Basic Ophthalmology (Paperback, 5th Revised edition) / Author: Renu Jogi ; ; Ophthalmology, Clinical & internal medicine, Medicine, Books. This book deals with the basic concepts, fundamentals and recent advances in ophthalmology. It provides guidance on the latest diagnostic. Download pdf version of Renu Jogi - Basic Ophthalmology, 4th Edition [ATTACH] link for download >.
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Basic. Ophthalmology. FOURTH EDITION. Renu Jogi. MBBS MS. Ex Associate Professor. MGM Medical College, Indore (MP). Pt. Jawahar Lal Nehru Memorial. R Jogi - Basic Ophthalmology, 4th echecs16.info - Ebook download as PDF File .pdf ), Basic Ophthalmology. Basic Ophthalmology FOURTH EDITION. Renu Jogi. POLITICS THE BASICS 4TH EDITION This highly successful introduction to the world of politics has Po Interchange 4th Edition Level 1 Student Book.
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Review This Product. Welcome to Loot. Checkout Your Cart Price. Repayment Terms: Special order. This item is a special order that could take a long time to obtain. Description Details Customer Reviews The fifth edition of this book has been fully revised to present undergraduate medical students with the latest information in the field of ophthalmology.
Beginning with an overview of embryology and anatomy, the next chapters explain the physiology and neurology of vision and examination of the eye. Each of the following sections provides in depth detail on each section of the eye, and the step by step diagnosis and management of associated disorders and diseases.
The final chapters discuss general therapeutics, causes and prevention of blindness, and ophthalmic instruments. The comprehensive text is highly illustrated with more than clinical photographs and diagrams.
Key Points Fully revised, new edition presenting students with latest information in ophthalmology Covers all sections of the eye and associated disorders and diseases Highly illustrated with more than images and diagrams Previous edition published in General Imprint: October Authors: Renu Jogi Dimensions: Paperback Pages: Review This Product No reviews yet - be the first to create one!
Herpes zoster 3. Thickness—The thickness of the periphery of the cornea is 0. Superficial staining—A drop of fluorescein is instilled in the conjunctival sac. Herpes simplex 2. Curvature and colour—There is thinning. It marks the areas of denuded epithelium due to abrasions. Absolute glaucoma 5. It is measured by the pachymeter. Staining of the cornea by vital stains a.
Alcian blue—It stains only excess mucus. Following alcohol injection in the Gasserian ganglion Trigeminal neuralgia vi.
It is 0. Deep staining—After instilling the dye the lids are kept closed for about 5 minutes. It stains the diseased or devitalized cells red. It is available as drops or disposable strips. Acute congestive glaucoma 4. Sclera i. Leucomatous corneal opacity 6.
Vessels—Ciliary injection and nodule is seen in episcleritis and scleritis. Anterior Chamber i. Iris i. Heterochromia iridium Colour—Heterochromia iridium—The two irides are of different colour. It is estimated by the position of the cornea and plane of the iris. Depth—The normal depth is 2. Position—Plane of the iris is noted. Pattern—Ill-defined or loss of pattern chronic iridocyclitis iii. Tremulousness Iridodonesis —Excessive movements or tremors of iris are seen best in a dark room with oblique illumination when eyes move rapidly.
Examination of the Eye 29 Posterior synechia iv. Pathological i. Pupil Size—Normal size of the pupil is mm Anisocoria—Unequal size of both the pupil is called anisocoria Miosis—The pupil is small and constricted Mydriasis—The pupil is dilated Miosis—The pupil is small and constricted due to the action of sphincter pupillae muscle.
General—Morphia 3. Pharmacological i. Afferent pathway—The optic nerve Centre—Edinger-Westphal nucleus in midbrain third nerve nucleus. Argyll-Robertson pupil—Accommodation reflex is retained but light reflex is lost.
The decussation of the nerve fibres in the midbrain explains the mechanism of the indirect reflex. Pupillary reactions reflexes a. Third cranial nerve paralysis—Trauma. Near reflex accommodation reflex —Contraction of the pupil occurs on looking at a near object. Indirect consensual light reflex—If light enters an eye. Irritation of cervical sympathetics.
