Anterior segment optical coherence tomography versus ultrasound pachymetry to measure corneal thickness in endothelial keratoplasty donor corneas

Intraoperative optical coherence tomography-guided donor corneal tissue assessment and preparation

Purpose

To evaluate the role of intraoperative optical coherence tomography (i-OCT) in donor grading, selection, and preparation during different types of keratoplasty.

Methods

Seventy-one consecutive donor corneas collected over 6 months, after clinical grading, were observed by an experienced corneal surgeon under an i-OCT equipped microscope. The donor preparation (manual/automated) for different types of keratoplasty procedures was also undertaken under i-OCT.

Results

The mean central corneal thickness of optical and nonoptical grade tissues was 533 ± 19 and 662 ± 52 μm, respectively. The i-OCT-based grading matched with clinical grading in 98.5% cases. Irregular thickness, anterior stromal hyperreflectivity, and previous scars were appreciated in 1.4, 1.4, and 7.04% donors, respectively. During Descemet stripping automated endothelial keratoplasty, i-OCT facilitated selection of appropriate microkeratome head for automated donor preparation in all cases, besides allowing manual dissection of partially dissected lenticule, identification of site of inadvertent perforation, and eccentric trephination in one case each. During Descemet membrane endothelial keratoplasty, i-OCT-based assessment of preexisting scar (five cases) guided careful tissue selection (2/5) and preparation. During predescemetic endothelial keratoplasty, precise needle advancement allowed successful type-1 bubble formation in all cases. All manually punched donors demonstrated an extra endothelial ledge, while those with automated preparation showed tapering donor margins.

Conclusion

i-OCT might serve as a useful imaging tool for objective assessment of donor characteristics. The modality may complement clinical evaluation for donor grading, selection, and preparation.

Measurements of donor endothelial keratoplasty lenticules prepared from fresh donated whole eyes by using ultrasound and optical coherence tomography

This study was conducted to analyze the profile and thickness of endothelial keratoplasty lenticules prepared from fresh donated whole eyes with Visante optical coherence tomography (V-OCT) compared to measurements obtained from ultrasound pachymetry (USP) at the Central Eye Bank of Iran. Microkeratome-assisted precut corneas were prepared for Descemet stripping automated endothelial keratoplasty by using standard eye bank protocol. Central posterior lenticule thickness (CPLT) on fresh whole eye, before excising corneoscleral disc and transferring to Optisol-GS, was measured by USP. V-OCT was used to measure central, paracentral, and midperipheral thicknesses of lenticules after transferring the tissue to Optisol-GS. Chi Square and Bonferroni tests were respectively used to uncover the differences between the USP and V-OCT measurements and also the thickness profile of lenticules. Postoperative reports for the entire transplanted lenticules were recorded. Accordingly, on evaluation of 312 enrolled precut corneas, CPLT measurements by V-OCT versus USP were statistically different (mean: 136 µm vs 165 µm, respectively; P = 0.008). Thickness profile of the posterior lenticules revealed increased thickness from the central to the peripheral parts of the cornea (mean increase of 16 µm at the pericentral and 64.2 µm at the peripheral locations, respectively); however, the increase in the thickness was relatively symmetrical. Postoperative reports of transplanted lenticules were unremarkable, since there were no posterior flap detachments. In essence, V-OCT measurements of microkeratome-assisted precut lenticules prepared from fresh donated whole eyes averaged 29 μm thinner than USP measurements and revealed a significant but symmetric increase of thickness towards the peripheral parts of the corneas. However, the variation in the thickness profile did not affect the attachment or the clarity of transplanted precut lenticlues.

Reproducibility of single-pass donor DSAEK tissue preparation with the MORIA single-use microkeratome

PURPOSE

To assess the reproducibility of single-pass cutting for preparation of ultra-thin (≤120μm) donor cornea grafts in Descemet stripping automated endothelial keratoplasty (DSAEK).

