Purpose
To explore the structural features of juvenile X-linked retinoschisis using spectral-domain optical coherence tomography (OCT).
Design
Retrospective, observational cross-sectional study.
Methods
Eighteen male patients (34 eyes) who were diagnosed with juvenile X-linked retinoschisis at the Eye & ENT Hospital of Fudan University over an 18-month period were included. Their OCT images, which were obtained using spectral-domain OCT (Cirrus HD-OCT; Carl Zeiss Meditec), were analyzed. The anatomic location of the schisis cavity in juvenile X-linked retinoschisis was characterized by direct inspection of OCT images.
Results
On OCT, the schisis cavity was visible at the fovea in all 34 eyes, and it was associated with increased retinal thickness. Schisis was present at the retinal nerve fiber layer in 4 eyes, at the inner nuclear layer in 29 eyes, and at the outer nuclear layer/outer plexiform layer in 22 eyes. In most cases, widespread foveomacular schisis was detected using OCT; however, in 9 eyes (6 patients), the schisis was confined to the fovea. Schisis of the inner nuclear layer and outer nuclear layer/outer plexiform layer almost always involved the foveal center, but retinal nerve fiber layer schisis was seen only in the parafoveal area.
Conclusions
Despite conventional wisdom, in patients with X-linked retinoschisis, the schisis cavity can occur in a number of different layers of the neurosensory retina (retinal nerve fiber layer, inner nuclear layer, and outer nuclear layer/outer plexiform layer). In addition, different forms of schisis may affect different locations in the macula (foveal vs parafoveal), and, in most eyes, the schisis involves the entire foveomacular region.
Juvenile X-linked retinoschisis has been referred to as congenital hereditary retinoschisis , congenital vascular veil , vitreous veils , and cystic disease of the retina in children . On clinical examination, a bilateral cyst-like stellate maculopathy or foveal schisis is present in every case and may be associated with inferotemporal retinoschisis in approximately 50% of patients. Early histopathologic studies reported splitting of the retinal nerve fiber layer (RNFL) and ganglion cell layers (GCLs) ; however, these reports did not provide information regarding the early stages of foveal schisis, and in vivo imaging of fine retinal structures was not available at the time.
With the advent of optical coherence tomography (OCT), it is possible to obtain high-resolution cross-sectional images of the neurosensory retina in a noninvasive manner, and thus, to characterize many forms of retinal pathologic features. Using OCT, the typical cystic maculopathy of juvenile X-linked retinoschisis has been examined previously. However, the location of schisis cavity within the neuroretina varied between difference studies, including the inner nuclear layer (INL), outer plexiform layer (OPL), and the outer nuclear layer (ONL). Interestingly, extramacular OCT scans have demonstrated schisis nearer the RNFL. Despite these studies, much remains to be learned about the evolution of the structural changes seen in this disorder, in particular the anatomic association between foveal and peripheral retinoschisis. Recently, the introduction of spectral-domain OCT, offering higher axial resolution (approximately 6 μm), has afforded new opportunities to explore the morphologic features of this disorder. In this study, we used high-speed spectral-domain OCT to localize the foveal schisis cavities that occur in patients with juvenile X-linked retinoschisis and to characterize further the structural features of this disorder.
Methods
Eighteen male patients (34 eyes) who were diagnosed with juvenile X-linked retinoschisis at the Eye & ENT Hospital of Fudan University, Shanghai, from May 2008 through October 2009 and who previously underwent OCT imaging were identified. Their medical records reviewed, and the following information was collected: family history, personal medical history, best-corrected visual acuity, and details of clinical examination. For each case, color fundus photographs, fluorescein angiograms, and electroretinogram reports also were collected where available.
All OCT images were obtained through a dilated pupil using a spectral-domain system, Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, California, USA). The Cirrus HD-OCT images were acquired using both the macular cube and the 5-line raster scanning protocols. Segmentation of the inner and outer retinal boundaries, and thus macular thickness measurement, is provided by the macular cube protocol, whereas the high-definition 5-line raster protocol typically is used for qualitative assessments. The anatomic location of the schisis cavity in each case was characterized by direct inspection of OCT images.