Efferent pathway—The oculomotor nerve. Pathway of the pupillary light reflex ii. Psychosensory reflex—A dilatation of the pupil occurs on psychic or sensory stimuli. Direct light reflex—If light enters an eye. Light reflex i. Posterior surface of cornea Concave surface Erect virtual image c. Purkinje-Sanson images. Purkinje-Sanson images—When bright light falls obliquely on the eye dilated pupil in a dark room images are formed by the a. Lens i. Colour—Jet black—Normal. Posterior surface of lens Concave surface Inverted real image In clear transparent lens—There is presence of all 4 images.
In aphakia—There is absence of 3rd and 4th images. The lens is tilted causing astigmatism and uniocular diplopia seeing double objects. Morgagnian cataract Dislocation into anterior chamber Posterior dislocation Yellowish—Shrunken lens in hypermature cataract. Position—Dislocation occurs commonly in lower part of the vitreous or in the anterior chamber due to complete rupture of the zonule as following trauma.
In opaque lens—There is absence of 4th image. It is of unknown etiology. Adie pupil—It presents as unilateral dilated pupil usually in young women.
Anterior surface of lens d. Anterior surface of cornea b. The pneumatotonometer 4. Disadvantage—There may be error due to ocular rigidity. There are 3 more weights available 7. Method—The patient is asked to look down. Lymph nodes—Preauricular lymph nodes may be enlarged. The Goldmann applanation tonometer 2.
Digital Tension Principle—The intraocular tension is estimated by palpation of the eyes with fingers.. Method— The cornea is anaesthetized with suitable local anaesthetic.
The Perkins tonometer 3. The sclera is palpated through the upper lid beyond the tarsal plate. The MacKay-Marg tonometer. Applanation Tonometer It is a more accurate method. The cornea is flattened by a plane surface. Schiotz Tonometer Principle—The depth of indentation of the cornea is measured. The tension is estimated by the amount of fluctuation. This is more accurate since the pressure values recorded are uninfluenced by scleral rigidity.
Advantages—It is cheap. It states that for an ideal. Six applanation tonometers are currently in use namely. Digital tension—It is assessed by fluctuation method. The air-puff tonometer 5. Patient is seated in front of a slit-lamp. The intraocular pressure is determined by multiplying the dial reading with Biprism is then advanced until it just touches the apex of the cornea. Pneumatic tonometer—The cornea is applanated by touching its apex by a silastic diaphragm covering the sensing nozzle which is connected to a central chamber containing pressurised air.
Method 1. The applanation force against the cornea is adjusted until the inner edges of the two semicircles just touch. The Microelectronic Tono-pen Goldmann applanation tonometer—It is the most popular and accurate tonometer. This is the end point.
It is small and easy to carry. At this point two fluorescent semicircles are viewed through the prism. There is a pneumatic-to-electronic transducer which converts the air pressure to a recording on a paper-strip from where IOP is read. Examination of the Eye 33 Goldmann applanation tonometer Schiotz tonometer 6. It consists of a double prism mounted on a standard slit-lamp. The cornea and biprisms are illuminated with cobalt blue light from the slit-lamp. The prism applanates the cornea in an area of 3.
Perkins hand-held applanation tonometer—It is same as above except that it does not require a slit- lamp and it can be used even in supine position.
Microelectronic Tono-pen—It is a computerised pocket tonometer. Direct gonioscopy with goniolenses—They provide a direct view of the angle. Types of Gonioscopy i. Binocular loupe—A stereoscopic effect is obtained and the depth of opacities can be assessed.
The central part of cornea is flattened by a jet of air.
Indirect gonioscopy with gonioprisms—The rays are reflected by the mirror and the angle of anterior chamber is seen. Zeiss four mirror gonioscope. Goldmann single mirror or three mirror gonioscope.
