Lamellar keratoplasty: a literature review

Intrastromal Keratoplasty Using Biosynthetic Corneas Versus Human Donor Corneas in Advanced Keratoconus

PURPOSE

The objective of this study was to compare the clinical outcomes of intrastromal keratoplasty using biosynthetic corneas with human donor corneas in cases of advanced keratoconus.

METHODS

A prospective nonblinded randomized controlled study was conducted at a tertiary eye center in India. Treatment-naïve patients with advanced keratoconus aged 18 years or older were included. Twenty eyes were randomized into 2 groups-group 1 (human donor corneal lenticule, n = 10) and group 2 (biosynthetic corneal lenticule, n = 10). Efficacy analyses included an increase in the thinnest pachymetry and a decrease in the maximum keratometry (Kmax). Safety analyses included any adverse events in the postoperative period.

RESULTS

At 6 months postoperatively, the rise in the thinnest pachymetry in group 1 was 346.8 ± 40.82 to 486.7 ± 15.7 μm (P < 0.001) and in group 2 was 366.2 ± 31.3 to 548.3 ± 59.1 μm (P < 0.001). The biosynthetic group exhibited a significant increase in the thinnest pachymetry (P = 0.005). However, both groups showed a similar decrease in Kmax (71.06 ± 7.95 to 63.3 ± 3.74 D in group 1 and 69.13 ± 8.54 to 61.5 ± 6.2 D in group 2; P = 0.44). No adverse events were seen at 6 months of follow-up.

CONCLUSION

Femtosecond-assisted intrastromal implantation of biosynthetic corneas is a safe and effective alternative to human donor corneas in cases of advanced keratoconus.

Classic lattice corneal dystrophy: a brief review and summary of treatment modalities

PURPOSE

To provide a brief summary and comparison of the most recent literature on available and theorized treatment modalities for classic lattice corneal dystrophy (LCD). This paper aims to support practitioners in their management of this disease.

METHODS

A search was carried out on available literature through PubMed and Google Scholar of English language articles up to January 2023 that relate to the treatment of LCD. Due to scarcity of literature regarding specific novel therapies for LCD, results from other corneal pathologies (granular corneal dystrophy, corneal scarring) are sometimes included for contrast, which is clearly denoted.

RESULTS

LCD is a slowly progressive disease that leads to recurrent epithelial corneal erosions, stromal haze, corneal opacification, substantial discomfort, and visual impairment. Due to its autosomal-dominant inheritance pattern, this disease can persist throughout ancestral lines and requires consistent treatment and follow-up. An optimal management plan is necessary to (1) prolong years of life with best achievable visual acuity; (2) treat painful recurrent corneal erosions as they occur; (3) ensure proper follow-up throughout the life of a patient, as well as monitor at-risk offspring; and (4) monitor efficacy of treatment.

CONCLUSIONS

This paper addresses (1) treatment for early disease including corneal epithelial debridement, photo therapeutic keratectomy (PTK), femtosecond laser-assisted lamellar keratectomy (FLK), and others; (2) treatment for late disease including full thickness keratoplasties and anterior lamellar keratoplasties; and (3) potential future treatment considerations including a wide variety of topical/systemic, genetic, and regenerative approaches.

