Hisham A. Saad

Endothelial keratoplasty: the influence of insertion techniques and incision size on donor endothelial survival.

Purpose: To determine the acute endothelial cell damage from trephination and tissue insertion in endothelial keratoplasty (EK) surgery. The influence of insertion technique (forceps insertion vs “pull-through” insertion) of donor tissue and incision size (3 vs 5 mm length) was assessed. Methods: Forty precut 8.-mm-diameter donor posterior buttons were used in this study. Thirty-five buttons were inserted through a limbal incision of either 3 or 5 mm length into the anterior chamber of cadaver eyes and then removed through an open sky technique without further trauma. Five buttons that were trephined but not inserted served as a control group. Vital dye staining and computer digitized planimetry were used to analyze the tissue and quantify the total damaged area over the entire endothelial surface. Five buttons for each of 7 insertion techniques were used. The 8 tissue groups evaluated were as follows: group 1: control group of trephination only, with no insertion; group 2: forceps with folded tissue through 5-mm incision; group 3: suture pull through of nonfolded tissue through a 5-mm incision; group 4: forceps pull through of Busin glide folded tissue through a 5-mm incision; group 5: forceps with folded tissue through a 3-mm incision; group 6: suture pull through with folded tissue through a 3-mm incision; group 7: suture pull through with nonfolded tissue through a 3-mm incision; and group 8: forceps pull through of Busin glide folded tissue through a 3-mm incision. Results: The control group demonstrated 9% ± 2% peripheral cell damage from simple trephination of the tissue but without insertion. In the 5-mm incision surgeries, forceps insertion (group 2) caused 18% ± 3% loss, suture pull-through insertion (group 3) caused 18% ± 2% loss, and Busin glide pull through (group 4) caused 20% ± 5% loss. There were no significant differences in damage between any of the 5-mm incision group techniques (P > 0.99). In the 3-mm incision surgeries, forceps insertion (group 5) caused a 30% ± 3% loss, pull through with folded tissue (group 6) caused 30% ± 5% loss, pull through with nonfolded tissue (group 7) caused 56% ± 4% loss, and Busin glide pull through (group 8) caused a 28%± 5% loss. There was no difference in damage among the 3-mm groups (P > 0.96), with the exception of group 7 where pulling the unfolded tissue through a 3-mm incision was significantly worse than all other techniques (P < 0.001). There was significantly greater cell area damage in the 3-mm groups (36%) than in the 5-mm groups (19%) (P <0.001). Large patterns of striae with cell loss were seen in the 3-mm groups emanating from the peripheral traction site, regardless of whether the traction to pull the tissue through the incision and into the chamber was generated by a suture or cross-chamber forceps. Direct forceps insertion caused circular patterns of injury at the tip compression site regardless of incision size, but this damage was multiplied and exacerbated by insertion through a smaller incision. Conclusions: Smaller size (3 mm) incisions for EK surgery result in greater acute endothelial area damage than larger size (5 mm) incisions. Pull-through insertion techniques through a 5-mm incision seem equivalent in the amount of induced area damage to that of forceps insertion. Compressive injury from the incision appeared less when the tissue was folded than when not folded. Insertion with any technique through a 3-mm incision resulted in larger areas of endothelial damage. All these iatrogenic death zones outside the central endothelial area would be missed clinically by standard early specular microscopy after EK surgery.

An easy and inexpensive method for quantitative analysis of endothelial damage by using vital dye staining and Adobe Photoshop software.

