Dissertation > Excellent graduate degree dissertation topics show

The Study on Changes of Corneal Asphericity before and after Excimer Laser Corneal Refractive Surgery

Author: HouJie
Tutor: WangYan
School: Tianjin Medical University
Course: Ophthalmology
Keywords: Cornea Myopia Asphericity Q-value Spherical aberration Keratomileusis Laser in situ
CLC: R779.63
Type: Master's thesis
Year: 2010
Downloads: 21
Quote: 0
Read: Download Dissertation

Abstract


Purpose:To evaluate the asphericity and corneal spherical aberration of the anterior and posterior corneal surface with different corneal diameters in myopic eyes, and investigate the change of the asphericity (Q-value) of the posterior corneal surface with different corneal diameters after corneal refractive surgery.Methods:Sectionl included 232 eyes of 116 myopia or myopic astigmatism patients were enrolled. Only the right eyes were included for analysis. The preoperative sphere refraction was -2.25～-7.75 D, and the cyclinder refraction was-0.50～-2. OOD.The Q-value and spherical aberration of the anterior and posterior corneal surface for different corneal diameters (6,7,8 and 9mm) were measured with Pentacam. The correlations between Q-value and spherical aberration, corneal refraction and central corneal thickness (CCT) were investigated.Section 2 included 115 myopic eyes of 115 subjects (59 LASIK,56 EPI-LASIK) having corneal refractive surgery were enrolled in this prospective study. The Q-value of the posterior corneal surface for different corneal diameters (6,7,8 and 9mm) were measured with Pentacam preoperatively and postoperatively. The correlations between Q-value, Q change (△Q), and the preoperative spherical equivalent refraction (SE), CCT, central ablation depth (AD) were investigated.Results:1. The Q6mm, Q7mm, Q8mm, Q9mm of the anterior corneal surface of the 116 eyes were-0.24±0.09、-0.29±0.09、-0.33±0.09 and-0.39±0.10, respectively; The Q6mm, Q7mm, Q8mm, Q9mm of the posterior corneal surface of the 116 eyes were-0.12±0.12,-0.21±0.11,-0.30±0.10 and-0.38±0.10, respectively.2. Q-value of the anterior corneal surface were more negative than the posterior corneal surface (t6mm=-10.353, P=0.000; t7mm=-6.684, P=0.000; t8mm=-3.455, P=0.001; t9mm=-0.026, P=0.979). Positive relationships were found between the anterior corneal surface and the posterior corneal surface (r6mm=0.302, P=0.001; r7mm= 0.367, P=0.000; r8mm=0.399, P=0.000; r9mm=0.424, P=0.000)3. Positive relationships were found between anterior Q-value and the cyclinder refraction (r6mm=0.280, P=0.002; r7mm=0.268, P=0.004; r8mm=0.246, P=0.008; r9mm=0.217, P=0.019). Negative relationships were found between posterior Q-value and CCT (r7mm=-0.183, P=0.049; r8mm=-0.212, P=0.022; r9mm=-0.238, P=0.010). No statistically significant correlation between Q and age or sex was found in this study(P>0.05).4. Linear correlation between Q-value and corneal spherical aberration were found. With a 6mm corneal diameter, the regression equation of the anterior corneal surface was SA=0.663Q+0.415, and the posterior corneal surface was SA=0.159Q-0.177.5. The mean Q-value of the posterior corneal surface of the 115 preoperative eyes for the corneal diameters of 6,7,8 and 9mm were 0.08±0.16,-0.05±0.13,-0.15±0.12 and-0.26±0.11, respectively. The Q-value had a statistically significant positive shift 1 month after surgery at 6,7,8 mm corneal diameter. The mean Q-value diminished significantly 6 months compared to 1 month after surgery, and had an obvious tendency back to its preoperative level.6. No statistically significant correlation between Q and SE or CCT was found in the preoperative eyes. Also, no correlation between△Q and SE, CCT, AD and AD/CCT was found after surgery.Conclusions:1. Both the anterior and the posterior corneal surface of the myopic eyes were prolate. With increasing corneal diameter Q-value became more negative (indicating an increased rate of flattening in the peripheral cornea).2. The relationship between Q-value and corneal spherical aberration can provide more valuable instructions for refractive surgeons to design the aspheric ablation.3. The posterior corneal surface showed central flattening and peripheral steepening (oblate shift) at early stage either post-LASIK or post-EPI-LASIK, and then returned to its original state over time.

Related Dissertations

  1. An Ethical Analysis of Consumption Values in Contemporary China,F014.5
  2. Research on How Sports Anime Affect Youth Value of Basketball,G841
  3. Dai junior high school students the educational needs of value orientation,G755.5
  4. Study on the Development of Folk Sports Non-Profit Organization,D632.9
  5. Research on Liquidity Requirements and Efficiency in Large-value Payment Systems,TP301.6
  6. The Research on Mechanism of NaHCO3 in the Prevention and Cure of the Dothiorella Gregaria,S763.7
  7. S Philosophy of Wang Yangming,B248.2
  8. With the Socialist Core Value System and Bring the Students,D267.6
  9. The Morphology and Challenges of Contemporary Public Administration Theories,D035
  10. Research on Values of Post-90 Generation under the Influence of the Current Pop Culture,C913.5
  11. The Research on Socialism Feminism,C913.68
  12. Study on Entertainment Value of Martial Arts,G852
  13. The Research of Dynamic Trust Model on Cloud Computing Platform,TP309
  14. The Research on Relationship between Capital Structure and Enterprise Value in Listed Companies of Construction Industry,F426.92
  15. Study on Nitrogen Accumulation Characteristics of Winter Wheat with Yield of 10t/ha, Diagnosis and Nitrogen Application Technologies,S512.1
  16. The Analysis of the Social Institution of Realization of Individual Value,B038
  17. Multi-dimensional harmony under the guidance of one yuan,D61
  18. The Study of Socialist Core Value System Leading the Ideological Education of Farmers,D422.62
  19. A Smoothing Method for Solving Model under WCVarR,O224
  20. The Comparative Study of Competitive Advantage in the Self-Owned Clothing Brands of Beijing,F426.86
  21. The Empirical Research of the Important Factors of the Financial Risks of Chinese A-share Construction Enterprises Market,F426.92

CLC: > Medicine, health > Ophthalmology > Eye surgery and surgery > Retinal photocoagulation and laser eye surgery
© 2012 www.DissertationTopic.Net  Mobile