Optical bench simulation for intraocular lenses using field-tracing technology

Purpose To evaluate the image quality of intraocular lenses (IOLs) using field-tracing optical simulation and then compare it with the image quality using conventional ray-tracing simulation. Methods We simulated aspheric IOLs with a decenter, tilt, and no misalignment using an aspheric corneal eye model with a positive spherical aberration. The retinal image, Strehl ratio, and modulation transfer function (MTF) were compared between the ray-tracing and field-tracing optical simulation and confirmed by the results reported in an in vitro experiment using the same eye model. Results The retinal image showed interference fringes from target due to diffraction from the object in a field-tracing simulation. When compared with the experimental results, the field tracing represented the experimental results more precisely than ray tracing after passing over 400 μm of the decentration and 4 degrees of the tilt of the IOLs. The MTF values showed similar results for the case of no IOL misalignment in both the field tracing and ray tracing. In the case of the 200-μm decentration or 8-degree tilt of IOL, the field-traced MTF shows lower values than the ray-traced one. Conclusions The field-tracing optical bench simulation is a reliable method to evaluate IOL performance according to the IOL misalignment. It can provide retinal image quality close to real by taking into account the wave nature of light, interference and diffraction to explain to patients having the IOL misalignment.

Development of a novel multifocal lens using a polarization directed flat lens: possible candidate for a multifocal intraocular lens

Background A polarization-directed flat (PDF) lens acts as a converging lens with a focal length (f) > 0 and a diverging lens with f < 0, depending on the polarization state of the incidental light. To produce a multifocal lens with two focal lengths, a PDF and a converging lens having shorter focal length were combined. In this study, we tested a bifocal PDF to determine its potential as a new multifocal intraocular lens (IOL). Methods Constructed a multifocal lens with a PDF lens (f = +/− 100 mm) and a converging lens (f = + 25 mm). In an optical bench test, we measured the defocus curve to test the multifocal function. The multifocal function and optical quality of the lens in various situations were tested. An Early Treatment Diabetic Retinopathy Study (ETDRS) chart as a near target and a building as a distant target were photographed using a digital single-lens reflex (DSLR) camera. Both lenses (multifocal and monofocal) were tested under the same conditions. Results For the 0 D and − 20 D focal points, the multifocal lens showed sharp images in the optical bench test. In the DSLR test using the multifocal lens, the building appeared slightly blurry compared with the results using the monofocal lens. With the multifocal lens, the ETDRS chart’s images became blurry as the ETDRS chart’s distance decreased, but became very clear again at a certain position. Conclusions We confirmed the multifocal function of the multifocal lens using a PDF lens. This lens can be used as a multifocal IOL in the future.

Blue–Yellow VEP with Projector-Stimulation in Glaucoma

Background and aim In the past, increased latencies of the blue-on-yellow pattern visually evoked potentials (BY-VEP), which predominantly originate in the koniocellular pathway, have proven to be a sensitive biomarker for early glaucoma. However, a complex experimental setup based on an optical bench was necessary to obtain these measurements because computer screens lack sufficient temporal, spatial, spectral, and luminance resolution. Here, we evaluated the diagnostic value of a novel setup based on a commercially available video projector. Methods BY-VEPs were recorded in 126 participants (42 healthy control participants, 12 patients with ocular hypertension, 17 with “preperimetric” glaucoma, and 55 with perimetric glaucoma). Stimuli were created with a video projector (DLP technology) by rear projection of a blue checkerboard pattern (460 nm) for 200 ms (onset) superimposed on a bright yellow background (574 nm), followed by an offset interval where only the background was active. Thus, predominantly S-cones were stimulated while L- and M-cone responses were suppressed by light adaptation. Times of stimulus onset to VEP onset-trough (N-peak time) and offset-peak (P-peak time) were analyzed after age-correction based on linear regression in the normal participants. Results The resulting BY-VEPs were quite similar to those obtained in the past with the optical bench: pattern-onset generated a negative deflection of the VEP, whereas the offset-response was dominated by a positive component. N-peak times were significantly increased in glaucoma patients (preperimetric 136.1 ± 10 ms, p < 0.05; perimetric 153.1 ± 17.8 ms, p < 0.001) compared with normal participants (123.6 ± 7.7 ms). Furthermore, they were significantly correlated with disease severity as determined by visual field losses retinal nerve fiber thinning (Spearman R = –0.7, p < 0.001). Conclusions Video projectors can be used to create optical stimuli with high temporal and spatial resolution, thus potentially enabling sophisticated electrophysiological measurements in clinical practice. BY-VEPs based on such a projector had a high diagnostic value for detection of early glaucoma. Registration of study Registration site: www.clinicaltrials.gov Trial registration number: NCT00494923.

