Evaluation of functional and morphologic parameters of the cornea after epikeratophakia using prelathed, lyophilized tissue

Deep Anterior Lamellar Keratoplasty Using Dehydrated versus Standard Organ Culture-Stored Donor Corneas: Prospective Randomized Trial

PURPOSE

To compare the outcomes of deep anterior lamellar keratoplasty (DALK) using dehydrated versus standard organ culture-stored donor corneas for eyes with keratoconus.

DESIGN

Prospective, randomized, single-center trial conducted in Italy.

PARTICIPANTS

Adult patients (age ≥ 18 years) with keratoconus scheduled for elective DALK.

METHODS

Patients undergoing successful type 1 bubble pneumatic dissection using a standard DALK technique were randomized during surgery to receive either dehydrated (n = 30) or standard organ culture-stored (n = 30) donor corneas.

MAIN OUTCOME MEASURES

The primary study outcome was best spectacle-corrected visual acuity (BSCVA) 12 months after surgery. Secondary outcomes were refractive astigmatism (RA), endothelial cell density (ECD), and complication rates.

RESULTS

Postoperative BSCVA did not significantly differ between groups at both time points: mean difference at 6 months was 0.030 logarithm of the minimum angle of resolution (logMAR; 95% confidence interval [CI], -0.53 to 0.10 logMAR; P = 0.471) and at 12 months was -0.013 logMAR (95% CI, -0.10 to 0.08 logMAR; P = 0.764). No significant differences between groups were observed in terms of postoperative RA and ECD at all time points. In the first 3 days after DALK, an epithelial defect was present in 10 patients (33%) in the organ culture cornea group and in 29 patients (97%) in the dehydrated cornea group. Complete re-epithelialization was achieved by day 7 in all patients (100%) in both groups.

CONCLUSIONS

The study provides evidence that the use of dehydrated corneas is noninferior to the use of standard organ culture donor corneas for DALK. Corneal tissue dehydration represents a viable solution that can allow long-term cornea preservation and avoid wastage of unused corneas.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Increasing depth of focus with allogeneic presbyopic inlays: 3-year results

PURPOSE

To demonstrate the safety and efficacy of allogenic corneal inlays designed to increase the depth of focus (DoF) in treated eyes.

SETTINGS

Medipol University Hospital, Istanbul, Turkey.

DESIGN

Prospective case series.

METHODS

This study includes 50 eyes of 25 patients with a follow-up of 3 years. Emmetropic patients with presbyopia had implantation of allogenic corneal inlays in the nondominant eye. The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and uncorrected near visual acuity (UNVA) were evaluated in all eyes. A subjective visual acuity test system (Multifocal Lens Analyzer 3.0 application) was used to analyze the DoF by measuring the defocus curves.

RESULTS

No significant difference between the treated and fellow eyes in UDVA and CDVA was found, whereas UNVA was significantly better in the treated eyes ( P = .20, P = .07, P < .01, respectively). Comparing to the preoperative CDVA, there was a 1-line decrease in CDVA in 6 (%24) patients. The mean defocus curves reveal a DoF of 1.1 diopters (D) for the untreated eye at the logMAR = 0.2 threshold. By contrast, the mean DoF of the treated eye and binocularly was 2.8 D. The areas under the curve were significantly better in the near, intermediate, and total distances in the treated eyes, whereas it was better for the far distances in the untreated eyes. All values were significant ( P = .023 total, P < .01 others).

CONCLUSIONS

Allogenic presbyopic inlay implantation may be safe and provided a clinically and statistically significant increase in the DoF leading to good far, intermediate, and near-visual acuity in emmetropic presbyopic patients.

Sterile Excimer Laser Shaped Allograft Corneal Inlay for Hyperopia: One-year Clinical Results in 28 Eyes