Correlation Between the Cost and Safety of Corneal Graft Types

Background Corneal diseases are the fourth most common cause of blindness worldwide. In the majority of these diseases, vision reduction is reversible and can be restored to a large extent by replacing the cornea through specific surgery and, in particular, transplantation. In Greece, due to a lack of organized eye banks as well as donors, the grafts intended for corneal transplantation usually come from eye banks abroad. This study focuses on the dynamics of cost versus value in the decision-making process for the procurement of corneal grafts, ultimately investigating the safety that the procured grafts provide to patients. Methodology A total of 267 patients with severe vision problems who underwent 301 corneal and amniotic membrane transplants from years 2020 to 2023 at the Transplant Unit of the Athens General Hospital "Georgios Gennimatas" were included in this study. All patients who were deemed appropriate to undergo corneal transplant operations, the diagnosis that led to the specific surgery, and other relevant data were recorded and evaluated. Results There was no significant difference in the ratio between males and females (51.3% male and 48.7% female). The mean age of the patients was 66.5 years (SD = 13.7 years). Graft problems were faced by 13.9% of the patients, with the amniotic membrane by 1.5% (in the total number of surgical operations) and both eyes by 4.5% of patients. The majority of the patients had undergone only one surgery (88.8%). Reoperation was needed in 14% of the cases, and 7.6% of the cases were surgeries that occurred due to graft rejection or non-functioning grafts from surgeries performed at another hospital or clinic. In the majority of surgeries (60.8%), a Descemet's stripping automated endothelial keratoplasty graft was used. The mean cost was 3,167 euro (SD = 960.3 euro). Furthermore, in 35.8% of the surgeries, the graft was preserved with amphotericin. Conclusions The present study draws useful conclusions about the effectiveness of surgical interventions through the correlation of cost and safety of the grafts that are approved and finally used in corneal transplants, as well as the submission of proposals to improve the procedures and lead to patient benefits.

[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.

Corneal transplantation: A walk to vision

Corneal diseases are a major cause of blindness in the world. Corneal transplantation has been a cornerstone in the management of several of these advanced pathologies. This article discusses the evolution of corneal transplantation over a century, its indications, complications and briefly the various surgical techniques. Such tremendous technical improvisations from total corneal transplantation to lamellar keratoplasties have generated significant interest in the ophthalmic world and garnered momentum to the fight against blindness. Armed Forces Medical Services are also in vogue more than ever in this forward surge.

"Groove and Peel" Deep Anterior Lamellar Keratoplasty: How Deep Can You Go?

PURPOSE

The aim of the current research was to measure the thickness of the residual central corneal bed after performing the manual "Groove and Peel" deep anterior lamellar keratoplasty (GP-DALK) technique on human cadaveric eyes.

METHODS

The manual GP-DALK technique was performed on 6 human cadaver eyes by an experienced corneal surgeon. After surgery, the eye globes were fixed in 10% buffered formalin and embedded in paraffin. For each eye, 4-μm-thick hematoxylin and eosin sections involving the pupillary axis were obtained and examined. Using an image-processing software, 2 observers measured the corneal thickness of the residual central corneal bed and the peripheral corneal rims.

RESULTS

The overall mean central corneal bed thickness was 35.5 ± 12.9 μm, whereas the mean right and left peripheral rim thicknesses were 993.0 ± 141.1 and 989.3 ± 147.1 μm, respectively ( P = 0.0006 ). In most corneas, the level of dissection reached almost to the pre-Descemetic collagen (Dua) layer.

CONCLUSIONS

The GP-DALK technique is effective in removing most of the corneal stroma and may be non-inferior to "big-bubble" deep anterior lamellar keratoplasty in some cases.

Visual Outcomes of Microkeratome-Assisted Anterior Lamellar Keratoplasty in Keratoconus: 5-Year Results

Purpose

To report 5-year results of microkeratome-assisted anterior lamellar keratoplasty (MK-ALK) in cases of keratoconus.

Methods

Patients with advanced keratoconus and the thinnest corneal location 300 μ or more were recruited. A Carriazo–Barraquer microkeratome was used to remove a 200-μ cap from the recipient cornea, and to prepare a 300-μ anterior stromal graft from a donor cornea. A full-thickness crescentic incision was made in the posterior stromal recipient bed using a 6.5-mm suction trephine. The donor was sutured to the recipient bed using interrupted nylon sutures. The minimum follow-up was five years.

Results

Twelve eyes of 12 patients were included. The mean age was 26 ± 8 years. None of the patients required conversion to penetrating keratoplasty. Mean logMAR uncorrected and best spectacle-corrected visual acuity, respectively, improved from 1.56 ± 0.24 and 1.18 ± 0.32 preoperatively, to 0.63 ± 0.38 and 0.18 ± 0.12, five years after surgery (P=0.001for both). There was also a statistically significant reduction of mean manifest spherical equivalent, refractive cylinder, and mean keratometry readings. Posterior stromal striations occurred in all patients immediately after surgery but resolved after a maximum of 3 months. At five-years, anterior segment optical coherence tomography revealed a clear interface in all cases and a mean graft thickness of 328 ± 27 μ.

