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Lecture notes, cheat sheets
Eye diseases. Technique for examining the condition of the eye (part II) (lecture notes)
Directory / Lecture notes, cheat sheets Table of contents (expand) LECTURE No. 4. Methodology for examining the condition of the eye (part II) 1. Examination of the eye in transmitted light The deep media of the eye (the lens and the vitreous body) are examined in transmitted light using an ophthalmoscope. The light source (matte electric lamp with a power of 60100 W) is placed on the left and behind the patient, the doctor sits opposite. Using an ophthalmic mirror placed in front of the researcher's right eye, a beam of light is directed into the pupil of the examined eye from a distance of 2030 cm. The researcher examines the pupil through the opening of the ophthalmoscope. The rays reflected from the fundus (mainly from the choroid) cause a red glow of the pupil, which is especially clearly observed if it is dilated. In cases where the refractive media of the eye are transparent, the reflex from the fundus is uniformly red. Various obstacles in the way of the passage of the light beam, i.e., turbidity of the media, delay part of the rays reflected from the fundus of the eye. Against the background of a red pupil, these opacities are visible as dark spots of various shapes and sizes. Changes in the cornea can be easily excluded when viewed using lateral illumination. Opacities of the lens and vitreous body are differentiated quite easily. The relative depth of opacities can be determined by inviting the patient to look in different directions. Dark spots against the background of a red pupil, associated with clouding of the lens, move relative to the center of the pupil, naturally, only when the eyeball moves. Those located in the anterior layers of the lens are displaced in the direction of movement of the eye, located in the posterior sections in the opposite direction. Opacities in the anterior parts of the lens are quite clearly visible in side illumination. Vitreous changes look a little different. Most often they resemble dark strands, flakes that continue to move after stopping the gaze. With a significant change in the vitreous body due to inflammation of the vascular tract or hemorrhage, the reflex from the fundus becomes dull or absent. 2. Ophthalmoscopy The fundus of the eye is examined using the ophthalmoscopy method, which is one of the most important methods for studying the organ of vision, allowing one to judge the condition of the retina, its vessels, choroid and optic nerve. The most widely used ophthalmoscopy method is the reverse. The study is carried out in a darkened room. An ophthalmoscopic mirror is placed in front of the right eye of the researcher sitting at a distance of 4050 cm from the subject. The light source is positioned behind and to the left of the patient, as in a transmitted light examination. After obtaining a uniform glow of the pupil, the researcher places a magnifying glass (usually 13,0 diopters) 78 cm in front of the patient’s eye, resting his finger on his forehead. It is necessary to ensure that the researcher’s pupil, the mirror hole, the center of the magnifying glass and the pupil of the subject are on the same line. A true reverse image of the fundus, magnified approximately 5 times, is seen hanging in the air at a distance of about 7 cm in front of the magnifying glass. To examine a larger area of the fundus, if there are no contraindications, the patient’s pupil is first dilated with a 1% solution of homatropine or a 0,25% solution of scopolamine. Examination of the fundus begins with the most visible part of the optic nerve head. Since it is located medially from the posterior pole, during ophthalmoscopy it can be seen only when the eyeball is rotated 1215° to the nose. Against the red background of the fundus, the optic disc appears as a yellowish-pink, slightly oval formation with clear boundaries. In children under one or two years of age, the disc is often grayish. The blood supply to the nasal half is better, so its color is brighter. In the center of the disc, due to some divergence of the fibers, a whitish vascular funnel is formed (physiological excavation). The color, contours and tissue of the optic nerve head change due to inflammatory and congestive phenomena, optic nerve atrophy, damage to the choroid and many general diseases, in particular blood vessels, etc. Pay attention to the condition of the retinal vessels emerging from the middle of the optic nerve head, their caliber, color, width of the reflex strip located along the lumen of larger arteries and eyelids. The caliber of blood vessels (in a healthy child in the first months of life the ratio of the caliber of arteries and veins is 1:2, at an older age 2:3) changes both in a number of eye diseases and in many general diseases, in particular arterial hypertension, endarteritis, kidney diseases, diabetes, etc. Functionally, the most important part of the retina is the macula. It is better to examine it by first dilating the pupil. The patient must look at the ophthalmoscope mirror. During reverse ophthalmoscopy in older children, the macula appears as a dark red oval, surrounded by a shiny stripe of macular reflex, formed due to thickening of the retina along the edge of the macula. In the center of the macula, a shiny light dot is usually visible - a reflex from the central fovea, the foveal reflex. Newborns and children of the first year of life do not have macular