Scaffolding helps decrease risk for graft detachment in complex DMEK/PDEK cases

The technique can also help in routine cases during the learning curve.

Issue: June 10, 2019

ByAmar Agarwal, MS, FRCS, FRCOphth

BySoosan Jacob, MS, FRCS, DNB

One of the major problems in endothelial keratoplasty is graft detachment or dislocation. This is more common in thin membrane endothelial keratoplasties such as Descemet’s membrane endothelial keratoplasty and pre-Descemet’s endothelial keratoplasty. It especially becomes an issue in eyes that need to undergo surgeries such as secondary IOL implantation, phacoemulsification or glaucoma surgery combined with endothelial keratoplasty. It is also a problem in eyes that have more complex anterior segment abnormalities such as those with aphakia, glaucoma drainage devices or lack of a stable iris-IOL diaphragm. Various techniques employed in the past for avoiding detachment include the use of long-acting gases such as C₃F₈ or SF₆, staging surgeries into multiple sittings as well as avoiding thin membrane endothelial keratoplasty and instead performing Descemet’s stripping automated endothelial keratoplasty in complex eyes.

One of the authors (SJ) has described a technique called host Descemetic scaffolding for decreasing the incidence of graft detachment after thin membrane endothelial keratoplasty in such complex eyes. This technique is performed by creating a scaffold that holds the graft firmly up against the stroma in the postoperative period. This scaffold is obtained from native means, ie, the host’s Descemet’s membrane or the wound/incision. It is performed in combination with the air pump-assisted PDEK/DMEK technique also described by one of us (SJ).

**Figure 1.** Host Descemetic scaffolding to decrease risk for graft detachment. Shows the host Descemet’s membrane being teased out with a reverse Sinskey hook and brought to lie under the graft, thus providing the graft scaffolding from below (a). The host Descemet’s membrane is seen providing support to the graft in the quadrant. A new area for host Descemetic scaffolding is being attained in the opposite quadrant (b).

Technique

The Descemet’s membrane of the host cornea is stripped to a size that is slightly smaller than the graft size. This can be done all around or in only two quadrants that are 180° apart from each other. This is performed by an inverse descemetorhexis using the air pump-assisted PDEK/DMEK technique. Here, an air pump/pressurized air infusion is connected to an anterior chamber maintainer inserted into the anterior chamber, and subsequent maneuvers are performed under pressure of the continuous air infusion.

Once the host descemetorhexis is performed, the graft is inserted into the anterior chamber and unfolded and floated up against the recipient bed. The pressurized air infusion acts as a third hand, holding the graft firmly apposed against the recipient stroma. It also maintains the anterior chamber, preventing it from collapsing when instruments are inserted. Under pressurized air, the graft is centered and graft edges unfolded if required. Because the graft is slightly larger than the area of descemetorhexis, a part of the graft lies under the host Descemet’s membrane, overlapping it from behind.

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At this stage, leaving it as such would actually increase the risk for graft detachment. It is to prevent this overlap and subsequent increased risk for detachment that the recipient Descemet’s membrane is normally scored and removed in an area larger than the graft size in DMEK and PDEK. However, we use this oversized graft to our advantage by obtaining a scaffolding by bringing the host Descemet’s membrane posterior to the graft rather than anterior. Using a reverse Sinskey hook, the host Descemet’s membrane is teased out from a sandwiched position between the graft and the recipient stroma to come to lie beneath the graft, such that the edge of the graft is now sandwiched between the host stroma and the host Descemet’s membrane. In this way the graft receives a scaffolding or support from the host Descemet’s membrane either all around or in two quadrants opposite to each other. Because this is done using the air pump-assisted technique, damage to the graft during the maneuvers is prevented by the air holding the anterior chamber well maintained. The pressurized air also helps make graft adherence faster.

A combination of host Descemetic scaffolding and wound scaffolding can also be used in some cases. Here, the host Descemetic scaffolding, as just described, is obtained in a quadrant that is directly opposite to the wound. Scaffolding on the incisional side is obtained by pulling the edge of the graft slightly into the innermost part of the wound/incision in such a way that it does not cross more than 50% of the surface area of the wound.

Advantages

Scaffolding obtained by either of these means helps prevent graft detachment in complex situations and combined surgeries. It is also recommended for beginners in their early surgeries even in uncomplicated cases to increase their success rate. It is combined with the air pump-assisted technique that offers several other advantages such as helping perform a well-controlled inverse descemetorhexis and aiding in graft centration, graft edge unfolding, and graft unwrinkling and uncreasing. The continuous air infusion also avoids bleeding from the peripheral iridectomy, thus helping avoid a fibrinous atmosphere in the anterior chamber as well as visualization problems and blood in the graft-host interface. It helps tamponade intraocular bleeding from other sources such as while releasing peripheral anterior synechiae or oozing into the anterior chamber from peripheral neovascularization in a long-standing edematous cornea. As previously mentioned, the air pump technique also prevents anterior chamber depth fluctuations and acts as a third hand, aiding surgical maneuvers.

To conclude, the host Descemetic and wound scaffolding techniques in combination with the air pump-assisted technique help perform DMEK/PDEK successfully while also decreasing the risk for graft detachment even in complex cases and combined surgeries.

References:
Jacob S. Air pump assisted PDEK 11 advantages with audio. www.youtube.com/watch?v=lcIHrzdbDd4.
Jacob S, et al. Cornea. 2017;doi:10.1097/ICO.0000000000001225.
Jacob S. Host Descemetic scaffold for pre-Descemet and Descemet membrane endothelial keratoplasty – use of native means for graft stabilization. Presented at: American Society of Cataract and Refractive Surgery meeting; 2018; Washington.
Jacob S. Open Ophthalmol J. 2018;doi:10.2174/1874364101812010175.

For more information:
Amar Agarwal, MS, FRCS, FRCOphth, is director of Dr. Agarwal’s Eye Hospital and Eye Research Centre. Agarwal is the author of several books published by SLACK Incorporated, publisher of Ocular Surgery News, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery and Presbyopia: A Surgical Textbook. He can be reached at 19 Cathedral Road, Chennai 600 086, India; email: dragarwal@vsnl.com; website: www.dragarwal.com.

Disclosure: The authors report no relevant financial disclosures.