JPH10174676A - Contact lens for observation and imaging of eyeground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an eyeground camera wide-angle by specifying a synthesized visual angle of a contact lens and an eye to be examined when the contact lens which is to be placed by bringing it into contact with the eye to be examined and changes the apparent angle of imaging of an optical system for observation of the eyeground is placed by bringing it into contact with the eye to be examined. SOLUTION: A light emitted from a light source 19 for illumination is focused at the position of a light source 17 for imaging by means of a condenser lens 18 and the light emitted from this light source 17 is passed through the first relay lens 16 and an image is formed in the vicinity of a perforated mirror 12 through an aperture of a ring slit 14 and the second relay lens 13. The light reflected on the perforated mirror 12 is passed through an objective lens 1 and enters into a contact lens L and forms a ring-like illmination light at the position of the pupil of an eye to be examined. In this instance, when the radius of curvature on the object face side of the contact lenz is RL and the thickness at the center is (d), a condition of 0.5<=d/RL<=1.8 is satisfied and, when the contact lens is fitted, the synthesized visual angle is made approximately zero diopter to hold emmetropia of the eye.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used with an ophthalmic observation apparatus, for example, a fundus camera or an ophthalmoscope, and is used for observation and photographing of a fundus of an eye to be examined (hereinafter referred to as a contact lens). ).

[0002]

2. Description of the Related Art A fundus camera has conventionally been required to have a wide angle of view and a high quality image as a means for recording fundus information of an eye to be examined. Especially in diabetic retinopathy, it is said that the initial signs appear in the periphery of the fundus, and the recording was conventionally combined with several images to form a wide-angle image. Instead of such means, there is a need for a fundus camera with a high angle of view that can obtain an image up to the peripheral portion of the fundus with a single photographing.

On the other hand, when photographing the fundus of a subject's eye with a fundus camera, harmful light from the cornea and lens of the subject's eye significantly reduces the image quality. Therefore, the fundus camera employs a so-called ring illumination in which illumination light is incident from the periphery of the pupil of the eye to be examined and such harmful light is not mixed into the imaging angle of view. The ring diameter of this ring illumination must be increased as the angle of view of the fundus camera becomes wider.

[0004] However, the diameter of the pupil of the subject's eye is limited,
If the ring diameter is larger than a predetermined value, the illumination light cannot be made incident on the eye to be examined. Therefore, there is a limit to widening the angle of view of a fundus camera employing ring illumination. The upper limit of the angle of view (2θ) of the currently used fundus camera is approximately 60 °
It is.

Therefore, another technique is required to further increase the angle of view of photographing. Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent Application Laid-Open No. 1969691, a technique is known in which a contact lens is worn on an eye to be inspected to change the angle of view of the eye to be inspected without changing the angle of view of a fundus camera.

[0006]

However, Japanese Patent Laid-Open No.
Japanese Patent Application Publication No. 1996961 does not show the relationship between the angle of view of the fundus camera and the angle of view in the eye of the subject's eye according to the specific shape of the contact lens. Therefore, there is a problem that it is not possible to specify the shape of the contact lens capable of capturing a desired angle of view.

[0007] Further, although a change in the focal position of the fundus camera when the contact lens is worn is described, since the correction method is configured to add a correction function to the fundus camera body, it is already used. If the fundus camera does not support adding a correction mechanism, there arises a problem that the use of the contact lens itself becomes impossible.

On the other hand, when the correction mechanism is not added, there is a problem that depending on the contact lens to be added, the focus lens deviates from the in-focus range and photographing becomes impossible.

The present invention has been made in view of such a problem, and has as its object to provide a contact lens capable of widening the angle of the fundus camera without requiring the focus correction function of the fundus camera.

[0010]

In order to achieve the above object, the present invention relates to a contact lens which is placed in contact with an eye to be examined and changes an apparent angle of view of an optical system for fundus observation, wherein the contact lens is When placed on the subject's eye, the combined diopter of the contact lens and the subject's eye is substantially zero diopter.

"Diopter" refers to the reciprocal of the focal length in meters. When a contact lens is attached to the eye, the diopter changes as compared with the case of the naked eye, and focusing may not be possible. However, according to the present invention, with such a configuration, when observing the fundus using a fundus camera or the like,
While changing the angle of view of the optical system for fundus observation, especially while expanding it,
By setting the combined diopter to approximately 0 diopter when wearing a contact lens, it becomes possible to maintain the normal vision of the eye, that is, to achieve focusing. The composite diopter is most preferably about 0 diopters, but is not limited to this. Focusing is also possible in the range of -5 to +5 diopters, and more preferably -2 to +2.
It may be in the diopter range.

Further, the contact lens for fundus oculi observation and photographing according to the present invention has the following condition: 0.5 ≦ d / RL ≦ 1.8, where RL is the radius of curvature on the object plane side of the contact lens and d is the center thickness. It is characterized by satisfaction. By satisfying such conditions, it is possible to specify the shape of the contact lens that can obtain the required effect of enlarging the angle of view.

