JP3423030B2 - Ophthalmic equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ophthalmic apparatus, and more particularly, to a refractometer for measuring a fundus reflection image of a measurement target to obtain an eye refractive index, The present invention relates to an ophthalmologic apparatus such as a keratometer that measures a corneal reflection image of a measurement target and determines a corneal curvature radius. 2. Description of the Related Art Conventionally, when an eye refraction is obtained based on a fundus reflection image of an eye to be examined by a refractometer, the eye refraction power must be obtained if at least data in the three meridian directions of the fundus reflection image is known. Was completed. Further, even when the corneal radius of curvature of the eye to be examined is determined by a keratometer, it is possible to calculate the corneal radius of curvature if at least data in the 5-meridian direction of the corneal reflection image is known. [0004] When projecting the target on the fundus of the eye or the cornea of the eye using a ring target as the measurement target, it is more difficult to receive the reflected image with an area sensor. In order to grasp the ring shape with high accuracy, a large number of meridian data are calculated at certain fixed angles, and the ring shape is approximated by an ellipse using the meridian data to obtain the eye refractive power and the corneal curvature radius. [0005] As in the prior art, the calculation using a small number of meridian data is likely to cause a measurement error when affected by pine hair or the like around the eye to be inspected, and the calculation results may vary. It can also be a cause. Further, in order to calculate a large number of meridian data at equal intervals, when a measurement error occurs due to a pine hair or the like, the data is interpolated by linear approximation or the like. As a result, measurement errors can be reduced, and the calculation formula can be simplified, which is advantageous in terms of calculation time and the like. However, for example, when the meridian data portion that cannot be calculated is wide, interpolation of the meridian data may greatly change the calculation result from the actual fundus reflection image. As a result, the amount of astigmatism may become larger than the actual amount of astigmatism, or the astigmatic axis angle may deviate from the actual angle. In particular, when the corneal curvature radius is obtained based on the corneal reflection image, the degree of corneal irregular astigmatism may be canceled. SUMMARY OF THE INVENTION It is an object of the present invention to provide an ophthalmologic apparatus capable of accurately determining the refractive index of an eye and the radius of curvature of a cornea even when the meridian data which cannot be calculated is wide. The present invention comprises a projecting means for projecting a measurement target to an eye to be examined, and a light receiving means for receiving a reflected image of the target from the eye to be examined. In an ophthalmologic apparatus for obtaining optical characteristics of an eye to be inspected based on light receiving data of the light receiving means, there is a data missing part based on the light receiving data.
Determining means for determining whether or not the fixed amount has been exceeded; and calculating mode based on the determination result of the determining means, the calculation mode having an equally spaced distribution.
Calculation switching means for switching to either a calculation mode of non-uniform distribution or unequally spaced distribution . The operation of the ophthalmologic apparatus according to the present invention will be described below. In this ophthalmologic apparatus, the measurement target is projected onto the eye by the projection means, and a reflected image of the target from the eye is received by the light receiving means. The calculating means determines the optical characteristics of the subject's eye based on the received light data from the light receiving means.
Determines whether there is a missing part in the received light data.
Then, the operation switching means detects that the light receiving data has a missing part.
