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Yoshiaki Nawa

Publications and source records attributed to Yoshiaki Nawa.

15 recordsLinked to original sources
PubMed2006

Effect of total higher-order aberrations on accommodation in pseudophakic eyes.

PURPOSE: To analyze the effect of total higher-order aberrations (HOAs) on the range of accommodation in pseudophakic eyes and the size of near-vision optotypes. SETTING: Department of Ophthalmology, Nara Medical University, Nara, Japan. METHODS: The study comprised 30 patients (44 eyes) who were diagnosed with cataract at Nara University of Medical Science Hospital and Municipal Oyodo Hospital. Inclusion criteria included no other eye disorder and a best corrected distance acuity of 20/20 or better 1 month after cataract surgery. All patients had small-incision phacoemulsification followed by in-the-bag implantation of a monofocal intraocular lens (SA60AT, Alcon). All incisions were self-sealing. Accommodation in pseudophakic eyes was measured by the lens-loading method in an examination room under constant illumination. Ocular HOAs were measured using the KR-9000PW Hartmann-Shack wavefront analyzer (Topcon). RESULTS: The mean patient age was 75.8 years +/- 5.4 (SD) (range 64 to 83 years). The Pearson correlation coefficient (r) showed a significant positive correlation between the range of accommodation and Z7 (vertical coma) for a 4.0 mm pupil using the 1.0 near-vision optotype. There was a significant negative correlation between the range of accommodation and Z12 (spherical aberration) for a 4.0 mm pupil using the 1.0 near-vision optotype (r = .311, P = .040 for Z7;r = -.365, P = .015 for Z12). No other parameter was significantly correlated with the range of accommodation. CONCLUSIONS: Measurement of accommodation in pseudophakic eyes by the lens-loading method using the 1.0 near-vision optotype showed that eyes with larger vertical coma aberrations achieved a larger range of accommodation. In contrast, eyes with larger spherical aberrations had smaller amounts of accommodation. The size of the near-vision optotype may affect accommodation analysis in pseudophakic eyes.

Accommodation, Ocular↗
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↗
PubMed2005

Relationship between the retinal thickness of the macula and the difference in axial length.

PURPOSE: The purpose of this study was to evaluate the relationship between the retinal thickness of the macula and the difference in axial length with A-scan ultrasonography (UD-6000) and partial coherence interferometry (IOLMaster). METHODS: In 38 eyes of 26 patients with macular edema (ME), we measured axial length using both instruments and the retinal thickness of the macula using optical coherence tomography (OCT). To compare the difference in axial length between both methods, the Wilcoxon signed-ranks test was used. In addition, the relationship between macula thickness and axial length difference was analyzed by Spearman's correlation coefficient. RESULTS: There was a significant difference between axial-length measurements (p<0.001). In addition, the retinal thickness of the macula and the difference in axial-length measurements were positively correlated (correlation coefficient = 0.55, p=0.003). CONCLUSIONS: The difference in axial length obtained by both methods was considered to be the difference in optical and acoustic reflection site. This study may suggest that IOLMaster is sufficient for measuring axial length in eyes with macular edema and reducing postoperative refractive errors.

Biometry↗
PubMed2005

Photoreceptor cells from mouse ES cells by co-culture with chick embryonic retina.

Degeneration of photoreceptors is a consistent and common endpoint in retinal diseases. Herein, we report the efficient induction of photoreceptor-like cells from mouse embryonic stem (ES) cells using chick embryonic retina tissue. Undifferentiated mouse ES cells were initially cultured in a preferential condition into a neural lineage, and ES cells were then co-cultured with chick embryonic day 6 (E6) retina tissues. After a 10-day co-culture, approximately 20% of the mouse ES derivatives became immuno-positive for rhodopsin. RT-PCR analysis demonstrated expression of the transcription factor crx and a distinct increase of rod photoreceptor-specific markers, IRBP and recoverin, after the start of the co-culture. These results indicate that co-culture of ES cells with chick embryonic retina tissue is a useful and efficient method for the induction of photoreceptor-like cells.

Animals↗
PubMed2005

Evaluation of apparent ectasia of the posterior surface of the cornea after keratorefractive surgery.

