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PDEK can be combined with glued IOL technique

The combination manages corneal endothelial dysfunction and secondary IOL fixation simultaneously.

Issue: April 10, 2015

ByAmar Agarwal, MS, FRCS, FRCOphth

ByPriya Narang, MS

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Globally, bilateral corneal blindness is estimated to affect 4.9 million individuals and unilateral corneal blindness affects 23 million individuals. A subset of corneal blindness is secondary to endothelial decompensation.

A combination of a corneal transplantation procedure with a glued posterior chamber IOL with an intrascleral pocket haptic fixation attempts to correct a cloudy cornea and pseudophakic requirements for optimal visual rehabilitation of the patient. Corneal clarity in cases of endothelial decompensation is usually achieved by endothelial keratoplasty, which includes Descemet’s stripping endothelial keratoplasty with donor corneal stroma and Descemet’s membrane endothelial keratoplasty without corneal stroma. In between these two is a newer procedure, pre-Descemet’s endothelial keratoplasty, which includes less stroma than with DSEK. The PDEK donor corneal disc is sturdier than the DMEK donor disc, and tissue handling may be relatively easier with PDEK. However, the donor disc preparation is different in PDEK compared with DMEK.

With regard to a secondary posterior chamber IOL or an IOL exchange, the popular techniques include haptic scleral fixation, sulcus placement, iris fixation or placement in the anterior chamber angle. Added to this list is the glued intrascleral haptic fixation of a secondary posterior chamber IOL. The choice depends on the anterior segment tissue anatomy and the surgeon’s comfort in performing such a procedure.

In this column, Drs. Agarwal and Narang describe their technique of performing a combined PDEK and glued posterior chamber IOL.

Thomas “TJ” John, MD
OSN Surgical Maneuvers Editor

Amar Agarwal

Priya Narang

Pre-Descemet’s endothelial keratoplasty is the latest iteration for endothelial keratoplasty and evolved following the description of the pre-Descemet’s layer (PDL, or Dua’s layer) by Harminder Dua. This technique allows the separation and usage of PDL, which is an additional 10 µm layer to the conventional Descemet’s membrane endothelium graft. The key to success of donor graft creation lies in the formation of a type 1 bubble that is a central, well-circumscribed, dome-shaped bubble and typically spreads from the center to the periphery of the donor lenticule. The glued IOL technique is a well-established form of intrascleral haptic fixation for secondary IOL procedures. The combination of PDEK with a glued IOL serves the purpose of handling corneal endothelial dysfunction and secondary IOL fixation simultaneously. Complicated cataract surgeries associated with posterior capsule rupture often lead to corneal decompensation that results from a failure of the corneal endothelium to maintain deturgescence. Glued IOLs have previously been used in multiple situations, including surgical aphakia, traumatic phacocele and dislocated IOL in the bag, and in combination with femtosecond laser-assisted keratoplasty.

Surgical considerations for combined procedure

The main advantage of combining PDEK and glued IOL surgery is patient convenience. Patients undergo only one surgery, attend fewer appointments and deal with only one set of postoperative medications.

Although a combined surgical procedure is not significantly more complex than PDEK surgery alone, a few concerns must be addressed, especially for novice surgeons. During the surgery, the surgeon must be prepared for a decreased view secondary to guttata or cloudy cornea, decreased anterior chamber stability (in cases requiring explantation of a previous IOL), increased chances of graft dislocation (intraoperative miosis is often required), increased intraocular inflammation that may lead to increased endothelial cell damage, and a potential risk of problems associated with the anterior chamber air fill due to possible air diversion posteriorly into the vitreous cavity.

Surgical technique

The initial step of the technique involves successful harvesting of the donor lenticule, followed by the glued IOL procedure (minus the application of glue to seal the scleral flaps), and then recipient bed preparation and donor lenticule insertion. Fibrin glue is then applied to seal the scleral flaps.

Figure 1. Pseudophakic bullous keratopathy with the presence of an anterior chamber IOL.

Figure 2. Formation of a type 1 bubble. A 30-gauge needle is introduced from the corneoscleral rim, and air is injected. A well-circumscribed dome-shaped bubble is formed and extends from the center to the periphery.

