This retrospective case series compared the results of deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) in eyes with keratoconus, scars after infectious keratitis, stromal dystrophies and trauma. The authors report in the February issue of Ophthalmology that long-term, model-predicted graft survival and endothelial densities are dramatically greater after DALK than after PK. The DALK big-bubble technique appears to provide better results than DALK manual dissection and PK. Compared with PK, manual dissection provides higher survival of both the corneal endothelium and graft but lower visual acuity.
The study included 142 consecutive patients who underwent DALK with either the big-bubble technique or manual lamellar dissection using a slitlamp. A control group of 142 PK patients was matched for preoperative diagnosis and recipient rejection status.
They found that the average five-year postoperative endothelial cell loss was significantly less in the DALK group compared with the PK group (-22.3 percent vs. -50.1 percent; P < 0.0001). The early- and late-phase annual rates of endothelial cell loss were also significantly different (P < 0.001; biphasic linear model), at -8.3 percent and -3.9 percent per year, respectively, in the DALK group and -15.2 percent and -7.8 percent per year in the PK group. Model-calculated long-term endothelial cell loss indicated a decrease by 50 percent every 10 years after PK and every 29 years after DALK.
The median predicted graft survival was significantly greater in the DALK group, 49 years, compared with 17.3 years in the PK group (P < 0.0001). The authors say this implies that a young patient undergoing DALK should not require regrafting in the long term. Conversely, regrafting is likely to be required in the long term for a young patient undergoing PK. However, they caution that these median predicted graft survival times are statistical theorems, and clinical assessment cannot be provided because DALK has not been used for such a long period. The dramatic improvement in long-term model-predicted graft survival after DALK is explained by better survival of the corneal endothelium, as reported by several other studies, and a decrease in the incidence of rejection.
The average visual acuity was lower in the manual dissection subgroup compared with the PK group (average difference, 1.0 to 1.8 lines) and with the big-bubble subgroup (average difference, 2.2 to 2.5 lines).
The average central corneal thickness at 12 months was 536 µm in the PK group, 523 µm in the big-bubble subgroup and 562 µm in the manual dissection subgroup (P < 0.001). The average thickness of the residual recipient stroma measured by OCT was 87± 26 µm in the manual dissection subgroup. No correlation was found between this figure and logMAR visual acuity at any postoperative time point (P > 0.05).
The authors say that in order to obtain the best visual recovery, PK should be performed. However, if the main goal is the highest probability of long-term graft survival, DALK should be the preferred procedure.