Optical Bench Analysis of 2 Depth of Focus Intraocular Lenses

<b><i>Background:</i></b> The aim of the study was to analyze the objective optical properties of 2 enhanced depth of focus (EDoF) intraocular lenses (IOLs) using optical bench analysis. <b><i>Methods:</i></b> This experimental study investigates 2 new EDoF IOLs, the Alcon AcrySof IQ Vivity and the Bausch &amp; Lomb LuxSmart Crystal, on the optical bench, using OptiSpheric IOL PRO2 (Trioptics, Germany) in order to assess the optical quality according to ISO 11979 with ISO-2 Cornea. IOLs (power 22.0 D) were evaluated regarding modulation transfer function (MTF) at 50 lp/mm and Strehl ratio (SR) using a 3.0-mm and a 4.5-mm aperture. In addition, wavefront measurements were obtained using WaveMaster® IOL 2 device (Trioptics, Germany), and USAF targets were analyzed. <b><i>Results:</i></b> Centered: the MTF (mean) at 50 lp/mm (AcrySof IQ Vivity/LuxSmart Crystal) with 3.0 mm aperture was 0.250/0.257 and with 4.5 mm aperture 0.202/0.243. The SR (mean) with 3.0 mm aperture was 0.261/0.355 and with 4.5 mm aperture 0.176/0.206. Decentered by 1 mm: the MTF (mean) at 50 lp/mm (AcrySof IQ Vivity/LuxSmart Crystal) with 3.0 mm aperture was 0.266/0.247 and with 4.5 mm aperture 0.126/0.215. The SR (mean) with 3.0 mm aperture was 0.272/0.234 and with 4.5 mm aperture 0.133/0.183. Tilted by 5 degree: the MTF (mean) at 50 lp/mm (AcrySof IQ Vivity/LuxSmart Crystal) with 3.0 mm aperture was 0.221/0.360 and with 4.5 mm aperture 0.214/0.229. The SR (mean) with 3.0 mm aperture was 0.232/0.428 and with 4.5 mm aperture 0.225/0.229. The simulated visual function using USAF test targets showed corresponding qualitative results. Wavefront measurements proved a complex optical design. Higher order aberrations in the central part of the optics were modulated up to the 10th order to enhance the range of functional vision to near distance, leaving the peripheral parts of the optics aberration free or as aberration correcting. <b><i>Conclusion:</i></b> The diversity of EDOF IOLs, their optics, and their respective impact on the vision quality must be understood in order to select the appropriate IOL in each individual case. This analysis of new, innovative IOL optics based on increased negative spherical aberration may help the ophthalmic surgeon to select the IOL which meets the individual requirements of the patient for best postoperative outcomes. It seems that there is no perfect IOL that is equally suitable for all patients, but the right choice is an individual, customized approach dealing with patients’ expectations.

Development of a novel multifocal lens using a polarization directed flat lens: Possible candidate for a multifocal intraocular lens

Background: A polarization-directed flat (PDF) lens acts as a converging lens with a focal length (f) > 0 and a diverging lens with f < 0, depending on the polarization state of the incidental light. To produce a multifocal lens with two focal lengths, a PDF and a converging lens having shorter focal length were combined. In this study, we tested to determine its potential as a new multifocal intraocular lens (IOL).Methods: Constructed a multifocal lens with a PDF lens (f=+/- 100 mm) and a converging lens (f= +50 mm). In an optical bench test, we measured the lens’s focal lengths to test the multifocal function. The multifocal function and optical quality of the lens in various situations were tested. An Early Treatment Diabetic Retinopathy Study (ETDRS) chart as a near target and a parking lot as a distant target were photographed using a digital single-lens reflex (DSLR) camera. Both lenses (multifocal and monofocal) were tested under same conditions. Results: In the optical bench test, the multifocal lens’s focal lengths were 31.2 and 71.2 mm. In the DSLR test using the multifocal lens, the parking lot appeared slightly cloudy compared to the monofocal lens results. With the multifocal lens, the ETDRS chart’s images became blurry as the ETDRS chart’s distance decreased, but became very clear again at a certain position.Conclusions: We confirmed the multifocal function of the multifocal lens using a PDF lens. This lens can be used as a multifocal IOL in the future.