Lamellar corneal transplantation

Evolving indications and surgical techniques for corneal transplantation at a tertiary eye care center in southern China

BACKGROUND

This retrospective study aimed to analyze the evolution of primary indications and surgical techniques for corneal transplantation in Southern China from 2012 to 2021.

METHODS

The medical charts of all patients who underwent keratoplasty between January 2012 and December 2021 at Zhongshan Ophthalmic Centre, Sun Yat-Sen University, Guangzhou, Southern China were reviewed. We collected and analyzed the primary indications for corneal transplantation and the surgical methods used in each keratoplasty.

RESULTS

The total number of corneal transplantations was 7,286 during this decade, increasing from 210 cases in 2012 to 1054 cases in 2021. The primary indications for keratoplasty included acquired nontraumatic corneal diseases (56.2%), congenital corneal abnormalities (16.4%), acquired traumatic corneal diseases (14.0%), and regraft (13.4%). Infectious keratitis was the leading indication among all keratoplasties (18.5%), followed by regraft (13.4%). Over the decade, the proportion of infectious keratitis gradually decreased (P = 0.013), while the proportion of regraft increased (P = 0.019). The predominant surgical technique was penetrating keratoplasty (PKP), accounting for 56.7%. However, the number of deep anterior lamellar keratoplasty (DALK) and endothelial keratoplasty (EK) significantly increased from 2012 to 2021 (P = 0.007 and P = 0.002).

CONCLUSIONS

The annual number of corneal transplants significantly increased from 2012 to 2021. In the past decade, infectious keratitis and regraft have become the leading primary indications for corneal transplantation. Although the use of customized lamellar techniques has dramatically increased, PKP remains the predominant surgical technique for keratoplasty.

Donor Risk Factors and Environmental Conditions Associated With Poor-Quality Corneas: An Analysis of the Central Eye Bank of Iran (2018-2021)

PURPOSE

The purpose of this study was to investigate the donor risk factors and environmental conditions associated with poor-quality corneas using the database of the Central Eye Bank of Iran over 4 years.

METHODS

This cohort study was conducted on the recorded data of all donated corneas at the Central Eye Bank of Iran database from March 2018 to March 2022. Donors' characteristics and tissue variables were extracted from the database. The final corneal quality was determined based on slitlamp biomicroscopic observations and the results of specular microscopy. Environmental variables were also obtained from reliable resources. Risk factors for poor-quality corneas were calculated using logistic mixed-effect regression analysis. All analyses were performed with STATA 17.0. The significance level of 0.05 was considered for all the analyses.

RESULTS

The data of 20,625 eyes of 10,601 donors were evaluated. We found that donor age had an inverse correlation with endothelial cell density (r = -0.28, P < 0.001). The trend of donated corneal poor quality decreased between 2018 and 2021. Several factors, including intoxication (odds ratio [OR] = 1.29), obesity (OR = 1.34), diabetes mellitus (OR = 1.63), hypertension (OR = 1.52), and pseudophakic eyes (OR = 1.56), were associated with the poor quality of donated corneal tissues. The outdoor temperature over 26°C was associated with higher odds of poor corneal quality (OR = 1.31), whereas high relative humidity decreased the odds of poor corneal quality (OR = 0.82).

CONCLUSIONS

This study revealed that the cause of donor death, obesity, donor comorbidities, pseudophakia, and environmental factors could affect the corneal quality and make the donated corneas less suitable for transplantation.

[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.

Design and Experiment of an Ultrasound-Assisted Corneal Trephination System

According to the advantages of ultrasonic vibration cutting, an ultrasound-assisted corneal trepanation robotic system is developed to improve the accuracy of corneal trephination depth and corneal incision quality in corneal trephination operations. Firstly, we analyzed the reasons for the difficulty in controlling the depth of trephination in corneal transplantations from the perspective of the biomechanical properties of the cornea. Based on the advantages of ultrasonic vibration cutting, we introduced an ultrasonic-vibration-assisted cutting method for corneal trephination and analyzed the cutting mechanism. Secondly, we described the surgical demands of corneal trephination and listed the design requirements of a robotic system. Thirdly, we introduced the design details of said system, including the system's overall structure, the ultrasound-assisted end effector, the key mechanisms of the robotic system, and the human-machine interaction interface. We designed the end effector based on ultrasonic vibration cutting and its eccentric adjustment system in an innovative way. Additionally, we then presented a procedure for robot-assisted corneal trephination. Finally, we performed several cutting experiments on grapes and porcine eyeballs in vitro. The results show that, compared with manual trephine, ultrasound-assisted corneal trephination has a better operation effect on the accuracy of corneal trephination depth and corneal incision quality.

