Comparison of Corneal Surface Higher-Order Aberrations After Endothelial Keratoplasty, Femtosecond Laser–Assisted Keratoplasty, and Conventional Penetrating Keratoplasty

[Options for contact correction after keratoplasty]

Keratoplasty is a radical surgical method for treating various corneal pathologies. Today, there are many types of keratoplasty, each aiming to restore the integrity and transparency of the cornea. However, keratoplasty-induced ametropia often prevents achieving high visual acuity and makes impossible the use of conventional optical correction methods such as glasses or soft and traditional rigid contact lenses. In this regard, the use of scleral contact lenses is the most optimal method for optical correction of postoperative refractive anomalies, ensuring successful visual rehabilitation and preventing the need for additional keratorefractive interventions.

Suprathreshold contrast perception of resolvable high spatial frequencies remain intact in keratoconus

Contrast detection thresholds are elevated with optical quality loss in keratoconus. This study hypothesized that suprathreshold contrast perception is also impaired in keratoconus, with the impairment being predictable from the pattern of loss in threshold-level performance. Contrast detection thresholds were determined across a range of spatial frequencies in 12 cases with mild to severe keratoconus and 12 age-similar controls. These values were used to predict the contrast needed to achieve perceptual matches between reference and test spatial frequency pairs (peak of CSF Vs. 0.3x, 0.5x, 2x or 3x spatial frequency from the peak) for stimuli at 10% and 50% suprathreshold contrast. Contrast thresholds predicted a 1.5 to 6.7-fold increase in the test pattern's contrast to obtain a perceptual match with the reference pattern in keratoconus, relative to controls. Contrary to predictions, the empirical data of contrast matches between test and reference patterns were similar for higher than peak spatial frequencies at both contrast levels. However, as predicted, test patterns required higher contrast than the reference pattern for a perceptual match for lower than peak spatial frequencies. These results were similar to controls and invariant of disease severity, interocular asymmetry and short-term changes in optical quality. Unlike thresholds, suprathreshold contrast perception of resolvable high spatial frequencies appears immune to optical quality losses in keratoconus. These results are discussed in the context of the prevailing models of contrast constancy in healthy humans. Breakdown of contrast constancy at lower than peak spatial frequencies may reflect the properties of the testing paradigm employed here.

Update on Femtosecond Laser-Enabled Keratoplasty

ABSTRACT

The application of femtosecond lasers to corneal transplantation is an intriguing proposition with many potential benefits to patients with various corneal diseases. The customized trephination pattern for donor and host matching offers many advantages regarding wound integrity and high precision of donor and recipient match at the interface, which should lead to faster healing and visual rehabilitation. Femtosecond laser-enabled keratoplasty (FLEK) is an advancement of conventional trephination penetrating keratoplasty, and in large clinical cohorts to date, there are meaningful improvements in visual outcomes and a lower risk of graft rejection. Femtosecond laser-enabled deep anterior lamellar keratoplasty (Femto-DALK) combines the advantage of a customized trephination pattern with the deep anterior lamellar keratoplasty procedure, which eliminates the risk of endothelial rejection. Furthermore, the precision of the femtosecond laser may offer additional novel approaches to lamellar keratoplasties. In time, advancements in femtosecond laser platforms will help cornea surgeons realize the added benefits and better optimize outcomes for patients, such that the cost-benefit calculus shifts toward wider accessibility for patients. Prospective randomized-controlled trials are needed to definitively determine the impact of femtosecond laser-enabled keratoplasties on long-term outcomes.

Femtosecond laser deep lamellar keratoplasty

We aimed to develop a novel and effective technique for creating a smooth deep lamellar dissection of the cornea using a femtosecond (FS) laser for deep anterior lamellar keratoplasty (DALK), we conducted a retrospective eye bank study. Thirteen fresh human corneas were mounted on an artificial anterior chamber, and deep lamellar cuts were made with a 500-kHz VisuMax FS laser at a level of 50-80 μm anterior to the Descemet's membrane (DM). A posterior diameter of 8 mm with a side cut angle of 110° was used for the anterior penetrating side cut. The anterior lamellar tissue was bluntly dissected. The residual posterior stromal beds and side cuts were examined with microscopy and intraoperative optical coherence tomography (OCT) and post-cut endothelial cell evaluations. All corneas revealed a smooth residual posterior stromal bed without any visible irregularities or ridges by microscopy and OCT imaging. Six corneas were suitable for post-cut endothelial cell evaluation 2 days after laser cut, with no significant endothelial cell loss post-laser and blunt dissection of the posterior stroma. FS laser deep lamellar keratoplasty utilizing an ultrafast laser to produce a smooth deep stromal dissection followed by blunt dissection and removal of the anterior stromal tissue yields a consistent and smooth residual stromal bed. The creation of a smooth lamellar dissection in the deep posterior cornea may result in more consistent DALK without the need for air bubble or manual baring of DM that has the risk for DM perforation.

Impact of Degraded Optics on Monocular and Binocular Vision: Lessons from Recent Advances in Highly-Aberrated Eyes

PURPOSE

Optical imperfections of the eye, characterized by higher-order wavefront aberrations, are exaggerated in corneal disease (e.g., keratoconus) and iatrogeny (e.g., keratorefractive surgery for myopia correction, keratoplasty for optical clarity restoration). This article reviews the recent advances on this topic for a comprehensive understanding of how optical degradations in disease models impact retinal image quality and monocular and binocular visual performance.