Conclusion

MK-ALK is a safe and effective procedure for advanced keratoconus. Where feasible, it may be the best choice for patients at high risk of poor outcomes with penetrating keratoplasty, such as young patients with atopic keratoconjunctivitis or Down's syndrome.

Evolution of corneal transplantation techniques and their indications in a French corneal transplant unit in 2000–2020

Purpose

This retrospective cohort study assessed the evolution of corneal transplantation and its indications in the last 21 years (2000–2020) in a specialized ophthalmology department in a tertiary referral center in France.

Methods

The surgical techniques and indications, patient age and sex, and postoperative best-corrected visual acuity (BCVA) 6 months after keratoplasty were extracted.

Results

In total, 1042 eyes underwent keratoplasty in 2000–2020. Annual numbers of corneal transplantations increased by 2.2-fold. Penetrating keratoplasty (PKP) was the sole technique for the first 11 years. Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK) were introduced in 2011 and 2014, respectively. Cases of both quickly increased, accounting for 28% and 41% of cases in 2015–2020, respectively. Eventually, DSAEK and DMEK were respectively used for most pseudophakic bullous keratopathy (PBK) and all Fuchs endothelial cell dystrophy (FECD) cases. PKP cases declined to 27%. Deep anterior lamellar keratoplasty (DALK) was rare (3% of all cases). These changes associated with rises in PBK and particularly FECD cases, and a strong decline in keratoconus, causing FECD, PBK, and keratoconus to move from being the 4^th, 1^st, and 3^rd most common indications to the 1^st, 2^nd, and 6^th, respectively. On average, BCVA improved by 0.1–0.3 logMAR. Patient age dropped steadily over time. Female predominance was observed.

Conclusions

The invention of DSAEK and then DMEK precipitated an enormous change in clinical practice and a large expansion of keratoplasty to new indications. This study confirms and extends previous findings in other countries.

Ophthalmological aspects of mustard gas poisoning (focus on management)

Background

Amongst the chemical warfare agents, blistering (vesicant) agents can be significant materials. The most important agent in this group is sulfur mustard (mustard gas) which is known as "King of chemical warfare (CW) agents ". Exposure to this agent, seriously causes damages in several organs, such as the eyes. This article reviews the ophthalmological aspects of sulfur mustard with reference of its management.

Methods

A wide-ranging search in PubMed databases, Thomson Reuters and Scopus was done and different aspects of chemical properties of sulfur mustard, its mechanism of action and effects on eyes, clinical finding, diagnostic evaluation, initiate actions, pharmaceutical and surgical interventions was reported.

Results

Sulfur mustard can alkylate DNA and RNA strands and break down structures of protein and lipid of cell membrane. This may impair cell energy production, and leads to cell death. Exposure to sulfur mustard, therefore, causes such problems for organs, including irreversible damage to the eyes.

Conclusion

Understanding the mechanism of the sulfur mustard effect and the early training in prevention injuries will cause fewer complications and damage to organs, including the eyes. Washing the eyes with tap water or eyewash solutions, using mydriatic drops, anti- inflammatory drugs, matrix metalloproteinase inhibitors and antibiotics may help to the management of poisoning. Surgical interventions including tarsorrhaphy, amniotic membrane transplantation, stem cell transplantation and corneal transplantation could reduce the harm to the victims.

