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Case of the week 180 ( December 2014 )
Alternating Exotropia


16 year old girl
Vision: OD 20/20, OS 20/20
Refraction: OD plano  OS plano
Stereo: nil

This girl has had an exotropia since age 2 year, as stated by her mother. The angle in the primary position is huge, 90 prism diopters

She has had a life long exotropia . The mother would like to improve her appearance and is eager to have surgical correction for the exodeviation of her daughter.



Alternating Exotropia
Many patients with alternating exotropia are likely to have intermittent exotropia as which became decompensated with age. All of these patients have nearly equal vision in both eyes, that is because each eye is taking fixation half of the time.

Preoperative diplopia testing is extremely important in the determination of what surgical management should be done. It helps in deciding if the patient should have surgery, what surgery should be done, and when to do it. The evaluation of postoperative diplopia also helps in determining the course of action—e.g., whether to wait and reassure, manage medically with prisms, or reoperate.

 Intractable diplopia after strabismus surgery in adults without previous diplopia is very rare. The diagnostic use of prisms prior to surgery may identify some patients who have little or no risk of postoperative diplopia, as well as a group of patients with a small but definite risk of intractable postoperative diplopia.

The prism adaptation test is a pre-operative diagnostic test to identify the potential for fusion and predict the risk of diplopia in patients without the potential for binocular single vision, before embarking on cosmetic surgery.

In a patient like this with XT ( 80 PD ), the surgical plan is BLR recession 8 mm combined with one MR resection 8 mm, this works good with me.




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