METHODS

All consecutive patients of DSAEK performed using the MORIA One Use microkeratome (MORIA, Antony, France) in between June 2014 and August 2015. Patient and donor central corneal thickness (CTT), microkeratome head, remaining stromal bed thickness (RSBT), number of cut and graft thickness at 1 month and 6 months postoperatively were recorded in this single-center prospective study.

RESULTS

The mean preoperative donor graft CCT was 569.0±45.1μm and the mean donor endothelial graft CCT immediately after the cut was 116.5±28.7μm. At 1 month postoperatively, the mean CCT was 102.8±35.9μm. At 6 months, the mean CCT was 89.4±26.2μm. In all eyes, the mean CCT decreased from the post-cut (116.5±28.7μm) to the last visit (89.4±26.2μm) (P<0.01) due to in vivo deturgesence of the graft. We obtained 77.5% ultra-thin DSAEK immediately after the cut, 77.5% at 1 month and 89.8% after 6 months.

CONCLUSION

Single-pass technique with the MORIA One Use microkeratome offers safe and reproducible DSAEK tissue preparation and allows achieving ultra-thin DSAEK in 89.8% of cases.

Accuracy of corneal trephination depth using the Moria single-use adjustable depth vacuum trephine system

Background

The Moria single-use adjustable depth trephine is a device that allows a goal trephination depth to be set prior to the surgical procedure.

Methods

Eleven fresh human cadaveric eyes were trephined using 8.0 mm Moria single-use adjustable vacuum trephines. Prior to trephination, the average corneal pachymetry in the peripheral 7–10 mm range was obtained using anterior segment optical coherence tomography. The trephination depth was set to 80% of that value. Light microscopy was used to image anteroposterior cross-sections of each corneal specimen. Digital protractor software was used to evaluate the trephination angle, depth, and length. All adequately processed specimens were included in the analysis. In addition, trephination angle data from a previous publication by Moshirfar et al were used as a comparison with those of this study.

Results

Trephination analysis of depth compared with pachymetry revealed a mean of 83.7%±6.53% (95% confidence interval 79.8–87.6). Maximum and minimum trephined depths were 95.35% and 71.3%, respectively. Trephination depth compared with angular corneal thickness yielded a mean of 66.2%±4.79% (95% confidence interval 63.0–69.4). Maximum and minimum depths were 73.7% and 59.7%, respectively. Analysis of trephination angle yielded a mean of 130.2±3.57 degrees (95% confidence interval 127.8–132.61). Maximum and minimum angles were 135.5 degrees and 126 degrees, respectively. The standard deviation of the trephination angle of the Moria trephine was found to be significantly less than that of Hessburg-Barron and Hanna trephines calculated in the previous study.

Conclusion

The Moria adjustable vacuum trephine is an accurate method of trephination when a specific depth is desired. Further investigation is needed to determine the relevance of this in relation to deep anterior lamellar keratoplasty.

Eye-bank preparation of endothelial tissue

PURPOSE OF REVIEW

Eye-bank preparation of endothelial tissue for keratoplasty continues to evolve. Although eye-bank personnel have become comfortable and competent at Descemet's stripping automated endothelial keratoplasty (DSAEK), tissue preparation and tissue transport, optimization of preparation methods continues. Surgeons and eye-bank personnel should be up to date on the research in the field. As surgeons transit to Descemet's membrane endothelial keratoplasty (DMEK), eye banks have risen to the challenge of preparing tissue. Eye banks are refining their DMEK preparation and transport techniques.

RECENT FINDINGS

This article covers refinements to DSAEK tissue preparation, innovations to prepare DMEK tissue, and nuances to improve donor cornea tissue quality.

SUMMARY

As eye bank-supplied corneal tissue is the main source of tissue for many corneal surgeons, it is critical to stay informed about tissue handling and preparation. Ultimately, the surgeon is responsible for the transplantation, so involvement of clinicians in eye-banking practices and advocacy for pursuing meaningful research in this area will benefit clinical patient outcomes.