- Symmetric appearance of eyelids, orbit and face
- Ability to comfortably wear an ocular prosthesis
Cyst and microphthalmos
In a direct comparison of orbits with microphthalmos and cyst, 17 orbits were treated with surgical removal of the cyst, to facilitate fitting of a conformer, and 17 orbits had conformers fit without removal of the cyst (six additional orbits were treated in other ways). A similarly good cosmetic result was obtained in both groups (BJO 87:860, 2003).
The cyst itself can act as a tissue expander. A large orbital cyst can be a powerful stimulator of tissue expansion, even if it precludes conformer use.
When the cyst is not removed and the patient is not wearing a conformer, a reasonable compromise is to remove the orbital cyst at age 5, at which point orbital volume is about 90% of an adult and cosmesis becomes more important as the child begins school.
Aspirating the cyst contents can assist in fitting a conformer temporarily though reaccumulation is anticipated.
Ethanolamine oleate sclerotherapy can promote cyst resolution, after aspiration of the cyst contents, when there is no visual potential in the microphthalmic eye (OPRS 23:307, 2007).
The orbit is not fully grown until puberty and any effort at tissue expansion until then can be helpful. However, some parents (and ocularists) might be satisfied with eyelid expansion alone to facilitate prosthesis wear, and might elect to forego orbital surgery on the child.
Inflatable balloon expanders
An inflatable balloon tissue expander can be inserted as a means of manual tissue expansion, but inflation of the balloon can cause severe pain. With inflation, the orbital pressure can reach 150–200 mm Hg. The normal adult human orbital pressure is 3–6 mm Hg. Therefore the slow steady pressure exerted by a hydrogel tissue expander is preferred by some, since it creates pressures of approximately 20–30 mm Hg.
A bicoronal flap and lateral orbitotomy are sometimes needed for insertion of a balloon expander, although a newer balloon device that is implanted anteriorly and fixated to the orbital rim has been described (Am J Ophthalmol 151:470, 2011).
Wiese introduced self-filling hydrogel expanders in 1999 (J Craniomaxillofacial Surgery 27:72, 1999).
Hydrogel expanders are made of a highly hydrophilic compound consisting of N‑vinylpyrrolidone and methyl methacrylate, also commonly used to make soft contact lenses and some intraocular lenses.
The expected tissue expansion with a hydrogel expander is modest. In a study of 17 microphthalmic orbits treated with hydrogel expanders, the orbital volume expanded to 74%–83% of the contralateral side (J Am Ass Ped Ophthalmol Strab 16:458, 2012).
Hydrogel spheres are available in sizes including 6, 8 and 9 mm in diameter. The swelling time in vitro in normal saline is 1–4 days and final diameters of 12, 15, 18, 20, and 22 respectively are expected. The orbital sphere implant is placed through a small lateral soft tissue incision.
In vivo, the expansion occurs over several weeks. Maximum expansion is expected within 30 days and the expander can remain in place for several months.
It may be appropriate the leave the hydrogel implant in place for years but this risks potential complications including overexpansion.
Once removed the implant can be replaced with another hydrogel implant, a conventional orbital implant or a dermis fat graft.
Tissue wrapping of hydrogel implant
This might help control the rate of hydrogel expansion
In an in vitro study, 5.0‑ml orbital hydrogel expander implants were placed in beakers containing 0.9% sodium chloride solution, either unwrapped, or placed in porcine sclera wrapping, or porcine fascia lata wrapping (wrappings were 5.5 x 5.5 cm). Final volume of the fascia-wrapped implant was 3 ml compared with 5 ml for the sclera wrapped and control implants (OPRS 27:327, 2011).
As an alternative to orbital spheres, small expandable pellets can be inserted in the socket which are 8 mm in length, 2 mm in diameter and have an expected hydrated state of 0.24 ml in volume.
Dermis fat grafts
Autologous dermis fat grafts can be used to exert orbital pressure and expand the orbit and lids by taking advantage of natural growth of the graft. (JAAPOS 5:367, 2001). Late need for debulking of the graft due to excessive growth has been reported in children less than 4 years old at the time of graft placement (OPRS 14:81, 1998).
Harvest and placement of the dermis fat graft can be accomplished in the first few months of life, although many surgeons will initially initiate eyelid and fornix expansion until the child is 6–12 months old before considering orbital surgery.
Eyelid and fornix expansion
Serial placement of custom rigid conformers can expand the eyelid and fornices. Each conformer is larger than the previous one, enough to cause expansion but not so large that is causes pain or extrusion. Placement and exchange may require general anesthesia and may require a suture tarsorrhaphy.
Hemisphere hydrogel expanders are alternative options for expansion of the eyelid. Only 24–48 hours after placement of the hemisphere expander the fornices can be adequate to allow fitting of a first conformer.
The hemisphere implant is placed in the fornices, as a regular conformer, and held in place with fornix reconstruction sutures tied externally.
The hemispheres are available in sizes including 6, 8, 9 and 10 mm in diameter. The swelling time in vitro in normal saline is only 1–2 days and final diameters of 11, 14, 18, and 20 respectively are expected.
Regular follow-up is needed, even on a weekly basis, to the ocularist and/or surgeon while the eyelids are being expanded.
Specific complications from treatment
A hydrogel implant can migrate as it expands, possibly extruding rather than expanding the tissues, and extending beyond the orbital rim, precluding conformer or prosthesis wear.