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Central tenotomy and central plication are just two options that can correct very small deviations previously not amenable to surgical treatment.
Reviewed by Dr Yi Ning Strube.
Minimally invasive strabismus surgery in adults is quicker and safer than the traditional method, according to Dr Yi Ning Strube, an associate professor and director of paediatric ophthalmology and adult strabismus at Queen’s University in Kingston, Ontario, Canada.
During her presentation at the 32nd Annual Jack Crawford Day, an annual paediatric ophthalmology update held virtually in April 2022 by the University of Toronto and The Hospital for Sick Children in Toronto, Canada, Dr Strube described the advantages of the minimally invasive approach.
“Minimally invasive strabismus surgery is less risky to the patient, and less painful, with faster recovery compared to our traditional strabismus procedures,” she explained. “It is easier and faster for the surgeon and therefore less stressful.”
One of the minimally invasive strabismus surgical techniques is the central tenotomy, which can be performed with the patient fully awake as an in-clinic procedure. “This procedure can correct small vertical tropias of 1 to 2 [prism dioptre],” Dr Strube explained. “It is a simple and quick procedure that you can do under topical anaesthesia.”
Dr Strube discussed a case in which a central tenotomy was used on a surgeon who had a retinal detachment that was repaired but had residual vertical diplopia and did not want to wear prism glasses. The procedure provides a surgical alternative to prism spectacles; it corrects very small deviations previously not amenable to surgical correction, as standard rectus muscle recessions correct much larger deviations.
A study1 published in 2009 of 15 consecutive cases by Dr Kenneth Wright, a paediatric ophthalmologist and founder of Wright Center for Pediatric Ophthalmology and Adult Stabismus in Los Angeles, California, United States, looked at the success of the central tenotomy procedure he developed to correct diplopia associated with small-angle strabismus.
Patients in the series were aged 35 –86 years, and 11 of 15 were 60 years and older. All 15 patients had binocular diplopia, and five of 15 were using prism glasses prior to surgery. Dr Wright reported successful treatment of hypertropia with the central tenotomy, but not for esotropia; the procedure is therefore not recommended for patients with esotropia as they often have a much larger underlying esophoria.
Dr Strube outlined a few important steps to keep in mind when performing the central tenotomy. Firstly, topical anaesthetic is applied to the eye, followed by a drop of phenylephrine 2.5% to blanch conjunctiva; this allows for improved visualisation of the anterior ciliary vessels, which should be avoided. Additionally, a drop of antibiotic should be applied.
A 0.50- or 0.75-toothed forceps is used to grasp the central tendon of the rectus muscle through the intact conjunctiva. “You want to move the eye and be sure you haven’t just grasped the superficial conjunctiva,” Dr Strube said.
“Make sure you are using blunt Westcott scissors and be very careful not to go too deep. You are going to hear a click when you cut through the tendon.” The central tendon is cut between the forceps and sclera through the intact conjunctiva, with the central third of the tendon more relaxed, and the two muscle poles left intact, maintaining the normally broad insertion.
“The nice thing is this is repeatable, either at the time of surgery, or if the diplopia should recur,” Dr Strube said. “The patient will tell you if they have improved or not at the time of the procedure if you are performing awake in the office. A procedure like this opens up treatment options for patients without using valuable OR time.”
Another minimally invasive strabismus procedure is the central plication, a rectus muscle tightening procedure. Technically, the procedure involves a modified swan incision over the muscle, Dr Strube noted, citing another study by Dr Wright and Dr Rebecca S. Leenheer, a pediatric ophthalmologist with Family Eye Care and Children’s Eye Center of New Mexico in Albuquerque, New Mexico.2
Results of the retrospective study, which categorised patients by hyperdeviations, esodeviations and exodeviations, showed that all patients experienced a decrease in strabismus following the plication procedure. In addition, diplopia was noted in 50% of the adults preoperatively and none postoperatively.
“It corrects more than the tenotomy, about 6 to 8 prism dioptres per muscle,” Dr Strube explained. “Again, this is a procedure you can do under topical anaesthesia. It is a vessel-sparing procedure, and it can be reversed if needed by cutting the sutures in the first day or two. It is really great for small angle deviations. It is hard to do a recession or resection to correct such a small amount (of deviation).”
“On average, you get about 5 to 6 prism [dioptres] per muscle,” Dr Strube noted. “You can correct about 8 prism dioptres if you are performing against a previously recessed antagonist muscle.”
Dr Strube noted that it is important to remember that pulling on the muscle is very painful for the patient and that with minimally invasive strabismus surgery, topical anaesthetic will not completely address that problem. Careful tissue handling and proper technique can avoid pain, for example, by using a traction suture to manipulate the eye rather than pulling on the muscle.
“The central plication is an invaluable technique that is great for patients [post-LASIK and post-cataract surgery] with small-angle strabismus who are keen to be out of glasses, and [it is] an additional technique for complex strabismus patients,” Dr Strube concluded. “Both the central plication and central tenotomy procedures eliminate the need for adjustable strabismus surgery, as these simple techniques can be performed as needed as a touch-up surgery to correct residual small angle deviations.”