Deep Anterior Lamellar Keratoplasty

Letters to the Editor Deep Anterior Lamellar Keratoplasty Dear Editor: Deep anterior lamellar keratoplasty (DALK) is rapidly gaining acceptance as the procedure of choice for visual rehabilitation of eyes with corneal pathology with normal corneal endothelium.1 Approximately 59% of donor corneas received by the United Kingdom Transplant Service (Bristol, UK) are issued for penetrating keratoplasty (PK).2 Of those not issued, 71% of corneas were not suitable for PK owing to endothelial insufficiency.2 It would be a major contribution if this material could be used safely for transplants in which a healthy corneal endothelium is not required. There are no previous studies reporting on the outcomes of DALK using tissue suitable for PK compared with that suitable for lamellar keratoplasty only. We reviewed 84 consecutive elective DALK procedures performed for visual rehabilitation. Donor tissue was suitable (31 cases) or unsuitable (53 cases) for PK. Indications included severe keratoconus (n ⫽ 67), microbial keratitis (n ⫽ 5), herpes zoster (n ⫽ 2), herpes simplex keratitis (n ⫽ 3), granular dystrophy (n ⫽ 1), ocular cicatricial pemphigoid (n ⫽ 1), repeat DALK (n ⫽ 2), and complications of refractive surgery (n ⫽ 3). No patients had undergone previous intraocular surgery. Primary outcome measures were best-corrected visual acuity (BCVA) and refraction closest to 12 months postoperatively. All procedures were performed by a single surgeon (WHA), using intrastromal air injection to facilitate dissection down to Descemet’s membrane. Donor tissue was not randomly allocated. Until 2004, donor material supplied by the United Kingdom Transplant Service for DALK was only suitable for PK if specifically requested or if there was surplus donor material suitable for PK. Subsequently, all donor material supplied for DALK is suitable for PK. Both groups were comparable before surgery with no statistically significant difference in age at time of surgery, gender, indication for surgery, time of follow-up, or preoperative visual acuity (Table 1; available online at http:// www.aaojournal.org). The preoperative best average BCVA was 1.02 (standard deviation [SD] ⫽ 0.66) logarithm of the minimum angle of resolution (20/209 Snellen) in cases with tissue suitable for PK and 1.20 (SD ⫽ 0.66; 20/317 Snellen) in cases with tissue unsuitable (P ⫽ 0.3). Of the 84 DALK procedures performed, complete postoperative visual and refractive data were available for 74 DALK cases (28 cases donor tissue suitable for PK and 46 cases donor tissue unsuitable for PK). Average BCVA at 12 months was 0.24 logMAR (20/35 Snellen equivalent; SD ⫽ 0.17) with tissue suitable for PK and 0.26 logMAR (20/36 Snellen equivalent; SD ⫽ 0.20) with tissue unsuitable for PK (P ⫽ 0.6; Fig 1 [available online at http://www.aaojournal.org]). Mean postoperative spherical equivalent was ⫺3.42 diopters (SD ⫽ 2.98) in those with donor tissue suitable for PK and ⫺3.52 (SD ⫽ 4.10) diopters in those with donor tissue unsuitable for PK (Table 2; available online at http://www.aaojournal.org). Mean postoperative refractive astigmatism was ⫺3.8 (SD ⫽ 2.20)

diopters in those with donor tissue suitable for PK and ⫺4.3 (SD ⫽ 2.20) diopters in those with donor tissue unsuitable for PK (Table 3; available online at http://www.aaojournal. org). There were no statistically significant differences in refractive outcomes between the 2 groups. Two patients required further visual rehabilitation and had replacement PK. In these patients, interface haze limited the visual improvement after DALK. Both had undergone DALK for severe keratoconus. Both achieved excellent BCVA after routine PK. Four DALKs failed, all occurring within 4 weeks of surgery: 2 cases required PK for double anterior chambers that did not resolve despite repeated gas injection, 2 cases developed persistent epithelial defect and graft melt within 1 month of surgery owing to atopic scleritis (Table 4; available online at http://www. aaojournal.org). These eyes underwent successful repeat DALK. Visual outcomes after DALK using donor tissue unsuitable for PK have previously been reported.3,4 However, there are no studies comparing visual and refractive outcomes using tissue suitable and unsuitable for PK. Previous studies using tissue unsuitable for PK mainly used lyophilized tissue, which requires corneal protection (such as tarsorrhapy or botulinum toxin–induced ptosis) while epithelialization takes place. This disadvantage is highlighted by a study by Coombes et al,3 in which 2 cases (of 44 DALK cases for keratoconus) had persistent epithelial defects, one of which resulted in graft melt requiring repeat corneal grafting. Sugita and Kondo4 noted that using fresh donor corneas resulted in faster visual rehabilitation, but by 3 months postoperatively, there was no difference in visual acuities between where frozen corneas had been used compared to fresh donor corneas.4 Power calculations based on our results assuming 2-sided test (␣ ⫽ 0.05; SD of the difference, 0.2; power, 90%) show 22 patients would be required per group to determine if there is a true difference in BCVA of ⱖ2 lines of the logarithm of the minimum angle of resolution (0.2) and 85 patients per group if the difference is ⱖ1 line of the logarithm of the minimum angle of resolution (0.1). Our study, although nonrandomized, suggests that the visual and refractive results for DALK using donor tissue unsuitable for PK are similar to those using tissue suitable for PK, thus potentially greatly increasing donor tissue availability. Further investigation requiring a randomized controlled trial is necessary to confirm this. If donor tissue unsuitable for PK is used, it is important to have tissue suitable for PK available if intraoperative Descemet’s perforation requires conversion to PK. ALEXANDER DAY WILLIAM AYLIFFE Croydon, United Kingdom MARTIN BLAND York, United Kingdom

