Procedure for Fitting Phase II: Impression Moulded
Scleral Ocular Prosthesis
(For the Acquired Dysfunctional
or Phthisical Globe)
Congratulations on your double accomplishment of completing
the wearing schedule for Phase I Scleral Trial Shell for
the prescribed time (your waking hours), and mastering the
technique of inserting and removing the shell. We can
now describe the procedure involved in fabricating the Phase
II Scleral Ocular Prosthesis.
Laboratory Sessions: The amount of time required to
duplicate the iris color striations is dependent upon the
thinness of the trial shell at the selected cornea/pupil
apex. Since, our objective is to use as much of the
anterior-posterior thickness for a clear acrylic cornea to
obtain a lifelike 3-dimensional effect. Therefore,
the scleral trial shell (thickness) measurement will determine
which of the following methods is appropriate for duplicating
the iris color.
Method 1: Surface Iris Painting
Visit #1 (Estimated Duration:
1 hour)
If it is a thin scleral shell measures less than 1½
millimeters (no loss of global volume), a duplicate of the
trial shell would be made in white acrylic. (1st
curing cycle)
Visit #2 (Estimated Duration:
2-3 hours)
A
circle would then be scribed on the white scleral shell for
iris diameter and pupil center. The entire anterior
surface would be trimmed down to ¼ millimeter.
The iris painting would then be painted together with scleral
tints and simulation of the vascular pattern. A clear
acrylic overlay would then be applied to replace the white
acrylic that had been trimmed away. (2nd
curing cycle) Another
option, providing this was only a scarred, disfigured cornea,
would be to utilize your own sclera by now trimming away
most of the white acrylic from the posterior side of the
shell. This would be replaced with clear acrylic (3rd
curing cycle).
Method 2: Curved Iris-Cornea Die Plate
Visit #1 (Estimated Duration:
1½ hour)
If the thin scleral shell measures 1½ to 2½
millimeters it would be marked for pupil/iris center with
an attached plastic stem. (A two piece mold would be
made of the scleral trial shell.) A
specially designed curved iris-cornea die-plate would be
used for the iris painting. This technique involves
placing an aluminum foil over the curved surface and painting
on its surface. When a clear acrylic mixture is compressed
(1st curing cycle) and cured under heat and pressure,
the painted iris will become the posterior surface of the
clear acrylic cornea. The iris cornea would then be
embedded in a white acrylic mixture (2nd curing
cycle).
Visit #2 (Estimated Duration:
45 minutes to 1 hour)
This entails the simulation of the scleral tints and vascular
pattern (white portion of the eye). The iris is exposed
to the desired iris diameter. (Red nylon and cotton
threads are applied in varying thickness to create the 'bloodshot'
appearance, and various tints are added to simulate the scleral
tones. A clear acrylic overlay would then be applied
to replace the white acrylic that had been trimmed away.
(3rd curing cycle)
Method 3: Flat Acrylic Iris Disc
Visit #1 (Estimated Duration:
1 hour)
If
the scleral trial shell measures more the 2½ millimeters
at pupil center, it would be marked for pupil/iris center
with an attached plastic stem. (A two piece dental
stone mold would be made of the scleral shell.) A flat
iris disc would be selected with the proper pupil size and
placed on
a tapered spindle for the painting. The completed iris
artwork is then placed in an iris-cornea die plate for a
clear acrylic polymerization with an attached stem at its
apex. (1st curing cycle), followed by its
being embedded in white plastic in the two piece mold made
from the trial shell. (2nd curing cycle)
Visit #2 (Estimated Duration:
45 minutes to 1 hour)
This session entails the simulation of the scleral tints
and vascularization (white portion of the eye). This
is accomplished by first exposing the embedded iris-cornea
surface to the desired iris diameter. Red nylon and
cotton threads are applied in varying thickness to simulate
the vascular pattern, and various tints are added to match
the scleral tones. Upon completion this phase will
require a clear acrylic overlay (which replaces the amount
of white acrylic that was removed to expose the iris) under
a controlled heat and pressure curing cycle. (3rd
curing cycle)
Final Visit
for all three options: (Estimated Duration: 45 minutes to
1 hour)
The final session would be the fitting of the completed impression
moulded scleral ocular prosthesis. We would then review
the insertion and removal techniques, and stress again the
need for good hygiene care of eye, lids and prosthesis.
A follow-up session is then scheduled for 4 to 6 weeks to
check for comfort, fit and cosmesis. It is advisable
to make notes of any questions you need answered, or any
wearing problems you may have experienced in the interim.
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