Name: scanning light scattering profiler (slps) based methodology to quantitatively evaluate forward and backward light scattering from intraocular lenses
Uploaded: 2017-06-06T15:30:00
Description: Watch this Scientific Journal Video about Scanning Light Scattering Profiler SLPS Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses at JoVE.com

The authors would like to thank the companies for the access of their monofocal and multifocal IOLs. This work was supported by Oak Ridge Institute for Science and Education (ORISE) and the Medical Device Fellowship Program (MDFP) and their contributions are appreciated. In addition, the authors would like to thank Samuel Song for his contributions in the laboratory.

1. SLSP Measurement Platform Preparation
NOTE: All alignment steps require precision and patience to ensure accurate quantitation when measuring light scatter. An overview of the SLSP setup in provided within Figure 1. Here, an illustration (Figure 1a) shows the basic concept of the SLSP setup. In addition, Figures 1b and 1c help define the various angles referenced within the discussion. Specifically, the following three angles...

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The results from the SLSP platform experiments have found that using simple goniophotometry principles can lead to a powerful tool for evaluating the properties of light scatter associated with unique IOL designs and materials. Specifically, the SLSP platform has observed a direct correlation between the amount of detectable scattered light and the beam diameter of the light source. In addition, the multiple scattered peaks found in multifocal IOLs were easily observed with the SLSP. Furthermore, as the source of light a...

The scanning light scattering profiler (SLSP) approach was first introduced to address the need to quantitatively evaluate light scattering characteristics of intraocular lenses (IOLs) in a non-clinical setting1. Developing a test methodology to evaluate the light scattering tendencies of IOL designs and materials is of significant interest in order to help identify potential unwanted light scattering problems. Light scatter is commonly reported by patients and observed as glare, glistening, optical imperfections, and other forms of dysphotopsia2, sometimes leading to a patient requesting the IOL explantation. In addition to dysphotopsia, scattered light reduces the amount of ballistic light, resulting in lower overall image quality3. Developing a device that can non-clinically evaluate the IOL potential to scatter the incoming light (and later correlated with clinically reported outcomes) can be useful.
Evaluating optical properties of IOLs (the lens used to replace the human crystalline lens after cataract surgery) is of particular interest as it is the most commonly implanted medical device in the world (almost 20 million per year)4 and the United States (over 3 million per year)5. As a result, even a small percentage of patients reporting dysphotopsia may have a large impact. In addition, rapidly improving technologies (e.g. new IOL designs, materials, and optical capabilities) have the potential to increase concerns related to light scattering. For example, multifocal IOLs have been designed to improve near and far visual acuity by designing lenses that utilize refraction and diffraction optical principles. Although highly successful, these lenses have also been found to increase the amount of reported halos and glare, largely associated with scattering of light6.
A few non-clinical laboratory studies attempt to predict dysphotopsia from scattered light as it passes through IOLs7. For example, research has identified that IOL haptics (the arms of the IOL used to set it in place) and the edge of the IOLs are prone to induce a large amount of the observed glare scattered light8. One method, a ballistic-photon removing integrating-sphere method (BRIM), was introduced to quantitatively measure the amount of total non-ballistic light after passing through an IOL9. However, this highly sensitive technique is designed to measure the total intensity of scattered light and is unable to identify directionality of the scattered light. Computer simulation software can be used with model eyes to help predict intensity and directionality of light scatter from various IOL designs and materials. For example, the propensity for the IOL edge to induce the light scattering was simulated to identify designs that would limit the amount of scattered light10. Furthermore, computer simulations that incorporated the Mie scattering theory verified that increased light scatter can reduce the modulation transfer function (MTF) of the IOL (a direct correlation to image quality)3. Although helpful, real bench tests would be necessary to verify these predictive simulations.
To verify predictive simulations a bench test is necessary that is capable of detecting and quantitatively evaluating two distinct forms of scattered light, forward scattered and backward scattered light. Although not a source of dysphotopsia, backward scattered light (light scattering away from the eye) is a cause for reduced image quality, as less light passes through the IOL to ultimately reach the retina. Forward scattered light (light scattering towards the retina) is a concern for ophthalmologists as it may result in complaints of dysphotopsia (e.g. glare, halo, and glistening). One common example is patients reporting additional unwanted glare from passing oncoming cars during night driving; this issue is particularly common with multifocal IOLs11. However, current practice to identify potential forward scattered light is for ophthalmologists to shine light onto the patient&#39;s eye and qualitatively observe how much light is reflected back (backward scattered light) and assuming that the backward scattered light will be approximately the same as the forward scattered light (which is not always the case)12.
Here, we describe a simple test methodology using goniophotometry principles to quantitatively measure the magnitude and direction of scattered light at it passes through an intraocular lens. The SLSP operates by rotating a photodiode sensor 360 degrees around an IOL that is exposed to a light source, see Figure 1a. We chose a green laser source (543 nm) to best represent the known photopic maximum and to agree with the international standard specifications13. Here, an IOL is adapted onto a rotational and translational holder where a photodiode sensor can circle around and observe light scattering off of the lens. As a result, the SLSP has the unique capability to quantitatively measurement the magnitude and directionality of scattered light. However, although not described here, for better predictive capabilities, experiments should be conducted within a controlled environment using an appropriate eye model. The distance between the IOL and the optical sensor (as well as the size of the sensor element) will determine the resolution capabilities of the device; however, there will be a tradeoff between resolution and signal strength that will need to be adjusted, as needed.
To accurately describe the principles of the SLSP platform we define three types of rotational angles, see Figures 1b and 1c. Specifically, the rotation angle (&#730;R) represents the rotation of a photodiode sensor as it rotates around an IOL. Here, 0&#730;R would represent when the sensor is behind the lens (backward scattered light) and 180&#730;R represents when the sensor is in front of the lens (forward scattered light). Angles of 90&#730; and 270&#730; represent the transition points between forward and backward scattered light. The sensing angle (&#730;S) represents degrees that the sensor is pivoted (in the up and down direction) so that it can detect more than one plane of scattered light. Here, 0&#730;S means the sensor surface is parallel to the IOL (and light source). Finally, the angle of incidence (&#730;I) represents the angle that the light source is approaching the IOL from. Here, 0&#730;I corresponds to when the incident light is on the optical axis of the IOL and 90&#730; would represent when the light source is perpendicular to the Meridional plane.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>PD300 series Photodiode Sensor</td>
			<td>Ophir-Spiricon Corp</td>
			<td>7Z02410</td>
			<td>PD300-1W, RoHS</td>
		</tr>
		<tr>
			<td>URS Series Precision Rotation Stage</td>
			<td>Newport Corp.</td>
			<td>URS75BCC</td>
			<td></td>
		</tr>
		<tr>
			<td>ESP301 1-Axis Motion Controller and Driver</td>
			<td>Newport Corp.</td>
			<td>ESP301-1N</td>
			<td></td>
		</tr>
		<tr>
			<td>LabView Software</td>
			<td>National Instruments Corp.</td>
			<td>776671-35</td>
			<td></td>
		</tr>
		<tr>
			<td>Origin</td>
			<td>OriginLab Corp.</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Single Mode FC/APC Fiber Optic Patch Cables</td>
			<td>ThorLabs Inc.</td>
			<td>P3-460B-FC</td>
			<td></td>
		</tr>
		<tr>
			<td>10X Olympus Plan Achromat Objective</td>
			<td>ThorLabs Inc.</td>
			<td>RMS10X</td>
			<td>RMS10X - 10X Olympus Plan Achromat Objective, 0.25 NA, 10.6 mm WD&#160;</td>
		</tr>
	</tbody>
</table>

