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5 PDEK/DMEK for Failed DSAEK

5 PDEK/DMEK for Failed DSAEK

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4



Complex Scenarios in PDEK



55



a



b



c



d



Fig. 4.3 PDEK on failed PK: (a) A failed graft is seen. (b) The endoilluminator helps visualization through the hazy cornea for phacoemulsification. (c) Cortex aspiration. (d) IOL

implantation



DSAEK graft is generally easy to identify and remove. The air pump-assisted PDEK

technique helps in easier stripping of the DSAEK graft. Adherence to the overlying

corneal stroma is more at the edges of the graft than elsewhere and therefore, the continuous pressurized air helps in removing the graft without the use of viscoelastic as

well as without repeated chamber collapse. Once the DSAEK graft is removed, the

rest of the surgery may be completed as in a conventional DMEK or PDEK (Fig. 4.6).



4.6

4.6.1



PDEK in Vitrectomized Eye

Intra-operative Challenges



The vitrectomized eye offers special challenges by being soft and collapsible [2,

11, 12]. In addition, the anterior chamber is usually deeper which makes graft



56



S. Jacob



a



b



c



d



Fig. 4.4 PDEK on failed PK: (a, b) Air pump-assisted descemetorhexis done. The use of a small

separate side port to introduce the reverse Sinskey would have avoided iris prolapse. (c) The previously prepared PDEK bubble is shown. (d) E-DMEK technique is used to verify graft orientation

before insertion into the AC



unrolling difficult and the graft shows a tendency to repeatedly curl up (Fig. 4.7).

Unrolling the graft therefore can lead to increased intra-operative manipulations which can all increase the risk for endothelial cell loss and primary graft

failure. The aim should be to try and keep the AC shallow if possible, without

causing vitreous loss. This can be done by applying very gentle pressure on the

sclera. The cornea may also have to be depressed downwards in an attempt to

open up the graft. The graft may be opened partially by injecting air into the roll

(see Fig. 4.15c, d). It may be necessary to float up the graft without achieving

full unrolling of extreme graft edges and in these cases, the air pump-assisted

PDEK [2] becomes helpful in achieving unwrinkling, unfolding and centration

of the graft. However, it should be noted that even though it is possible to do air

pump-assisted techniques with DMEK, one needs to be much more careful and

gentle as the DMEK graft tears very easily as opposed to the PDEK graft which

is tough.



4



Complex Scenarios in PDEK



57



a



b



c



d



Fig. 4.5 PDEK on failed PK: (a) The PDEK graft is seen correctly oriented (scrolled upwards)

using the endoilluminator-assisted technique. (b) The graft is seen completely opened up. (c) The

air pump connected to the anterior chamber maintainer (ACM) is turned on after making sure the

ACM is under the graft. (d) Post-operative clear graft is seen



4.6.2



Broken Capsulo-zonular Barrier



If the vitrectomized eye also has a broken capsulo-zonular barrier, there is an

increased risk of vitreous entering the AC and entangling the graft, which can interfere with graft-related manoeuvres and graft adhesion. The air bubble can have an

increased tendency to migrate to the posterior chamber and the vitreous cavity

through a posterior capsular rent, thereby leading to a loss of support for the graft

both intra-and post-operatively (Fig. 4.8).



4.6.3



Importance of the Iris–IOL Diaphragm



For the above-mentioned reasons, it is imperative to have a well-formed iris–IOL

diaphragm before injecting the graft [13, 14]. This may be done by performing a

iridoplasty to make the pupil small and complete all around (Fig. 4.9a–d).



58



S. Jacob



a



b



c



d



e



f



Fig. 4.6 PDEK on failed DSAEK: (a) The edematous DSAEK graft is removed. The ACM connected

to air helps prevent chamber fluctuations while doing this. (b) A 5-year-old PDEK graft is used here. (c)

The PDEK graft is seen in correct orientation with the endoilluminator. While opening the graft, the

ACM has been turned off. (d) An air bubble is used to float up the graft and the ACM connected to the

air pump is turned on again. (e) Extreme edges generally scroll tightly in very young donors and are

difficult to unscroll completely before floatation. These extreme edge folds are opened with a reverse

