Deep anterior lamellar keratoplasty vs penetrating keratoplasty for keratoconus: a clinical trial. Cornea. 2010;29:365-371. [PMID: 20168217 DOI: 10.1097/ico.0b013e3181b81b71]

Does lamellar surgery for keratoconus experience the popularity it deserves?

PURPOSE

To analyse developments in surgical treatment for keratoconus (KC) by assessing rates and types of corneal surgery from 2005 to 2010.

METHODS

The Dutch Transplantation Foundation supplied data on all keratoplasty procedures for KC performed from 2005 to 2010 in the Netherlands. Registration was carried out by the eyebank at allocation and by the surgeon at the time of surgery. The type of surgery was categorized as either a penetrating or a lamellar procedure.

RESULTS

Five hundred and seventy-five anonymized records were received, with excellent data completion (99%). Patients undergoing penetrating surgery had on average a lower visual acuity, higher k-readings and were slightly older compared with the lamellar group. A previous corneal hydrops was recorded for 19.1% of patients. Regular penetrating keratoplasty decreased in popularity from 79.7% in 2005 to 43.7% in 2010, due to the increased rate of lamellar surgery (42.5% in 2010) and 'mushroom' penetrating keratoplasty (13.8% in 2010). When hydrops cases were excluded, popularity became equal (47.6% penetrating versus 52.4% lamellar surgery, in 2010).

CONCLUSION

Lamellar surgery is gaining in popularity, although regular penetrating keratoplasty is still the more commonly performed procedure. Only when hydrops cases are excluded do transplant rates become comparable.

Deep anterior lamellar keratoplasty versus penetrating keratoplasty for treating keratoconus

BACKGROUND

Keratoconus is an ectatic (weakening) disease of the cornea, which is the clear surface at the front of the eye. Approximately 10% to 15% of patients diagnosed with keratoconus require corneal transplantation. This may be full-thickness (penetrating) or partial-thickness (lamellar).

OBJECTIVES

To compare visual outcomes after deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty for keratoconus, and to compare additional outcomes relating to factors which may contribute to poor visual outcomes (e.g. astigmatism, graft rejection and failure).

SEARCH METHODS

We searched a number of electronic databases including CENTRAL, PubMed and EMBASE without using any date or language restrictions. We last searched the electronic databases on 31 October 2013. We also handsearched the proceedings of several international ophthalmic conferences.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing the outcomes of DALK and penetrating keratoplasty in the treatment of keratoconus.

DATA COLLECTION AND ANALYSIS

Two authors assessed trial quality and extracted data independently. For dichotomous data (graft failure, rejection, achievement of functional vision) results were expressed as odds ratios (ORs) and 95% confidence intervals (CIs). For continuous data (postoperative best corrected visual acuity (BCVA), uncorrected visual acuity (UCVA), keratometric astigmatism and spherical equivalent) results were expressed as mean differences (MDs) and 95% CIs.

MAIN RESULTS

We identified two completed studies, with a total of 111 participants (n = 30 and n = 81), both conducted in Iran, that met our inclusion criteria. Participants had moderate to severe keratoconus pre-operatively and were randomly allocated to receive either DALK or penetrating keratoplasty. Only one eye of each participant was treated as part of the trials. The smaller study had 12 month follow-up data for all participants. For the larger study, four DALK surgeries had to be abandoned due to technical failure and visual and refractive outcomes were not measured in these participants. Follow-up length for the remaining 77 participants ranged from 6.8 to 36.4 months, with all 77 followed for at least three months post-suture removal. Details of the randomisation procedure were unavailable for the smaller study and so sensitivity analyses were conducted to determine if the results from this study had affected the overall results of the review.Neither of the included studies reported a difference between groups on any of the measures of post-graft visual achievement, keratometric astigmatism or spherical equivalent. A single case of graft failure in a penetrating keratoplasty was reported. No postoperative graft failures were reported in the DALK group of either study.Instances of graft rejection were reported in both groups, in both studies. The majority of these cases were successfully treated with steroids. The data, which related to all cases in each study - given that the four cases that did not go ahead as planned had already technically failed without presence of rejection - showed that rejection was less likely to occur in DALK (odds ratio (OR): 0.33, 95% confidence interval (CI) 0.14 to 0.81, GRADE rating: moderate).Results of the sensitivity analysis indicated that inclusion of the Razmju 2011 study did not bias the results with regards to rejection episodes. While sensitivity analysis showed altered results with regards to failure rates, the data available from the Javadi 2010 study alone had a very wide 95% CI, suggesting an imprecise estimate. Therefore, even after removal of the Razmju 2011 data, it is still difficult to draw conclusions regarding superiority of one technique over another with regards to graft failure.DALK was unable to be completed as planned in four cases and in a further three cases, complications during dissection required further intervention. Other adverse events, of varying severity, were reported in both intervention groups with similar frequency. For both types of surgery, these included postoperative astigmatism, steroid induced ocular hypertension and persistent epithelial defects. In recipients of DALK, one participant had interface neovascularisation (a proliferation of blood vessels where the host and donor cornea come together) and one had wrinkling of Descemet's membrane, the basement membrane separating the corneal stroma from the corneal endothelium. In the penetrating keratoplasty groups, one participant required graft resuturing and one had an atonic pupil, a condition in which the pupil dilates and is non-reactive.Overall, the quality of the evidence was rated as very low to moderate, with methodological limitations, incomplete data analysis and imprecision of findings, as well as high risk of bias in several areas for both studies.

