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Scanning Light Scattering Profiler (SLSP) Method for Quantitative Evaluation of Light Scattering in Intraocular Lens Implants

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This regulatory science tool (RST) is a scanning light scattering profiler (SLSP) method for quantitative evaluation and nonclinical measurement of light scattering characteristics of both current and new-technology intraocular lens (NTIOL) implants.

Technical Description

The SLSP test method is based on a comprehensive, full-angle quantitative evaluation of both forward and backward light scatter from intraocular lens (IOL) implants [1-4]. The SLSP uses a goniometric 360°-angle scanning design for measuring the IOL angular light scattering properties under simulated in-situ conditions. The SLSP tool has a wide range of applications for quantitative nonclinical evaluation of light scatter that contributes to clinically relevant phenomena including unintended vacuoles, glare, optical defects, poor image quality, and other IOL light scattering effects [5,6]. The SLSP test capabilities have been implemented in studying light scattering characteristics of a variety of IOL designs including monofocal, multifocal, and extended depth of focus (EDF) IOLs. The SLSP tool approximates in-situ conditions by adjusting the parameters of the light source, including the angle of incidence. To measure IOL light scattering characteristics and assess its test potential, the SLSP tool incorporates analytical modeling and alternative comparison test approaches based on digital microscopy. For example, statistically significant correlation was found among the SLSP results, analytical modeling, and comparison tests in evaluating unwanted light scatter caused by IOL microvacuoles [3,4]. In quantitative evaluation of IOL light scattering, the SLSP tool provides the following features:

  • Full-angle quantitative evaluation of total forward and backward IOL light scatter.
  • Demonstrated applicability for evaluating IOL light scattering associated with key light scatter phenomena across various current and NTIOL designs, as reported in [1-4].
  • Measures IOL light scattering characteristics under dry and in-situ conditions.
  • Performance compatible with analytical modeling and alternative test approaches for measurement of IOL light scattering characteristics.

Intended Purpose 

The intended purpose of the SLSP method is to provide quantitative objective evaluation and nonclinical measurement of light scattering characteristics of both current and NTIOL implants.

Testing

To evaluate and validate the critical properties of the SLSP tool, we performed multiple tests included in the following peer-reviewed studies:

  • SLSP tool characteristics [1-2]: These studies provided experimental evaluation of the SLSP measured dependences between the forward and backward light scattering intensities and rotational angles (or scattering profiles). The SLSP tool characteristics tested include angle of incidence and test beam diameter, and they were tested using monofocal, multimode, EDF, and graded IOL samples.
  • Light scatter from IOL vacuoles [3-4]: These studies compared experimental SLSP tool results with a ray-tracing analytical model to quantitatively evaluate and correlate the light scattering characteristics of IOL vacuoles under simulated in-situ conditions using various vacuole-graded IOL samples.
  • Quantitative evaluation and characterization of IOL light scatter [3-4]: The studies compared SLSP measured-IOL light scattering characteristics with those obtained through an alternative test approach based on high-magnification digital microscopy.
  • Correlating multiparameter IOL light scatter characteristics [2-4]: These studies used SLSP data, including results from analytical modeling and digital microscopy, to correlate multiparameter IOL light scattering characteristics, enabling highly accurate quantitative evaluation and nonclinical measurement of the IOL light scatter.

Limitations

The current SLSP setup does not replicate in-vivo ocular conditions, as the temperature and surrounding media differ from those of the eye. Incorporating a temperature-controlled saline bath is one approach that may more closely approximate physiological conditions. Another limitation is the challenge of removing ballistic photons from the measured scatter [5], which can improve measurement accuracy and reduce the influence of IOL dioptric power on measured scatter. Additionally, the SLSP setup currently uses a primary laser wavelength of 546 ± 10 nm consistent with ISO 11979-2:2024 [7]. However, light scattering measurements typically include laser sources with various wavelengths across the 400-780 nm visible spectral range.

Supporting Documentation

  1. B. Walker, R. James, D. Calogero, and I. Ilev, “A novel full-angle scanning light scattering profiler (SLSP) to quantitatively evaluate forward and backward light scattering from intraocular lenses”, Review of Scientific Instruments, v. 86, pp. 095004, 2015. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10961904/ 
  2. B. Walker, R. James, D. Calogero, and I. Ilev, “Scanning light scattering profiler (SLSP) based methodology to quantitatively evaluate forward and backward light scattering from intraocular lenses”, Journal of Visualized Experiments, v. 124, pp. e55421, 2017. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5608261/ 
  3. V. Spiezio, B. Walker, D. Calogero, and I. Ilev, “Quantitative evaluation of light scattering glistenings in intraocular lenses employing a high-magnification digital microscopy method”, Journal of Ophthalmology, v. 2019, pp. 7929014, 2019. https://www.hindawi.com/journals/joph/2019/7929014/ 
  4. V. Spiezio, B. Walker, D. Calogero, and I. Ilev, “Experimental and analytical quantification of light scattering from vacuoles in intraocular lenses”, Journal of Cataract and Refractive Surgery, v. 46, pp. 762-773, 2020. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10824253/pdf/nihms-1958417.pdf
  5. D. Kim, R. James, R. Landry, D. Calogero, J. Anderson, and I. Ilev, “Quantification of glistenings in intraocular lenses using a ballistic-photon removing integrating-sphere method”, Applied Optics, v. 50, pp. 6461-7, 2011. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10961905/ 
  6. R. Landry, I. Ilev, J. Pfefer, M. Wolffe, and J. Alpar, “Characterizing reflections from intraocular lens implants”, Eye, v. 21, pp. 1083-1086, 2007. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11384229/ 
  7. International Organization for Standardization. Ophthalmic implants – Intraocular lenses – Part 2: Optical Properties and Test Methods. Geneva, Switzerland, ISO, 2024 (ISO 11979-2:2024)

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