Yasuo Sakamoto

The Multi-Purpose Camera: A New Anterior Eye Segment Analysis System

A new device for the analysis of the anterior eye segment was developed. With this device, a Scheimpflug slit image and a retroillumination image can be taken separately using a CCD camera. The quality of the images obtained was satisfactory enough for analysis. The data obtained were stored and analyzed on an almost real-time level using an on-line computer. The menu for the data analysis provided for this device includes multilinear densitometry, with planimetry, area densitometry, measurement of anterior chamber depth and thickness of lens layers, determination of chamber angle and positioning of implanted intraocular lenses, and measurement of opaque areas in the retroillumination image.

Measurement of postoperative intraocular lens tilting and decentration using Scheimpflug images

ABSTRACT A three‐dimensional, in vivo method for determining the position of implanted intraocular lenses (IOLs) using an image‐processing technique has been developed. Two images of the anterior segment of the eye with an implanted IOL were photographed with a Scheimpflug camera at slitlamp angles of 90 degrees and 180 degrees. After geometrical correction, the contours of the original images were enhanced using binarization and curve‐fitting techniques. These images afforded calculation of the angle of tilt of the IOL optic axis relative to a standard reference line which connected the center of anterior corneal surface curvature with the geometrical center of the pupil. The extent and direction of IOL decentration could also be shown. The IOL image in the posterior chamber was expressed as a wire‐frame figure. This method provides several kinds of biometry in pseudophakic eyes.

Reproducibility of data obtained by a newly developed anterior eye segment analysis system, EAS-1000.

The reproducibility of data obtained from the recently developed anterior eye segment analysis system (EAS-1000) was evaluated. 40 normal eyes and 62 cataractous eyes were examined at Kanazawa Medical University Hospital or Yayoi Hospital. The radius of the corneal curvature, the corneal thickness, anterior chamber depth, whole lens thickness, anterior chamber angle and the scattering light intensity were all observed on a slit section of the lens, and the intrapupillary area of the cataractous shadow was measured from a retroillumination image. The measurements were made twice at an interval of 14.2 days. There were no significant differences between the data of the 1st and 2nd examination in either place.

Efficacy of α-Lipoic Acid Against Diabetic Cataract in Rat

Purposeα-Lipoic acid (LA) is well known as a powerful antioxidant. The efficacy of dihydrolipoate-LA for oral administration against streptozotocin (STZ)-induced diabetic cataract in rat was investigated.MethodsRats were divided into three groups, control, diabetes mellitus (DM), and DM treated with LA (DM+LA). Diabetes was induced by intravenous injection of 50 mg/kg STZ. DM+LA rats were fed 30 mg/rat per day LA in their diet. Lens changes were assessed using Scheimpflug images (EAS-1000) and by measuring light-scattering intensity.ResultsIncrease in lens light scattering was less (P < 0.05) in DM+LA rats than in DM rats 5 weeks after induction of diabetes. DM rats had the highest and control rats the lowest blood glucose levels at every measurement point up to 111 days (P < 0.05).ConclusionLA treatment delayed development and progression of cataract in rats with streptozotocin-induced diabetes. Jpn J Ophthalmol 2007;51:10–13

Accuracy of Biometrical Data Obtained from the NIDEK EAS-1000

The accuracy of biometrical data obtained from Scheimpflug images through an Anterior Eye Segment Analysis System, EAS-1000, was examined using phantom eyes and eyes with implanted IOLs. Phantom eyes

UV-B exposure to the eye depending on solar altitude

Purpose:To assess the validity of the solar ultraviolet index (UVI) as a determiner of eye risk under different conditions of facial profiles and orientation, and reflected light. Methods:Ocular UV radiation (UVR) exposure was measured as a function of the time of the day (solar altitude) using a two-dummy-type mannequin dosimetry system with embedded UVR (260-310 nm) sensors, in September and November in Kanazawa, Japan, on a motorized sun-tracking mount with one dummy face directed toward the sun and the other away from the sun. Results:A bimodal distribution of UV-B exposure was found in September for the face directed toward the sun, which differed dramatically from the pattern of ambient UVR exposure and measurements taken on the top of the head and those for the eye taken later in the year. Although the overall level was lower, a higher solar altitude is associated with higher UVR exposure in the condition facing away from the sun. Conclusions:The UVI is based on ambient solar radiation on an unobstructed horizontal plane similar to our measures taken on the top of the head, which differed so much from our measures of ocular exposure that UVI as a determiner of eye risk is deemed invalid. The use of the UVI as an indicator for the need for eye protection can be seriously misleading. Doctors should caution patients with regard to this problem, and eye protection may be warranted throughout the year.

