Ординатура / Офтальмология / Английские материалы / Practical Ophthalmology A Manual for the Beginning Ophthalmology Residents 4th edition_Wilson_1996

316 Chapter 13: Posterior Segment Examination

time a new section is examined. After examining the supcronasal ora serrata, lift and reposition the depressor superiorly, superotemporally, inferotemporally, inferiorly, and inferonasally to see the entire ora serrata and the posterior one third of the pars plana (Figure 13.14). The nasal and temporal horizontal meridians are usually examined last because they are often the hardest to examine for the beginning ophthalmologist.

Check with the patient periodically about discomfort. A topical anesthetic eyedrop is used if it becomes necessary to place the depressor directly onto the globe.

Having achieved a circumferential view of the ora serrata and the peripheral fundus, any fundus lesion is reexamined. The examiner locates the lesion on the mound produced by scleral depression and rolls the lesion over the indentation by moving the depressor with fine anteroposterior and sideways movements. Changing the angle of observation of a lesion on the fundus mound will allow the examiner to determine the lesion's relative elevation or depression and will highlight its margins.

Tips on scleral depression

•If the area of indentation cannot be seen, resist die temptation to

press harder and instead move the depressor gently into the line of sight, hugging the border of the tarsus.

•Release the pressure on the depressor if the patient begins to squeeze the eyes forcibly.

Figure 13.14 Sequence of circumferential scleral indentation through upper and lower eyelids. (A) Examination of superior periphery.The depressor tip is first placed superonasally (l),then moved superiorly (2) and superotemporally (3).(B) Examination of inferior periphery.The depressor tip is placed inferotemporally (4),

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good way to examine the optic disc and posterior pole, both clear and

yellow convex lenses are available; the vellovv filter absorbs ultraviolet and short-wavelength visible light of less than 480 nm but substantially distorts the color of the fundus image. Almost all condensing lenses used with the slit lamp are double-aspheric lenses, so it does not matter which side is held toward the patient. Lower-powered (eg, +60 D) lenses afford a more magnified view but are harder to focus. Some lenses have adapters that expand the field or increase magnification.

For indirect slit-lamp biomicroscopy, the condensing lens is held in the same way as for indirect ophthalmoscopy; the fingers can be simi-

determines the field of view, and the magnification is varied by turning the magnifying knob on the slit lamp. A setting of 10x or 16x is generally selected to begin die examination; higher magnification will not improve resolution. As with other types of posterior segment examinations, the right eve is usually examined first.

Moving the instruments viewing and illumination arms makes indirect ophthalmoscopy with the slit lamp a dynamic, creative examination. Light intensity with the slit lamp is often more than with the indirect ophthalmoscope, so the duration of viewing should i>e kept

Figure 13.15

Hruby Lens Biomicroscopy

The Hruby lens is a planoconcave high-minus lens (-55 D or -58.6 D) that neutralizes the optical power of the normal eve (+60 D) and forms a virtual, erect image ot the fundus. This preset, noncontact lens is fixed bv a movable arm to the slit-lamp biomicroscope (Figure 13.16). It is used to examine the posterior pole and vitreous cavity with the help of a fixation target for the other eye. Instructions tor examining the posterior segment with the Hruby lens attached to the slit-lamp biomicroscope appear in Clinical Protocol 13.4.

Overview of the examination

The optic nerve is first evaluated tor cupping and other changes. The peripapillary retina is then examined for the nerve fibers that enter the optic disc circumferentially. Nerve fibers are most easily seen adjacent to the superotemporal and inferotemporal edges ot the optic disc and are more obvious with moderately dark fundus pigmentation. Bright linear reflections are normally seen from closely packed bundles; as the nerve fiber layer thins during optic neuropathies, dark slits are seen. Increasing the light or putting in the red-free filter on the slit-lamp illumination arm can help the examiner to see the nerve fiber layer.

Attention is then turned to the macula. After examination with a 4 mm wide beam, a thin slit is focused onto the fovea. Sideways movement of a narrow slit beam can help to visualize the relative convexity

Contact Lens Biomicroscopy

;pheral fundus by applying scleral depression (a special conical holder with

an attached scleral depressor is available for use with the Goldmann three-mirror lens).

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Direct Ophthalmoscopy

The direct ophthalmoscope gives approximately 15x magnification (depending on the patient's refractive error) and is most useful lor examining the optic disc and posterior pole. The rheostat is generalU turned to get the brightest light, unless the patient is very light sensitive. Some instruments have a sliding polarizing filter for reducing glare. Besides the open light, filters contain different spot sizes, a streak projection, a calibrated grid, a fixation target, and a red-free filter. These illumination options and their uses are listed in Table 13.4. The grids are meant for localizing and determining the size of fundus lesions but are not normallv used because it is customary to describe lesions in terms of disc diameters. The slit aperture is not used much because of difficulties in seeing contour clues monocularly

The monocular direct ophthalmoscope (and its measuring reticule aperture) is particularly useful for viewing through a small pupil to

Table 13.4 Illumination Openings of the Direct Ophthalmoscope

Figure 13.18 Vitreoretinal drawing chart.The inner circle identifies the relative location of the equator, the middle circle represents the ora serrata, and the outer circle locates the ciliary processes (anterior limit of the pars plana).The roman numerals indicate the fundus meridians in clock hours.The labeled horizontal and vertical cross-sections are used for recording changes in the vitreous body.

to the fundus periphery (Figure 13.20). Residents should accurately depict fundus lesions by their color, size, shape, location, elevation, and relationship to retinal and choroidal blood vessels. The spherically shaped fundus cannot be easily mapped in an anatomically correct way on a flat drawing. For example, the equator of the eye always has a larger circumference than the ora serrata, but the opposite is shown on the standard fundus record. As a result, lesions anterior to the equator are exaggerated in size on the fundus record.