Purpose: We developed a simple, practical, and inexpensive technique to analyze areas of endothelial cell loss and/or damage over the entire corneal area after vital dye staining by using a readily available, off-the-shelf, consumer software program, Adobe Photoshop. The purpose of this article is to convey a method of quantifying areas of cell loss and/or damage. Methods: Descemet-stripping automated endothelial keratoplasty corneal transplant surgery was performed by using 5 precut corneas on a human cadaver eye. Corneas were removed and stained with trypan blue and alizarin red S and subsequently photographed. Quantitative assessment of endothelial damage was performed by using Adobe Photoshop 7.0 software. Results: The average difference for cell area damage for analyses performed by 1 observer twice was 1.41%. For analyses performed by 2 observers, the average difference was 1.71%. Three masked observers were 100% successful in matching the randomized stained corneas to their randomized processed Adobe images. Conclusions: Vital dye staining of corneal endothelial cells can be combined with Adobe Photoshop software to yield a quantitative assessment of areas of acute endothelial cell loss and/or damage. This described technique holds promise for a more consistent and accurate method to evaluate the surgical trauma to the endothelial cell layer in laboratory models. This method of quantitative analysis can probably be generalized to any area of research that involves areas that are differentiated by color or contrast.

Descemet's stripping automated endothelial keratoplasty (DSAEK) using corneal donor tissue not acceptable for use in penetrating keratoplasty as a result of anterior stromal scars, pterygia, and previous corneal refractive surgical procedures.

Purpose: The purpose of this study was to evaluate outcomes of Descemets stripping automated endothelial keratoplasty (DSAEK) using anterior stromal flawed (ASF) donor corneas that were unsuitable for use in full-thickness penetrating keratoplasty as a result of stromal scars, pterygia, or previous corneal refractive surgery and to compare results with DSAEK using standard tissue. Methods: We conducted a review of our initial 42 (19 with 6-month follow up) consecutive DSAEK surgeries using ASF tissue compared with 357 (199 with 6-month follow up) time-matched controls using standard tissue. Intraoperative and perioperative complications, including dislocations and primary graft failures, were compared. Six-month best spectacle-corrected vision, incidence of rejection episodes, postoperative refractive astigmatism, keratometric values, pre- and postoperative topography-derived surface asymmetry index, and surface regularity index were compared. Results: One surgeon-cut ASF tissue was perforated before surgery and was discarded. No surgeon-cut standard tissue was perforated. No intraoperative complications and no episodes of primary graft failure or pupillary block glaucoma occurred in either group. One (2.4%) postoperative graft dislocation and one (5.2%) graft rejection episode occurred in the study group. There were 10 (2.8%) dislocations and 8 (2.2%) graft rejection in the controls. A statistically similar significant improvement in best spectacle-corrected vision occurred in both groups. Corneal topography, pachymetry, and manifest astigmatism were not significantly different between groups. Conclusion: Postoperative results of DSAEK using donor tissue excluded from use in penetrating keratoplasty as a result of stromal flaws are equivalent to results using standard donor tissue. Central corneal thickness measurements should be performed before cutting to avoid tissue perforation. The use of ASF tissue for DSAEK will expand the cornea donor pool.

Ultrathin DSAEK Tissue Prepared With a Low-Pulse Energy, High-Frequency Femtosecond Laser

Purpose: To evaluate the endothelial cell survival and stromal bed quality when creating deep stromal cuts with a low–pulse energy, high-frequency femtosecond laser to produce “ultrathin” tissue for Descemet stripping automated endothelial keratoplasty. Methods: Seventeen corneas were used for this study. Five corneas were cut with the laser at a depth of 420 to 500 &mgr;m to produce a tissue thickness of approximately ⩽70 &mgr;m. Five corneas served as an uncut comparison group. Vital dye staining and computer digitized planimetry analysis were performed on these corneas. The 7 remaining corneas were cut for scanning electron microscopy evaluation. Results: The mean central posterior stromal thickness of cut corneas was 60.6 &mgr;m (range, 43–72 &mgr;m). Endothelial cell damage in cut and comparison corneas was 3.92% ± 2.22% (range, 1.71%–6.51%) and 4.15% ± 2.64% (range, 1.21%–7.01%), respectively (P = 0.887). Low-magnification (×12) scanning electron microscopy revealed a somewhat irregular-appearing surface with concentric rings peripherally. Qualitative grading of higher magnification (×50) central images resulted in an average score of 2.56 (between smooth and rough). Conclusions: Ultrathin tissue for Descemet stripping automated endothelial keratoplasty can be safely prepared with minimal endothelial cell damage using a low–pulse energy, high-frequency femtosecond laser; however, the resulting stromal surface quality may not be optimal with this technique.