MacKay-Marg Pulse air tonometer—It is a hand held. It employs a microscopic transducer which applanates the cornea and converts IOP into electrical waves. This tonometer is very good for mass screening as there is no danger of cross-infection and local anaesthetic is not required. They provide a mirror image of the opposite angle. Slit-lamp examination—It is essential when minute examination of the eye is necessary. Barkan goniolens. A brilliant light is brought to a focus as a slit or point by an optical system supported on a movable arm and observations are made by a binocular microscope.
They are used both for diagnostic and operative purposes. Trans-scleral—When an intense beam of light is thrown through the sclera. If there is a solid mass in the path of light. The lines from above downwards should be read at At these distances the letters subtend a visual angle of 5' at the nodal point. It is kept at a distance of 6 m so that the rays of light are parallel for practical purpose. Trans-pupillary—When an intense beam of light is allowed to pass obliquely through the dilated pupil.
Ciliary band—A grey or dull brown band of ciliary body is seen at the insertion of iris root. Subjective Examination of Retinal Functions 1. The minimum illumination of the test type accepted for satisfactory vision should be foot candles. Examination of the Eye 35 Gonioscopic examination of the angle of anterior chamber Normal angle structures from anterior to posterior —Normal angle structures are: It tests the form sense.
Scleral spur—It is a prominent white line which represents the most anterior projection of the sclera. The presence of a narrow angle of the anterior chamber. Trabecular meshwork—The degree of pigmentation varies. Simple picture chart—It is used for children. E chart—It is used for illiterate persons. If he fails to see the light. Other Test Types 1. A normal person can read all the lines.
In a dark room. When the patient can only read the 18 m line. If he can appreciate the movements. If the patient is unable to see the top letter when close to it. If he can count fingers only at 50 cm. If he cannot count fingers. When the patient cannot read the largest letter. He is asked to say when the light is on the eye or when it is off. If he tells correctly.
If he can count the fingers. If he can read the top most letter at 5.
Recording of Visual Acuity for Distance Each eye is tested separately. Point of fixation—It is the area of maximum visual acuity in the normal visual field. The crier of Water Cresses frequently travels seven or eight miles rose sauce cannon reverse N. Water Cresses are sold in small bunches. The effect pro- cave scorn veneer succour N. Doors-mats of all kinds. The streets of London are better paved and better lighted than those of any metropolis in Europe: Boundary—The peripheral limits of the visual field.
Examination of the Eye 37 N. Hearth Brooms. It corresponds to the foveola of the retina. This is the principle used in computerized automated perimeters. Negative scotoma—It is a defect detected only when visual field is recorded. It is commonly seen in cases of glaucoma. Kinetic perimetry—A target is moved across the field to map out of the two-dimensional extent of field. Positive scotoma—When the patient appreciates a dark area in his field of vision. Static perimetry—It forms the basis of modern glaucoma assessment.
It corresponds to the region of optic nerve head where there are no rods and cones. The point of perception is recorded along different meridians. Relative scotoma—A variable amount of vision remains.
The stimuli can be presented in two different ways Extent of normal visual field of right eye a. Suprathreshold perimetry—It is used mainly for screening the patients. Scotoma—It is an absolute or relative area of depressed visual function non-seeing area surrounded by normal vision.
Visual stimuli are presented at luminance levels above the expected normal threshold values in various locations in the visual field. Two techniques of testing the field of vision are commonly employed: It involves presentation of a moving stimulus of known luminance or intensity from periphery towards the centre till it is perceived.
In cases of moderate to gross loss of sensitivity. By joining these points an isopter is plotted for that stimulus intensity. Absolute scotoma—All vision is lost. Confrontation Method It is a rough but very useful method. Method—The surgeon stands facing the patient at a distance of about 60 cm. Method—The patient is seated with his chin supported by the chin rest. Peripheral Field i.
Principle—The patients field of vision is compared with that of the examiner having a normal field of vision. Friedmann analyser. Each of them has an electronic fixation control and an automatic recording of missed points. There is constant monitoring of fixation. Method—The patient sits 2 m away from the screen. Automated perimeters. Objective Examination of Retinal Functions The retinal function can be tested objectively by: It is extinguished or absent in complete failure of function of rods and cones.
