Contrast sensitivity in deep anterior lamellar keratoplasty versus penetrating keratoplasty

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.

Indications of Keratoplasty and Outcomes of Deep Anterior Lamellar Keratoplasty Compared to Penetrating Keratoplasty

Background

Corneal diseases are a significant cause of visual impairment and blindness. Despite the treatable nature of many corneal diseases before visual demise, many cases of advanced disease necessitating keratoplasty for visual rehabilitation are encountered. A mismatch between the number of corneal donors and potential recipients also exists worldwide, with underutilization of certain types of keratoplasty techniques that may allow more efficient use of this limited resource.

Methodology

A retrospective cohort study of all cases of optical corneal transplantations performed from January 1, 2015 to October 31, 2020 was performed. Indications for keratoplasty, type of keratoplasty, complications, intraocular pressure elevation, and best corrected visual acuity (BCVA) by category and range at different time intervals were collected and analyzed. Findings were compared between penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) for all indications, specifically for keratoconus (KCN).

Results

A total of 58 corneal transplants meeting our criteria were performed during the study period. PK was performed for 29 eyes, DALK for 28 eyes, and endothelial keratoplasty for one eye. The most frequently encountered indication was KCN (62.1%). The number of eyes with BCVA of 20/100 or better increased from preoperative BCVA, 37/58 eyes had BCVA worse than 20/100 before keratoplasty (63.8%), while at the time of last follow-up 45/58 eyes had BCVA of 20/100 or better (77.6%). At the time of last follow-up 16/58 had BCVA in the range of 20/20 to 20/40 (27.6%) and 29/58 eyes had BCVA in the range of 20/50 to 20/100 (50%). Comparison of all cases of PK to DALK for all indications showed significantly better BCVA by category at one year, at last follow-up, and BCVA range at last follow-up (p = 0.032, 0.001, and 0.014, respectively). Although better visual acuity results by category and range at one year and last follow-up, respectively, were observed in more patients undergoing DALK than PK, for KCN the results were not statistically significant (p = 1.00, 1.00, 0.417, and 0.374, respectively). Overall, 70% of recorded complications, intraocular pressure (IOP) elevations, and graft rejections were seen in eyes that underwent PK; however, these findings were not statistically significant (p = 0.297). Graft failures occurred more frequently with PK than deep anterior keratoplasty when analyzed for all indications of keratoplasty (p = 0.010).

Conclusions

Despite advancement and improvements in surgical techniques, statistics continue to show underutilization of the invaluable resource of donor corneas, with PK still being performed more than DALK for diseases that do not affect the endothelium. Our study found superior visual acuity outcomes of DALK as well as the advantages of less frequent complications, IOP elevations, graft rejections, and graft failures. We encourage ophthalmologists to utilize DALK in appropriate candidates to more fully utilize the scarce and potentially vision-restoring resource of donor corneal tissue.

Femtosecond laser-assisted deep anterior lamellar keratoplasty in phototherapeutic keratectomy versus the big-bubble technique in keratoconus

AIM

To compare the functional and anatomic results of femtosecond laser (FSL)-assisted deep anterior lamellar keratoplasty (DALK) associated with phototherapeutic keratectomy (PTK) and FSL-assisted DALK performed using the big-bubble technique in keratoconus.

METHODS

During the first phase of the study, an electron microscopy histopathology pilot study was conducted that included four unsuitable donor corneas divided into two groups: in FSL group, FSL lamellar cuts were performed on two corneas and in FSL+PTK group, PTK was performed at the stromal beds of two corneas after FSL lamellar cuts were made. During the second phase of the study, a randomized clinical trial was conducted that included two treatment groups of patients with keratoconus: group 1 (n=14 eyes) underwent FSL-assisted DALK associated with PTK and group 2 (n=12 eyes) underwent FSL-assisted DALK associated with the big-bubble technique. The main outcome measures were the postoperative visual acuity (VA) and optical coherence tomography (OCT) measurements, confocal microscopic findings, and contrast sensitivity.

RESULTS

In the pilot study, histopathology showed a more regular stromal bed in the FSL+PTK group. In the clinical trial, group 1 had significantly worse best spectacle-corrected VA and contrast sensitivity (P<0.05 for both comparisons). The residual stromal bed measured by OCT was significantly (P<0.05) thicker in group 1. Confocal microscopy detected opacities only at the donor-receptor interface in group 1.

CONCLUSION

Patients with keratoconus treated with FSL-assisted DALK performed using the big-bubble technique fare better than treated with FSL-assisted DALK associated with PTK.

