Itrace posterior corneal aberrations12/29/2023 The iTrace is particularly helpful when the refractive result is not as good as expected after toric IOL implantation (Figure 1A). When there is significant refractive astigmatism present, I like using the iTrace in order to determine the amount of corneal lenticular astigmatism. This may alter the axis that I use for toric IOL calculations. In eyes with significant astigmatism, the Cassini provides another reliable source for magnitude and axis of corneal astigmatism. This IOL must be rotated 38º clockwise in order to gain the full effect of the toric IOL (B). Ideally, the toric IOL and corneal astigmatism axes should coincide in order to fully address the refractive astigmatism. The effect of the toric IOL is shown top left. Postoperative iTrace maps (A) showing entire eye’s wavefront (top right) and corneal wavefront (bottom left). These factors all impact the timing of surgery and the choice of IOL.įigure 1. I have also diagnosed many epiretinal membranes on OCT that I simply never saw on fundus exam at the slit lamp using 78.00 or 90.00 D lenses. I like to see the state of the nerve fiber layer and the macular retinal pigment epithelium, and I am also keen on seeing the state of the posterior vitreous and whether there has been a total posterior vitreous detachment or there is some vitreomacular traction present. I typically try to obtain an OCT of the macula and optic nerve for all patients undergoing cataract or clear lens extraction surgery, not just those who receive premium IOLs. Knowing the toricity of the posterior corneal surface also helps with the choice of a toric IOL. Knowing these things can prompt me to select an IOL solution over LASIK or other corneal refractive surgical solutions if the dimensions are sufficiently reduced. Corneal tomography is also valuable in terms of the above, but in addition it provides more anterior chamber dimensions in terms of angle, depth, and volume. On the odd occasion, however-if the clinical picture warrants it-I add iTrace topography and aberrometry and Cassini corneal topography (i-Optics).Ĭorneal topography is essential to determine any irregular astigmatism and identify a large angle kappa, two clinical conditions that will prevent me from using multifocal IOLs. I do the following diagnostic tests routinely: corneal topography, corneal tomography, and optical coherence tomography (OCT) of the macula and optic nerve. CUMMINGS, MB ChB, FCS(SA), MMed(Ophth), FRCS(Edin) Chang is a member of the CRST Europe Global Advisory Board and states that he has no financial interest in any instrument or technique he describes. Chang, MD, is a Clinical Professor at the University of California, San Francisco, and in private practice in Los Altos, California. An entire bilateral exam takes only a few minutes, and the machine footprint is like that of any topographer.ĭavid F. The iTrace also automatically measures angle kappa and angle alpha and has a unique toric IOL planner. This is helpful with some astigmatic patterns, particularly post-LASIK patterns. By totaling data from 600 individual ray tracings through the central 3-mm zone, it gives a best-fit K reading that is quite often different from the traditional K reading from a single 3-mm ring. Knowing this information is important if a multifocal IOL is considered, and I have decided against using a diffractive multifocal lens in many cases because of the corneal HOAs measured through a particular patient’s actual pupil size in a dimly lit room.įinally, the iTrace topographer not only provides a traditional 3-mm simulated keratometry (SimK) reading but also maps the refractive keratometry (K). For example, corneal irregularity measured over a standard 6-mm diameter zone may not be problematic with a 2-mm pupil. Additionally, it performs pupillometry and quantifies the HOAs that the patient would see through that specific pupil diameter. Most important, it measures and calculates the higher-order aberrations (HOAs) of the cornea separately from those of the internal optics (eg, the lens). In addition to being a topographer, the iTrace simultaneously performs wavefront aberrometry. There are several useful diagnostic technologies, but one that I find indispensable is the iTrace (Tracey Technologies). How Much Astigmatism Do I Fix With Cataract Surgery? POINT/COUNTERPOINT: DOES INTRAOPERATIVE ABERROMETRY MATTER? Improving Refractive Outcomes With the Verion SystemĬirle: A Digital Tool for Surgical Navigation and GuidanceĬallisto Eye: Seamless Integration With Other ProductsĬassini: Providing True Axis and Magnitude of AstigmatismĪdvancing Cataract Surgery With Diagnostic Technologies Pharmacologic Approach to Presbyopic Correctionĭislocated IOL Levitation With a Sleeveless Extrusion Cannula Advances in Smartphone Photography of the Eye
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