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Examination techniques for evaluating visual functions
III. To test the basic knowledge/skills level, do the two tasks below.
V. Learning content
Diagnostics algorithm for
VI. The tasks below help you check your knowledge.
VII. Brief work guidelines for the workshop activity
Process chart of the workshop on
Techniques of ocular examination
II. Objective (general)
III. You are supposed to do the two tasks below to check your basic level of knowledge and skills
General ocular inspection
In the examination of anterior eye chamber
Transmitted light examination
MINISTRY OF HEALTH OF UKRAINE
DONETSK M.GORKY STATE MEDICAL UNIVERSITY
Department of Ocular Diseases
Donetsk - 2008
Ocular Diseases: Manual / Pavlyuchenko K.P. et al. – Donetsk, 2008.- pp.
According to Higher Education Law of Ukraine, the priority of the state policy is to facilitate integration of Ukrainian higher school into the world educational system still preserving and developing national academic achievements and traditions.
Decision of 24.04.2003 issued by the Ministry Board of the Ministry of Education and Science runs: “Introducing ECTS into the system of higher education of Ukraine is a key requirement under Bologna Declaration of 1999 and one of the prerequisites for entering Ukraine into Europe”.
The program to implement Bologna Declaration requirements has been approved by the Ministry of Education and Science resolution No 49 of 23.01.2004.
The Manual has been made according to ECTS conversion plan for medical students. It is an instructive textbook on ocular diseases for students of III-IV accreditation level medical universities. Supplement 1 (p. 168) shows a list of workshop topics for a four-year medical students majoring in ocular diseases with Donetsk National Medical University for 2008-2009 and includes 3 conceptual modules. Every workshop is followed with a final test on the topic studied. Final workshop is an all-topic modular final test. Пособие рекомендовано в печать 21.02.2008г. Ученым советом ДонНМУ, протокол заседания №1.
1. Sergienko N.M., corresponding member of the Academy of Medical Sciences and National Academy of Sciences of Ukraine, Dr Sci (Medicine), professor, head of ocular diseases department with NMAPE named after P.L.Shupyk
2. Zhaboyedov G.D., corresponding member of the Academy of Medical Sciences, head of ophthalmology department with A.A.Bogomolets National Medical University (principal ocular department in Ukraine).
3. Bezdetko P.A., head of ocular diseases department with Kharkov Medical University, Dr Sci (Medicine), professor.
Donetsk M.Gorky Medical Unoversity
Examination techniques for evaluating visual functions 6
Techniques of ocular examination 21
Diseases of the anterior segment of the eye 40
Lens disorders. Examination 60
Glaucoma. Emergency treatment of acute glaucoma 78
Refraction abnormalities, accommodation disorders and strabismus 97
Ocular symptoms in systemic diseases. Eye neoplastic diseases 116
Ocular traumas. Emergency treatment of eyeball burns and injuries. 134
Reference answers 155
Recommended references 156
(into the Manual to ocular diseases )
The Manual is an abridged theory to be studied by 4-year medical students in the course of “Ocular diseases”.
The topics covered here are relevant for a future physician. Visual function disorders revealed in examination can help diagnose a number of internal diseases. In a number of cases good knowledge of causes leading to visual function abnormalities can help prevent disease development Ocular examination skills are essential in diagnosing neurologic disorders, ENT pathologies, liver disorders, avitaminoses, infectious and invasion diseases.
Close anatomical and physiological connection between human eyes and the whole body, various systems and organs explains ophthalmologic manifestation of systemic diseases (diabetes mellitus, essential hypertension, kidney diseases).
A physician needs to know ophthalmoscopic techniques that help interpret a picture of the eye fundus obtained in ophthalmologic examination.
In view of high morbidity and potentially irreversible blindness caused by diseases included in “The List of Emergency States” of QC (Qualification Characteristic), other important topics are glaucoma, emergency treatment of ocular diseases, cataract, etc.
Actually everybody needs glasses this time or other, therefore a future physician has to acquire knowledge about refraction abnormalities and vision correction techniques.
Eye trauma is a topical problem occurring quite often in industry, agriculture, everyday life, both with grown-ups and children. Eye trauma is an emergency state that requires special attention and is of particular interest for a future general practitioner.
Every topic is completed with tasks supplemented with reference answers, which to our opinion will help master the theory thoroughly.
The authors hope that the Manual that has been written as a student-oriented handbook will help study the theory and master it in the practical work of a physician.
I. Relevance of the topic. The subject is relevant to a physician in the medical faculty since visual function disorders revealed in examination can help diagnose a number of internal diseases, congenital eye diseases and ocular diseases in infants. Good knowledge of causes leading to visual function abnormalities in a number of cases helps to prevent disease development. Testing of color perception (chromatic sensitivity), central and peripheral vision acuity is necessary for diagnosing a number of brain and liver diseases, as well as avitaminoses (dark adaptation abnormalities).