Figure 3. The edge of the bubble is perforated.

Figure 4. Trypan blue is injected into the bubble to stain the graft.

Images: Agarwal A, Narang P

Figure 5. The graft is excised with corneoscleral scissors all around the peripheral edge of the bubble, and it is then kept in the storage media.

Figure 6. Scleral tunnel incision is framed, and anterior chamber IOL is explanted.

Figure 7. Glued IOL surgery is performed, and haptics are externalized.

Figure 8. Descemetorrhexis is performed.

Figure 9. The donor graft is loaded into the cartridge of a foldable IOL. The spring of the injector is removed to prevent any damage to the graft.

Figure 10. The graft is injected into the anterior chamber and subsequently unrolled with air and fluidics.

Figure 11. Scleral flaps created for glued IOL surgery are sealed with fibrin glue.

Step 1. Donor graft preparation: The detailed method of donor graft preparation has been previously described. In brief, an air-filled 5 mL syringe with an attached 30-gauge needle is introduced from the corneoscleral disc with the needle bevel-up to the center of the donor lenticule with the endothelial side up. As air is injected, a type 1 bubble is formed with a distinct edge all around. A trephine with a suitable diameter is used to create a mark on the endothelium. The edge of the bubble at the extreme periphery is perforated, followed by injection of trypan blue into the bubble to stain the graft, which is then cut all around the trephine mark with corneoscleral scissors. The graft is then stored in the storage media.

Step 2. Glued IOL technique: The technique consists of making two partial scleral thickness flaps approximately 2.5 mm by 2.5 mm in size and 180° opposite to each other. The epithelium of the recipient eye is often debrided due to epithelial decompensation that hinders the intraoperative view. An anterior chamber maintainer is introduced in the lower quadrant, and a sclerotomy wound is created with a 20-gauge needle approximately 1 mm away from the limbus, beneath the scleral flaps. The entire glued IOL surgery is performed before tucking the haptics into the scleral pockets. An anterior chamber maintainer is used throughout the surgery, and the use of viscoelastic is deferred because it is important not to leave residual viscoelastic in the anterior chamber because it is thought to potentially hamper good adhesion between the donor corneal disc and the recipient corneal stroma.

Step 3. Recipient cornea: The recipient cornea is marked with a trephine to outline the area of Descemet’s membrane to be excised. A reverse Sinskey hook is introduced into the anterior chamber, and descemetorrhexis is performed corresponding to the margins of the epithelial mark. The Descemet’s membrane is then stripped off and removed from the anterior chamber. The donor pre-Descemet’s roll is loaded into the cartridge of a foldable IOL injector, and the injector spring is removed (as originally improvised by Francis W. Price Jr., MD) to prevent any damage to the donor graft. The donor roll is injected into the anterior chamber, and the graft is slowly unfolded with air and fluidics, avoiding any direct contact with the graft to minimize trauma. The PDEK graft rolls like a DMEK graft with the endothelium on the outer side, although due to the splinting effect of the PDL, the rolling of tissue graft is comparatively less. After proper orientation of the graft, air is injected beneath it to facilitate proper adhesion to the posterior corneal stroma. About 30 minutes is allowed to pass to facilitate initial donor-recipient corneal disc adherence. Postoperatively, the patient is asked to lay flat in the recovery room for about an hour and then to lay flat for the most of the first postoperative day.

After surgery, all patients undergo pressure patching and supine positioning overnight. Beginning the next morning, 0.1% dexamethasone sodium phosphate and moxifloxacin eye drops are administered every 2 hours for 1 week and then every 4 hours for the next 3 weeks. Topical steroid drops are then tapered to three times daily in the second month, twice daily in the third month and once daily from the fourth month onward.

Refractive concern

Performing IOL implantation before a corneal procedure involves refractive instability and unpredictable keratometry values; therefore, predicting the lens implant power before a corneal procedure can present challenges. Studies of lens power calculations associated with keratoplasty have shown that an effective way to reduce postoperative ametropia is to perform keratoplasty first, followed by lens extraction and IOL implantation at a later date. Flowers and colleagues reported 95% of patients within 2 D of intended postoperative target refraction after penetrating keratoplasty and cataract extraction, with IOL placement performed secondarily.