AUTHORS' CONCLUSIONS

We found no evidence to support a difference in outcomes with regards to BCVA at three months post-graft or at any of the other time points analysed (GRADE rating: very low). We also found no evidence of a difference in outcomes with regards to graft survival, final UCVA or keratometric outcomes. We found some evidence that rejection is more likely to occur following penetrating keratoplasty than DALK (GRADE rating: moderate). The small number of studies included in the review and methodological issues relating to the two, mean that the overall quality of the evidence in this review is low. There is currently insufficient evidence to determine which technique may offer better overall outcomes - final visual acuity and time to attain this, keratometric stabilisation, risk of rejection or failure, or both, and risk of other adverse events - for patients with keratoconus. Large randomised trials comparing the outcomes of penetrating keratoplasty and DALK in the treatment of keratoconus are needed.

Deep anterior lamellar keratoplasty with a manual spatula: anatomical and functional results

Objective:

Evaluate the anatomical, refractive, and functional results of an innovative technique of deep anterior lamellar keratoplasty with a manual spatula.

Materials and Methods:

We evaluated the results and examinations of 16 eyes from 14 patients who underwent deep anterior lamellar keratoplasty using the technique described by Ferrara. Residual bed thickness after keratoplasty was evaluated postoperatively using Visante. The measurement was performed using a technique similar to that used to measure flap thickness after laser in situ keratomileusis refractive surgery. The measurements were performed at the center of the cornea in an area comprising the central 3-mm in the 45° and 135° meridians.

Results:

Best-corrected visual acuity was 0.34 ± 0.18 LogMar (0.09 to 0.60 LogMar), the spherical equivalent was -4.31 ± 3.38 D (+0.25 to -9.50 diopters), and keratometry was 45.75 ± 2.77 D (41.11 to 52.48 diopters) postoperatively. Corneal astigmatism was 3.19 ± 2.78 D (0.18 to 11.81 diopters). Residual stromal bed thickness measured by optical coherence tomography showed values of 67.1 ± 24.3 μm (30 to 109 μm). The statistical correlation by Spearman's test between the best-corrected visual acuity and the residual stromal bed thickness was 0.11 (P = 0.67).

Conclusion:

Deep anterior lamellar keratoplasty, in which manual dissection was performed using an instrument similar to that used to implant corneal rings, provided good visual and anatomical results.

Long-term outcomes of deep anterior lamellar keratoplasty versus penetrating keratoplasty in Australian keratoconus patients

PURPOSE

The aim of this study is to compare long-term visual and surgical outcomes after performing deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) for keratoconus.

METHODS

This is a retrospective review of 73 consecutive patients with keratoconus, managed with DALK or PK, between 2000 and 2010, by a single surgeon. Data were collected on baseline parameters, best-corrected visual acuity (BCVA) in logarithm of the mean angle of resolution (logMAR), subjective refraction, graft survival, and complications.