Purpose: This study aimed to evaluate the one-year clinical results of an allograft corneal inlay (ACI) implantation in a case series of 28 hyperopic eyes of 16 patients.Methods: Patients with manifest refraction spherical equivalent (MRSE) between +1.00 and +6.00 D and having a cylindrical refraction of less than 1 D were included in this prospective study. The refractive powers of excimer laser-shaped ACIs were determined based on the refractive error of the individual subject's eyes. After the creation of a femtosecond flap, the inlays were centered on the pupillary axis. Visual acuities, refractive results, and other clinical findings were reported for the 6- and 12-month follow-up exams.Results: The mean age of the patients included in the study was 36.2 ± 12.4 years (range 22-65 years). The mean pre-operative MSRE of 3.6 ± 1.51 D decreased to 0.21 ± 0.56 D (P < .001). The uncorrected distance and near visual acuity increased from 0.33 ± 0.22 and 0.17 ± 0.13 to 0.75 ± 0.22 (P < .001) and 0.72 ± 0.19 (P < .001), respectively. The corrected distance visual acuity remained unchanged (pre-OP: 0.79 ± 0.22; post-OP: 0.80 ± 0.21; P = .916), and the corrected near visual acuity increased from 0.78 ± 0.22 to 0.84 ± 0.20 (P = .003). The mean K-value and central corneal thickness increased from 42.57 ± 0.81 D and 557.5 ± 43.0 µm to 44.8 ± 1.4 D (P < .001) and 597.1 ± 58.1 µm (P < .001), respectively. No significant postoperative complications such as diffuse lamellar keratitis, epithelial ingrowth, or decentralization were observed.Conclusion: Excimer laser-shaped ACI offers an alternative treatment modality for patients with hyperopia. Acceptable visual results and similar regression rates were observed with ACI implantation compared with other laser refractive procedures.

Objective Monitoring of Corneal Backward Light Scattering After Femtosecond Laser-assisted LASIK

PURPOSE

To investigate the changes in corneal backward light scattering, as measured by a rotating Scheimpflug camera with automated corneal densitometry software, in eyes treated with femtosecond laser-assisted LASIK (FS-LASIK).

METHODS

The cornea was examined preoperatively and postoperatively at 1 day, 1 week, and 1, 3, and 6 months in 23 patients who underwent myopic FS-LASIK. Local analysis of corneal backscatter was performed on four concentric radial zones across a 12-mm diameter (0 to 2, 2 to 6, 6 to 10, and 10 to 12 mm) and at a different corneal depth (anterior 120 µm, central and posterior 60 µm).

RESULTS

A statistically significant increase in corneal backward light scattering (P < .0001) was detected within the central 10 mm of the anterior cornea. The increase in corneal densitometry was gradually reversed over 6 months. The difference compared to preoperative values was no longer statistically significant at 3 and 6 months after surgery in the central cornea, whereas it remained significant in the mid-peripheral annulus (ranging from 6 to 10 mm), where the flap edge was located.

CONCLUSIONS

FS-LASIK is followed by an increase in corneal backward light scattering during the early postoperative period that returns to baseline by 3 months. Whereas the increase in corneal densitometry at the flap edge location can be related to a scarring reaction, the explanation for such an increase in the central anterior cornea remains speculative.

Deep anterior lamellar transplant using lyophilized and Optisol corneas in patients with keratoconus

PURPOSE

Prospective randomized clinical trial to evaluate the efficacy of lyophilized corneas for deep anterior lamellar keratoplasty (DALK) in patients with keratoconus.

METHODS

Ten eyes underwent DALK and received corneas that had been lyophilized, and 10 eyes received corneas kept in Optisol. Follow-up examinations included measurement of visual acuity (VA; Early Treatment Diabetic Retiropathy Study chart), topography, pachymetry, specular microscopy, contrast sensitivity, and confocal microscopy.

RESULTS

All variables improved similarly in both groups, without statistical differences between them, except for the uncorrected VA in the sixth postoperative month, which was better in the lyophilized group (0.46) compared with the Optisol group (0.70). The best spectacle-corrected VA was 0.16 in the lyophilized group and 0.26 in the Optisol group. The mean endothelial cell count during the sixth postoperative month was 2778.5 in the lyophilized group and 2611.5 in the Optisol group. Optisol corneas had greater keratocyte density, and the keratocyte density improved in lyophilized corneas during follow-up.

CONCLUSIONS

Lyophilized corneas can be used successfully for DALK to treat keratoconus with results similar to Optisol corneas.

Long-term outcome of epikeratophakia

PURPOSE

To assess the long-term outcome of epikeratophakia.

SETTING

National center for pediatric ophthalmology (The Children's Hospital) and ophthalmology department in a regional general hospital (Waterford Regional Hospital), Republic of Ireland.

