Absolute retinal blood flowmeter using a laser Doppler velocimeter combined with adaptive optics.

SIGNIFICANCE: The development of a technique allowing for non-invasive measurement of retinal blood flow (RBF) in humans is needed to understand many retinal vascular diseases (pathophysiology) and evaluate treatment with potential improvement of blood flow. AIM: We developed and validated an absolute laser Doppler velocimeter (LDV) based on an adaptive optical fundus camera that provides simultaneously high-definition images of the fundus vessels and absolute maximal red blood cells (RBCs) velocity to calculate the absolute RBF. APPROACH: This new absolute LDV is combined with the adaptive optics (AO) fundus camera (rtx1, Imagine Eyes©, Orsay, France) outside its optical wavefront correction path. A 4-s recording includes 40 images, each synchronized with two Doppler shift power spectra. Image analysis provides a vessel diameter close to the probing beam, and the velocity of the RBCs in the vessels are extracted from the Doppler spectral analysis. A combination of these values gives an average of the absolute RBF. RESULTS: An in vitro experiment consisting of latex microspheres flowing in water through a glass capillary to simulate a blood vessel and in vivo measurements on six healthy humans was done to assess the device. In the in vitro experiment, the calculated flow varied between 1.75 and 25.9 µL / min and was highly correlated (r2 = 0.995) with the flow imposed by a syringe pump. In the in vivo experiment, the error between the flow in the parent vessel and the sum of the flow in the daughter vessels was between -11 % and 36% (mean ± sd, 5.7 ± 18.5 % ). RBF in the main temporal retinal veins of healthy subjects varied between 0.9 and 13.2 µL / min. CONCLUSIONS: The AO LDV prototype allows for the real-time measurement of absolute RBF derived from the retinal vessel diameter and the maximum RBCs velocity in that vessel.

Effect of a New Matrix Therapy Agent in Persistent Epithelial Defects After Bacterial Keratitis Treated With Topical Fortified Antibiotics.

PURPOSE: To evaluate the effect of topical application of a matrix regenerating agent (RGTA) in subjects with a persistent epithelial defect after bacterial keratitis treated with topical fortified antibiotics. METHODS: In this prospective case series of 14 subjects (14 eyes) with a persisting corneal ulcer after the cessation of fortified antibiotics, subjects were treated with an RGTA at a dose of 1 drop every other day. The main outcome measure was the proportion of subjects with complete corneal healing 1 month after initiation of treatment. The secondary outcome measures were the size and depth of corneal ulceration at 1 month, the duration from treatment initiation to complete healing, pain, and tolerability. The ulceration depth was measured with anterior segment optical coherence tomography. RESULTS: Complete corneal healing was observed in 11 (78.6%) of the 14 patients after 1 month and in 14 of the 14 (100%) patients after 3 months. Mean logarithm of the minimum angle of resolution visual acuity improved from 1.22 ± 0.59 at inclusion to 0.57 ± 0.68 at 1 month and to 0.55 ± 0.68 at 3 months (P < 0.01). Pain according to a visual analog scale decreased from 0.34 ± 0.25 to 0.05 ± 0.09 at 1 month and to 0 at 3 months (P < 0.001). Amniotic membrane transplantation was not required for any patients. There were no RGTA-related side effects, and none of the patients reported pain or discomfort during instillation of the drops. CONCLUSIONS: The RGTA seems to be efficient for the treatment of a persistent epithelial defect after bacterial keratitis treated with topical fortified antibiotics.