Kaltreider and Lucarelli developed a simple algorithm for determining the size of the implant required for a patient after enucleation or evisceration. This can help avoid complex or hurried calculations during the operation. The authors are from the University of Wisconsin.
Factors affecting eye replacement:
(1) A spherical implant is placed in the posterior compartment while a prosthesis is placed in the anterior compartment.
(2) The eye reaches >= 85% of adult size by age of 2 years.
(3) While the maximal size is 4.2 mL, a prosthetic volume >= 3.0 mL is associated with problems for the patient. The ideal prosthesis contributes about 2 mL to the overall volume replacement.
Parameters:
(1) A-scan measurement of remaining eye in mm
(2) presence of hyperopia (axial length < 24 mm) or pediatric patient
(3) type of operation (evisceration vs enucleation)
|
Parameter |
Finding |
Points |
|
hyperopia or pediatric |
no |
0 |
|
|
yes |
1 |
|
type of operation |
enucleation |
0 |
|
|
evisceration |
1 |
total points =
= SUM(points for hyperopia) + (points for type of operation)
axial length in mm =
= (A-scan length in mm) + 1
diameter of implant in mm =
= (axial length in mm) – (2 + (total points))
|
Axial Length in mm |
Prosthesis Volume in mL |
|
20 (hyperopia) |
1.6 |
|
21 (hyperopia) |
1.8 |
|
22 (hyperopia) |
2.0 |
|
23 (hyperopia) |
2.2 |
|
24 |
1.6 |
|
25 |
1.8 |
|
26 |
2.0 |
|
27 |
2.1 |
|
28 |
2.3 |
NOTE: An alternative approach to the algorithm is to (a) calculate the volume of the eye based on the axial length, (b) subtract the volume of the prosthesis to get the implant volume, and (c) calculate the diameter of the implant in mm.
Specialty: Ophthalmology
