New Wrinkles in Retinal Densitometry

Masella, Benjamin; Hunter, Jennifer J.; Williams, David R.

doi:10.1167/iovs.13-13795

Cited by 17 publications

(35 citation statements)

References 43 publications

(60 reference statements)

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“…We have previously published details about the experimental preparation and the two primates used in this investigation. 11 Before each imaging experiment, the animal was injected with ketamine (18-21.5 mg/kg), glycopyrrolate (0.017 mg/kg), ketofen (5 mg/kg) and, when available, valium (0.25 mg/kg). During imaging, the animal was intubated and anesthetized with isoflurane gas.…”

Section: Animal Preparationmentioning

confidence: 99%

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Rod Photopigment Kinetics After Photodisruption of the Retinal Pigment Epithelium

Masella

Hunter

Williams

2014

Invest. Ophthalmol. Vis. Sci.

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At higher RREs, optical path length through the outer segments was reduced. However, the rate of photopigment regeneration was unchanged. While some ambiguity remains as to the correlation between measured reflectivity and absolute rhodopsin density; at the lowest RREs, RPE disruption appears not to be accompanied by a loss of apparent rhodopsin density, which would have been indicative of functional loss.

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Section: Animal Preparationmentioning

confidence: 99%

“…Retinal densitometry provides an objective way to estimate photopigment optical density and kinetics. [2][3][4][5][6][7][8][9][10] Masella et al 11 recently described a retinal densitometer integrated into an adaptive optics scanning light ophthalmoscope (AOSLO) that is capable of resolving single cells in the living primate eye.…”

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confidence: 99%

Rod Photopigment Kinetics After Photodisruption of the Retinal Pigment Epithelium

Masella

Hunter

Williams

2014

Invest. Ophthalmol. Vis. Sci.

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“…Using this model to calculate the free electron density generated with the tested exposure at the focal spot by rearranging Eq. (3), every laser pulse with a peak power of 214 W generates 10 …”

Section: C) Plasma Formationmentioning

confidence: 99%

“…Objective methods currently used to assess outer retinal function include electroretinography [5,6] and rhodopsin densitometry [7]. However, in both techniques, several retinal layers contribute to the signal, generating artifacts and complicating data interpretation [8][9][10]. To facilitate the diagnosis and prognosis of retinal diseases as well as the assessment of therapeutic interventions, more reliable, noninvasive methods are needed to evaluate retinal function.…”

Section: Introductionmentioning

confidence: 99%

Safety assessment in macaques of light exposures for functional two-photon ophthalmoscopy in humans

Schwarz¹,

Sharma²,

Fischer³

et al. 2016

Biomed. Opt. Express

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Two-photon ophthalmoscopy has potential for in vivo assessment of function of normal and diseased retina. However, light safety of the sub-100 fs laser typically used is a major concern and safety standards are not well established. To test the feasibility of safe in vivo two-photon excitation fluorescence (TPEF) imaging of photoreceptors in humans, we examined the effects of ultrashort pulsed light and the required light levels with a variety of clinical and high resolution imaging methods in macaques. The only measure that revealed a significant effect due to exposure to pulsed light within existing safety standards was infrared autofluorescence (IRAF) intensity. No other structural or functional alterations were detected by other imaging techniques for any of the exposures. Photoreceptors and retinal pigment epithelium appeared normal in adaptive optics images. No effect of repeated exposures on TPEF time course was detected, suggesting that visual cycle function was maintained. If IRAF reduction is hazardous, it is the only hurdle to applying two-photon retinal imaging in humans. To date, no harmful effects of IRAF reduction have been detected.

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“…Bleaching, the increase in probe light transmitted through the outer segment when high incident light levels drive a fraction of the photopigment to a nonabsorptive state, is one of the most studied of these phenomena (2). Although bleaching is the most direct result of a light stimulus, scattering (3,4) and refractive index (5) may also change.…”

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confidence: 99%