Study and think over the objectives of the workshop on eye functions and examination methods.
II. General objective: to be able to examine basic ocular functions, analyze the findings to determine probable correlation with general diseases and offer preventive measures, if possible.
A patient with a chronic liver disease complained to the physician about bad orientation at twilight and was referred to ophthalmologist. Objective examination of the patient’s eyes revealed no structural changes. Byelostotsky adaptometer test showed a moderate reduction in dark adaptation. The ophthalmologist suspected functional hemeralopy in the patient.
1. What retinal receptors are responsible for twilight vision?
2 Can the patient’s liver disease be the cause of hemeralopy?
3. What other general causes can result in twilight vision abnormalities? Why?
A patient with a pituitary tumor pressing upon the optic chiasm in its central part.
Question: What changes can develop in the patient’s filed of vision?
Reference answer to task 1.
2. Yes, it can.
3. Gastrointestinal disturbances, liver disorders (endogenous A avitaminoses), A vitamin nutritional deficiency, since vitamin A participates in visual pigment synthesis. Twilight vision abnormalities can also be caused by nervous cerebropathy, some metabolic disturbances, intoxication with industrial toxic substances (mercury, lead, etc.), and other factors leading to vision impairment.
Reference answer to task 2.
The chiasm central parts accommodate the converging fascicles from internal halves of the retina of both eyes. Therefore the temporal halves of the vision field will be lost.
After the basic knowledge has been acquired, you may proceed to study the following:
Supplemental references to improve the original level of knowledge:
Theory used as a basis for target activities.
1. Physiology of visual perception. The structure of light perception apparatus, retina blood supply. The role of conductive pathways and visual centers in the act of vision. Daytime, twilight and night vision. Qualitative and quantitative methods for light perception assessment. The operation of adaptometer. Types of visual perception, incidence of pathological changes. Hemeralopy. Basic issues of diagnostics, occupational screening, disability and recruitment medical examination with twilight vision problems.
2. Central vision. Measurement units. The methods of testing vision acuity with charts, objects and special charts for children. Age standards of vision acuity with children. The principle of chart arrangement . The causes of reduced visual acuity in disease diagnostics, occupational selection, disability and recruitment medical examination.
3. Peripheral vision. Control and instrument study methods. Campimetry testing. Normal borders of the vision filed. The importance of peripheral vision testing in the diagnostics of pathologic processes in the eye and the CNS. The importance of peripheral vision testing in occupational selection, disability and recruitment medical examination.
4. Color vision. Basic colorimetric parameters. Rabkin’s polychromatic charts.
Color vision defects. Basic principles of occupational screening and disability medical examination with color vision defects.
Study the logic structure graph for the topic:
Logical structure graph for
“Examination techniques for evaluating visual functions”
Basic reference sources:
Additional reference sources:
After the basic knowledge has been acquired, use the following guiding procedure to study visual functions and the testing methods; check your academic level to do the tasks.
V. Guiding procedure (GP)
The guiding procedure used to tackle the tasks and manage the patients is presented in the logic structure graph as a sequence of student activities in testing visual functions.
«Examination techniques for evaluating visual functions»
Acquired color blindness
Importance of the technique
3. Examination of color perception with Rabkin chart
Congenital color blindness
Anomalous color vision
Human eye is a unique organ with specific operation capacities specified by its complicated structure on the one side and a variety of functions on the other, which enable the human eye to perceive as complete as possible the impressions of light energy reflected by outside objects.
Patient complaints contain data indicating vision disorders: 1) central vision - complaints of visual impairment; 2) peripheral vision – complaints of “veil” and “spots”; 3) accommodation - far sight vision impairment; 4) light and dark adaptation – impaired twilight vision; 5) color perception – inability to appreciate certain colors (can be congenital or acquired); 6) refraction – patient needs glasses or contact lenses correction to improve the sight, or tit may be the complaint of reduced visual acuity if glasses or lenses have never been used before; 7) binocular vision – complaints of inability to perform skilled movements while working with tiny objects.
A number of objective evaluation techniques are used to detect central and peripheral vision disorders.
Visual acuity evaluation is needed for central vision quantitative estimation. It is performed 5m away from a patient in a dark room with a visual acuity chart (Golovin-Sivtsev, Orlova, Shevalev charts). The eyes are examined separately; the other eye is covered with a non-transparent shield. The patient is shown lines of letters in succession from bigger to smaller ones. Patient’s visual acuity is determined by the smallest perceptible symbol. Knowing the distance from the chart and the distance of normal visual acuity for the line perceived, one can easily determine the patient’s visual acuity by Donders equation , where V - Visus – visual acuity, d – testing distance and D - distance of a well-perceived line with normal visual acuity. Normal visual acuity is identified with 1,0 and corresponds to the 10th line at a 5m distance.
