Accommodation obtained per 1.0 mm forward movement of a posterior chamber intraocular lens.
OBJECTIVE
To clarify the amount of accommodation per 1.0 mm forward movement of a posterior chamber intraocular lens (IOL).


METHODS
Department of Ophthalmology, Nara Medical University, Nara, Japan.


METHODS
A ray-focusing equation of pseudophakic eyes was obtained with the ray-tracing method using Mathematica((R)) computer software (Wolfram). At first, it was assumed that the anterior radius of curvature of the cornea was 7.7 mm, the thickness was 0.5 mm, and the refractive index was 1.3375, and an AcrySof IOL (Alcon) was implanted in the capsular bag. Anterior and posterior radii of curvature and IOL thickness data were provided from the manufacturer and inserted in the equation. Next, the amount of accommodation per 1.0 mm of forward movement of a posterior chamber IOL was calculated under the assumption that the axial length (AL) varied from 21.0 to 27.0 mm and the implanted IOL from 30.0 to 11.0 diopters (D). The AL was fixed at 24.0 mm, and the anterior radius of curvature was varied from 6.5 to 9.5 mm and the IOL from 10.0 to 30.0 D. Similar calculations were then performed.


RESULTS
Under the assumption of a fixed corneal anterior radius of curvature of 7.7 mm, when the AL was 24.0 mm and the implanted IOL 20.0 D, 1.0 mm of forward IOL movement corresponded to 1.3 D of accommodation. When the AL was 21.0 mm and a the IOL 30.0 D, 1.0 mm of forward IOL movement corresponded to 2.3 D of accommodation. When the AL was 27.0 mm and the IOL 11.0 D, 1.0 mm of forward IOL movement corresponded to 0.8 D of accommodation. Similarly, when the anterior radius of corneal curvature was varied from 6.5 to 9.5 mm and the IOL from 10.0 to 30.0 D and the AL was fixed at 24.0 mm, 1.0 mm of forward IOL movement corresponded to 0.5 to 1.9 D of accommodation.


CONCLUSIONS
Accommodation obtained per 1.0 mm of forward IOL movement varied with AL from 0.8 D in a long eye to 2.3 D in a short eye. It also varied with the corneal power. Thus, one should not state that 1.0 mm of forward IOL movement always corresponds to a certain amount of diopters of accommodation.
Nawa
Yoshiaki
Y
Department of Ophthalmology, Nara Medical University, Kitasato, Japan. yanawa@naramed-u.ac.jp
Ueda
Tetsuo
T
Nakatsuka
Mieko
M
Tsuji
Hideyuki
H
Marutani
Hiroshi
H
Hara
Yoshiaki
Y
Uozato
Hiroshi
H
D000065:Accommodation, Ocular / Q000502:physiology*; D000180:Acrylic Resins; D003315:Cornea / Q000033:anatomy & histology; D005133:Eye Movements; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008962:Models, Theoretical; D019591:Pseudophakia / Q000503:physiopathology*
D000180:Acrylic Resins