Lamellar keratoplasty is a surgical procedure in which diseased corneal stroma is replaced by donor tissue. Commonly, the anterior stroma is incised with a trephine that can be set to a depth not exceeding the corneal thickness, and several stromal layers may be dissected until the desired depth of the recipient bed is obtained. Lamellar dissections, for example in lamellar keratoplasty, are generally made by removing stromal tissue 'layer for layer', while the depth of the dissection is judged by the changing tissue structure with deeper stromal beds.

Compared to a penetrating keratoplasty, a lamellar procedure has the advantage of being extra-ocular in nature in most cases; avoiding most complications associated with intra ocular or 'open sky' surgery, such as risk of damage to anterior chamber structures.

Also, there is virtually no risk of allograft rejection; larger diameter grafts can be performed safely. Post operative management is easier with less follow-up time and less usage of immunosuppressive medications .There is also less risks to eyes with pre-existing glaucoma or steroid sensitivity.

With lamellar keratoplasty, less induction of astigmatism¹ occurs and full thickness corneal grafting can still be performed if the visual result with the lamellar graft is not satisfactory.

Despite these benefits, surgeons commonly perform a penetrating keratoplasty for anterior corneal disorders, because lamellar keratoplasty is a time consuming procedure, requires more skill, and may show decreased best corrected visual acuity due to scarring at the donor-host interface.

However, in recent years, there is a renewed interest in lamellar keratoplasty due to a number of reports on deep lamellar keratoplasty (DLK). In deep lamellar keratoplasty, the objective is to remove all stromal tissue overlying the recipient overlying the recipient pupillary zone, leaving just the Descemet’s membrane and endothelium, creating the smoothest possible recipient bed. A number of techniques such as air injection^2,3,4, hydrodelamination with spatula delamination⁵ and deep stromal pocket dissection⁶ of the posterior stroma have been advocated to obtain a deep recipient stromal bed. No interface scarring was reported with DLK in these reports. However, none of the described techniques were intentionally done to expose the Descemet’s membrane during surgery.

I would like to describe my surgical technique in which the objective is to separate the Descemet’s membrane from the stromal tissue in a controlled fashion to accomplish deep lamellar keratoplasty. With this technique, the surgical time is reduced to less than an hour and graft-host interface scarring may not be a problem postoperatively. This is a technique in which I have modified from the various techniques described in the literature after performing over 40 lamellar keratoplasty in the last 4 years.

Surgical technique

A handheld corneal trephine is used to trephine the recipient cornea in a usual manner similar to a penetrating keratoplasty procedure. The recipient cornea was trephined to a depth of about 75 to 80% of stromal thickness. A paracenthesis was then made to drain out the aqueous and to make the eye soft. A 26G needle was then inserted into the stroma carefully to the level just anterior to the Descemet’s membrane by observing the appearance the of the fold lines. Once the needle bevel is fully buried within the substance of the stroma, air is injected until the Descemet’s membrane separates from the stromal tissue. This gives rise to the appearance of a large dome-shaped space expanding into the anterior chamber (Figure 1).

Sometimes, air is found entering the anterior chamber possibly via the trabecular meshwork. A 15⁰ side port blade is then used to make an opening into this stroma-Descemet’s membrane space. Immediately, air will be released and this space collapses. Viscoelastic solution is then injected through the same entry point to separate these two tissues planes. The anterior stroma is then excised with corneal scissors. Descemet’s membrane can be identified as a very smooth and glossy layer. Without the air bubble in the anterior chamber, one can hardly see this transparent layer (Figure 2).

The donor cornea is then  punched from endothelial side up. The endothelium and Descemet’s membrane is removed with forceps and cotton swab. This tissue is then sutured onto the recipient bed with 10/0 nylon sutures.

Results

I am presenting brief results only in this newsletter. This technique was tried on 17 eyes. There were 13 eyes (76.4%) in which the procedure went well without problems. Two eyes had pre-existed full thickness corneal scar and the Descemet’s membrane perforated during intra-stromal air injection. These eyes had full thickness graft performed. One eye had the Descemet’s membrane punctured even before air injection. This case was converted to another method of deep lamellar keratoplasty. In 1 eye, air was not successful in separating the Descemet’s membrane during the intra-stromal injection, while dissecting the deep stromal mechanically with a crescent knife, the Descemet’s membrane was inadvertently ruptured and this case was converted to a full thickness penetrating keratoplasty. Pathology included 13 cases of keratoconus, 2 cases of traumatic corneal scar, 1 case of post infective keratitis corneal scar and 1 case of Granular Dystrophy. The follow-up periods ranged from one month to 10 months. No interface scarring was noted in any of the cases so far.

(Figure 3) Four out of 5 eyes that had follow-up of more than 6 months achieved 6/9 or better vision. None of the 12 eyes experienced graft rejection. The eyes that had follow up longer than 6 months had all sutures removed and cessation of topical steroids. The commonest post-operative complication was the development of suture infiltrates because the topical steroids used was tailed down too fast in the earlier cases. This complication was not seen after the cause was rectified.

 In conclusion, this technique of separating the Descemet’s membrane from the stroma with air injection eases the technical difficulty in performing deep lamellar keratoplasty. This procedure shortens the operating time, has all the reported advantages of lamellar keratoplasty and possibly without the risk of having donor-host interface scarring. I am still refining the technique in order to make it an easy technique for others to learn and thus benefiting patients who would benefit more from a lamellar surgery.

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