Posterior lamellar keratoplasty: techniques, outcomes, and recent advances

Over the past 2 decades, posterior lamellar keratoplasty (PLK) has emerged as an alternative to penetrating keratoplasty in the treatment of corneal endothelial disorders. The reasons for this trend include the search for a safer procedure to replace diseased endothelium that provides faster and better visual rehabilitation and reduces the need for postoperative care. Different surgical techniques, surgical instruments, devices, and lasers have been introduced to overcome technical difficulties, thus improving clinical outcomes. Yet, surgeons and eye banks must address the complications and limitations that arise during the transition to these new techniques. This review discusses the most significant aspects of the evolution of PLK, including a detailed description of current techniques and the direction of future treatment for corneal endothelial disease with the use of laser-assisted surgery, bioengineered corneas, cell therapy, and new pharmacologic therapy.

Management of Corneal Clouding in Patients with Mucopolysaccharidosis

Mucopolysaccharidoses (MPS) are a rare group of lysosomal storage disorders characterized by the accumulation of incompletely degraded glycosaminoglycans (GAGs) in multiple organ systems including the eye. Visual loss occurs in MPS predominantly due to corneal clouding and retinopathy, but the sclera, trabecular meshwork and optic nerve may all be affected. Despite the success of therapies such as enzyme replacement therapy (ERT) and hematopoietic stem-cell transplantation (HSCT) in improving many of the systemic manifestations of MPS, their effect on corneal clouding is minimal. The only current definitive treatment for corneal clouding is corneal transplantation, usually in the form of a penetrating keratoplasty or a deep anterior lamellar keratoplasty. This article aims to provide an overview of corneal clouding, its current clinical and surgical management, and significant research progress.

Preferred practice pattern and observed outcome of deep anterior lamellar keratoplasty - A survey of Indian corneal surgeons

Purpose

This study aimed to assess the preferred surgical technique and outcome of deep anterior lamellar keratoplasty (DALK) among corneal surgeons in India.

Methods

An online questionnaire-based cross-sectional survey was conducted among members of the Cornea Society of India (CSI) with experience of performing >10 DALK procedure. The responses pertaining to their surgical experience, preferred technique, complications, and outcome of DALK were collected and analyzed.

Results

A total of 156 responses were received. In total, 35.9% of participants reported annual keratoplasty of >50, and DALK constituted >25% surgeries for 25% of participants. Ectatic corneal disorder was reported as the most common indication for DALK by 71.6% of the respondents. Big-bubble (BB) DALK (WA-1.82) was the most preferred technique, along with suction trephine (50%) for partial trephination and bottom port cannula (45.5%) for BB formation. On statistical analysis, no difference was observed in the surgeon reported success rate of BB formation with or without anterior lamellar keratectomy (ALK) (χ2 (1,156) = 3.1498, P = 0.08) or paracentesis (χ2 (1,156) = 0.2737, P = 0.60) before stromal air injection, and method of stromal air injection (χ2 (1,156) = 4.7325, P = 0.09). Conversion to penetrating keratoplasty was reported by 16% of participants in >25% cases, while 66.7% reported in <10% cases. Cataract and double anterior chamber were the most common complications. 50% of participants suggested that >20 procedures are required to overcome the learning curve.

Conclusion

BB DALK is the most commonly practiced DALK technique, and its success is independent of ALK and paracentesis being performed prior to air injection and method of air injection (cannula/needle).

[One-piece mushroom keratoplasty outcomes]

PURPOSE

To clinically evaluate the results of one-piece mushroom-shaped keratoplasty.

MATERIAL AND METHODS

A total of 10 patients (10 eyes) were enrolled, all having corneal perforations and deep stromal opacities with involvement of Descemet's membrane. For transplantation, hypothermic preserved donor corneas with mean endothelial cell density of 2896±327 cells per 1 mm² were used. Surgical technique. Recipient tissues as well as the graft were cut with the Moria trephine. For that, the 8.5-mm blade was replaced by a 6.5-mm one and vice versa, respectively, with attention paid not to violate the vacuum while making the cuts.

RESULTS

Transparent cornea engraftment was achieved in all patients. Best corrected visual acuity averaged 0.55±0.22. Spherical component of refraction varied from -4.25 to +2.75 diopters. Mean corneal astigmatism was 3.35±1.73 diopters. At 6 months after surgery, the mean endothelial cell density was 2355±336 cells/mm², at 1 year - 2141±304 cells/mm2.