Patients with low visual acuity unable to recognize even the first line are shown the chart or Polyak’s optotypes (a number of white stripes against a black background) at a closer distance, or offered to recognize the number of the tester fingers shown against a dark background. In this case, visual acuity is calculated accordingly. Patient’s visual acuity is evaluated as 0,02 if he can see only the first line from a 1m distance or 0,04 if he can see it from a 2m distance, and so on. When formal vision is absent, the light perception and projection ability are evaluated. In a dark room, a source of light is located behind and to the left of the patient. Ophthalmoscope mirror directs the light beam into the patient’s eye from different points. The patient has to say if he can see the light and where from. Such vision is identified as proectio lucis certa, i.e . light perception with right light projection. Light perception with wrong light projection is identified as proectio lucis incerta. If the patient is not able to discriminate between light and dark, his visual acuity equals 0.
Evaluation of visual acuity is the beginning of an ocular patient examination as vision disorders are very common and critical subjective symptoms. Visual acuity deviations obviously point to the character and behavior of a disease.
To evaluate peripheral vision it is essential to quantify the visual field embraced, with the eyes, head and a certain point fixed.
Each of the eyes has its own limits of visual field. The limits correspond to the limits of optically active retina and are bounded by protruding parts of the face: nose bridge, eye socket upper edge, cheeks. Normal visual field borders from the central point of fixation are: 90 outwards, 70 up and outwards, 50-55 upwards, 60 up and inwards, 55 inwards, 50 down inwards, 65-70downwards, 90 down outwards. Individual deviations within 5-10 are possible.
There are several techniques to determine visual field limits.
There is a finger technique, the simplest but not very accurate, only efficient for gross lesions of visual field. Patient and physician are seated 5m away facing each other so that the light is behind the patient. The patient closes his right eye while the physician closes his left eye, and vise versa when the right eye is examined. It is important that the examiner should have normal limits of visual field. The examiner does some minor movements with his fingers or hand along the center line between him and the patient gradually nearing the visual filed center. The patient has to spot the moment when the doctor’s hand appears in his visual field. If he catches the moment simultaneously with the doctor, it means that his visual filed has normal borders in this direction. Similarly it is repeated at 4-8 meridians. Thus it is possible to evaluate the limits of visual field.
Accurate evaluation of visual field can be done by projecting field limits on a spherical surface. Visual field examination performed on a desk perimeter or all-purpose projection perimeter is called perimetry. For perimeter examination, the patient seated in front of the instrument looks at the white fixation point in the centre of perimeter arc. The examiner stands at the perimeter side and moves an object along the arc (periphery to centre). The patient has to catch the moment when the moving object appears. Tests are repeated every 15 at the meridians. The object dimensions are chosen within 3-10mm according to the patient vision acuity.
Visual field deviations appear as missing areas (scotoma). Campimetric techniques are advisable for accurate examinations. The patient is seated 1m away from a 2x2m black board (campimeter). A white symbol in the centre of the board is a fixation point. For testing, a white-color object (1-3mm circle) is used. The circle is moved along horizontal line intersecting the fixation point in the outside half of the visual field from periphery to the centre or vice versa. The moment when the object disappears is recorded. Then visual field limits are evaluated vertically. Eyes are tested separately.
Rabkin charts are used for color vision examination. The charts are called polychromatic as dichromatic patients discriminating color strength and brightness rather than color hues are not able to read the chart correctly. The charts are made of variously colored circles of different brightness. Circles are located so as some of the circles of similar color make up a numeral or figure against the background of differently colored circles. Tests are performed at daylight illumination. The patient is seated his back to light. He looks at the charts 1-1.5 m away, the time of exposition is 10s. Trichromatic patients discriminating color hues can easily read the chart numerals while for dichromatic patients the task is rather complicated and even impossible.
Dark adaptation measurement is called adaptometry and is performed with a high-accuracy adaptometer.
Adaptometer enables to determine the curve for light sensitiveness rise during a long-time (60min) stay in the dark, to separately investigate peripheral or central retina light sensitiveness for short-time expositions (3-4min), and evaluate bright light sensitiveness of a dark-adapted eye.
Before testing dark adaptation, the patient has to look at a brightly and uniformly lighted screen for 20 minutes. Then the patient enters a complete darkness and during this stay his light sensitiveness is evaluated. The patient is asked to look at a mildly lighted screen every 5 minutes. Brightness of the illumination is gradually reduced as light sensitiveness goes up. Examination is carried out during an hour. Light sensitiveness increases quickly in the dark and reaches its maximum within 40-45 minutes. Notable rise of dark adaptation occurs within the first 20 minutes. Dark adaptation process is usually presented by a curve. Time of dark stay in minutes is marked on the horizontal axis, and light sensitiveness thresholds are on the vertical axis.