and foveal reflexes. In the area of the macula, the retinal vessels are not visible or sometimes extend somewhat to its periphery. The periphery of the fundus up to the dentate line is examined with different directions of the patient's gaze. The pattern and color of the fundus largely depend on the pigment content in the retinal pigment epithelium of the choroid. More often, the fundus is uniformly colored red, and the vessels of the choroid are clearly visible on it. The less pigment in the fundus, the lighter it appears due to the translucency of the sclera. With age, the tone of the fundus of the eye changes from pale pink to dark red. A thorough study of changes in the fundus of the eye is carried out using direct ophthalmoscopy. To do this, they resort to using an electric ophthalmoscope equipped with its own lighting system. The refractive media of the eye of the subject (a magnification of 13-15 times is achieved) serve as a magnifying glass. The device is powered from the mains through a step-down transformer. It is more convenient to conduct an examination with a dilated pupil. Direct ophthalmoscopy allows the researcher to get as close as possible to the patient's eye (by 24 cm), until the fundus becomes visible through the opening of the ophthalmoscope. The ophthalmoscope is held so that the index finger of the researcher lies on the disk with corrective glasses. By rotating the disk, a lens is placed that gives the sharpest image of the fundus. Examination of the right eye of the patient is carried out by the right eye of the oculist, respectively, the examination of the left eye is also carried out. Direct ophthalmoscopy makes it possible to see such subtle changes, the nature of which remains unclear with reverse ophthalmoscopy. Direct ophthalmoscopy makes it possible to see such subtle changes, the nature of which remains unclear with reverse ophthalmoscopy. Due to a significant increase and the existing binocular attachment, it is possible to use it for stereoscopic examination of the fundus, which is especially necessary when differentiating subtle changes in the optic nerve head. To examine the fundus, an ophthalmochromoscope is used, which allows one to examine the fundus in light of different spectral compositions (red, yellow-green, purple, etc.). A polarizing photo-ophthalmoscope makes it possible to examine and photograph the fundus of the eye in polarized light. Registration of changes can be carried out by a photographic camera and an ophthalmic (retino) photo. 3. Biomicroscopy For a detailed study of the transparent structures of the eye and its membranes, the biomicroscopy method is used. It consists in using a narrow, sharply limited homogeneous beam of light, the focus of which can be placed at different depths and in different parts of the eye. Such a beam of light allows you to create a pronounced contrast between the illuminated and unlit areas of the eye, to obtain a thin section of its transparent tissues. The study of the obtained sections is carried out using a binocular microscope. For biomicroscopy, a slit lamp is used, in which a special freely moving illuminator is mounted on a common axis of rotation with the microscope. This device allows you to consider very minor changes in the cornea, lens, vitreous body, in the fundus. Due to the fact that the light beam crosses the transparent tissues from front to back at different angles, it is easy to determine the depth of the changes and their nature. For example, biomicroscopy of the cornea clearly shows even point defects in its epithelium, especially after staining with fluorescein, it is easier to judge the depth of the location of opacities, infiltrates, foreign bodies, we can confidently talk about the superficial or deep nature of vascularization. With the help of a slit lamp, you can see gentle changes in the endothelium of the cornea, its edema, precipitates, consider a suspension of blood cells in the moisture of the anterior chamber, the appearance of the vitreous body (hernia) in it after injury, surgery. No less valuable data is obtained when examining the iris under a microscope. In cases of pathology, it can be seen dilated and newly formed vessels, areas of atrophy, the appearance of tubercles, posterior synechia, etc. The role of biomicroscopy in studying the state of the lens and vitreous body is invaluable. It allows you to determine the severity, localization of lens opacities, to judge the degree of maturity of the cataract, its origin, the state of the capsule. When examining the vitreous body, they judge the nature of the changes in it, the type of destructive disturbances, etc. This method provides great opportunities for studying pathological changes in the retina, choroid, and optic nerve. For example, subtle changes in the macular area in some types of degeneration can only be seen with a slit lamp. At the same time, studies in redless light and in light of various intensities are expedient. Biomicroscopy of the eye in young children is possible only with the help of a manual slit lamp, and sometimes only during drug-induced deep sleep or under anesthesia. Author: Shilnikov L.V. << Back: Technique for examining the condition of the eye (part I) (External examination of the eye in natural light. Side lighting method. Examination using a combined method) >> Forward: Technique for examining the condition of the eye (part III) (Gonioscopy. Tonometry. Tonography. Echoophthalography. Exophthalmometry)
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