Fluorescein angiography was performed using the Zeiss Digital Image Archiving System VISUPAC/System 450 (Carl Zeiss Jena GmbH, Jena, Germany); electroretinograms were recorded using the Visual Evoked Response Imaging System VERISTM Clinic 4.9 (Electro Diagnostic Imaging, Inc., San Mateo, California, USA). Best-corrected visual acuities were measured using a standard Snellen chart and were converted to logarithm of the minimal angle of resolution units for the purpose of statistical analysis.
Results
All 18 patients (34 eyes; age range, 5 to 48 years) were males without family history with the exception of a single case who had a brother diagnosed with X-linked retinoschisis at another hospital. All 18 patients were affected bilaterally with the exception of 2 patients: one was a 48-year-old patient who had phthisis bulbi at presentation secondary to vitreous hemorrhage, and the other was a 12-year-old boy with unilateral vitreous hemorrhage that precluded OCT examination. OCT images were available for all 34 eyes; in addition, 10 eyes underwent fluorescein angiography, and 8 eyes underwent electroretinography.
In 18 eyes, the macula had the characteristic microcystoid appearance of beaten copper on clinical examination. Macular change was the only finding in 25 eyes, whereas a vitreous veil also was present at the mid periphery in the other 9 eyes. In the 10 eyes that underwent fluorescein angiography, there was a window defect at the macula or in the mid periphery, but there was no leakage in the macula. In the 8 eyes that underwent electroretinography, the A-wave in 6 eyes was minimally affected, whereas the amplitudes of the B-wave were markedly decreased, and the implicit times were delayed. In the other 2 eyes, both the A- and B-waves were substantially affected. The B-to-A ratio was decreased in all patients.
On OCT, a schisis cavity was visible at the fovea in all 34 eyes and was associated with increased retinal thickness. In each case, the retina was divided into multiple layers by the schisis cavity, with retinal elements evident bridging the layers ( Figure 1 , Top left and Top right). In 4 eyes from 3 cases, a retinal detachment localized at the central fovea also was observed ( Figure 1 , Bottom left). Schisis was evident at different layers of the retina. The high-resolution images provided by Cirrus HD-OCT allow precise delineation of the intraretinal layers and, thus, allow direct localization of the schisis cavity in each case. The schisis cavity was located in 3 discrete locations: superficial, RNFL; middle, inner nuclear layer (INL); and outer, junction of the outer nuclear layer (ONL) and outer plexiform layer (OPL). Of all the 34 eyes, schisis was present at the RNFL in 4 eyes, at the INL in 29 eyes, and at the ONL/OPL junction in 22 eyes. In 14 eyes, the schisis at the INL and the ONL/OPL coexist. And in 1 eye ( Figure 1 , Bottom right), the schisis at the INL and ONL/OPL merged into 1 large schisis cavity in the paramacular area. In 4 eyes with schisis at the RNFL, 2 had another schisis at the ONL/OPL and 2 were accompanied by schisis at both the INL and ONL/OPL. Besides the schisis cavity, in 15 eyes from 9 cases, small cysts within the ganglion cell layer were found ( Figure 1 , Bottom right, and Figure 2 ). These small cysts were rather isolated and confined to the parafoveal area and were not considered to be a schisis cavity.
Finally, our OCT findings demonstrated that the location of the schisis cavity in the posterior fundus may vary in patients with juvenile X-linked retinoschisis. In 25 eyes of 15 patients, widespread foveomacular schisis was detected using OCT. However, in 9 eyes (6 patients), the schisis was confined to the fovea. In 3 cases, the schisis was confined to the fovea in 1 eye, whereas it involved the entire posterior pole in another eye. In 1 of these 3 cases, the schisis involved the entire foveomacular region of the right eye (with associated visual symptoms for 4 years), but was confined to the foveal center in the left eye (with associated visual symptoms of 3 months’ in duration; Figure 3 ). Moreover, schisis of the INL and ONL/OPL almost always involves the central fovea, but RNFL schisis was seen only in the parafoveal area ( Figure 4 ).
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