Abstract
Purpose: :
To improve detection and localization of pathological changes in the retinas of diabetic patients using noninvasive, near infrared imaging. To compare subtle pathology across near infrared imaging modalities: the Laser Scanning Digital Camera (LSDC) in confocal and indirect modes, Spectral Domain Optical Coherence Tomography (SD-OCT) with en face imaging, and Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO).
Methods: :
Ten patients (6 females, 4 males, mean age 63 yr) with diabetes, but without clinically significant macular edema or proliferative retinopathy, were imaged with the LSDC and SD-OCT without mydriasis. The confocal mode of the LSDC had 1 megapixel resolution for a 36 deg field. The FD-OCT (Spectralis, Heidelberg Engineering) used the dense macular grid. Pathological changes were spatially compared between the en face images and b-scans. Exudative lesions were further studied with the indirect mode of the LSDC, and the 2nd generation Indiana AOSLO that has 2.4 micron lateral resolution. The AOSLO results were compared with a sample of 10 control subjects (mean age 57 yr), using a + pattern that sampled + 10 deg through the macula.
Results: :
The LSDC demonstrated regions of reflectivity changes across the macula consistent with edema, and also vascular changes, that were confirmed on the b-scan of the FD-OCT. Changes were not confined to superficial retinal layers, with locations also clearly in photoreceptor or RPE layers on OCT, yet distinct from drusen and retinal vessel artifact. Indirect mode imaging showed large areas of scattered light in the macula, corresponding spatially with the reflectivity changes. On AO-SLO, darker, round cystic changes were localized, some > 200 microns, and clearest in the focal plane of cones. Control subjects had at most 1 similar structure of < 30 microns for this focal plane, e.g. where large expanses of cones were visible.
Conclusions: :
The LSDC and FD-OCT demonstrate presence of exudative changes that are sub-clinical, possibly because some are deep. These changes clearly disrupt photoreceptors and other neural elements. AO-SLO further demonstrates multiple focal cystic lesions and vascular changes.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • diabetic retinopathy • photoreceptors