ophthalmoscope /oph·thal·mo·scope/ (of-thal´mo-skōp) an instrument containing a perforated mirror and lenses used to examine the interior of the eye.
Ophthalmoscope
ophthalmoscope
ophthalmoscope, (ofthal´m
skōp´),
direct ophthalmoscope one that produces an upright, or unreversed, image of approximately 15 times magnification.
indirect ophthalmoscope one that produces an inverted, or reversed, direct image of two to five times magnification.
scanning laser ophthalmoscope an instrument for retinal imaging in which the retina is scanned by a low-power laser and the reflected light is used to create a digital image.
oph·thal·mo·scope ( f-th l m -sk p , p-)n. An instrument for examining the interior structures of the eye, especially the retina, consisting essentially of a mirror that reflects light into the eye and a central hole through which the eye is examined. |
Ophthalmoscope
An instrument used for viewing the inside of the eye that consists of a concave mirror with a hole in the middle through which the physician examines the eye, and a light source that is reflected into the eye by the mirror.
Mentioned in: Eye Examination, Glaucoma, Papilledema, Physical Examination, Retinal Artery Occlusion, Retinitis Pigmentosa, X Rays of the Orbit
ophthalmoscope
[ofthal′məskōp]
Etymology: Gk, ophthalmos + skopein, to look
a device for examining the interior of the eye. It includes a light, a mirror with a single aperture through which the examiner views, and a dial holding several lenses of varying strengths. The lenses are selected to allow clear visualization of the structures of the eye at any depth. If the patient or the examiner ordinarily requires extensive correction of a refractive error, the examination may require that the corrective lenses should be worn for the examination. Also called funduscope.
ophthalmoscope, (ofthal´m
skōp´),n a device for examining the interior of the eye. It includes a light, a mirror with a single hole through which the examiner may look, and a dial holding several lenses of varying strengths. The lenses are selected to allow clear visualization of the structures of the eye at any depth.
ophthalmoscope
an instrument for examining the interior of the eye. It sends a bright, narrow beam of light through the lens of the eye, and contains a perforated mirror and lenses through which the veterinarian can examine interior parts of the eye. It is helpful in detecting possible disorders of the eyes, as well as disorders of other organs that are reflected in the condition of the eyes.
direct ophthalmoscope
one that produces an upright, or unreversed, image of approximately 15 times magnification.
indirect ophthalmoscope
one that produces an inverted, or reversed, direct image of two to five times magnification.
ophthalmoscope
An instrument for viewing the media and fundus of the eye. It consists essentially of: (1) a light source (a halogen or tungsten bulb), a condenser system, a lens and a reflector (a prism, mirror, or metallic plate) to illuminate the interior of the eye, and (2) a viewing system comprising a sight hole and focusing system (usually a rack of lenses of different powers) to compensate for the combined errors of refraction of the patient and practitioner. See transillumination; Visuscope.
binocular indirect ophthalmoscope (BIO) An indirect ophthalmoscope with a binocular viewing system for obtaining a magnified, inverted, stereoscopic image of the fundus. It consists of a light source mounted above and between the examiner's eyes on a headset. This illuminates a handheld condensing lens of high positive power close to the patient's eyes, which forms an image of the patient's pupil in both of the examiner's pupils. An aerial image of the patient's fundus is formed between the condensing lens and the examiner (if the patient is emmetropic the image will be formed in the focal plane of the condensing lens). It appears inverted and stereoscopically through the oculars attached to the headset. Stereopsis is obtained by reducing the interpupillary distance by means of mirrors or prisms within the headset of the instrument. This ophthalmoscope allows examination of a wide area of fundus and perception of depressed and raised areas (Fig. O1).
confocal scanning laser ophthalmoscope (CSLO) An instrument using a confocal laser system to provide and analyse a three-dimensional image of the optic nerve head, peripapillary retina and macular region. The instrument uses a 670 nm diode laser and measures the amount of light reflected from a series of 16-64 optical sections in depth and reconstructs them to show the topography of the optic nerve head and a measure of the thickness of the retinal nerve fibre layer (RNFL). The RNFL thickness is compared with an age-matched normative database. The instrument is used to analyse RNFL defects, to detect damage to the optic nerve head and progressive changes over time in glaucomatous eyes, as well as retinal oedema, which occurs in the early stages of diabetic retinopathy. Syn. confocal scanning laser tomograph. See glaucoma detection; confocal microscope.
direct ophthalmoscope An ophthalmoscope that provides a virtual, erect image with a magnification of about ✕15 of the fundus, formed by the patient's eye in combination with whatever focusing lenses are needed to correct for the refractive errors of the observer and patient. The instrument is held at close range to the patient's eye and the field of view is small (less than 10º) (Fig. O2). The magnification M of a direct ophthalmoscope is equal to
indirect ophthalmoscope An ophthalmoscope that provides an aerial image of the fundus (and not the fundus itself as with a direct ophthalmoscope), which is real, inverted, with a magnification of ✕5 to ✕7 and formed at approximately arm's length from the practitioner. This aerial image is usually produced by a strong positive lens ranging in power from +13 D to +30 D that is held in front of the patient's eye. The practitioner views this aerial image through a sight hole with a focusing lens to compensate for ametropia and accommodation. This instrument provides a large field of view (25-40º) and allows easier examination of the periphery of the retina. This instrument has been supplanted by the binocular indirect ophthalmoscope. The magnification of an indirect ophthalmoscope M is equal to
scanning laser ophthalmoscope (SLO) An ophthalmoscope that provides a continuous image of the ocular fundus on a TV monitor. It consists of a narrow laser beam, which is scanned horizontally and vertically to produce a rectangular area (called a raster) on the retina. A small beam of light is reflected back out of the eye to a light detector, which monitors the brightness of each point on the raster and relays the information to the corresponding element on a TV monitor where the image can be viewed and/or stored. Low illumination is used to make this procedure more comfortable than conventional photography and mydriatics are usually unnecessary. The field of view extends up to 40 degrees. The instrument has been especially valuable in diagnosing glaucoma and in research.