METHODS

Published literature over the last decade on retinal image quality and/or monocular and binocular visual functions with corneal irregularity was reviewed based on their relevance to the current topic, study population and strength of study design. The literature was summarized into four themes: 1) wavefront errors and retinal image quality of highly aberrated eyes, 2) monocular and binocular vision loss consequent to degraded optics and visual strategies to optimize performance, 3) impact of optical correction modalities on visual performance and 4) implications for clinical management of patients.

RESULTS

Across the 46 articles reviewed, the results clearly indicated that an increase in higher-order aberrations across these conditions had a significant negative impact on the patient's retinal image quality, and monocular and binocular visual functions. Interocular differences in retinal image quality deteriorated visual performance more than an overall worsening of image quality bilaterally. Minimizing optical degradation using rigid contact lenses and adaptive optics technology significantly improves retinal image quality and monocular and binocular vision, but performance remains sub-optimal relative to age-similar healthy controls.

CONCLUSION

Corneal disease and iatrogeny are useful models to understand the impact of optical degradation on retinal image quality and visual performance. Clinical management will greatly benefit from equalizing retinal image quality of both eyes of these patients. Future studies that deepen our understanding of the structure-function relation in these conditions are desirable for advancing vision science in this area and for developing novel clinical management strategies.

Post-penetrating keratoplasty astigmatism

Postoperative astigmatism is one of the common complications affecting visual outcomes after a penetrating keratoplasty. It can result from various factors related to host, donor and surgical technique, resulting in suboptimal visual outcome. While some of the measures taken during preoperative planning and during actual surgery can reduce the magnitude of postoperative astigmatism, postoperative correction of astigmatism is often required in cases with high degrees of astigmatism. When spectacles and contact lenses fail to provide optimal visual outcomes, various surgical techniques that include astigmatic keratotomy, compression sutures, toric intraocular lens placement, and laser refractive procedures can be considered. When none of these techniques are able to achieve a desired result with in the acceptable optical range, a repeat keratoplasty is considered a last option. We discuss the various causes and management of complication of postoperative astigmatism occurring after a full thickness corneal transplantation surgery.

[Comparative assessment of functional outcomes of different endothelial keratoplasty techniques]

PURPOSE

Comparative analysis of the higher-order aberrations (HOA) of the cornea after endothelial keratoplasty (EK) using DSAEK and DMEK techniques; evaluation of the correlation between higher-order corneal aberrations and functional outcomes of the treatment.

MATERIAL AND METHODS

The study included 47 patients (59 eyes). The main group consisted of 35 patients (35 eyes) with bullous keratopathy and Fuchs' endothelial dystrophy; among them, 19 patients underwent endothelial keratoplasty using the DSAEK technique and 16 - DMEK technique. The control group included 12 patients (24 eyes) of corresponding age without corneal pathology. Standard and special examination tests were performed before, as well as 6 and 12 months after the operation, including computed tomography and aberrometry of the cornea using the Pentacam HR system. Same tests were performed in the control group.

RESULTS

The values of the main HOA of the anterior corneal surface: RMS coma (Z₃^±1, Z₅^±1), RMS spherical aberration (SA; Z₄⁰, Z₆⁰) and RMS HOA (Z_3-6) 6 months after different EK techniques were statistically significantly higher than in the control group. A statistically significantly lower induction of aberrations of the posterior corneal surface after DMEK technique was revealed. Analysis of the final aberration pattern 6 months after surgery did not reveal any statistically significant differences in the values of the main (RMS coma, RMS SA, RMS HOA) total corneal aberrations after DSAEK and DMEK. A negative correlation was revealed between the best corrected visual acuity (BCVA) and HOA; however, it was statistically significant only for individual aberration values: RMS HOA (Z_3-6) of the posterior corneal aberrations after DMEK (r= -0.634, p=0.049), and RMS coma (Z₃^±1, Z₅^±1) of the cornea after DSAEK (r= -0.57, p=0.042).

CONCLUSION

Comparative analysis of total corneal HOA did not reveal a statistically significant difference in the main parameters: RMS coma, RMS SA, RMS HOA in patients after DSAEK and DMEK surgeries. Correlation analysis did not reveal any statistically significant effects of most aberrations on the functional outcomes of the treatment.

Comparing the efficacy and safety of femtosecond laser-assisted vs conventional penetrating keratoplasty: a meta-analysis of comparative studies

PURPOSE

To investigate the safety and efficacy of femtosecond laser-assisted penetrating keratoplasty (FLAK) versus conventional penetrating keratoplasty (CPK).

METHODS

A literature search of PubMed, Cochrane, Embase, Web of Science, and Clinicaltrials.gov was conducted for comparative studies published from January 2007 to October 2019. Studies that involved both FLAK and CPK groups and reported on the relevant efficacy and/or safety parameters were included. The Newcastle-Ottawa quality assessment scale was used to analyse the methodological quality of these studies. Further, weighted mean differences (WMDs) with 95% confidence intervals (CIs) were calculated.

RESULTS

From the screened articles, a total of 1991 eyes from nine comparative studies were included. FLAK was not statistically superior for twelve-month postoperative best corrected visual acuity (WMD = - 0.06; 95% CI [- 0.16, 0.04]; P = 0.22), corneal astigmatism (WMD = - 0.81; 95% CI [- 1.63, 0.01]; P = 0.05) or six-month postoperative uncorrected visual acuity (WMD = - 0.11; 95% CI [- 0.27, 0.06]; P = 0.21). There were no significant differences in corneal graft rejection rate and the graft failure between FLAK and CPK at twelve months postoperative. However, best-corrected visual acuity (BCVA) and corneal astigmatism corrected with FLAK were better than those with CPK six months postoperative after elimination of data heterogeneity.

