RU2197169C2 - Method for applying pupillography - Google Patents

Abstract

FIELD: medicine. SUBSTANCE: method involves measuring pupil area on images produced in darkness without background illumination being used. Pupil response coefficient is determined as pupil area ratio of the first image to the second one produced after acting with some irritator. EFFECT: higher accuracy in determining pupil area and response to irritation factors of various nature.

Description

 The invention relates to medicine and can be used to measure the size of the pupil and quantify the reaction of the pupil to various stimuli, including physiological ones.

 In areas of medicine such as ophthalmology, neurology, psychiatry, determining the reaction of the pupil to light is of greater clinical significance. When describing the clinical picture of the patient’s eye condition, during an ophthalmological examination using ophthalmoscopy or biomicroscopy on a slit lamp, a mandatory point is to state the state of the pupil’s reaction to light. In neurological and psychiatric practice, when describing certain diseases and conditions of a patient or subject, it is also necessary to determine the reaction of the pupil to light. Usually, generally accepted terms in medicine are used for this: the pupil’s reaction to light is live, or sluggish, or the complete absence of the pupil’s reaction to light.

 For a more accurate determination of the size of the pupil in the clinic, various pupillometry methods are used. With the help of pupillometry, physiological variants of pupil width, anisocoria magnitude, the nature of direct and friendly reactions of pupils to local exposure (directed light beam to the eye area), spontaneous fluctuations of the pupil diameter in normal and pathological conditions, eye convergence, the effect of various pharmacological agents on the pupil were studied, sound, color and other irritants. When evaluating the results of pupillometry, it is necessary to take into account significant physiological fluctuations in the width of the pupils depending on the illumination, the direction of the gaze associated with the convergence and tension of accommodation, the age of the patients, the general condition of the patients, the function of the endocrine system and other factors.

 In clinical practice, pupillometry is often performed using the Gaab pupillometer, which is a ruler with circles depicted in black on it with diameters from 1.5 to 8 mm in diameter. The diameter of each subsequent circle differs from the previous one by 0.5 mm. When using this method, a patient sitting opposite the doctor is asked to look into the distance. The doctor first brings the Gaab's measuring line to one eye, compares the diameter of the patient’s pupil with the diameter of the circle shown on the ruler, then also measures on the other eye (Ananin V.F. Objective methods for studying human vision. In the book Human Physiology, 1976, vol. 2, 4, p.693).

 In modern medicine, especially in its newest field related to the use of objective methods of provability, the so-called evidence-based medicine, the use of subjective methods related only to the judgment of a doctor should be considered insufficient. We cannot, from our subjective position, accurately reflect the change in the pupil’s reaction to light, and even the measurements made by different doctors can be very different. Therefore, for the accurate determination of these states, the need is to use measuring instruments, the so-called pupillographs.

 Pupillography is performed using a cinematopupillograph (Sokolova O.N. Ophthalmoneurology of the midbrain lesions. M., 1971) in two stages: at the beginning, the pupils are filmed on a highly sensitive film at a speed of 10 frames in 1 second, then at the second stage, using a special the device automatically carries out photo scanning of the pupil, analyzes the captured film frames and records the horizontal diameters of the pupils in the form of straight lines (pupillograms) on a highly sensitive unexposed film. A calibration scale is printed on each line, one division of which is equal to 1 mm. This scale is designed to determine the diameter of the pupil in SI units (i.e., in millimeters). Next, the final measurement is performed using a millimeter ruler (or for a more accurate measurement - a caliper).

 The disadvantages of this type of pupillography are the use of bright background lighting, which is necessary for filming the pupil, which creates non-physiological conditions for studying pupillary reflexes, difficulties in the dosage of light and the complexity of the entire measurement associated with developing the film, applying a calibration scale and others.

 Previously prof. Samoilov and Shakhnovich (Samoilov A.Ya. and Shakhnovich AR A new method of local pupilography and its application in physiology and clinic. - Vesti. USSR Academy of Medical Sciences, 1958, 4, p. 47) a method was proposed in which the background light is strictly dosed and located below the line of sight of the subject. At the same time, background lighting lamps make it possible to illuminate the iris well, almost without illuminating the retina. According to the authors, under these conditions, the width of the normal pupil is almost the same as in the dark.

 Further development of the technique led to the creation of other methods for measuring pupil width and determining its response to light - television pupillometry (Saladin JJ Television pupillometry via digital time processing // Invest Ophthalmology Vis. Sci. 1978, vol.17, p.702) and video pupilography ( Hamann KU et al. Videopupillographic and VER investigations in patients with congenital and acquired lesions // Ophthalmologica 1979, vol. 1778 p. 348).

