Indirect Ophthalmoscopy .pptx
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Indirect ophthalmoscopy allows examination of the retina using an inverted magnified image. A strong convex lens is placed near the eye to make the eye highly myopic. This brings light from the retina to a focused real image between the lens and observer. The image size and position depends on the eye's refractive error - it is at the lens focus for emmetropia, in front for myopia, and behind for hyperopia. Indirect ophthalmoscopy provides a large field of view useful for retinal pathology assessment and laser treatment. Though difficult to learn, it allows examination of peripheral retina and is useful in media opacity.
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1. o Cornea requires energy for normal metabolic activities as well as for maintaining transparency and dehydration o Energy is generated by the breakdown of glucose in the form of ATP o Most actively metabolizing layer are epithelium and endothelium o Sources of nutrients : o Oxygen : mainly from atmosphere through tear film , with minor amount supplied by the aqueous and limbal vasculature o Glucose , amino acid, vitamins and other nutrients supplied to cornea by aqueous humor o Glucose also derived from glycogen stores in corneal epithelium o Epithelium consumes O2 10 times faster then stroma
2. o Three process or pathways – o Pentose shunt (Hexose monophosphate shunt) –occurs both in hypoxic and normoxic condition o Glycolysis (Embden meyerhof pathway) –anaerobic process , glucose / glycogen converted to pyruvate yeilding 2 ATPs o TCA or krebs or citric acid cycle- aerobic condition pyruvate is oxidized to yield 36 ATP, water, CO2.
3. o In normal conditions all the glucose consumed by the cornea o Glucose mostly come from aqueous humor o The rate of glucose consumption by the whole cornea is approx. 100 microgram/hr/cm2. o 1 mol. of glucose will be converted to the pyruvic acid and produced 2 molecules lactic acid and 2 mol. of ATP o In the krebs cycle, 1 mol. of glucose will utilize the pyruvic acid and O2 to produced 36 mol. ATP o Epithelium and endothelium will consume the oxygen
4. o The pentose phosphate pathway is used to metabolize five carbon sugars; one ATP and 2 NADH molecules are produced from oxidation of one glucose molecule o Produced intermediates for nucleic acid synthesis and some amino acids o This process will happen in hypoxic or normoxic condition o The purpose of glucose metabolism through the pentose shunt is the production of NADPH
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- Pentacam is useful for diagnosing conditions like keratoconus by detecting thinning, steepening, and irregularity. It can also evaluate outcomes of procedures like refractive surgery and intraocular surgery.
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2. The slit lamp examination uses different illumination techniques like diffuse, direct, and retroillumination to examine the anterior segment of the eye including the eyelids, cornea, iris, and lens.
3. Indirect techniques like specular reflection and optical sectioning are used to examine corneal structures at high magnification.
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This document provides information about the Maddox rod and Maddox wing, which are used to measure eye alignment and phoria. The Maddox rod consists of cylindrical lenses available in red and white, and is used at distances of 3m and 6m to measure horizontal and vertical distance phoria by having one eye view a line while the other views a spot. The Maddox wing is used at 33cm to measure near phoria by having the eyes view dissimilar images of arrows pointing to a scale. The procedures for each are described. References for more information are also provided.
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Indirect ophthalmoscopy allows examination of the peripheral fundus and posterior pole. It should be used when examining patients with symptoms suggesting retinal abnormalities or those with certain systemic diseases. Indirect ophthalmoscopy involves placing a high-power convex lens in front of the eye to form a real, inverted image of the fundus that can be viewed. It can be performed monocularly or binocularly to allow stereoscopic viewing. Proper technique involves dilating the pupil and using illumination while positioning the condensing lens to view different areas of the fundus.
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Bio optos-8-21-2011
Indirect ophthalmoscopy provides binocular visualization of the retina using an illuminated, inverted image located between the examiner and patient. There are two main types:
1. Binocular indirect ophthalmoscopy (BIO) allows for the best view of the retina through large fields of view and minimal refractive error effects. A condensing lens focuses light into the pupil and forms an aerial image magnified by the lens power.