RESULTS

Thirty-one (42.5%) eyes underwent a DALK, and 42 (57.5%) eyes underwent a PK. All PK-operated and 29 out of 31 (93.5%) DALK-operated eyes remained clear at the last review. Postoperative complications were significantly more frequent after PK (57.1%) than after DALK (26.5%; P = 0.0197). The mean BCVA was not significantly different for DALK (0.14 logMAR, SD 0.2) versus PK (0.05 logMAR, SD 0.11); however, eyes that underwent PK were more likely to achieve a BCVA of 0.0 logMAR (P = 0.0029). Subjective refraction and method of visual correction (spectacles or contact lenses) were similar for each group.

CONCLUSIONS

DALK-operated patients in this study showed similar graft survival, fewer postoperative complications, and equivalent refractive outcomes. No significant difference in the mean BCVA was noted between DALK and PK cases.

Donor Descemet-off versus Descemet-on deep anterior lamellar keratoplasty: a confocal scan study

PURPOSE

To compare confocal features of grafts following deep anterior lamellar keratoplasty (DALK) using a donor without Descemet membrane (DM) versus a full-thickness donor with intact DM and endothelium.

METHODS

This retrospective comparative study examined 45 eyes from patients with keratoconus who underwent DALK using the big-bubble technique. The big-bubble technique yielded a bared DM in all keratoconic eyes. Twenty-seven eyes received tissue from a donor without DM (group 1), while 18 received tissue from a full-thickness donor with an intact DM and endothelium (group 2). A group of normal eyes (n = 28, group 3) served as controls. Confocal microscopy was used to determine keratocyte density, explore the donor-recipient interface including clarity and reflectivity, evaluate endothelial cell density and morphology, as well as measure interface depth and central corneal thickness.

RESULTS

Mean follow-up duration was 20.2 ± 8.6 months and 29.6 ± 17.0 months in groups 1 and 2, respectively (p = 0.13). Confocal scan demonstrated that the keratocyte profiles and distribution were more similar to normal corneas in group 2. Significantly more severe interface haziness was observed when donor DM and endothelium was retained (mean interface reflectivity value of 102.7 ± 22.1 versus 161.7 ± 30.0 light reflectance units in groups 1 and 2, respectively, p<0.001).

CONCLUSIONS

Graft cellular profiles and healing response at the donor-recipient interface can be profoundly affected depending on whether donor DM and endothelium is removed or retained.

A comparison of lamellar and penetrating keratoplasty outcomes: a registry study

OBJECTIVES

To investigate changing patterns of practice of keratoplasty in Australia, graft survival, visual outcomes, the influence of experience, and the surgeon learning curve for endothelial keratoplasty.

DESIGN

Observational, prospective cohort study.

PARTICIPANTS

From a long-standing national corneal transplantation register, 13 920 penetrating keratoplasties, 858 deep anterior lamellar keratoplasties (DALKs), and 2287 endokeratoplasties performed between January 1996 and February 2013 were identified.

METHODS

Kaplan-Meier functions were used to assess graft survival and surgeon experience, the Pearson chi-square test was used to compare visual acuities, and linear regression was used to examine learning curves.

MAIN OUTCOME MEASURES

Graft survival.

RESULTS

The total number of corneal grafts performed annually is increasing steadily. More DALKs but fewer penetrating grafts are being performed for keratoconus, and more endokeratoplasties but fewer penetrating grafts are being performed for Fuchs' dystrophy and pseudophakic bullous keratopathy. In 2012, 1482 grafts were performed, compared with 955 in 2002, translating to a requirement for 264 extra corneal donors across the country in 2012. Comparing penetrating grafts and DALKs performed for keratoconus over the same era, both graft survival (P <0.001) and visual outcomes (P <0.001) were significantly better for penetrating grafts. Survival of endokeratoplasties performed for Fuchs' dystrophy or pseudophakic bullous keratopathy was poorer than survival of penetrating grafts for the same indications over the same era (P <0.001). Visual outcomes were significantly better for penetrating grafts than for endokeratoplasties performed for Fuchs' dystrophy (P <0.001), but endokeratoplasties achieved better visual outcomes than penetrating grafts for pseudophakic bullous keratopathy (P <0.001). Experienced surgeons (>100 registered keratoplasties) achieved significantly better survival of endokeratoplasties (P <0.001) than surgeons who had performed fewer grafts (<100 registered keratoplasties). In the hands of experienced, high-volume surgeons, endokeratoplasty failures occurred even after 100 grafts had been performed.

