This article is more than 5 years old. Information may no longer be current.
Navigating the diagnostic maze for today’s premium surgeon
Premium cataract surgeons use a variety of tools to try to achieve the accuracy seen in LASIK outcomes.
Click Here to Manage Email Alerts
Today’s premium cataract surgeon must be the most technologically advanced in order to achieve the greater than 90% within 0.5 D of intended target seen with LASIK outcomes, as compared to the estimated best 65% accuracy as reported throughout the literature.
Our daily grind as premium surgeons involves managing patient expectations and performing a thorough preoperative evaluation to address the ocular surface, manage astigmatism, discover macular disease early and obtain data to help select an appropriate IOL customized to the specific patient at hand. In this installment of my column, I want to focus on this diagnostic maze of technology that will allow the premium surgeon to achieve the greater than 90% outcome expected from our patients.
Managing the ocular surface
The tear film is the most important refracting surface of the eye, and managing the ocular surface is a much more complex process since it was redefined in 2007 by the International Task Force Delphi Panel on Dry Eye as a multifactorial disease accompanied by increased osmolarity of the tear film and inflammation of the ocular surface. There are a number of diagnostic tests that can now aid in this diagnosis with improved efficiency and accuracy.
The TearLab Osmolarity Test provides a quick and simple method to quantitatively measure 50 nL of tear fluid in just seconds. The maximum measurement between two eyes, if greater than 308, is pathogenic; if the difference between two eyes is greater than 8 mOsm/L, this represents tear film instability. Tear osmolarity has become a global marker for dry eye assessment and even has an advantage in determining response to therapy objectively while subjectively motivating patients to adhere to their therapy.
Devices such as the Lipiview Interferometer and hand-held Meibomian Gland Evaluator (both TearScience) respectively measure the lipid layer of the tear film in a non-contact method and assess meibomian gland secretions directly at the slit lamp to give an efficient diagnostic approach to the evaporative component of dry eye.
Other newer inflammatory tests include the in-office InflammaDry test (Rapid Pathogen Screening) to detect the inflammatory marker matrix metalloproteinase-9, which is typically elevated in the tears of dry eye patients and may be detected in high levels even before the presence of clinical signs of dry eye. Another new diagnostic test, called Sjö (Nicox), is for the detection of Sjögren’s syndrome using a simple finger stick test in the office with results from Immco lab within 48 hours. The importance of Sjögren’s is that only one in 10 dry eye patients are currently diagnosed with this condition, with the current rho antibodies found only late in the disease process, whereas Sjö allows for much earlier detection with three new proprietary immune markers (SP-1, PSP and CA-6). A large literature review conducted by Simpson et al, dated to 2012, concluded that Sjögren’s patients are the least suitable category of immune disease-related dry eye patients to undergo LASIK. In the premium channel, LASIK, PRK and limbal relaxing incisions are all utilized as enhancement tools for advanced IOL technology, so appropriate assessment in this population before refractive cataract surgery is critical.
Multiple data points
Devices such as the OPD III (Marco Ophthalmics) and the iTrace (Hoya) will give multiple data points in just seconds for both eyes, including corneal mapping, spherical aberration/coma, angle kappa and scotopic pupil, which are all useful in advanced IOL selection. Besides distinguishing corneal from lenticular astigmatism, new data published by Koch et al tells how posterior corneal astigmatism can influence visual outcomes. Ignoring posterior corneal astigmatism may yield incorrect estimation of total corneal astigmatism. The prediction error of five devices — IOLMaster (Carl Zeiss Meditec), Lenstar (Haag-Streit), Atlas (Humphrey), manual keratometer and Galilei (Ziemer) — calculated as the difference between the astigmatism by each device and the actual corneal astigmatism, revealed that corneal astigmatism was overestimated by 0.5 D to 0.6 D in with-the-rule astigmatism by all devices and underestimated by 0.2 D to 0.3 D by all devices except the Galilei. I have adjusted my toric IOL decision process based on this analysis, such that I tend to choose a toric IOL slightly undercorrecting a patient by 0.5 D who has with-the-rule astigmatism and slightly overcorrecting a patient by 0.2 D who has against-the-rule astigmatism after toric calculator vector analysis.
Refractive guidance
The newest hotbed comes in the form of guidance systems to help refractive outcomes by improving the accuracy and mapping of the surgical procedure from patient data obtained preoperatively. These guidance systems create digital overlays and allow for a markerless approach to toric IOL placement with improved centration and alignment guidance, even in the case of multifocal IOLs. The current systems of interest are the Verion Image Guided System (Alcon Laboratories), the Callisto eye (Carl Zeiss Meditec) and the Cassini (i-Optics), the latter coupled with the TrueVision platform. These new systems will simplify the overall surgical translation process, with the hope of climbing closer to the 90%+ LASIK outcomes we all desire for our patients.
Intraoperative aberrometry
The final hurdle to truly achieve these excellent outcomes has come with intraoperative aberrometry, especially in my experience. ORA’s new VerifEye system from WaveTec and Holos IntraOp (Clarity Medical Systems) allow for real-time aberrometry, which is especially useful in aphakic spherical power selection, pseudophakic toric IOL alignment and post-refractive cataract cases. My data series in post-LASIK cataract patients utilizing preoperative Haigis-L software analysis from the IOLMaster 500, as presented at the 2013 European Society of Cataract and Refractive Surgeons meeting, yielded 83% predictability within ±0.5 D postoperatively. I recently added ORA intraoperatively after my Haigis-L analysis preoperatively on this same subset of patients, and my early data have approached that desirable 93%+ predictability seen with LASIK outcomes.
In the end, the premium surgeon does not need every diagnostic technology to succeed, but the proper selection of one’s tools of the trade has just been made easier due to the advancements of technologies globally and perpetually.
Stay tuned for my next column: Do electronic health records play a dominant role for the premium surgeon?