Steps:
(1) Determine the weight of gold required to obtain the desired closure in grams. This is done by taping various weights to the outside of the upper eyelid.
(2) Multiply this weight by a factor that takes into account the mechanics once implanted within the eyelid.
weight to implant in grams =
= 1.152 * (weight of gold selected from the tape test)
The factor 1.152 comes from the ratio of the cosines of 2 angles relative to the vertical line drawn through the forehead viewed from the side (see Figure 1, page 1540):
(1) alpha (angle between the vertical and a line running along the plane of the outer surface of the upper eyelid)
(2) beta (angle between the vertical and a line running along the plane of the inner surface of the upper eyelid)
(COS(beta)) / (COS(alpha)) = 1.152
Limitations:
• This factor should work for most upper eyelids. If the thickness of the eyelid is increased then it may be necessary to measure the angles.
