottawa, Ontario, and equipment and unrestricted research support from Heidelberg Engineering, Heidelberg, Germany. Correspondence: Balwantray C. Chauhan, PhD, Department of Ophthalmology and Visual Sciences, Dalhousie University, 1276 South Park Street, 2W
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Victoria, Room 2035, Halifax, Nova Scotia, B3H 2Y9, Canada. E-mail: [email protected].
References 1. Vrabec F. The temporal raphe of the human retina. Am J Ophthalmol 1966;62:926–38. 2. Chauhan BC, Burgoyne CF. From clinical examination of the optic disc to clinical assessment of the optic nerve head: a paradigm change. Am J Ophthalmol 2013;156:218–27. e2. 3. Srinivasan VJ, Adler DC, Chen Y, et al. Ultrahigh-speed optical coherence tomography for three-dimensional and en face imaging of the retina and optic nerve head. Invest Ophthalmol Vis Sci 2008;49:5103–10. 4. Denniss J, McKendrick AM, Turpin A. An anatomically customizable computational model relating the visual field to the optic nerve head in individual eyes. Invest Ophthalmol Vis Sci 2012;53:6981–90. 5. Kim TW, Kim M, Weinreb RN, et al. Optic disc change with incipient myopia of childhood. Ophthalmology 2012;119:21–6. e1e3.
Visual Acuity Outcome in RADIANCE Study Patients With Dome-Shaped Macular Features Recently, dome-shaped macula (DSM) has been described in patients with pathologic myopia. The DSM has been identified in optical coherence tomography (OCT) scans, fundus biomicroscopy, and ultrasonography, and is characterized by an inward bulge inside the chorioretinal posterior concavity of the eye in macular area.1 The pathophysiology of DSM is not known precisely, but several theories have been published. These include localized choroidal thickening, scleral infolding, and vitreomacular traction.1,2 Dome-shaped macula may be associated with atrophy of the retinal pigment epithelium, subfoveal fluid, and visual loss. In this study, baseline OCT scans from all patients included in the RADIANCE study3 were analyzed for DSM. Additionally, it was explored if the DSM is a predictive factor for visual outcome of therapy for myopic choroidal neovascularization (CNV). The design of the RADIANCE study has been described in detail elsewhere.3 A post hoc analysis was performed for the retrospectively defined subgroup of patients with the DSM feature present in the study eye at baseline (n ¼ 277). Presence of DSM feature on OCT scans was determined on the first study visit for all patients included into the full analysis set of the RADIANCE study. We analyzed OCT scans for the presence of an unusual feature of the macular profile. We defined DSM as the presence of a convex, curved, elevated profile within the concavity of the macula (Figure 1). Outcomes of this subanalysis were changes in best-corrected visual acuity at 3 and 12 months, compared with baseline. Outcomes were evaluated in all patients who completed the RADIANCE study using the last observation carried forward method (n ¼ 276). All data were analyzed with IBM Statistical software (SPSS 17, IBM Inc, Chicago, IL) and presented in tables. The research followed the tenets of the Declaration of Helsinki. Institutional review board approval was granted.
Figure 1. En face visualization of the temporal raphe of the right eye of a 52-year-old healthy subject. The en face image is generated from high density (11 mm separation) horizontal spectral-domain optical coherence tomography B-scans between the 2 dashed white lines. The papillomacular bundle is visible around the fovea (arrow), while temporally, the nerve fiber bundles assume a more horizontal course above and below the temporal raphe. The image is very similar to the histological studies of Vrabec,1 including the triangular area of irregular bundles temporal to the fovea (T).
software (Fig 2, available at www.aaojournal.org). All data were converted to right eye format. The orientation of the temporal raphe could not be made on the pattern of the retinal vasculature because of the significant interdigitation of the vessels originating from the superior and inferior hemiretinas, leading to a large variability in the subjective assessment of the angle. The en face visualization technique clearly shows the orientation of the papillomacular bundle and the temporal raphe, not visible in the infrared image (Fig 1). We believe this technique also enables, for the first time, in vivo visualization of the “triangular area” containing irregular bundles temporal to the fovea (Fig 1), described by Vrabec1 in postmortem human retinas stained supravitally with methylene blue. The mean within-observer unsigned difference between the 3 possible paired TRA estimates was 0.35 and 0.61 for observers 1 and 2, respectively, and the maximum and minimum differences were 0.52 and 0.92 , and 0.15 and 0.23 , respectively. The mean between-observer unsigned difference in mean TRA was 0.72 , and the minimum and maximum were 0.03 and 2.67 , respectively. The orientation of the temporal raphe is neither maintained according to the FoBMO axis, nor is it horizontal (Fig 3A, available at www.aaojournal.org). Instead, it is oriented more positively relative to the FoBMO axis (Fig 3B, available at www.aaojournal.org). There was a significant relationship between the FoBMO axis and
2287
