HK1237230B - Method and system for measuring light diffusion in the eyeball or in the ocular region - Google Patents

Description

Method and system for measuring light diffusion in an eyeball or an eye region

Technical Field

In a first aspect, the present invention generally relates to a method for measuring light diffusion in an eye or an eye region, and more particularly to a method for combining aberration measurement information of the eye with information on an image of the retinal plane of one or both eyes of a patient.

A second aspect of the invention relates to a system suitable for implementing the method of the first aspect.

A third aspect of the invention relates to a computer program adapted to implement the method of the first aspect.

Background Art

Light diffusion in the eyeball or in the ocular region is one of three causes of image degradation of the retina in the human eye, the other two being optical aberrations and diffraction.

The combination of optical aberrations and intraocular diffusion together affects retinal image quality. The double-pass technique (J. Antamaria, P. Artal, J. Bescos, "Determination of the point-spread function of human eyes using a hybrid optical-digital method", J., Opt. Soc. Am. A, 4, 1109-1114 (1987)) is based on projecting a parallel light beam onto the patient's retina and directly recording the light reflected therein after the light has passed through the ocular medium in a double pass, allowing an objective measurement of the contribution of aberrations and intraocular diffusion to the optical quality of the eye to be obtained (F. Diaz-Douton, A. Benito, J. Pujol, M. Arjona, JL Guell, P. Artal, "Comparison of the retinal image quality obtained with a Hartmann-Shack sensor and a double-pass instrument", Inv. Ophthal. Vis. Ciencia., 47, 1710-1716 (2006)).

In the article entitled "Comparison of the retinal image quality obtained with a Hartmann-Shack sensor and a double-pass instrument" (F. Diaz-Douton, A. Benito, J. Pujol, M. Arjona, JL Guell, P. Artal, Inv. Ophthal. Vis. Ciencia., 47, 1710-1716 (2006)), the use of a double-pass technique by means of a wavefront sensor (in particular by means of a Hartmann-Shack sensor) and an ocular aberration measurement technique alone is described, with the aim of comparing the results obtained by means of the two techniques to determine when one is superior to the other in assessing the quality of the retinal image. It was concluded that for eyes with low intraocular diffusion, both techniques provide similar results, whereas for eyes with medium or high intraocular diffusion values, the double-pass technique is better because it produces a more accurate description of the optical quality that is most relevant to visual quality, while the aberration measurement technique can produce results that overestimate the quality of the retinal image.

The article does not suggest combining the results obtained by using each of the two techniques to obtain a combined result, or measuring light diffusion in the eye or ocular region, or performing any other type of measurement.

Furthermore, patent application EP 2 147 633 A1 proposes a method and a system for measuring light diffusion in an eyeball or an eye region, which comprises performing the steps described in the preamble of claim 1 of the present invention.

Summary of the Invention

There is a need to provide an alternative solution that covers the gaps in the prior art and that provides more accurate light diffusion measurements in the eyeball or ocular region than is obtained by prior art proposals.

To this end, the present invention relates in a first aspect to a method for measuring light diffusion in an eyeball or an eye region, comprising performing the following steps:

projecting a spot beam of light onto the retina of at least one eye of the patient;

correcting low-order ocular aberrations of the eye; and

Once the low-order aberrations are corrected, at least one image of the retinal plane is captured and recorded, the image being formed after the point-shaped light beam reflects off the retina and passes twice (double passage through) the ocular medium of the eye.

Unlike known methods for performing measurements, in which at most one ocular aberration measurement is used to verify the results obtained by processing the image of the retinal plane and the information on said image, the method proposed in the first aspect of the present invention characteristically comprises performing high-order and low-order ocular aberration measurements and light diffusion measurements in the plane of the pupil of the eye while capturing said image of the retinal plane, combining the information obtained by said ocular aberration measurements with the information on said image of the retinal plane.

Capturing an image of the retinal plane and taking both high-order and low-order ocular aberration measurements simultaneously is necessary to obtain good results with respect to light diffusion measurements, because if they do not occur simultaneously, the circumstances in which the two measurements are taken (those associated with capturing an image of the retinal plane and the ocular aberration measurements) will not be the same or similar enough to be combined with one another.