CONCLUSIONS

More corneal transplants, especially DALKs and endokeratoplasties, are being performed in Australia than ever before. Survival of DALKs and endokeratoplasties is worse than the survival of penetrating grafts performed for the same indications over the same timeframe. Many endokeratoplasties fail early, but the evidence for a surgeon learning curve is unconvincing.

Donor tissue selection for anterior lamellar keratoplasty

PURPOSE

To assess the influence of donor characteristics on the outcome of anterior lamellar keratoplasty (ALK) and to evaluate whether corneal donor tissue considered unsuitable for penetrating or posterior lamellar keratoplasty due to poor endothelial condition may be safely used for ALK.

METHODS

Institutional setting. One hundred sixty-six consecutive ALK (166 patients) performed for optical indication in eyes with corneal diseases not involving the corneal endothelium. The main outcome measures were graft survival, early (0-12 months postoperatively) and late (after 12 months) annual endothelial cell loss, and postoperative logarithm of the minimum angle of resolution visual acuity.

RESULTS

The average and extreme values of donor tissue characteristics were: donor age, 70.6 years (range, 28-88 years); organ culture time, 20.9 days (range, 12-35 days); graft endothelial cell density before transplantation, 2047 cells per millimeters (range, 100-3300 cells/mm2); and deswelling time, 2.0 days (range, 1-4 days). The average follow-up time of patients was 48.1 ± 24.8 months (mean ± SD). None of the donor characteristics significantly influenced graft survival or postoperative endothelial cell loss (early and late phase). Donor age >80 years was associated with lower postoperative visual acuity at all postoperative points in time (P < 0.05). At 3 years, the mean logarithm of the minimum angle of resolution visual acuity was 0.44 (20/55) for grafts from donors older than 80 years and 0.25 (20/35) for younger donors. This result was shown to be significant both in univariate and in multivariate analysis.

CONCLUSIONS

Grafts from elderly donors should be discarded before ALK. Conversely, donor tissue with poor endothelial cell density (<2000 cells/mm2) is suitable for ALK.

Keratoconus: current perspectives

Keratoconus is characterized by progressive corneal protrusion and thinning, leading to irregular astigmatism and impairment in visual function. The etiology and pathogenesis of the condition are not fully understood. However, significant strides have been made in early clinical detection of the disease, as well as towards providing optimal optical and surgical correction for improving the quality of vision in affected patients. The past two decades, in particular, have seen exciting new developments promising to alter the natural history of keratoconus in a favorable way for the first time. This comprehensive review focuses on analyzing the role of advanced imaging techniques in the diagnosis and treatment of keratoconus and evaluating the evidence supporting or refuting the efficacy of therapeutic advances for keratoconus, such as newer contact lens designs, collagen crosslinking, deep anterior lamellar keratoplasty, intracorneal ring segments, photorefractive keratectomy, and phakic intraocular lenses.

Photorefractive keratectomy in patients with mild to moderate stable keratoconus: a five-year prospective follow-up study

Background

The purpose of this study was to evaluate the visual outcome of photorefractive keratectomy (PRK) in patients with mild to moderate stable keratoconus and to assess the risk of progression of the disease after the excimer laser procedure.

Methods

In this prospective study, carried out at the Clemenceau Medical Center, an affiliate of Johns Hopkins International, in Beirut, Lebanon, 119 eyes from 72 patients with grade 1–2 keratoconus (Amsler–Krumeich classification) underwent PRK. Forty-seven patients had both eyes treated and 25 patients had one eye treated. The procedure was done using the Wavelight Eye Q Excimer laser. Uncorrected and best-corrected visual acuity, corneal topography, and pachymetry were assessed before the procedure and 3, 6, 12, 36, and 60 months after the procedure.

Results

Mean uncorrected visual acuity showed a statistically significant improvement (P < 0.05) at one, 3, and 5 years follow-up. One hundred and seventeen eyes (98.3%) showed no progression while two eyes (1.7%) showed progression of the disease at 5 years follow-up, as documented by corneal topography and pachymetry. These two eyes were treated with corneal collagen crosslinking.