In static perimetry. Auto field perimeters Field master and Humphery field analyser static technique. Electroretinogram ERG The changes induced by the stimulation of light in the resting potential of the eye are measured by electroretinography.
These are more sensitive than manual perimetry. Automated perimeters utilize computers to programme visual field sequences. Visual field can be always stored and reproduced. Advantages 1. Baylor visual field programmer attached to standard Goldmann perimeter. Examiner bias is eliminated.
Plane mirror examination at a distance of 1 m—Uniform red glow is seen if there are no opacities in the media. Media Media consists of cornea. The image is virtual. The incident rays reach the retina causing it to be illuminated.
Optical principle i. Plane mirror examination at a distance of 22 cm distant direct ophthalmoscopy —The exact position of the opacities or black spots in the refractive media is determined by parallactic displacement.
Media can be clear. Method—The surgeon looks through a self-luminous ophthalmoscope and directs the light upon the pupil.
Fundus oculi examination 1. Examination of the Eye 41 2. Electro-oculogram EOG The changes in the resting current when the eyes are moved laterally are picked up by the electrodes placed at the inner and outer canthi. Examination of the fundus is done best at a close distance with accommodation relaxed.
The emergent rays from the fundus then reach the observers retina through the hole in the mirror. A uniform red reflex or glow is seen.
Direct ophthalmoscopy—Helmholtz invented the direct ophthalmoscope. Atropine is preferred in children as it results in paralysis of ciliary muscle. It is absent in retinal dystrophies and degenerations. The convergent light beam is reflected from the ophthalmoscopic mirror ii.
The curved surface of the lens is towards the examiner. The convergent beam is cast by a perforated concave mirror. The lens is held in between the thumb and forefinger of the left hand. It is pink in colour. Papilloedema is seen in cases of raised intracranial tension brain tumour and malignant hypertension. The central retinal vessels emerge from the middle.
It is blurred in cases of secondary optic atrophy. It is pale or white in cases of optic atrophy. Indirect ophthalmoscopy Advantages of indirect ophthalmoscope 1. The normal cup: It can be used in high refractive error.
The beam passes through the opacities in the media. It is waxy yellow in retinitis pigmentosa v. Strong illumination.
Optic Disc It is circular or oval in shape measuring 1. Shape—The normal optic disc is round or oval in shape. The periphery of the retina can be seen by scleral depression with the patient in lying down position. It is situated at the posterior pole of the fundus. Margin—The margin is sharp and clearly defined normally and in primary optic atrophy. Size—Optic disc is large in myopia and small in hypermetropia and aphakia.
Colour—It is normally pink in colour. Cupping—Pathological cupping is seen in glaucoma. Total retinal area and pars plana can be examined with the help of scleral indentation. A real. Black pigments resembling bone corpuscles are typically seen in retinitis pigmentosa. There is a bright foveal reflex in the centre due to reflection of light from the walls of the foveal pit.
General Fundus Normally the fundus has a uniform red appearance. Cystoid macular oedema. In albino. Three types of lenses are available for biomicroscopic examination of the vitreous and fundus. In high myopia. The arteries are brighter red and narrower than veins. Examination of the Eye 43 3. By interposing a —55 D approximately lens in front of the cornea. Goldmann three mirror contact lens—Three mirrors are placed in a cone. It is a small circular area. Macula Lutea It is situated 3 mm or 2 disc diameter to the temporal side of the optic disc.
The normal artery: Retinal Vessels These are derived from the central retinal artery and vein. Corneal staining is done by following vital stains a. Ciliary congestion is most marked at the a. White pupillary reflex is seen in a. The normal depth of anterior chamber is a. Pupil is pinpoint in a. Anterior chamber is shallow in a. Keratometry is used in the measurement of a.
