Non-invasive phakometric measurement of corneal and crystalline lens alignment in human eyes

Mark C.M. Dunne*, Leon N. Davies, Edward A.H. Mallen, Thomas Kirschkamp, Jean-Cyriaque Barry

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

We describe a non-invasive phakometric method for determining corneal axis rotation relative to the visual axis (β) together with crystalline lens axis tilt (α) and decentration (d) relative to the corneal axis. This does not require corneal contact A-scan ultrasonography for the measurement of intraocular surface separations. Theoretical inherent errors of the method, evaluated by ray tracing through schematic eyes incorporating the full range of human ocular component variations, were found to be larger than the measurement errors (β < 0.67°, α < 0.72° and d < 0.08 mm) observed in nine human eyes with known ocular component dimensions. Intersubject variations (mean ± S.D.: β = 6.2 ± 3.4° temporal, α = 0.2 ± 1.8° temporal and d = 0.1 ± 0.1 mm temporal) and repeatability (1.96 × S.D. of difference between repeat readings: β ± 2.0°, α ± 1.8° and d ± 0.2 mm) were studied by measuring the left eyes of 45 subjects (aged 18-42 years, 29 females and 16 males, 15 Caucasians, 29 Indian Asians, one African, refractive error range -7.25 to +1.25 D mean spherical equivalent) on two occasions. © 2005 The College of Optometrists.

Original languageEnglish
Pages (from-to)143-152
Number of pages10
JournalOphthalmic and Physiological Optics
Volume25
Issue number2
DOIs
Publication statusPublished - 2005

Keywords

  • ocular alignment
  • ocular components
  • phakometry

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