Ken Asakawa

Effects of ocular dominance and visual input on body sway.

PurposeTo clarify the role of ocular dominance and to investigate the importance of visual acuity and restriction of the visual field for the visual stabilization of posture.MethodsThe subjects were 31 healthy volunteers ranging in age from 18 to 27 years. The sway of the center of gravity in the upright position was measured by a stabilometer. The tracings of the center of gravity obtained with the stabilometer while the subjects were standing erect for 1 min under several conditions were analyzed. The root mean square (RMS) area of body sway in each case was determined by analysis of the data. The main visual conditions were as follows: with the eyes open; with fixation of the dominant eye or of the nondominant eye; with a binocular or a monocular visual field of 10°; with a binocular or a monocular visual field of 10° and a visual acuity of 0.01; and with the eyes closed.ResultsThe main results were as follows: (1) The RMS area while fixation of the dominant eye was maintained was significantly greater than that with fixation of the nondominant eye, and (2) the RMS area showed marked differences between binocular and monocular visual fields restricted to 10°. In monocular fixation of the same visual field, the RMS area increased significantly compared with in binocular fixation.ConclusionsBinocular vision with the field restricted to 10° offered the greatest contribution to postural stability, but the nondominant eye was more concerned with postural control than the dominant eye. Jpn J Ophthalmol 2007;51:375–378

Evaluation of optic nerve head using a newly developed stereo retinal imaging technique by glaucoma specialist and non-expert-certified orthoptist.

Purpose:To evaluate the reproducibility and interexaminer consistency in analyzing the optic disc parameters using a newly fundus stereoscopic camera, and their correlation with parameters of the Heidelberg Retina Tomograph II (HRT II) was also examined. Methods:This study examined 53 eyes of 53 healthy volunteers (mean age, 21.8 y). Fifty-five eyes of 55 glaucoma patients (mean age, 59.3 y) were also involved. A Nonmyd WX retinal camera was used for stereoscopic fundus imaging. The diagnostic parameters for the optic nerve head analyses were examined under the following conditions: (1) the intraexaminer reproducibility was determined by a certified orthoptist (CO) with 1 year’s experience, with the appropriate coefficient of variation in 8 healthy eyes; and (2) the interexaminer consistency of the diagnostic parameters by both glaucoma specialist and CO was examined in 45 healthy eyes and 55 glaucomatous eyes. By subgroup analysis, the healthy eyes were classified into 2 groups based on the degree of myopia, the optic disc of glaucomatous eye was classified into 4 types: focal ischemic, generalized enlargement, myopic, and senile sclerotic, and also classified into 3 stages (early, moderate, and severe) by Hodapp-Anderson-Parrish scale. (3) The correlation of parameters common to Nonmyd WX and HRT II was examined in 18 eyes of randomly selected patients. Results:The results were as follows: (1) Mean coefficient of variation of 2.6% to 17.6%, with volume parameters considerably lower than the other parameters. (2) In both groups, a high or moderate degree of consistency was obtained (r=0.40 to 0.99; P=0.032 to <0.0001), except only the upper rim width in healthy subjects (r=0.28; P=0.137). In particular, good consistency was obtained in healthy eye with >−3 D of myopia, in glaucoma patients with the generalized type of optic disc and severe glaucomatous stage. (3) A strong correlation with HRT II was obtained only in the cup area and the disc area by both specialist and CO (r=0.75 to 0.90; P=0.0003 to <0.0001). Conclusions:Our studies indicated that most of the parameters were highly reproducible and consistent, and less difference was found between the results obtained by an experienced glaucoma specialist and a non–expert CO in patients with deep cupping and severe eye, but the examiner needs a clear understanding of the criteria for the rim and the cup.

Abnormal pupillary light reflex with chromatic pupillometry in Gaucher disease

The hallmark of neuronopathic Gaucher disease (GD) is oculomotor abnormalities, but ophthalmological assessment is difficult in uncooperative patients. Chromatic pupillometry is a quantitative method to assess the pupillary light reflex (PLR) with minimal patient cooperation. Thus, we investigated whether chromatic pupillometry could be useful for neurological evaluations in GD. In our neuronopathic GD patients, red light‐induced PLR was markedly impaired, whereas blue light‐induced PLR was relatively spared. In addition, patients with non‐neuronopathic GD showed no abnormalities. These novel findings show that chromatic pupillometry is a convenient method to detect neurological signs and monitor the course of disease in neuronopathic GD.

