title: MRI study of the changes in crystalline lens shape with accommodation and aging in humans.
abstract: Magnetic Resonance Imaging was used to study changes in the crystalline lens and ciliary body with accommodation and aging. Monocular images were obtained in 15 young (19-29 years) and 15 older (60-70 years) emmetropes when viewing at far (6 m) and at individual near points (14.5 to 20.9 cm) in the younger group. With accommodation, lens thickness increased (mean ± 95% CI: 0.33 ± 0.06 mm) by a similar magnitude to the decrease in anterior chamber depth (0.31 ± 0.07 mm) and equatorial diameter (0.32 ± 0.04 mm) with a decrease in the radius of curvature of the posterior lens surface (0.58 ± 0.30 mm). Anterior lens surface shape could not be determined due to the overlapping region with the iris. Ciliary ring diameter decreased (0.44 ± 0.17 mm) with no decrease in circumlental space or forward ciliary body movement. With aging, lens thickness increased (mean ± 95% CI: 0.97 ± 0.24 mm) similar in magnitude to the sum of the decrease in anterior chamber depth (0.45 ± 0.21 mm) and increase in anterior segment depth (0.52 ± 0.23 mm). Equatorial lens diameter increased (0.28 ± 0.23 mm) with no change in the posterior lens surface radius of curvature. Ciliary ring diameter decreased (0.57 ± 0.41 mm) with reduced circumlental space (0.43 ± 0.15 mm) and no forward ciliary body movement. Accommodative changes support the Helmholtz theory of accommodation including an increase in posterior lens surface curvature. Certain aspects of aging changes mimic accommodation.
authors: Abbott Medical Optics, Milpitas, CA, USA. sanjeev.k@amo.abbott.com
authors: Sanjeev
authors: S
authors: Kasthurirangan
authors: Emma L
authors: EL
authors: Markwell
authors: David A
authors: DA
authors: Atchison
authors: James M
authors: JM
authors: Pope
mesh_terms: D000065:Accommodation, Ocular; D000328:Adult; D000368:Aged; D000375:Aging; D000867:Anterior Chamber / Q000473:pathology; D000869:Anterior Eye Segment / Q000473:pathology; D016477:Artifacts; D002924:Ciliary Body / Q000473:pathology; D006801:Humans; D007908:Lens, Crystalline / Q000000981:diagnostic imaging / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D011305:Presbyopia / Q000175:diagnosis* / Q000503:physiopathology*; D014463:Ultrasonography; D055815:Young Adult