CONCLUSION

One-piece mushroom keratoplasty is an effective surgical treatment of corneal perforations and deep stromal opacities with involvement of Descemet's membrane that ensures a high rate of transparent corneal engraftment. The use of the Moria vacuum trephine in combination with blades of different diameters and secure fixation of the vacuum part of the trephine eliminate the risk of the 'mushroom stem' decentration relative to its 'head'.

Engineering a Corneal Stromal Equivalent Using a Novel Multilayered Fabrication Assembly Technique

To overcome the serious shortage of donor corneas for transplantation, alternatives based on tissue engineering need to be developed. Decellularized corneas are one potential alternative, but their densely packed collagen architecture inhibits recellularization in vitro. Therefore, a new rapid method of recellularizing these constructs to ensure high cellularity throughout the collagen scaffold is needed. In this study, we developed a novel method for fabricating corneal constructs by using decellularized porcine corneal sheets assembled using a bottom-up approach by layering multiple sheets between cell-laden collagen I hydrogel.

Corneal lenticules were cut from porcine corneas by cryosectioning, then decellularized with detergents and air-dried for storage as sheets. Human corneal stromal cells were encapsulated in collagen I hydrogel and cast between the dried sheets. Constructs were cultured in serum-free medium supplemented with ascorbic acid and insulin for 2 weeks. Epithelial cells were then seeded on the surface and cultured for an additional week. Transparency, cell viability, and phenotype were analyzed by qPCR, histology, and immunofluorescence. Constructs without epithelial cells were sutured onto an ex vivo porcine cornea and cultured for 1 week.

Lenticules were successfully decellularized, achieving dsDNA values of 13 ± 1.2 ng/mg dry tissue, and were more resistant to degradation than the collagen I hydrogels. Constructs maintained high cell viability with a keratocyte-like phenotype with upregulation of keratocan, decorin, lumican, collagen I, ALDH3A1, and CD34 and the corneal epithelial cells stratified with a cobblestone morphology. The construct was amenable to surgical handling and no tearing occurred during suturing. After 7 days ex vivo, constructs were covered by a neoepithelium from the host porcine cells and integration into the host stroma was observed.

This study describes a novel approach toward fabricating anterior corneal substitutes in a simple and rapid manner, obtaining mature and suturable constructs using only tissue-derived materials.

[Modern modifications of penetrating keratoplasty with complex operative incision]

The basic principle of modern keratoplasty is selectivity, i.e. the choice of whether to replace only the affected corneal layer. However, when layer-by-layer and interlayer transplantation is not indicated, the method of choice is conventional penetrating keratoplasty. An alternative can be its modifications with complex profiles of the transplant edges and the bed, which are better justified in terms of pathogenesis. The most popular among them are mushroom, zig-zag and top-hat. These surgeries combine optical benefits of penetrating keratoplasty as they do not involve dissection of the corneal optical zone and can negate - to a certain degree - its main downsides such as low trauma tolerance of the postoperative scar, significant level of postoperative astigmatism, and increased visual rehabilitation time. Mushroom-shaped incisions can be performed manually with a femtosecond laser or a microkeratome, zig-zag incision - only with a femtosecond laser. Considering the diversity of keratoplasty modifications with complex operative incisions, further research is required for evaluation of their clinical effectiveness and analysis of postoperative complications.

Clinical efficacy of therapeutic keratoplasty using corneal xenografts in patients with corneal ulcers

Objective. to assess the clinical efficacy of keratoplasty using a corneal xenograft in patients with corneal ulcers of various etiologies. Methods. A total of 46 patients (49 eyes) with complicated corneal ulcers (perforated or with impending perforation) have been operated. Freeze-dried corneal xenografts have been used for keratoplasty. Results. Our results showed that postoperative period after xenogeneic keratoplasty in patients with corneal ulcers was uneventful and the transplant underwent gradual resorption. In all patients with non-infected corneal erosions, ulcers healed completely and corneal fistulas were fully closed. The implanted corneal xenograft undergoes complete resorption between 2 to 3 months. Conclusions. Given the shortages of donor material, the demonstrated efficacy of using corneal xenografts in patients with complicated corneal ulcers requiring therapeutic keratoplasty allows recommending corneal xenografts for wide use to relieve inflammation and to preserve the eye.