New approach for the glaucoma detection with pupil perimetry

Objective: To calculate the pattern deviation for identifying abnormal points of pupil perimetry, and also to evaluate the grayscale display for distinguishing glaucomatous pupil field loss (abnormal test points) from normal pupil field (normal test points). Methods: Fourteen patients ranging in age from 51 to 80 years, who had normal-tension glaucoma (6 eyes) and primary open-angle glaucoma (8 eyes) were tested. Pupil perimetry (Kowa & Hamamatsu, Japan) was used to objectively measure the visual field. Also, to obtain a subjective visual field, the analysis was performed with a Humphrey Field Analyzer (30-2, Full threshold program, Carl Zeiss Meditec, Dublin). Of the 76 test points, the 22 surrounding points and the 3 points corresponding to the blind spot are excluded; and among the remaining 51 points, the 85th percentile value of pupil perimetry was calculated. The abnormal and normal test points were recorded, and the amount of positive or negative deviation of each test point from the normal median value for the corresponding test points was determined. We also used this technique to identify the value for distinguishing glaucomatous pupil field loss from the normal pupil field. Results: This study could be improved by calculating the sensitivity and specificity of a certain cut-off value between the normative data and the glaucoma patients. The value for identifying both abnormal and normal test points was a negative deviation of −4. Based on these results, pupil perimetry gray scales were determined: white (< −3), 25% gray (from −4 to −8), 50% gray (from −9 to −13), 75% gray (from −14 to −18) and black (> −19). Glaucomatous pupil field losses were generally distinguished from the normal pupil field by use of a gray scale. Conclusion: Our studies demonstrated that, when a deviation of > −4 was regarded as an abnormal value, the detection of pupil perimetry exhibited improvement in glaucoma patients.

Effects of Age and Sex on Values Obtained by RAPDx(®) Pupillometer, and Determined the Standard Values for Detecting Relative Afferent Pupillary Defect.

Purpose To determine the effects of age and sex on the amplitude and latency scores obtained by the RAPDx® pupillometer, and to determine the standard values for detecting relative afferent pupillary defect (RAPD) in healthy subjects. Methods The study was conducted on 84 healthy subjects (52 males, 32 females), who had no ophthalmic diseases other than refractive errors with a mean age of 32 years. The amplitude and latency scores of the males were compared to that of females and also among the different age groups. The correlations between the amplitude and latency scores and age were determined. The standard values with the 90%, 95%, and 99% prediction intervals of the measured values were also calculated. Results The differences in the amplitude and latency scores between the sexes were not significant. In addition, both scores were not significantly related with age. The mean amplitude score for all subjects with prediction intervals of 90%, 95%, and 99% was 0.02 (−0.26 to 0.30, −0.32 to 0.35, and −0.42 to 0.46, respectively); the latency score was −0.02 (−0.24 to 0.20, −0.28 to 0.25, and −0.37 to 0.33, respectively). Conclusions RAPD is not present when the absolute values of the amplitude score and latency scores, measured by the RAPDx® pupillometer, are ≤ 0.2 log units. RAPD is present when either of the values are ≥ 0.5 log units. Translational Relevance Results of this study can be used for detection of RAPD in the clinic and it will be the basic data of RAPDx® pupillometer for future research.

Discovering irregular pupil light responses to chromatic stimuli using waveform shapes of pupillograms

BackgroundThe waveforms of the pupillary light reflex (PLR) can be analyzed in a diagnostic test that allows for differentiation between disorders affecting photoreceptors and disorders affecting retinal ganglion cells, using various signal processing techniques. This procedure has been used on both healthy subjects and patients with age-related macular degeneration (AMD), as a simple diagnostic procedure is required for diagnosis.ResultsThe Fourier descriptor technique is used to extract the features of PLR waveform shapes of pupillograms and their amplitudes. To detect those patients affected by AMD using the extracted features, multidimensional scaling (MDS) and clustering techniques were used to emphasize stimuli and subject differences. The detection performance of AMD using the features and the MDS technique shows only a qualitative tendency, however. To evaluate the detection performance quantitatively, a set of combined features was created to evaluate characteristics of the PLR waveform shapes in detail. Classification performance was compared across three categories (AMD patients, aged, and healthy subjects) using the Random Forest method, and weighted values were optimized using variations of the classification error rates. The results show that the error rates for healthy pupils and AMD-affected pupils were low when the value of the coefficient for a combination of PLR amplitudes and features of waveforms was optimized as 1.5. However, the error rates for patients with age-affected eyes was not low.ConclusionsA classification procedure for AMD patients has been developed using the features of PLR waveform shapes and their amplitudes. The results show that the error rates for healthy PLRs and AMD PLRs were low when the Random Forest method was used to produce the classification. The classification of pupils of patients with age-affected eyes should be carefully considered in order to produce optimum results.