CONCLUSION

Visual outcomes improvement in FLAK was better than that in CPK at six months postoperative, but not twelve months postoperative. This review recommends selecting a technique based on patients' work demands and economic burdens.

Femtosecond Lasers in Cornea & Refractive Surgery

Since the introduction of femtosecond laser (FS) systems for corneal flap creation in laser-assisted in-situ keratomileusis there have been numerous applications for FS laser in corneal surgery. This manuscript details the utility of FS lasers in corneal surgical procedures including refractive laser surgeries, intracorneal ring segment tunnels, presbyopic treatments, and FS-assisted keratoplasty. We also review the role of FS lasers in diagnostic procedures such as two photon excitation fluorescence and second harmonic generation.

Femtosecond laser-assisted deep anterior lamellar keratoplasty

PURPOSE OF REVIEW

A survey of the recent literature of deep anterior lamellar keratoplasty using femtosecond laser technology.

RECENT FINDINGS

There are several recent reports in the literature assessing technique and outcomes of deep anterior lamellar keratoplasty done with a femtosecond laser trephination. Most of these reports are laboratory studies and small case series with short-term outcomes. The laser technology is expensive and may not produce better results than conventional manual techniques. However, there are several theoretical advantages to femtosecond laser incisions in deep anterior lamellar keratoplasty that should be explored, including possible increased success of Descemet's membrane separation from stroma during surgery as well as postsurgical astigmatism benefits, earlier suture removal, and increased wound strength and healing.

SUMMARY

Femtosecond laser trephination in the setting of DALK may improve the technique by decreasing the number of descemet's membrane ruptures and improving short-term and long-term outcomes as compared with manual techniques. However, there is no consensus on a standardized approach for wound design or postoperative management. The literature would benefit from a prospective randomized controlled trial.

Effect of Donor Graft Thickness on Clinical Outcomes after Descemet Stripping Automated Endothelial Keratoplasty

Purpose

To evaluate the effects of donor graft thickness on postoperative best spectacle-corrected visual acuity (BSCVA), refractive outcomes, endothelial cell density (ECD) and function, intraocular pressure (IOP), and postoperative complications after Descemet stripping automated endothelial keratoplasty (DSAEK).

Methods

This retrospective, interventional case series enrolled 77 eyes of 64 patients who underwent DSAEK with or without simultaneous cataract surgery. Clinical outcomes, including BSCVA, refraction, keratometric astigmatism, IOP, and ECD were assessed at the final follow-up examination. Univariate analyses were used to investigate the effects of postoperative donor graft thickness on clinical outcomes and complications.

Results

The mean patient age was 62.3 ± 15.6 years, and the patients were followed for 26.2 ± 20.9 months postoperatively. The mean postoperative central graft thickness was 102.4 ± 31.6 μm. In the univariate analysis, postoperative central graft thickness was significantly associated with postoperative IOP (P = 0.005), central recipient thickness (P = 0.002), and ECD (P = 0.016). No significant association was found for central graft thickness with postoperative BSCVA (P = 0.70), spherical equivalent refraction (P = 0.33), keratometric astigmatism (P = 0.27), graft detachment (P = 0.16), graft decentration (P = 0.17), high IOP (P = 0.53), or endothelial rejection (P = 0.88).

Conclusion

This study failed to demonstrate any significant correlation between graft thickness and BSCVA. Attempting to minimize graft thickness might not have the desired outcome regarding endothelial cell density and function. Increased graft thickness could negatively impact the accuracy of IOP measurements after DSAEK.

Long-Term Results of Femtosecond Laser-Enabled Keratoplasty With Zig-Zag Trephination

PURPOSE

To report long-term visual and astigmatism outcomes in cases of zig-zag femtosecond laser-enabled penetrating keratoplasty (FLEK).

METHODS

Retrospective review. Three hundred thirty-five eyes of 287 patients underwent (FLEK) with a zig-zag incision pattern. Patients were assessed preoperatively and underwent postoperative comprehensive examinations at standard intervals of 1, 3, 6, 9, and 12 months, and 6 months thereafter. Postoperative uncorrected distance visual acuity and spectacle-corrected distance visual acuity and manifest and topographical (Mrx cyl and Topo cyl) astigmatism were compared with preoperative values.

RESULTS

Three hundred thirty-five eyes received FLEK with zig-zag configuration. Data are presented for the last recorded visit before any refractive procedure. Sutures were removed in 202 of 335 eyes at an average time to removal of 1.3 ± 1.1 years, and a mean follow-up period of 2.9 ± 2.1 years (range 0-10 years). After full suture removal, mean uncorrected distance visual acuity and spectacle-corrected distance visual acuity were logarithm of the minimum angle of resolution 0.84 (Snellen 20/138) ± 0.55 and 0.33 (Snellen 20/42) ± 0.33, respectively. Mean Mrx cyl and Topo cyl of these groups were 3.38 ± 2.22 and 4.77 ± 3.15, respectively. Of the total number of grafts, the rate of graft rejections was 14.0%, and the failure rate was 5.6%.

CONCLUSIONS

The femtosecond laser-generated zig-zag-shaped incision results in lower manifest and topographical astigmatism than the reported average for conventional penetrating keratoplasty. Graft rejection and failure rates are similar to published data for conventional penetrating keratoplasty.

