Takushi Kawamorita

Repeatability, reproducibility, and agreement characteristics of rotating Scheimpflug photography and scanning-slit corneal topography for corneal power measurement

PURPOSE: To evaluate the repeatability, reproducibility, and agreement in anterior, posterior, and in particular the total corneal power of 2 topography devices, rotating Scheimpflug photography and scanning‐slit topography. SETTING: Department of Ophthalmology and Visual Science, Kitasato University Graduate School of Medical Sciences, Sagamihara, Japan. METHODS: Seventeen eyes of 17 subjects (mean age 24.7 years ± 4.1 [SD]) were included in the study. The corneal shapes within the central 3.0 mm were measured with rotating Scheimpflug photography (Pentacam) and scanning‐slit corneal topography (Orbscan II). The within‐rater repeatability and reproducibility of 2 raters and the overall between‐instrument agreement of the measurements were evaluated using intraclass correlation coefficients (ICCs) and the Bland‐Altman method. RESULTS: The repeatability of Scheimpflug photography and scanning‐slit corneal topography was high (ICC, 0.70 to 0.99). Scheimpflug photography outperformed scanning‐slit corneal topography for anterior power, posterior power, and total corneal power. The reproducibility results were similar, with limits of agreement (LoA) consistently narrower for Scheimpflug photography. The between‐instrument agreement was moderate, with LoA around the mean value of total corneal power of 0.46 diopter ranging from 0.032 to 0.889. CONCLUSIONS: The results suggest that repeatability and reproducibility are higher in Scheimpflug photography than in scanning‐slit topography. The agreement between rotating Scheimpflug photography and scanning‐slit topography for total corneal power was moderate.

Modulation transfer function and pupil size in multifocal and monofocal intraocular lenses in vitro

PURPOSE: To investigate the relationship between pupil size and the modulation transfer function (MTF) of a multifocal intraocular lens (IOL) in vitro and to predict the visual effects in vivo. SETTING: Department of Ophthalmology and Visual Science, Kitasato University Graduate School of Medical Sciences, Kitasato, Japan. METHODS: A refractive multifocal IOL (Array SA‐40N, Allergan) and a monofocal IOL (PhacoFlex SI‐40NB, AMO) were evaluated using the OPAL Vector system and a model eye with a variable effective aperture. With effective pupil diameters of 2.1, 3.0, 3.4, 3.9, 4.6, 5.1, and 5.5 mm, the in‐focus and defocus MTFs were measured in the multifocal and monofocal IOLs. RESULTS: With increases in effective pupil diameter, the far MTF progressively decreased at all spatial frequencies. In contrast, the near MTF began to increase at effective pupil diameter 2.1 mm, showed a peak at 3.4 mm, and decreased at diameters greater than 3.4 mm. The ratio of near MTF to far MTF showed an increase with larger effective pupil diameters and at lower spatial frequencies. CONCLUSIONS: With a zonal progressive multifocal IOL, the pupil size effected a trade‐off between the far and near MTFs: The near MTF increased at the expense of the far MTF at large pupil sizes (effective pupil diameter >3.4 mm). To enhance near vision with a multifocal IOL, the desirable effective pupil diameter should be 3.4 mm or larger.

Repeatability and Reproducibility of Corneal Curvature Measurements Using the Pentacam and Keratron Topography Systems

