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Paton, David, Barry N. Hyman and Johnny Justice, Jr. Lincoln, United Kingdom Seller Rating:. Seller Image. Introduction to ophthalmoscopy Paton, D. Create a Want Tell us what you're looking for and once a match is found, we'll inform you by e-mail. Spontaneous visibility of elevated lesions. When the pupil is small, the area of overlap shaded of illuminating and viewing beam is limited. When the pupil is large, the area of overlap extends farther backward, and elevated lesions may become visible without an ophthalmoscope.
For reflex-free ophthalmoscopy, we want to achieve the opposite: overlapping beams on the retina and separated beams through the cornea and lens where reflections and scatter may be bothersome. Satisfying Gullstrand's requirement may call for a compromise in the construction of the ophthalmoscope. Bringing the illuminating and viewing beams close together Fig. Reflex-free viewing is achieved more easily if the beams are separated see Fig.
A compromise can be reached by including a half-circle diaphragm in the illuminating beam. This diaphragm reduces the amount of reflection by intercepting the upper part of the illuminating beam see Fig. As a result, only the lower half of the field of view is illuminated, but the entire field may be scanned by moving this illuminated area around while viewing.
One ophthalmoscope on which this feature is available is the Propper instrument. Separation of viewing and illuminating beams for reflex-free direct ophthalmoscopy. Beams close: overlap in cornea and lens. Beams separated: Area of overlap moves backward, but a wider pupil is required.
Beams close, but illuminating beam restricted: less overlap, yet smaller pupil possible. This arrangement illustrates the advantage of equipping the illuminating system with its own optical system of a condensing lens to intensify the beam , diaphragm, and projecting lens to limit the total circumference of the beam. In modern hand-held ophthalmoscopes, this is always the case. In the older forms of ophthalmoscope with a mirror and external light source, this was not possible.
For maximum light effectiveness with small pupils and for the most even fundus illumination, the narrowest part of the illumination beam the area where an image of the filament is formed should be positioned within the patient's pupil, that is, 2 to 3 cm outside the ophthalmoscope head. Some ophthalmoscopes place it closer, for example, on the patient's cornea or even on the reflecting prism. The latter position is not optimal. In prefocused ophthalmoscopes the manufacturer has made the adjustments. In ophthalmoscopes that allow for some adjustment of the light bulb, the user can choose to adjust the illuminating beam either toward or away from the edge of the mirror or prism.
Location toward the edge allows small pupil viewing at the expense of more reflections. Location away from the edge reduces reflections but requires more dilation. Some ophthalmoscopes have an illumination system that can slide up and down, thus allowing individual adjustment for each patient. The ophthalmoscopy lens projects the observer's pupil and the illuminating source as reduced images into the patient's pupil Fig.
These reduced images and the narrow pencils of light that generate them allow for more complete separation through the cornea and lens than is possible in the direct method. Because Gullstrand's requirement is more easily fulfilled in indirect ophthalmoscopy, media opacities are often more easily penetrated by this method. Illumination and observation beam placement in indirect ophthalmoscopy. The observer's pupil and the light source are placed within the image of the patient's pupil.
Their image thus must fall within the actual patient pupil. Monocular method. Binocular method. This greater latitude in beam placement allows the use of two observation beams, thus allowing binocular viewing and stereopsis. To achieve this, the images of the observer's pupils must fit within the actual patient pupil, or the observer's interpupillary distance PD must fit within the enlarged image of the patient's pupil.
To make this possible the observer's PD is usually reduced through prisms or mirrors see Fig. The first binocular ophthalmoscope reportedly was made by Giraud-Teulon 18 in France To reduce the observer's PD, he placed a set of prisms behind the perforated hand-held mirror commonly used in those days. Gullstrand's explanation of the principle of reflex-free ophthalmoscopy led to the construction of large table-mounted ophthalmoscopes made by Zeiss in Europe and Bausch and Lomb in the United States , which were popular in clinical settings for many decades.
These also allowed binocular vision.
Yet binocular ophthalmoscopy did not gain wide acceptance until , when Schepens 14 introduced his binocular head-mounted ophthalmoscope with built-in light source. Today in the United States, binocular indirect ophthalmoscopy has largely replaced monocular indirect ophthalmoscopy. From this table it follows that the magnification of the pupil image resulting from a D lens and a cm viewing distance cm total distance is 12 times.
