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

2 76 Chapter 11: Anterior Segment Examination

Heavy pigment

Light pigment

Circular muscle

Figure 11.51 Gonioscopic anatomy of the anterior chamber and surrounding structures.

in Table 11.2 and shown in Figure 11.52. The Spaeth grading system adds information about the configuration and insertion of the peripheral iris (Figure 11.53).

Stains (dyes) instilled into the tear film can facilitate examination of the ocular surface bv highlighting, and making more evident, certain pathologic changes. The two most commonly used stains are fluores-1 cein and rose-bengal red (usually referred to simply as rose bengal).

Stains 277

Table 11.2 Shaffer Method of Grading Anterior Chamber Angles

Figure 11.52 Shaffer grading of anterior chamber angles: narrow angle (0°-20o), open angle (20°-45°).

Fluorescein

Fluorescein is available as an eyedrop mixed with a topical anesthetic (Fluress) or as fluorescein-impregnated paper strips. The strips are moistened with a drop of saline solution, artificial tear, or topical ophthalmic anesthetic and then touched to the inside of the lower lid.

Fluorescein does not stain corneal or conjunctival epithelium but readily enters and stains the stroma in areas in which epithelium is absent (or even in areas in which epithelial cells have loose intercellular junctions). Accordingly, fluorescein is very useful for detecting'

2JM . Chapter 11: Anterior Segment Examination

/

Figure 11.53 Spaeth's gonioscopic classification of the angle of the anterior chamber, based on three variables: (A) Angular width of the angle recess; (B) configuration of the peripheral iris; (C) insertion of the iris root

{a = highest insertion, e = lowest insertion). (Redrawn by permission from Shields MB:

Textbook of Glaucoma, 3rd ed. Baltimore: Williams & Wilkins; 1992.)

areas of epithelial deficiency that occur, for example, in cases of corneal abrasion, recurrent corneal erosion, or herpes simplex epithelial (dendritic) keratitis.

Fluorescein staining is best seen using diffuse slit-lamp illumination with the cobalt-blue filter; the blue light causes the dve to fluoresce a bright green color. T h e pattern and morphology of staining have diagnostic value (Figure 11.54).

Fluorescein is useful for detecting corneal perforations or wound leaks (Seidel test). Fluorescein is instilled into the tear film, which is observed with diffuse, blue illumination. Anv leak of aqueous humor onto the ocular surface can be detected bv noting a trickle of clear, nonstained fluid into the green tear film. Fluorescein is also used for measuring intraocular pressure with the (ioldmann tonometer (see

Figure 11.54 Typical patterns of staining with fluorescein or rose bengal and their diagnostic importance. (A) Dendritiform staining (dichotomously branching lesions, often with terminally bulbous swellings)—typical of herpes simplex keratitis. (B) Staining in the interpalpebra! zone of exposure in the dry eye (usually more so with rose bengal than with fluorescein) in keratoconjunctivitis sicca.

(C) Linear punctate staining in the superior cornea (caused by a foreign body entrapped in the upper palpebral conjunctival (D) Corneal abrasion or erosion (gross epithelial defect), usually just below the center of the cornea. (E) Eyedrop-

Chapter 12). Use of the dye for measuring tear film breakup time has been presented in Clinical Protocol 11.2.

Flare and cell in the anterior chamber should be graded prior to instilling fluorescein, as the dye can enter the chamber and produce a green, false flare. Fluorescein is nonirritating and mav be instilled without topical anesthetic.

Rose Bengal

Rose bengal is available as a 1% eyedrop or as an impregnated paper strip. The strip is used the same wav as are fluorescein strips. Unlike fluorescein, rose bengal stains abnormal and devitalized epithelial cells. Therefore, it is useful for conditions such as the drv eve (keratoconjunctivitis sicca) in which epithelial cells are not so much missing as just abnormal. Rose bengal also stains mucus and keratin.

Rose-bengal staining is best observed using diffuse slit-lamp illumination with the <n~een (red-free) filter. Stained areas are red with either

280 Chapter 11: Anterior Segment Examination

green or white light. Rose bengal (at least the 1% solution) is somewhat irritating and should not be used without first instilling a topical anesthetic agent.

Pitfalls and Pointers

Resist any tendency to limit die anterior segment examination to a cursory scanning of the cornea and anterior chamber, using only a single kind of illumination. Other important tissues (eyelids, conjunctiva, etc) and methods of illumination can provide valuable information.

It is often useful to examine the anterior segment (at least that portion posterior to the iris) after, as well as before, pupillary dilation. Otherwise, abnormalities of the lens, retrolental space, and anterior vitreous might be missed or inadequately evaluated.

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Position the patient at the slit lamp and adjust the instrument for diffuse illumination through the cobalt-blue filter.

Ask the patient to look straight ahead and to blink.

While observing the eye through the slit-lamp oculars, count to yourself the number of seconds that elapse between the blink and the appearance of the first dry spot. The dry spot will appear blue-black (because of the dark blue illumination) when the green-stained tear film pulls away from the area of breakup.

Repeat the test one or more times for each eye, because a single measurement might be falsely high or low. The normal breakup time (BUT) is at least 10 seconds.

Evaluating Flare and Cell

Set the slit lamp for a short (2-4 mm), medium-width parallelepiped, with the illumination at full brightness.

Situate the patient comfortably at the slit lamp and direct the beam at an angle of 45°-60° onto the midperipheral temporal cornea and the nasal iris.

Estimate the intensity of gray-white flare, using the dark pupil as background for viewing, and grade its intensity as follows:

0.5+ Very faint, barely visible (normal)

1.0+ Faint (normal)

1.5+ Mild

2.0+ Mild to moderate (closer to mild)

2.5+ Mild to moderate (closer to moderate)

3.0+ Moderate

3.5+ Moderate to severe *

4.0+ Severe

Without changing the slit-lamp settings, examine for the presence of cells (white dots rising and falling in the anterior chamber) and grade presence of cells as follows:

0.5+ Rare cell (normal)

12

Tonometry

onometry is the measurement of intraocular pressure ((IOP) It is performed as part of a thorough ocular examination to help detect ocular hypertension and glaucoma and to diagnose ocular hypotony (low IOP) in conditions such as iritis, retinal detachment, postoperative wound leaks, and occult perforations of the globe.

This chapter discusses measurement conventions and population means associated with IOP. In addition, it presents the variety of devices and methods currendy available and provides instruction in measuring IOP.