Comparison of Outcomes in Patients Who Underwent Deep Anterior Lamellar Keratoplasty and Those Converted to Penetrating Keratoplasty

OBJECTIVES

To compare clinical outcomes of cases who underwent deep anterior lamellar keratoplasty (DALK) and cases who were converted to penetrating keratoplasty (PKP) from DALK surgery.

MATERIALS AND METHODS

The records of 54 patients for whom DALK surgery was planned and were operated for different diagnoses between March 2013 and June 2015 were retrospectively analyzed. Patients were divided into two groups: group 1 (PKP group) consisted of 23 cases who were converted to PKP due to Descemet's membrane perforation at any stage of surgery; group 2 (DALK group) consisted of 31 patients whose surgery could be completed as DALK. Preoperative and postoperative follow-up results were evaluated in each group.

RESULTS

Corrected distance visual acuity (CDVA) increased in the postoperative period according to baseline in both groups. However, there was no statistically significant difference in the rates of CDVA increase between the groups (p=0.142). The mean astigmatism measured by corneal topography at final examination was 5.8±2.3 diopters in group 1 and 5.4±1.8 diopters in group 2. The difference between groups was not statistically significant (p=0.430). The groups were not statistically different regarding postoperative pachymetry (p=0.453). The grafts in all 54 patients (100%) were clear at final postoperative examination. There were no statistically significant differences between the groups in terms of postoperative complications.

CONCLUSION

Similar clinical outcomes were obtained in our study for patients who underwent DALK and those whose procedure was converted from DALK to PKP.

Surgical outcome of deep anterior lamellar keratoplasty with air-assisted manual dissection for corneas with previous inflammation or fibrosis

PURPOSE:

To report our experience in air-assisted manual dissection deep anterior lamellar keratoplasty (DALK) for the treatment of corneal scar with previous inflammation and fibrosis.

MATERIALS AND METHODS:

We retrospectively reviewed the medical history of 21 patients (male:female = 13:8 mean age 41.9 years old) with corneal pathology from previous infection and inflammation. Trephination diameter ranged from 7.0 to 8.0 mm, and the graft was oversized by 0.25–0.50 mm. Debulking technique was performed to expose Descemet's membrane after filling stroma with air. Starting from postoperative 3 months, selective suture removal was performed to reduce corneal astigmatism.

RESULTS:

The mean follow-up period was 59.9 ± 19.8 (20–96) months. Intraoperative microperforation occurred in 2 eyes (9.5%); however, there was no shift to penetrating keratoplasty. Air-bubble tamponade was performed in 7 eyes (33.3%) for postoperative gapping of the graft. There were 2 failed grafts (9.5%) due to corneal ulcer while all the other grafts remained clear throughout follow-up. The mean preoperative best-corrected visual acuity (BCVA) was 1.84 ± 0.66 logMAR, which improved to 0.74 ± 0.63 (P < 0.01). The average sphere power was − 0.88 ± 3.88 diopter (D), average cylinder power 3.03 ± 1.46D, and average endothelial count 1877 ± 375 cells/mm².

CONCLUSION:

In severe ocular surface diseases, big-bubble technique frequently failed to separate predescemtic plane; however, it effectively created air-filled stroma which was easier to remove. Although BCVA was suboptimal due to ocular surface disorders, graft survival and clarity rate is high, justifying the application of DALK in these cases.

Clinical outcomes and risk factors for graft failure after deep anterior lamellar keratoplasty and penetrating keratoplasty for macular corneal dystrophy

PURPOSE

The aim of this study was to compare visual acuity, clinical outcomes, complications, and risk factors for graft failure after deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) for macular corneal dystrophy.

METHODS

Retrospective comparative case series.

RESULTS

The PK group consisted of 109 eyes of 84 patients and the DALK group consisted of 21 eyes of 20 patients. The mean logarithm of the minimum angle of resolution best-corrected visual acuity at 3 and 12 months was 0.5 versus 0.5 (P = 0.285) and 0.4 versus 0.4 (P = 0.67) in the DALK and PK groups, respectively. There was no significant statistical difference in astigmatism and spherical equivalent between the 2 groups at 12 months. In the PK group, graft rejection that was the most common cause of graft failure was seen in 27 eyes (25%), of which 55% occurred within 1 year. In the DALK group, Descemet membrane microperforation occurred in 5 eyes (24%) intraoperatively, and early postoperative Descemet membrane detachment with double anterior chamber occurred in 9 eyes (43%). Kaplan-Meier estimate of graft survival in PK versus DALK groups were 93% versus 80% at 1 year and 78% versus 70% at 4 years, respectively.

