Post-enucleation problems

Socket problems following childhood enucleation

Enucleation is the oldest treatment for retinoblastoma. It is widely available even in less developed countries, can be curative when the tumour is limited to the eye and is suitable when the eye cannot be salvaged by other means, or other treatment options are unsuitable.

Enucleation is required in up to 70-80% of unilateral cases and one eye in 20% of bilateral cases will be advanced enough to necessitate enucleation. The advent of newer treatment like sub-tenon and intra-arterial chemotherapy where available have reduced but not eliminated the need for enucleation. As a result, enucleation continues to be a valuable treatment for advanced intra-ocular retinoblastoma, and can be lifesaving in some cases.

The loss of an eye can be very traumatic for the child and their family, including siblings and parents. It is therefore imperative that every effort is taken to provide support through the difficult peri-operative period, continuing into many years after into adulthood.

It is also important to ensure a cosmetically optimum result to minimise disfigurement, and minimise the psycho-social impact on the child and family.

This article discusses the various problems encountered following enucleation, and strategies for their management

Volume deficiency

One of the biggest challenges of enucleation in young children, particularly under one year of age is volume replacement following removal of the eye. The volume of the adult eye is 6.5 cc (smaller in children) and needs replacement for cosmesis, and to stimulate orbital growth. This is done at the same time as enucleation with an orbital implant. 80% of the growth of the eye is complete by two years of age. It follows that the eye and bony orbit of the young child is significantly smaller than the adult size.

Orbital implants are typically spherical, and available in sizes 16,18,20 and 22mm diameter. Most adult eyes will be replaced with 22mm orbital implants to provide optimum volume replacement. Due to the smaller bony orbit in children, it is unusual to use 22mm implants. The aim in children is to use the largest possible implant that will fit within the bony orbit, leaving sufficient room for the artificial eye fit. This can be estimated using orbital sizers during surgery. 18-20mm implants are used in younger children, particularly infants, and 22mm might be suitable in older children.

It is therefore expected that children undergoing enucleation at a young age will develop a degree of volume deficiency as they grow. The problem is compounded if the eye has previously received radiotherapy resulting in arrested growth of the bony socket and limiting the size of the implant that can be used. Radiotherapy also results in loss of the orbital fat and soft tissues, further accentuating the volume deficiency. (image below)

Rarely, the implant might have to be removed due to complications, and the lack of an implant in childhood will result in failure of growth of the orbit. It is therefore important to replace the lost volume either with another implant, or a dermis fat graft to restore the volume and promote symmetric bony growth.

Management of volume deficiency

The volume deficiency can be managed in several ways. The use of a larger prosthesis might be sufficient in some cases. If a small implant has been used, further surgery to exchange the implant for a larger one can be considered – such surgery carries its own risks. Fat injection into the orbit (Coleman technique), or overlaying a dermis fat graft (discussed later) on the existing implant can be useful techniques to add volume. Temporary orbital filler injections with hyaluronate (Restylane, Macrolane) can be used to assess the effect of injections, and to demonstrate the effect to the patient and parents before undertaking a permanent procedure with fat injections.

Fornix shortening

The conjunctival fornix is the space behind the eyelid where the artificial eye (prosthesis) fits. The fornix must be of sufficient depth to permit optimum fit of the artificial eye. Fornix shortening can occur following radiotherapy, socket inflammation or infection resulting in prolonged periods when the prosthesis is not worn, due to poor surgical technique, or following aggressive healing response of the body to the orbital implant. In some cases, there is no evident cause (idiopathic).

Fornix shortening can result in difficulty fitting the prosthetic eye, excessively wide open eye (wide palpebral fissure),inturn of the lower eyelid (entropion) and in extreme cases, inability to wear a prosthetic eye. This could be managed without surgery in some cases by using an oversize prosthesis, and then gluing the eyelids together with medical grade cyano-acrylate glue (similar to superglue) that lasts a few weeks and stretches the fornix. Gradual stretching with progressively larger prosthesis can give a good result.