2. Direct ophthalmoscopy provides a monocular view with high magnification but limited field of view and issues with reflections. It is better for viewing small pupils or the retinal nerve fiber layer.
Key factors that affect the view include the condensing lens power, examiner distance,
Errors 1
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Retinoscopy @adi
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Indirect Ophthalmoscopy .pptx
- 1. Indirect Ophthalmoscopy • Invented by Nagel in 1864 • An inverted reverse real image • Magnification:2 to 4 times • Field of vision: 40 to 50 degrees • Optical working distance 40 to 50cm • Good illumination and stereopsis • Ease of use with scleral inventor • Lenses for 14 to 30 D range
- 2. Types • Head Mounted • Spectacle Mounted
- 3. Condensing lenses Three types • Biconvex • Plano convex • Aspheric • Two different curved surfaces - to avoid spherical aberration • Steeper curvature faces the examiner • + 20 ,+30 , +14 D
- 5. Parts of indirect ophthalmoscopy
- 6. Principle The Principle of indirect ophthalmoscopy is to make the eye highly myopic by placing a strong convex lens in front of the patient's eye so that emergent rays from an area of fundus are brought to focus as a real, inverted image between the lens and the observer's eye.
- 8. Field of Illumination • More in myopia and less in hypermetropia as compared to emmetropia
- 9. Image Formation • EMMETROPIA • MYOPIA • HYPERMETROPIA
- 10. Emmetropia • Emmetropic eye, rays from fundus are parallel, brought to a focus by the condensing lens Image formed at the principal focus of the lens Hence, size of image remains the same, no matter the position of lens.
- 11. Myopia • Rays are convergent • Image formed in front of the eye • Final image by condensing lens within its own focal length • Image is smaller when lens is nearer to anterior focus of the eye and larger when away
- 12. Hypermetropia • Rays divergent and appear to come from behind the retina • Image by condensing lens in front of its principle focus • Image is larger when lens is nearer to the anterior focus of the eye and smaller when away.
- 13. Relative Position of Image • In Emmetropia: - at the principal focus • In Myopia: - Nearer to the lens than its principal focus • In Hypermetropia: - Farther away from the principal focus
- 14. Factors affecting field of view • Patient's pupil size • Power of the condensing lens • Over all size of the condensing lens • Refractive error • Distance the condensing lens is held from the patient's eye
- 15. Image Characteristics • Real, inverted and magnified • Magnification depends on: Dioptric power of the convex lens Position of lens in relation to the eyeball Refractive state of the eyeball
- 16. Prerequisites • Dark room • Source of light and a concave mirror or self illuminated indirect ophthalmoscope • Convex lens (commonly used +20D) • Pupils of the patient's eye should be dilated
- 17. Procedures • Patient is made to lie in the supine position, with one pillow on a bed or couch and instructed to keep both eyes are open. • The examiner throws the light into the patient's eye from an arm distance. • Binocular ophthalmoscope with head band or that mounted on the spectacle frame is employed most frequently. • Keeping his or her eyes on the reflex, the examiner then interposes the condensing lens.
- 18. • In the path of beam of light ,close to patient's eye,then slowly moves the lens away from the eye until the image of the retina is cleared seen. • The examiner moves around the head of the patient to examine direct quadrants of the fundus.
- 19. •He or she has to stand opposite the clock hour position to be examined ..eg.to examine inferior quadrant(around 6 o'clock meridian)the examiner stands towards the patient's head (12 o'clock meridian)and so on. •By asking the patient to look in extreme gaze, using scleral indenter,the whole peripheral retina upto ora serrata can be examined.
- 22. Applications Indirect ophthalmoscopy is essential for the assessment and management of the retinal detachment and other peripheral retinal lesions.
- 23. Advantages • Larger field of view • Lesser distortion of retinal image • Useful in hazy media • Useful eyes with nystagmus • Delivery of LASER • Better resolution. • Binocular examination of fundus up periphery • Useful in high spherical or astigmatism refractive errors.
- 24. Disadvantage • Difficult to learn • Less magnification there for details of a small lesion not visualized properly • Impossible with very small pupil • More uncomfortable to the patient
- 25. Thank you