Retromode Retinal Imaging of Macular Retinoschisis in Highly Myopic Eyes




Purpose


To determine the characteristics of a macular retinoschisis using noninvasive retromode imaging by a new, commercial confocal scanning laser ophthalmoscope (F10; Nidek, Aichi, Japan) and to compare the findings with those obtained by conventional optical coherence tomography (OCT).


Design


Open-label, consecutive, interventional case series.


Methods


Sixty-six consecutive highly myopic eyes were examined by multiple scans of the posterior fundus within the retinal vascular arcade using the Cirrus OCT (Carl Zeiss Meditec, Oberkochen, Germany). The retinas also were examined with the F10.


Results


OCT examinations showed that 22 (33.3%) of the 66 eyes had a macular retinoschisis. Retromode imaging by F10 showed a characteristic fingerprint pattern at the corresponding area of the macular retinoschisis in all 22 eyes. The fingerprint pattern consisted of radiating retinal striae centered on the fovea and many light dots and lines that ran in parallel to the striae or formed a whorled pattern surrounded the radiating striae. Two patients had both inner and outer retinoschisis, and the border between them was outlined as a change in the course of the linear reflex by the retromode imaging. Also, an inner lamellar hole was found in 2 patients and was observed as a circular defect of the deep retinal reflex by the retromode imaging. In contrast, the 44 eyes that did not have a macular retinoschisis by OCT showed no abnormal findings by F10.


Conclusions


Retromode imaging by F10 shows characteristic alteration of the retina that corresponds to the site of the macular retinoschisis.


Amacular retinoschisis is present in 9% to 34% of highly myopic eyes with a posterior staphyloma, and it has been suggested that a macular retinoschisis is a precursor lesion of more severe retinal complications, such as a macular hole and foveal detachment. It is difficult to detect a macular retinoschisis ophthalmoscopically in highly myopic eyes because of the thinness of the retina and the accompanying chorioretinal atrophy.


Optical coherence tomography (OCT) has been the only method that can reliably detect a macular retinoschisis. OCT images of a macular retinoschisis show a splitting of the neurosensory retina into a thin outer retinal layer lying on the retinal pigment epithelium and a thicker inner retinal layer. The 2 layers are connected by bridging column-like structures. In addition to this so-called outer retinoschisis, OCT examinations have shown that a macular retinoschisis can be accompanied by an inner retinoschisis or tractional internal limiting membrane detachment in 2.4% of the patients. This retinal defect probably results from the high rigidity or proliferative response of the internal limiting membrane.


Although OCT has provided valuable information on the morphologic features of a macular retinoschisis, some problems remain when OCT is used to study macular retinoschisis. First, the extent or the area of a macular retinoschisis is determined by a cross-section of the lesion in the line scan mode of the OCT, and this may fail to detect the full extent of a macular retinoschisis unless the scans happens to pass through the entire extent of the lesion. Serial OCT sections are helpful in detecting not only macular retinoschisis, but also the area of a macular retinoschisis. However, multiple scans require a considerable amount of time, and it is also difficult to obtain serial images in patients with poor fixation because of myopic chorioretinal atrophy, a common lesion associated with a macular retinoschisis.


To improve the detection rate of a macular retinoschisis, we previously performed multiple OCT scans of the entire posterior fundus within the retinal vascular arcade. However, this technique required a considerable amount of time, and the patients had to maintain good fixation during the examination. It was also essential to have an experienced examiner (N.S.) perform the scans and read the OCT images.


The F10 (Nidek, Aichi, Japan) is a new, commercially available scanning laser confocal ophthalmoscope (SLO) that can perform multiple functions including fluorescein angiography, indocyanine green angiography, fundus autofluorescence, retromode imaging, and dark-field mode imaging. In the dark-field mode with a central stop, scattered light from the deeper layers of the retina silhouette the structural abnormalities. In contrast, the retromode of the F10 SLO uses an infrared laser and an aperture with a modified central stop. The aperture is displaced laterally from the confocal light path. This optical arrangement allows for a clearer and pseudo–3-dimensional image, which is a new method of detecting abnormalities in the deeper retinal layers. The retromode imaging enables investigators to observe the details of deep retinal structures noninvasively and clearly by illuminating the fundus with an infrared laser and collecting the scattered light reflected from the retina, choroid, and sclera through a semicircular and pericentral aperture by a new confocal technique.


A PubMed search did not extract any articles describing the properties of a macular retinoschisis obtained by instruments other than OCT. Thus, the purpose of this study was to determine the presence and characteristics of a macular retinoschisis using retromode imaging of the F10 SLO and to compare the findings with those obtained by OCT. We show that a macular retinoschisis has a characteristic appearance in the retromode retinal images, and the sites of these alterations correspond to that of a macular retinoschisis obtained by multiple OCT scans. This suggests that the F10 SLO can be used to determine the presence and extent of a macular retinoschisis.


Methods


Thirty-three consecutive highly myopic patients (66 eyes) who visited the High Myopia Clinic at Tokyo Medical and Dental University between February 27 and March 27, 2009, were studied. A comprehensive ocular examination, including measurements of the refractive error (spherical equivalent) and axial length, dilated ophthalmoscopy with macular examinations with a contact lens or a 78-diopter (D) lens, color fundus photography, OCT, and noninvasive retromode imaging by F10 SLO, was performed.


The Cirrus OCT (Carl Zeiss Meditec, Oberkochen, Germany) was used to detect the presence and extent of a macular retinoschisis. The entire area of posterior fundus within the retinal arcade vessels was scanned carefully with the 5-line mode and a 512 × 128-volume cube (each image had a 5-μm axial and 10-μm transverse resolution) by moving a fixation point, as described in detail.


After completing the OCT scans of the entire fundus area within the vascular arcade, the fundus was examined by the retromode imaging by F10 SLO. In the retromode imaging, infrared laser (790 nm) light was used to scan the fundus under nonmydriatic conditions in a noninvasive way. The F10 only acquires 1 photograph of the entire posterior fundus using the retromode imaging settings, whereas a complete OCT scan of the entire posterior fundus within the vascular arcade takes at least 1 minute in patients who can maintain a good fixation during the examination.


High myopia was defined as a myopic refractive error of more than −8 D or an axial length ≥ 26.5 mm. Eyes with the most advanced degree of myopia (> −15 D) were excluded because the range of the focus of the F10 was within ± 15 D. Also, patients with dense cataracts were excluded because of the difficulty in obtaining clear images by F10 and OCT.




Results


There were 27 men and 6 women who met the inclusion criteria for this study. The mean age of the patients was 59.0 ± 12.7 years with a range of 20 to 84 years. The mean refractive error (except for eyes with an implanted intraocular lens) was −12.7 ± 1.9 D, with a range of −7.75 to −15.0 D. The mean axial length was 29.4 ± 1.3 mm, with a range of 26.6 to 34.4 mm.


OCT examinations of the posterior fundus showed that 22 (33.3%) of the 66 eyes had a macular retinoschisis ( Table ). The macular retinoschisis extended over the fovea in 16 of the 22 eyes, and the macular retinoschisis was peripheral to the fovea in the remaining 6 eyes. Neither a retinal detachment nor a macular hole was detected in any of the 22 eyes with a macular retinoschisis by OCT.


Jan 17, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Retromode Retinal Imaging of Macular Retinoschisis in Highly Myopic Eyes
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