Pathophysiology See comments in “General Pathology”. Primary prevention Since all strabismus surgeries carry an element of risk, the goal is to reduce the incidence of adverse post-postoperative outcomes with the realization that is not possible to eliminate surgical complications. The risk of an unsatisfactory eye alignment after surgery is minimized by a careful and complete pre-operative evaluation and by meticulous surgical technique with emphasis on good exposure, lighting, and precise intraoperative measurements to verify that proper surgical dosages were obtained. The pre-operative evaluation can include multiple consistent measurements of the eye deviation and prism adaptation to assess both surgical angle and post-operative fusion potential. The intra-operative procedure can include steps to minimize the measurement error induced by the curvature of the globe, particularly for large recessions, and to ensure proper placement of the muscle sutures to capture of the muscle belly, not just the muscle capsule, and minimize sag of the new muscle insertion. Limiting surgical dosages could reduce the risk of a change in the post-operative refraction, but as a practical matter simply monitoring post-operative vision and adjusting the refractive correction to maximize vision if necessary can treat this self-limited complication. The risk of post-operative intractable diplopia can be minimized by careful assessment of the binocular potential prior to surgery and by choosing conservative surgical dosages and employing adjustable suture techniques to minimize the chance of an overcorrection. Diplopia is a necessary but short-lived complication of eye muscle surgery in many patients. The risk of scleral perforation can be minimized by using a magnified view of the surgical field and placing flexible spatulated needles through the sclera with good exposure and clear visibility of the needle tip at all times. Also, the depth of the scleral suture is easier to judge when placing the scleral sutures through the original insertion and using a “hang-back” technique for recessions. The risk of a post-operative infection can be minimized by aggressively treating any superficial infection or bacterial overgrowth pre-operatively, by using meticulous sterile technique during surgery, and by using post-operative antibiotics. The risk of an allergic reaction can be minimized by carefully reviewing the patient’s medical history and avoiding medications that might cross-react with known medication allergies. The risk of a foreign body granuloma can be reduced by avoiding gut sutures and by proper draping to keep lashes out of the surgical field. The risk of a conjunctival inclusion cyst can be minimized with careful and complete wound closure. Preplaced marking sutures can allow easy identification of the edges of the conjunctival wound at the end of surgery, allowing easy distinction from the underlying Tenon’s capsule. The risk of conjunctival scarring can also be minimized by careful wound closure. For resections, debridement of Tenon’s capsule from the undersurface of the conjunctiva and recession of the conjunctival wound from the corneal limbus may help prevent the thickened anterior conjunctival scar that can occur after a large resection. The risk of fat adherence can be minimized by recognition of the violation of the retro-orbital fat intra-operatively. The posterior opening in Tenon’s capsule can be repaired in layers with absorbable sutures to prevent contact between the globe and muscles and orbital fat. The risk of a dellen can be minimized by utilizing a fornix incision instead of a limbal incision or by recessing the conjunctiva away from the limbus after a limbal incision. The risk of anterior segment ischemia can be minimized by limiting the number of muscles operated on in each eye, by utilizing botulinum toxin, and by using special surgical techniques to spare the ciliary vessels during muscle surgery. A fornix conjunctival incision may have a slightly reduced effect on anterior segment perfusion compared with a limbal incision. The risk of eyelid retraction or ptosis can be minimized by limiting the surgical dosages applied to the vertical rectus muscles and by carefully dissecting the lid retractors away from the extraocular muscles during surgery at least 12-15 mm posterior to the insertion. The risk of a lost muscle can be minimized by using gentle surgical techniques when isolating and securing the muscle belly and rotating the globe towards a resected muscle rather than pulling the tight muscle anteriorly. The risk can also be reduced by direct placement of scleral sutures at the site of the new insertion, instead of utilizing a hang-back technique from the original insertion. The risk of a slipped muscle can be minimized by using full-thickness bites when passing the muscle suture. Special groove hooks or muscle clamps can be used with tight muscles to provide more space to securely place the muscle sutures to encompass the muscle belly in addition to the muscle capsule. Some physicians prefer to use two locking bites instead of the traditional one locking bite to ensure adequate capture of the muscle fibers.
Posted on: Sat, 06 Jul 2013 09:58:20 +0000
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