Ophthalmology Volume 121, Number 11, November 2014 the TRA (P < 0.01 for each observer; Fig 3A, available at www.aaojournal.org), but the TRA, relative to the FoBMO axis, was independent of the FoBMO axis (Fig 3B, available at www.aaojournal.org; P > 0.55). Because of the large interindividual variation in the FoBMO axis, we have previously argued that image acquisition and regionalization of the optic nerve head and the retinal nerve fiber layer (RNFL) should be performed relative to the FoBMO axis.2 The current data illustrate the separate and considerable interindividual variability in the TRA, even relative to the FoBMO axis (Fig 3B; available at www.aaojournal.org). Interindividual variability of the TRA has a bearing on how accurately the visual field is mapped to optic nerve head and RNFL sectors. Currently, most mapping methods assume there is no variation in the correspondence between the visual field and neuroretinal rim and RNFL sectors. Some investigators have proposed customized visual field maps based on axial length, optic nerve head position, and dimension.4 The large interindividual variation in the FoBMO axis and TRA underscores the importance of their inclusion into customized visual field mapping to increase its clinical utility and allow better elucidation of the relationship between visual field loss and neuroretinal rim or RNFL loss in glaucoma. The major finding of this reportdthat the temporal raphe does not conform to the geometric axis defined by the papillomacular bundle, is perplexing from the standpoint of ocular development. It suggests that, if the FoBMO axis and TRA are determined from the time neural connections in the visual pathway are established, then axons of retinal ganglion cells situated temporal to the fovea would not necessarily course along the shortest path to the optic nerve head, given the constraints of the watershed midline defined by the raphe and the papillomacular bundle, neither of which can presumably be traversed by these axons. These findings could suggest acquired changes in the relative positions of the optic nerve head and fovea, with the temporal retina being relatively less affected. Recent data indicate no relationship between the FoBMO angle and age in healthy adults (Chauhan BC, et al. Characteristics of an anatomically and geometrically accurate neuroretinal rim parameter in a normal population: A multi-centre study. Paper presented at the Annual ARVO Meeting, May 7, 2014, Orlando, Florida); therefore, these structural alterations may occur in early development, perhaps as the fovea is being established. Profound changes in optic nerve head configuration, initiated by scleral stretching in childhood myopia, have been reported5; hence, other positional changes could also occur.
BALWANTRAY C. CHAUHAN, PHD GLEN P. SHARPE, MSC DONNA M. HUTCHISON, BSC Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada Financial Disclosure(s): B.C. Chauhan: Grant Support e Heidelberg Engineering; Honoraria, Speaker Fees, Travel e Allergan. Supported by grants MOP11357 (B.C.C.) from the Canadian Institutes of Health Research, Ottawa, Ontario, and equipment and unrestricted research support from Heidelberg Engineering, Heidelberg, Germany. Correspondence: Balwantray C. Chauhan, PhD, Department of Ophthalmology and Visual Sciences, Dalhousie University, 1276 South Park Street, 2W
2288
Victoria, Room 2035, Halifax, Nova Scotia, B3H 2Y9, Canada. E-mail: [email protected].
References 1. Vrabec F. The temporal raphe of the human retina. Am J Ophthalmol 1966;62:926–38. 2. Chauhan BC, Burgoyne CF. From clinical examination of the optic disc to clinical assessment of the optic nerve head: a paradigm change. Am J Ophthalmol 2013;156:218–27. e2. 3. Srinivasan VJ, Adler DC, Chen Y, et al. Ultrahigh-speed optical coherence tomography for three-dimensional and en face imaging of the retina and optic nerve head. Invest Ophthalmol Vis Sci 2008;49:5103–10. 4. Denniss J, McKendrick AM, Turpin A. An anatomically customizable computational model relating the visual field to the optic nerve head in individual eyes. Invest Ophthalmol Vis Sci 2012;53:6981–90. 5. Kim TW, Kim M, Weinreb RN, et al. Optic disc change with incipient myopia of childhood. Ophthalmology 2012;119:21–6. e1e3.
Visual Acuity Outcome in RADIANCE Study Patients With Dome-Shaped Macular Features Recently, dome-shaped macula (DSM) has been described in patients with pathologic myopia. The DSM has been identified in optical coherence tomography (OCT) scans, fundus biomicroscopy, and ultrasonography, and is characterized by an inward bulge inside the chorioretinal posterior concavity of the eye in macular area.1 The pathophysiology of DSM is not known precisely, but several theories have been published. These include localized choroidal thickening, scleral infolding, and vitreomacular traction.1,2 Dome-shaped macula may be associated with atrophy of the retinal pigment epithelium, subfoveal fluid, and visual loss. In this study, baseline OCT scans from all patients included in the RADIANCE study3 were analyzed for DSM. Additionally, it was explored if the DSM is a predictive factor for visual outcome of therapy for myopic choroidal neovascularization (CNV). The design of the RADIANCE study has been described in detail elsewhere.3 A post hoc analysis was performed for the retrospectively defined subgroup of patients with the DSM feature present in the study eye at baseline (n ¼ 277). Presence of DSM feature on OCT scans was determined on the first study visit for all patients included into the full analysis set of the RADIANCE study. We analyzed OCT scans for the presence of an unusual feature of the macular profile. We defined DSM as the presence of a convex, curved, elevated profile within the concavity of the macula (Figure 1). Outcomes of this subanalysis were changes in best-corrected visual acuity at 3 and 12 months, compared with baseline. Outcomes were evaluated in all patients who completed the RADIANCE study using the last observation carried forward method (n ¼ 276). All data were analyzed with IBM Statistical software (SPSS 17, IBM Inc, Chicago, IL) and presented in tables. The research followed the tenets of the Declaration of Helsinki. Institutional review board approval was granted.
