The effect of pre-adapting light intensity on dark adaptation in early age-related macular degeneration
- 418 Downloads
This study aimed to identify the pre-adapting light intensity that generated the maximum separation in the parameters of dark adaptation between participants with early age-related macular degeneration (AMD) and healthy control participants in the minimum recording time.
Cone dark adaptation was monitored in 10 participants with early AMD and 10 age-matched controls after exposure to three pre-adapting light intensities, using an achromatic annulus (12° radius) centred on the fovea. Threshold recovery data were modelled, and the time constant of cone recovery (τ), final cone threshold, and time to rod-cone-break (RCB) were determined. The diagnostic potential of these parameters at all pre-adapting intensities was evaluated by constructing receiver operating characteristic (ROC) curves.
There were significant differences between those with early AMD and healthy controls in cone τ and time to RCB (p < 0.05) at all pre-adapting ‘bleaching’ intensities. ROC curves showed that the diagnostic potential of dark adaptometry was high following exposure to all three pre-adapting intensities, generating an area under the curve in excess of 0.87 ± 0.08 for cone τ and time to RCB for all conditions.
Dark adaptation was shown to be highly diagnostic for early AMD across a range of pre-adapting light intensities, and therefore, the lower pre-adapting intensities evaluated in this study may be used to expedite dark adaptation measurement in the clinic without compromising the integrity of the data obtained. This study reinforces the suggestion that cone and rod dark adaptation are good candidate biomarkers for early AMD.
KeywordsEarly age-related macular degeneration Dark adaptation Diagnostic potential Pre-adapting light intensity Psychophysics
- 5.Brown DM, Michels M, Kaiser PK, Heier JS, Sy JP, Ianchulev T (2009) Ranibizumab versus verteporfin photodynamic therapy for neovascular age-related macular degeneration: Two-year results of the ANCHOR study. Ophthalmology 116:57.e55–65.e55Google Scholar
- 7.UN (2009) Population prospects: 2008 revision [online]. Available at: http://www.un.org/esa/population/publications/wpp2008/wpp2008_highlights.pdf. Accessed 18 July 2011
- 8.Bird AC, Bressler NM, Bressler SB, Chisholm IH, Coscas G, Davis MD, de Jong PT, Klaver CC, Klein BEK, Klein R, Mitchell P, Sarks JP, Sarks SH, Soubrane G, Taylor HR, Vingerling JR (1995) An international classification and grading system for age-related maculopathy and age-related macular degeneration. The International ARM Epidemiological Study Group. Surv Ophthalmol 39:367–374CrossRefPubMedGoogle Scholar
- 11.Sabour-Pickett S, Loughman J, Nolan JM, Stack J, Pesudovs K, Meagher KA, Beatty S (2013) Visual performance in patients with neovascular age-related macular degeneration undergoing treatment with intravitreal ranibizumab. J Ophthal 2013:268438Google Scholar
- 35.Brainard DH, Pelli DG, Robson T (2001) Display characterization. In: Hornak J (ed) The encyclopaedia of imaging science and technology, vol 18. Wiley, Hoboken, NJ, pp 172–188Google Scholar