Predicting visual performance from wavefront quality metrics in cataract

1
Predicting visual performance from wavefront
quality metrics in cataract

• Konrad Pesudovs
• Katja Ullrich
• NHMRC Centre for Clinical Eye Research, Flinders
  Medical Centre Flinders University, Adelaide,
  South Australia

Financial disclosure The authors have no
financial interest
2
Background and Purpose

• Cataract affects visual performance via higher
  order aberrations and light scatter
• Wavefront aberrations occurring in cataract have
  been described in terms of the Zernike polynomial
  decomposition but neither Zernike terms nor RMS
  predict visual performance
• Other methods for organising wavefront data exist
  wavefront quality metrics
• Attempts to connect wavefront quality metrics to
  visual performance in cataract are lacking
• PURPOSE To determine which wavefront quality
  metrics are most predictive of visual performance
  in patients with cataract

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Population and Visual Performance

• Prospective, cross-sectional study of consecutive
  patients attending the Cataract Assessment Clinic
  at Flinders Medical Centre
• Inclusions all types of cataract
• Exclusions ocular comorbidity, unable to
  measure whole eye wavefront
• 206 eyes, age 73 years, 58 female
• The clinical assessment was conducted by one
  clinician-KP

• Refraction and best corrected
• High contrast visual acuity(VA)
• Pelli-Robson contrast sensitivity (PRCS)
• Pelli-Robson contrast sensitivity under glare
  (PRCSglare)

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Wavefront quality metrics

• Whole eye wavefront sensing with Wavefront
  Sciences COAS-HD
• Wavefront data exported to VOLPro software v7.25
  (Sarver and Associates) and 10th order Zernike
  expansion derived
• Zernike data exported to GetMetrics v.2.02.006
  (University of Houston, College of Optometry) by
  Thibos and Applegate for calculation of wavefront
  quality metrics

• 31 metrics of wavefront quality designed to be
  predictive of visual performance were calculated
  for the pupil plane and the image plane as per
  Thibos LN, Hong X, Bradley A, Applegate RA.
  Accuracy and precision of objective refraction
  from wavefront aberrations. J Vis
  20044(4)329-51.
• Linear Regression with SPSS Software V15.0 (SPSS
  Inc)

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Results - visual acuity and wavefront quality
metrics

• The strongest correlate of all three measures of
  visual performance was the pupil fraction metric
  PFWc

• Visual acuity and logPFWc, r2-0.37, plt0.001

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Results contrast sensitivity and wavefront
quality metrics

• The strongest correlate of each measure of
  contrast sensitivity was the pupil fraction
  metric PFWc

• Pelli-Robson contrast sensitivity and logPFWc,
  r20.39, plt0.001
• Pelli-Robson contrast sensitivity glare
  logPFWc, r20.32, plt0.001

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Pupil fraction metrics

• Pupil fraction is defined as the fraction of the
  pupil area for which the optical quality of the
  eye is good
• The critical pupil method uses an area of good
  pupil which is a concentric zone

• The red circle indicate the largest concentric
  zone for which the wavefront has reasonably good
  quality
• PFWc which is a critical pupil defined as the
  concentric area for which RMSwltcriterion (?/4)

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Conclusion

• Pupil fraction metrics are the best correlates
  with visual performance in cataract, and also
  have performed well in normal eyes

Pupil fraction metrics should be used to organise
wavefront aberration data so as to be predictive
of visual performance