Many of us have experienced being in the market for a new car and have gone through the decision-making process. This journey may have started when we viewed some slick advertisements in a magazine or were attracted to an alluring clip online. After researching the options, we made a tentative decision. With eager anticipation, we hurried down to the dealership to test-drive our selected model, only to be disappointed. The ergonomics of the driver’s seat and console did not suit our body, the handling of the car was sluggish, the color in natural light was not as portrayed in the ad, and there were numerous blind spots as we traversed the road. This brief, but valuable real-world experience eclipsed the preconceived notions that were the basis of our initial evaluation. Moreover, the test-drive empowered us to walk away and try another car more suitable to our needs.

Is it possible for our cataract or clear lens exchange patients to “test-drive” their presbyopia-correcting intraocular lenses (IOLs) preoperatively and to view real-world scenes and images at different distances and under different lighting and glare sources with good fidelity to their postoperative outcomes? Can they experience the photic phenomena associated with specific IOL designs and evaluate image contrast? What if they could efficiently evaluate varying degrees of monovision and determine the laterality and strength of their ocular preference? Would this be a better and more realistic way for patients to evaluate IOL options than the current paradigm of viewing printed or digital images of halos around car headlights at night, answering written questions regarding imagined preferences and tolerances, or reviewing the results of phase 3 trials with narrow inclusion criteria that may not reflect their individual ocular characteristics or adaptive abilities?

SimVis Gekko Binocular Visual Simulator

The SimVis Gekko visual simulator (2Eyes Vision) is a wearable, wireless, programmable, see-through binocular device (Figure 1) with a widefield view that allows for simulation of IOLs through the subject’s own optical system.¹ It uses optotunable lenses working in a temporal multiplexing mode to provide multiple images superimposed on the retina, all with the same position and magnification but corresponding to different planes in focus.² These custom, electronically driven lenses can produce fast periodic foci variations at speeds greater than the flicker fusion threshold of the human visual system (50 Hz), thereby delivering seemingly static images on the subject’s retina that emulate the effect of multifocal correction.

The simulation of extended depth of focus (EDOF) or multifocal corrections relies on evaluating the through-focus energy distribution of the correction from the spatially varying pupillary power distribution of the IOL and programming the optotunable lens to the corresponding time-varying focus changes. By modifying the temporal pattern driving the tunable lens, it is possible to tailor the through-focus performance of specific commonly used multifocal (diffractive and refractive) and EDOF IOLs. A comparative advantage of the temporal multiplexing principle employed in SimVis Gekko is that it allows for projecting the multifocal profile onto the retina, avoiding selective spatial occlusions that will occur in a spatial representation of the lens in other simulator modalities (eg, using a spatial light modulator) in patients with cataracts.² This binocular, visual simulator can also simulate other binocular presbyopic corrections, including monovision and modified monovision.

Evolution to Advanced Alignment and Eye Tracking 

Recently, the SimVis Gekko has evolved to incorporate a cutting-edge alignment method and an advanced eye tracking system. This enhancement ensures precise alignment of the visual simulation with the patient’s gaze, improving the accuracy of the simulated visual experience. The eye-tracking system monitors the patient’s eye movements in real time, allowing for dynamic adjustments.

Fidelity of the Visual Simulator in Predicting Postoperative Vision and Photic Phenomena

The utility of a visual simulator depends on its accuracy in predicting postoperative vision at multiple distances, as well as simulating photic phenomena that may be inherent to specific commonly used IOL designs. Numerous studies have demonstrated the fidelity of the SimVis Gekko in reproducing postoperative vision with real IOLs, even in patients with moderate cataracts, demonstrating strong correlations between the patients’ preoperative and postoperative SimVis assessments (Figure 2).^3-5 The same patient can efficiently and effectively experience different IOL combinations preoperatively. Perceptual scores vary for different IOL combinations and are repeatable for a given subject.⁶ Patients maintain the same binocular IOL preference rankings preoperatively and postoperatively, both for patients with cataract and for those undergoing clear lens exchange.³

It is well established that performance in many real-world situations (such as night driving) is not well correlated with high contrast vision testing, as is commonly employed in the clinic. A new metric, the Multifocal Acceptance Score (MAS-2EV), is a useful tool derived from responses using the SimVis Gekko system to more realistically evaluate vision with presbyopic corrections and to rank and order binocular IOL preferences, with high repeatability and sensitivity.⁷ The MAS-2EV is based on a set of images representing natural visual scenes in day and night conditions projected on far and near displays, as well as a near stereo target.

In addition to high-contrast optotypes, the SimVis Gekko allows for the viewing of natural images (including low, medium, and high spatial frequencies) under different luminances, as well as sources of mesopic glare (eg, LED lights embedded in an image of a car’s headlights). A recent study by Papadogiannis and colleagues⁸ (Figure 3) showed that the size of the glare image perceived through the SimVis Gekko Visual Simulator with each of the presbyopic IOL corrections was highly correlated (r_s>.97) with the reported symptoms using the validated Assessment of IntraOcular Lens Implant Symptoms questionnaire,⁹ and that larger glare diameters (which disturbed the patients more) correlated with higher near adds.