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Ophthalmology Volume 115, Number 10, October 2008 References 1. Yamada M. Overcoming the technical challenges of deep lamellar keratoplasty. Br J Ophthalmol 2005;89:1548 –9. 2. Armitage WJ, Easty DL. Factors influencing the suitability of organ-cultured corneas for transplantation. Invest Ophthalmol Vis Sci 1997;38:16 –24.

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3. Coombes AG, Kirwan JF, Rostron CK. Deep lamellar keratoplasty with lyophilised tissue in the management of keratoconus. Br J Ophthalmol 2001;85:788 –91. 4. Sugita J, Kondo J. Deep lamellar keratoplasty with complete removal of pathological stroma for vision improvement. Br J Ophthalmol 1997;81:184 – 8.

Letters to the Editor Table 1. Comparison of Preoperative Data for Both Groups No.

Age at Surgery

Gender

Indication for Surgery

Donor tissue suitable for PK

31

32.9⫾11.1

21 M, 10 F

Donor tissue unsuitable for PK

53

37.1⫾17.0

41 M, 12 F

P value

—

0.2

0.3

Keratoconus: 27 (87.1%) Other: 4 (12.9) Keratoconus: 40 (75.5%) Other: 13 (24.5%) 0.2

Average Follow-up, mos (SD)

Preoperative BCVA

11.6 (3.1)

1.02 (0.57)

12.5 (2.8)

1.20 (0.66)

0.9

0.3

BCVA ⫽ best-corrected visual acuity; F ⫽ female; M ⫽ male; PK ⫽ penetrating keratoplasty; SD ⫽ standard deviation.

Figure 1. Visual outcomes by donor types.

Table 2. Visual Outcomes at 12 Months Posttransplant BCVA 0.0 logMAR BCVA 0.2 logMAR BCVA 0.3 logMAR Number of or Better or Better or Better Average logMAR BCVA Eyes (n ⴝ 74) Postoperative Number Postoperative Number Postoperative Number Postoperative (SD) Donor tissue unsuitable for PK Donor tissue suitable for PK All cases

46 28 74

7 (15%) 4 (14%) 11 (15%)

27 (59%) 17 (59%) 44 (59%)

37 (80%) 25 (86%) 62 (84%)

0.24 (0.17) 0.26 (0.20) 0.25 (0.18)

BCVA ⫽ best-corrected visual acuity; logMAR ⫽ logarithm of the minimum angle of resolution; PK ⫽ penetrating keratoplasty.

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Ophthalmology Volume 115, Number 10, October 2008 Table 3. Refractive Outcomes at 12 Months Posttransplant

All, donor suitable for PK All, donor suitable for DALK only P-value 95% confidence interval (PK – DALK) All cases

Number of Eyes (n ⴝ 74)

Average logMAR BCVA Postoperatively (SD)

Average Spherical Equivalent (SD) Diopters

Average Cylinder (SD) Diopters

28 46 — — 74

0.24 (0.17) 0.26 (0.20) 0.6 ⫺0.11 to ⫹0.06 0.25 (0.18)

⫺3.42 (2.98) ⫺3.52 (4.10) 0.9 ⫺1.67 to 1.88 ⫺3.48 (3.69)

⫺3.79 (2.22) ⫺4.26 (2.19) 0.4 ⫺0.58 to 1.54 ⫺4.08 (2.20)

BCVA ⫽ best-corrected visual acuity; DALK ⫽ deep anterior lamellar keratoplasty; logMAR ⫽ logarithm of the minimum angle of resolution; PK ⫽ penetrating keratoplasty; SD ⫽ standard deviation.

Table 4. Grafts Requiring Replacement Indication Persistent double anterior chamber Persistent epithelial defect and graft melt Interface haze limiting visual outcome

Number, Donor Tissue Originally Used 2 (1 suitable for PK, 1 suitable for DALK only) 2 (2 suitable for DALK only) 2 (1 suitable for PK, 1 suitable for DALK only)

DALK ⫽ deep anterior lamellar keratoplasty; PK ⫽ penetrating keratoplasty.

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