The Effects of Surgical Factors on Post-Operative Astigmatism in Patients Enrolled in the Infant Aphakia Treatment Study (IATS) Open Access
Lee, Jason Andrew (2013)
Abstract
Cataract surgery in infants is a very complicated process, with no clear answers on the proper treatment and rehabilitation. While contact lenses are the traditional optical correction after lens removal, physicians have advocated using an intra-ocular lens (IOL) to achieve better visual outcomes. This thesis focuses on one such outcome, astigmatism. We examine whether different demographic factors or factors within the surgical technique affect severity of post-operative astigmatism levels. Many of these factors are unexplored as they relate to aphakic infants. Data were obtained from 114 patients enrolled in the Infant Aphakia Treatment Study (IATS) at baseline (date of cataract removal surgery) and 1 year of age. Outcome measurements included keratometric astigmatism levels at baseline, 1 year, and the difference between the two time points. 1 and 2-sample t tests were used to assess the bivariate relationships between factors and astigmatism. Additionally, two regression models were fit, using surgical factors: a stepwise model, using p = 0.10 as stay criterion, and a mixed model with age as a random effect. While keratometric astigmatism in fellow eyes significantly decreased at 1 year of age (p = 0.0003), levels in treated eyes did not significantly change (p = 0.362). The contact lens group had significantly less astigmatism at 1 year than the IOL group, a difference of 0.47 D (p = 0.023). All other comparisons were insignificant at α = 0.05. However, the significant differences in bivariate comparisons are less than 0.5 diopters, a clinically insignificant value. The stepwise regression model for surgical factors included incision location and the number of sutures. The small sample size of reviewed surgeries, and the lopsided divide of some factors within the surgical technique, means that some results should be viewed with caution.
Table of Contents
TABLE OF CONTENTS
Chapter 1:
INTRODUCTION.............................................................................................
1
1.1: Cataracts and Cataract
Surgery............................................................................
1
1.2: The Infant Aphakia Treatment Study
(IATS)......................................................
1
1.3: What Is
Astigmatism?...........................................................................................2
1.4: Research
Question................................................................................................
2
Chapter 2: LITERATURE
REVIEW.................................................................................
4
2.1: The Importance of
IATS.......................................................................................
4
2.2: Surgical Factors of
Interest....................................................................................4
2.3: Demographic Factors of
Interest...........................................................................
5
Chapter 3:
METHODS.........................................................................................................
7
3.1: Data
Collection......................................................................................................7
3.2: The
Dataset...........................................................................................................
7
3.3: Bivariate
Associations..........................................................................................
8
3.4: Regression and Mixed
Modeling.........................................................................
9
Chapter 4:
RESULTS..........................................................................................................
10
4.1: Astigmatism in Treated vs. Fellow
Eyes............................................................
10
4.2: Comparisons of Demographic Factors and
Treatment....................................... 11
4.3: Comparisons of Surgical
Factors........................................................................
12
4.4: Model
Selection..................................................................................................
14
Chapter 5:
DISCUSSION....................................................................................................
16
5.1: Significant
Results..............................................................................................
16
5.2:
Cautions..............................................................................................................
17
5.3:
Conclusion..........................................................................................................
17
References.............................................................................................................................
19
Appendix A:
Tables..............................................................................................................
21
Appendix B: Relevant
Figures............................................................................................
25
Appendix C: Code..........................................................................................54
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