 With these methods, the patient’s pupil of the patient observed by the doctor-researcher is transmitted via a video camera to a television monitor. To obtain video information, background dosed illumination of the eye is carried out, and then, to obtain information about the state of the reaction of the pupil to light, illumination of the pupil area. In this case, the measurement of pupil width is carried out using electronic computers (computers). The undoubted advantage of these methods, unlike the previous ones, is the speed of pupil width measurements, the lack of multi-stage in the work being done, the ability to store information.

 The disadvantages of all the above methods include the use of background illumination of the eye, although many authors do not use light from the pupil and retina. In this regard, it is impossible for the researcher to obtain information about the width of the pupil in the dark or in the dark. The second equally important point is associated with obtaining information only about the width of the pupil, about its horizontal dimensions. Although the horizontal size is more important for obtaining information about the reaction of the pupil to various stimuli, including light; it is in the horizontal meridian that the pupil width most fully changes. Nevertheless, there are conditions, more often associated with inflammatory eye diseases, when the pupil’s reaction to light may be weakened due to the presence of posterior synechia of the pupil edge of the iris with the lens, restricting or excluding pupil movements, and therefore the information obtained using the above methods on the state of the pupil's reaction to external stimuli may be inaccurate.

 The technical result of the invention is to increase the objectivity of evaluating the pupil for various stimuli, including physiological, which are light, and therefore the conditions for determining the size of the pupil.

 The implementation of the technical result is achieved by the use of a computer analyzer system based on the principle of computer analysis of eye images, and the actions that make up the essence of the present invention.

 The implementation of the proposed method is as follows.

 The entire examination procedure takes place in a dark room only with the minimum acceptable illumination of the computer monitor included in the set of the computer analyzer system, which is located behind the patient and accordingly does not create background illumination of the eye. The patient in a comfortable sitting position is asked to look into the distance at the proposed fixation point. Previously, for 5 minutes the patient is in this dark room to achieve pupil expansion. Next, the doctor-researcher makes a video recording (on a video camera or directly on a computer-analyzing system with observation of what is happening on the monitor) of the patient’s eye area. Usually for this an ophthalmologist uses a slit lamp for examination, but it may not be necessary to carry out the proposed method, since it does not allow the doctor to control the examination of the patient’s eyes, since the whole procedure is carried out in the dark. For video recording and broadcasting to the monitor, an ultra-sensitive video camera is used (for this, the proposed method used a black and white video camera with a sensitivity of 0.02 Lx) or any other device that allows you to get a contoured image of the pupil area. Thus, the doctor observes the patient’s eyes on a television monitor. The obtained images are stored in the memory of a personal computer in the form of a static image in graphic format, or the whole procedure can be recorded on a video camera or as a computer video clip in any digital video format. Next, dosed illumination of the pupil of the eye is performed, which remains unchanged in all patients (for healthy patients, the tolerated illumination power on a slit lamp, which does not cause blepharospasm, was determined to be 3.0 Lx). Dosing of illumination on a slit lamp is achieved by limiting the light beam from the illuminating lamp using horizontal and vertical diaphragms in the design of a slit lamp, or when using, for example, a flashlight handle. After illuminating the pupil area, we save the second static image. Thus, we get two static images or a video clip (video clip in digital format) of the pupil of the eye before and after its metered illumination. We perform similar actions in a dark room without lighting our eyes, if we check the pupil’s reaction to any stimuli, for example, the effectiveness of pharmacological agents with a mydriatic effect. Then the second image can be obtained after a certain period of time, predetermined.

 Immediately after receiving the images or at any convenient time, we calculate the pupil size as follows. The shape of the pupil may depend on the presence of posterior synechia for inflammatory eye diseases, on the presence of the exudative process of the pupil edge of the iris with the remains of the anterior capsule and the front surface of the intraocular lens (artificial lens of the eye) after cataract surgery, dislocation of the artificial lens in the posterior chamber of the eye and other factors. Accordingly, when the eye is illuminated or if an irritant is exposed to it (instillation of mydriatic agents, for example), the shape of the pupil can change differently across different meridians, that is, for example, in the horizontal meridian, the width of the pupil may be smaller or larger than in some or another meridian. Therefore, measuring the width of the pupil in the horizontal meridian should be considered insufficient for the above conditions of the eyes. For accurate measurement, it is proposed to use the determination of the area of the static image of the pupil using mathematical calculation of irregular geometric shapes. Counting irregular geometric shapes is done in two ways. Either the projection onto the image of the pupil of the program grid is used (meaning in the computer image conversion unit) containing irregular geometric shapes, and mathematical calculation of all shapes that fit into the pupil region, which is also carried out on different meridians. Or, which is currently usually used, the mathematical calculation of all the pixels that make up the image of the pupil, which in shape refers to irregular geometric shapes.

 Using a computer program, two values are obtained, and then we calculate the coefficient of the pupil’s reaction to light (or to another stimulus) as the ratio of the first value (pupil’s area in the dark) to the second value (pupil’s area under dosed illumination or exposure to some stimulus).