Conclusion

PRK in mild to moderate keratoconus is a safe and effective procedure for improving uncorrected vision in patients with mild refractive errors. However, close follow-up of patients is needed to detect any progression of the disease. Longer follow-up is needed to assess the overall effect of this procedure on progression of the disease.

Lamellar keratoplasty: a literature review

The concept of lamellar keratoplasty (LK) is not new. However, newer forms of lamellar keratoplasty techniques have emerged in the last decade or so revolving around the concept of targeted replacement of diseased corneal layers. These include anterior lamellar keratoplasty (ALK) techniques that aim to selectively replace diseased corneal stroma and endothelial keratoplasty techniques aiming to replaced damaged endothelium in endothelial disorders. Recent improvements in surgical instruments and introduction of new techniques as well as inherent advantages such as preservation of globe integrity and decreased graft rejection have resulted in the reintroduction of LK as an acceptable alternative to conventional PK. In this review, indications, benefits, limitations, and outcomes of various anterior and posterior lamellar keratoplasty techniques are discussed.

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.

Comparison of clinical outcomes of same-size grafting between deep anterior lamellar keratoplasty and penetrating keratoplasty for keratoconus

Purpose

To compare the clinical outcomes between deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PKP) with same-size grafts in patients with keratoconus.

Methods

Medical records of 16 eyes from 15 patients treated from June 2005 through April 2011 were retrospectively reviewed. Patients with contact lens intolerance or who were poor candidates for contact lens fitting due to advanced cone underwent keratoplasty. The transplantations consisted of 11 DALK and 5 PKP with same-size grafting for keratoconus. Best-corrected visual acuity (BCVA), refractive error, corneal topographic profiling, and clinical course were compared between DALK and PKP groups.

Results

The follow-up period was 30 ± 17 months in the DALK group and 45 ± 20 months in the PKP group (p = 0.145). At final follow-up, the DALK and PKP groups achieved a BCVA (logarithm of the minimum angle of resolution) of 0.34 and 0.52, respectively (p = 0.980). Postoperative refractive error and mean simulated keratometric index showed myopic astigmatism in both groups without any statistical difference. Corneal irregularity index measured at 5 mm in the DALK group was less than that of the PKP group at 1-year follow-up (p = 0.021); however, at final follow-up, there was no longer a statistically significant difference. Endothelial cell counts were lower in the PKP group than in the DALK group at final follow-up (p = 0.021).

Conclusions

The optical outcomes of DALK with same-size grafts for keratoconus are comparable to those of PKP. Endothelial cell counts are more stable in DALK compared to PKP.

Deep anterior lamellar keratoplasty versus penetrating keratoplasty for macular corneal dystrophy: a randomized trial

PURPOSE

To compare outcomes of big-bubble deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) for macular corneal dystrophy.

DESIGN

Prospective, randomized, interventional case series.

METHODS

setting: Single hospital. patients: Eighty-two eyes of 54 patients requiring keratoplasty for the treatment of macular corneal dystrophy without endothelial involvement were included. main outcome measures: Operative complications, uncorrected visual acuity, best-corrected visual acuity, contrast sensitivity function, higher-order aberrations, and endothelial cell density were evaluated.

RESULTS

The DALK and PK group consisted of 35 and 41 eyes, respectively. Best-corrected visual acuity after surgery was 20/40 or better 68.5% and 70.7% of the eyes in the DALK and PK groups, respectively (P > .05). No statistically significant differences between groups were found in contrast sensitivity function with and without glare for any spatial frequency (P > .05). Significantly higher levels of higher-order aberrations were found in the DALK group (P < .01). In both groups, a progressive and statistically significant reduction in endothelial cell density was found (P < .01). At the last follow-up, the mean endothelial cell loss was 18.1% and 26.9% in DALK and PK groups, respectively (P = .03). Graft rejection episodes were seen in 5 eyes (12.1%) in the PK group, and regrafting was necessary in 3 eyes (7.3%). Recurrence of the disease was documented in 5.7% and 4.8% of the eyes in the DALK and PK groups, respectively.