METHODS

A retrospective clinical review was carried out of 25 eyes (20 patients) with epikeratophakia performed over 10 years. Eyes were assigned to a children's group (Group 1) or an adult group (Group 2), depending on patient age at the time of surgery, and assessed with respect to indication for surgery, visual acuity, condition of the implanted lenticule, complications, refraction, and corneal topography. Histological analysis was performed on 1 removed lenticule.

RESULTS

Mean follow-up of all patients was 7.3 years (median 6.8 years; range 4.0 to 10.0 years). Most eyes (n = 18) were contact lens intolerant. Freeze-dried lenticules were implanted in all cases, and all but 1 had stable visual acuity from the early postoperative period to last follow-up. In Group 1 (n = 10), most eyes had a visual acuity of 6/36 or worse preoperatively with an improvement of 1 or more lines in 4 eyes. In Group 2 (n = 14), at last follow-up most eyes retained good or improved visual acuity by 1 or more lines. Most grafts were clear or had insignificant opacities outside the visual axis. The overall complication rate was 12%, with the most serious complication being significant induced astigmatism requiring removal of 1 epigraft. Mean induced astigmatism was 2.50 diopters (D) (median 2.00 D; range 1.00 to 6.00 D), which was accurately predicted within +/- 1.00 D by corneal topography in 14 of 19 eyes. Histology demonstrated infiltration of the implanted lenticule by host keratocytes.

CONCLUSION

Epikeratophakia, a reversible procedure with a low complication rate, resulted in stable visual acuity with good lenticule condition and minimal induced regular astigmatism after long-term follow-up.

Epikeratophakia for keratoconus. Long-term results using fresh, free-hand made lamellar grafts

Epikeratophakia using fresh, free-hand made corneal grafts was done in 16 patients with keratoconus. The follow-up period averaged 27.8 months (range 13-45 months). A significant improvement of visual acuity was obtained (p = 0.002), and 14 of the 16 eyes (87.5%) achieved a corrected visual acuity greater than or equal to 6/12. The spherical equivalent and the cylindrical refractive error were reduced (p less than 0.05), and a significant flattening of the central corneal curvature was obtained (p less than 0.002). The mean postoperative central corneal astigmatism was 4.25 D. Postoperatively, the mean central corneal thickness was 0.670 mm, and the mean central thickness of the epithelialized graft was 0.336 mm. Six patients reported some postoperative glare or blurring of vision, despite a visual acuity greater than or equal to 6/9 on the Snellen chart. No significant subjective or objective changes were noticed after the 6-month postoperative follow-up visit.

Physiologic analysis of corneal healing after epikeratophakia

The evaluation of epithelial permeability, stromal transparency, and endothelial cell density is essential to determine the resumption of normal function in each corneal physiologic unit after refractive surgical procedures. The authors report the results of a prospective study conducted in 55 consecutive patients undergoing epikeratophakia using prelathed, lyophilized tissue lenses. Epithelial permeability was evaluated by means of fluorophotometry preoperatively and 1, 2, 4, 8, 12, 24, and 52 weeks after epikeratophakia. With few exceptions, Scheimpflug photography also was performed at the same examination times to assess stromal optical density. Endothelial cell counts were performed in each patient preoperatively and between 6 and 12 months postoperatively. The epithelial barrier function resumed normal values within 8 weeks after epikeratophakia. The optical density of both donor lenticule and recipient corneas was initially increased but returned to values comparable with those of unoperated corneas by 12 weeks postoperatively. Endothelial cell density was not affected by epikeratophakia. These results confirm the authors' preliminary observation that epikeratophakia allows a relatively quick recovery of normal corneal functions and should prompt investigators to demonstrate the safety of other refractive surgical procedures in a similar way.

Epikeratophakia for high myopia

A cryo-technique for production of corneal epi-lenses has been developed. During the manufacturing procedure the anterior surface of the tissue is moulded and the posterior surface cut with a microtome. After cutting, the epi-lenses are stored for days to weeks in an organ culture medium. Twelve eyes in 10 patients have been treated with epikeratophakia for high myopia (greater than -7 D). In all eyes, epithelialization was complete within one week, and at follow-up 3-18 months after the operation all epi-lenses were clear. The average refractive change in spherical equivalents was 9.7 +/- 4.4 D. All eyes obtained better uncorrected visual acuity, and no eyes lost more than one line of the best corrected visual acuity. At the time of follow-up, the patients' native cornea had regained normal hydration, whereas the epi-lenses did not thin as much as expected.