Fornix vs. limbal incisions · Rectus Muscle Surgery Fundamentals

Incision choice is a decision, not a formality. It sets your exposure, your closure, and how miserable the next operation on this eye will be.

Choosing the approach

Limbal is the workhorse: easiest to learn, widest exposure, workable without a skilled assistant, and the only approach that lets you recess conjunctiva at closure. It costs time at both ends, needs sutures, leaves a broad perilimbal scar, and exposed knots make the first week less comfortable. Favor it over roughly 50–60 years of age, in heavy scarring, and in complex or lost-muscle cases.
Fornix is preferred in children and young adults when a trained assistant is reliably available. One incision reaches two or three muscles, six muscles need only two incisions, there are no sutures or exposed knots, the eye is examinable within hours, and scleral scarring stays minimal for any later reoperation. It needs four hands, and it is genuinely easy to get lost in.
Swan / over-the-muscle is not recommended for routine use: it bleeds, it risks blind transection of a muscle in a scarred field, and it welds conjunctiva to muscle.

Limbal peritomy — key steps

Tent conjunctiva and Tenon’s at the limbus in front of the muscle’s center and snip 2–3 mm right at the limbus. Spread into the plane between Tenon’s and sclera, not inside Tenon’s.
Turn the scissors parallel to the limbus and shave both layers off for about two clock hours either way.
Mark paired dots across the limbus at both ends of the peritomy — these are your realignment marks for closure.
Cut radial relaxing incisions between the paired marks, full thickness to bare sclera, staying in the oblique quadrants. One wing is enough for a routine horizontal case; two for verticals, reoperations and distorted anatomy.
Elevate the flap and spread bluntly back into each oblique quadrant to reach bare sclera behind the insertion, spreading away from adjacent muscles.
Close by reapposing the marked dots with two interrupted fine sutures. To recess conjunctiva instead, appose the flap edges further back along the radial cut, judging the amount with the globe rotated fully away from the incision.

Pearl: Closing a limbal peritomy is your chance to treat the conjunctiva as well as the muscle. In a long-standing large-angle or restrictive deviation the conjunctiva itself is short, and sewing it back to the limbus rebuilds the leash you have just released. Rotate the globe fully away from the incision and close so that nothing is tight in that position. The bare sclera you leave behind re-epithelializes in two to three weeks.

Two-plane fornix incision — key steps

The assistant rotates the eye away from the quadrant and lifts it forward into the fissure. Pick the avascular zone between muscles; a drop of phenylephrine beforehand blanches the superficial vessels and makes the anterior ciliary vessels easier to read.
Incise conjunctiva only, 6–8 mm behind the limbus, blades flat and parallel to the lid margin. Don’t cross the plica, don’t curve up into the fissure, don’t go back into fat.
Second plane: tent Tenon’s into a ridge parallel to the first incision and cut it perpendicular, aiming for bare sclera in one snip. Extend 5–6 mm posteriorly.
Close by massaging the conjunctiva back down and lifting the lower lid to the upper. Placed correctly the wound hides under the lid and self-seals.

Pearl: Orbital fat is the one tissue in this operation you should never see. Parks described the fornix incision in 1968 as a way to reach the muscle through a small wound that hides under the lid, and its price is that you are working closer to the fat than you are at the limbus. From about 10 mm behind the limbus, Tenon’s capsule is all that separates sclera from fat, and fat that reaches sclera or muscle scars into a restriction that is very hard to undo. Keep the conjunctival cut 6–8 mm back and the Tenon’s opening short. If fat appears, stop: don’t pull on it, don’t cauterize it, and close Tenon’s over it.

Pearl: Cut the fornix incision to size rather than letting the hook do it. A wound that is too small tears when the large hook goes in, and a tear runs where it likes — usually up into the fissure, where it shows and needs a suture. A clean cut of the right length, parallel to the lid margin, stretches around the hook and falls back under the lid when you are done.

Pitfalls to avoid

Dissecting inside Tenon’s rather than finding sclera, which turns the whole case bloody.
Dissecting toward an insertion before the muscle is hooked.
A fornix incision that wanders into the fissure or into orbital fat.
Choosing fornix without the assistant to support it.

Choosing the approach

Limbal peritomy — key steps

Two-plane fornix incision — key steps

Pitfalls to avoid

Further reading