[0013]

FIG. 1 schematically shows the structure of a contact lens L of the present invention and a conventional fundus camera. The light emitted from the illumination light source 19 is condensed by the condenser lens 18 at the position of the imaging light source 17 placed at a position conjugate with the illumination light source 19. Therefore, in the subsequent illumination system optical system, the light from the imaging light source is equivalent to the light from the illumination light source.

The light emitted from the photographing light source 17 illuminates the ring slit 14 after passing through the first relay lens 16.
At this time, the illumination light source 19 or the imaging light source 17 and the ring slit 14 are substantially conjugate with the relay lens 16.

The light that has passed through the opening of the ring slit 14 is imaged by the second relay lens 13 near the perforated mirror 12. That is, the ring slit 14 and the perforated mirror 12 are also substantially conjugated. Since the ring aperture image of the ring slit is formed larger than the hole diameter of the perforated mirror, the illumination light and the photographing light are separated here.

Further, the light reflected by the perforated mirror 12 passes through the objective lens 1 and then enters the contact lens L, and emits ring-shaped illumination light to the pupil position 20 of the eye to be examined which is substantially conjugate with the perforated mirror. Form.

The illumination light incident on the eye illuminates the fundus of the eye. The fundus image of the eye to be examined passes through the contact lens L, is formed once by the objective lens 1, passes through the hole of the perforated mirror 12, passes through the imaging relay lens 2, the variable power lens 3, and the light receiving surface 5 is formed. Therefore, the contact lens L and the objective lens 1 are shared by the observation / photographing system and the illumination system.

Further, switching reflecting members 4 and 8 for switching the optical path are provided. If the switching reflecting member 4 is on the optical path as shown in FIG. By placing it at the eye point position, it is possible to observe the fundus image of the subject's eye without being blurred.

When the switching reflecting member 4 is retracted out of the optical path and another switching mirror 8 is inserted into the optical path, the fundus oculi image is formed on the light receiving surface 1 of the second photographing means including the imaging lens 9 and the reflecting mirror 10.
1 is imaged.

FIG. 2 is a diagram showing the relationship between the angle of view of the fundus camera and the angle of view in the eye of the subject's eye. NO and NO 'represent the front node and the rear node of the subject's eye, respectively. If the maximum angle of view of the fundus camera is θ, the front node NO of the subject's eye is NO
Are emitted at the same angle θ as the incident angle θ from the rear node NO ′ of the subject's eye. Now, assuming that the eyeball is a sphere having a radius R and its center is O, the shooting range of the fundus camera can be represented using the angle α in the eye.

FIG. 3 shows the contact lens of the present invention in FIG.
It is a case where it is mounted under the same condition as that of FIG. By wearing the contact lens, the entire joint of the eye with the contact lens moves to positions N and N '.

Accordingly, as can be seen from the figure, the angle of view of the fundus camera is unchanged, but the angle of view α 'in the eye centered on the point O is larger than that without a contact lens.
For this reason, by adding a contact lens, it becomes possible to photograph the inside of the eye over a wide range.

When the eye of FIG. 2 is an emmetropic eye, the rear focal point F of the eye
Since O 'is considered to coincide with the retinal surface, the following equation holds.

Sin θ / R = Sin (α−θ) / (NO′FO′−R) (2) Here, if the radius of curvature of the cornea is RC and the refractive index of the eye is n, NO′FO ′ = RC / ( n-1) (3). Therefore, the angle α in the eye is approximately expressed as follows.

Α = 1 / (n−1) · RC / R · θ (4) Table 1 shows the relationship between equations (2) and (4).

[0026]

[Table 1] The parameters are R = 12 mm, RC = 7.7 mm, and the refractive index n = 1.45294 is the front focal length ff = 1 / (n−1) · RC (5) of the eye expressed by the following equation (5). ) Is determined to be 17 mm. Table 1 shows that the angle in the eye is about 1.4 times the angle of the fundus camera. Equation (4) is approximated by 2θ = 60
Even in °, the error is within a range of about 1%.

As shown in FIG. 3, when the contact lens is attached, the entire rear focal point F ′, which is generally composed of the contact lens and the optical system of the eye, moves to a position different from the retinal plane. .

At this time, the distance δ between the rear focal point F ′ and the retinal surface is expressed by the following equation.

Sin θ / R = Sin (α′−θ) / (N′F ′ + δ−R) (6) Assuming now that the refractive index of the contact lens is equal to the refractive index of the eye, RL is the curvature of the contact lens. As a radius, N′F ′ = RL / (n−1) (7) Further, at this time, δ is δ = n / (n−1) · RC + dn / (n−1) · RL (8) where d is the center thickness of the contact lens. Is generally expressed as follows.

Α ′ = (n / (n−1) · RC + d−RL) · θ / R (9) Here, assuming that the diopter of the entire eye on which the contact lens is worn is 0 diopter, the curvature of the cornea If the radius RC is replaced with the radius of curvature RL of the contact lens, equation (9) is obtained.
Can be written in the same manner as in equation (4), so that α ′ can be expressed as follows.