The low-order aberrations preferably include astigmatism and defocus.

According to one embodiment, the method proposed by the first aspect of the invention is implemented in both eyes of the patient using open field techniques and/or in a binocular manner.

According to one embodiment, high-order and low-order ocular aberration measurements are second measurements, wherein the method comprises previously performing a first ocular aberration measurement of the patient's eye and using the obtained results for correction of said low-order ocular aberrations of the eye.

Low-order ocular aberrations may be corrected using any known technique, ranging from techniques associated with standard methods to those disclosed in patent application EP2147633A1 of the applicant of the present patent application.

Advantageously, the method of the first aspect of the invention comprises using the same system for measuring aberrations (typically an aberrometer) to perform the first and second ocular aberration measurements. In another less preferred embodiment, two systems for measuring aberrations are used, one for each of the first and second measurements.

The method comprises performing the mentioned high-order and low-order ocular aberration measurements on the wavefront resulting from the reflection of the point-shaped light beam on the retina as it passes through the plane of the pupil.

According to one embodiment, the method of the invention comprises analyzing, at the plane of the pupil, the light distribution of an image of the retinal plane and of an image corresponding to said ocular aberration measurement at said wavefront, and performing a light diffusion measurement by comparing the two distributions of light, advantageously corresponding to each light spot of the two images.

For one embodiment, the method comprises calculating the objective scatter index (OSI) described in patent application EP2147633A1 using information of the image at the retinal plane, and combining the result obtained with the result obtained by applying any known method to the ocular aberration measurement information for obtaining the final light diffusion measurement.

In another embodiment, the method includes applying a corresponding optical transfer function (or OTF) to the ocular aberration measurement information and the image information at the retinal plane, and performing a light diffusion measurement in combination with the results provided by the OTF function.

According to a variant of said embodiment, the method proposed by the first aspect of the invention comprises performing a light diffusion measurement, combining the results provided by said OTF function and also comparing the two said light distributions.

Regarding the OTF function, said function comprises at least the absolute values of the corresponding modulation transfer functions (MTF), wherein said method comprises performing a dividing value of light diffusion measurements associated with profiles (e.g. radial profiles or unidirectional profiles) generated using said absolute values, e.g. calculating the existing area under the curve of said profile, performing said dividing using the values calculated for said area.

According to one embodiment, the OTF function includes complex parameter values in a corresponding phase transfer function (or PTF).

A second aspect of the invention relates to a system for measuring light diffusion in an eye or an eye region, comprising:

means for projecting a spot beam of light onto the retina of at least one eye of the patient;

means for capturing and recording an image of the retinal plane, said image being formed after said point-shaped light beam has reflected on the retina and passed twice through the ocular medium of said eye; and

Means for correcting low-order ocular aberrations of said eye prior to said capturing and recording.

Different from the known systems, the system proposed by the second aspect of the present invention comprises

means for performing high-order and low-order ocular aberration measurements in the plane of the pupil of said eye;

control means that control at least said means for capturing and recording images of the retinal plane and said means for performing ocular aberration measurements so that they operate simultaneously; and

Processing means for processing the information obtained by said eye aberration measurement together with the information of said image at the retinal plane in a combined manner and providing one or more values of said light diffusion measurement as a result of said processing.

A system proposed by a second aspect of the present invention is provided for implementing the method according to the first aspect.

Preferably, the means for projecting a spot-shaped light beam onto the retina of the patient's eye and the means for capturing and recording an image of the retinal plane are part of a double-pass ophthalmoscopic system.

Advantageously, the system proposed by the second aspect of the invention is configured and arranged to use openfield techniques.

For a preferred embodiment, the system proposed by the second aspect of the present invention is configured and arranged for implementing a binocular system applied to both eyes of a patient.

For another less preferred embodiment, the system proposed by the second aspect of the present invention is configured and arranged for implementing a monocular system.

According to a preferred embodiment, the means for correcting low-order ocular aberrations comprise or are associated with means for performing ocular aberration measurements, so as to correct ocular aberrations based on measurements performed with the means for performing ocular aberration measurements.

In another less preferred embodiment, the means for correcting low-order ocular aberrations and the means for performing ocular aberration measurements are independent of each other.