If there is no equidistant distribution, select the normal calculation mode and
In the case of equidistant distribution where the amount of received data is slightly missing
Selects the correction calculation mode, and the data amount of the received light data
If the distribution is uneven due to lack of
Select a mode. The calculating means sets each calculation mode to
Select and calculate the optical characteristics of the eye to be examined. As a result, the optical characteristics of the eye to be inspected, such as the refractive index of the eye and the radius of curvature of the cornea, can be determined with high accuracy even when the uncalculatable portion is meridian data having a wide distribution of unequal intervals. Embodiments of the present invention will be described below in detail. An ophthalmologic apparatus 1 shown in FIG. 1 projects a light beam from a light source 3 passing through a ring target 2 which is a measurement target to a fundus ER of an eye E to be examined, and forms a reflected image from the fundus ER. A measuring optical system 5 that forms a two-dimensional image on a light receiving surface of the light receiving unit 4, and a storage unit that stores, under the control of the control unit 6, data of the eye to be inspected corresponding to the reflected image processed by the light receiving unit 4. 7, an operation switching unit 8 having an operation mode setting function for switching an operation mode of an operation unit 9 described later according to the amount and distribution state of the subject's eye data stored in the storage unit 7, and stored in the storage unit 7. Optical characteristic calculation based on the subject eye data having an evenly distributed distribution based on the subject eye data obtained and in response to the switching signal from the arithmetic switching means 8, optical characteristics based on the subject eye data having a data amount lacking in the regular interval distribution Operation and Calculation means 9 for selectively executing the optical characteristic calculation based on the subject's eye data (when an eyelash image is present or when an intraocular lens is inserted) having a uniform distribution, and a liquid crystal display for displaying the calculation result of the calculation means 9 And display means 10 as shown in FIG. The calculation switching means 8 determines whether or not the eye data having an equidistant distribution exists based on the judgment of the examiner based on the display mode of the display means 10 for displaying the calculation result of the calculation means 9, for example. It is possible to set a normal calculation mode, a correction calculation mode in the case where the subject's eye data having a data amount lacking in the uniform interval distribution exists, and an unequal interval calculation mode in the case where the subject's eye data having the unequal interval distribution exists. . Next, the operation of the ophthalmologic apparatus 1 will be described with reference to FIGS.
This will be described with reference to FIG. When the ring target 2 is projected on the fundus ER of the eye E to be inspected and its reflected image is received by the light receiving means 4,
The reflected image can be represented as an elliptical image having an X-axis direction inclined at an angle A from the X0 axis with the long axis as a reference and a short axis as the Y-axis direction as shown in FIG. That is, each radius data (ri) having an angle θi from the X axis in the meridian direction is obtained from the reflected image, and an elliptical image is approximated from the result. The general formula of the ellipse is given by Equation 1. [Equation 1] For Xi and Yi of Equation 1, (Equation 3) Substituting into (Equation 4) By transforming equation (4), equation (5) is obtained. (Equation 5) Therefore, Equation 5 can be represented by Equation 6 below. (Equation 6) When the least squares approximation is performed on Equation 6, the above equation becomes Equation 7. (Equation 7) Equations (8) to (10) can be derived from equations in which F is differentiated by X1, X2, and X3 and set to 0. [Equation 8] (Equation 9) [Mathematical formula-see original document] If the eye data in each meridian direction is obtained at equal intervals, Equations 8, 9, and 10 can be expressed by Equations 11 to 13. [Mathematical formula-see original document] [Mathematical formula-see original document] (Equation 13) That is, a large number of meridian data are calculated at a certain fixed angle by the calculating means 9, and the shape of the ring target 2 is approximated by an ellipse based on the meridian data to obtain the eye refractive power. In this case, as described above, X1 through X
Equation 3 is simplified. If there is a slight lack of data among a large number of equally-spaced meridian data, a correction calculation mode is set by the calculation switching means 8 and a correction calculation (data by linear approximation or the like) is performed by the calculation means 9.
By performing the interpolation calculation) , the eye refractive power can be obtained. On the other hand, when eye data in each meridian direction does not exist at equal intervals, that is, when eye data is largely lacked due to eyelash images, or when an intraocular lens is inserted into the eye to be examined, the conventional method is used. As described in connection with the problem, the error component may increase. Therefore, the operation mode is switched by the operation switching means 8 to set the unequal interval operation mode.
A method that can be easily and accurately calculated using the Chromel's formula for the three equations (9) and (10), even if the calculation meridians are not at equal intervals, will be described below. From the elliptic approximation formula: [Equation 15] (Equation 16) Here, when obtaining data of an ellipse in equal angle steps, (Equation 18) (Equation 19) [Mathematical formula-see original document] (Equation 21) Therefore, Expression 14, Expression 15, and Expression 16 are obtained by Expression 2.