An Index for Human Lens Transparency Related to Age and Lens Layer: Comparison between Normal Volunteers and Diabetic Patients with Still Clear Lenses

Objective: The light scattering intensity of normal, clear lenses varies with age and with the localization within the lens. Realizing the biometry of single lens areas together with their relevant light scattering intensity one should be able to calculate an index to express the lens transparency properties of normal human lenses in dependence on age. Performing the same procedure in cases of diabetic patients with still clear lenses it should become possible to obtain an index for the lens transparency properties of lenses under the ‘risk factor’ diabetes. Methods: 748 eyes with transparent lenses in 383 healthy individuals and 134 eyes with clear lenses in 70 subjects with diabetes were examined. Scheimpflug slit images of the lens were documented by a Nidek EAS-1000 instrument. Biometry for measuring the distance of the single lens layers from the anterior capsule and densitometry for determining the light scattering intensity of six defined lens layers along the (theoretical) optical axis were performed. The index of the lens transparency properties was calculated using the light scattering intensity of a defined lens layer and its distance from the anterior capsule. Results: Lens thickness and light scattering intensities increased linearly with increasing age in the normal population as well as in the diabetic patients. The densitogram pattern of the light scattering intensities in the defined representative six points was similar in both populations, but in the diabetic group the lens thickness was larger and the light scattering intensities were higher at all ages. Conclusion: The index of lens transparency properties calculated with the light scattering intensities of a certain lens area and its distance from the anterior capsule is a useful measure of lens clarity in dependence on age. ‘Clear’ lenses of the diabetic population show significantly higher indices for the lens transparency properties in all age groups.

Quantitative Evaluation of Nuclear Cataract Using Image Analysis

To quantitatively evaluate nuclear lens opacification, we applied image analysis techniques. Utilizing a newly developed anterior eye segment analysis system, Scheimpflug slit images were taken in 65 eyes with transparent lenses and 31 eyes with nuclear cataract. In transparent lenses, scattering light intensity of the anterior fetal nucleus (AFN) was equal to or less than that of the posterior fetal nucleus (PFN). In eyes with nuclear cataract, scattering light intensity of the AFN was higher than that of the PFN. Utilizing this phenomenon, nuclear opacification was evaluated by the difference of scattering light intensity between the AFN and PFN (delta i value). The methodology applied in this investigation provides precise grading of nuclear cataract and progression thereof.

Quantitative Chamber Angle Measurement Utilizing Image-Processing Techniques

An image-processing technique was applied to the measurement of the anterior chamber angle. The anterior eye segment was documented by a new instrument, named anterior eye segment analysis system for biometry of the anterior eye segment. The approximated curve of the corneal posterior curvature and the line tangent to the anterior surface of the iris were calculated as the anterior chamber angle. The mean error of the reproducibility of repeated measurements for the same image was 1.6 +/- 0.81% and that of 3 images of the same eye which were taken at 3 different times was within 5.2%.

Effectiveness of eyeglasses for protection against ultraviolet rays

PURPOSE The relationship between eyeglass size and protection of the eye surface from the effects of solar ultraviolet (UV) rays was investigated. METHODS Solar UV rays irradiating the eye surface were measured on a mannequin which modeled the standard facial bone structure of a Japanese female. UV sensor chips (photo-sensitivity: 260-400 nm) were attached to the ocular surface of the lid fissure. UV measurement was done from 12:00 to 15:00 on a sunny day in March. UV intensity was measured under the following conditions: 1) with or without eyeglasses, 2) wearing sunglasses with side protectors, and 3) wearing a cap with a 7 cm brim. Eyeglasses of four frame sizes (width: 48-57 mm) were put on the mannequin. All lenses were made of plastic and coated so as to be impervious to rays shorter than 400 nm. The refractive power was 0 diopters. At the same time, UV irradiation intensity from all directions (excluding from the earth direction) was measured using a polyhedron type UV sensor with 25 sensor chips. RESULTS Except for eyeglasses with the smallest frame size, eyeglasses effectively reduced UV exposure to sunlight from the upper front direction. However, protection against rays from the upper temporal direction was extremely poor. Sunlight from the upper back was reflected by the posterior surface of the eyeglasses and reached the eye surface. CONCLUSION The efficacy of eyeglasses against UV depends on their size. The shape of the eyeglasses and reflection from the posterior lens surface are also of great importance. Small eyeglasses do not offer ideal UV protection for the Japanese face shape.