 This method was tested on 70 patients with various inflammatory eye diseases, including exacerbations of iridocyclitis of rheumatoid etiology (18 patients), 52 patients with artifact.

 For a visual demonstration of the differences of the proposed method, patients with exacerbation of iridocyclitis and the presence of posterior synechia along the pupil edge of the iris, deforming the pupil shape, were selected. Patients were prescribed the commonly used corticosteroid, antibacterial, anti-inflammatory drugs and various means to dilate the pupil in order to tear the posterior synechia from the anterior lens capsule and restore the round shape of the pupil. On the first day before the appointment of therapy using the presented method, the initial pupil area was calculated. Then on the following days, the pupil area was calculated and the pupil reaction coefficient for the action of various mydriatics was calculated (a 0.5% tropicamide solution and 1.0% atropine sulfate solution, which were prescribed in instillations 1 drop 3 times a day) were calculated. On the second day, 30 minutes after instillation, the following coefficients were obtained: 0.94 ± 0.02 and 0.81 ± 0.02 when exposed to tropicamide and atropine, respectively. When calculating the coefficients by the method of the ratio of the pupil width in the horizontal meridian, the following values were calculated: 0.99 ± 0.01 and 0.98 ± 0.01, i.e. the difference was not statistically significant. Therefore, the application of the proposed method made it possible the very next day to make a reliable conclusion that in the treatment of exacerbations of iridocyclitis with a pronounced adhesive process in the pupil of the iris, a 1.0% atropine solution has greater therapeutic effectiveness.

 Arthritic patients were divided into two groups depending on the method of cataract removal and implantation of different models of artificial eye lenses (hereinafter IOL). The first group included patients with extracapsular caratact extraction performed manually with aspiration of the lens masses with a syringe and implantation of an IOL made of polymethylmethacrylate (hereinafter PMMA). The second group consisted of patients in whom the cataract was removed by phacoemulsification with automatic aspiration of the lens masses and irrigation of a balanced solution and implantation of an IOL made of silicone. The calculation of the reaction coefficient of the pupil to the light of the proposed method was carried out on 3 days after surgery. The following coefficients were obtained: 1.14 ± 0.02 and 1.53 ± 0.03 in the first and second groups, respectively, i.e. in patients in whom cataract was removed by phacoemulsification with implantation of a silicone model of IOL, a more vivid reaction of the pupil to light was observed, expressed in subjective terms. Therefore, the proposed method made it possible to determine the degree of invasiveness of cataract surgery in different ways, as well as the degree of "biocompatibility" of IOLs made from different materials.

 The objectivity of the results obtained by the presented method can also be illustrated by the following clinical example.

 Example 1. Patient K., 67 years old, was hospitalized in the 1st surgical department of the Research Institute of Eye Diseases. An extracapsular cataract extraction with implantation of an intraocular lens made of polymethylmethacrylate was performed for mature left eye cataract. The day after the operation, after an ophthalmological examination, the reaction of the pupil to the light was determined using the method that was used as a prototype, i.e. the first image was obtained with illumination of the eye area, and the second image after exposure of the pupil area, and the ratio of the pupil widths measured in the horizontal meridian before and after exposure of the pupil, it was determined that the ratio was 1.0. In other words, a conclusion was drawn that the reaction of the pupil to light, determined in a known manner, is absent. When measuring the reaction of the pupil to light by the proposed method, i.e. by determining the pupil area by counting the irregular geometric shape of the pupil by mathematical determination of all the pixels making up the pupil image, the ratio of the pupil areas before and after exposure was determined to be 1.08. From this it was possible to conclude that the reaction of the pupil was saved in other meridians and it was reduced due to the presence of an inflammatory fibrinous-exudative adhesion process between the iris and the artificial lens, which required the use of medications that dilate the pupil and active anti-inflammatory therapy as a therapeutic treatment. If the pupil’s reaction coefficient of 1.0, determined by the prototype method, was taken as a diagnostic criterion, then urgent surgical intervention in the eye would have to be recognized as medical treatment, since the absence of a pupil’s reaction to light is a clinical sign of the so-called pupil block leading to an acute attack of glaucoma, which would be a gross diagnostic error.

 Thus, the proposed method allows more objectively, and therefore more precisely, to carry out pupillometric studies.

Claims (1)

 The method of pupillography, which includes the formation of images of the pupil on a television monitor by video recording before and after exposure to light or pharmacological stimuli and determining the pupil reaction to them, characterized in that the acquisition of pupils is carried out in the dark without background illumination of the eye, and when determining the reaction pupils for stimuli use the ratio of the measured values of the pupil areas in the first and second images, while the measurement of the pupil area is carried out by a pair of irregular geometric shapes in its various meridians.