Lucie Sawides

Background: Choroidal nevi are common, benign tumors. These tumors rarely cause adverse retinal sequalae, but when they do, they can lead to disruption of the outer retina and vision loss. In this paper, we used high-resolution retinal imaging modalities, optical coherence tomography (OCT) and adaptive optics scanning laser ophthalmoscopy (AOSLO), to longitudinally monitor retinal sequelae of a submacular choroidal nevus. Methods: A 31-year-old female with a high-risk choroidal nevus resulting in subretinal fluid (SRF) and a 30-year-old control subject were longitudinally imaged with AOSLO and OCT in this study over 18 and 22 months. Regions of interest (ROI) including the macular region (where SRF was present) and the site of laser photocoagulation were imaged repeatedly over time. The depth of SRF in a discrete ROI was quantified with OCT and AOSLO images were assessed for visualization of photoreceptors and retinal pigmented epithelium (RPE). Cell-like structures that infiltrated the site of laser photocoagulation were measured and their count was assessed over time. In the control subject, images were assessed for RPE visualization and the presence and stability of cell-like structures. Results: We demonstrate that AOSLO can be used to assess cellular-level changes at small ROIs in the retina over time. We show the response of the retina to SRF and laser photocoagulation. We demonstrate that the RPE can be visualized when SRF is present, which does not appear to depend on the height of retinal elevation. We also demonstrate that cell-like structures, presumably immune cells, are present within and adjacent to areas of SRF on both OCT and AOSLO, and that similar cell-like structures infiltrate areas of retinal laser photocoagulation. Conclusions: Our study demonstrates that dynamic, cellular-level retinal responses to SRF and laser photocoagulation can be monitored over time with AOSLO in living humans. Many retinal conditions exhibit similar retinal findings and laser photocoagulation is also indicated in numerous retinal conditions. AOSLO imaging may provide future opportunities to better understand the clinical implications of such responses in vivo.

Most tunable lenses (TLs) are affected by deviations in optical power induced by external temperature changes or due to internal heating while in use. This study proposes: (1) An experimental characterization method to evaluate the magnitude of the optical power deviations due to internal temperature shifts; (2) three different mathematical models (experimental, polynomial, and optimized) to describe the response of the lens with temperature; (3) predictions of the internal temperature shifts while using the lens in time frames of minutes, seconds, and milliseconds and; (4) a real time optical power compensation tool based on the implementation of the models on a custom voltage electronic driver. The compensation methods were successfully applied to two TL samples in static and dynamic experiments and in hysteresis cycles. After 40 min at a static nominal power of 5 diopters (dpt), the internal temperature exponentially increased by 17 °C, producing an optical power deviation of 1.0 dpt (1.5 dpt when the lens cools down), representing a 20% distortion for heating and 30% for cooling. Modelling and compensation reduced the deviations to 0.2 dpt when heating (0.35 dpt when cooling) and the distortions to 4% and 7%. Similar levels of improvement were obtained in dynamic and hysteresis experiments. Compensation reduced temperature effects by more than 75%, representing a significant improvement in the performance of the lens.

Purpose: Cones are at great risk in a wide variety of retinal diseases, especially when there is a harsh microenvironment and retinal pigment epithelium is damaged. We provide established and new methods for assessing cones and retinal pigment epithelium, together with new results. We investigated conditions under which cones can be imaged and could guide light, despite the proximity of less than ideal retinal pigment epithelium. Recent findings: We used a variety of imaging methods to detect and localise damage to the retinal pigment epithelium. As age‐related macular degeneration is a particularly widespread disease, we imaged clinical hallmarks: drusen and hyperpigmentation. Using near infrared light provided improved imaging of the deeper fundus layers. We compared confocal and multiply scattered light images, using both the variation of detection apertures and polarisation analysis. We used optical coherence tomography to examine distances between structures and thickness of retinal layers, as well as identifying damage to the retinal pigment epithelium. We counted cones using adaptive optics scanning laser ophthalmoscopy. We compared the results of five subjects with geographic atrophy to data from a previous normative ageing study. Using near infrared imaging and layer analysis of optical coherence tomography, the widespread aspect of drusen became evident. Both multiply scattered light imaging and analysis of the volume in the retinal pigment epithelial layer from the optical coherence tomography were effective in localising drusen and hyperpigmentation beneath the photoreceptors. Cone photoreceptors in normal older eyes were shorter than in younger eyes. Cone photoreceptors survived in regions of atrophy, but with greatly reduced and highly variable density. Regular arrays of cones were found in some locations, despite abnormal retinal pigment epithelium. For some subjects, the cone density was significantly greater than normative values in some retinal locations outside the atrophy. Summary: The survival of cones within atrophy is remarkable. The unusually dense packing of cones at some retinal locations outside the atrophy indicates more fluidity in cone distribution than typically thought. Together these findings suggest strategies for therapy that includes preserving cones.

