As premium cataract refractive surgeons, we are bombarded with a variety of outstanding advanced diagnostic tests to assist us in selecting the best options to achieve the best outcomes for our patients. Recently, the diagnostic armamentarium has continued to expand, especially in the area of anterior segment imaging. What becomes even more challenging is trying to interpret the overwhelming amount of data in a matter of minutes so the patient encounter is customized into the best premium lifestyle decision.
The three most exciting technologies implemented in my practice have been the AcuTarget HD ocular scatter analyzer (AcuFocus), the Cassini Total Corneal Astigmatism (TCA) analyzer (i-Optics) and the Lipiview II Interferometer with Dynamic Meibomian Imaging (TearScience). They all, alone or in combination, aid in optimizing the ocular surface, in treating the correct magnitude and axis of astigmatism, and in selecting the proper corneal vs. lenticular surgical procedure.
Optimizing the surface and selecting the proper procedure
Light scattering causes uniform distribution of light across a wide region of the retina, and conditions that can affect light scatter are the anterior or any layer of the cornea, flare and/or cell in the aqueous, cataracts at any stage, and asteroid hyalosis in the vitreous cavity. Light scatter measurement on the AcuTarget HD device is an excellent means to quantitate lens changes at any stage. Low light scatter, defined as objective scatter index (OSI) on this device, suggests good optical clarity and only a low-grade dysfunctional lens syndrome (DLS stage 1 or 2), as established by George Waring IV. High light scatter suggests poor quality of vision, either from true cataract formation or a poor ocular surface.
Artal and colleagues have published that OSI scores are highly correlated with LOCS III-accepted cataract grading scale. Measuring OSI every 0.5 second for 20 seconds can give a clear measure of tear film stability and corresponding effect on optical quality. Using this information with other ocular surface diagnostic modalities, such as tear osmolarity (TearLab) and MMP-9 detection (InflammaDry, RPS), it becomes much easier to determine if pathology related to visual function is ocular surface and/or lens related.
The objective data from OSI analysis and other appropriate diagnostic tests such as OCT analysis of the macula can determine if a patient should undergo a corneal vs. lenticular surgical approach, for example, for presbyopia. With the Kamra inlay (AcuFocus) possibly approaching FDA approval in the U.S. and with topography-guided applications for laser vision correction already approved in the U.S. (WaveLight, Alcon), the need to determine if a patient should have a corneal or lenticular procedure to obtain optimal vision becomes ever more important. The AcuTarget HD device with other appropriate diagnostic tests will aid in this surgical delineation of approach and is quite easy to demonstrate to the patient in the exam lane via EHR efficiencies.
Treating the correct astigmatism magnitude and axis
Once it has been determined to go forward with a lens-based surgery (either refractive lens exchange or cataract surgery), managing astigmatism is just one of many critical items that need to be done near perfection to hit the visual end target. Current planning by most surgeons involves anterior cornea data only, and the lack of posterior astigmatism data can wreak many postoperative surprises and unwanted enhancements and secondary procedures for the patient and surgeon.
With-the-rule (WTR) posterior astigmatism occurs in about 80% to 88% of patients between the ages of 60 and 79 years, and against-the-rule (ATR) and oblique posterior astigmatism occurs in about 12% to 20% of patients in this same age range. Koch has optimized toric IOL selection based on the Baylor nomogram, which takes into effect of about 0.3 D (up to 1.1 D) of posterior astigmatism. The Cassini TCA analyzer measures both anterior and posterior astigmatism in a quantitative way, yielding that magic total corneal astigmatism TCA number that can now be used to select the appropriate toric IOL or place the appropriate arc length if limbal relaxing incisions are being performed. The Cassini technology uses a multi-colored LED point-to-point ray tracing for anterior corneal astigmatism measurement and second Purkinje point-to-point ray tracing technology for measuring posterior corneal astigmatism. In the end, total corneal analysis in terms of magnitude and axis can be achieved with one automated imaging session with no need for additional testing. The surprise of posterior astigmatism effect can then be eliminated.
In the end, there are many diagnostic devices out there, and selection of the devices that will enhance the premium experience is critical when it comes to optimizing the ocular surface, delineating lens changes and managing posterior astigmatism effect.
Artal P, et al. PLoS One.
Koch DD, et al. J Cataract Refract Surg.
Koch DD, et al. J Cataract Refract Surg.
For more information:
Mitchell A. Jackson, MD, can be reached at Jacksoneye, 300 N. Milwaukee Ave., Suite L, Lake Villa, IL 60046; email: email@example.com
Disclosure: Jackson reports he is a consultant for i-Optics, TearLab and TearScience and is a shareholder in RPS.