In general, it should be remembered that a pupil that is too small for viewing with a low-power ophthalmoscopy lens may be penetrable if a higher power is used. The original monocular, hand-held indirect ophthalmoscope used an external light source reflected by a mirror held in front of the observer's eye. Today the beam of a direct ophthalmoscope can be used, provided that the beam is strong enough and evenly concentrates all of its light output on the ophthalmoscopy lens.
Ophthalmoscopes with a more divergent beam, such as the AO giantscope, are less desirable. Alternatively, a special handle with built-in light source and prism can be used. The observer looks over the top or along the side of the prism see Fig. Oculus makes such a handle with rechargeable batteries. Beam placement in monocular indirect ophthalmoscopy. For the 3 o'clock and 9 o'clock periphery, the observer looks over the top of the beam. For the 6 o'clock and 12 o'clock periphery, looking along the side of the beam is advantageous.
Using the direct scope as an indirect light source makes it easy to alternate the two methods for the exploration of peripheral details. The fundus is first scanned in the indirect mode, and the desired detail is centered. Then, the ophthalmoscopy lens is removed and the patient's eye is approached. If orientation and alignment are properly maintained, the ophthalmologist can automatically zero in for precise examination of the desired detail. A major advantage of the monocular hand-held ophthalmoscope is that the positions of light source and viewing beam are variable.
The light source can be brought very close to the observer's line of view to allow viewing through very small pupils; more separation can be used with wider pupils to reduce reflections and to avoid scatter by cataracts. In a patient with a peripheral iris coloboma, it is sometimes possible to view through the undilated central pupil, while maneuvering the illuminating beam through the coloboma Fig.
Indirect ophthalmoscopy with a hand-held light. The hand-held light allows maximum flexibility of beam placement.
In direct ophthalmoscopy of the seated patient, the pupil becomes a vertically elongated oval when the patient looks to the left or to the right to allow us a view of the 3 o'clock and 9 o'clock periphery. With the ophthalmoscope held in its normal vertical position, the viewing and illuminating beams easily fit into this oval.
In viewing of the 6 o'clock and 12 o'clock positions, however, the pupil becomes horizontally elongated and it is advantageous to shift the ophthalmoscope to a horizontal position. This is done almost instinctively because it also allows closer approximation of the pupils. For other meridians, the ophthalmoscope has to be tilted accordingly Fig. Beam placement in direct ophthalmoscopy.
In peripheral viewing, the viewing and illuminating beams must fit within the narrowed appearance of the pupil. For the 12 o'clock and 6 o'clock positions, the ophthalmoscope is best tilted. Peripheral viewing is possible until the projection of the pupil becomes too narrow to accommodate the beams. Peripheral viewing, therefore, is better the wider the patient's pupil is dilated and is usually achievable up to the equatorial area.
In indirect ophthalmoscopy the same restrictions apply, but, because of the narrower beam in the patient's pupillary plane, it is easier to reach more peripheral areas. In monocular indirect ophthalmoscopy of the seated patient, the same conditions apply as for direct ophthalmoscopy. To view centrally and in the 3 o'clock and 9 o'clock positions, the observer should look over the top of the illuminating beam.
For the 6 o'clock and 12 o'clock positions, he or she will obtain better viewing if the illuminating beam and viewing beam are side by side Fig. If the observer uses the Oculus instrument, he or she will want to look along the side of the prism. If the observer uses the beam of a direct ophthalmoscope, he or she will want to change the ophthalmoscope to a horizontal position. Through a dilated pupil, a skilled ophthalmoscopist can readily visualize the ora serrata. In binocular indirect ophthalmoscopy with a head-mounted scope, the same flexibility of beam placement is not available.
Because the arrangement of the viewing and illuminating beams is generally horizontally elongated, viewing toward the 6 o'clock and 12 o'clock periphery of the eye of the seated patient will be relatively easier than toward the 3 o'clock and 9 o'clock periphery. Indirect binocular ophthalmoscopy of the peripheral retina is easier if the patient is reclining and looking upward and the observer can move around the patient's head. Under these conditions the patient's pupil always becomes a horizontally elongated oval and visualization up to the ora serrata is usually possible.
Some ophthalmoscopes offer minor adjustments of the relative position of the illuminating and viewing beams through tilting of the mirror.
The adjustability is advantageous for the expert, but it also increases the possibility of inadvertent maladjustment. The novice should use an ophthalmoscope that is permanently adjusted for a reasonable compromise setting. Adjustments in the Schepens Pomerantzeff ophthalmoscope. Standard setting. Additional separation in an extra-wide pupil. Less separation in a narrow pupil. Illuminating beam shifted for peripheral viewing.
