In vivo evaluation of photoreceptor mosaic in type 2 idiopathic macular telangiectasia using adaptive optics
Year: 2010
Type: article
Abstract: Editor, Type 2 idiopathic macular telangiectasia (IMT) is a retinal disease of unknown cause that commonly present in the fifth to seventh decade (Gass & Blodi 1993). Optical coherence tomography (OCT) reveals intraretinal cavities and disruptions at the level of outer retinal layers (Cohen et al. 2007). Adaptive optics (AO) technology leads to acquisition of high-resolution retinal images and allows visualizing the mosaic of cone photoreceptors or retinal pigment epithelium cells (Roorda et al. 2007). Our purpose was to describe the AO characteristics in a patient with IMT. An otherwise healthy 55- year-old woman presented with progressive loss of visual acuity in both eyes since 2 years. Visual acuity was 20/32 in the right eye and 20/40 in the left eye. Fundus biomicroscopy revealed right-angled venules, and intraretinal pigment migration in the parafoveal area, predominantly temporal to the fovea of both eyes. Fluorescein angiography (Heidelberg Retina Angiograph HRA; Heidelberg Engineering, Heidelberg, Germany) revealed telangiectatic parafoveal capillaries in the early phase with increasing diffuse hyperfluorescence in the late angiographic phase (Fig. 1). High-definition spectral domain optical coherence tomography (Spectralis SD-OCT; Heidelberg Engineering, Heidelberg, Germany) showed foveal cysts, as well as disruption of the outer retinal layers [the external limiting membrane, the photoreceptors (IS/OS junction) and retinal pigment epithelium] mainly temporal to the fovea (Fig. 1). Based on these findings, the patient was diagnosed with type 2 IMT. Fluorescein angiography of the right eye shows telangiectatic parafoveal capillaries in the early phase (left panel) with increasing hyperfluorescence in the late angiographic phase (right panel). In this patient, retinal images of the right eye were taken with the Imagine-Eyes (Imagine Eyes, Orsay, France) flood-illumination AO ophthalmoscope at the 3°–8° temporal to the fixation point. The AO device corrects ocular wavefront aberrations in closed-loop operation at 10 Hz, based on a 52-actuator electromagnetic deformable mirror and a 1024 lenslet Shack-Hartmann sensor. Simultaneously, a square 4° × 4° area of the fundus is flood-illuminated by a pulsed LED at 850 nm that returns the information through the deformable mirror onto a low-noise CCD camera (Roper Scientific, Ottobrunn, Germany). Each acquisition provides a series of 20 consecutive reflectance images. Ten of them were selected, registered and averaged to produce a final enhanced image. Normally, macular cones are seen as the bright spots on AO images. In this case, AO revealed an overall rarefaction of macular cones, and disruption of the continuity of the photoreceptor mosaic within 5° to the fixation point, and complete absence of macular cones in a circumscribed area between 3° and 5° temporal to the fixation point (Fig. 2). This area showing loss of macular cones on AO well corresponded to the lesion as visualized by fundus biomicroscopy, fluorescein angiography, and spectral domain OCT. Retinal examination by AO showed normal cone layout and photoreceptor mosaic outside the 5° to the fixation point (Fig. 2). Infrared reflectance and corresponding high-definition spectral domain optical coherence tomography (Spectralis SD-OCT, Heidelberg Engineering, Heidelberg, Germany) scan of the right eye showing foveal cysts, as well as disruption at the level of the outer retinal layers (external limiting membrane, the photoreceptors [inner segments/outer segments junction] and retinal pigment epithelium) mainly in the temporal macula. Adaptive optics reveals complete absence of the photoreceptor mosaic in a circumscribed area at 3° temporal to the fixation point (AO 3° T), as well as rarefaction of macular cones at 5° nasal to the fixation point (AO 5° N). Adaptive optics shows normal cone layout (visualized as regularly spaced small bright dots) and photoreceptor mosaic at 8° nasal to the fixation point (AO 8° N). Note intraretinal pigment migration that appears as a dark spot on adaptive optics image (small asterisk). Time domain OCT has shown new specific findings in type 2 IMT that may represent important steps in the evolution of the disease process (Cohen et al. 2007). AO is a noninvasive technique that allows observing retinal pathology directly at a cellular level and provides a measure of photoreceptor loss in retinal diseases. In our patient with type 2 IMT, AO showed an overall rarefaction and disruption of the continuity of the photoreceptor mosaic within 5° to the fixation point. Similar findings have been recently reported (Povazay et al. 2009) using AO OCT. In our case, AO displayed also disappearance of macular cones in correspondence to an area showing on SD OCT presence of intraretinal cysts and disruption of IS/OS junction. However, we cannot exclude that the apparent disappearance of macular cones could be attributed to alterations in the mosaic, which change the ability of the cones to wave-guide light. In conclusion, AO ophthalmoscopy and SD-OCT in tandem create a more powerful imaging approach than either alone which may help establishing an early diagnosis of type 2 IMT and may improve therapeutic approach to the disease.
Source: Acta Ophthalmologica
Institution: Hôpital Intercommunal de Créteil
Language: English
Subfield: Ophthalmology
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2012143011