Cone Outer Segment Tips Research Articles

High-Resolution In Vivo Imaging in Achromatopsia

To characterize the retinal changes in patients with achromatopsia using an ultrahigh-resolution (UHR) spectral-domain optical coherence tomography (OCT) to examine how human achromatopsia corresponds to its animal model. Comparative case series. Ultrahigh-resolution OCT (Copernicus; OPTOPOL Technology S.A., Zawiercie, Poland; 3-μm axial resolution) was used to obtain scans from 13 patients (26 eyes) with achromatopsia and from 20 controls (40 eyes). A 3-dimensional scan program (743×75; A×B scan) sampling a 7×7-mm retinal area centered at the fovea was used to obtain tomograms of the fovea. Individual B-scans at the fovea were exported and analyzed using ImageJ (Wayne Rasband, National Institute of Health) for reflectance profiles and morphologic abnormalities. Gross morphologic changes in OCT were characterized. Specifically, inner segment and outer segment (IS/OS) junction and cone outer segment tip (COST) disruption was noted. Using the reflectance profiles, foveal depth, thickness of the outer nuclear layer (ONL), and retinal thickness (RT) were measured. A characteristic so-called punched out hyporeflective zone (HRZ) was noted in 7 of 13 patients; this was age-dependent (P = 0.001). The area of the HRZ was asymmetric with the nasal area being significantly greater than the temporal area (P = 0.002). In all patients, there was disruption of the IS/OS junction at the foveal or parafoveal regions, or both. Five of 13 patients also had a disrupted COST reflectivity. There was significant (P = 1.1×10(-6)) ONL thinning in the achromats compared with controls, which was age-dependent (P = 0.0002). Foveal maldevelopment was seen in 9 of 13 patients. The achromats also had a significantly reduced foveal depth (P = 7.7×10(-6)) and RT (P = 1.46×10(-9)) compared with controls. A range of signs in achromatopsia are described that can be detected using UHR OCT. The IS/OS junction and COST reflectivity disruption and presence of HRZ and ONL thinning are signs of cone photoreceptor degeneration. The latter 2 are age-dependent, which suggests that achromatopsia is a progressive disorder. In addition, foveal maldevelopment is described; this represents a fetal developmental defect linked to cone photoreceptor degeneration.

STAGE 1-A MACULAR HOLE

To determine the anatomical morphology of Stage 1-A impending macular holes characterized by a yellow spot using spectral-domain optical coherence tomography to study the fellow eyes of patients diagnosed with a full-thickness macular hole or eyes with a typical yellow spot with metamorphopsia. Prospective observational case series of 45 patients with a full-thickness macular hole or a foveolar yellow spot with metamorphopsia. Visual acuity assessment, biomicroscopic examination, and spectral-domain optical coherence tomography were performed. Clinical ophthalmologic examinations were repeated, including spectral-domain optical coherence tomography, in the eyes with a foveolar yellow spot at 1-month interval. We examined 43 fellow eyes of 43 patients with a macular hole and 2 eyes of 2 patients with a foveolar yellow spot. Five fellow eyes had a yellow spot. Spectral-domain optical coherence tomography clearly showed the reflectivity of the perifoveal posterior vitreous detachment with vitreofoveal adhesion in the 7 eyes with a yellow spot; the foveal microstructure had a triangular foveolar detachment of the cone outer segment tip line, of which only 2 eyes (29%) had foveal splits during the observational period, 3 eyes (43%) had a foveal perpendicular line, and 4 eyes (57%) showed progression to vitreofoveal separation before the development of inner splits or pseudocysts. In those 7 eyes, the 2 eyes (29%) with foveal splits progressed to a full-thickness macular hole. The 38 fellow eyes without a yellow spot had no foveolar detachment. The foveolar detachment of the cone outer segment tip line might be responsible for the yellow spot seen in Stage 1-A macular holes.

Morphologic Photoreceptor Abnormality in Occult Macular Dystrophy on Spectral-Domain Optical Coherence Tomography

PURPOSE. To investigate morphologic photoreceptor layer abnormalities and their correlation with visual function in occult macular dystrophy (OMD), by using spectral-domain optical coherence tomography (SD-OCT). METHODS. This observational case series included 18 eyes of 9 patients with OMD. All patients underwent an ophthalmic evaluation, which included a fundus examination, fluorescein angiography, full-field electroretinography (ERG), multifocal ERG, time-domain optical coherence tomography (TD-OCT), and visual field testing. Morphologic photoreceptor layer abnormalities of the retinal layers were investigated with SD-OCT. The structure-function relationship was investigated regarding visual acuity, symptom duration, and multifocal ERG RESULTS: RESULTS. Best corrected visual acuity ranged from 20/200 to 20/20. Four patients had a symmetric decline of acuity in both eyes (20/200-20/100), and five had unilateral vision impairment (20/200-20/50). TD-OCT showed foveal thinning in all patients, but revealed no other retinal layer abnormality. In 15 eyes of 8 patients, SD-OCT demonstrated a well-defined disruption of the inner segment-outer segment (IS-OS) junction of the photoreceptors and of the Verhoeff membrane (cone outer segment tips). SD-OCT showed that three of five patients with presumed unilateral OMD had bilateral OMD after initial or follow-up examinations. Degrees of abnormality in the photoreceptor layer varied and correlated with visual acuity and symptom duration. CONCLUSIONS. SD-OCT can demonstrate the disruption of photoreceptors in most patients with OMD and the morphologic changes on SD-OCT correlate with visual function and disease progression. These morphologic abnormalities can be an important feature and cause of vision loss in patients with OMD.