The overall goal of this procedure is to prepare Demas endothelial tissue for DMEC insertion. This is accomplished by first performing a partial trephination and applying stain in order to visualize it. Next, a 360 degree partial dissection at the TATed line is performed between the S stroma and demas membrane.
Then the Demas membrane is manually peeled from the stromal bed, leaving only a small hinge attached. Finally, the Demas membrane is returned to the stromal bed and any residual liquid between them is removed. Ultimately, Demas membrane endothelial ker plasty using precut tissue preparations is a safe and repeatable form of controlled manual tissue dissection used to treat endothelial disease.
The main advantage of the eye bank preparing the decimated membrane endothelial ker plasty donor tissue is that it reduces the risk of tissue loss in the preparation and improves efficiency in the operating room for the surgeon. Generally, surgeons in each of this technique may struggle at first because they may find it difficult to avoid tearing Demas membrane, especially during the partial dissection and the desme stripping Visual demonstration of this technique is critical because the separation steps are difficult to describe. In particular, the successful delineation between deses and stroma Demonstrating the procedure will be Lauren Johnson, the manager of tissue processing from the Midwest Ibis, Michigan laboratory.
To begin preparing Demas endothelial tissue, dawn the proper attire including a cap and mask, and wear eye protection in the processing room. Prepare the processing room by first turning on the fan to create positive pressure. Organize all the supplies, making sure to check the expiration dates, integrity of packages and sterilization indicators with freshly washed hands, and while wearing sterile gloves, establish a sterile field by aseptically opening the wraps.
Avoid using the outer one and a half inches of the wrap as part of the sterile field as this portion is considered unsterile, drop the sterile items onto the sterile field. Next, place the microscope above the sterile field. Turn on the light source and adjust the oculars as necessary while obtaining corneal tissue to be stripped.
Place it next to the prepared sterile processing area. Loosen the cap of the viewing chamber and it to rest on top of the viewing chamber with no threads engaged and discard the non-sterile gloves. Next open, one pair of sterile gloves and a sterile gown with towel.
Perform a surgical scrub before putting on the sterile gown and then sterile gloves. Open the instrument boxes so that all supplies are accessible and open a moisture imp permeable drape to create the work area. Assemble the glass syringe for the trian loose stain by placing the plunger into the syringe and finger tightening the plunger.
Attach one cannula to the trian blue syringe and a second cannula to the bottle of balanced salt solution. Separate the TR refine punch from the vacuum block and set it aside. Then center the vacuum block within the field of view of the microscope before adjusting the microscope settings to bring the vacuum block into focus.
Using a foil square as a barrier, lift the lid of the viewing chamber with the opposite hand and using forceps. Grasp the cornea by the sclera rim to remove the cornea from the storage media. Then replace the lid of the viewing chamber, completely depressed a suction syringe.
Then place the cornea epithelial side down on the vacuum block and ensure that it is centered. Using the guideposts, gently lower the seating ring on the vacuum block. Remove the seating ring and set it aside with the tissue focused and well visualized under the microscope.
Perform a partial trephination to score through the demas membrane. Tilt the vacuum block and use a sterile swab spear placed at the limbus to remove excess medium. Next, place enough stain at the limbus to stain the edge of the score.
Demas membrane allow the stain to remain on the endothelium for 60 to 90 seconds. Then use the surgical spears to remove excess stain from the limbal area of the cornea. Taking care not to touch the endothelium with several drops of BSS.
Rinse the cornea of staining solution and use sterile swab spears to remove excess BSS. Then place one to two drops of BSS on the sclera rim to prevent the tissue from drying. Repeat as necessary throughout the procedure to perform a partial dissection of desme membrane with open forceps, place one tip at the edge of the score mark and gently separate desme membrane and endothelium away from the stroma.
Separate descemet's membrane and endothelium, not more than one to two millimeters from the scored edge, and continue the dissection 360 degrees around. Note the location of any micro tears by using a skin marker to place a dot on the vacuum block. Use forceps to remove any endothelial tags that overlap the score mark.
Then locate the previously marked micro tears and rotate the vacuum block so that the largest is at six o'clock. This will become the hinge of the flap. Next, using the forceps, grasp that SMAs membrane at 12 o'clock.
Then gently separated from the S stroma by peeling it towards the hinge. Create the hinge by stopping the separation two millimeters from the score mark. Gently lay the flap back in place on the S stroma.
Use BSS and swab spears to unscr the endothelium and return it to its original position. Remove residual fluid from between the demas membrane and the stroma so that the flap stays in position. Soak up any excess moisture from the sclera near the hinge.
Use a skin marker to draw an arrowhead on the sclera rim, pointing it to the center of the hinge and remove any excess ink. Release the vacuum by depressing the piston of the syringe connected to the vacuum block while the vacuum is disengaged. Use forceps to remove the cornea from the vacuum block using a foil square as a barrier.
Lift the lid of the viewing chamber. Place the cornea in the viewing chamber endothelial side up. Replace the lid and tighten it.
Finally, after removing tissue from the processing area and breaking down the sterile field according to the text protocol, perform post cut slit lamp evaluation and specular microscopy of the corneas and record the findings. 50 donor corneas with a mean age of 65 plus or minus six years death to processing time of 5.9 plus or minus 2.3 days, and endothelial cell density or ECD of 2, 616 plus or minus 321 cells per square centimeters were used to assess feasibility and reproducibility of the surgical preparation technique. The success rate was 72%in the first 25 cases and increase to 80%in the second half with an overall success rate of 76%Point by serial correlation or RPB was used to determine correlation with preoperative tissue factors.
The donor age, death to processing time and ECD did not correlate with successful preparation of tissue. The post preparation ECD of 2, 676 plus or minus 284 was not significantly different from the pre-preparation.ECD. Unsuccessful outcomes resulted from DM tears and severe cell loss.
These cases were also associated with difficulty re mounting tissue and incomplete staining of the dm Edge iBank. Assessment of patient outcomes from nine DEC procedures carried out by five surgeons indicated that one case had a dislocation at one day and one week without need for bubbling visual acuity at one day ranged from 2, 400 to light perception and by one week improve to 2, 103. Once mastered, this procedure can be performed in as little as 20 minutes, and with practice, the time tissue remains out of the original medium can be as short as 10 minutes.
While attempting this procedure, it's important to obtain corneal tissue from donors above the age of 45. That minimizes the risk of tearing bee's membrane. Following this procedure, additional processing can be performed such as the application of orientation markings, which identify which side is the stromal side of the membrane After its development.
This technique has paved the way for rapid acceptance of DMEC by corneal surgeons.
