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S. Ishiko, E. Sato, Y. Kato, H. Kagokawa, A. Takamiya, F. J. Van de Velde, J. Akita, A. Yoshida; Changes in Fundus Appearance Relate to the Area of the Off-Central Aperture in the Scanning Laser Ophthalmoscope. Invest. Ophthalmol. Vis. Sci. 2010;51(13):283.
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© ARVO (1962-2015); The Authors (2016-present)
To study the changes in fundus appearance relating to the area of the confocal aperture that is off-centered from the optical axis "retro mode" in the scanning laser ophthalmoscope (SLO).
Twenty-three eyes of 19 patients (mean age ± SD, 66.3±7.3 years) with macular disease were included: six eyes with drusen or age-related macular degeneration (AMD), seven eyes with branch retinal vein occlusion (BRVO), two eyes with an epiretinal membrane (ERM), five eyes with a macular hole (MH), and three eyes with other diseases. The Digital Ophthalmoscope F-10 (Nidek, Gamagori, Japan) was used for this study. The retro-mode images were obtained with a confocal aperture 10 mm in diameter at the detector, with a second confocal aperture of the same diameter juxtapositioned. Only in the area of overlap of the two confocal apertures light can be backscattered from the fundus. The width of the area of overlap can be varied from 2.5 mm (commercial size) to 10 mm in 0.5-mm increments;.The "retro mode" contribution to imaging is predominant up to 4.5 mm overlap, and the confocal mode contribution would be dominant when the overlap exceeds 5 mm.
Imaging of deeper tissue layers as in AMD and imaging of cystoid macular edema in AMD or BRVO, improved because of a higher contrast obtained with the larger size of the area of overlap and increased confocal contribution. Surface details in retinal folds in ERMs and MHs were enhanced by addinng some confocal contribution as in the retro-mode. Drusen sometimes were more distinctly seen as a result of the confocal aperture that blocked the choroidal contribution.
Changes in fundus appearance depend on the size of the area of overlap of the two apertures in retro-mode. Adding the confocal contribution to the retro-mode imaging results in improved visualization of the retinal surface pathology or selectively blocks the contribution from the choroid. Selecting the appropriate size of the aperture area in retro-mode depending can improve the quality of the fundus imaging.
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