From bench to clinic: Emerging therapies for corneal scarring

Corneal diseases are one of the leading causes of moderate-to-severe visual impairment and blindness worldwide, after glaucoma, cataract, and retinal disease in overall importance. Given its tendency to affect people at a younger age than other blinding conditions such as cataract and glaucoma, corneal scarring poses a huge burden both on the individuals and society. Furthermore, corneal scarring and fibrosis disproportionately affects people in poorer and remote areas, making it a significant ophthalmic public health problem. Traditional medical strategies, such as topical corticosteroids, are not effective in preventing fibrosis or scars. Corneal transplantation, the only effective sight-restoring treatment for corneal scars, is curbed by challenges including a severe shortage of tissue, graft rejection, secondary conditions, cultural barriers, the lack of well-trained surgeons, operating rooms, and well-equipped infrastructures. Thanks to tremendous research efforts, emerging therapeutic options including gene therapy, protein therapy, cell therapy and novel molecules are in development to prevent the progression of corneal scarring and compliment the surgical options currently available for treating established corneal scars in clinics. In this article, we summarise the most relevant preclinical and clinical studies on emerging therapies for corneal scarring in recent years, showing how these approaches may prevent scarring in its early development.

Determining the learning curve for a novel microsurgical procedure using histopathology

PURPOSE

Wet laboratories are becoming an increasingly important training tool as part of a push to a proficiency-based training model. We created a microsurgical wet laboratory to investigate the utility of histopathology use in assessing surgical outcomes and determine the learning curve of a novel microsurgical procedure.

METHODS

A microsurgical wet laboratory was established using pig eyes to simulate the human cornea. Three novice surgeons and an experienced surgeon performed an anterior cornea lamellar dissection and the duration of the procedure was recorded. With the aid of histological analysis, the thickness and characteristics of the dissected graft was recorded. The number of attempts to complete the experiment, defined as three successful dissections with mean thickness below 100 μm, was documented.

RESULTS

The use of histopathology was highly successful allowing in-depth analysis of the dissected graft for each attempt. Trainees reached the endpoint of the study in 21, 26 and 36 attempts (mean: 28 attempts) whilst the corneal surgeon completed the experiment in 12 attempts (p = 0.07). Mean dissection thickness decreased over time for all participants. The mean dissection time for trainees was 10.6 ± 4.2 min compared to the corneal surgeon with a mean of 8.2 ± 3.1 min (p = 0.03).

CONCLUSION

We propose a corneal wet laboratory model that allows for simple, efficient, and flexible microsurgical training. The use of histopathological analysis allows for careful graft analysis, providing objective feedback throughout the training exercise. Trainees demonstrated improvements in the three key aspects of the procedure: accuracy as evidenced by decreasing histological thickness, confidence by self-report and fluidity by decreasing duration of the procedure.

[Nerve fiber structure after different types of corneal transplantation]

This review presents basic information about the state of corneal nerve fibers and Langerhans cells before and after keratoplasty. Keratoplasty is a common corneal surgery that carries a risk of graft rejection. The state of corneal nerve fibers can vary after different types of keratoplasty. Corneal confocal microscopy allows in vivo evaluation of the cornea, which can help assess the condition of corneal nerve fibers, as well as reveal the presence of Langerhans cells. Further research in this direction would contribute to identifying the relationship between the state of corneal nerve fibers, the presence of Langerhans cells, and graft rejection.

[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'.

Deep Anterior Lamellar Keratoplasty After Previous Anterior Lamellar Keratoplasty to Improve the Visual Outcomes

PURPOSE

To describe a series of patients who underwent deep anterior lamellar keratoplasty (DALK) after previous anterior lamellar keratoplasty (ALK) to improve their visual outcomes.

