Trends in penetrating and anterior lamellar corneal grafting techniques for keratoconus: a national registry study

PURPOSE

Keratoconus is a progressive disorder and one of the primary indications for corneal transplantation. Anterior lamellar keratoplasty offers several advantages over other techniques, including endothelial preservation and longer graft survival. In this study, we examined the recent trend of using lamellar techniques for keratoconus at a national level.

METHODS

Data were obtained from the Dutch national organ transplant database regarding corneal transplants for keratoconus performed in 2005 through 2014. Baseline characteristics for patients undergoing various techniques were obtained, and temporal trends were analysed.

RESULTS

A total of 1041 operations were performed, including 736 penetrating keratoplasties (PKPs) and 297 anterior lamellar keratoplasties (ALKs). The mean age of the total surgical group was 37.4 ± 13.4 years, and 68% of patients were male (p = 0.0001). Preoperative patient characteristics were reported in all 1041 cases. The relative proportion of ALKs increased from 2005 (19% of cases) to 2010 (39% of cases) and remained approximately 30-40% thereafter. Descemet baring or deep anterior lamellar keratoplasty (DALK) was increasingly applied and was the predominant anterior lamellar technique performed from 2009 onwards.

CONCLUSIONS

The number of corneal transplantations performed annually for keratoconus decreased during the past 10 years. Lamellar techniques were increasingly performed, accounting for approximately 35% of keratoplasties in 2010 and thereafter. Among ALK techniques, maximal depth DALK is the most prevalent keratoplasty performed for keratoconus in most recent years. Penetrating keratoplasty (PKP) is still common, with a stable frequency from 2010 onwards.

Comparison of refractive outcomes in three corneal transplantation techniques for keratoconus

BACKGROUND

Deep anterior lamellar keratoplasty (DALK) has a much lower incidence of immunologic reactions than penetrating keratoplasty (PK) for patients with keratoconus. However, it is unclear whether DALK is better on refractive outcomes than PK, due to its high postoperative myopia.

METHODS

We retrospectively studied the clinical records of keratoconus patients who underwent PK, DALK, or predescemetic DALK (pre-DALK, DALK with residual stroma) between June 2004 and September 2008. The main outcome measures included refractive sphere, manifest cylinder, corneal power, keratometric astigmatism, and best-corrected visual acuity (BCVA) at the latest visit and the methods of visual correction. Postoperative manifest refractions and topography data were compared at postoperative 3, 5, 7, and 9 years among the three groups. Additionally, the final BCVA and the methods of vision correction were compared.

RESULTS

A total of 172 subjects (172 eyes) screened out of 207 keratoconus patients underwent PK (79 eyes), DALK (68 eyes), or pre-DALK (25 eyes). Postoperative myopic refractive sphere increased in all groups, but the most obvious increase was noted in the pre-DALK group. At the 9-year follow-up, both the pre-DALK group (-6.5 ± 1.7 D) and DALK group (-6.1 ± 1.8 D) had higher myopic refractive sphere than the PK group (-5.0 ± 1.5 D, p < 0.05). Postoperative myopic manifest astigmatism progressively increased in 5 years, but there were no differences among the groups. The progressive increases in postoperative corneal power were recorded in all groups, with the highest one in the pre-DALK group and the lowest in the PK group. At the 9-year follow-up, both the pre-DALK (49.8 ± 2.7 D) and DALK (48.8 ± 2.1 D) groups had higher corneal power than the PK group (47.3 ± 2.0 D); meanwhile, the corneal power was higher in the pre-DALK group than the DALK group (p < 0.05). No differences were noted with respect to keratometric astigmatism among the groups. Mean LogMAR BCVA was 0.12 ± 0.12 in the DALK group, 0.17 ± 0.10 in the pre-DALK group, and 0.1 ± 0.11 in the PK group (p = 0.325) at 9 years after surgery. Moreover, the methods of achieving BCVA seem to be similar among the treatment groups.