CONCLUSIONS

Deep anterior lamellar keratoplasty with the big-bubble technique provided comparable visual and optical results as PK and resulted in less endothelial damage, as well as eliminating endothelial rejection in macular corneal dystrophy. Deep anterior lamellar keratoplasty surgery is a viable option for macular corneal dystrophy without endothelial involvement.

Deep anterior lamellar keratoplasty in children

PURPOSE

To evaluate the outcomes of deep anterior lamellar keratoplasty (DALK) in children.

DESIGN

Retrospective interventional case series.

METHODS

setting: Institutional, L.V. Prasad Eye Institute, a tertiary care center in south India. study population and intervention: All children less than 16 years of age undergoing DALK from January 2003 to January 2011. main outcome measure: Visual outcome and complications.

RESULTS

Twenty-six eyes of 26 children (13 male and 13 female) with a mean age of 7.82 ± 4.64 years underwent DALK for keratoconus (8), microbial keratitis (6), corneal scar (6), corneal keloid (3), chemical injury with limbal stem cell deficiency (2), and dermoid (1). Big bubble was achieved in 5 eyes, while manual dissection was done in 21. Follow-up ranged from 1 week to 7.3 years. Seventeen patients with a minimal follow-up of 6 months were evaluated for visual outcomes. Final vision varied from counting fingers to 20/20 (mean sphere 2.32 diopters, mean cylinder -2.5 diopters). Complications encountered were suture-related graft infiltrate (3), graft dehiscence (3), and Descemet membrane detachment (2).

CONCLUSIONS

DALK is a feasible option in children with stromal corneal pathology. It offers advantages in the form of lower risk of graft rejection. However, the risk of complications such as suture-related infections and graft dehiscence persists even in these cases.

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.

Anterior segment optical coherence tomography-guided big-bubble technique

PURPOSE

To evaluate the feasibility of intraoperative anterior segment (AS) optical coherence tomography (OCT) for quantification of the corneal depth reached with the dissecting cannula used for deep anterior lamellar keratoplasty, as well as its correlation with the success rate of big-bubble formation.

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

One hundred consecutive keratoconus patients.

INTERVENTION

Deep anterior lamellar keratoplasty was performed using the big-bubble technique. During surgery, the cannula used for pneumatic dissection was inserted into the peripheral stroma and advanced as deep and far toward the center as believed adequate by the surgeon. Then, after retracting the cannula, AS OCT was performed. The cannula was placed back in position and creation of the big bubble was attempted.

MAIN OUTCOME MEASURES

Stromal depth reached with the cannula tip, success rate in achieving big-bubble formation, and complication rate.

RESULTS

Bubble formation was obtained in 70 of 100 eyes (70%). In all remaining eyes, the procedure was completed by manual deep lamellar dissection. The average depth reached by the cannula tip was 104.3±34.1 μm from the internal corneal surface; the mean value recorded in cases of successful big-bubble formation (90.4±27.7 μm) was statistically lower than that measured in failed procedures (136.7±24.2 μm). In 1 case, corneal perforation occurred during the insertion of the cannula and required conversion to penetrating keratoplasty (PK). In 8 eyes, small microperforations occurred during stromal excision but could be managed conservatively, avoiding conversion to PK. In 2 advanced cones, an incomplete bubble formation was obtained, necessitating manual peripheral stromal removal.

CONCLUSIONS

Successful big-bubble formation can be anticipated if pneumatic dissection is attempted at a sufficiently deep level. Although an ideal depth could not be defined, AS OCT allows objective evaluation of the depth reached by the cannula tip used for pneumatic dissection. The AS OCT findings may confirm the decision to proceed with air injection. It is possible that cannula repositioning based on the AS OCT depth may improve the success rate for big-bubble formation.

