Abstract
Purpose :
In this work we present a prototype instrument for the recording of double- pass retinal images and associated Point Spread Function (PSF) in human eyes using visible light. The instrument can measure refractive errors and assess intraocular scattering based on through-focus PSF data. While this type of system has been traditionally using infrared light, here our aim was to test the visible-light instrument on healthy volunteers in a laboratory environment and assess the clinical feasibility of the measurements.
Methods :
A prototype benchtop instrument and control software were developed to capture through-focus double-pass PSF in visible light. The instrument consists of two diode laser sources at 520nm and 780nm, a CMOS camera to capture the retinal image, and two tunable lenses for focusing the laser on the retina and the retina on the camera. A spinning mirror was employed to create a circular pattern on the retina to eliminate speckle and retinal non-uniformities. Two apertures located at pupil conjugate planes were used to regulate the light entering the pupil and reaching the camera. The measurement at 520nm, consisted of a sequence of 10 retinal captures with a step of 0.1D and lasted 0.2 seconds allowing us to measure non-dilated volunteers. Light levels were kept below 12μW for both wavelengths, more than an order of magnitude below the maximum permissible exposure.
Results :
The instrument was successfully used to measure non-dilated healthy emmetropic volunteers. The refractive error was assessed using visible light and matches the measurement obtained with infrared light once considered chromatic focus differences. The use of visible light allows the instrument to assess the true PSF of individuals with diffractive multifocal IOLs, which cannot be accurately measured with infrared light due to their diffractive properties.
Conclusions :
A prototype benchtop double-pass instrument utilizing visible light for optical quality assessment was evaluated on a healthy volunteer in a laboratory setting. The instrument holds the potential to become a valuable clinical tool for evaluating the optical performance of cataract patients before and after surgery, including those with premium IOLs that cannot be accurately assessed with current commercial instruments. The accurate assessment of the optical quality of pseudophakic patients can help surgeons identify and correct residual refractive errors or secondary cataracts.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.