Α ′ = 1 / (n−1) · RL / R · θ (10) Therefore, the angle α ′ in the eye when the contact lens is worn and the angle α in the eye when the contact lens is absent The ratio is expressed as:

Α ′ / α = RL / RC (11) Therefore, the curvature radius RL of the contact lens is given by giving the ratio of the angle of view with and without the contact lens.
Can be obtained as in the following equation.

RL = α ′ / α · RC (12) Further, the center thickness d of the contact lens is represented by the following equation.

D = n / (n−1) (α ′ / α−1) · RC (13) In addition, the angle of view of the fundus camera corresponding to the angle α ′ in the eye (hereinafter, referred to as converted angle of view). Is calculated by substituting α ′ for α in equation (4) and calculating θ ′ back. That is, θ ′ = (n−1) · R / RC · α ′ (14)

Another consideration in contact lens design is the distance between the fundus camera and the contact lens. As the ratio of the angle of view in the eye with and without the contact lens increases, the center thickness of the contact lens increases, and the distance between the fundus camera and the contact lens decreases. Therefore, if the angle of view ratio is too large, the fundus camera comes into contact with the contact lens.

Since the ring slit of the fundus camera forms an image near the iris of the eye, the position of the fundus camera when a contact lens is attached is determined by the position where the ring slit of the fundus camera forms an image near the iris through the contact lens and the cornea. Become. The pushing amount X of the ring slit is represented by the following equation.

1 / X−n / (d + 3.6) = (1−n) / RL (15) The pushing amount X must be larger than the working distance of a normal fundus camera.

Since the working distance of the current fundus camera is about 60 mm at the longest, the ratio of the angle of view is about 2.3 as the upper limit from the equation (15).

Therefore, d / RL ≦ 1.8 (16) is derived from the equation (13).

Conversely, if the angle of view ratio is reduced, it becomes impossible to photograph a wide area, and it becomes meaningless to wear a contact lens.

In order to improve the angle of view ratio by at least 20%, it is necessary to satisfy the following condition: 0.5 ≦ d / RL (17) In order to improve at least the angle of view ratio by 50% or more, it is necessary to satisfy 1.0 ≦ d / RL (18).

[0042]

FIG. 4 shows a first embodiment of the present invention based on the data shown in Table 2.

[0043]

[Table 2] The magnification of the angle of view is 1.2 times.

FIG. 5 shows a second embodiment of the present invention based on the data in Table 3.
An example will be described.

[0045]

[Table 3] The magnification of the angle of view is 1.7 times.

FIG. 6 shows a third embodiment of the present invention based on the data in Table 4.
An example will be described.

[0047]

[Table 4] The magnification of the angle of view is 2.2 times.

[0048]

As described above, by using the fundus observation lens of the present invention, the effect of expanding the angle of view can be obtained without providing any focus correction mechanism on the fundus camera side. Further, it is possible to specify the shape of the contact lens that can obtain the required effect of enlarging the angle of view, and it is possible to obtain a contact lens in which the contact lens does not come into contact with the fundus camera.

As a result, it becomes possible to photograph the fundus of the eye to be examined with a wider angle of view by using a conventionally used fundus camera.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the structure of a contact lens and a fundus camera according to the present invention.

FIG. 2 is an explanatory diagram showing a relationship between an angle of view of a fundus camera and an angle of view in an eye.

FIG. 3 is an explanatory diagram showing the relationship between the angle of view of the fundus camera and the angle of view in the eye when the contact lens of the present invention is worn on the eye.

FIG. 4 is an explanatory diagram showing a shape of a contact lens according to the first example of the present invention.

FIG. 5 is an explanatory view showing a shape of a contact lens according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a shape of a contact lens according to a third example of the present invention.

[Explanation of symbols]

 L Contact Lens for Fundus Observation and Photography 1 Objective Lens 2 Relay Lens for Photography 3 Magnifying Lens 4, 8 Switching Reflecting Member 5 First Light-Receiving Surface 7 Eyepiece 9 Imaging Lens for Second Imaging Means 11 Second Light receiving surface 12 Perforated reflector 13, 16 Illumination relay lens 14 Ring slit 17 Imaging light source 18 Condenser lens 19 Illumination light source 20 Eye position of subject eye 21 Eye point position for examiner 22, 23 Conical reflection member

Claims (2)

[Claims] 1. A contact lens which is placed in contact with an eye to be examined and changes an apparent angle of view of an optical system for fundus observation, wherein the contact lens and the object are placed when the contact lens is placed on the eye to be examined. A contact lens for fundus oculi observation and photographing, wherein the combined diopter of the optometry is approximately 0 diopter. 2. The condition that 0.5 ≦ d / RL ≦ 1.8 is satisfied, where RL is a radius of curvature on the object surface side of the contact lens and d is a center thickness. The contact lens for fundus observation photography described in the above.