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Correlation Of Corneal Contour With Higher Order Ocular Aberrations (HOA) In Indian Eyes

Correlation Of Corneal Contour With Higher Order Ocular Aberrations (HOA) In Indian Eyes . ID 737882. Manish Chaudhary MS Amit Gupta MS Advanced Eye Centre, Postgraduate Institute of Medical Education & Research, Chandigarh India (Email : amitguptaeye@gmail.com).

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Correlation Of Corneal Contour With Higher Order Ocular Aberrations (HOA) In Indian Eyes

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  1. Correlation Of Corneal Contour With Higher Order Ocular Aberrations (HOA) In Indian Eyes ID 737882 • Manish Chaudhary MS • Amit Gupta MS • Advanced Eye Centre, • Postgraduate Institute of Medical Education & Research, • Chandigarh • India • (Email : amitguptaeye@gmail.com) The authors have no financial interest in the subject matter of this poster

  2. Role of Corneal Contour The anterior corneal surface is the major refractive component of the human eye and major determinant in quality of optical image Ideally, cornea must have an optical zone consisting of an elliptical surface with an adequate shape factor (Q factor or asphericity) to minimize curvature induced ocular aberrations and optimal image formation. Calossi A. Corneal Asphericity and Spherical Aberration. J Refract Surg 2007;23:505-514. Limited literature exists correlating corneal asphericity with ocular aberrations. To the best of our knowledge, this is the first study correlating Higher order ocular aberrations with asphericity of corneal contour.

  3. Purpose Patients and Methods Correlation Of Corneal Contour With Higher Order Ocular Aberrations (HOA) In Indian Eyes Study Design: An observational cross sectional prospective study Study Population • Group I : 500 emmetropic eyes (refractive error 0+0.25 D) • Group II : 500 myopic eyes (refractive error > -0.25 to < -6.0 diopters)

  4. Methods Inclusion criteria • Age 18-40 years. • Best corrected visual acuity (BCVA)of 6/9 or better. • Normal ocular examination, emmetropia or Myopia < 6 D. Patient Workup: • Best Corrected Visual Acuity, • Slit Lamp Biomicroscopy, • Refraction, • Schirmer’s test, • Aberrometry:Optical Path Difference (OPD) Scanning done after dilating with 0.8% tropicamide and 5% phenylephrine using ARK-10000 OPD scan (NIDEK Technologies, Japan) Exclusion criteria • Corneal degenerations and dystrophies • Corneal scarring after infective diseases • Dry eye patients • Any Other ocular pathology

  5. Aberrometric Data Interpretation and Analysis Step 1: OPD Scan Analysis Step 2: Zernike polynomials at 6mm transformed into • Root mean square (RMS) of higher order aberration (HOA) from the 3rd to 6th orders • RMS of the spherical aberration (SA) (square root of the sum of the squared coefficients of Z40 and Z60), • RMS of coma (square root of the sum of the squared coefficients of Z3-1, Z31, Z5-1,and Z51), • RMS of trefoil (square root of the sum of the squared coefficients of Z3-3, Z33, Z5-3,and Z53 Thibos et al. Standards for reporting the optical aberrations of eyes. J Refract Surg 2002; 18:S652–S660 Step 3: Statistical Analysis • ‘t-test’ (for normal Distribution) & for skewed data Mann- Whitney test. • Relationship between different variables using Spearman and Pearson correlation coefficient Aberrometric Analysis by OPD Scan

  6. Results Patients characteristics in emmetropic and myopic group Keratometric values in emmetropic and myopic group Number of eyes in different subgroups

  7. Comparison of wavefront error and keratometry value in emmetropic eyes keratometry value in Emmetropic eyes Emmetropic group : Higher keratometry values (>46 D) were associated with significantly higher amount of total wavefront aberration, total higher order aberrations, 3rd, 5th order as well as trefoil

  8. Comparison of wavefront error and keratometry value in myopic eyes keratometry value in Myopic eyes Myopic group : Higher keratometry values (>46 D) were associated with significantly higher amount of trefoil

  9. Figure : Comparison of asphericity coefficient (Q) value along steep , flat axis and average in emmetropic versus myopic eyes Figure : Distribution of asphericity coefficient (Q) in emmetropic and myopic eyes We found most common Asphericity coefficient (Q) value is between 0 to -1 (prolate ellipse) in both the groups Distribution of Q value in emmetropic and myopic eyes (prolate versus oblate cornea)

  10. Significance of wavefront aberrations with Corneal Asphericity in emmetropic eyes The mean RMS value of total HOAs, coma, and spherical aberration were significantly higher in oblate then prolate corneas Significant association of total HOA, coma, spherical aberration with Oblate cornea in emmetropic eyes

  11. Significance of wavefront aberrations with Corneal Asphericity in myopic eyes The mean RMS value of total HOAs and spherical aberration were significantly higher in oblate then prolate corneas Significant association of total HOA, spherical aberration with Oblate cornea in myopic eyes

  12. Our study highlights the association of corneal asphericity with HOA Higher keratometric (>46 D) and oblate cornea were associated with significantly higher amount of HOAs Emmetropic eyes • Higher keratometric value > 46 diopter was associated with significantly higher value total wavefront aberration, total HOAs, 3rd order, 5th order as well as trefoil • We found Oblate corneas (Q > 0) were associated with higher total HOAs, coma and spherical aberration • Myopic eyes • Higher keratometric value > 46 diopter was associated with significantly higher value of trefoil • Oblate corneas (Q > 0) were associated with higher total HOAs and spherical aberration

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