Learning Objective
· Apply principles of corneal suturing to full/near full thickness thickness corneal transplantation to both obtain proper wound closure and minimize astigmatism
Materials
· Tape to secure styrofoam heads
· Pig/goat eyes
· 25 gauge needle x 1
· 5 cc syringe x 2
· Anterior chamber cannula x 2
· Hemostat to bend needles
· Supersharp (15 degree) paracentesis blades
· Crescent blade
· Viscoelastic
· BSS (tap water will suffice)
· Fine non-locking needle holders
· 10-0 nylon suture
· Colibri or straight 0.12 or 0.3 forceps
· Vannas scissors
· Tying forceps
· Vacuum trephine
· Vacuum punch (optional for DALK)
· Left and right corneal scissors
Preparation
· Please read the following:
o Krachmer section on penetrating keratoplasty
· Please watch the following videos:
o Trephination and corneal excision in PKP (may have to create free account if don’t already have one):
§ http://eyetube.net/video/penetrating-keratoplasty-technique/
o Full surgical video on PKP (may want to mute music)
§ http://www.youtube.com/watch?v=h4FL3jtgU7s
o V sign in PKP
§ http://www.youtube.com/watch?v=zh5zYhB3yfQ
o DALK
§ http://www.youtube.com/watch?v=5hwtSeiFnV4 (using specialized air injection cannula)
§ http://www.youtube.com/watch?v=tV22aExyMlo (using bent needle)
PKP Procedure
1. Secure styrofoam head in proper orientation with tape
2. Secure eye within styrofoam eye socket
3. Inject some BSS into the anterior chamber of the pig/goat eye to reform the anterior chamber to physiologic turgor (makes for easier paracentesis incision).
4. Create a paracentesis incision
5. Fill anterior chamber with viscoelastic.
6. Trephine the cornea with the vacuum trephine to 75% depth (about 8-9 quarter turns for pig eyes).
7. Enter anterior chamber through trephined area using the paracentesis blade
8. Excise corneal button with left and right corneal scissors.
9. Resuture corneal button back in PKP fashion with 16 10-0 nylon interrupted sutures
DALK procedure (see video)
1. Secure styrofoam head in proper orientation with tape
2. Secure eye within styrofoam eye socket
3. Inject some BSS into the anterior chamber of the pig/goat eye to reform the anterior chamber to physiologic turgor (makes for easier paracentesis incision).
4. Create a paracentesis incision
5. Inject a small air bubble into the anterior chamber
6. Trephine the cornea with the vacuum trephine to ~ 80% depth (to be safe, stop at 9 quarter turns for pig eyes).
7. Using the hemostat, bend the 25 gauge needle so that it is bevel down and at about halfway across the shaft
8. With the needle on a 5 cc empty syringe with the plunger pulled to about 2.5 cc, carefully advance the needle at about 50% depth of the residual corneal stroma (what has not been trephined yet), following the curve of the cornea so as to not perforate Descemet’s membrane. Advance to the center of the cornea.
9. Inject the air into the corneal stroma. If you have a big bubble, you should see the previous small air bubble shift to the periphery of the anterior chamber. If you don’t have a big bubble, you can retry.
10. Lamellar dissect to the previous depth of trephination (try and save for resuturing)
11. Make sure the eye is soft
12. While securely holding the corneal stroma, make a single incision through the residual stroma to expose Descemet’s membrane.
13. Inject a (cohesive) viscoelastic through the stromal incision to protect DM
14. Make cruciate incisions through the stroma to expose DM (use blunt tipped corneal scissors)
15. Excise the quadrants of stromal tissue with blunt tipped corneal scissors
16. Irrigate off any viscoelastic on the DM
17. Suture on a corneal button, taking care to avoid DM perforation. If you were not able to save the previously excised corneal button, you can punch another button 0.25 mm larger and suture it on after removing DM.
18. If you perforate the DM, proceed as if doing a PKP
