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Reanalysis of Refractive Growth in Pediatric Aphakia and Pseudophakia

Reanalysis of Refractive Growth in Pediatric Aphakia and Pseudophakia. Susan Whitmer, MD 1 Aurora Xu 2 Scott McClatchey, MD 1,3,4 1 Naval Medical Center San Diego 2 Byram Hills High School, Armonk NY 3 Uniformed Services University of the Health Sciences 4 Loma Linda University

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Reanalysis of Refractive Growth in Pediatric Aphakia and Pseudophakia

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  1. Reanalysis of Refractive Growth in Pediatric Aphakia and Pseudophakia Susan Whitmer, MD1 Aurora Xu2 Scott McClatchey, MD1,3,4 1 Naval Medical Center San Diego 2 Byram Hills High School, Armonk NY 3 Uniformed Services University of the Health Sciences 4 Loma Linda University The authors have no financial interest in the subject matter of this poster. The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government.

  2. Introduction The growth of an aphakic or pseudophakic eye results in myopic shift. The vertex distance of a spectacle lens causes the effective power to be higher at the cornea; this is greatest in babies less than 6 months of age.

  3. Vertex distance artifact in RRG In utero “Aphakic” refraction +100 D BUT THIS CANNOT BE: 100 D at spectacle plane => -500 D vergence at cornea At birth “Aphakic” refraction +21 D Adult “Aphakic” refraction +11 D

  4. Purpose The current model for logarithmic refractive growth (RRG2) is defined by the slope of the line of aphakic refraction at the spectacle plane vs. adjusted age. We developed a new model “RRG3”, to address the optical artifact induced by the vertex distance.

  5. Methods We reanalyzed eyes previously studied for RRG1,2. Children 10 years old or younger, at the time of cataract surgery, were included. Each study eye had recorded follow-up refraction data of at least 3.6 yr and at least equal to the age at first refraction + 0.6 yr. For bilateral cases, only data from the right eye was used. Based upon the vergence at the different surfaces in the eye, a new formula, “W”, was developed to calculate the IOL power required for a given refraction, axial length and IOL A constant: IOL power = vergenceback of IOL – vergencefront of IOL We assumed that the radius of curvature of the cornea, axial length and thickness of the cornea are all proportionate, with a limit to the anterior cornea radius of 8.9mm.

  6. Methods Using Excel Visual Basic for Applications and iteration, we calculated the IOL power for emmetropia (aphakic refraction at the natural lens plane), based upon the available data for the study eyes at each age. From the IOL power for emmetropia, RRG3 was calculated as follows: where AdjAR is the adjusted aphakic refraction, calculated for each individual eye at the natural lens plane, and AdjAge is the same adjusted age we used for RRG2 (i.e., age + 0.6 yr). The “1" and “2" refer to the initial and follow-up measurements, respectively.

  7. Results • 78 pseudophakic and 70 aphakic eyes were analyzed.

  8. Results

  9. Conclusions • The data did not show a difference in RRG3 between eyes that had surgery at less than 6 months of age and those that had surgery at 6 months of age or after. • There was a significant difference in RRG3 for pseudophakic and aphakic eyes.

  10. Discussion • The observation that RRG3 was not found to be different for the different age groups is consistent with the hypothesis that the observed difference in RRG was due to the vertex distance artifact. • The "W formula," from which RRG3 was calculated, needs further testing in infant aphakic and pseudophakic eyes to assess its accuracy.

  11. References • McClatchey SK, Dahan E, Maselli E, Gimbel HV, Wilson ME, Lambert SR, Buckley EG, Freedman SF, Plager DA, and Parks MM. “A Comparison of the Rate of Refractive Growth in Pediatric Aphakic and Pseudophakic Eyes.” Ophthalmology 2000; 107:118-122. • McClatchey SK and Hofmeister EM. “The Optics of Aphakic and Pseudophakic Eyes in Childhood.” Survey of Ophthalmology 2010; 55.2:174-182. • Hoffer KJ. “The Hoffer Q formula: A comparison of theoretic and regression formulas.” J Cataract Refract Surg 1993; 19:700-712. • Holladay JT, Prager TC, Chandler TY, Musgrove KH, Lewis JW, and Ruiz RS. “A three-part system for refining intraocular lens.” J Cataract Refract Surg 1988; 14.1:17-24. • Lambert SR. “The Effect of Age on the Retardation of Axial Elongation Following a Lensectomy in Infant Monkeys.” Arch Ophthalmol 1998; 116:781-784. • Lambert SR, Fernandes A, Drews-Botsch C and Tigges M. “Pseudophakia Retards Axial Elongation in Neonatal Monkey Eyes.” Investigative Ophthalmology and Visual Science 1996; 37.2:451-458. • McClatchey SK and Parks MM. “Theoretic Refractive Changes after Lens Implantation in Childhood.” Ophthalmology 1997; 104:1744-1751.

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