PURPOSE: To calculate the apparent posterior corneal changes after keratorefractive surgery and reevaluate corneal ectasia displayed by Orbscan (Orbtek). SETTING: Department of Ophthalmology, Nara Medical University, Nara, Japan. METHODS: Postoperative:preoperative magnification ratio of the posterior surface of the cornea was calculated in a theoretical eye model. RESULTS: Assuming the preoperative corneal thickness is 600.00 microm, the preoperative refractive power of the anterior corneal surface is 48.0 diopters (D), the refractive power of the cornea is 1.376, the ablation diameter is 6.0 mm, the postoperative corneal thickness is 480.00 microm, the postoperative refractive power of the anterior corneal surface is 38.0 D, and the posterior surface of the cornea does not change postoperatively, the apparent image of the posterior surface of the cornea becomes 0.778% smaller postoperatively. If the posterior radius of curvature of the cornea is 6.2 mm, it becomes smaller by 48.24 microm. If this change directly affects the difference map, the posterior surface of the cornea moves forward by 48.24 microm. CONCLUSION: The results correspond to the amount of ectasia in previous reports. This artifact may explain the apparent ectasia detected by Orbscan.

Artifacts↗
PubMed2005

Dioptric changes in eyes with reversed intraocular lenses.

PURPOSE: To theoretically calculate refractive changes in eyes with reversed intraocular lenses (IOLs). SETTING: Nara Medical University, Nara, Japan. METHODS: With the ray-tracing method, the refractive changes in a theoretical eye model with a reversed IOL in the capsular bag were calculated. Data for 3 models, anterior biconvex (MA60AC, Alcon), posterior biconvex (MA60BM, Alcon), and convex plano (UV2565T, Menicon), were provided by the manufacturer and used in the analysis. RESULTS: Using the assumption that the axial length varied from 22 to 27 mm, the anterior-biconvex IOLs elicited small refractive changes when reversed. The posterior-biconvex IOLs elicited a significant myopic shift (up to 0.90 diopter [D]) when reversed. The convex-plano IOLs elicited a significant hyperopic shift (up to 2.01 D) when reversed. CONCLUSIONS: Anterior-biconvex IOLs with similar anterior and posterior radii of curvature will not cause large diopter surprises when reversed. High-power posterior-convex IOLs will cause significant myopic diopter surprises when reversed. Both these changes shift toward myopic if the postoperative anterior chamber depth (ACD) becomes shallow. Medium- to high-power convex-plano IOLs will cause a large hyperopic shift when reversed. This hyperopic shift decreases if the postoperative ACD becomes shallower.

Humans↗
PubMed2005

Posterior corneal surface changes after hyperopic laser in situ keratomileusis.

PURPOSE: To evaluate posterior corneal surface topographic changes after hyperopic laser in situ keratomileusis (H-LASIK) using Orbscan I (Orbtek, Inc.). SETTING: Department of Ophthalmology, Nara Medical University, Nara, Japan. METHODS: In 25 eyes of 15 patients who had H-LASIK, the posterior corneal surface was measured with slit-scanning corneal topography (Orbscan I) preoperatively and 1 year postoperatively. The center as a fit zone and calculated posterior corneal surface changes were taken at 4 points: nasal, temporal, superior, and inferior sides in the 5.0 mm diameter. The posterior corneal topographic changes were analyzed using an analysis of variance. The postoperative:preoperative magnification ratio of the posterior corneal surface was calculated in a theoretical eye model. RESULTS: When a "+" reading was defined as the forward displacement and "-" was defined as the backward displacement, the mean posterior corneal topographic changes were -2.8 microm +/- 27.9 (SD) at the nasal side, -4.5 +/- 27.8 microm at the temporal side, -3.9 +/- 20.1 microm at the superior side, and -2.3 +/- 20.1 microm at the inferior side. The posterior corneal surface between any 2 examined points showed no significant difference after H-LASIK. In addition, the hypothetical change in the posterior cornea was -8.3 microm after +3.0 diopter H-LASIK, which was approximately closer to the study results. In each side, the amount of the attempted correction was significantly correlated with the posterior corneal topographic change. CONCLUSIONS: Clinical measurement of the posterior corneal displacement after H-LASIK with Orbscan revealed a backward shift. This change corresponded to the hypothetical artifactual changes with Orbscan; that is, changes in the magnification ratio.

