Wavefront aberrations after Penetrating Keratoplasty

1
Wavefront aberrations after Penetrating
Keratoplasty

• Adriana Forseto, MD Telma Pereira, MD Lucila
  Pinto, MD Vera Mascaro, MD Walton Nosé, MD

Eye Clinic Day Hospital São Paulo - Brazil
2

• The authors do not have any commercial or
  proprietary interest in the subject matter of
  this paper

3
Purpose

• To analyze ocular order aberrations derived from
  LADARWave (Alcon) and Zywave (Bausch Lomb)
  devices in eyes after penetrating keratoplasty
  (PKP) eyes and to compare the clinical refraction
  with the lower order aberrations obtained from
  these two aberrometers

4
Methods

• Thirty post-PKP eyes from keratoconic patients
  were evaluated using both the LADARWave and the
  Zywave aberrometers, according to each respective
  manufacturers guidelines

5
Methods

• Ocular lower-order aberrations were evaluated for
  3.5mm diameter pupil. The obtained values were
  compared with both manifest and cycloplegic
  refractions (clinical refraction)
• To be eligible for this study all the eyes should
  have no sutures

6
Methods

• Total higher-order aberrations (HOA), 3rd HOA and
  4th HOA were documented for a 6.00mm pupil size
  and compared between the two aberrometers

7
Methods

• For statistical analysis the manifest,
  cycloplegic and aberrometers refractions were
  also converted to power vectors coordinates where
  M represents the spherical equivalent, and J0 and
  J45 the cylinder components of the refraction

8
Methods

• Statistical analysis
• Refractions Power vectors(1)
• M Spherical Equivalent
• J0 (-Cyl/2)cos(2axis)
• J45 (-Cyl/2)sin(2axis)

(1)Thibos LN, Wheeler W, Horner DG. Power
vectors an application of Fourier analysis to
the description and statistical analysis of
refractive error. Optom Vis Sci 199774367-375.
9
Results

• The mean time between the keratoplasty and the
  wavefront examinations was 5.924.29 years (range
  1 to 15 years)
• The Zywave aberrometer was unable to capture the
  images in 3 eyes and the LADARWave in one of them

10
Results
Cycloplegic refraction vs Aberrometer derived
refraction
Both aberrometers showed similar spherical
equivalent values when compared with the
cycloplegic refraction. Statistical significant
differences were noted with the Zywave sphere
measurements and with both aberrometers cylinder
measurements (plt0.05)
11
Results
Manifest refraction vs Aberrometer derived
refraction
When compared with the manifest refraction just
LADARWave showed similar spherical equivalent
values. Statistical significant differences were
noted with both aberrometers sphere and cylinder
measurements (plt0.05)
12
Results

• Both wavefront devices derived refractions were
  highly correlated to clinical cycloplegic and
  manifest M, J0 and J45 components as will be
  shown in the next slides
• However these correlations tended to be worst
  regarding the cylinder power vector coordinates
  (J0 and J45)

13
Cycloplegic vs Wavefront (M)

• Pearson correlation
• LADARWave 0.990
• Zywave 0.989

14
Cycloplegic vs Wavefront (J0)

• Pearson correlation
• LADARWave 0.961
• Zywave 0.934

15
Cycloplegic vs Wavefront (J45)

• Pearson correlation
• LADARWave 0.904
• Zywave 0.935

16
Manifest vs Wavefront (M)

• Pearson correlation
• LADARWave 0.963
• Zywave 0.959

17
Manifest vs Wavefront (J0)

• Pearson correlation
• LADARWave 0.949
• Zywave 0.951

18
Manifest vs Wavefront (J45)

• Pearson correlation
• LADARWave 0.917
• Zywave 0.915

19
Results
Mean values of total HOA, 3rd and 4th HOA
(6.00mm pupil)

• No statistically significant discrepancies in HOA
  measurements between the two Hartmann-Shack
  devices were observed.
• Trifoil aberrations were dominant when compared
  to coma or spherical aberrations in post-PKP eyes.

20
Conclusions

• This study demonstrated that both wavefront
  devices derived refraction were highly correlated
  to clinical measurements
• Zywave showed more discrepancies when compared
  with both cycloplegic and manifest refraction
• These discrepancies should be taken into account
  while performing customized ablation in post PKP
  eyes

21
Conclusions

• Technical problems preventing the centroids
  acquisition were more frequent with the Zywave
  system
• Post PKP eyes had increased values of HOA,
  specially trifoil
• The mean values for all higher-order aberrations
  components were similar between the two
  aberrometers