A third aspect of the present invention relates to a computer program comprising code instructions, which, when executed in a computer, performs light diffusion measurement in an eyeball or an eye region according to the method of the first aspect, and processes data corresponding to information obtained by eye aberration measurement and data corresponding to information on an image of the retinal plane in a combined manner.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned and other advantages and features will be better understood based on the following detailed description of several embodiments with reference to the accompanying drawings, which must be understood in a non-limiting illustrative manner, in which:

FIG1 is a perspective view of a schematic diagram of an embodiment of a system proposed by the second aspect of the present invention, wherein the embodiment implements an open-field binocular system.

DETAILED DESCRIPTION

According to the embodiment shown in FIG1 , the system for measuring light diffusion in the eyeball or eye region according to the second aspect of the present invention is an open-field binocular system, which includes a device for projecting a punctiform light beam onto the retinas of the patient's two eyes O1 and O2, the device including a punctiform light source SLD, which generates a collimated light beam distributed through a mask or pupil P1 into two corresponding emission sub-beams. beam) (typically a laser), the two respective emission sub-beams are directed towards each of the two eyes O1, O2 through a series of conventional optical elements, in particular beam splitters BS1 and BS2 acting as mirrors and lenses L1 and L2, and after each emission sub-beam has been redirected to the respective eye O1, O2 by the mirror M1, each of the two emission sub-beams is directed individually through one of the respective optical element groups, each of which is in particular formed by a pair of cylindrical lenses C1-2 and C3-4, followed by another lens LL1 and LL2, another pupil P2 and P3, a respective mirror M2 and M4, another lens L3 and L5, a dichroic mirror DM1 and DM2 and finally a hot mirror HM1 and HM2, after which the emission sub-beams impinge on the retinas of the eyes O1, O2.

FIG1 also shows how the system comprises an arrangement consisting of two cameras CCD-DP1y, CCD-DP2, each camera being provided for capturing and recording an image of a plane of one of the retinas, the image being formed after two point-shaped emission sub-beams of light are reflected within the retina and pass twice through the ocular medium of the two eyes O1, O2, generating corresponding reflected sub-beams along paths opposite to the paths of the emission sub-beams, passing through optical elements to reach the beam splitter BS2, which reflects a portion of each of the reflected sub-beams, passes through the lens L1 and the beam splitter BS1, after which each reflected sub-beam is directed by a mirror M3 towards one of the cameras CCD-DP1 and CCD-DP2.

The pair of cylindrical lenses C1-2 and C3-4 is a device or part of a device that corrects low-order ocular aberrations of the eyes O1, O2 before capturing and recording the image of the retinal plane.

Furthermore, FIG1 shows how the system also comprises means for performing high-order and low-order ocular aberration measurements in the plane of the pupils of the two eyes O1, O2, which means in particular consist of a Hartmann-Shack sensor HS which is illuminated by part of the two reflected sub-beams passing through the beam splitter BS2 and the lens L4.

FIG1 also shows the direction of the light in the first and second channels by means of arrows, ie the emitted sub-beam towards the retina and the reflected sub-beam in the opposite direction.

FIG1 also shows an electronic system SE communicating in a bidirectional manner with the cameras CCD-DP1, CCD-DP2 and the Hartmann-Shack sensor HS, and comprising control means MC for controlling at least the CCD-DP1, CCD-DP2 and HS so that they operate simultaneously, and processing means MP for processing the information obtained by means of the CCD-DP1, CCD-DP2 and HS in a combined manner and providing one or more values of light diffusion measurement as a result of said processing.

For an embodiment not shown, the control means MC are connected to the pair of cylindrical lenses C1-2 and C3-4 (and/or to any other type of alternative mechanism suitable for correcting low-order ocular aberrations) to control them for the purpose of correcting ocular aberrations as mentioned, depending on the ocular aberration measurement performed with the Hartmann-Shack sensor HS.

Those skilled in the art may introduce changes and modifications in the described embodiments without departing from the scope of the invention as defined in the appended claims.