If this is unsuccessful or not feasible, buccal mucous membrane grafting can be considered where the inner lining of the lower lip or cheek is transplanted to the socket to increase the surface area.

Another option is to use a thin dermis fat graft to increase the surface lining and deepen the fornices. These procedures could be combined with special stitches to deepen the fornix that are left in for several weeks.

Post radiotherapy sockets pose a particular challenge as they have reduced blood supply, and any surgical procedure carries a high failure rate.

Palpebral fissure problems (including ptosis)

The palpebral fissure is the opening between the eyelids and is approximately 10mm wide (high). Droop of the upper lid (ptosis) resulting in narrowing of the palpebral fissure can occur in upto 10-15% of cases following enucleation. Volume deficiency resulting from a small implant is a common cause, and can be remedied by enlarging the prosthesis, or adding volume with a fat injection of graft (described above).

It can sometimes be a real challenge to achieve the delicate balance between fitting a large enough prosthesis to lift up the eyelid, and yet not making it so big that it sits too proud. In some cases, we have to accept a compromise.

If there is no volume deficiency, or it has been addressed, the possibility that the levator muscle that elevates the upper eyelid has slipped from its original attachment to the upper lid must be considered. Such cases can be dealt with by performing ptosis surgery either by the posterior approach (levator advancement performed from behind the eyelid)) or rarely anterior (skin) approach levator repair, or brow suspension surgery with artificial material like silicone or PTFE (Ptose-up).

If the palpebral fissure is wider than usual, it could be due to an oversize prosthesis which needs reduction in size, or sagging of the lower lid from the weight of the prosthesis.

Granulomas and bleeding

Granulomas are reddish lumps of tissue that can appear in the socket in response to chronic irritation from the prosthesis or abnormal healing following surgery. They can result in bleeding and discharge. Granulomas can be the harbinger of implant exposure, and warrants careful examination.

Discharge

Discharge from the socket is a common and very bothersome problem. There are several causes of socket discharge including abnormal blink resulting in disordered eyelid/lacrimal pump, and impaired drainage of tears, or irritation/inflammation/infection from the prosthetic eye, and rarely from implant exposure or granulation tissue. One mechanism proposed by some is chronic bacterial overgrowth in the socket. Frustratingly, in many cases, there is no evident cause.

Managing the discharging socket

One must look carefully for implant exposure in any case with new onset discharge, and if found, it must be corrected. The prosthesis fit must be reviewed, particularly if there are signs of conjunctival irritation (papillary changes). Anti-allergy or steroid eye drops can be used for low grade inflammation. If there is overt infection, short courses of anti-bacterial eye drops or ointment such as Polyfax eye ointment or Chloramphenicol can be used. Some cases benefit from long tem use of antibiotic drops, and such cases could benefit from the use of povidone iodine eye drops 1% where available to minimise use of antibiotics and avoid developing antibiotic resistance.

Exposure

There are several types of implants , including acrylic balls,Hydroxy-apatite (Synthetic coral), Bioceramic and Medpor (Porous polyethylene). Apart from the acrylic ball, the rest of the implants are bio-integrable, ie they integrate into the surrounding tissues. Despite this, some implants will erode through the overlying tissues, and result in exposure. This could be due to an oversized implant, poor prosthesis fit, surgical technique, infection, and following radiotherapy. There is a rate of implant exposure with all implants, quoted in various large published studies between 2-5%.

Treatment options

The treatment depends on the extent of exposure. If the exposure is small, and covered with granulation tissue, it can be watched if the patient is unwilling for surgery, treating intermittently with antibiotic drops to minimise risk of infection. However, the optimum treatment is surgical repair as there is a significant long-term risk of infection tracking deeper into the orbit, and compromising the implant.

Primary repair can be performed for small defects, exploring the wound followed by repair in layers. For larger defects, it is advisable to use grafted tissue to close the gap as primary repair will shallow the conjunctival fornix (see above) and compromise subsequent prosthesis fitting. The various tissue grafts used include deep tissue (fascia) from the temple deep to the scalp (temporalis fascia) or the outer aspect of the thigh (fascia lata), the tough lining of the bones of the scalp (pericranium), or the deeper layers of skin with some underlying fat (dermis fat graft). Some surgeons use donor sclera (the white of the eye from donated eyes).

