Surgeons weigh technologies for visual analysis of refractive cataract patients
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Welcome to another edition of CEDARS/ASPENS Debates. CEDARS/ ASPENS is a society of cornea, cataract and refractive surgery specialists, here to discuss some of the latest hot topics in ophthalmology.
This month, Timothy Page, MD, and I. Paul Singh, MD, discuss their preferred technologies for the visual analysis of patients before and after refractive cataract surgery. We hope you enjoy the discussion.
Kenneth A. Beckman, MD, FACS
OSN CEDARS/ASPENS Debates Editor
OPD-Scan III: Thousands of data points within seconds
The Nidek OPD-Scan III is indispensable in my practice where I specialize in refractive cataract surgery and IOL complication management.
This remarkable device provides thousands of data points within seconds, enabling a comprehensive examination of the cornea and lens.
The first thing I look at is the topography, but unlike standard topographers, the OPD-Scan III provides the patient’s spherical aberration in the cornea. It also displays the patient’s photopic and mesopic pupil size and angles alpha and kappa. I see these data points in a matter of seconds, and they allow me to quickly narrow down the lens possibilities for the patient.
Next, I look at the cornea’s higher-order aberration profile. It gives me the confidence of whether or not we can use a multifocal IOL. I use caution or avoid using them altogether when higher-order aberrations are higher than normal.
The same features that allow me to advise patients on which IOL is best for them also allow me to analyze postoperative patients who are having problems. In a matter of seconds, I can see if their IOL is tilted with induced astigmatism or higher-order aberrations. I review their angle alpha, topography and corneal higher-order aberration profile and identify their problem. I can show them a point spread function of their total optical system, separating the corneal aspect from the IOL. It is often an “aha” moment for the patient, where they have instantaneous relief in knowing that we have at least identified the issue.
Another invaluable feature of the OPD-Scan III is the toric analyzer. It captures an image of the IOL and overlays the topographical axis across the toric IOL. It tells you precisely how many degrees the IOL cylinder is off axis.
Finally, the retro-imaging feature of the OPD-Scan III is helpful for managing subluxated IOLs. It allows me to show the patient what the problem is and what I am going to do to fix it. I take that image to the operating room for surgical planning.
In summary, I think what sets OPD-Scan III apart from other systems is the speed in which the technicians can capture the scan. In a matter of seconds, my staff can provide me with thousands of data points that allow me to look at one screen and make quick decisions and help patients make theirs. Frankly, I could not function as a refractive cataract surgeon without this technology.
- For more information:
- Timothy Page, MD, co-chief of anterior segment surgery and professor of ophthalmology at Oakland University William Beaumont School of Medicine, can be reached at tpagemd@yahoo.com.
iTrace: Understanding of entire optical system
When we assess a patient, we have to take into consideration multiple variables in order to make an informed decision based on their needs but also on their anatomy and physiology.
I like the iTrace (Tracey Technologies) because it gives me a true understanding of the quality of the optical system from front to back. It provides accurate and complete information on the quality and biomechanical properties of the cornea, the quality of the lens, and what is going on in the vitreous. The iTrace sends 256 light rays through the cornea to the retina, measuring the point spread function, size and intensity of the rays hitting the retina. It gives me the total aberration profile but can also separate the cornea from the internal optics, enabling me to understand the contribution of the lens vs. the cornea when it comes to quality of vision. For instance, if the higher-order aberration of the cornea is high. I will likely avoid implanting a multifocal IOL. It provides corneal topography with wavefront keratometry and provides for a repeatable and accurate autorefraction.
If a patient has a refraction with no astigmatism in their glasses and the iTrace tells me that there is some amount of corneal astigmatism, which is compensated by lenticular astigmatism, I will make them aware that after the lens is removed, they will be left with this corneal astigmatism. I can display this on the screen. Subjective vision simulation also allows me to show them the quality of image they can expect looking through their cornea and how I can improve it by taking care of the astigmatism and other corneal aberrations. The iTrace also helps us select the appropriate IOL by measuring centration of the visual axis (angle alpha) and helps to explain to our patients the value of premium IOL technologies with defocus curves.
One of the features of iTrace is the dysfunctional lens index (DLI), a numerical representation of the visual quality of a patient’s crystalline lens or artificial lens and vitreous. In some cases, if the quality of vision is not good but the lens is clear, there is no posterior capsule opacification, but the DLI is still low, the system tells us there are probably some vitreous opacities and can identify the contribution of floaters. If the DLI is normal and higher-order aberration of the cornea is high, that tells me to look for ocular surface disease or other corneal pathology to explain the patient’s symptoms. The latest software also allows for a high quality assessment of the tear film, which we know can affect our biometry and effect quality of vision after IOL implantation.
The iTrace is also important for postoperative management. Without dilating the pupil, I am able to perform a toric check in patients who are not happy with their vision after implantation of a toric lens. I can verify lens placement compared with the optimal axis location and how the refraction would change if I rotated the lens.
So, in a nutshell, the iTrace is a key diagnostic for me. It provides us a true understanding of the entire optical system and of the individual components of the optical system, and it lets us understand what to address, guiding our choices before and after surgery.
- For more information:
- I. Paul Singh, MD, president of The Eye Centers of Racine and Kenosha, can be reached at inderspeak@gmail.com.
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