Sinskey using the air pump-assisted PDEK technique. (f) A clear graft is seen (3 months post-op)



4



Complex Scenarios in PDEK



59



Fig. 4.7 In a vitrectomized eye, the AC is deep and the graft shows a tendency to repeatedly curl up



Fig. 4.8 EK in eye with posterior capsular rent: A suboptimal air bubble occurs due to migration

of air to the posterior chamber and the vitreous cavity through the posterior capsular rent. Figure

shows a sulcus-placed PCIOL with a tear in the PC (arrow)



60



S. Jacob



a



b



c



d



Fig. 4.9 The ‘bubble test’ and iridoplasty: (a) The bubble test predicts poor support to the graft.

With the ACM turned off, only a small air bubble is seen in AC on injecting air. (b, c) An iridoplasty is done to form a complete and stable iris–IOL diaphragm. (d) Post iridoplasty, a stable

bubble is seen in the AC which indicates that good support will be possible after graft floatation



A complete iris–IOL diaphragm allows good air support as well as prevents air from

migrating posteriorly in the erect position of the patient thus preventing early loss of

post-operative support (Fig. 4.10a–c). If a three-piece IOL is unstable, a closed

chamber translocation to a glued IOL may also be done (Fig. 4.11a–f). The absence

of a well-formed and stable iris–IOL diaphragm leads to greater difficulty in

unscrolling the graft and a less stable air-fill. It may also cause air to migrate into the

posterior chamber or vitreous and lead to a graft detachment in the post-operative

period. Large iris defects in an aphakic eye and in secondary scleral IOL fixations

(sutured and glued) carry the risk of the graft dropping into the vitreous. In such

cases, the iris must be attempted to be made complete all around and the pupillary

margin should ideally cover the IOL optic all around (Fig. 4.12a–f).



4.6.4



Aphakia



DMEK and PDEK both carry a high risk of graft loss into the vitreous cavity intraas well as post-operatively in aphakic eyes with absent posterior capsule. Intra- and

post-operative air management is more difficult and there is a correspondingly

higher risk for graft detachments. Aphakic eyes should therefore either undergo a

secondary IOL fixation followed by EK, or both surgeries may be performed



4



Complex Scenarios in PDEK



a



61



b



c



Fig. 4.10 Effect of complete and stable iris–IOL diaphragm in vitrectomized eye without intact

posterior capsule: (a) A stable air bubble seen in the presence of a good iris–IOL diaphragm. (b) A

large iridectomy allows air bubble to migrate posteriorly. (c) Air bubble migrates behind the IOL

in the erect position predisposing to graft detachment



simultaneously in the same sitting [15]. Simultaneous surgery has the associated

higher risk of complications secondary to operating in a less stable eye. Sequential

surgery gives more time for any large incisions to have healed and the eye may

therefore be in a more stable state at the time of PDEK.



4.6.5



Secondary IOL Fixation



Though EK has been reported with ACIOL in situ [16], it carries a higher risk of

graft damage. There is lesser operating space in the eye and more likelihood of

graft IOL touch with consequent loss of cells. This risk is especially high with

DMEK and PDEK as compared to DSAEK as graft unscrolling is more difficult



62



a



S. Jacob



b



c



d



e



f



Fig. 4.11 PDEK with closed chamber translocation of single-piece PMMA IOL into glued IOL:

(a) Single-piece PMMA IOL seen placed on iris. (b) Closed chamber translocation into glued IOL

is done very gently taking care not to crack the haptic. This maneuver is more easy if the malpositioned IOL is three-piece. (c) Iridoplasty is done to make the pupil round and smaller. (d) E-PDEK

technique clearly shows the correct orientation of the graft. (e) The graft is seen floated up. One

edge fold (arrow) is seen which is being unfolded with air pump-assisted PDEK. (f) Post-operative

clear graft is seen



and graft–IOL touch is very likely. The greater proximity of the anterior surface of

the IOL to the graft can also contribute to continuing cell loss in the post-operative

period. Iris-fixated IOL may be an option but a complete iris diaphragm is required

for this. The author’s personal preference is to combine glued IOL with PDEK. The

glued IOL gives the advantage of stable fixation of the IOL via intra-scleral haptic