Peripheral endothelial cell damage after trephination of donor tissue.

Purpose: To evaluate and quantify the degree and pattern of donor endothelial cell damage, which occurs with mechanical trephination of donor corneal tissue. Method: Twenty donor corneal-scleral tissues were used for these paired experiments. The tissues were randomized for trephination with 10 tissues trephinated by an 8.0-mm-diameter Barron trephine (Katena, Denville, NJ), and 10 tissues trephinated with an 8.0-mm-diameter UltraFit Coronet trephine (distributed by Angiotech, British Columbia, Canada) by the same investigator. Trephinated corneal buttons were then stained with vital dye stain, and the endothelial layer image captured with digital photography. The images were then analyzed by digital planimetry, and the pattern and quantity of endothelial damage was determined by an investigator who was masked to the specific trephine used for the individual tissue. Results: Trephination created a pattern of circular damage at the edge of the donor button in every case with no break in continuity of the circle, but some portions of the circle were wider than others. Occasional, scattered, peripheral small areas also displayed damage, but no significant striae, stretch, or other central damage was noted in any donor. The mean percent damage in the series was 6.35% ± 0.90% (range: 4.33%-7.78%). The UltraFit Coronet trephinations averaged damage of 5.64% ± 0.85% (range: 4.33%-6.69%), and the Barron trephinations averaged damage of 6.50% ± 0.95% (range: 4.92%-7.78%). Although 8 of 10 experimental pairs of trephinations demonstrated less peripheral endothelial damage with the UltraFit Coronet trephine, the mean damage between each group did not reach statistical significance in this small series. (P = 0.08) Conclusions: Donor mechanical trephination of full-thickness corneal tissue creates relatively consistent amounts of peripheral edge damage and likely no central endothelial damage. There may exist differences in edge damage between different mechanical trephination systems, and a direct comparison to laser-created trephination is needed.

In Vitro Evaluation of Endothelial Cell Loss Using the Neusidl Corneal Inserter.

Purpose: To determine the immediate endothelial cell loss (ECL) resulting from insertion of a precut donor button using the Neusidl Corneal Inserter (NCI) and compare it with the previously published ECL resulting from insertion of a folded donor button using non-coapting forceps. Methods: Ten corneas were precut for Descemet stripping automated endothelial keratoplasty and trephinated to a diameter of 8.0 mm (n = 5) or 8.5 mm (n = 5). Each tissue was placed onto the platform of a new NCI spatula and inserted into a cadaveric whole globe through a 5.2 mm incision. The tissue was carefully removed and stained with trypan blue and alizarin red to detect damaged endothelium. ECL was estimated using Adobe Photoshop planimetry. Mean ECL was compared with previously reported studies of forceps insertion with a one-sample t test, using SPSS v. 19. Geographic patterns of ECL were also documented. Results: Mean ECL was 15.6% (95% confidence interval, 13.8–17.4). We were unable to detect a difference in ECL compared with previous insertion methods studied (P < 0.001). The pattern of damage from the NCI was different than that previously seen with forceps insertion. Conclusion: Immediate endothelial damage resulting from use of the NCI for insertion of Descemet stripping automated endothelial keratoplasty tissue is comparable with that seen with a standard forceps technique, but with a different damage pattern.

