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Lens opacity and refractive influences on the measurement of retinal vascular fractal dimension
Author(s) -
Li Haitao,
Mitchell Paul,
Liew Gerald,
Rochtchina Elena,
Kifley Annette,
Wong Tien Y.,
Hsu Wynne,
Lee Mong L.,
Zhang Yong P.,
Wang Jie J.
Publication year - 2010
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2010.01975.x
Subject(s) - ophthalmology , opacity , retinal , medicine , refraction , magnification , confounding , dioptre , lens (geology) , subjective refraction , emmetropia , optometry , refractive error , optics , visual acuity , physics
Acta Ophthalmol. 2010: 88: e234–e240 Abstract. Purpose: To examine the influence of lens opacity and refraction on the measurement of retinal vascular fractal dimension ( Df ). Methods: Optic disc photographs (right eyes) of 3654 baseline Blue Mountains Eye Study participants (aged 49–97 ) were digitized. Retinal vascular D f was quantified using a computer‐based program. Summated severity scores for nuclear, cortical and posterior subcapsular (PSC) cataract were assessed from lens photographs. Refraction data were converted to spherical equivalent refraction (SER), as sum spherical plus 0.5 cylinder power. Axial length was measured at 10‐year follow‐up examinations using an IOL master. Results: Mean D f of the retinal vasculature was 1.444 ± 0.023 for 2859 eligible participants. Increasing lens opacity scores were associated with significant reduction in D f (β = −0.0030, p < 0.0001). Both cortical and PSC cataract involving central lens area were associated with reduced D f , after controlling for confounding factors (p trend ≤ 0.0105). Increasing myopia severity was associated with reduced D f after adjusting for lens opacity scores and other confounders (p trend < 0.0001). The slope of D f decrease per SER reduction was 0.0040 in eyes with SER ≤ −4D, compared to −0.0016 in eyes with SER > −4D. For axial length quintiles, there were no significant differences in mean D f in all groups except a reduction in the fifth quintile (axial length ≥24.15 mm) (all p < 0.05). Conclusion: Ocular media opacity independently influenced retinal vascular D f measurement, but we found no evidence supporting any refractive axial magnification effect on this measure. Myopic refraction ≤−4D was associated with a reduction in D f , suggesting rarefaction of retinal vasculature associated with high myopia.