Adult↗
PubMed2004

Long-term observation of the refraction with a reversed-optic posterior chamber intraocular lens.

A 73-year-old man had phacoemulsification and implantation of a posterior chamber intraocular lens (PC IOL) in both eyes. In the right eye, the optic was unintentionally reversed in the bag. In the left eye, the posterior capsule was ruptured and the IOL haptics were fixated in the ciliary sulcus. The refraction in the sulcus-fixated left eye was stable from 1 month to 4 years. The right eye had a myopic shift at 1 month, with a regression of 1.50 diopters that continued for 2 years. The final IOL position in the right eye was 0.25 mm anterior to the position predicted by the SRK/T formula. It took 2 years for the refraction in the eye with the reversed-optic PC IOL to become stable. A large myopic shift and gradual regression in refraction may stem from a different wound-healing reaction than that of properly fixated IOLs.

Aged↗
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↗
PubMed2003

Evaluation of the corneal endothelium after hyperopic laser in situ keratomileusis.

PURPOSE: To evaluate corneal endothelial changes after hyperopic laser in situ keratomileusis (LASIK) considering overestimation and underestimation of the cell count measurement. SETTING: Department of Ophthalmology, Nara Medical University, Nara, Japan. METHODS: The data were from the clinical trial of the Nidek EC-5000 excimer laser for hyperopic LASIK. The mean correction was 3.59 diopters (D) +/- 1.54 (SD) (range 2.0 to 6.0 D). Using noncontact specular microscopy, the corneal endothelial changes in 25 eyes of 15 patients who had hyperopic LASIK were measured. Follow-up ranged from 6 months (n = 25) to 1 year (n = 21). The overestimation and underestimation of the corneal endothelial cell count that would occur after +5.0 D hyperopic LASIK was hypothetically calculated. RESULTS: The measured endothelial cell count per 1.0 mm(2) did not significantly decrease up to 1 year after hyperopic LASIK (preoperatively, 2508 +/- 395; at 1 year, 2814 +/- 349). The hypothetical calculation revealed that a +5.0 D hyperopic correction corresponded to a 0.1% underestimation of the corneal endothelial cell count. CONCLUSIONS: Underestimation of the corneal endothelial cell count after hyperopic LASIK was negligible. Hyperopic LASIK with the Nidek EC-5000 excimer laser did not significantly decrease corneal endothelial cells up to 1 year after surgery.

Adult↗
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↗
PubMedDate not supplied

Relationship between corneal aberrations and contrast sensitivity after hyperopic laser in situ keratomileusis.

PURPOSE: To evaluate the relationship between corneal aberrations and contrast sensitivity (CS) after hyperopic laser in situ keratomileusis (H-LASIK). METHODS: In 13 patients (13 eyes) who underwent H-LASIK, we measured CS and corneal topography preoperatively and at 1 year postoperatively. Photopic and scotopic CS values were measured at 3, 6, and 12 cycles/degree (cpd) using an MCT-8000 contrast tester. Corneal aberrations were determined from the data on corneal topography using CTView. The corneal high-order aberrations were defined as the sum of the third- and fourth-order aberrations in the 4-mm zone and the sum of the third- to sixth-order aberrations in the 6-mm-zone. RESULTS: Under scotopic conditions at 12 cpd, the changes in CS significantly correlated with changes in the corneal aberrations. Scotopic CS was significantly deteriorated by glare, but photopic CS was not significantly changed. H-LASIK induced a significant increase in corneal aberrations that positively correlated with the amount of correction, regardless of the improvement in logMAR corrected visual acuity. LogMAR corrected visual acuity did not significantly correlate with corneal aberrations. Furthermore, decentration significantly correlated with the changes in the 6-mm zone corneal aberrations. CONCLUSIONS: In eyes after H-LASIK, the changes in scotopic CS significantly correlated with those in the corneal aberrations, which might have resulted from decentration or ablation profiles in H-LASIK and a relatively small optical zone. Further studies will be needed to validate this relationship.

Adult↗