Air pressure changes in the creation and bursting of the type-1 big bubble in deep anterior lamellar keratoplasty: an ex vivo study

PurposeTo measure the pressure and volume of air required to create a big bubble (BB) in simulated deep anterior lamellar keratoplasty (DALK) in donor eyes and ascertain the bursting pressure of the BB.Patients and methodsTwenty-two human sclera-corneal discs were used. Air was injected into the corneal stroma to create a BB and the pressure measured by means of a pressure converter attached to the system via a side port. A special clamp was designed to prevent air leak from the periphery of the discs. The pressure at which air emerged in the corneal tissue; the bursting pressure measured after advancing the needle into the bubble cavity and injecting more air; the volume of air required to create a BB and the volume of the BB were ascertained.ResultsType-1 BB were achieved in 19 and type-2 BB in 3 eyes. The maximum pressure reached to create a BB was 96.25+/- 21.61 kpa; the mean type-1 intrabubble pressure was 10.16 +/- 3.65 kpa. The mean bursting pressure of a type-1 BB was 66.65 +/- 18.65 kpa, while that of a type-2 BB was 14.77 +/- 2.44 kpa. The volume of air required to create a type-1 BB was 0.54 ml and the volume of a type-1 BB was consistently 0.1 ml.ConclusionsDua's layer baring DALK can withstand high intraoperative pressures compared to Descemet's membrane baring DALK. The study suggests that it could be safe to undertake procedures such as DALK-triple with a type-1 BB but not with a type-2 BB.

Spontaneous corneal perforation in Terrien's marginal degeneration in childhood: A case report

RATIONALE

Terrien's marginal corneal degeneration (TMD) is characterized by progressive peripheral corneal thinning. It appears primarily above the age of 40 years and is rare at younger ages. Spontaneous corneal perforation in TMD is a rare, but serious complication that may occur in childhood.

PATIENT CONCERNS

This review presents the case of a 16-year-old girl presented with blurred vision in the right eye on awakening in the morning. Slit-lamp examination revealed superior corneal thinning with a corneal perforation.

DIAGNOSES

The best-corrected visual acuity (BCVA) was 20/50 in the right eye and 20/20 in the left eye. Intraocular pressures were 5 and 18 mm Hg in the right and left eyes, respectively, measured using a noncontact tonometer. Slit-lamp examination revealed superior corneal thinning with superficial pannus. A 1-mm corneal perforation was observed at the 11 o'clock position. The anterior chamber of the right eye was flat and the Seidel test result was positive. The left eye showed no apparent abnormality on slit-lamp examination. Corneal topography showed 4.3 D of against-the-rule astigmatism, and anterior segment optical coherence tomography revealed superior corneal thinning. We diagnosed it as childhood onset TMD.

INTERVENTIONS

Multilayered amniotic membrane transplantation was performed over the perforation site and a bandage contact lens was placed.

OUTCOMES

At 1 week postoperatively, the BCVA of the right eye improved to 20/32, the amniotic membrane graft was well-attached, and the anterior chamber remained deep. At 2 months postoperatively, the BCVA was 20/25 and the anterior chamber depth was maintained.

LESSONS

Spontaneous corneal perforation due to TMD is rare, but may occur in childhood. The possibility of corneal perforation should be considered even in childhood and good surgical results can be obtained with amniotic membrane transplantation.

Corneal Biomechanical Properties After Penetrating Keratoplasty or Deep Anterior Lamellar Keratoplasty Using the Ocular Response Analyzer: A Meta-Analysis

PURPOSE

To evaluate the corneal biomechanical properties of patients who have undergone penetrating keratoplasty (PK) or deep anterior lamellar keratoplasty (DALK) using the ocular response analyzer.