Contralateral eye study of refractive, topographic and aberrometric outcomes after femtosecond assisted MyoRing implantation and DALK for management of keratoconus

AIM

To evaluate the efficacy of femtosecond laser assisted MyoRing intrastromal corneal implant and deep anterior lamellar keratoplasty (DALK) for management of moderate to advanced keratoconus regarding the degree of changes in visual acuity, refraction, corneal asphericity and aberrations.

METHODS

A prospective non comparative interventional case study was conducted in Ophthalmology Department, Ain Shams University Hospital in the period from January 2015 to February 2017. The study included 30 eyes of moderate to advanced keratoconus. MyoRing was implanted in one eye (Group I) and DALK operation was performed in the contralateral eye of the same patient (Group II). Preoperative and 6mo post-operative uncorrected visual acuity (UCVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), corneal and refractive astigmatisms, keratometry and Q-value using topography images were acquired. Quality of vision was assessed in all eyes including total corneal, anterior corneal high order aberrations analysis at 5 mm pupil size and the Strehl ratio of point spread function (PSF) as an objective measure of glare.

RESULTS

Mean postoperative UCVA, CDVA, SE, refractive astigmatism, keratometry readings and asphericity were statistically improved compared to preoperative parameters in both groups (P<0.05). Significant reduction of all corneal aberrations following both techniques (P<0.05) was achieved except mean trefoil and mean PSF in Group I (P>0.05). Postoperative corneal aberrations were significantly lower in Group II compared to Group I. A statistically significant negative correlation was found in Group I between the mean change in CDVA (logMAR) and the mean preoperative and mean postoperative total corneal aberrations root mean square (RMS; r=-0.78, P=0.04). Also a statistically significant negative correlation was found between mean preoperative coma RMS and mean post PSF (r=-0.86, P=0.01). In Group II, there was a statistically significant positive correlation between mean change in CDVA (logMAR) and mean change in Kmax (r=0.87, P=0.01) and between mean change in refractive cylinder and mean postoperative PSF (r=0.76, P=0.05).

CONCLUSION

Femtosecond laser assisted MyoRing and DALK are effective in improving visual acuities, refraction, corneal asphericity and aberrations. MyoRing reduced spherical error more than the corneal cylinder. Post operative homogenous corneal surface and good image quality were achieved following both techniques compared to the preoperative state. However, DALK results in better image quality and lower corneal aberrations.

Early Changes in Visual Quality and Corneal Structure after DMEK: Does DMEK Approach Optical Quality of a Healthy Cornea?

Purpose

To evaluate early changes in visual function and visual quality parameters after Descemet membrane endothelial keratoplasty (DMEK) and to compare the outcomes with healthy controls.

Methods

Thirteen patients who underwent DMEK and 14 controls were evaluated. All subjects underwent visual function evaluation, including visual acuity under photopic and mesopic lighting conditions and contrast sensitivity (CSV) tests CSV 1000 and Pelli-Robson. Corneal parameters were assessed with Oculus Pentacam. Corneal mean keratometry (Km), corneal densitometry values, and low and high order aberrations (LOA and HOA) were recorded. In DMEK patients, all tests were performed before surgery and 1 and 6 months after surgery.

Results

In patients who underwent DMEK, photopic visual acuity improved from 0.59 to 0.31 at 1 month (p=0.013) and 0.13 at 6 months (p=0.008); mesopic visual acuity and all contrast sensitivity values (both CSV and Pelli-Robson test) improved significantly in the first month (p < 0.005). A significant decrease was observed in corneal density in the 0-2 mm ring (from 43.83 to 35.60, p=0.043) and mean posterior Km (from -5.84 to -6.80, p=0.005) in the first month. Corneal HOAs and all corneal densities improved at 6 months after DMEK (p < 0.05). All visual function parameters and corneal aberrations remained lower and higher, respectively, compared with healthy controls (p < 0.05). Corneal densities were comparable with controls at 6 months after DMEK (p > 0.05).

Conclusions

Patients undergoing DMEK present visual function improvement and a decrease in corneal density at 1 month after surgery. Decrease in corneal posterior HOAs can be observed at 6 months. However, visual function outcomes and corneal aberrations remained worse compared with healthy controls.

Factors Limiting the Visual Outcome After Descemet Stripping Automated Endothelial Keratoplasty: Comprehensive Analysis Including the Graft Position and Irregularity

PURPOSE

To investigate factors affecting best postoperative corrected distance visual acuity (CDVA) in patients who have undergone Descemet stripping automated endothelial keratoplasty (DSAEK).

METHODS

Forty-two eyes of 42 patients with predominantly non-Fuchs endothelial corneal dystrophy after DSAEK were retrospectively evaluated. All patients were examined using anterior segment optical coherence tomography when their best postoperative CDVA had been achieved. We analyzed the relationship between best postoperative CDVA and preoperative, intraoperative, and postoperative factors, including corneal higher-order aberrations (HOAs), corneal backward scattering, graft irregularity, and graft decentration. Variables with P < 0.2 in univariate analysis were entered into a multivariate linear regression model to determine the factors affecting best postoperative CDVA.

RESULTS

Mean CDVA improved from 1.16 ± 0.46 preoperatively to 0.22 ± 0.19 logarithm of the minimum angle of resolution equivalents postoperatively (P < 0.0001). Best postoperative CDVA was achieved 11.6 ± 7.7 months after DSAEK. Multivariate analysis showed that anterior corneal coma-like HOAs and venting incisions inside the pupil area were significantly correlated with best postoperative CDVA (t = 2.90, P = 0.006; t = 2.62, P = 0.01, respectively). No significant relationship was found between the visual outcome and any other factor, including posterior corneal HOAs, corneal backward scattering, graft decentration, and graft irregularity.

