Outcomes of Same-Size Host and Donor Trephine in Deep Anterior Lamellar Keratoplasty for Keratoconus

We read the elegant randomized controlled trial by Huang and associates on the outcomes of same-size host and donor trephine in deep anterior lamellar keratoplasty for keratoconus. We have concerns about the study design, regarding masking especially.

Preoperatively A-scan was done as a routine examination. The technique of A-scan is not clearly mentioned.

Initially the authors mentioned the exclusion of 7 and 5 eyes from the same-size and oversize groups, respectively, because of failure of big bubble formation. But as the study progressed outcomes were measured taking the denominator as 45 and 47 in 2 groups, respectively. The numbers and indication of further exclusions should be clarified.

With our experience in clinics, we have noticed better uncorrected visual acuity in oversize grafts because of lesser numbers of Descemet folds as compared with same-size grafts, which is in contradiction to the study by Huang and associates.

The study mentions that at 5 years of follow up 8 of 45 and 4 of 47 eyes in, respectively, the same-size and oversize group had hyperopic spherical equivalent. But the line chart (Figure 3) does not represent any hyperopic value. This needs to be clarified, as there is no mention of exclusion of those eyes from the study.

We are also concerned about the line chart representing axial length (Figure 6); the authors have stated that after 3 years, axial length seemed to be longer than preoperatively in both the groups. But taking standard deviation into consideration, axial lengths are actually increasing after 4 years of follow-up.

We add a small mention about the incorrect spelling of axial length in Figure 6.

The authors have stated that for elevation of intraocular pressure, along with administration of topical antiglaucoma medications, steroids were terminated. But they have not mentioned about the follow-up time and whether it led to rejection of the graft (if in early postoperative period).

In the discussion column, the authors have discussed the study by Wilson and Bourne as reference 15. But in the list of references, it is actually reference 14.

In conclusion, we believe that same-size trephination for deep anterior lamellar keratoplasty in keratoconus patients would help in controlling postoperative myopic refractive error and this study is a step toward that, but more studies with larger sample sizes are necessary to prove this hypothesis.

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Jan 5, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Outcomes of Same-Size Host and Donor Trephine in Deep Anterior Lamellar Keratoplasty for Keratoconus

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