To diagnose the character of ocular lesions, lesions of conduction pathways or cortical centers, it is essential to interpret visual examination findings correctly.
Central vision acuity is the major indicator of eye condition. Reduced vision acuity may be caused by lesions occurred in any section of the eyeball, conduction pathways or cortical centers.
Change of visual field can appear as the field narrowing or the loss of certain areas. Concentric narrowing is observed with retina pigmental degeneration, post-neuritis optic atrophy, congestive disk and other optic nerve lesions. Narrowing of visual field can develop in a sector-wise manner. Such narrowing is usually observed with glaucoma, certain types of optic nerve atrophy, embolism in one of the retina central artery branches.
Illnesses affecting upper parts of visual pathways - chiasm, optic tract, subcortical ganglia, corresponding parts of occipital lobe cortex- are accompanied by specific changes of visual field. In case of chiasm, its internal parts are usually affected. It happens due to pituitary body tumors, base of brain tumors, an inflammatory process, etc. This is accompanied by lesions of intersecting nerve fibers from both retina nose parts and bitemporal crossed hemianopsia i.e. temporal parts of visual fields in both eyes are lost. Binasal hemianopsia caused by lesions in chiasm of non-crossing fibers from both nerves is quite rare and suggests two symmetrical lesions outwards the chiasm center.
When optic tracts are affected, equilateral hemianopsia develops. With lesions of left tractus opticus in the left eye, non-crossing fibers maintaining the temporal part of retina, that is the right nasal part of the visual field, are lost. In the right eye, crossing fibers that maintain the retina nasal part, i.e. the right temporal part of the visual field are lost. With lesions of the right tractus opticus, left part of the visual field in both eyes is lost. When only a part, e.g. a half of tractus opticus is affected, a quarter of the field rather than a half of it is lost in each eye. This is called quadrantic hemianopsia.
Topical lesion of the visual field is called scotoma. Scotoma, known as a blind spot, always exists in the normal field of vision and corresponds to optic nerve projection.
Positive scotoma is a kind of lesion of the visual field that a patient perceives as a dark, sometimes colored spot partially covering the object looked at. Positive scotoma usually develops with retina lesions or optic nerve inflammation.
Negative scotoma is not perceived by a patient but is usually revealed during examination of some areas of the visual field. Negative scotoma prevails when visual pathways are affected. With absolute scotoma white and colored objects are not perceived in some area. Relative scotoma means that a white object looks less distinct. Scotoma can be central or peripheral according to its location.
With central scotoma there is an area in the field of vision that corresponds to a blind spot. Causes of central scotoma are various: lesions of retina, choroid, papillamacular fascicle of optic nerve, macular hemorrhage. Bilateral central scotoma more than often is associated with diseases of optic nerve trunk.
To interpret color perception disorders it is essential to know that dyschromasia (a congenital color vision disorder) is characterized by various intensity and behavior. A person perceiving all three colors is called trichromatic, he who is able to perceive two colors is called dichromatic and a perceiver of one color is called monochromatic. The highest degree of defected color perception is monochromatism that features the absence of components differentiating light wavelengths. In this visual defect, objects of various colors appear as variations of a gray color (white to black). With monochromatism the vision is always very bad as retina cones are affected.
Dichromatism is of three types: protanopia, when the red component is lost; deuteranopia, when the green component is lost, tritanopia, when the violet component is lost. Dichromatism prevails in males.
Congenital red blindness is called protanopia. There are people with weak color perception. This phenomenon is called anomalous trichromatism.
Dark adaptation defects may manifest as a higher threshold of stimulation, i.e. light sensitivity even after a long stay in the dark remains reduced and never reaches its normal value. Another manifestation is a slower adaptation when the rise of light sensitivity is later than normal but gradually reaches normal or almost normal value. The above defects are common in combination. Both defects result in reduced light sensitivity.
Reduced dark adaptation is called hemeralopy. Hemeralopy is a symptom of some retina diseases (pigmental degeneration, retinitis, chorioretinitis, retinal detachment) or optic nerve diseases (atrophy, congestive disk), as well as bad shortsightedness. Here hemeralopy is caused by irreversible anatomic defects: rods and cones damage. Reduced dark adaptation is an early sign of glaucoma. It also develops also with liver diseases.
|Ministry of public health of ukraine ministry of education, science, youth and sports of ukraine||Ministry of health of ukraineministry of health of ukraine|
|Ministry of Health of Ukraine||Ministry of health of ukraine|
|Ministry of Health of Ukraine||Ministry of Health of Ukraine|
|Ministry of Health of Ukraine||Ministry of Health of Ukraine|
|Ministry of health of ukraine||The Health Ministry of Ukraine|
|Ministry of Health of Ukraine|