CONCLUSIONS

Irregularity of the anterior corneal surface and venting incisions inside the pupil area are important factors that impair best postoperative CDVA in patients who have undergone DSAEK. In contrast, our results indicate that the graft position and irregularity might not have a strong influence on the visual outcome after DSAEK.

Impact of Forward and Backward Scattering and Corneal Higher-Order Aberrations on Visual Acuity after Penetrating Keratoplasty

PURPOSE

To assess the relationship of forward and backward scattering and corneal higher-order aberrations (HOAs) with corrected distance visual acuity (CDVA) after penetrating keratoplasty (PK).

METHODS

This retrospective study comprised 25 eyes of 25 consecutive patients who underwent PK using the VisuMax femtosecond laser system and age-matched 25 eyes of 25 healthy subjects. We quantitatively assessed objective scattering index (OSI) using the double-pass instrument (OQAS II, Visiometrics), corneal densitometry (CD) and corneal HOAs with the Scheimpflug rotating camera (Pentacam HR, Oculus) 1 year postoperatively.

RESULTS

The OSI, CD, and corneal HOAs were significantly larger in the PK group than those in the control group (p ≤ 0.011). We found significant correlations of logMAR CDVA with the OSI (r = 0.477, p = 0.016), and with the anterior, posterior, and total corneal HOAs of the central 4-mm zone (anterior: r = 0.573, p = 0.003, posterior: r = 0.596, p = 0.002, total: r = 0.472, p = 0.017), but no significant association with the CD of the 0-2 mm zone at any layers (anterior: r = 0.236, p = 0.257, center: r = 0.139, p = 0.506, posterior: r = 0.073, p = 0.728, total: r = 0.212, p = 0.308). Similar results were obtained when the analysis was repeated with corneal HOAs of the central 6-mm zone and CDs in 2-6 mm zone.

CONCLUSIONS

Our pilot study demonstrated that the postoperative CDVA was significantly correlated with OSI and corneal HOAs, but not with backward scattering in post-PK eyes, suggesting that OSI as well as corneal HOAs plays an essential role in postoperative visual performance after PK.

Visual outcomes following Descemet stripping automated endothelial keratoplasty for corneal endothelial dysfunction

OBJECTIVE

To assess objective and subjective visual outcomes achieved by patients with corneal endothelial dysfunction who have undergone surgical treatment with Descemet stripping automated endothelial keratoplasty (DSAEK).

METHODS

A total of 40 eyes of 36 patients with corneal endothelial dysfunction underwent DSAEK. All were followed up for 1 year. Visual acuity (VA; logMAR), mean endothelial cell density (MCD; via noncontact specular microscopy), and topography assessment were performed at baseline (preoperatively). Visual acuity and topography measurement were repeated at postoperative year 1. Subjective assessment of visual quality was evaluated using the National Eye Institute Visual Function Questionnaire (NEI-VFQ).

RESULTS

Preoperative best-corrected VA (BCVA) was 1.29 ± 0.53 logMAR with mean optical correction of -0.33 ± 1.74 D. Postoperative BCVA, assessed after a mean of 10.8 ± 2.1 months, showed mean line gain of 7.11 ± 4.8 logMAR, with optical correction of +1.17 ± 1.54 D. Mean 6-month postoperative pachymetry was 598.2 ± 72.3 µm. Three patients experienced premature graft detachment, requiring repositioning via injection of a sterile air bubble. No other adverse events were observed. Significant improvement (p<.05 for all) in general, near, and far vision, ocular pain, difficulty in carrying out daily tasks, dependency, social life, and mental health were reflected by NEI-VFQ scores at 10.4 ± 2.1 months postoperatively versus preoperatively. No significant correlation was noted between postoperative VA line gain and NEI-VFQ-25 questionnaire score (p>0.05).

CONCLUSIONS

Descemet stripping automated endothelial keratoplasty treatment may restore corneal clarity, improve VA, and increase vision-related quality of life in patients with advanced endothelial dysfunction. Further large-scale study is needed to corroborate these findings.

Quality of Vision after Deep Anterior Lamellar Keratoplasty (Fluid Dissection) Compared to Penetrating Keratoplasty for the Treatment of Keratoconus

Purpose

To compare the visual quality of patients with keratoconus who underwent penetrating keratoplasty (PKP) or deep anterior lamellar keratoplasty (DALK) with fluid dissection.

Design

Cross-sectional, observational study.

Methods

Twelve eyes that underwent PKP (PKP group) were compared to 24 eyes that underwent DALK (DALK group) after complete removal of sutures and stability of refraction. Visual, refractive, corneal topographic, corneal aberrometry, and ocular aberrometry parameters were compared for both groups. The χ² and Mann–Whitney U tests were used for comparisons as appropriate. P < 0.05 was considered statistically significant.

Results

Uncorrected and best spectacle-corrected visual acuity (UCVA and BSCVA, resp.), mean refractive spherical equivalent and mean refractive cylinder (MRSE and MRC, resp.), root mean square of the 3 mm and 5 mm OPD Scan (NIDEK Co. Ltd., Gamagori, Japan), steep and flat meridians (SimK1 and SimK2, resp.), and the difference (corneal cylinder) were not statistically significantly different between groups (P > 0.05, all comparisons). All aberrations, point spread functions (PSF), and the modulation transfer function (MTF) were not statistically different between groups (P > 0.05).

