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In vivo macular pigment measurements: a comparison of resonance Raman spectroscopy and heterochromatic flicker photometry
  1. R E Hogg1,
  2. R S Anderson2,
  3. M R Stevenson3,
  4. M B Zlatkova2,
  5. U Chakravarthy1
  1. 1Department of Ophthalmology, Queens University Belfast, Belfast, UK
  2. 2Vision Science Research Group, School of Biomedical Sciences, University of Ulster, Coleraine, UK
  3. 3Department of Epidemiology and Public Health, Queens University Belfast
  1. Correspondence to: R E Hogg Ophthalmology and Vision Science, Queen’s University and Royal Victoria Hospitals, Belfast BT12 6BA, UK; r.e.hogg{at}qub.ac.uk

Abstract

Aim: To investigate whether two methods of measuring macular pigment—namely, heterochromatic flicker photometry (HFP) and resonance Raman spectroscopy (RRS)—yield comparable data.

Methods: Macular pigment was measured using HFP and RRS in the right eye of 107 participants aged 20–79 years. Correlations between methods were sought and regression models generated. RRS was recorded as Raman counts and HFP as macular pigment optical density (MPOD). The average of the top three of five Raman counts was compared with MPOD obtained at 0.5° eccentricity, and an integrated measure (spatial profile; MPODsp) computed from four stimulus sizes on HFP.

Results: The coefficient of variation was 12.0% for MPODsp and 13.5% for Raman counts. MPODsp exhibited significant correlations with Raman counts (r = 0.260, p = 0.012), whereas MPOD at 0.5° did not correlate significantly (r = 0.163, p = 0.118). MPODsp was not significantly correlated with age (p = 0.062), whereas MPOD at 0.5° was positively correlated (p = 0.011). Raman counts showed a significant decrease with age (p = 0.002) and were significantly lower when pupil size was smaller (p = 0.015).

Conclusions: Despite a statistically significant correlation, the correlations were weak, with those in excess of 90% of the variance between MPODsp and Raman counts remaining unexplained, meriting further research.

  • CAREDS, Carotenoids and Age Related Eye Disease Study
  • HFP, heterochromatic flicker photometry
  • LogMAR, logarithm of the minimum angle of resolution
  • MPOD, macular pigment optical density
  • MPOD0.5, macular pigment optical density measured at the 0.5°arc radius
  • MPODsp, macular pigment optical density spatial profile
  • PPS, predicted pupil size
  • RRS, resonance Raman spectroscopy

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Footnotes

  • Published Online First 6 July 2006

  • Funding: This study was funded by grants from The Health Foundation and Evi-Genoret.

  • Competing interests: None.

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