Ophthalmic Echography

Echography (ultrasound, ultrasonography or sonography) is a diagnostic test using high frequency sound waves that is utilized by many medical specialities. In ophthalmology, echography is primarily employed to provide additional information about the interior of the eye and surrounding areas.

The ultrasound examination is performed after anesthetic drops have been applied to the eye. A small probe, that both emits and receives the sound waves, is gently placed on the eye surface. The emitted sound waves are reflected back to the probe from various tissue surfaces within the eye and appear on the screen of the ultrasound instrument. The resultant images are referred to as echograms. The echographer (sonographer or ultrasonographer) carefully observes the echograms and takes photographs of the images.

In the COMS, the ultrasound examination is performed with Standardized Echography which combines two display methods, B-scan (two dimensional) and A-scan (one dimensional) (Figures 1 and 2). This comprehensive method serves to help confirm the diagnosis of melanoma, exclude tumor extension beyond the eye, and measure tumor size.

Echography of Normal Eye

Figure 1
B-Scan Echogram

Figure 2
A-Scan Echogram

Patients undergo ultrasound examination upon enrollment in the study, and those randomized to Iodine-125 plaque therapy are re-examined at each follow-up visit.

All COMS Echographers receive specific training as directed by the Echography Center located at Mars Hill College in Mars Hill, North Carolina. The training has been carefully developed so that all ultrasound examinations are performed in a uniform manner. There is at least one certified COMS echographer in every participating clinical center. The standardized protocol provides maximum ultrasound information about each examination to ensure the highest possible quality.

Ultrasonic tumor evaluation in the study is achieved through the performance of three primary examination techniques. B-scan is used to assess topographic features including tumor shape, surface contour and boundaries (Figure 3). Standardized A-scan is then employed to evaluate the lesion's internal structure and reflectivity (Figure 4) as well as kinetic properties (consistency and vascularity). Finally, tumor height (elevation) is determined by measuring both B-scan and standardized A-scan echograms.

Echography of Choroidal Melanoma

Figure 3
B-Scan Echogram

Figure 4
A-Scan Echogram

The ultrasound data obtained at each COMS clinical center is sent to the Echography Center for evaluation. The echograms are evaluated by highly skilled individuals who independently confirm the diagnosis, assess for tumor extension beyond the eye, and carefully remeasure tumor height. The results of these evaluations are compiled and sent to the COMS Coordinating Center at Johns Hopkins University for computer analysis.

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