OPHTHALMOLOGICA

Retinal blood flow evaluation

There are now several non-invasive technologies available which can measure the response of retinal blood flow to physiological and pharmacological stimuli. That may in turn elucidate the role of altered retinal blood flow and its regulation in the pathogenesis of retinal diseases of vascular origin. The technologies include the new retinal vein analyzer and bidirectional laser Doppler velocimetry to measure retinal blood flow and blood vessel diameter in the main retinal vessels. The addition of a scanner in such a setup enables the creation of a map of the retinal microcirculation. Other techniques include laser Doppler flowmetry and laser speckle flowgraphy, which measure the velocities of blood in discrete areas of the retinal tissue microcirculation. The blue-field simulation technique allows the quantification of the velocity, number and velocity pulsatility of leukocytes moving in the retinal capillaries of the macular region. Colour Doppler imaging enables measurement of the peak systolic and end-diastolic values of blood velocity in the ophthalmic and central retinal artery, from which a resistivity index is obtained.

(Pournaras et al, Ophthalmologica 2012 DOI:10.1159/000338186)

Micronutrients in AMD

There is a range of micronutrients that may be of value in treating or preventing AMD, according to a survey of the peer-reviewed literature on the topic. The micronutrients include vitamin C, β-carotene, vitamin E and zinc, the carotenoids, lutein and zeaxanthin and the omega-3 fatty acids. Theories regarding the mode of action of the micronutrients include an improved filtration of short wavelength light and a reduction in oxidative and inflammatory damage, in addition to other structural and physiological factors.

(Aslam et al, Ophthalmologica 2013 DOI:10.1159/000343708.)

Spectral domain OCT segmentation software

In eyes with exudative AMD, the Spectralis optical coherence tomography (OCT) segmentation software provides a reliable representation of the inner limiting membrane, but is unreliable in its representation of the Bruch’s membrane, according to findings of a retrospective study. The study’s investigators reviewed 114 scans of 38 eyes of 38 newly diagnosed exudative AMD patients. The Spectralis OCT segmentation software drew inner limiting membrane correctly in all 114 spectral domain OCT scans, but drew the Bruch’s membrane correctly in only 59 scans (51.8 per cent). The software was significantly less reliable in locating Bruch’s membrane in cases with pigment epithelium detachment (PED), where it only drew the membrane correctly in 42.5 per cent of eyes, compared to 73.5 per cent of eyes without PED (p = 0.049).

(Tilleul et al, Ophthalmologica 2013; DOI:10.1159/000342980.)