How brief can a visual stimulus be and still be seen? To answer this question, we developed a digital micromirror device (DMD) based system operating at high speed (22.7 kHz) to control the rapid presentation of visual stimuli and estimated the minimum time required to identify the orientation of tumbling Snellen E letters. Time thresholds were measured in five subjects using a QUEST algorithm to vary the presentation time of the letters subtending either 0.75°, 1.5° and 4.5° on the retina, for two different effective pupil sizes (0.3 and 1 mm). Additionally, to evaluate the effect of defocus on time thresholds, the experiment was repeated with 1.5° letters and induced myopic defocus with 3, 6 and 9 D trial lenses placed in a conjugated pupil plane. We found that subjects were able to identify the orientation of the letters presented as briefly as 5 ms.

In adaptive optics scanning laser ophthalmoscope (AOSLO) systems, capturing multiply scattered light can increase the contrast of the retinal microvasculature structure, cone inner segments, and retinal ganglion cells. Current systems generally use either a split detector or offset aperture approach to collect this light. We tested the ability of a spatial light modulator (SLM) as a rapidly configurable aperture to use more complex shapes to enhance the contrast of retinal structure. Particularly, we varied the orientation of a split detector aperture and explored the use of a more complex shape, the half annulus, to enhance the contrast of the retinal vasculature. We used the new approach to investigate the influence of scattering distance and orientation on vascular imaging.

Retinal imaging with an adaptive optics (AO) system usually requires that the eye be centered and stable relative to the exit pupil of the system. Aberrations are then typically corrected inside a fixed circular pupil. This approach can be restrictive when imaging some subjects, since the pupil may not be round and maintaining a stable head position can be difficult. In this paper, we present an automatic algorithm that relaxes these constraints. An image quality metric is computed for each spot of the Shack–Hartmann image to detect the pupil and its boundary, and the control algorithm is applied only to regions within the subject’s pupil. Images on a model eye as well as for five subjects were obtained to show that a system exit pupil larger than the subject’s eye pupil could be used for AO retinal imaging without a reduction in image quality. This algorithm automates the task of selecting pupil size. It also may relax constraints on centering the subject’s pupil and on the shape of the pupil.

Purpose: We measured localized changes occurring in the foveal cone photoreceptors and related defects in the cone mosaic to alterations in the nearby retinal vasculature. Methods: The central 4° of the retina of 54 diabetic (53.7 ± 12.5 years) and 85 control (35.8 ± 15.2 years) participants were imaged with the Indiana adaptive optics scanning laser ophthalmoscope. Foveal cones and overlying retinal capillaries were imaged and infrared scanning laser ophthalmoscopy (IR SLO) images and optical coherence tomography (OCT) B-scans were obtained. Follow-up imaging sessions were performed with intervals from 4 to 50 months for 22 of the 54 diabetic participants. Results: The foveal cone mosaics of 49 of 54 diabetic participants were of sufficient quality to assess the absence or presence of small localized defects in the cone mosaic. In 13 of these 49 diabetic participants we found localized defects, visualized as sharp-edged areas of cones with diminished reflectivity. These small, localized areas ranged in size from 10 × 10 μm to 75 × 30 μm. Of these 13 participants with cone defects, 11 were imaged over periods from 4 to 50 months and the defects remained relatively stable. These dark regions were not shadows of overlying retinal vessels, but all participants with these localized defects had alterations in the juxtafoveal capillary network. Conclusions: The foveal cone mosaic can show localized areas of dark cones that persist over time, that apparently correspond to either missing or nonreflecting cones, and may be related to local retinal ischemia.

This publisher’s note amends the author affiliations of a recent publication [Biomed. Opt. Express 7, 4388 (2016)].