CONCLUSIONS

Visual and refractive outcomes are comparable between DALK and PK groups. DALK was superior to PK in its safety against postoperative complications such as endothelial rejection and secondary glaucoma. Graft failure in DALK was mostly associated with either intraoperative or early postoperative complications. DALK is a viable surgical option in cases with macular corneal dystrophy.

Comparative study of keratoconus between Anwar's deep anterior lamellar keratoplasty versus converted penetrating keratoplasty

OBJECTIVE

To compare outcomes between penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) in patients with keratoconus.

DESIGN

Retrospective cohort study.

METHODS

Data of 90 DALK and 49 procedures from conversion to PK, performed by a single surgeon (R.D.) from 2006 to 2011 were analysed. Outcomes on corrected distance visual acuity (BCVA), astigmatism, time to first refraction, pachymetry, endothelial count cell, and postoperative complications were compared between these groups.

RESULTS

The mean age of the patients who underwent DALK and PK was 28.2 and 31.7 years, respectively (P=.17). The mean follow up for DALK and for the PK group was 14.7 and 19.4 months, respectively (P=.13). There was no significant difference between PK and DALK groups in the mean postoperative for: BCVA (LogMAR) (0.17 vs. 0.17; P=.59); refractive astigmatism (-3.19 vs.-3.01 diopters; P=.65), and time for the first subjective refraction (60.5 versus 68 days; P=.50). Main postoperative complications were 8% of endothelial rejection in PK group and 10% of deep stromal vascularization in DALK group.

CONCLUSIONS

The only differences in postoperative results between groups were stromal neovascularization in DALK group and endothelial rejection in PK group. DALK should be considered as the first option when keratoplasty is indicated in keratoconus.

[Corneal transplantation in keratoconus: penetrating keratoplasty versus deep anterior lamellar keratoplasty with Melles technique]

OBJECTIVES

To evaluate the effectiveness of deep anterior lamellar keratoplasty (DALK) using Melles technique (technique B) in patients with advanced keratoconus versus a classic technique, penetrating keratoplasty (technique A).

METHODOLOGY

Retrospective descriptive comparative study between technique A and technique B in homogeneous groups.

RESULTS

Best corrected visual acuity (Snellen test decimal scale) was 0.77±0.32 for group A and 0.62±0.29 for group B, with no statistically significant differences. The mean spherical final refraction in group A was 1.73±5.1 diopters, and the mean spherical equivalent was -3.92±5.1. Technique B group gave values -2.67±4.02 diopters and -4.55±4.08 diopters, respectively, with no statistically significant differences. The residual cylinder after removal of the sutures was 4.47±2.47 diopters for group A and 3.77±1.63 for group B, with no statistically significant differences.

CONCLUSION

No statistically significant differences were found for any of the studied variables when comparing both groups using the t -test for independent samples. More studies on the homogeneity and residual stromal bed thickness could provide the key to determine whether this technique is closer to the visual acuity of penetrating keratoplasty or DALK by a descemet technique.

Comparison of descemet-on versus descemet-off deep anterior lamellar keratoplasty

PURPOSE

To determine the effect of retained donor Descemet membrane (DMs) on visual outcomes, contrast sensitivity (CS), higher-order aberrations (HOAs), and central graft thickness after deep anterior lamellar keratoplasty (DALK) using the big-bubble technique.

METHODS

In this retrospective comparative study, keratoconic eyes undergoing a DALK using the big-bubble technique were enrolled. A bared DM was achieved in all cases. A donor cornea without (group 1; 48 eyes) or with (group 2; 22 eyes) DM was sutured to the recipient bed. The 2 groups were compared in terms of best spectacle-corrected visual acuity, keratometric astigmatism, refractive error, CS, HOAs, and central graft thickness at least 3 months after complete suture removal. Additionally, the rate of postoperative pseudoanterior chamber formation was compared between the study groups.

RESULTS

The mean follow-up duration was 23.2 ± 6.9 months in group 1 and 26.5 ± 6.5 months in group 2 (P = 0.61). The postoperative best spectacle-corrected visual acuity was 0.18 ± 0.08 logMAR and 0.24 ± 0.30 logMAR, respectively (P = 0.36). The 2 groups had comparable postoperative keratometric astigmatism, spherical equivalent refraction, and HOAs. In terms of CS, however, group 1 demonstrated better results at a low spatial frequency. The mean postoperative central graft thickness was greater in group 2 (589.8 ± 34.5 μm) than in group 1 (523.6 ± 63.0 μm; P < 0.001). A pseudoanterior chamber developed in 3 eyes of group 1 and in 2 eyes of group 2 (P = 0.23). All cases were successfully managed by giving an intracameral air injection.

