11 Surgically Mastering Pre-Descemet Endothelial Keratoplasty in 15 Steps The hallmark of any surgery is marked by its reproducibility in terms of surgical procedure and visual outcomes. Technical ease, availability of tissue donor, and the required hospital and surgical setup go a long way in the acceptance of any new surgical procedure. Among all the subtypes of endothelial keratoplasty (EK), Descemet membrane endothelial keratoplasty (DMEK) and pre-Descemet endothelial keratoplasty (PDEK) are met with the technical challenge of handling thin donor tissue and subsequently loading and unscrolling it in the eye, which can be even more unpredictable and challenging at times. Donor tissue characteristics1,2 often affect and influence the tendency of some tissues to resist unscrolling and to behave in an inconsistent manner. PDEK3,4 combines a simplified technique of stripping the endothelium and Descemet membrane (DM) with the pre-Descemet layer (PDL) from the donor cornea, which is assisted by air dissection and creation of a type 1 bubble (bb).5 PDEK allows closed chamber manipulation of the donor graft. It also successfully mitigates ocular surface complications and structural problems (including induced astigmatism and perpetually weak wounds), like other EK procedure subtypes, and also immunologic graft reactions and secondary glaucoma from prolonged topical corticosteroid use, unlike a penetrating keratoplasty (PK). This constitutes one of the most essential steps and the initial step of the surgery. The donor corneoscleral rim is obtained from the whole globe and is placed with the endothelial side up. 1. Bubble creation: A 30-gauge needle attached to an air-filled 5 mL syringe is introduced from the periphery of the corneoscleral rim of the graft up to the center. The needle is entered at a considerable depth below the DM so as to create a plane between the PDL and the residual stroma. The needle is introduced in a bevel-up position under direct supervision, and air is injected. A type 1 bubble is formed that characteristically spreads from the center to the periphery, is dome shaped, and is approximately 8 mm in diameter. 2. Staining and harvesting the graft: Staining the graft is essential for enhancing the visualization of the graft and to identify the correct orientation. The edge of the bb is entered with a side port blade, and trypan blue is injected inside to stain the graft. The graft is then cut with the corneoscleral scissors all around the periphery of the bb and is placed in the storage media (► Fig. 11.1). Fig. 11.1 Donor graft preparation. (a) A 5mL air-filled syringe attached to a 30-gauge needle is introduced from the corneoscleral edge with the endothelial side up. (b) Air is being injected slowly and small bubbles start to form. (c) Air is injected and a type 1 bubble (bb) is formed. (d) The peripheral edge of the bb is ruptured with a side port blade. (e) Trypan blue is injected to stain the bubble. The edge of the bb is cut with the corneoscleral scissors. (f) The graft is placed in the storage media. This procedure can be described in 15 steps that need to be followed sequentially in the following order: • Step 1: Fix the infusion cannula. A trocar anterior chamber maintainer6 (T-ACM) (► Fig. 11.2) or even a routine anterior chamber maintainer (ACM) can also be fixed if the surgeon is not well versed with the use of a T-ACM. Fixing up an infusion setup allows the surgeon to easily switch between an air or fluid infusion as and when required during the surgical procedure. • Step 2: Switch on the air pump. Connect the T-ACM to an air pump (► Fig. 11.3). This facilitates continuous air infusion into the eye and helps to perform the procedure with an anterior chamber (AC) that is always well formed. • Step 3: Frame the side port incisions. Two side port incisions are made at superotemporal and superonasal positions (► Fig. 11.4). This is done so as to allow these sites to be used in the future for further intraocular manipulation. • Step 4: Perform descemetorhexis. Descemetorhexis is performed with a reverse Sinskey hook (► Fig. 11.5). This step is essentially the same as in a DMEK procedure. Two Sinskey hooks are introduced from both the side port incisions, and the diseased DM is peeled and scraped off the recipient bed. • Step 5: Frame the corneal incision tunnel. A 2.8 mm clear corneal incision is made, and the peeled DM–endothelium complex is removed (► Fig. 11.6). This site is further used for the introduction of the graft into the eye. • Step 6: Inferior iridectomy. Inferior iridectomy is performed with a vitrector (► Fig. 11.7). This helps to prevent any incidence of pupillary blockage. The vitrectomy machine is set at low vacuum and at the cutter rate of around 20 cuts per minute. The cutter is then placed at the proposed iridectomy site, and the iris tissue is engaged into the cutter probe initially with the aspiration mode at a low setting. A low cutting rate ensures proper aspiration of the iris tissue into the cutter followed by its cutting. The aspiration port is occluded by the iris stroma, and the iris is cut using the vitrectomy probe in a controlled manner under direct visualization, taking care not to disturb the angle structures. A customized iridectomy can thus be created in the desired quadrant, leaving the rest of the iris tissue undisturbed.
11.1 Donor Graft Preparation
11.2 Recipient Bed Preparation and Graft Insertion
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