Biomedical subjects

Mieko Nakatsuka

Publications and source records attributed to Mieko Nakatsuka.

3 recordsLinked to original sources

PubMed2006

Effect of static visual acuity on dynamic visual acuity: a pilot study.

The aim of this pilot study was to evaluate whether dynamic visual acuity changes with or without refractive correction. 42 healthy enrolled subjects with normal vision were divided into two age-matched groups. In Group A, dynamic visual acuity was measured first with the refractive error fully corrected and then without. In Group B, dynamic visual acuity measurements were taken in the reverse order of that performed by Group A. The measurements were binocularly performed five times using free-head viewing after dynamic visual acuity values were stable. Significant changes in dynamic visual acuity (static visual acuity 20/20 vs 12/20) were observed in both Group A (171.6 +/- 36.0 deg./sec. vs 151.8 +/- 39.6 deg./sec., Wilcoxon test, p < .001) and Group B (169.8 +/- 30.0 deg./sec. vs 151.2 +/- 36.0 deg./sec., Wilcoxon test, p < .001). The interaction was significant (F1.20 = 8.12, p = .009). These results indicated that refractive correction affected dynamic visual acuity.

Adult↗

PubMed2003

Accommodation obtained per 1.0 mm forward movement of a posterior chamber intraocular lens.

PURPOSE: To clarify the amount of accommodation per 1.0 mm forward movement of a posterior chamber intraocular lens (IOL). SETTING: 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.

Accommodation, Ocular↗

PubMed2002

[A study on cases of good apparent accommodation using an all-distance visual acuity chart and corneal shape analysis].

PURPOSE: As a part of an attempt to elucidate the mechanism of apparent accommodation, an evaluation was made of patients with good apparent accommodation using an all-distance visual acuity chart and corneal shape analysis. MATERIALS AND METHODS: The study was performed on 6 patients (7 eyes) in a good apparent accommodation group and 13 patients (15 eyes) in a poor apparent accommodation group. These were selected from patients who had undergone normal small-incision ultrasonic phacoemulsification and posterior chamber type single focus intraocular lens implantation. In these patients, all-distance visual acuity was measured using an AS-15(Kowa Co., Ltd.), and corneal shape analysis was performed using Orbscan (Orbtek Inc.). RESULTS: In all-distance visual acuity, gentle decline from far to near was noted in the poor apparent accommodation group, and the degree of decline was lower in the good apparent accommodation group. Also, a two-peak pattern, showing decline at first and then an increase, was observed in some of the cases. In corneal shape analysis, there was no specific pattern in the good apparent accommodation group. However, the difference between maximum refractive power and minimum refractive power of cornea in the ranges of 3, 5, and 7 mm in total optical power (TOP) was significantly higher in the good apparent accommodation group compared with the poor apparent accommodation group (TOP 3 mm: p = 0.0233, TOP 5 mm: p = 0.0306, TOP 7 mm: p = 0.0035). CONCLUSION: In the present study, there were three patterns in all-distance visual acuity in the good apparent accommodation group, showing a two-peak pattern, a flat pattern, and a gentle decline, and the pattern of gentle decline was observed more often than the other patterns. The results of the study also suggest that the gradient of corneal refractive power may be related to apparent accommodation.

Accommodation, Ocular↗