Corneal sensations are reduced in a. Corneal thickness is measured by a. Superficial vascularisation of cornea has all the following features. Tremulousness of iris is seen in a. Central field of vision is limited up to a. Examination of the Eye 45 The normal intraocular pressure is Schiotz a. The most accurate method of measuring lOP is a.
In indirect ophthalmoscopy the image is a. Distant vision is recorded at a distance of a. Near vision is recorded at a distance of a. Schiotz d. Peripheral field of vision is tested by a. Normal field of vision extends on the nasal side to a.
Distant direct ophthalmoscopy is done at a distance of a. In direct ophthalmoscopy the image is a. Periphery of retina is best visualized with a.
In a frightened man. Campimetry is used to measure a. Angle of anterior chamber is studied with a. Most emmetropic eyes are approximately 24 mm in length. The retinal image is inverted but it is re-inverted psychologically in the brain. The normal schematic eye Optic axis—The line passing through the centre of curvature of cornea and the two surfaces of the lens.
An emmetropic eye will have a clear image of a distant object without any internal adjustment of its optics.
There is no error of refraction. Nodal point—The optical centre lies in the posterior part of the lens. The eye is considered to be emmetropic when incident parallel rays of light from infinity come to a focus on the retina fovea centralis with accommodation at rest. The normal eye is like a camera. Anterior focal distance—It is about 15 mm in front of the cornea. The normal eye is so constructed that distant objects form their images upon the retina. Posterior focal distance—It is about 24 mm behind the cornea.
When light rays pass from a medium of one density to a medium of a different density they are refracted or bent. Before reaching the retina light rays pass successively through the cornea. Index ametropia—There is abnormal refractive index of the media.
Too long—In myopia Too short—In hypermetropia. Curvature ametropia—There is abnormal curvature of the refracting surfaces of the cornea or lens. Axial ametropia—There is abnormal length of the eyeball. Too high—In myopia Too low—In hypermetropia. Axial—Increased anteroposterior diameter of the globe is the most common cause. Abnormal position of the lens Forward displacement—In myopia Backward displacement—In hypermetropia.
Curvature—Increased curvature is seen in following conditions: Too strong—In myopia Too weak—In hypermetropia. Usually the young children are unable to see the blackboard clearly. Indistinct distant vision is the most common symptom. There is discomfort after near work.
Fundus examination. Fundus changes in pathological myopia. Flashes of light may be seen. Apparant divergent squint may be present. Jews and Japanese. Prominent eyes. Forward displacement of the lens. Signs 1. This leads to exposure of choroidal pigment. Corneal—Conical cornea. Symptoms 1. Index—Increased refractive index of the nucleus. Errors of Refraction 49 i. Black spots are seen floating before the eyes.
Spectacles—Myopia is treated by prescribing suitable correcting spherical concave lenses for constant use. Complicated cataract posterior cortical is due to the disturbance to the nutrition of the lens.
In low degree of myopia. Treatment 1. Two high myopes should not get married as far as possible. In pathological myopia. It is good in simple myopia. Retinal detachment simple is always due to break in the retina through which fluid seeps in. Prognosis 1. Vitreous degeneration liquefaction. Complications 1. Tear and haemorrhages occur in the retina due to chorioretinal degeneration. High myopia is sometimes associated with chronic simple glaucoma. Operative i. Epikeratophakia—It is a procedure in which a lenticule of donor tissue of desired power is used to alter the surface topography of cornea.
Toric lense may be used. Incidence Newborns are invariably hypermetropic average 2. Errors of Refraction 51 Temporal and supertractional nasal crescent presbyopic age. It should be undercorrected to avoid very bright and clear retinal images which are uncomfortable. Hygiene of eyes—Proper position.
Radial keratotomy—Multiple peripheral cuts are made in the cornea in order to flatten the increased curvature of the cornea. Excimer laser—It reshapes and flattens the central part of the cornea photorefractive keratectomy iii. This alters the shape of the cornea by flattening it. Keratomileusis—A disc of cornea is freezed and placed on a lathe machine and keratomileusis grinding is performed.