If this is successful, the implant can be retained, minimising further surgery. If there is overt infection of the implant, or the patch graft procedures are unsuccessful, the implant might have to be removed and exchanged with a new implant. This is usually done as two separate procedures to minimise risk of the second implant developing infection. Another option is to replace the infected implant with a dermis fat graft, with sufficient fat to restore the lost volume.

The secondary implant procedure results in a more predictable volume replacement, unlike the dermis fat graft which can shrink or even grow over time. It also gives good movement, and does not result in additional scars. However, if there is deficiency of the surface lining (conjunctiva), the dermis fat graft is preferred as it adds surface lining, and minimises fornix shortening compared to the secondary implant. There is also no risk of infection of the dermis fat graft as it is autologous (taken from the patient’s own body), but it is best to defer the insertion of the secondary implant or dermis fat graft till all signs of infection have subsided. Dermis fat grafts are taken from the abdominal wall (just above the groin), or the buttock (gluteal region).

Poor Movement

Good movement of the prosthetic eye is a desirable outcome of enucleation. It is important to have realistic expectations as movement of the artificial eye will be less than the fellow (normal) eye. As most surgeons will attach the muscles surgically to or around the implant at surgery, this will result in fairly good up, down and side to side movement of the implant within the socket, replicating movement of the normal eye. However, it is important to remember that not all this movement is transmitted from the implant to the prosthetic eye, and the prosthetic eye moves less than the observed movement of the implant within the conjunctival socket.

The mechanism by which the prosthetic eye moves is quite complex and counter-intuitive. Contrary to popular belief, most of the movement is passive. There is little movement transmitted from the moving implant to the prosthetis eye. Instead, the muscles that are attached to the implant also attach into the conjunctival fornices, and drag the fornix in the desired direction when the fellow eye initiates movement. This results in deepening of the fornix, and the prosthetic eye follows into the deep fornix. The movement is therefore passive rather than active, and explains why movement is generally best in downgaze (assisted by gravity and the weight of the prosthesis), least in upgaze, and moderate from side to side) in most cases.

It is therefore important to achieve the optimum balance between implant size and prosthesis to allow room for movement. Too big an implant will limit movement as there will be little room for movement, and too small an implant will necessitate a larger and heavier prosthesis which will limit movement.

The technique of pegging implants was described over a decade ago, but did not gain wide acceptance. It involved performing an MRI scan to check if blood vessels had grown into the hydroxyl-apatite implant, following which a hole was drilled into the implant. The prosthesis was fitted with a peg on its rear surface that coupled with the hole in the implant. It was expected that the movement of the implant would be directly transmitted to the prosthetic eye, maximising movement. However, the hole promoted infections and bleeding from the socket, without a significant improvement in prosthesis movement, and this procedure is rarely performed now.

The role of the prosthetist

Good prosthetic care is vital to a successful outcome following enucleation. The experienced prosthetist can create custom-made shapes and moulded prosthesis for unusual shaped sockets. They can make lifelike temporary prostheses which are preferred to clear shells for use immediately after enucleation to minimise emotional trauma for the child and family.

Acknowledgements

This article appears with thanks to Manoj V Parulekar, Consultant Ophthalmologist, Birmingham Children’s Hospital; Maureen McCalla, Retinoblastoma Specialist Nurse, Retinoblastoma Unit, Birmingham Children’s Hospital; and Zoe Squires, Prosthetist, National Artificial Eye Service, UK

We are grateful to Bryan Hyde Jones retired prosthetist; the expert prosthetists of the National Artificial Eye Service UK, Wales and Scotland; Bruce Richard and Hiroshi Nishikawa, plastic surgeons, Birmingham Children’s Hospital; and most importantly our patients and their families from whom we learn so much.

References

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