2, which can be simplified. [Mathematical formula-see original document] When considering at unequal angles, Equation 14, Equation 15,
Calculating the items of all the equations in Equation 16 results in Equation 24 below. That is, when the terms of Expression 14, Expression 15, and Expression 16 are expressed by the respective items of Expression 23, Expression 14, Expression 15, and Expression 16 become Expression 23 and Expression 24 below. [Mathematical formula-see original document] [Equation 24] Here, the above determinant is solved by the Chromel formula, which is a method for solving the determinant. The Chromel formula is as follows. [Formula 25] When solving the ternary simultaneous equation represented by the following equation, the basic determinant obtained from only the coefficient of the equation 25 is the equation 26. [Equation 26] The co-determinant is given by Equation 27, where Dx, Dy, and Dz are equations for unknowns x, y, and z, respectively. [Mathematical formula-see original document] Here, when Equation 26 is not "0", the simultaneous equation has only one solution, and the solution becomes Equation 28 from Equations 26 and 27, and Can be obtained by This is the Chromel formula. By applying Equations 26, 27 and 28 to Equation 24, Equation 29 is obtained. (Equation 29) Similarly, Dx, Dy and Dz are obtained, and
, Λ 1, λ 2, and λ 3 are given by Equations 30 to 32. [Mathematical formula-see original document] (Equation 31) (32) As described above, when eye data having an evenly spaced distribution exists, eye data having a data amount lacking in an evenly spaced distribution exists, and eye data having an unequally spaced distribution exist. For each of them, the optical characteristics of the eye E to be examined can be obtained without any trouble by the calculating means 9.
Even in the case where the data part that cannot be calculated is eye data having a wide range of unevenly distributed eyes, it is possible to accurately obtain the eye refractive index. Further, during the calculation by the calculating means 9, it is known that the meridian in any direction cannot be used for the calculation (for example, when the eyelashes are darkened or vignetted), and the portion α is shown in FIG. As shown, it is also possible to display the image on the screen of the display means 10 in accordance with the normal ring target image, or to display the measurement error portion. Further, when the reflection image from the eye E is a fundus reflection image obtained by the auto-refractometer and a corneal reflection image obtained by the keratometer, there is a difference in the data of the eye to be examined. In this case, it is also possible to obtain the respective optical characteristics by switching the operation mode of the operation means 9. For example, in the case of a corneal reflection image obtained by projecting a ring target, the light amount distribution of the corneal reflection image becomes clear as shown in FIG. Is adopted. In the case of a fundus reflection image by an auto-refractometer, the light intensity distribution of the fundus reflection image may not be as clear as that of the corneal reflection image as shown in FIG. The means 9 employs an unequally spaced distribution calculation. Further, in the above-described embodiment, the case where the operation mode is switched by the operation switching means 8 based on the judgment of the examiner has been described. However, the operation mode can be automatically switched. That is, the control system of the ophthalmologic apparatus 1 is provided with a judging means for judging whether or not the missing part of the eye data has exceeded a certain amount, and based on the judgment result of this judging means, the missing part of the eye data is determined. When a certain amount is exceeded, the operation mode of the operation means 9 can be automatically switched to the correction operation mode or the unequal interval operation mode. The present invention can be variously modified within the scope of the gist, in addition to the above-described embodiment. According to the present invention described above, with the above-described configuration, the optical characteristics of the eye to be inspected can be obtained without any trouble. In particular, the uncomputable meridian data portion covers a wide range. It is possible to provide an ophthalmologic apparatus capable of accurately determining optical characteristics of an eye to be examined even in the case of eye data having unequally spaced distributions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a control system of an embodiment of the present invention. FIG. 2 is an explanatory diagram showing elliptic approximation of subject's eye data in the embodiment of the present invention. FIG. 4 is an explanatory view showing a display example of a fundus reflection image of an eye to be examined in the apparatus of the embodiment of the invention. FIG. 4 is an explanatory view showing a light amount distribution of a corneal reflection image in the apparatus of the embodiment of the invention. FIG. 1 is an explanatory diagram showing a light amount distribution of a fundus reflection image at a time. [Description of References] 1 Ophthalmologic apparatus 2 Ring optotype 3 Light source 4 Light receiving unit 5 Measurement optical system 7 Storage unit 8 Operation switching unit 9 Operation unit E Eye to be inspected

Claims (1)

(57) [Claim 1] Projection means for projecting a measurement target to an eye to be inspected, and light receiving means for receiving a reflected image of the target from the eye to be inspected, An ophthalmologic apparatus for determining optical characteristics of an eye to be inspected based on received light data of a means, a determining means for determining whether a missing part of data exceeds a certain amount based on the received light data, and a determination result of the determining means The calculation mode is based on the calculation mode of the uniform distribution or the calculation of the non-uniform distribution
An ophthalmologic apparatus comprising: an operation switching unit for switching to any one of the modes .