New Methods for the Assessment of Accommodative Convergence

PURPOSE The authors introduced a new objective method for measuring horizontal eye movements based on the first Purkinje image with the use of infrared charge-coupled device (CCD) cameras and compared stimulus accommodative convergence to accommodation (AC/A) ratios as determined by a standard gradient method. METHODS The study included 20 patients, 5 to 9 years old, who had intermittent exotropia (10 eyes) and accommodative esotropia (10 eyes). Measurement of horizontal eye movements in millimeters (mm), based on the first Purkinje image, was obtained with a TriIRIS C9000 instrument (Hamamatsu Photonics K.K., Hamamatsu, Japan). The stimulus AC/A ratio was determined with the far gradient method. The average values of horizontal eye movements (mm) and eye deviation (Delta) (a) before and (b) after an accommodative stimulus of 3.00 diopters (D) were calculated with the following formula: horizontal eye movements (mm/D) and stimulus AC/A ratio (Delta/D) = (b - a)/3. RESULTS The average values of the horizontal eye movements and the stimulus AC/A ratio were 0.5 mm/D and 3.8 Delta/D, respectively. Correlation analysis showed a strong positive correlation between these two parameters (r = 0.92). Moreover, horizontal eye movements are directly proportional to the AC/A ratio measured with the gradient method. CONCLUSIONS The methods used in this study allow objective recordings of accommodative convergence to be obtained in many clinical situations.

Evaluation of Relative Afferent Pupillary Defect Using RAPDx Device in Patients with Optic Nerve Disease

ABSTRACT We previously reported the standard values of the amplitude and latency scores in the RAPDx device for evaluating relative afferent pupillary defect (RAPD). Here, we evaluated RAPD in patients with optic nerve disease by using these standard values. Twenty-eight patients with current or previous optic nerve disease were enrolled in this study. Additionally, the data of 84 healthy subjects from our previous report were used as control data. We measured the amplitude and latency scores using RAPDx. We then compared their mean values and the percentages of individuals with standard values within a certain range between the optic nerve disease group and healthy group. Additionally, we evaluated their correlation with visual acuity and the critical flicker fusion frequency in the optic nerve disease group. Both parameters were significantly higher in the optic nerve disease group than in the control group (p < 0.0001). The detection rate of RAPD when using the standard value of amplitude score was 75%. Additionally, both parameters showed a significant correlation with laterality-based differences in visual acuity and critical flicker fusion frequency values in the optic nerve disease group (r = 0.59–0.75, p < 0.001). The amplitude and latency scores determined using RAPDx are useful in evaluating RAPD, particularly the standard value of the amplitude score.

Histopathological Changes of Inner Retina, Optic Disc, and Optic Nerve in Rabbit with Advanced Retinitis Pigmentosa

ABSTRACT We observed the histopathological changes of retinal ganglion cells (RGCs), optic disc, and optic nerve in rabbit with advanced retinitis pigmentosa (RP). Wild-type (WT) and rhodopsin transgenic (Tg) of RP rabbits were used at age 24 months. Light and electron microscopy were used to observe the retina, optic disc, and optic nerve. RGCs were also confirmed by immunofluorescent staining with a TUJ-1 monoclonal antibody. In addition to the rod and cone degeneration, we observed the astrocyte infiltration of the optic disc due to the damage of small RGCs and nerve fibres and atrophy of small optic nerve fibres. They subsequently lead to the optic disc excavation and atrophy of the optic nerve. Consequently, our histopathological study clarified that not only the outer retina but also the inner retina, the optic disc, and the optic nerve were also affected in the late stages of RP rabbit.

Electroretinography and Pupillography in Unilateral Foveal Hypoplasia

The authors describe a 3-year-old boy with unilateral foveal hypoplasia and an absence of other ocular or systemic findings. Electroretinography obtained predominantly affecting cones. Laterality of pupil constriction to red but not to blue light was observed. The colored-light pupil response can be used to predict the retinal state.