To view the pars plana beyond the ora serrata, a technique first described by Trantas 12 is useful. It brings the far peripheral areas into view by depressing the sclera, either with one's finger or, more commonly, with a thimble-mounted scleral depressor as described by Schepens 14 Novice observers often find that attempting localization by indirect ophthalmoscopy is confusing.
They should remember that only the central ray through the ophthalmoscopy lens passes undeflected. A lesion seen in the center of the lens is seen in the same direction in which it would be seen on direct ophthalmoscopy.
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It is around this center that the image is inverted up is down, left is right Fig. These relationships can easily be verified by viewing the inverted image of a room seen through an ophthalmoscopy lens. Relative localization in indirect ophthalmoscopy. Only the detail seen through the center of the ophthalmoscopy lens ray 2 is seen in the proper direction. The rest of the image is inverted around this point.
In retinal surgery, precise localization is necessary for the treatment of retinal holes or for the removal of foreign bodies. This is not a simple matter, because the relationship between the ophthalmoscopic viewing angle in degrees from the optical axis and the external measurement in millimeters behind the limbus is not a linear one and varies according to the refractive error of the eye. Considerable ingenuity has been applied to this problem. Measuring devices have been built to record the exact viewing angle under which a lesion is seen.
Tables have been constructed to convert these data to external scleral measurements. Figure 22 summarizes the relationships for an emmetropic eye. Absolute localization through ophthalmoscopy. This figure summarizes the relationship of viewing angle and scleral localization. Vol 7. Heredity, Pathology, Diagnosis and Therapeutics. Because these measurements have to be verified at the time of surgery, surgeons have generally preferred direct localization during surgery. During surgery the indentation made by a scleral depressor on the outside of the globe can be localized ophthalmoscopically and compared with the location of the tear or foreign body.
The position of the depressor can then be adjusted until coincidence is reached. Fiberoptics have made it possible to use local transillumination for the same purpose. In dealing with metallic foreign bodies, the use of a metal detector during surgery is a further alternative or adjunct to ophthalmoscopic localization. In indirect ophthalmoscopy, nonphotographic fundus measurements can be made by engraving a scale on the surface of the ophthalmoscopy lens. In direct ophthalmoscopy, measurements of width can be made by projecting a scale or reticule in the illuminating beam.
For absolute measurements, corrections have to be applied for axial length and for ametropia; for the follow-up of a specific lesion, relative measurements are sufficient. Projection of a reticule in the illuminating beam is simple if the eye to be observed is emmetropic. If this is not the case, the reticule will be out of focus and measurement will be difficult. Focusing of the reticule can be achieved in the following ways:.
To estimate depth, one may observe movement parallax when the direct ophthalmoscope is moved across the pupil or may judge stereopsis when a binocular indirect ophthalmoscope is used. To measure depth in direct ophthalmoscopy, one may notice the difference in focusing required for details that lay in different planes, for example, the bottom of the disc, the normal retina, or an elevated lesion. For this measurement the observer must keep his or her accommodation constant, which is not easy for nonpresbyopic observers.
Accurate measurement is facilitated if the focusing of a reticule or of fine lines can be observed. This technique as is possible with the Oculus Visuskop and Propper Autofoc eliminates the accommodative factor. All of the methods discussed previously involve relative measurement. If measurements are to be related to standard units, the following approximations can be used: for lateral measurement, in which 1 disc diameter is approximately 1. For more exact conversions, elaborate corrections for ametropia have to be made. Ultrasound measurements offer an alternative that is independent of ophthalmoscopy.
A fixation star, a dot or a star-shaped figure, may be used to determine the patient's fixation. This is useful in determining eccentric fixation not only in strabismic amblyopia but also in central retinal dystrophies or macular degeneration. In the latter, it may be found that the patient fixates with a point considerably outside the area of visible change, indicating that the area of functional deficit is larger than that of the ophthalmoscopically visible changes. Knowing which area is used for fixation and how stable this fixation can be maintained is also useful in the evaluation of macular scarring, and even minimal fixation nystagmus can easily be recognized.
A slit diaphragm is often provided to allow slit-lamp type observation of elevated retinal lesions. The value of this gadget is limited, because the angle between slit beam and observation beam is fixed at zero, precisely the angle at which no depth measurement on the slit lamp is possible.
It may be used, however, as a hand-held slit lamp with observation from the side of the ophthalmoscope. A pinhole or half-circle diaphragm may be used to reduce reflections by limiting the illumination beam as indicated earlier see Fig. It is also helpful in the observation of certain fine retinal details that are seen best in the transitional zone between illuminated and nonilluminated retina. The spectral characteristics of various red-free filters vary, but all are low in transmission in the red part of the spectrum and high in the green and blue part.