In a recent prospective study of 326 subjects tested for ocular dominance using the binary, commonly used “hole-in-the-card” sighting test when compared to the eye dominance strength (EDS) and laterality using the SimVis Gekko, the sighting test did not match the SimVis sensory test results 41% of the time.¹⁰ The “hole-in-the-card” sighting test relies on a neural motor muscle action of holding the card, biasing the test with the subjects’ motor habits and gaze angle. In contrast, widefield binocular vision is entirely a sensory activity independent of motor muscle activity. The SimVis relies entirely on neural sensory image testing, thereby eliminating the neural motor bias. Prospective studies are under way to determine the prognostic significance of eye dominance strength and satisfaction with monovision correction using the EDS metric vs sighting testing with the “hole-in-the-card” method. The SimVis Gekko allows rapid evaluation of full and partial monovision in a masked fashion allowing the patient to visualize natural images and optotype at both distance and near. In addition, because the correction is applied on a plane conjugate with the pupil of the eye, it obviates issues of interocular differences in magnification or prismatic effects associated with loose lenses.¹¹ The SimVis methodology could be similarly applied to determine optimal adjustments for light-adjustable IOLs set for different degrees or laterality of monovision.

The same advantages of SimVis Gekko in evaluating presbyopia-correcting IOLs can also be applied to rapidly evaluate simulations of various multifocal contact lens designs^12,13 and to compare them to contact lenses set for varying degrees of monovision, testing the patient at near, intermediate, and far. 

Conclusions

The IOL selection process may at times be overwhelming for both the patient and the eyecare professional in light of the growing list of presbyopic simultaneous vision options (eg, trifocal and EDOF IOLs), as well as the varying degrees of monovision with monofocal or light-adjustable IOLs. An important, useful addition to preoperative cataract and clear lens exchange assessment is the ability to prospectively simulate specific pseudophakic options in a masked fashion for patients, using a binocular, wearable, portable, see-through, wide field of view, programmable vision simulator that shows excellent fidelity to postoperative perceptual scores and reproducible preoperative and postoperative binocular IOL rankings. The SimVis Gekko system is designed to empower patients (and their providers) with the ability to visually test-drive various commonly used monofocal and premium IOL options—diffractive, EDOF, and monovision—before committing to their final surgical decision with their doctor to enhance the likelihood of a satisfied outcome. The SimVis Gekko helps put the patient in the “visual driver’s seat” preoperatively, helping to improve patient visual satisfaction postoperatively.  

Jay S. Pepose, MD, PhD, is a specialist in refractive surgery and in corneal and external diseases. He is the founder and medical director of the Pepose Vision Institute and a professor of clinical ophthalmology and visual sciences at Washington University School of Medicine in St. Louis, MO.

Scott M. MacRae, MD, is a professor of ophthalmology at the University of Rochester Flaum Eye Institute. He specializes in cataract and refractive surgery and has served on the FDA Ophthalmic Devices Panel. He has been Senior Associate Editor of the Journal of Refractive Surgery and served on other editorial boards, and has a special interest in presbyopic correction.

References

1. Dorronsoro C, Radhakrishnan A, Alonso-Sanz JR, et al. Portable simultaneous vision device to simulate multifocal corrections. Optica. 2016;3(8):918-924.

2. Akondi V, Sawides L, Marrakchi Y, Gambra E, Marcos S, Dorronsoro C. Experimental validations of a tunable-lens-based visual demonstrator of multifocal corrections. Biomed Opt Express. 2018;9(12):6302-6317.

3. Barcala X, Zaytouny A, Rego-Lorca D, et al. Visual simulations of presbyopic corrections through cataract opacification. J Cataract Refract Surg. 2023;49(1):34-43.

4. Vinas M, Aissati S, Romero M,  et al. Pre-operative simulation of post-operative multifocal vision. Biomed Opt Express. 2019;10(11):5801-5817.

5. Zaytouny A, Sisó-Fuertes I, Barcala X, Sawides L, Dorronsoro C, Marcos S. Clinical validation of simulated multifocal intraocular lenses with SimVis GekkoTM simulations and reports on pseudophakic patients. Abstract presented at: Annual meeting of the Association for Research in Vision and Ophthalmology; April 23-27, 2023; New Orleans, LA. 

6. Radhakrishnan A, Pascual D, Marcos S, Dorronsoro C. Vision with different presbyopia corrections simulated with a portable binocular visual simulator. PLoS ONE. 2019;14(8):e0221144.

7. Barcala X, Vinas M, Romero M, et al. Multifocal acceptance score to evaluate vision: MAS-2EV. Sci Rep. 2021;11(1):1397.

8. Papadogiannis P, Rodriguez-Lopez V, de Castro A, et al. Preoperative simulation of glare with a multifocal Intraocular lenses using a binocular visual simulator. Poster presented at: Annual meeting of the European Society of Cataract and Refractive Surgeons; September 6-10, 2024; Barcelona, Spain.

9. Masket S, Lum F, MacRae S, et al. Symptoms and satisfaction levels associated with intraocular lens implants in the monofocal and premium IOL patient-reported outcome measure study. Ophthalmology. 2023;130(7):726-734.

10. Pepose JS. Monovision: Still a quality option, but which eye dominates? Presented at Hawaiian Eye and Retina Meeting; January 13-19, 2024, Maui, Hawaii.

11. Rodriguez-Lopez V, Barcala X, Zaytouny A, Dorronsoro C, Peli E, Marcos S. Monovision correction preference and eye dominance measurements. Transl Vis Sci Technol. 2023;12(3):18. 

12. Barcala X, Vinas M, Ruiz S, et al. Multifocal contact lens vision simulated with a clinical binocular simulator. Cont Lens Anterior Eye. 2022;45(6):101716.

13. Esteban-Ibañez E, Montagud-Martínez D, Sawides L, et al. Simulation of daily soft multifocal contact lenses using SimVis Gekko: from in-vitro and computational characterization to clinical validation. Sci Rep. 2024;14(1):8592.

Disclosures

Dr. Pepose is an equity owner in 2EyesVision.

Dr. MacRae is a consultant to 2EyesVision.