PURPOSE To compare the repeatability and reproducibility of corneal curvature measurements using the Pentacam eye scanner (Oculus Optikgeräte GmbH) and Keratron corneal topographer (Optikon 2000 SpA). METHODS Axial topography maps were used to acquire measurements. Twenty-six eyes of 26 healthy patients were measured to determine repeatability and reproducibility. Another 10 eyes of 10 healthy patients were included in a parallel study. Three measurements per eye were performed. Repeatability was assessed via the coefficient of variation. Reproducibility was assessed using Bland-Altman plots. Linear correlations were used to determine the agreement between devices. A P value < .05 was considered statistically significant. RESULTS The majority of coefficient of variations for both devices were within 1%. The coefficient of variation of the Pentacam was higher in the superior cornea (P < .01). The mean difference (95% limits of agreement) in the flattest meridian between examiners was -0.03 +/- 0.27 diopters (D) (range: -0.56 to +0.49 D) for the Pentacam and -0.08 +/- 0.21 D (range: -0.50 to +0.33 D) for the Keratron. The mean difference (95% limits of agreement) in the steepest meridian was -0.10 +/- 0.26 D (range: -0.60 to +0.41 D) for the Pentacam and -0.11 +/-0.22 D (range: -0.53 to +0.31 D) for the Keratron. The mean axial power for the central 3.0 mm of the Pentacam was statistically significantly lower than that of the Keratron (P < .01). CONCLUSIONS Although statistically significant differences were noted, both devices provided repeatable and reproducible corneal measurements centrally. Pentacam repeatability outcomes indicate that superior corneal measurements should be interpreted with caution.

Interferometry in the evaluation of precorneal tear film thickness in dry eye.

PURPOSE To compare tear film thickness between normal subjects and aqueous tear deficiency dry eye patients by tear interferometry. DESIGN Prospective case-control study. METHODS Central precorneal tear film thickness was measured noninvasively using an interference thin-film thickness measurement device (Quore MSPA1100; Mamiya-OP). Tear film thickness of 14 eyes from 14 normal subjects and of 28 eyes from 28 aqueous tear deficiency dry eye patients were compared along with noninvasively measured tear meniscus height, DR-1 (Kowa) dry eye severity grading, fluorescein and rose bengal staining scores, tear film break-up time, and Schirmer test results. Among dry eye patients, 13 eyes underwent punctal occlusion, and tear film thickness was compared before and after the surgery. RESULTS Tear film was significantly thinner in dry eye patients (2.0 ± 1.5 μm) than normal subjects (6.0 ± 2.4 μm; P < .0001). Tear film thickness showed good correlation with other dry eye examinations. After punctal occlusion, tear film thickness increased significantly from 1.7 ± 1.5 μm to 4.9 ± 2.8 μm (P = .001) with the improvement of tear meniscus height, fluorescein and rose bengal staining scores, tear film break-up time, and Schirmer test values. CONCLUSIONS Interferometric tear film thickness measurement revealed impaired precorneal tear film formation in aqueous tear deficiency dry eyes and was useful for showing the reconstruction of tear film after punctal occlusion surgery. Interferometry of precorneal tear film may be helpful for the evaluation of aqueous tear deficiency in conjunction with other dry eye examinations.

Effect of axis orientation on visual performance in astigmatic eyes

PURPOSE: To determine the effect of axis orientation on visual performance in astigmatic eyes. SETTING: Department of Ophthalmology, Kitasato University, Kanagawa, Japan. DESIGN: Investigational simulation. METHODS: Healthy volunteers with no ophthalmic disease other than refractive errors were enrolled. After cycloplegic refraction was fully corrected with a 3.0 mm artificial pupil, with‐the‐rule (WTR), against‐the‐rule (ATR), and oblique (OBL) astigmatism of 1.0 diopter (D), 2.0 D, and 3.0 D were produced using trial lenses in each subject. Distance visual acuity and reading performance with uncorrected astigmatism imposed by the trial lenses under cycloplegia were assessed. Reading performance was determined from reading acuity and maximum reading speed using the Japanese version of the Minnesota Low Vision Reading Test acuity charts. RESULTS: Distance visual acuity and reading performance in the 38 volunteers decreased significantly with increasing astigmatism (P<.001, analysis of variance). Distance visual acuity, reading acuity, and maximum reading speed with uncorrected astigmatism were significantly affected by axis orientation at each diopter of astigmatism (P<.05, 1.0 D and 2.0 D; P<.001, 3.0 D). All parameters showed significantly better values in eyes with WTR or ATR astigmatism than in eyes with OBL astigmatism at each diopter (P<.05); there were no significant differences between eyes with WTR astigmatism and eyes with ATR astigmatism. CONCLUSIONS: Eyes with OBL astigmatism had significantly lower visual performance than eyes with WTR or ATR astigmatism. Correcting the preexisting astigmatism to acquire excellent visual outcomes may be necessary, especially in eyes with OBL astigmatism. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Changes in vaulting and the effect on refraction after phakic posterior chamber intraocular lens implantation.