METHODS

This is a retrospective case series of 9 DALK eyes (9 patients) with a history of previous ALK and an unsatisfactory visual outcome. Surgery was performed in all cases at least 3 years after ALK. Cannula big bubble, air viscobubble, and manual dissection techniques were performed. Preoperative and postoperative best-corrected visual acuity, residual recipient bed thickness, and endothelial cell count were evaluated. Follow-up was at least 24 months for all eyes.

RESULTS

Two subtotal anterior lamellar keratoplasties (through 1 type 1 big bubble and 1 air viscobubble) and 7 manual dissection DALKs were achieved. A small rupture of the residual recipient bed occurred during 1 case, and it was managed without penetrating keratoplasty conversion. Mean best-corrected visual acuity improved from 0.64 to 0.09 logMAR. Postoperative residual recipient central bed thickness was less than 80 μm in all cases. No postoperative complications were recorded at the last follow-up (24-36 months postoperatively).

CONCLUSIONS

Different DALK techniques can be successfully used to improve visual acuity in previous ALK eyes with an unsatisfactory visual outcome.

[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.

Corneal transplantation in the modern era

Corneal blindness is one of the major causes of reversible blindness, which can be managed with transplantation of a healthy donor cornea. It is the most successful organ transplantation in the human body as cornea is devoid of vasculature, minimizing the risk of graft rejection. The first successful transplant was performed by Zirm, and since then, corneal transplantation has seen significant evolution. It has been possible because of the relentless efforts by researchers and the increase in knowledge about corneal anatomy, improvement in instruments and advancements in technology. Keratoplasty has come a long way since the initial surgeries wherein the whole cornea was replaced to the present day where only the selective diseased layer can be replaced. These newer procedures maintain structural integrity and avoid catastrophic complications associated with open globe surgery. Corneal transplantation procedures are broadly classified as full-thickness penetrating keratoplasty and partial lamellar corneal surgeries which include anterior lamellar keratoplasty [sperficial anterior lamellar keratoplasty (SALK), automated lamellar therapeutic keratoplasty (ALTK) and deep anterior lamellar keratoplasty (DALK)] and posterior lamellar keratoplasty [Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK)] broadly.

[Mushroom keratoplasty in rosacea keratitis complicated by corneal perforation (a clinical case)]

Rosacea is a polyethiologic chronic inflammatory disease with varying clinical manifestations. It is primarily a dermatologic disease, which often manifests in the eyes affecting eyelids, cornea and conjunctiva. The leading role in the pathological process belongs to disruption of regulatory mechanisms in the vascular, immune and nervous systems. It is accompanied by increased levels of metalloproteinases and vascular endothelial growth factor (VEGF). Treatment depends on the severity of the disease and may vary from hygiene of the eyelid margins and use of artificial tears for dry eye disease management, to antibiotics and anti-inflammatory agents in moderate cases, and surgical treatment in severe or neglected state. A clinical case of severe rosacea shows that keratoplasty with mushroom-shaped profile of the surgical incision helps achieve good functional results and reduce the post-operative rehabilitation time, while significantly reducing the risk of postsurgical complications. Anti-VEGF therapy significantly reduces the risk of histoincompatibility reaction typical for rosacea keratitis.

Interface infectious keratitis after anterior and posterior lamellar keratoplasty. Clinical features and treatment strategies. A review

Interface infectious keratitis (IIK) is a novel corneal infection that may develop after any type of lamellar keratoplasty. Onset of infection occurs in the virtual space between the graft and the host where it may remain localised until spreading with possible risk of endophthalmitis. A literature review identified 42 cases of IIK. Thirty-one of them occurred after endothelial keratoplasty and 12 after deep anterior lamellar keratoplasty. Fungi in the form of Candida species were the most common microorganisms involved, with donor to host transmission of infection documented in the majority of cases. Donor rim cultures were useful to address the infectious microorganisms within few days after surgery. Due to the sequestered site of infection, medical treatment, using both topical and systemic antimicrobials drugs, was ineffective on halting the progression of the infection. Injection of antifungals, right at the graft–host interface, was reported successful in some cases. Spreading of the infection with development of endophthalmitis occurred in five cases after Descemet stripping automated endothelial keratoplasty with severe sight loss in three cases. Early excisional penetrating keratoplasty showed to be the treatment with the highest therapeutic efficacy, lowest rate of complications and greater visual outcomes.