binocular indirect ophthalmoscope (BIO) An indirect ophthalmoscope with a binocular viewing system for obtaining a magnified, inverted, stereoscopic image of the fundus. It consists of a light source mounted above and between the examiner's eyes on a headset. This illuminates a handheld condensing lens of high positive power close to the patient's eyes, which forms an image of the patient's pupil in both of the examiner's pupils. An aerial image of the patient's fundus is formed between the condensing lens and the examiner (if the patient is emmetropic the image will be formed in the focal plane of the condensing lens). It appears inverted and stereoscopically through the oculars attached to the headset. Stereopsis is obtained by reducing the interpupillary distance by means of mirrors or prisms within the headset of the instrument. This ophthalmoscope allows examination of a wide area of fundus and perception of depressed and raised areas (Fig. O1).
confocal scanning laser ophthalmoscope (CSLO) An instrument using a confocal laser system to provide and analyse a three-dimensional image of the optic nerve head, peripapillary retina and macular region. The instrument uses a 670 nm diode laser and measures the amount of light reflected from a series of 16-64 optical sections in depth and reconstructs them to show the topography of the optic nerve head and a measure of the thickness of the retinal nerve fibre layer (RNFL). The RNFL thickness is compared with an age-matched normative database. The instrument is used to analyse RNFL defects, to detect damage to the optic nerve head and progressive changes over time in glaucomatous eyes, as well as retinal oedema, which occurs in the early stages of diabetic retinopathy. Syn. confocal scanning laser tomograph. See glaucoma detection; confocal microscope.
direct ophthalmoscope An ophthalmoscope that provides a virtual, erect image with a magnification of about ✕15 of the fundus, formed by the patient's eye in combination with whatever focusing lenses are needed to correct for the refractive errors of the observer and patient. The instrument is held at close range to the patient's eye and the field of view is small (less than 10º) (Fig. O2). The magnification M of a direct ophthalmoscope is equal to
M = Fe/4
where Fe is the power of the eye. Example: the magnification of the fundus of an aphakic eye of +40.00 D is equal to 40/4 = 10✕.indirect ophthalmoscope An ophthalmoscope that provides an aerial image of the fundus (and not the fundus itself as with a direct ophthalmoscope), which is real, inverted, with a magnification of ✕5 to ✕7 and formed at approximately arm's length from the practitioner. This aerial image is usually produced by a strong positive lens ranging in power from +13 D to +30 D that is held in front of the patient's eye. The practitioner views this aerial image through a sight hole with a focusing lens to compensate for ametropia and accommodation. This instrument provides a large field of view (25-40º) and allows easier examination of the periphery of the retina. This instrument has been supplanted by the binocular indirect ophthalmoscope. The magnification of an indirect ophthalmoscope M is equal to
M = Fe / Fc
where Fe and Fc are the powers of the eye and of the condensing lens, respectively. Example: using a condensing lens of +15.00 D to view the fundus of an emmetropic eye yields a magnification of 60/15 = 4✕. See fundus camera; inverted image.scanning laser ophthalmoscope (SLO) An ophthalmoscope that provides a continuous image of the ocular fundus on a TV monitor. It consists of a narrow laser beam, which is scanned horizontally and vertically to produce a rectangular area (called a raster) on the retina. A small beam of light is reflected back out of the eye to a light detector, which monitors the brightness of each point on the raster and relays the information to the corresponding element on a TV monitor where the image can be viewed and/or stored. Low illumination is used to make this procedure more comfortable than conventional photography and mydriatics are usually unnecessary. The field of view extends up to 40 degrees. The instrument has been especially valuable in diagnosing glaucoma and in research.
)
Fig. O1 Binocular indirect ophthalmoscope. The light source mounted above and between the examiner's eyes illuminates the condenser, which images the source at the periphery of the patient's pupil. The illumination does not overlap the observation beam. The condenser lens is handheld; it forms an inverted aerial image of the retina
)
Fig. O2 Optical principle of the simplest form of direct ophthalmoscope (O, observer's eye; P, patient's eye; M, semi-silvered mirror)
| Table O1 Comparison between direct and indirect ophthalmoscopes | ||||||||
| ophthalmoscope | form | image | field of view (in degrees) | magnification | ||||
| direct | monocular | erect | 8 | ✕15 | ||||
| indirect | monocular | inverted | 20-40° | ✕5 to ✕7 | ||||
| indirect | binocular | inverted | 40-75 | ✕1.5 to ✕4.5* | ||||
| *Varies according to the power of the condensing lens. | ||||||||
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