PURPOSE: To assess the changes in vaulting over time after implantable Collamer lens (ICL) implantation and the effect of vaulting on refraction. SETTING: Department of Ophthalmology, Kitasato University, Kanagawa, Japan. METHODS: This retrospective study evaluated eyes of consecutive patients having ICL implantation. The postoperative changes in vaulting between the ICL and the crystalline at 1, 3, and 6 months and 1 year were quantitatively assessed. The relationship between the vaulting and refractive outcomes at 1 year was also evaluated. RESULTS: Seventy‐five eyes of 47 patients were evaluated. The mean vaulting was 0.61 mm ± 0.26 (SD), 0.59 ± 0.25 mm, 0.54 ± 0.25 mm, and 0.53 ± 0.24 mm at 1 month, 3 months, 6 months, and 1 year, respectively. The mean refractive error (difference between attempted and achieved manifest spherical equivalent refraction) was 0.01 ± 0.42 diopter (D) 1 year postoperatively. There was no significant association between the amount of vaulting and the refractive error (r = 0.19, P = .11). CONCLUSIONS: Vaulting of the ICL over the crystalline lens decreased slightly with time, likely as a result of pupil movement, age‐related increases in crystalline lens thickness, and the fixed position of the ICL haptics. The vaulting did not significantly affect refractive outcomes, suggesting that a precise effective lens position leads to higher predictability, largely as a result of the narrow fixated location of the ICL between the back surface of the iris and the ciliary sulcus.

Optical performance in rezoom and array multifocal intraocular lenses in vitro.

PURPOSE To investigate the modulation transfer function (MTF) of two refractive multifocal intraocular lenses (IOLs). METHODS The ReZoom and Array (AMO) multifocal IOLs were evaluated using the OPAL Vector system (Image Science Ltd) and a model eye with a variable aperture (2.1 to 5.5 mm). Modulation transfer functions were evaluated at distant, near, and intermediate (-1.50 diopter defocus) focus lengths. RESULTS The ReZoom IOL distant focus MTF for a 5.1-mm effective diameter was higher than that of the Array IOL. At intermediate distance, the ReZoom lens showed a slight increase compared with the Array. The near focus MTF for the ReZoom IOL began to increase at an effective diameter of 2.1 mm and remained constant for diameters > 3.45 mm. CONCLUSIONS The ReZoom IOL gave better image quality than the Array, particularly at distant focus. To enhance near vision with the ReZoom lens, the desirable real pupil diameter should be at least 3.45 mm.

Quantitative measurement of ocular dominance using binocular rivalry induced by retinometers

PURPOSE: To develop a new method using binocular rivalry and retinometers to quantitatively examine ocular dominance and to investigate the magnitude of ocular dominance in cataract patients preoperatively and postoperatively. SETTING: Eye Clinic, Kitasato University School of Medicine Hospital, Sagamihara, Kanagawa, Japan. METHODS: The duration of exclusive visibility of the dominant and nondominant eye target in binocular rivalry were measured in 60 healthy volunteers (study 1) and preoperatively and postoperatively in 10 cataract patients (study 2). Rivalry targets were presented directly to the retina of each eye using 2 retinometers. Subjects reported the exclusive visibility of 1 eye target, and the total duration of exclusive visibility for each eye in dominant and nondominant eye trials was evaluated. RESULTS: In study 1, the magnitude of ocular dominance was quantitatively assessed with 4 grades based on differences in total duration of exclusive visibility between dominant and nondominant eyes. In study 2, magnitude of ocular dominance could be evaluated in all cataract patients regardless of refractive and cataract conditions. Magnitude of ocular dominance displayed significant correlations between preoperative and postoperative conditions (simple regression, P<.001). CONCLUSIONS: Ocular dominance can be quantitatively evaluated using this new method based on binocular rivalry and retinometers, particularly in cataract patients. Magnitude of ocular dominance may indicate preoperatively whether a patient with cataracts will have sufficient ocular dominance to adjust to monovision correction.

