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Automatic cyclorotation measurement with a femtosecond Cataract laser

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Posterboard#: A0445

Abstract Number: 1685 - A0445

AuthorBlock: David Dewey1, Douglas Koch4, Li Wang4, Tal Raviv3, Luis Atiles1, Quynh Nguyen1, Joris Snellenburg2, Maarten Huijbregtse2, Joris Vogels2
1R&D, Johnson+Johnson Vision, Milpitas, California, United States; 2Cassini Technologies BV, , Netherlands; 3Eye Center of New York, New York, United States; 4Baylor College of Medicine, Texas, United States;

DisclosureBlock: David Dewey, Johnson + Johnson Vision Code E (Employment), Douglas Koch, Johnson + Johnson Vision Code F (Financial Support), Li Wang, Johnson + Johnson Vision Code F (Financial Support), Tal Raviv, Johnson + Johnson Vision Code F (Financial Support), Luis Atiles, Johnson + Johnson Vision Code E (Employment), Quynh Nguyen, Johnson + Johnson Vision Code E (Employment), Joris Snellenburg, Cassini Technologies BV Code E (Employment), Maarten Huijbregtse, Cassini Technologies BV Code E (Employment), Joris Vogels, Cassini Technologies BV Code E (Employment)

Purpose
Accurate alignment of arcuate incisions for the treatment of corneal astigmatism is complicated by rotations of the patient’s eye between pre-operative measurements and the position of the patient’s eye while docked to the treating laser system. To aid the treating physician in determining the amount of rotation, an automated method of measuring the cyclorotation between pre-operative and docked images of the eye was developed. This study is intended to find both the amount of cyclorotation present in femtosecond laser cataract surgery, and the accuracy of the automated measurement of cyclorotation.

Methods
Retrospective pre-op image pairs were collected from a CASSINI topographer, and CATALYS Precision Laser for patients who underwent cataract surgery at two clinical sites. The image pairs were graded for cyclorotation between the pre-op and docked conditions by at least 3 different graders aided by an image based computer grading tool. The cyclorotation between paired images was independently computed by an automated algorithm, that is incorporated into the femtosecond laser system. The algorithm was based on correlation of the iris portions of the images as segmented between the pupil and limbus and returned a cyclorotation angle in degrees. The accuracy of the automated laser system cyclorotation measurement was assessed by comparison to the average cyclorotation determined by the three human graders.

Results
Forty-nine (49) image pairs of cataract patients in total were collected from two clinical sites. The age and sex of the patients were not disclosed. There were 37 eyes from site one and 12 eyes from site two, 22 eyes OD and 27 eyes OS. The range of measured cyclorotation was 25°(max18°, min.-7°, σ=6.5° ) for the human graders, and 27°(max17°, min.-10°, σ=6.6° ) for the automated algorithm. The automated algorithm succeeded in finding a cyclorotation angle in 96% of cases and was within 2° of the human graders in 98% of returned angles.

Conclusions
Cyclorotation in femtosecond laser cataract surgery will likely be in the range of 3σ =+/-20°. Automated determination of cyclorotation for femtosecond laser cataract patients has a high success rate of being within 2° of human graders.

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