Pachymetry-guided intrastromal air injection ("pachy-bubble") for deep anterior lamellar keratoplasty

To evaluate an innovative technique for intrastromal air injection to achieve deep anterior lamellar keratoplasty (DALK) with bare Descemet membrane (DM). Thirty-four eyes with anterior corneal pathology, including 27 with keratoconus, underwent DALK. After 400 μm trephination with a suction trephine, ultrasound pachymetry was performed 0.8 mm internally from the trephination groove in the 11 to 1 o'clock position. In this area, a 2-mm incision was created, parallel to the groove, with a micrometer diamond knife calibrated to 90% depth of the thinnest measurement. A cannula was inserted through the incision and 0.5 mL of air was injected to dissect the DM from the stroma. After peripheral paracentesis, anterior keratectomy was carried out to bare the DM. A 0.25-mm oversized graft was sutured in place. Overall, 94.1% of eyes achieved DALK. Bare DM was achieved in 30 eyes, and a pre-DM dissection was performed in 2 eyes. Air injection was successful in detaching the DM (achieving the big bubble) in 88.2% of the eyes. In keratoconus eyes, the rate was 88.9%. All cases but one required a single air injection to achieve DM detachment. Microperforations occurred in 5 cases: 3 during manual layer-by-layer dissection after air injection failed to detach the DM, 1 during removal of the residual stroma after big-bubble formation, and 1 during the diamond knife incision. Two cases (5.9%) were converted to penetrating keratoplasty because of macroperforations. The technique was reproducible, safe, and highly effective in promoting DALK with bare DM.

Anwar versus Melles deep anterior lamellar keratoplasty for keratoconus: a prospective randomized clinical trial

PURPOSE

To compare the outcomes of 2 techniques (Anwar vs. Melles) of deep anterior lamellar keratoplasty (DALK) in patients with keratoconus.

DESIGN

Randomized, double-blind clinical trial.

PARTICIPANTS

Fifty-seven eyes of 57 patients 20 to 35 years of age were enrolled.

METHODS

Patients with clinical diagnosis of keratoconus who were contact lens intolerant and whose corrected distance visual acuity (CDVA) was less than 20/80 were enrolled. Eligible eyes were allocated randomly into 2 groups: the Anwar technique (23 eyes) or the Melles technique (25 eyes).

MAIN OUTCOME MEASURES

The primary outcome measure was CDVA. Secondary outcomes were spherical equivalent, contrast sensitivity, corneal aberrations, corneal biomechanical properties, endothelial cell count, and central corneal thickness. All outcomes were compared 15 months after surgery.

RESULTS

The CDVA was 0.17 ± 0.09 logarithm of the minimum angle of resolution (logMAR) units and 0.18 ± 0.11 logMAR units in the Anwar and Melles groups, respectively (P = 0.803). Spherical equivalent was -1.82 ± 2.7 diopters (D) and -2.69 ± 3.94 D in the Anwar and Melles groups, respectively (P = 0.155). Overall, the difference in photopic and mesopic contrast sensitivity function between the 2 groups was statistically significant (P<0.05). There was no significant difference between 2 groups in total and higher-order aberrations up to the fifth order (P>0.05 for all parameters). Corneal hysteresis was not significantly different between the 2 groups (9.9 ± 0.8 vs. 9.9 ± 0.6; P = 0.606). The corneal resistance factor was 10.02 ± 0.8 and 10.13 ± 0.76 (P = 0.509). There was no significant difference in percentage of endothelial cell loss between the 2 groups (1 ± 2% vs. 1 ± 3% in the Anwar and Melles groups, respectively; P = 0.869). Mean central corneal thickness was 525.56 ± 47.87 μm versus 504.64 ± 54.20 μm in the Anwar and Melles groups, respectively (P = 0.155).

CONCLUSIONS

The Anwar and Melles techniques of DALK have comparable visual acuity and refractive outcomes, aberrometric profiles, biomechanical properties, corneal thicknesses, and endothelial cell densities. However, patients who underwent the Anwar technique showed better contrast sensitivity.

Enlarging the big-bubble during deep anterior lamellar keratoplasty

PURPOSE

During big-bubble deep anterior lamellar keratoplasty, a bubble that is not large enough can be formed. Further air injection can result in the rupture of the posterior lamella, necessitating conversion to penetrating keratoplasty. We describe some techniques to safely enlarge the big-bubble in such a circumstance.

METHODS

In cases in which a white-margin bubble forms that has extended to the trephination margin, the bubble is collapsed and the margins are extended by blunt dissection. For cases of an undersized clear-margin bubble, the bubble is enlarged by gentle injection of a cohesive ophthalmic viscosurgical device into the bubble cavity.

RESULTS

Using these techniques, big-bubbles were safely extended beyond the trephination margin for both white- and clear-margin bubbles.