scanning light scattering profiler (slps) based methodology to quantitatively evaluate forward and backward light scattering from intraocular lenses

The scanning light scattering profiler (SLSP) methodology has been developed for the full-angle quantitative evaluation of forward and backward light scattering from intraocular lenses (IOLs) using goniophotometer principles. This protocol describes the SLSP platform and how it employs a 360&#176; rotational photodetector sensor that is scanned around an IOL sample while recording the intensity and location of scattered light as it passes through the IOL medium. The SLSP platform can be used to predict, non-clinically, the propensity for current and novel IOL designs and materials to induce light scatter. Non-clinical evaluation of light scattering properties of IOLs can significantly reduce the number of patient complaints related to unwanted glare, glistening, optical defects, poor image quality, and other phenomena associated with the unintended light scattering. Future studies should be conducted to correlate SLSP data with clinical results to help identify which measured light scatter is most problematic for patients that have undergone cataract surgery subsequent to IOL implantation.

Goniophotometry measurements can produce 360&#730;R of signal when the sensor is not located on the plane of the light source. However, to collect measurements from scattered light on the plane of the light source (0&#730;I) the sensor will need to eclipse the light source, resulting in less than 360&#730;R of signal. In our experiments, it was determined that ~20&#730;R of signal was blocked as the sensor eclipsed the light source.
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Watch this Scientific Journal Video about Scanning Light Scattering Profiler SLPS Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses at JoVE.com

Scanning Light Scattering Profiler SLPS Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses

This protocol describes the scanning light scattering profiler (SLSP) that enables the full-angle quantitative evaluation of forward and backward scattering of light from intraocular lenses (IOLs) using goniophotometer principles.

Scanning Light Scattering Profiler (SLPS) Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses

The scanning light scattering profiler (SLSP) methodology has been developed for the full-angle quantitative evaluation of forward and backward light ...

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