CONCLUSIONS

DALK performed using the big-bubble technique for keratoconus may give better results in terms of CS if a donor cornea without DM is transplanted.

A retrospective contralateral study comparing deep anterior lamellar keratoplasty with penetrating keratoplasty

PURPOSE

This study was conducted to compare endothelial cell (EC) loss, visual outcomes, and complications after deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) in the contralateral eyes of the same patients.

METHODS

A retrospective cohort study was undertaken at the Samsung Medical Center, Seoul Korea. We reviewed the records of 8 patients (16 eyes) who underwent PK in one eye and DALK in the contralateral eye. The DALK procedures were performed according to the Anwar and Teichmann big-bubble technique. EC loss, visual acuity, refractive status, and complications were evaluated to compare these techniques.

RESULTS

EC density was significantly higher after DALK compared with PK (at 12 months: 2045.8 ± 664.8 vs. 1732.6 ± 793.2, P = 0.044; at 24 months: 1900.3 ± 352.2 vs. 1416.2 ± 456.1, P = 0.013). The mean postoperative refractive astigmatism was -3.46 ± 2.57 diopters in the DALK-operated eyes versus -3.38 ± 2.48 diopters in the PK-operated eyes (P = 0.780), and the mean postoperative best-corrected visual acuity was 0.14 and 0.13 logarithm of the minimum angle of resolution, respectively (P = 0.870). There were no significant differences in the uncorrected visual acuity, best-corrected visual acuity, and refractive error between the DALK-operated and PK-operated eyes throughout the follow-up period. Rejection episodes were reported in 2 PK-operated eyes. No graft failures occurred.

CONCLUSIONS

Over the 2-year follow-up after DALK, EC loss was significantly lower, whereas the visual outcomes were comparable with those of the PK-operated eyes. No endothelial rejection occurred in the DALK-operated eyes. DALK is an effective alternative surgical procedure for corneal stromal pathologies.

Comparison of contrast sensitivity and visual acuity between deep anterior lamellar keratoplasty and penetrating keratoplasty in patients with keratoconus

AIM

To evaluate postoperative visual acuity and contrast sensitivity results following deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) in patients with keratoconus (KC).

METHODS

All the patients' records with KC who had PK or DALK surgery between May 2010 and May 2011 were retrospectively reviewed. Sixty patients who underwent successful corneal transplantation for KC: 30 eyes underwent DALK and 30 eyes underwent PK were included in this study. Preoperative and postoperative mean logarithm of the minimum angle of resolution (logMAR) uncorrected visual acuity (UCVA), logMAR best spectacle-corrected visual acuity (BSCVA) and intraocular pressure (IOP) were evaluated. Contrast sensitivity tests (CS) were done preoperative and 2 months after all sutures had removed. All surgeries were performed under regional anesthesia (retrobulbar anesthesia) by 1 surgeon (B.K.) who was experienced in penetrating and lamellar keratoplasty techniques.

RESULTS

The mean age of the DALK group was 29.67±4.95 (range 18-40) years and the PK group was 28.7±3.53 (range 18-39) years. Preoperatively there was no significant difference in the logMAR UCVA, logMAR BSCVA and IOP between the DALK (1.281±0.56; 0.97±0.85; 12.07±2.12mmHg) and PK (1.34±0.21; 0.98±0.21; 13±2.12mmHg) groups. One-year after surgery there was no significant difference in the mean logMAR UCVA and IOP between the DALK (0.46±0.37; 11.73±2.1mmHg) and PK (0.38±0.21; 12±2.12mmHg) groups. The mean contrast sensitivity was evaluated by CC-100 Topcon LCD at 1.5, 2.52, 4.23, 7.10 and 11.91 cycles per degree (cs/deg) spatial frequencies before and 2 months after the all sutures had removed.

CONCLUSION

All patients with keratoconus in both DALK and PK groups performed good visual function postoperatively. The mean contrast sensitivity increased considerably at all spatial frequencies compared with preoperative levels in the DALK and PK groups. The mean post-operative evaluation of contrast sensitivity measurements was not significantly different between the two groups.

Deep anterior lamellar keratoplasty as an alternative to penetrating keratoplasty a report by the american academy of ophthalmology

OBJECTIVE

To review the published literature on deep anterior lamellar keratoplasty (DALK) to compare DALK with penetrating keratoplasty (PK) for the outcomes of best spectacle-corrected visual acuity (BSCVA), refractive error, immune graft rejection, and graft survival.

