This article is more than 5 years old. Information may no longer be current.
Handheld adaptive optics SLO images cones closest to the fovea
Click Here to Manage Email Alerts
A portable handheld adaptive optics scanning laser ophthalmoscope enables cellular level imaging near the fovea of the retina, according to researchers who engineered and tested the device in a human trial.
Researchers imaged the retina of seven healthy, undilated adult volunteers, five healthy, dilated adult volunteers and two young children under anesthesia.
Before each human imaging session, the linear polarizer was rotated to maximize throughput in the illumination channel, and the quarter wave plate was rotated to minimize the lens reflection, researchers wrote. The optical power incident on the subject cornea was 0.54 mW or less and within the most conservative limits of the ANSI Z136.1 standard for the 774 ± 5 nm source used.
All subjects were imaged with the maximum field-of-view from the handheld adaptive optics scanning laser ophthalmoscope (HAOSLO), which was 1.4° x 4.0°, at a frame rate of 6.8 Hz and image dimensions of 250 x 1464 pixels.
Researchers measured convergence time of three wavefront sensor-less adaptive optics (WS-AO) algorithms. Then, the overall aberration correction ability of the three algorithms was tested.
In the first set of human experiments, researchers used the HAOSLO probe in handheld mode to image seven healthy, nondilated adults positioned semi-reclined on a tilted chair.
They also imaged five pharmacologically dilated, supine adults to establish the practicality of using the probe to image a subject who cannot sit upright.
The researchers’ novel stochastic Zernike gradient descent (SZGD) algorithm achieved the same correction quality as stochastic parallel gradient descent (SPGD) but in about one-sixth of the time, based on their WS-AO speed comparisons.
The defocus-only correction converged quickly but had a maximum mean intensity less than half that of the other two algorithms, according to the study.
Further, “the SPGD and SZGD algorithms both reached the same maximum mean intensity, but SZGD converged 5.9 times faster, which supports claims from prior studies on the superior convergence times of model-based optimization strategies,” researchers wrote.
SZGD provided nearly identical qualitative image correction to SPGD and corrected more than just defocus, they continued.
The HAOSLO provides reliable imaging of the cones closest to the fovea, according to researchers.
The device also many be useful in a range of other applications for optical engineers, vision scientists and clinicians studying ophthalmic disorders in adults and children.
They also demonstrated imaging of the cone photoreceptors in dilated supine young children and adult subjects.
To facilitate reproducibility of the research, the optical and mechanical designs, computational algorithms and control software for the HAOSLO system is freely available online at: people.duke.edu/~sf59/HAOSLO.htm. – by Abigail Sutton
Disclosures: DuBose is employed by Duke University. Please see the full study for remaining authors’ financial disclosures
Click Here to Manage Email Alerts