Ultrasound is the most reliable method of measuring the shape of the tumor dome and altitude at the tumor apex. Sometimes tumor altitude can also be obtained from CT images if you can reconstruct a CT meridian slice which passes through the tumor apex. Fundus photos do not provide any altitude information at all.

Following the COMS convention, Plaque Simulator defines the altitude of the tumor apex as the distance from the inner sclera to the apex, and assumes the sclera is 1 mm thick under the tumor. Hence, the apex of a tumor of altitude 5 mm is actually 6 mm from the external sclera, and will also be 6 mm from the concave facial surface of a plaque assuming the plaque is touching the external sclera at the tumor base.

Ultrasound is also used to measure the nominal radial and circumferential dimensions of the tumor base. Tumor dimensions determined by ultrasound should be cross-checked with the dimensions obtained from fundus photos and CT imaging. If the various methods of measurement yield similar results you will have greater confidence in the validity of the model.

The most common tumor shapes are domes, peaks and mushrooms. Some examples are illustrated below.