METHODS

Searches of the peer-reviewed literature were conducted in the PubMed and the Cochrane Library databases. The searches were limited to citations starting in 1997, and the most recent search was in May 2009. The searches yielded 1024 citations in English-language journals. The abstracts of these articles were reviewed, and 162 articles were selected for possible clinical relevance, of which 55 were determined to be relevant to the assessment objective.

RESULTS

Eleven DALK/PK comparative studies (level II and level III evidence) were identified that compared the results of DALK and PK procedures directly; they included 481 DALK eyes and 501 PK eyes. Of those studies reporting vision and refractive data, there was no significant difference in BSCVA between the 2 groups in 9 of the studies. There was no significant difference in spheroequivalent refraction in 6 of the studies, nor was there a significant difference in postoperative astigmatism in 9 of the studies, although the range of astigmatism was often large for both groups. Endothelial cell density (ECD) stabilized within 6 months after surgery in DALK eyes. Endothelial cell density values were higher in the DALK groups in all studies at study completion, and, in general, the ECD differences between DALK and PK groups were significant at all time points at 6 months or longer after surgery for all of the studies reporting data.

CONCLUSIONS

On the basis of level II evidence in 1 study and level III evidence in 10 studies, DALK is equivalent to PK for the outcome measure of BSCVA, particularly if the surgical technique yields minimal residual host stromal thickness. There is no advantage to DALK for refractive error outcomes. Although improved graft survival in DALK has yet to be demonstrated, postoperative data indicate that DALK is superior to PK for preservation of ECD. Endothelial immune graft rejection cannot occur after DALK, which may simplify long-term management of DALK eyes compared with PK eyes. As an extraocular procedure, DALK has important theoretic safety advantages, and it is a good option for visual rehabilitation of corneal disease in patients whose endothelium is not compromised.

Dissection plane in deep anterior lamellar keratoplasty using the big-bubble technique

PURPOSE

To find the level of dissection in keratoconic corneas undergoing deep anterior lamellar keratoplasty (DALK) using the big-bubble technique.

METHODS

In 3 keratoconic eyes that underwent DALK, the operation was converted into penetrating keratoplasty after complete big-bubble formation because of extensive tear in Descemet's membrane (DM) during stromal excision. The corneal stroma and DM taken from these eyes were submitted for light and transmission electron microscopy.

RESULTS

Both light and transmission electron microscope revealed a thin layer of corneal stroma adhered to DM in all cases. In 2 eyes, the residual stromal thickness was almost constant (6.4 μm and 12.3 μm), whereas it varied from 9.5 μm to 25.8 μm in the other one.

CONCLUSION

Dissection plane in DALK using the big-bubble technique can be within corneal stroma rather than exactly between stroma and DM. Various corneal pathologies as well as different techniques of dissection may have influence on this level.

Deep anterior lamellar keratoplasty versus penetrating keratoplasty for keratoconus: a clinical trial

PURPOSE

To compare deep anterior lamellar keratoplasty (DALK) using the big-bubble technique to penetrating keratoplasty (PK) in patients with keratoconus.

MATERIALS AND METHODS

In this clinical trial, patients with moderate to advanced keratoconus with poor spectacle-corrected visual acuity and intolerant to contact lens wear were enrolled. DALK was performed using the big-bubble technique, and a full-thickness donor cornea without Descemet membrane was sutured to the recipient bed. PK was performed conventionally with a Hessburg-Barron suction trephine. Three types of suturing were used for both groups. Postoperative refractive errors, best-corrected visual acuity (BCVA), contrast sensitivity function (CSF), and higher order aberrations (HOAs) were compared between the study groups.

RESULTS

The study included 81 eyes of 81 patients. Forty-six eyes underwent DALK from which 4 were excluded because of failure to achieve bared Descemet membrane. Thirty-five eyes received PK. Mean patient age was 26.91 ± 7.9 versus 30.89 ± 10.3 years in the DALK and PK groups, respectively (P = 0.06). Mean follow-up period was 22.0 ± 7.9 months in the DALK group and 24.6 ± 3.5 months in the PK group (P = 0.32). Mean postoperative spherical equivalent refractive error was -3.23 ± 3.4 diopters in the DALK group versus -2.22 ± 4.6 diopters in the PK group (P = 0.28), and mean postoperative BCVA was 0.18 ± 0.08 and 0.15 ± 0.10 logarithm of the minimum angle of resolution, respectively (P = 0.12). CSF and total aberrations and HOAs were comparable in the study groups.

CONCLUSIONS

DALK is an effective alternative surgical procedure for patients with keratoconus; the outcomes are comparable to PK in terms of refractive errors, BCVA, CSF, and HOAs.