Lack of red light makes the red elements very dark so that vessels and pinpoint hemorrhages stand out more clearly. The relative abundance of shorter wavelengths, which are scattered more easily in the largely transparent superficial retinal layers, makes it easier to observe changes in these layers, such as incipient retinal edema and changes and defects in the retinal nerve fiber layer. A blue filter may be provided to enhance the visibility of fluorescein, for use in fluorescein angioscopy and as a hand-held light source for fluorescein staining of the cornea.
A set of crossed polarizing filters in illuminating and viewing beam is sometimes used to reduce reflections if Gullstrand's requirement cannot be met. Light reflected off the cornea is not depolarized and can be filtered out by the viewing filter. Light diffusely reflected at the retina is depolarized and remains visible, but light that is specularly reflected, such as from the internal limiting membrane, is also filtered out. The use of these filters considerably reduces the effective light output of the ophthalmoscope.
Technologic advances in light source design have made it possible to deliver almost any amount of light to the fundus; this certainly does not improve patient comfort, and several studies have pointed at the side effects of prolonged intense ophthalmoscopy. Several attempts have been made to eliminate unnecessary radiation, particularly infrared. In the Exeter ophthalmoscope Mentor , dichroic mirrors are used, which selectively reflect infrared out of the top of the lamp housing and visible light for viewing out of the bottom opening.
Volk has introduced yellow-tinted ophthalmoscopy lenses, which are designed to absorb both infrared and blue light. The elimination of blue light also reduces scatter and enhances contrast. Because the slit-lamp microscope has a fixed focus on a plane approximately 10 cm in front of the objective and because the image of the fundus of an emmetropic eye appears at infinity, the fundus cannot be visualized without the help of additional lenses. There are several options. The practical application of this principle was worked out by Hruby 19 , 20 of Vienna with a lens known as the Hruby lens.
This beautifully illustrated and concise textbook of direct ophthalmoscopy is intended for medical students and is distributed to them without charge. However. Ophthalmoscopy, also called funduscopy, is a test that allows a health professional to see inside the fundus of the eye and other structures using an.
The optical principle is best understood if the lens is considered in conjunction with the eye, rather than as a part of the microscope. Parallel rays emerging from an emmetropic eye are made divergent by the Hruby lens and seem to arise from the posterior focal plane of that lens Fig. For a D lens, this would be 20 mm behind the lens the usual Hruby lens is D. The slit-lamp microscope is thus looking at a virtual image of the fundus in a plane somewhere in the anterior segment and must be moved a little closer to the patient than it would be for the regular external examination.
Hruby lens. The fundus image F' is formed in the posterior focal plane of the lens. The field of view is proportional to the size of the pupil as seen from the anterior focal point of the lens. To estimate the field of view in this method, it may be assumed that only rays emerging parallel to the axis will reach the objective of the microscope and the observer's eye. When emerging from the eye, these rays must have been aimed at the anterior focal point of the Hruby lens.
This field is of the same order of magnitude as the field in direct ophthalmoscopy; it is largest when the lens is closest to the eye. With the lens close to the cornea, the fundus image will be close to the fundus plane and approximately actual size. The magnification to the observer is thus largely determined by the magnification of the microscope. Binocular viewing and slit illumination are advantages over direct ophthalmoscopy, even at similar magnification.
Limitation to the posterior pole is a disadvantage. If the curvature of the posterior lens surface equals the curvature of the anterior corneal surface, the image formation will not change, but two reflecting surfaces will be eliminated, and image clarity will increase.
The use of a contact lens for fundus examination was perfected by Goldmann 21 of Berne, Switzerland His contact lens is known for the three mirrors incorporated in it. These mirrors positioned at different angles make it possible to examine the peripheral retina with little manipulation of the patient's eye or of the microscope axis Fig.
Three mirror contact lens by Goldmann. Two of the three mirrors are shown. They allow visualization of different parts of the fundus. The refractive power of the cornea is eliminated in the contact lens. The only effective refractive element left would seem to be the far less powerful crystalline lens. The retina is situated well within the focal length of this lens, and the crystalline lens will therefore form a virtual image of the fundus F in a plane F' behind the globe.
How can the microscope focus on an image that far back? We overlooked one other refracting surface: the plano front surface of the contact lens. F' is seen through plastic and vitreous. To the observer in air F' appears at F", through the same effect that makes a swimming pool appear shallower than it is. Because of this, the microscope again must focus on a plane inside the globe.