Ординатура / Офтальмология / Английские материалы / Ultrasonography of the Eye and Orbit 2nd edition_Coleman, Silverman, Lizzi_2006

Figure D.2 Use of a sterile latex sheath with saline can provide an ideal standoff for examining infants or severely traumatized eyes. This can be used with A- or contact B-scan equipment (see also DVD).

With the patient supine on the examination table, we place a plastic Steri-drape around the eye to provide the container for the water bath. The Steri-drape is an ocular drape that has a central opening so that no plastic comes between the transducer and the eye. The drape may be applied directly to the skin, but we have found that perspiration, oily skin, or heavy makeup prevents a water-tight seal. Therefore, we routinely elect to paint a ring of collodion around the patient's eye, using a cottontip swab. Leakage of saline occasionally occurs inside the nasolabial fold or between the eyebrows, and care should be taken to allow at least a quarter-inch of plastic material to cover these areas. The collodion should never be passed directly over the patient's open eye, and, for extra caution, the patient is instructed to keep his or her eyes closed.

Once the drape is in position, a metal hoop is centered over the patient's eye. The edges of the drape are brought up through the hoop, but the hoop is not clamped. A drop of proparacaine is placed in the patient's eye, and a sterile Barraquer speculum is then gently inserted to hold the eyelids open. On occasion, the patient will move his or her head during this process, and, if the drape has been clamped, it might be torn loose.

Following the insertion of the speculum, the clamp is used to secure the edges of the plastic, and sterile warmed

P.180

saline is poured into the edge of the drape but not directly onto the eye. We preheat the saline to body temperature to minimize discomfort to the patient. For the experienced examiner, this initial patient preparation usually takes 2 minutes.

The transducer is then swung into position above the eye (Figure D.3; see also DVD), and the transducer is dipped to just below water lever. Horizontal scans are then made across the eye, and the display is observed. Vertical scans are used in selected cases to better portray the situation. The two-dimensional pictures on the oscilloscope provide a real-time monitor for the procedure. The examiner continually observes the A- and B-scan traces to abstract maximum acoustic information.

By changing transducer frequencies, certain features more amenable to greater resolution (higher frequency and/or focused transducers) or greater sensitivity (lower sensitivities and/or unfocused transducers) may be portrayed.

The total examination time varies according to the difficulty of the case. A simple precataract extraction screening procedure can take as short as 4 or 5 minutes, whereas a thorough tumor differentiation study using multiple frequencies can last up to 20 minutes. The total examination time should not exceed this period, because the anesthetic becomes ineffective, and the patient becomes uncomfortable.

Figure D.3 The plastic Steri-drape water bath system developed by Coleman for routine immersion scanning.

An ocular Steri-drape is placed around the eye, and approximately 400 cc of normal saline solution provide an easily accessible acoustic view of the eye and orbit. The transducer is then placed above the patient's eye (see also DVD).

Rarely does a patient not readily cooperate, but, if this is the case, contact scanning conducted through the lids on A- or B-mode alone is used. In the examination of children, we prefer to use anesthesia up to age 5 years. Diazepam (Valium) 10 mg 1 hour before the procedure has been useful for children ages 5 through 8.