Axial—There is short length of the eyeball. Index—There is increase in refractive index of the cortex. There may be frontal headache and eye strain. Latent hypermetropia—It is overcome by the normal tone of the ciliary muscle. Symptoms These are noticed specially in the evenings after close work. It is prone to cause closed angle glaucoma. In adults. Accommodative convergent squint may be present.
Manifest hypermetropia—It is detected without paralysing the ciliary muscle. Absence of lens or aphakia—It is a classical example of acquired high hypermetropia. It is detected only when the ciliary muscle is paralysed by atropine.
Treatment—It is treated by prescribing suitable correcting spherical convex lenses. Burning and dryness in the eyes are usually present. Facultative—It can be overcome by an effort of accommodation. Types—Total hypermetropia may be divided into: Curvature—There is flat curvature of the cornea. There is blurring of vision for near work. Absolute—It cannot be overcome by an effort of accommodation.
Backward displacement of the lens as in posterior dislocation of the lens. There is typical small eye as a whole. Mixed 2. It is curved above downwards vertical meridian. Compound iii. Regular i. Regular astigmatism is present when the two principal meridians are at right angles. There is decentring of the lens. Against the rule—The horizontal meridian is more curved. It can be corrected by lenses.
According to the rule—The vertical meridian is more curved. There is unequal curvature of the cornea in different meridians. Simple ii. Regular Astigmatism Normally cornea is flatter from side to side horizontal meridian perhaps because of the pressure of the eyelids.
Diminished visual acuity is the most troublesome clinical symptom. Retinal plane at B Simple hypermetropic astigmatism Vertical meridian—Emmetropic Horizontal meridian—Hypermetropic Retinal plane at C and D Mixed astigmatism [circle of least diffusion] Vertical meridian—Myopic Horizontal meridian—Hypermetropic Retinal plane at E Simple myopic astigmatism Vertical meridian—Myopic Horizontal meridian—Emmetropic Retinal plane at F Compound myopic astigmatism Both the foci are in front of the retina 2.
Soft contact lens may be used. When there are symptoms. Partial or full thickness keratoplasty may be done depending on the depth of opacity as a last resort. Irregular Astigmatism It is present when the corneal surface is irregular. It cannot be adequately corrected by lenses.
Retinal plane at A Compound hypermetropic astigmatism Both the foci are behind the retina. Eye strain and headache after short-time of near work is usually present.
If there are no symptom. It is cheap and readily available. The eye is hypermetropic. Errors of Refraction 55 Prognosis 1. The anterior chamber is deep due to lack of support of the iris by the lens. There is often iridodonesis or tremulousness of the iris due to lack of support. In pseudophakia. The pupil is jet black. Regular astigmatism is the only form susceptible to treatment by lenses. A linear semicircular corneo-scleral scar mark is seen in the upper half of cornea.
Aphakic eye Correction with convex lens Symptom There is gross dimness of vision because of acquired high hypermetropia. It is easy to handle particularly by old persons. Optical Condition 1. Purkinje-Sanson 3rd and 4th images are absent. Parallel rays of light reach a focus about 31 mm behind the cornea.
It is a classical example of acquired high hypermetropia. There is loss of accommodation.
Astigmatism [against the rule]—The surgical scar at the corneoscleral junction in the upper part of the cornea flattens the vertical meridian of the cornea. It looks good cosmetically. There is greater refraction at the periphery of spherical lens than near the centre.
Contact Lens Advantages There is minimum retinal image magnification. Corneal erosion and ulcer may result from epithelial damage. Disadvantages 1. There is difficulty in co-ordination and orientation. Corneal vascularization may occur due to constant irritation. Physical inconvenience and cosmetic deficiency is often present. Corneal epithelium oedema may occur due to hypoxia. Papillary conjunctivitis may occur due to the growth of pathogens.
The peripheral visual fields are reduced. Chromatic aberration may be present. Intolerance and foreign body sensation are common complaints. Both eyes are ametropic but differ in variety. Dislocation of IOL may occur in the vitreous or anterior chamber.
