What is the Normal Degree of Eyeball Prominence?

The normal protrusion of the eyeball ranges from 12 to 14mm, with an average of 13mm, and the difference between the two eyes should not exceed 2mm. During the measurement, the examiner and the examinee sit opposite to each other. The examiner inserts the notch of the exophthalmos meter onto the temporal orbital rim of the examinee, instructs them to look straight ahead, and the value corresponding to the corneal apex seen in the two plane mirrors represents the protrusion of the eyeball. At the same time, the value of the distance between the two orbits can be obtained from the scale on the flat rod, and the orbital distance and the protrusion values of each eyeball are recorded. When conducting follow-up observations, the same orbital distance should be used. Methods for measuring the protrusion of the eyeball: (1) Ordinary ruler measurement method: A special transparent ruler or an ordinary ruler is used, with the zero point placed on the temporal orbital rim. The examinee is instructed to look straight ahead, and the examiner observes the corneal apex from the side to determine its position on the ruler (the vertical distance from the temporal orbital rim to the corneal apex), which represents the protrusion of the eyeball. The same method is used to examine both eyes and record the measurements. This method can only provide a general measurement. (2) Hertel exophthalmos meter measurement method: This is a commonly used and relatively accurate examination method. The exophthalmos meter mainly consists of a flat rod with a scale and two measuring devices. One measuring device is fixed to one end of the flat rod, while the other can slide freely on the rod to accommodate different orbital distances, and the orbital distance can be read from the scale on the flat rod. The measuring device is equipped with a small scale plate and two plane mirrors crossed at a 45° angle, which reflect the numerical value on the scale plate and the image of the corneal apex, respectively. Intraorbital masses are a common cause of eyeball protrusion, and most of them are benign, with hemangiomas being the most common. The onset is usually slow. The main manifestations include unilateral eyeball protrusion, normal or decreased vision, and mostly unobstructed eye movement. Common intraorbital masses include hemangiomas, meningiomas, lacrimal gland masses, and schwannomas. Traumatic eyeball protrusion: It is caused by intraorbital hemorrhage, tissue edema, and emphysema due to local trauma to the eye or orbit.