CONCLUSIONS

Although DALK has a slightly higher degree of myopic refraction than PK, DALK and PK have comparable visual acuity outcomes and similar methods of vision correction. DALK is recommended for the treatment of keratoconus.

Corneal transplantation and glaucoma

Glaucoma is the leading cause of irreversible vision loss post-keratoplasty and an important cause of graft failure. With newer techniques, such as lamellar, endothelial, and laser-assisted keratoplasty as well as keratoprosthesis gaining popularity, clinicians will need to consider the incidence, risks, evaluation, and management of glaucoma for each type of keratoplasty when determining which type of transplant may be most appropriate. A comprehensive literature search of glaucoma in the setting of corneal transplantation was performed and serves as the basis for this review. Preexisting glaucoma and aphakia are notable risk factors. Patients that are candidates for deep anterior lamellar keratoplasty may benefit from reduced rates of post-keratoplasty glaucoma. Although glaucoma also complicates eyes with Descemet stripping endothelial keratoplasty, the severity is less and the intraocular pressure is more easily controlled when compared to penetrating keratoplasty. Endothelial keratoplasty creates unique perioperative issues mostly related to management of anterior chamber air bubbles.

Treatment options for advanced keratoconus: A review

Traditionally, the mainstay of treatment for advanced keratoconus (KC) has been either penetrating or deep anterior lamellar keratoplasty (PK or DALK, respectively). The success of both operations, however, has been somewhat tempered by potential difficulties and complications, both intraoperatively and postoperatively. These include suture and wound-healing problems, progression of disease in the recipient rim, allograft reaction, and persistent irregular astigmatism. Taken together, these have been the inspiration for an ongoing search for less troublesome therapeutic alternatives. These include ultraviolet crosslinking and intracorneal ring segments, both of which were originally constrained in their indication exclusively to eyes with mild to moderate disease. More recently, Bowman layer transplantation has been introduced for reversing corneal ectasia in eyes with advanced KC, re-enabling comfortable contact lens wear and permitting PK and DALK to be postponed or avoided entirely. We offer a summary of the current and emerging treatment options for advanced KC, aiming to provide the corneal specialist useful information in selecting the optimal therapy for individual patients.

Blunt scissors stromal dissection technique for deep anterior lamellar keratoplasty

Objective

We describe a modified technique for performing lamellar dissection in deep anterior lamellar keratoplasty after failure to achieve a “big bubble” detachment of Descemet’s membrane (DM) with deep intrastromal pneumatic injection.

Methods

The technique utilizes blunt lamellar dissection with blunt-tipped corneal mini scissors as an alternative to a crescent blade, which can be difficult for surgeons to master and is associated with a high risk of perforation.

Results

Other techniques of blunt dissection, such as the Melles technique, cannot be utilized after failure to achieve a big bubble, as emphysema in the stroma prevents visualization of the spatula. In contrast, our blunt scissors lamellar dissection technique takes advantage of the emphysema and microdetachments of DM created by the pneumatic injection.

Conclusion

This technique provides deep anterior lamellar keratoplasty surgeons with a simple, alternative method of baring DM or achieving a pre-DM plane with minimal residual stroma, after failure to achieve a big bubble.

A technique to salvage big-bubble deep anterior lamellar keratoplasty after inadvertent full-thickness trephination

Herein we describe a technique for management of large inadvertent full-thickness trephination during deep anterior lamellar keratoplasty using the big-bubble technique without converting to penetrating keratoplasty. First, the anterior chamber is formed with an ophthalmic viscosurgical device (OVD). Then, the full-thickness wound is secured with one X-type 10-0 nylon suture. A 27-gauge needle is attached to a 2 ml air-filled syringe and inserted into the corneal stroma in the meridian opposite to the site of full-thickness trephination. Air is gently injected to produce a limited area of "big-bubble" detaching Descemet's membrane (DM) from the corneal stroma. The "big bubble" is slowly expanded with injection of OVD. Finally, the recipient stroma is removed, the donor lenticule is placed and the DM tear is secured with one full thickness 10-0 nylon suture.