Mototsugu Saishin

[The influence of corneal thickness and curvature on the difference between intraocular pressure measurements obtained with a non-contact tonometer and those with a Goldmann applanation tonometer].

Purpose: The influence of corneal thickness and curvature on the difference between intraocular pressure (IOP) measurements obtained with a non-contact tonometer (NCT) and those with a Goldmann applanation tonometer (GAT) was studied.Methods: The corneal thickness and curvature were obtained in 230 eyes of 115 subjects. The correlation between them and ratios of measurement with NCT to that with GAT ([NCT/GAT]) were examined.Results: [NCT/GAT] and corneal thickness showed a significant positive correlation (r = 0.556, P <.01), but, the correlation between [NCT/GAT] and the radius of corneal curvature was not statistically significant (r = -0.035, P =.30).Conclusion: The thick cornea has more influence on the measurement with NCT than GAT, because IOP is measured with NCT over a wider applanation area. The corneas with steeper curvature also cause higher corneal rigidity and produce more overestimation of NCT measurement, while they have stronger capillary attraction of the precorneal tear film for the GAT tip and also produce overestimation of GAT measurement. As a result, [NCT/GAT] was believed to be not influenced by the corneal curvature.

Accommodation causes with-the-rule astigmatism in emmetropes

Purpose To measure the changes in astigmatism when bilateral emmetropes accommodate. Methods Bilateral emmetropes accommodative responses were measured with an improved photorefractometer PR-1100, which measured binocular refraction in all meridians simultaneously as a fixation target was shown in natural space. Results The accommodative responses in the vertical meridian are greater than those in the horizontal meridian. In the horizontal meridian, the accommodative responses are less than the accommodative stimulus. Conclusions When accommodating the majority of bilateral emmetropes show with-the-rule astigmatism and lag of accommodation in the horizontal meridian.

Measurement by holographic interferometry of the deformation of the eye accompanying changes in intraocular pressure

T. Matsumoto is with Osaka Prefectural Technical College, Department of Mechanical Engineering, Neyagawa, Osaka, Japan. R. Nagata is with University of Osaka Prefecture, Department of Mechanical Engineering, Sakai, Osaka, Japan. The other authors are with Nara Medical University, Department of Ophthalmology, Kashihara, Nara, Japan. Received 28 May 1978. 0003-6935/78/1115-3538

Design concept and construction of a hybrid lamellar keratoprosthesis.

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The Binocular Accommodative Response in Uncorrected Ametropia

A novel hybrid lamellar keratoprosthesis composed of epithelium and stroma was developed. Artificial extracellular matrices were constituted of photocrosslinkable copolymers of N,N-dimethylacrylamide and 2-(7-coumaroxy)ethyl methacrylate; a copolymer with a high content of coumarin (A) was used as a basement membrane (BM) for the epithelium, and a copolymer with a low content (B) was used for entrapment of keratocytes. The lamellar keratoprosthesis was constructed as follows: First, a viscous buffer solution containing water-soluble copolymer (B), collagen, and keratocytes derived from rabbit was prepared. Then, a cast film of copolymer (A) was tightly placed onto the mixed solution. Ultraviolet light irradiation leading to intermolecular dimerization of coumarin groups resulted in the formation of a transparent keratocyte-entrapped hydrogel that was layered with an artificial BM. Epithelial cells were seeded on the BM. Further culturing produced the lamellar keratoprosthesis, within which both kinds of cells proliferated well. The preliminary study on two week implantation of the lamellar keratoprosthesis in rabbits provided quite promising results; adverse tissue reactions, such as corneal opacity and neovascularization, were not observed.