Immunohistochemical Expression of Fas Ligand (FasL) and Neprilysin (Neutral endopeptidase/CD10) in Keratoconus

Recent evidence demonstrated a correlation between apoptosis and neprilysin expression. The aim of this study was to investigate the immunohistochemical expression of Fas ligand (FasL) and neprilysin in keratoconic corneas in comparison to normal cadaver corneas to evaluate if such molecules play a role in the pathogenesis of keratoconus. We studied the expression of FasL and neprilysin in corneal specimens removed during penetrating keratoplasty in 15 cases with keratoconus and compared them with 5 normal cadaver corneas. In keratoconus, FasL was expressed in epithelium, endothelium and sub-Bowman’s stroma only, while neprilysin was expressed in epithelium, endothelium and all stromal layers. All normal corneas showed weak expression of both markers in basal epithelial layer only. In keratoconus, corneal epithelium with higher expression of FasL may evoke apoptosis in keratocytes, while neprilysin could prevent possible rescue of keratocytes from apoptosis.

Analysis of the Outcomes of Combined Cross-Linking with Intracorneal Ring Segment Implantation for the Treatment of Pediatric Keratoconus

ABSTRACT Purpose: To analyze the visual and refractive outcomes of combined accelerated cross-linking with femtosecond laser intracorneal ring segment implantation for the treatment of pediatric keratoconus. Materials and Methods: This retrospective multicenter noncomparative clinical study included 63 eyes of 37 patients (age, 9–17 years) who underwent between August and September 2016 combined cross-linking with intracorneal ring segment implantation for keratoconus. Preoperative and postoperative (6, 12, and 18 months) uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA), subjective refractions, keratometry (K), and pachymetry measurements were compared. Results: The postoperative spherical equivalent refraction was within ±1 D, ±2 D, and ±3 D in 19 (30.2%), 27 (42.9%), and 37 (58.8%) eyes, respectively. Only 27 eyes achieved the attempted preoperative spherical equivalent refraction. The mean spherical equivalent refraction significantly improved from −6.01 ± 2.97 to −3.13 ± 2.78 D postoperatively (P < 0.0001). The mean K average reading significantly decreased from 48.75 ± 4.25 to 46.65 ± 3.89 D postoperatively (P < 0.0001). The mean postoperative myopic, astigmatic, and spherical equivalent corrections were −2.17 ± 2.19, −1.52 ± 2.03, and −2.93 ± 2.35 D, respectively. The mean UDVA and CDVA showed significant improvements (0.89 ± 0.33 to 0.40 ± 0.28, P < 0.0001; 0.35 ± 0.31 to 0.25 ± 0.24, P = 0.004; respectively) at 18 months postoperatively. Keratoconus progression, segment migration, and segment extrusion were seen in four (6.4%), one (1.6%), and three (4.7%) eyes, respectively, probably contributing to the lower mean postoperative CDVA. Conclusion: Cross-linking plus is only partially effective for pediatric keratoconus. Despite some improvements in vision and keratometry measures, it resulted in complications such as keratoconus progression, segment extrusion, and segment migration that affected the vision in some patients. These findings suggest an assessment of standard epithelium-off collagen cross-linking as a sole procedure to treat pediatric keratoconus in future studies.

One-year results of the triple procedure for primary pterygia

Purpose The aim of this work was to study the effectiveness and potential complications of adjunctive intraoperative mitomycin-C (MMC) application combined with limbal-conjunctival autografting after primary pterygium excision. Patients and methods Fifty-seven eyes of 43 patients with primary pterygia were randomized to receive pterygium excision, followed by either a free conjunctival autograft (control group, n = 27) or an adjunctive intraoperative MMC 0.02% application for 2 min and limbal-conjunctival autograft (triple procedure group, n = 30). All patients were followed for 12 months. Results After 1 year, the recurrence rate was 14.81 and 0% in the control and the triple procedure groups, respectively (P < 0.05). Most complications were transient and mild. The duration of surgery was significantly shorter in the control group (P < 0.01). The surgery did not significantly alter the corrected distance visual acuity or the average absolute astigmatism in either group. Conclusion Simple excision of pterygium combined with adjunctive intraoperative MMC 0.02% application for 2 min and limbal-conjunctival autografting is a safe and effective way of treating primary pterygia.