The sutures typically come with semi-circular needles that create circular paths when they are passed through tissue. There should be no linear pushing with these needles; otherwise they will bend and distort the tissues. Rather, the movement used to pass these sutures is similar to turning a screwdriver in a circular motion . Sutures should be placed symmetrically so that an even amount of tissue on either side of the incision is captured by the suture. This results in optimum holding power of the incision, better long-term stability and a lower likelihood of cheese wiring through the tissues .

The entry angle of the suture plays a large role in determining the depth of the suture. Because the needle creates a circular path, acute angles of less than 90° result in shallow passes, while obtuse angles of more than 90· result in deeper passes. If the needle entry angle is 90°, then the circular path of the needle will result in a depth equal to the radius of curvature of the needle.
Corneal Suturing Videos attachment.php?s=0585697b004bc6a6ce7c4ba80bf46b4b&attachmentid=3358&d=1509731503
The suture holding power is greatest directly under the suture itself, and this diminishes as you move farther away. The resulting forces from the suture result in a diamond-like distribution pattern (Figure 4). Shorter sutures distribute their force over a smaller area, and therefore, more sutures are required to close the incision or wound. This may be helpful in situations in which higher strength closure of the wound is required. Sutures that are placed at a more ideal length will provide good holding power at the incision while minimizing the number of sutures required for a given length of incision. Overly long sutures tend to distribute the closure force over too broad an area, and as a result, they may give less effective holding power for the incision.

Corneal Suturing, Part 1- A Curriculum for Suturing the Cornea

Leo J. Maguire, M.D., consultant in cornea and external disease, developed the curriculum in resident corneal surgery at Mayo Clinic. In this series of videos, he discusses how to engineer the placement of a suture in a corneal transplant so that the length, depth, and radiality of the sutures are consistent around the circumference of a corneal graft. Mayo has used this methodology successfully with its Ophthalmology residents for the past 15 years.

Corneal Suturing, Part 2 - Placing the Needle Into the Graft

Corneal Suturing, Part 3 - Engaging the Needle Deep in the Host

Corneal Suturing, Part 4 - Bringing the Needle to the Host Surface

Corneal Suturing, Part 5 - Suturing the Wound

Corneal Suturing, Part 6 - Integrating the Steps Into a Whole