Lag of Accommodation

Purpose. To measure the changes in astigmatism and in the degree of anisometropia when ametropes respond to accommodative stimulation. Methods. The accommodative responses of ametropes were binocularly measured with an improved photorefractometer (PR-1100), which objectively measured binocular refraction in all meridians simultaneously, when a visual fixation target was shown in natural space at 5 and 0.5 m. Results. (1) Changes of astigmatism and anisometropia occur during binocular accommodation. (2) Changes of astigmatism mainly result from lag of accommodation in the horizontal meridian. (3) Changes of anisometropia result from the effort to focus. (4) The interaction of both eyes is suggested as the cause of the changes of astigmatism and anisometropia with accommodation. (5) In the majority of strong anisometropes (nonoverlapping group in this paper), the magnitude of anisometropia decreases (approaching isometropia) with accommodation. Conclusion. Changes in astigmatism and anisometropia can occur during accommodation, and these interactions of both eyes with accommodation may contribute to the development and maintenance of binocular function.

Measurement of Visual Axis Using a Laser Beam

There are many concepts of lag of accommodation [1,2]. In this paper it is defined as follows: regardless of how clear an image an accommodating eye can maintain of a nearer object, its retinal conjugate point does not reach that object (Fig. 1).

Determination of corneal gel dynamics

A number of axes are recognized in the eye, such as optic axis, visual axis, pupillary axis, fixation axis, and line of sight [1,2], as shown in Fig. 1. It is well known that the visual axis is the most important for ophthalmic prescription, measurement of refraction and corneal configuration and so on [3] (Fig. 2). The visual axis is defined as the two lines, one from the fixation point to the first nodal point in object space, and other from the fovea to the second nodal point in image space [1]. However, objective measurement of the visual axis is extremely difficult because it is imaginary. In clinical viewpoint, the pupillary axis and line of sight are well in use because of the simplicity of measurement. Strictly speaking, these axes differ fairly from the visual axis, and do not pass through the fovea.

PVA Hydrogel as an Artificial Vitreous Body

Abstract From observations of the dynamics of light scattered by the cornea, intensity autocorrelation func-tions that revealed two independent diffusion coefficients, D (fast) = 2.4±0.2×10–7 cm2/s and D (slow) = 9.4±1.3× 10–9 cm2/s, were obtained. The diffusion coefficients were found to be statistically independent of the position and depth on the lateral surface of the cornea from which the scattered light was sampled. The slow diffusion coefficients obtained from light sampled from within cross-sections of the cornea were, however, measurably different. Diffusion coefficients obtained independently from observations of the kinetics of corneal swelling for comparison were found to be several orders of magnitude greater than those obtained from light scattering. The large disparity in the diffusion coefficients obtained from the two independent methods invoked the possibility that the lamellar layers within the cornea behave as individual gel sheets. Irrespective of this additional hypothesis, divergent behavior in the measured total scattered light intensities and diffusion coefficients upon varying external conditions, such as temperature or pressure (stretching), was observed. Namely, a slowing down of the dynamic modes accompanied by increased “static” scattered light intensities was observed. Although the slowing down of the dynamic modes is possibly indicative of the reduced affinity of protein binding to the gel matrix that “softens” the gel, the divergent behavior in the scattered light intensities and diffusion coefficients is, however, more characteristic of a phase transition. In addition, the divergent behavior in the scattered light intensities and diffusion coefficients was reversible up to a critical temperature (∼55 °C) or stretching (∼16%).

Error of Ocular Rotation Angle Measured by Major Amblyoscope

This research goal is to explore biocompatible and extremely transparent artificial vitreous body, using poly (vinyl alcohol) (PVA) hydrogel. PVA of degree of polymerization (DP) 2,000 and DP 8,000 in aqueous solution were irradiated by gamma-ray to form hydrogels. These hydrogels were characterized by viscosity and dynamic light scattering to check about degradation and polymerization process. In vitro, the activity of Chemotaxis of PVA hydrogel is almost same as that of silicone. PVA hydrogels were implanted into vitreous bodies of rabbits. No abnormality was histologically observed in cornea, lens and vitreous body, except some damage to injection areas in a few cases. No inflammatory reaction was observed between PVA hydrogels and native vitreous body. The postoperative intraocular pressure (IOP) was maintained within 8 mmHg higher than before operation. PVA hydrogel seems to have good biocompatibility for clinical usage.