Cystoid maculopathy leads to impaired vision. Standard calculation tables. Errors of Refraction 57 3. There is minimum retinal image magnification 2. Both eyes are ametropic either myopic or hypermetropic but differ in degree. There is eye strain due to aniseikonia. Corneal dystrophy may occur due to endothelial damage with anterior chamber lens. Pupillary block glaucoma results in raised tension postoperatively. There is early return of binocular vision 3.
It has cosmetic advantage. Congenital i. One eye is emmetropic and the other eye is ametropic. Lenses are biconvex or planoconvex measuring mm in diameter. Posterior chamber IOL implantation is best as they are placed in the normal physiological position of lens.
The peripheral vision is normal 4. Diplopia or seeing double objects may be present in severe cases and unilateral aphakia.
Acquired It is seen after unilateral cataract extraction. One eye is emmetropic and the operated eye is hypermetropic.
Lens power is calculated by: Postoperative iridocyclitis may occur occasionally. Keratometry iii. Ultrasonography A-scan axial length ii. Presbyopia is treated by prescribing suitable convex spherical lenses for near work. In low degree. This correction for near work is added to the correcting lenses for the distant vision.
The other eye may become divergent and take the position of rest. Symptoms depend on existing error of refraction. There is blurring of vision for near work specially reading.
The average eye glass adds for In myopia—There is delayed onset of presbyopia. Etiology There is physiological failure of accommodation due to: It is treated by prescribing suitable correcting lenses for refractive difference of up to D. Symptoms appear early in persons doing too much close work.
The vision improves if the book is held further away from the ordinary reading distance. Alternating vision—The hypermetropic eye is used for distance and the myopic eye is used for near. It is not an error of refraction. In high degree more than D. Presbyopia Symptoms 1. In hypermetropia—There is early onset of presbyopia. Iseikonic or size lenses are indicated in complicated cases of anisometropia.
Contact lenses are useful in correcting aniseikonia. In children—Atropine ointment application three times a day for 3 days is preferred up to 8 years of age as it paralyses the ciliary muscle.
Determination of refraction is done by the following methods: Keratometer—It is useful for testing corneal astigmatism particularly. Children have great power of accommodation. In adults—Phenylephrine. Retinoscopy—It is done after dilatation of the pupil. Auto-refractometer—Refraction is tested automatically using electronic and computer technology. Mydriatics in Refraction The pupil is dilated by a suitable mydriatic depending on the age of patient. Objective Methods i.
It is added to the correction for distant vision. In myopia of —1 D: There is no shadow. In hypermetropia: The shadow moves in the same direction as the mirror. In myopia above —1 D: The shadow moves in the opposite direction. In emmetropia and myopia of less than —1 D: There is a very faint shadow moving in the same direction. It is always undercorrected. Streak retinoscopy Neutralisation When the shadow moves with the mirror.
Observations and Inferences 1. Then the two eyes are finally tested and corrected together for distant vision. No shadow is seen ii.
In astigmatism: The shadow appears to swirl around scissor-shaped. Each eye is tested separately. The correction for near vision by convex spherical lenses is made over 40 years of age usually.
The direction in which the shadow moves is noted. When the lens is moved in front of the eye. Spherical Lens It has equal curvature in all meridians. Identification i. An object seen through the lens appears to be diminished in size. If an object is held close to the lens. Uses It is used in the treatment of: Spherical lens—Convex. Cylindrical lens—Convex.
Concave lens—It is transparent medium bounded by concave surfaces. Convex lens—It is a transparent medium bounded by two spherical surfaces. When the lens is moved in a direction at right angles to the axis Convex cylinder—The objects move in the opposite direction. This angle is called. When the lens is moved in the direction of the axis. Concave cylinder—The objects move in the same direction. Two marks are seen on the lens indicating the axis of the lens.
Disadvantage—The corneal hypoxia leads to corneal oedema. Cylindrical Lens It is a segment of a cylinder of glass cut parallel to its axis.