Conclusion

For our small study, the postoperative PKP and DALK with fluid dissection patient groups had vision/optical quality parameters that were not statistically different. This may indicate that DALK with fluid dissection can replace PKP for keratoconus without compromising vision quality.

[Visual outcomes after Descemet's membrane endothelial keratoplasty]

OBJECTIVES

Evaluation and monitoring at 6 months after Descemet's membrane endothelial keratoplasty (DMEK) in patients with Fuchs endothelial dystrophy and study of factors influencing visual rehabilitation and postoperative quality of life.

METHODS

Prospective, consecutive, interventional study of 35 eyes of 32 patients with Fuchs endothelial dystrophy who underwent surgery from February 2015 to February 2016 by DMEK. Measurement at D10, M1, M3, M6 of visual acuity, graft endothelial cell density, pachymetry, and intraocular pressure, and performance at M6 of aberrometry, macular OCT and a quality of life survey (NEI-VFQ-25). Post-DMEK aberrations are compared to those from control patients selected for refractive surgery.

RESULTS

Visual acuity improvement at 6 months was statistically significant (P<0.0001), as well as pachymetry decrease (P<0.0001), endothelial cell loss (P<0.0001) and intraocular pressure increase (P=0.003). We observed a statistically significant difference between post-DMEK aberrations and those of control subjects for all aberrations from 2nd to 5th order. There were no postoperative correlations between visual acuity, pachymetry, intraocular pressure, or endothelial cell loss. The global quality of life score at six months was 87, corresponding to a good quality of life. We did not find a link between the global NEI-VFQ-25 score and visual acuity or visual aberrations. Ninety percent of patients surveyed reported a postoperative general improvement in quality of life at M6.

CONCLUSION

DMEK provides good visual rehabilitation and an improvement in quality of life for patients with Fuchs endothelial dystrophy. Higher order optical aberrations in these patients, although higher than in a healthy population, are negligible and have no impact on quality of vision or postoperative quality of life.

Determinants of visual quality after endothelial keratoplasty

Endothelial keratoplasty is now favored over full-thickness penetrating keratoplasty for corneal decompensation secondary to endothelial dysfunction. Although endothelial keratoplasty has evolved as surgeons strive to improve outcomes, fewer patients than expected achieve best corrected visual acuity of 20/20 despite healthy grafts and no ocular comorbidities. Reasons for this remain unclear, with theories including anterior stromal changes, differences in graft thickness and regularity, induced high-order aberrations, and the nature of the graft-host interface. Newer iterations of endothelial keratoplasty such as thin manual Descemet stripping endothelial keratoplasty, ultrathin automated Descemet stripping endothelial keratoplasty, and Descemet membrane endothelial keratoplasty have achieved rates of 20/20 acuity of approximately 50%, comparable to modern cataract surgery, and it may be that a ceiling exists, particularly in the older age group of patients. Establishing the relative contribution of the factors that determine visual quality following endothelial keratoplasty will help drive further innovation, optimizing visual and patient-reported outcomes while improving surgical efficacy and safety.

Descemet stripping automated endothelial keratoplasty in Fuchs' corneal endothelial dystrophy: anterior segment optical coherence tomography and in vivo confocal microscopy analysis

Background

To evaluate the in vivo corneal changes using in vivo confocal microscopy (IVCM) and anterior segment optical coherence tomography (AS-OCT) in patients with Fuchs’ dystrophy who underwent Descemet stripping automated endothelial keratoplasty (DSAEK) and the relationship between these changes and the postoperative visual recovery up to 1-year follow-up.

Methods

Before DSAEK and 1 day, 3, 6 and 12 months after surgery 31 patients (39 pseudophakic eyes) underwent a complete ophthalmological evaluation including best corrected visual acuity (BCVA), IVCM (subepithelial haze, interface haze, graft thickness) and AS-OCT (graft thickness).

Results

Graft thickness measurements by AS-OCT were strongly correlated to those obtained using IVCM at every follow-up stage (intraclass correlation coefficient = 0.95 to 0.97 between 3 and 12 months, P < 0.001 for all coefficients). No correlation between BCVA and graft thickness measured by AS-OCT at any follow-up stage was found, while at 3 and 6 postoperative months the correlations between BCVA and preoperative subepithelial haze (r = 0.61, P < 0.001 and r = 0.46, P = 0.002), interface haze (r = 0.51, P < 0.001 and r = 0.46, P = 0.003), postoperative subepithelial haze (r = 0.43, P = 0.004 and r = 0.39, P = 0.001) were significant.

Conclusions

The study confirmed corneal subepithelial haze and interface haze as important factors limiting visual acuity after DSAEK, while graft thickness was not related to BCVA.

Effect of Intraocular Forward Scattering and Corneal Higher-Order Aberrations on Visual Acuity after Descemet's Stripping Automated Endothelial Keratoplasty

Purpose

To assess the relationship of intraocular forward scattering and corneal higher-order aberrations (HOAs) with best spectacle corrected visual acuity (BSCVA) after Descemet’s stripping automated endothelial keratoplasty (DSAEK), and to compare these parameters between DSAEK and non-Descemet’s stripping automated endothelial keratoplasty (n-DSAEK) groups.