Effect of incomplete blinking on tear film stability.

Purpose The purpose of this study is to assess changes in tear film stability caused by incomplete blinking. Methods Eleven subjects (mean age, 21.3 years) participated in this study. All subjects had a visual acuity of 20/20 or better and normal ocular health. The subjects were asked to play a game for 60 min on a personal computer as part of a visual display terminal (VDT) experiment. Each subject’s blinking was observed by a Web camera that was attached to the top of the display. Every 15 min, the VDT experiment was interrupted for measurement. An RT-7000 (Tomey Co., Ltd., Nagoya, Japan) was used to measure ring breakup time as a parameter of tear film stability. An OPD-Scan II ARK-10000 (NIDEK Co., Ltd., Aichi, Japan) was used to measure corneal aberrations. Results Although the total blink rate changed very little, the complete and incomplete blink rates fluctuated during the VDT experiment. Both types were plotted along symmetrical cubic approximation curves. Noninvasive (ring) breakup time at 30 min (4.33 ± 2.57 s) was significantly shorter (p < 0.01) than that at baseline before the VDT experiment (8.62 ± 1.54 s). After 30 min, the incomplete blink rate began decreasing (fewer incomplete blinks), whereas the complete blink rate began increasing. Ring breakup time increased (improved) after 45 min; however, the incomplete blink rate began to increase again after approximately 50 min. Conclusions Even if the total blink rate decreases, the tear film remains stable so long as almost all blinks are complete. The incomplete blinking contributes to tear film instability and is variable with prolonged VDT exposure. Our study indicated that the tear film stability was determined by blinking quality, and the predominance of blinking type relates to tear film stability.

Effect of pupil size on uncorrected visual acuity in astigmatic eyes

Aim To determine the effects of pupil size on uncorrected visual acuity (UCVA) in astigmatic eyes. Methods The authors examined 20 normal eyes of 20 healthy volunteers (age 26.7±4.9 years (mean±SD); 8 men, 12 women). After fully correcting cycloplegic refraction, the authors created with-the-rule and against-the-rule astigmatism of 1, 2, and 3 dioptres (D) in each eye, and then assessed UCVA using artificial pupils (1 to 5 mm) in these astigmatic eyes. Measurements were performed three times, and the mean value was used for statistical analysis. Results In eyes with with-the-rule astigmatism of 1, 2 and 3 D, logMAR UCVA was 0.04±0.08, 0.09±0.09 and 0.16±0.16 for 1 mm pupils, −0.01±0.09, 0.12±0.15 and 0.33±0.24 for 2 mm pupils, 0.02±0.09, 0.20±0.19 and 0.46±0.30 for 3 mm pupils, 0.02±0.08, 0.24±0.20 and 0.48±0.21 for 4 mm pupils, and 0.08±0.10, 0.33±0.18 and 0.53±0.22 for 5 mm pupils, respectively. The variance of the data was statistically significant (p=0.03 for 1 D, p<0.001 for 2 D, p<0.001 for 3 D, analysis of variance). Similar results were obtained in eyes with against-the-rule astigmatism. Conclusions Both the amount of astigmatism and the pupil size can affect UCVA in astigmatic eyes. It is suggested that not only the amount of astigmatism but also the pupil size should be taken into consideration for acquiring better visual performance in astigmatic eyes.