METHODS

Stata 13.0 SE was used for this meta-analysis. Studies in the literature that focused on corneal hysteresis (CH) or corneal resistance factor (CRF) after PK or DALK were retrieved by searching PubMed, Embase, Ovid, and Cochrane databases. We present the results as weighted mean difference (WMD) with a corresponding 95% confidence interval (CI).

RESULTS

Eight studies with a total of 750 eyes were included in the post-PK versus control group, and 4 studies with a total of 218 eyes were included in the post-DALK versus control group. The pooled results showed that CH and CRF were significantly reduced (P < 0.00001) for patients who have undergone PK (WMD = -1.16, 95% CI: -1.73 to -0.60 and WMD = -1.00, 95% CI: -1.61 to -0.40). No significant differences were found in both CH and CRF for patients who have undergone DALK (WMD = -0.27, 95% CI: -0.64 to -0.09 and WMD = -0.15, 95% CI: -0.53 to 0.23).

CONCLUSIONS

This meta-analysis suggested that both CH and CRF had better recovery after corneal transplantation with DALK than PK.

Corneal Stroma Regeneration with Acellular Corneal Stroma Sheets and Keratocytes in a Rabbit Model

Acellular corneal stroma matrix has been used for corneal stroma engineering. However, because of its compact tissue structure, regrowth of keratocytes into the scaffold is difficult. Previously, we developed a sandwich model for cartilage engineering using acellular cartilage sheets. In the present study, we tested this model for corneal stroma regeneration using acellular porcine corneal stroma (APCS) sheets and keratocytes. Porcine corneas were decellularized by NaCl treatment, and the APCS was cut into 20-μm-thick sheets. A rabbit corneal stroma defect model was created by lamellar keratoplasty and repaired by transplantation of five pieces of APCS sheets with keratocytes. Six months after transplantation, transparent corneas were present in the experimental group, which were confirmed by anterior segment optical coherence tomography examination and transmittance examination. The biomechanical properties in the experimental group were similar to those of normal cornea. Histological analyses showed an even distribution of keratocytes and well-oriented matrix in the stroma layer in the experimental group. Together, these results demonstrated that the sandwich model using acellular corneal stroma sheets and keratocytes could be potentially useful for corneal stroma regeneration.

A Two-Piece Microkeratome-Assisted Mushroom Keratoplasty Improves the Outcomes and Survival of Grafts Performed in Eyes with Diseased Stroma and Healthy Endothelium (An American Ophthalmological Society Thesis)

PURPOSE

To test the hypothesis that a new microkeratome-assisted penetrating keratoplasty (PK) technique employing transplantation of a two-piece mushroom-shaped graft may result in better visual outcomes and graft survival rates than those of conventional PK.

METHODS

Retrospective chart review of 96 eyes at low risk and 76 eyes at high risk for immunologic rejection (all with full-thickness central corneal opacity and otherwise healthy endothelium) undergoing mushroom PK between 2004 and 2012 at our Institution. Outcome measures were best-corrected visual acuity (BCVA), refraction, corneal topography, endothelial cell density, graft rejection, and survival probability.

RESULTS

Five years postoperatively, BCVA of 20/40 and 20/20 was recorded in 100% and over 50% of eyes, respectively. Mean spherical equivalent of refractive error did not vary significantly over a 5-year period; astigmatism averaged always below 4 diopters, with no statistically significant change over time, and was of the regular type in over 90% of eyes. Endothelial cell density decreased to about 40% of the eye bank count 2 years after mushroom PK and did not change significantly thereafter. Five years postoperatively, probabilities of graft immunologic rejection and graft survival were below 5% and above 95%, respectively. There was no statistically significant difference in endothelial cell loss, graft rejection, and survival probability between low-risk and high-risk subgroups.

CONCLUSIONS

Refractive and visual outcomes of mushroom PK compare favorably with those of conventional full-thickness keratoplasty. In eyes at high risk for immunologic rejection, mushroom PK provides a considerably higher probability of graft survival than conventional PK.