4



Complex Scenarios in PDEK



63



a



b



c



d



e



f



Fig. 4.12 Air pump-assisted PDEK in partial aniridia: (a) Pre-operative picture shows a large superior

iridodialysis. However, the posterior capsule (PC) is intact and the IOL is stable. (b) Bubble test shows

a stable air fill is possible in the anterior chamber (air pump is turned off). (c) The dialysed iris is caught

by the injector and hinders graft injection. (d) Graft injection is deferred and the vitrector is used to

perform a sector iridectomy under air to remove the superior dialysed iris. This is done only because

the intact PC offers good support to the air bubble. With a broken PC, all attempts should be made to

get a complete iris-IOL diaphragm. An aniridia IOL may also be an option with large defects. The

continuous pressurized air infusion prevents bleeding from the iris and prevents fibrin formation. (e)

The PDEK graft is injected. (f) The air pump-assisted technique is used to get a well-positioned graft



64



S. Jacob



fixation and thereby less pseudophakodonesis [17]. Greater pseudophakodonesis is

a disadvantage of sutured scleral-fixated IOLs.



4.7



PDEK and the Glued IOL



Glued IOL may be performed first followed by EK or they may be performed in the

same sitting [13–15]. Care should be taken to position the glued IOL close to the

posterior surface of the iris which allows a good air fill. A larger distance between the

anterior surface of the IOL and the posterior surface of the iris can lead to an unstable air fill (Fig. 4.13). IOL tilts should similarly be avoided by keeping the sclerotomies for haptic exteriorization equidistant from the limbus on both sides. Excessive

vitrectomy should be avoided to prevent the eye from becoming too soft. Iridoplasty

should be done to cover the IOL optic from all around. Large sector iridectomies and

iridodialyses must be repaired (Fig. 4.10). An unstable single-piece IOL may be cut

and explanted followed by glued IOL (Fig. 4.14a–f). Any large wounds should be

sutured in an airtight manner and the sclerotomies should be closed with the scleral

flap using fibrin glue. The aim should be to keep the eye well formed at all times and

in case of a soft eye, BSS infusion into the AC helps to form the vitreous cavity. The

graft is then injected and the AC is kept shallow in order to unscroll the graft. The

cornea may need to be indented more than usual while unscrolling and an air bubble

may be needed to open the graft (Fig. 4.15a–f). Gentle, careful pressure on the sclera

can also help to shallow the AC slightly. The graft is then centred and floated up.

The technique of air pump-assisted PDEK may be utilized in order to make graft

manipulations easier (Fig. 4.16a–f). Air may go posterior to the iris and IOL into the

vitreous. This does not matter unless with a floppy iris, it causes pupillary block and

pushes the iris upwards in which case air must be released and AC formed again.

Care must be taken to avoid graft detachment during these manoeuvres. Long-acting

gas may be used to obtain a longer period of air support to the graft but there is a

higher risk of IOL opacification with this. Post-operative care must include strict

face up positioning to avoid air bubble migration.

a



b



Fig. 4.13 IOL position: (a) An IOL that is placed too posteriorly allows the air bubble to migrate

behind the iris. (b) A well-placed IOL without a large gap between the anterior surface of IOL and

posterior surface of iris allows good air support



4



Complex Scenarios in PDEK



4.7.1



65



Anterior Vitrectomy



If an anterior vitrectomy needs to be done, it is preferable to keep it to as minimal

as possible in order to prevent an excessively soft eye. Preservative-free triamcinolone may therefore be used to identify vitreous tags in the AC and the vitrector used

to selectively remove these tags. Vitrectomy may be done through the pars plana.

This prevents continuing prolapse of vitreous into the AC. Smaller gauge (23 or

25 G) vitrectomy systems are better and the trocar should be either removed or

plugged before injecting the graft.



a



b



c



d



e



f



Fig. 4.14 PDEK with IOL explantation with glued IOL: (a) Single-piece acrylic (SPA) IOL

placed on iris. (b, c) Scleral flaps are made for the glued IOL. The SPA IOL is then cut and

explanted. (d) A limited anterior vitrectomy is done through the sclerotomy under the

scleral flap. (e, f) The haptics of a three-piece foldable IOL are exteriorized through the

sclerotomies



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