CONCLUSIONS

An undersized big-bubble can safely be extended using blunt dissection for white-margin bubbles and ophthalmic viscosurgical device injection for clear-margin bubbles.

Visual performance with wave aberration correction after penetrating, deep anterior lamellar, or endothelial keratoplasty

PURPOSE

To investigate the contribution ocular aberrations have on visual performance by quantifying improvements in best-corrected visual acuity (VA) and contrast sensitivity (CS) obtained with higher-order aberration (HOA) correction after penetrating (PK), deep anterior lamellar (DALK), or Descemet's stripping automated endothelial keratoplasty (DSAEK).

METHODS

Sixteen eyes were evaluated from 14 subjects who underwent PK (n = 5), DALK (n = 6), or DSAEK (n = 5) greater than 1 year prior to study enrollment. Ocular aberrations were measured and an adaptive optics system was used to correct ocular lower-order aberration (LOA) and HOA. VA and CS were measured for each subject with LOA or full-aberration correction. CS was measured at each of three spatial frequencies: 4, 8, and 12 cycles/deg.

RESULTS

All keratoplasty groups had more aberration than that of a normal myopic population and experienced significant VA gains with full-aberration correction (P < 0.0013). PK subjects had better VA than that of DSAEK subjects with LOA correction (logMAR VA 0.03 ± 0.05 vs. 0.25 ± 0.05; P = 0.0870). After HOA correction this trend persisted (P = 0.1734). DSAEK subjects also experienced less VA benefit from full-aberration correction than that of PK and DALK subjects. All keratoplasty groups demonstrated similar CS benefits from full-aberration correction despite differing higher-order root-mean-square magnitudes.

CONCLUSIONS

PK eyes had better logMAR VA than that of DSAEK eyes with LOA correction, whereas DALK eyes performed intermediate between the two. When full correction was applied, the same trend persisted. The findings suggest that factors other than aberration contribute to decrements in VA with DSAEK compared with PK.

Deep anterior lamellar keratoplasty: indications, surgical techniques and complications

The concept of lamellar keratoplasty (LK) is not new. However, it had been abandoned and largely replaced by the time-honored technique of penetrating keratoplasty (PK) because LK is technically demanding, time consuming and gives suboptimal visual outcomes due to interface irregularity arising from manual lamellar dissection. Recent improvements in surgical instruments and introduction of new techniques of maximum depth of corneal dissection as well as inherent advantages such as preservation of globe integrity and elimination of endothelial graft rejection have resulted in a re-introduction of LK as an acceptable alternative to conventional PK. This review article describes the indications, different techniques, clinical outcomes and complications of deep anterior LK.

Penetrating keratoplasty versus deep anterior lamellar keratoplasty for the treatment of keratoconus

PURPOSE

To compare the outcome of penetrating keratoplasty (PKP) and deep anterior lamellar keratoplasty (DALK) in the surgical management of keratoconus (KC).

PATIENT AND METHODS

A retrospective review was conducted of the medical records of all patients treated with PKP or DALK for KC at University of Iowa Hospitals and Clinics from January 1, 2000, to December 31, 2006. The main outcome measures were visual outcome, graft survival, and complications. Cases with a minimum follow-up of 6 months were included in the statistical analysis.

RESULTS

Of 41 eyes that met the inclusion criteria, 30 eyes were treated with PKP and 11 eyes were treated with DALK. The mean follow-up was almost identical for eyes treated with PKP or DALK (21.9 vs. 22.5 months, respectively). At the most recent examination, the mean best spectacle-corrected visual acuity (BSCVA) was 20/28 for the PKP group and 20/29 for the DALK group (P = 0.77). The percentage of eyes that achieved BSCVA of 20/25 or better was higher in the PKP group than in the DALK group (77.3 vs. 45.5%, respectively), but this difference was not statistically significant (P = 0.72). Endothelial rejection occurred in 4 (13.3%) eyes after PKP. Visually significant interface haze occurred in the early postoperative course in 2 (18.2%) eyes after DALK. No cases of late-onset endothelial failure were found in either group.

CONCLUSION

Treatment of KC with PKP or DALK is associated with similar visual outcomes, graft survival, and prevalence of sight-threatening complications.