- 1.
How are forced ductions performed?
Before beginning surgery, place an eyelid speculum in both eyes. Using one- or two-toothed forceps, grasp the conjunctiva at the limbus. Move the eye horizontally and vertically. The resistance encountered in moving the eye is compared with what normally would be expected, as well as with the resistance encountered in performing the same forced duction on the other eye.
- 2.
Why perform forced ductions?
Forced ductions are performed to detect “tight muscles” or restrictions in eye movement. If the forced ductions indicate that a muscle is restricted, the affected muscle should be recessed. For example, if a patient has a vertical deviation, the superior rectus on the hypertropic side or the inferior rectus on the fellow eye may be recessed. If forced ductions show resistance to elevating the fellow eye, the preferred surgery is recession of the inferior rectus.
- 3.
When correcting a horizontal or vertical strabismus, how do you decide how many muscles to recess or resect?
The angle of the deviation determines the number of muscles to recess or resect. Whereas a small-angle strabismus (<20 D) may be corrected by operating on one muscle only, a large deviation may require surgery on three or four rectus muscles. Most major texts contain tables that provide a guide as to how much surgery should be performed for the angle (measured in prism diopters) of strabismus. The tables indicate how many muscles should be operated on and the amount of recession or resection.
- 4.
When doing a recess–resect procedure, should you first perform the recession or the resection?
The recession is performed first. In a resection the muscle is shortened and then brought forward to the insertion. This procedure creates tension on the resected muscle, making it difficult to bring the resected muscle to the insertion site. Initial recession of the antagonist muscle decreases the tension pulling the globe away from the resected muscle and makes it easier to bring the resected muscle to the insertion site and to tie the sutures tightly.
- 5.
When performing surgery on an oblique muscle and rectus muscle of the same eye, on which muscle do you operate first?
The oblique muscles are more difficult to identify and isolate on the muscle hook than the recti. Strabismus surgery creates swelling of the Tenon’s capsule and bleeding, which can obscure the view and make identification of the oblique muscles difficult. Therefore, it is preferable to operate on the oblique muscles first when the Tenon’s capsule and the tissues surrounding the oblique muscles are the least swollen and distorted. The recti are more easily hooked and identified. There should be no difficulty in isolating the correct rectus muscle, even in the presence of significant bleeding and swelling of the Tenon’s capsule following oblique muscle surgery.
- 6.
What type of needle is used to suture the muscle to the sclera?
A spatulated needle has cutting surfaces only on the side and is flat on the bottom. This decreases the risk of perforating the globe. The sclera is thinnest just posterior to the insertion of the rectus muscles (0.3 mm).
Chapter 3 : Parasurgical procedures and preparation”; © 2003-2014 Project Orbis International Inc. Link: http://telemedicine.orbis.org/bins/volume_page.asp?cid=1-2161-2253-2258
- 7.
What is an adjustable suture?
Various techniques of placing and tying scleral sutures allow the muscle to be moved forward or backward during the immediate postoperative period. If a patient has an immediate overcorrection or undercorrection, the muscle can be moved to improve the alignment. This suture adjustment is performed within 24 hours of the initial surgery, often in the office.
- 8.
When should an adjustable suture be used?
The use of an adjustable suture is at the discretion of the surgeon. Some surgeons do not perform adjustable suture surgery, citing the fact that the correction seen immediately after strabismus surgery is variable and may not be indicative of the long-term result. Others use adjustable sutures in cases in which the results of strabismus surgery are difficult to predict, such as reoperations and restrictive or paralytic strabismus. Adjustable sutures are often used in patients with thyroid disease.
- 9.
What is a transposition procedure?
A transposition procedure places the partial or entire tendon of the adjacent rectus muscles to the insertion of the palsied or underacting muscle. For instance, in double-elevator palsy the tendon of the lateral and medial recti may be sutured to the nasal and temporal borders of the superior rectus insertion.
- 10.
When is a transposition procedure performed?
A transposition procedure is the procedure of choice when the function of one or more rectus muscles is severely limited, as with third-nerve, sixth-nerve, or double-elevator palsy.
- 11.
How are A and V patterns of strabismus treated?
In cases of oblique muscle overaction, the appropriate oblique muscle should be weakened. Weakening of the inferior oblique muscles corrects a V pattern, whereas weakening of the superior oblique muscles corrects an A pattern ( Fig. 27-1 ). In patients with no oblique muscle dysfunction, the horizontal recti are supraplaced or infraplaced. The medial recti are displaced toward the point of the A or V pattern, whereas the lateral recti are moved in the opposite direction. A useful acronym is MALE, which stands for m edial recti to the a pex, l ateral recti to the e mpty space. For example, to treat a V-pattern esotropia without oblique muscle overaction, the medial recti are recessed and infraplaced (moved inferiorly) by half of the tendon width.
