When observation is elected, lesions may be followed with greater precision. Where surgical intervention is indicated, the information gained is helpful in planning the approach.

Iris tumors

The presence of a typical morphologic appearance on ultrasound biomicroscopy may be helpful as a diagnostic sign. Several small, minimally elevated lesions involving the peripheral iris and clinically considered nevi have a similar appearance on ultrasound biomicroscopy (Fig. 7). They share the ultrasound biomicroscopic appearance of a small moderately thickened iris lesion not extending past the iris root. There is frequently a hypoechoic layer on the surface of these lesions, possibly indicating that the superficial layer is involved with the closely spaced cells of a surface plaque.

It is difficult to be too specific as to histologic diagnosis with ultrasound, even with the added

detail presented by ultrasound biomicroscopy. Resolution is not at the level that can differentiate individual cells. Malignant melanomas of the iris can be variable in their clinical and ultrasonic presentation. Ultrasound biomicroscopy can be helpful in a number of ways. Internal reflectivity varies considerably depending on the degree of vascularity and the patterns of internal cellular structure. Some melanomas show a linear internal pattern, others show a uniform reflectivity, while others show a large degree of internal vascularity.

Ciliary body tumors

One of the major assets of ultrasound biomicroscopy is the ability to differentiate a peripheral localized iris lesion from a ciliary body tumor that involves the iris (Fig. 8). These lesions can look very similar clinically as can be appreciated in Figs. 7A and 8A.

Ciliary body tumors can be easily assessed, although large tumors (>4 mm in depth) cannot be

Fig. 12. Iridociliary cyst (arrow) under the iris.

completely imaged because of sound attenuation. Small lesions that cannot be detected by conventional ultrasound can be defined by ultrasound biomicroscopy. Larger ciliary body lesions are detectable by conventional ultrasound, but ultrasound biomicroscopy shows improved internal detail of the superficial part of the tumor and frequently allows a more precise localization of the posterior and lateral boundaries. This information is important if iridocyclectomy is considered as a possible treatment.

The lateral extension of the tumor can be clearly defined, which can be important in the diagnosis of ring melanoma. These patients frequently present with hyperchromic glaucoma with delayed diagnosis. Ultrasound biomicroscopy is the best method of making the diagnosis in these cases.

Extrascleral extension of intraocular tumors

In cases of extrascleral extension, the relationship of the tumor to the extrascleral component can be defined (Fig. 9). The extrascleral component generally is located just above the internal ocular

tumor. Both of the lesions can be imaged simultaneously with ultrasound biomicroscopy. Frequently, the transscleral connection is imaged.37

Corneal involvement

Tumors that involve the cornea can present difficulty in determining the depth of corneal involvement. Ultrasound biomicroscopy can generally determine the thickness of the tumor and which corneal layers are involved (Figs. 10 and 11).38 This information can have a direct bearing on the type of treatment required. Tumors that are above Bowman’s membrane can generally be surgically removed, leaving the cornea intact. Deeper involvement may require a radiotherapeutic approach to preserve the cornea.

Cysts

Cysts are clearly imaged by ultrasound biomicroscopy.39,40 The usual clinical presentation of an iridociliary cyst is an elevation of the peripheral iris without iris involvement. The typical ultrasound biomicroscopic appearance of a thin-walled cyst with no internal reflectivity is diagnostic and essentially eliminates any question as to whether a lesion is a cyst or solid tumor (Fig. 12). If the iris is not involved, a cyst would be the most common clinical diagnoses. Occasionally, a ciliary body tumor with an extension under the iris can have this same presentation. Small cysts are also found occasionally as an isolated finding on examination for some other clinical indication or in association with solid lesions of the iris or ciliary body.

Peripheral choroidal tumors

The anterior aspect of peripherally located choroidal tumors can be imaged by ultrasound biomicroscopy.41 Although it is often impossible to measure these tumors through their greatest thickness, valuable information can be gained