Methods

This retrospective study enrolled thirty eyes of 30 consecutive patients who underwent standard DSAEK, and who underwent successful phacoemulsification with intraocular lens implantation before DSAEK. The mean age at the time of surgery was 71.7 ± 10.4 years. We quantitatively evaluated the objective scattering index (OSI) using the double-pass instrument (OQAS II, Visiometrics) and corneal HOAs using Hartmann-Shack aberrometry (KR-9000PW, Topcon) 3 months postoperatively.

Results

The mean OSI, corneal HOAs, and logMAR BSCVA 3 months after DSAEK were 7.91 ± 3.58, 0.43 ± 0.27 μm, and 0.32 ± 0.25, respectively. We found a significant correlation between the OSI and logMAR BSCVA (Spearman correlation coefficient r=0.714, p<0.001), but no significant association between corneal HOAs and logMAR BSCVA 3 months postoperatively (r=0.209, p=0.267). We found no significant differences in any postoperative parameters between the DSAEK and n-DSAEK groups (p>0.05).

Conclusions

Our pilot study demonstrated that the postoperative corrected visual acuity was significantly correlated with intraocular forward scattering, but not with corneal HOAs in post-DSAEK eyes, suggesting that intraocular forward scattering plays a more essential role in postoperative visual performance than corneal aberrations after DSAEK. The detailed visual performance, such as HOAs and intraocular scattering, after n-DSAEK appears to be essentially equivalent to that after DSAEK.

Eye Bank-Prepared Femtosecond Laser-Assisted Automated Descemet Membrane Endothelial Grafts

PURPOSE

The aim of this study was to investigate the use of a femtosecond laser (FL) in the eye bank preparation of corneas for Descemet membrane (DM) automated endothelial keratoplasty (fDMAEK) and to compare endothelial cell death in graft preparations between fDMAEK, Descemet stripping endothelial keratoplasty (DSEK), and DM endothelial keratoplasty (DMEK).

METHODS

Twenty cadaveric tissues were used to test the fDMAEK method. A 9.0-mm-diameter lamellar incision was made using the FL with a 6.0-mm perpendicular anterior ring cut that enabled a stromal rim by acting as a venting incision for bubble expansion. DM was pneumodissected off the central 6.0 mm of the tissue. The fDMAEK grafts were trephined and stained with a viability dye, calcein AM. The entire stained endothelial surface was digitally captured and the endothelial cell loss (ECL) was calculated using trainable segmentation software. For comparison, a series of 6 DSEK grafts and 8 DMEK grafts were created and analyzed.

RESULTS

Six of 20 tissues (30%) were lost during fDMAEK preparation. In the 14 successful tissues, the average ECL was 30.4% [95% confidence interval (CI), 25.3-35.6] compared with 21.1% (95% CI, 13.2-28.9, P = 0.09) in the 6 DSEK grafts and 22.5% (95% CI, 18.0-27.0, P = 0.04) in the 8 DMEK grafts.

CONCLUSIONS

FLs are useful in preparing DMAEK tissue at the eye bank and may promote predictable and precise big bubbles and stromal rims. The fDMAEK preparation success improved with experience and laser adjustments. In fDMAEK, the ECL is higher than was previously reported in DMEK and DSEK, likely due to greater tissue manipulation, although not significantly higher than DSEK controls.

Optical quality of the cornea after Descemet membrane endothelial keratoplasty

PURPOSE

To evaluate corneal higher-order aberrations (HOAs) and backscattered light before and after Descemet membrane endothelial keratoplasty (DMEK) and their correlation with visual outcome.

DESIGN

Retrospective study.

METHODS

In a total of 118 consecutive eyes of 118 patients who underwent uneventful DMEK for Fuchs endothelial dystrophy at a tertiary referral center, best spectacle-corrected visual acuity (BSCVA), corneal HOAs, and backscattered light were evaluated preoperatively and at 6 months postoperatively. Outcome data were compared to an age-matched control group with uncomplicated eyes (n = 27).

RESULTS

Compared to the control group, Fuchs endothelial dystrophy eyes, before as well as 6 months after DMEK, showed higher values of anterior and posterior HOAs and backscattered light (P < .033). Postoperative anterior HOAs and backscattered light (0-2 mm) were associated with lower 6-month BSCVA (positively related with logMAR BSCVA) (P ≤ .020). Anterior corneal HOAs did not change from preoperative to 6 months after DMEK (P = .649), while total posterior HOAs (RMS third to sixth Zernike order) and haze decreased (P < .001).

CONCLUSIONS

Anterior and posterior corneal HOAs, as well as backscattered light from the cornea, were elevated in eyes suffering from Fuchs endothelial dystrophy and remained higher throughout 6 months after DMEK. If present, anterior surface irregularities and anterior corneal haze may be the most important limiting factors in visual rehabilitation after DMEK.

Post-DSAEK optical changes: a comprehensive prospective analysis on the role of ocular wavefront aberrations, haze, and corneal thickness

PURPOSE

The aim was to assess the visual impact of ocular wavefront aberrations, corneal thickness, and corneal light scatter prospectively after performing a Descemet stripping automated endothelial keratoplasty (DSAEK) in humans.

METHODS

Data were obtained prospectively from 20 eyes preoperatively and at 1, 3, 6, and 12 months post-DSAEK. At each visit, the best spectacle-corrected visual acuity and visual acuity with glare (brightness acuity testing) were recorded, and ocular wavefront measurements and corneal optical coherence tomography (OCT) were performed. The magnitude and the sign of individual Zernike terms [higher-order aberrations (HOAs)] were determined. Epithelial, host stromal, donor stromal, and total corneal thicknesses were quantified. The brightness and intensity profiles of OCT images were generated to quantify light scatter in the whole cornea, subepithelial region, anterior and posterior host stroma, interface, and donor stroma.

