Optimized Nomograms
Optimizing refractive surgery outcomes requires personalized
nomograms that account for variations in equipment, surgical technique, the
operating environment, and each individual eye.
Since
1998, Jack T. Holladay, MD, MSEE and Guy M. Kezirian, MD, FACS have collaboratively
developed the Optimized Nomograms™ algorithm, a sophisticated method
for leveraging information to improve surgical outcomes. The goal? To improve
predictability, decrease the need for reoperations, and avoid "surprise"
results by better analyzing preoperative characteristics.
The math behind Optimized Nomograms™ is complex, but the Refractive Surgery
Consultant™ Elite brings it all to you at the touch of a button. This
versatile program evaluates over a dozen patient and surgical parameters for
statistical significance, and then applies only those parameters which affect
your results. The result is a truly customized nomogram for every surgeon
using every laser for every operation in your practice.
The impact of Optimized Nomograms™ on your surgical results can be very
significant. Reports from users of the Refractive Surgery Consultant™
show reductions enhancement rates of up to 75% using the program. While individual
results may vary, the ability to compensate for sphere/cylinder coupling,
effects of optical zone changes, and other aspects of the laser algorithm
can greatly improve surgical predictability.
Optimized Nomograms™ provide the surgeon with a great deal of information
at the time of surgical planning. For example, nomogram accuracy, recommended
age adjustments, and other information - calculated specifically for each
eye - are provided, to assist with setting the target amount to achieve the
desired outcome. This level of understanding can be very helpful in the clinical
setting, and can help avoid unwanted outcomes.
In addition to detecting and compensating for variables that influence outcomes,
Optimized Nomograms™ also detect changes that occur over time. For example,
recent work has shown that laser servicing may significantly alter laser performance.
By use of trailing windows, which incorporate only the most recent data, and
just enough data to achieve a certain level of predictability, Optimized Nomograms™
change to compensate for these changes.
Other elements of Optimized Nomograms™ include:
- A sophisticated, multi-step, iterated algorithm
based on extensive computer modeling of actual refractive data sets from
many lasers, to detect possible influences on refractive outcomes.
- Extensive data grouping to detect subtle influences
of techniques and equipment on outcomes. Once differences are detected,
new nomograms are produced and automatically applied in surgical planning.
- Sophisticated, relational data validation to help
avoid contamination of the nomograms by erroneous data.
- Data filtering to exclude outliers, and identify
and retain rare eyes.
- Utilization of correct statistical and mathematical
methods, such as vertexing refractions to the corneal plane, standardizing
cylinder notation, qualifying variables for statistical significance before
incorporating them into nomograms, etc.
- Careful analysis of the surgical plan is done behind
the scenes, and warnings are provided if necessary.
- Consideration of user-defined variables allow you to search for possible influences on outcomes, with automatic incorporation into nomograms if they are significant.
Optimized Nomograms™ have their first application in Surgical Planning. However, they can also be used to validate laser calibration, to monitor laser performance over time, to calibrate lasers for wavefront-guided procedures, to search for influences of specific surgical variations, and for many other purposes.
