Kaltreider et al used A-scan ultrasound of the remaining eye to determine the appropriate implant to use following enucleation of an eye. This can help determine the optimum volume prior to surgery. The authors are from the University of Virginia in Charlottesville.
Situations where remaining eye may not be a useful guide to determine replacement:
(1) buphthalmos
(2) microophthalmos
(3) severe anisometropia
(4) phthisis
(5) severely traumatized eyes
axial diameter for eye in mm =
= (A-scan diameter in mm) + 1
|
A-Scan diameter in mm |
Diameter of Implant for 70% Replacement |
Diameter of Implant for 80% Replacement |
|
20.0 mm |
18.5 mm |
19.5 mm |
|
20.5 mm |
19.0 mm |
20.0 mm |
|
21.0 mm |
19.5 mm |
20.5 mm |
|
21.5 mm |
20.0 mm |
21.0 mm |
|
22.0 mm |
20.5 mm |
21.0 mm |
|
22.5 mm |
21.0 mm |
21.5 mm |
|
23.0 mm |
21.5 mm |
22.0 mm |
|
23.5 mm |
22.0 mm |
23.0 mm |
|
24.0 mm |
22.0 mm |
23.5 mm |
|
24.5 mm |
22.5 mm |
23.5 mm |
|
25.0 mm |
23.0 mm |
24.0 mm |
|
25.5 mm |
23.5 mm |
24.5 mm |
|
26.0 mm |
24.0 mm |
25.0 mm |
|
26.5 mm |
24.5 mm |
25.5 mm |
|
27.0 mm |
25.0 mm |
25.5 mm |
|
27.5 mm |
25.5 mm |
26.0 mm |
|
28.0 mm |
25.5 mm |
26.5 mm |
|
28.5 mm |
26.0 mm |
27.0 mm |
from Table 1, page 38
volume of original eye in mL =
= 4 * PI() / 3 * ((((axial diameter in mm) / 2)^3) / 1000)
volume of implant in mL =
= 4 * PI() / 3 * ((((implant diameter in mm) / 2)^3) / 1000)
If the implant is scleral wrapped, the implant diameter required is the final implant diameter required minus 1 mm.
volume of prosthesis in mL =
= ((decimal fraction of eye to replace) * (volume of original eye in mL)) – (volume of implant in mL)
Situations where the implant may fail to give a good cosmetic effect:
(1) severe trauma (may sit too far posterior)
(2) anterior displacement (may be associated with proptosis)
Specialty: Ophthalmology
