[Changes of photoreceptor layer on spectral domain optical coherence tomography in idiopathic macular hole after vitreous surgery combined with air tamponade].

OBJECTIVE: To evaluate the tamponade effect of sterilized air in vitrectomy for idiopathic macular hole (IMH) as well as changes of photoreceptor layer after surgery. METHODS: Forty-five eyes of 45 consecutive cases underwent vitrectomy and air tamponade. Surgical outcomes were retrospectively analyzed, consisting of logarithm of the minimal angle of resolution (logMAR) and SD-OCT findings including the size of IMH and the photoreceptor layer defect. RESULTS: Preoperatively, mean BCVA was 0.08 (range, 0.4 to HM), mean hole diameter was 827.4 µm (range, 204 to 1616 µm), and mean diameter of photoreceptor layer defect was 1988.9 µm (range, 792 to 3444 µm). The primary closure rate was 75.6%. One month after surgery, mean BCVA was 0.13 (range, 0.5 to LP), and mean diameter of photoreceptor layer defect was 1285.1 µm (range, 166 to 2553 µm), both presenting a significant decrease. Preoperative hole diameter and postoperative diameter of photoreceptor layer defect were statistically significantly correlated with postoperative BCVA (r = 0.526, 0.628; P < 0.05). CONCLUSIONS: Vitrectomy plus air tamponade is safe and effective for the treatment of IMH, and the time for face-down positioning is obviously shortened. Preoperative hole diameter and postoperative diameter of photoreceptor layer defect are major predictive factors of visual acuity.

High-resolution ultrasonography of subretinal structure and assessment of retina degeneration in rat.

The purpose of this work was to evaluate the ability of 80 MHz ultrasonography to differentiate intra-retinal layers and quantitatively assess photoreceptor dystrophy in small animal models. Four groups of 10 RCS rats each (five dystrophic and five controls) were explored at 25, 35, 45 and 55 days post-natal (PN). A series of retina cross-sections were obtained ex vivo from outside intact eyes using an 80 MHz three-dimensional ultrasound backscatter microscope (20-microm-axial resolution). Ultrasound features of normal retina were correlated to those of corresponding histology and thickness measurements of photoreceptor segment and nuclear layers were performed on all groups. To show the ability of 80 MHz ultrasonography to distinguish the retinal degeneration in vivo, one RCS rat was explored at 25 and 55 days post-natal. Ultrasound image of normal retina displayed four distinct layers marked by reflections at neurites/nuclei interfaces and permitted to differentiate the photoreceptor segment and nuclear layers. The backscatter level from the retina was shown to be related to the size, density and organization of the intra-layer structure. Ultrasound thickness measurements highly correlated with histologic measurements. A thinning (p<0.05) of outer nuclear layer (ONL) was detected over time for controls and was thought to be assigned to retina maturation. Retinal degeneration started at PN35 and resulted in a more pronounced ONL thinning (p<0.05) over time. ONL degeneration was accompanied by segment layer thickening (p<0.05) at PN35 and thinning thereafter. These changes may indicate accumulation of outer segment debris at PN35 then progressive destruction. In vivo images of rat intra-retinal structure showed the ability of the method to distinguish the photoreceptor layer changes. Our results indicate that 80 MHz ultrasonography reveals intra-retinal layers and is sensitive to age and degenerative changes of photoreceptors. This technique has great potential to follow-up retinal dystrophy and therapeutic effects in vivo.

X-ray analysis of retinal photoreceptors.

A series of low-angle X-ray reflections have been recorded from photoreceptors in four types of intact untreated retinae. The retinae were maintained in a living condition during the X-ray exposure. The X-ray reflections arise from the regular arrangement of disk membranes within the photoreceptors. The recorded X-ray intensities contain information on the onedimensional electron-density distribution of the photoreceptors. An electrondensity model which is in good agreement with the low-angle X-ray data has been derived.