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The use of the adjustable suture strabismus technique has led to a revolution in strabismus surgery. Previously, depending on the surgeon's experience, the results of strabismus surgery may not have been very predictable after a first eye muscle procedure, let alone subsequent ones. The advent of adjustable sutures permitted ophthalmologists to adopt new attitudes towards their patients. Firstly, non-experienced ophthalmologists could attempt surgery, knowing that if their approach were not quite right, they would be given a second chance during the postoperative adjustment process. Secondly, experienced strabismus surgeons could realistically foretell a successful outcome rate often exceeding 90%—a prediction practically impossible without the use of adjustable sutures.
As with any innovative procedure, surgeons then attempted to improve the technique. The paper in this issue of theBJO (p 80) by Choi and colleagues is such a potential improvement. Their premise is that the further in time from the actual strabismus surgery the adjustable process is performed, the higher the success rate should be. Delaying the adjustment as long as 6 or more days after the surgery has been reported, but not often practised. This premise assumes that in the immediate postoperative period a number of factors may still change, which would affect the ultimate ocular alignment. Among these factors may be further healing of the muscle and conjunctiva, oedema of adjacent tissues especially Tenon's capsule, ability of the patient to properly focus on the fixation target, and changes in the length-tension curve of the operated muscle(s). Despite these concerns, Ruben and Elston, and Biglan and associates have reported good results when adjustment is performed within minutes of completing the initial surgery, often with the patient still on the operating table. These authors would not find ADCON-L useful because they used early adjustment. Even for those authors who perform the adjustment process later than the immediate postoperative period, there has been little difficulty with adjustment. Spierer and, later, Velez and associates reported adjustment at about 24 hours postoperatively to be essentially as easy as at 6 hours with similar long term results. Thus, the approach of Choi and colleagues might be most useful for adjustments performed beyond 24 hours after initial surgery.
The ADCON-L apparently works by preventing adhesion between tendon and sclera. This is thought to be accomplished by blocking fibroblast migration, either chemically or mechanically. In a multicentre controlled trial in 298 patients undergoing lumbar discectomy, ADCON-L significantly reduced peridural scar formation, postoperative related pain, low back pain, and permitted more movement of extremities. After lumbosacral discectomy, epidural scar tissue was found to be absent or minimal. Other agents have been placed on the sclera for the same purpose but have not found common use. Some of them, such as mitomycin-C and 5-fluorouracil, are potentially toxic to the eye, whereas ADCON-L appears to be non-toxic.
Another question to raise about this use is if the delayed healing imposed by ADCON-L, at least in the rabbit model, will leave the eventual adhesion between tendon and sclera weaker than it would otherwise be. If so, the impaired adhesion could further weaken the effects of a muscle recession or resection. In addition, the muscle could more easily dehisce off the globe after trauma. The authors' finding that the disinsertional force 3 weeks after surgery was no different whether an eye had been treated with ADCON-L or balanced salt solution is encouraging. But their other finding that even at 3 weeks postoperatively, the eyes treated with ADCON-L revealed less fibrosis on histological examination is worrisome with regard to the structural integrity of the scleral adhesion.
If the adjustment will be delayed more than 24 hours after surgery, another consideration is patient convenience. With one or more long sutures in the conjunctival sac, the patient will probably be patched, which would preclude much social interaction. In addition, the long sutures would cause discomfort in many patients. Perhaps these negative aspects of deferred adjustment could be justified if the long term result from a deferred adjustment could be proved to be significantly better than adjustment within 24 hours of surgery.
The results of Choi and associates are stimulating. A human trial of ADCON-L and performing the adjustment more than 24 hours after initial surgery should address a number of questions. In the human, will ADCON-L prove as effective and non-toxic as shown in the rabbit model? Does the deferred adjustment improve long term results? Is the discomfort of maintaining long sutures in the eye for a prolonged period tolerable to the patient? Will a muscle adjusted after use of ADCON-L maintain a weakened attachment to the sclera? These initial results in a rabbit model are sufficiently convincing and exciting to justify a human trial to answer these questions.
Video Reports (www.bjophthalmol.com)
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