Claims (14)

1. A method for measuring light diffusion in the eyeball or an area of the eye, characterized in that the method comprises performing the following steps: A point beam of light is projected onto the retina of at least one of the patient's eyes; Perform a first ocular aberration measurement on the at least one eye and use the obtained results to correct for low-order ocular aberrations of the eye; Once the lower-order aberrations are corrected, at least one image of the retinal plane is captured and recorded, which is formed after the dot beam of light is reflected on the retina and passes twice through the ocular medium of the eye; While capturing and recording the image in the retinal plane, high-order and low-order second ocular aberration measurements are performed in the plane of the pupil of the eye; and Perform light diffusion measurements and combine the information obtained through the higher-order and lower-order ocular aberration measurements with the information from the image in the retinal plane. 2. The method of claim 1, wherein the method is implemented using an opening technique. 3. The method according to claim 1 or 2, wherein the method is performed in both eyes of the patient in a binocular manner. 4. The method of claim 1, further comprising performing the higher-order and lower-order ocular aberration measurements on the wavefront as the wavefront passes through the plane of the pupil, wherein the wavefront originates from the reflection of the point beam on the retina. 5. The method of claim 1, further comprising using the same system to measure aberrations for performing the first and second ocular aberration measurements. 6. The method of claim 4, comprising analyzing the light distribution of an image of the retinal plane in the plane of the pupil and the light distribution of an image corresponding to the ocular aberration measurement on the wavefront, and performing a light diffusion measurement by comparing the two light distributions. 7. The method of claim 6, wherein the method comprises analyzing the light distribution for each spot in the two images. 8. The method of claim 6 or 7, further comprising applying a corresponding optical transfer function to ocular aberration measurement information and image information in the retinal plane, and performing a light diffusion measurement in conjunction with the results provided by said optical transfer function, wherein... The light diffusion measurement is performed by combining the results provided by the optical transfer function and the results obtained by comparing the two light distributions. 9. The method of claim 8, wherein the optical transfer function comprises at least the absolute value of a corresponding modulation transfer function, wherein the method comprises performing an optical diffuse measurement, segmenting values associated with a contour generated using the absolute value, wherein The segmentation is performed by calculating the existing region under the curve of the contour to obtain the value associated with the contour, and using the value calculated for the corresponding region. 10. The method of claim 8, wherein the optical transfer function includes complex parameter values in the corresponding phase transfer function. 11. The method of claim 1, wherein the lower-order aberrations include astigmatism and defocus. 12. A system for measuring light diffusion in the eyeball or an area of the eye, comprising: Device for projecting a dot beam of light onto the retina of at least one eye (O1, O2) of a patient; Devices (CCD-DP1, CCD-DP2) for capturing and recording images of the retinal plane, the images being formed after the dot-shaped light beam reflects off the retina and passes twice through the ocular medium of the eye (O1, O2); and Apparatus (C1-2, C3-4) for performing low-order ocular aberration correction of the eyes (O1, O2) based on the results of the first ocular aberration measurement before the capture and recording; The system is characterized in that it further includes: A device (HS) for performing a first ocular aberration measurement of at least one eye (O1, O2) and for performing high-order and low-order second ocular aberration measurements in the plane of the pupil of the eyes (O1, O2), wherein the result of the first ocular aberration measurement is used to perform correction of the low-order aberrations; A control device (MC) that controls at least the means for capturing and recording images of the retinal plane (CCD-DP1, CCD-DP2) and the means for performing the first and second ocular aberration measurements (HS), such that they operate simultaneously; and A processing device (MP) processes information obtained through the second ocular aberration measurement together with information from the image in the retinal plane in a combined manner, and provides one or more values of the light diffusion measurement as a result of the processing. The system is used to implement the method according to any one of claims 1 to 11. 13. The system of claim 12, wherein the means for projecting a dot beam of light onto the retina of the patient's eye and the means for capturing and recording an image of the retinal plane (CCD-DP1, CCD-DP2) are part of a dual-access ophthalmoscopy system, and wherein the system Configured and arranged to use opening techniques And/or configured and arranged to realize a binocular system applied to the patient's two eyes (O1, O2). 14. The system of claim 12 or 13, wherein the means (C1-2, C3-4) for performing low-order ocular aberration correction includes or is associated with means (HS) for performing the first ocular aberration measurement and the second ocular aberration measurement, for the correction of the ocular aberration based on the measurement performed using the means (HS).