RESULTS

The mean best spectacle-corrected visual acuity and glare disability at low light levels improved from 1 to 12 months post-DSAEK. All corneal thicknesses and ocular lower-order aberrations and HOAs were found to be stable from 1 to 12 months, whereas total corneal, host stromal, and interface brightness intensities decreased significantly over the same period. A repeated measures analysis of variance performed across the follow-up period revealed that the change in scatter, but not the change in the HOAs, could account for the variability occurring in the acuity from 1 to 12 months post-DSAEK.

CONCLUSIONS

Although ocular HOAs and scatter are both elevated over normal values post-DSAEK, our results demonstrate that the improvements in visual performance occurring over the first year post-DSAEK are associated with decreasing light scatter. In contrast, there were no significant changes in the ocular HOAs during this time. Because corneal light scatter decreased between 1 and 12 months despite there being stable corneal thicknesses over the same period, we conclude that factors that induced light scatter, other than tissue thickness or swelling (corneal edema), significantly impacted the visual improvements that occurred over time post-DSAEK. A better understanding of the cellular and extracellular matrix changes of the subepithelial region and interface, incurred by the surgical creation of a lamellar host-graft interface, and the subsequent healing of these tissues, is warranted.

Correlation between visual acuity and interface reflectivity measured by pentacam following DSAEK

PURPOSE

Descemet-stripping automated endothelial keratoplasty (DSAEK) is an advanced method of lamellar endothelial keratoplasty. In comparison with penetrating keratoplasty, visual rehabilitation seems to be faster. Final visual outcome of DSAEK, however, seems to be limited, especially in comparison with Descemet membrane endothelial keratoplasty (DMEK). DSAEK cases without graft failure often do not show any definite correlate for the reduced optical performance. In this study, we tried to correlate visual acuity following DSAEK with interface reflectivity as measured by a rotating Scheimpflug system.

METHODS

We examined 14 eyes of 13 patients with the pentacam for 2-11 months following DSAEK. Reflectivity of the interface region in the centre of the optical axis as well as central corneal thickness was determined. Statistical correlation between interface reflectivity and best spectacle-corrected visual acuity, central corneal thickness and follow-up time was drawn (multifactorial linear regression analysis).

RESULTS

Statistically significant correlation between interface reflectivity and BSCVA as well as follow-up time was found. Reflectivity was highest in regions of interface (metal) particles. There was no statistically significant correlation between interface reflectivity and central corneal thickness.

CONCLUSION

We present a measurable correlate for reduced visual outcome following DSAEK despite a clear graft. Inverse correlation between interface reflectivity and best spectacle-corrected visual acuity (BSCVA) indicates that irregularities or scarring in the interface region may influence the optical quality following DSAEK.

Postkeratoplasty Anterior and Posterior Corneal Surface Wavefront Analysis: Descemet's Stripping Automated Endothelial Keratoplasty versus Penetrating Keratoplasty

Purpose. To compare the higher-order aberrations (HOAs) due to the anterior and posterior corneal surfaces in patients that underwent either Descemet-stripping-automated-endothelial-keratoplasty (DSAEK) or penetrating keratoplasty (PK) for endothelial dysfunction and age-matched controls. Methods. This retrospective, observational, case series included 28 patients after PK, 30 patients after DSAEK, and 30 healthy controls. A Scheimpflug imaging system was used to assess the HOAs due to the anterior and posterior corneal surfaces at 4 mm and 6 mm optical zones. Total, 3rd and 4th order HOAs were considered. Intra- and intergroup differences were assessed using the Friedman and the Kruskal-Wallis tests, respectively; paired comparisons were performed using Duncan's multiple range test. Results. Total, 3rd and 4th order HOAs due to both corneal surfaces at 4 mm and 6 mm optical zones were significantly higher in the PK group, intermediate in the DSAEK group, and lower in controls (P < 0.05). The most important HOAs components in both PK and DSAEK groups were trefoil and coma from the anterior corneal surface (P < 0.05) and trefoil from the posterior corneal surface (P < 0.05). Conclusions. The optical quality of both corneal surfaces appeared significantly higher after DSAEK than after PK, which can increase the postoperative patient's quality of vision and satisfaction.

Application of the femtosecond laser LASIK microkeratome in eye banking

PURPOSE OF REVIEW

To review the literature for recent advancements in the femtosecond laser technology with regard to its applications in corneal transplantation and eye banking.

RECENT FINDINGS

Advancements in corneal surgery have encouraged the use of disease-specific corneal subcomponents, utilized in procedures such as anterior-lamellar keratoplasty and endothelial keratoplasty, instead of traditional transplant procedures to minimize adverse effects of penetrating keratoplasty. Femtosecond laser microkeratomes can precisely create flaps for such transplant procedures, achieve better wound stability, and promote healing by shaped wound configurations. Laser microkeratomes have been compared to traditional mechanical microkeratomes for keratoplasty procedures from various aspects and are superior in some aspects and offer unique capabilities.

SUMMARY

Femtosecond laser applications in eye banking include preparation of donor and recipient corneas for use in penetrating keratoplasty, anterior-lamellar keratoplasty, and endothelial keratoplasty. Advantages of femtosecond laser microkeratomes include higher precision of the cut, ability to achieve thinner flaps, and wound configurations that allow greater wound stability, shorter recovery time, and less postoperative pain. However, cost and availability at the eye-bank level may hinder widespread and immediate application.