Light path-length distributions within the retina.

A Monte Carlo simulation of light propagation through the retina has been developed to understand the path-length distributions within the retinal vessel. For full-field illumination, the path-length distribution within the vessel comprises directly backscattered light and light that has passed once or twice through the vessel. The origins of these light path-length distributions can be better understood by investigating different combinations of single-point illumination and detection positions. Perhaps the most significant observation is that illumination at the edges of the vessel, rather than over the whole field of view, and detection directly above the vessel capture only the light that has taken a single pass through the vessel. This path-length distribution is tightly constrained around the diameter of the vessel and can potentially provide enhancements for oxygen saturation imaging. The method could be practically implemented using an offset-pinhole confocal imaging system or structured light illumination.

Noncontact high-resolution ultra-wide-field oral fluorescein angiography in premature infants with retinopathy of prematurity.

IMPORTANCE: We report for the first time, to our knowledge, the acquisition of noncontact ultra-wide-field oral fluorescein angiograms in premature infants with retinopathy of prematurity. OBSERVATIONS: High-resolution oral fluorescein angiograms were successfully obtained in 3 consecutive premature infants with retinopathy of prematurity at the Oxford Eye Hospital, Oxford, England, using the Optos Panoramic 200MA imaging system (Optos PLC). CONCLUSIONS AND RELEVANCE: Noncontact ultra-wide-field oral fluorescein angiograms captured using the Optos Panoramic 200MA fluorescein angiographic system provide a safe and alternative method for evaluating the retinal vasculature in premature infants with retinopathy of prematurity.

Non-contact ultra-widefield retinal imaging and fundus fluorescein angiography of an infant with incontinentia pigmenti without sedation in an ophthalmic office setting.

When fluorescein angioscopy or angiography is required in an infant, it is usually performed in the operating theater or neonatal unit. We report a case of an infant with incontinentia pigmenti in whom we were able to acquire angiographic information in an office setting by using an ultra-widefield non-contact system with oral fluorescein.

Validation of human whole blood oximetry, using a hyperspectral fundus camera with a model eye.

PURPOSE: To assess the accuracy of human blood oximetry measurements in a model eye with a hyperspectral fundus camera. METHODS: Seven human whole blood samples (two arterial, five venous) were obtained, the oxygen saturations measured with a CO oximeter, and the samples inserted into quartz tubes with internal diameters of 100 and 150 µm. The tubes (n = 20; ten 100 µm and ten 150 µm) were placed within a model eye in front of a background reflectance surface with reflectivities of 20%, 60%, and 99%. Spectral images at wavelengths between 500 and 650 nm were acquired with a hyperspectral fundus camera and analyzed with an oximetric model to calculate the oxygen saturation of blood within the tubes. The calculated oxygen saturations were compared with the measured oxygen saturations. The effects of the background reflectivity and tube size on the accuracy of the calculated oxygen saturations were evaluated. RESULTS: Background reflectivity and tube size had no significant effect on the mean oxygen saturation difference (P = 0.18 and P = 0.99, respectively; repeated-measures, two-way ANOVA). The mean differences (SD) between the measured and calculated oxygen saturations in segments of the 100 and 150 µm tubes overlying the 20%, 60%, and 99% background reflectivities were (100 µm) -4.0% (13.4%), -6.4% (9.9%), and -5.5% (10.2%) and (150 µm) -5.3% (10.8%), -5.2% (10.7%), and -5.2% (10.9%), respectively. CONCLUSIONS: There was reasonable agreement between the measured oxygen saturation values and those calculated by the oximetry model. The oximetry model could be used to determine the functional health of the retina.