Deep anterior lamellar keratoplasty of dog eyes using the big-bubble technique

This study was conducted to establish the feasibility of corneal transplantation using the big-bubble technique (BBT) to perform deep anterior lamellar keratoplasty (DALK) in three dogs. After the cornea was trephined 750 µm, 4 mL of air was injected, and the blanched stroma was removed to expose Descemet's membrane (DM). The donor corneal button, which was gently stripped off the DM, was sutured onto the bare DM of the recipient cornea. The dogs received topical antibiotics every 6 h for 7 days and 2% cyclosporine ointment every 12 h for 1 month. The eyes were examined post-operatively at 7, 14, 21, 28 and 150 days. The central portion of the transplanted cornea stayed transparent while corneal haze developed around the transplanted margin. Menace response was normal even though the transplanted cornea was edematous until 3 weeks after surgery. A marginal haze was rarely observed between the donor and recipient corneas at 150 days after the operation. A spotted haze developed in the central part of the deep stroma near the DM. Upon histopathological examination, the stroma and epithelium of the donor cornea had normal structures. Corneal transplantation using DALK with BBT can be performed in dogs preserving the healthy endothelium.

Current techniques of lamellar keratoplasty for keratoconus

In recent years, there has been a considerable interest regarding the concept of lamellar keratoplasty (LK), which contributed in spreading the use of this procedure in the treatment of keratoconus. This is a new frontier in corneal surgery that minimizes trauma on the recipient patient since it works on a "closed bulb". The LK surgery, in fact, aims to selectively replace diseased corneal stroma, leaving the healthy endothelium. The main advantage of LK is to avoid major causes of failure of penetrating keratoplasty as immunological rejection, and the late mismatch in the transplanted cornea, thus increasing the life of transplantation. In the last decade, several techniques of LK have been proposed, depending on how the anterior portion of the recipient cornea is removed. This article, through a literary research reviews the various emerging techniques of anterior lamellar surgery for the management of keratoconus, analyzing their indications, visual outcomes, and rate of complications.

Intraoperative optical coherence tomography in descemet stripping automated endothelial keratoplasty: pilot experiences

Purpose

To assess the added value of intraoperative optical coherence tomography (iOCT) in evaluating graft adhesion and graft interface in patients undergoing descemet’s stripping automated endothelial keratoplasty (DSAEK).

Methods

This is a prospective single-center case series comprising 8 eyes of 8 patients consecutively scheduled for DSAEK surgery. iOCT imaging was performed after insertion of the graft, after pressurizing the eye, and at the end of surgery (three images per surgery). At each stage of surgery, corneal thickness and the widest gap between the recipient and the graft (i.e., maximal interface width) were measured using an image processing tool. Follow-up measurements were taken at 1 day, 3 and 6 months, post-operatively.

Results

Imaging was performed in 21 of 24 scheduled imaging intervals, and required little to no additional surgical time. At the end of surgery, iOCT showed persisting interfaces in six cases. One case showed a full graft detachment necessitating surgical intervention.

Conclusion

Real-time iOCT is a safe, efficient, and useful tool in assessing graft adherence in DSAEK surgery. With adequate analysis software, iOCT has the potential to be a paradigm-shifting development in posterior lamellar surgery and could aid the clinician in further lowering the rates of graft dislocation after DSAEK.

Effects of corneal stromal cell- and bone marrow-derived endothelial progenitor cell-conditioned media on the proliferation of corneal endothelial cells

AIM

To explore the effects of conditioned media on the proliferation of corneal endothelial cells (CECs) and to compare the efficiency of different conditioned media (CM).

METHODS

Rat CECs, corneal stromal cells (CSCs), bone marrow-derived endothelial progenitor cells (BEPCs), and bone marrow-derived mesenchymal stem cells (BMSCs) were isolated and cultured in vitro. CM was collected from CSCs, BEPCs, and BMSCs. CECs were cultivated in different culture media. Cell morphology was recorded, and gene and protein expression were analyzed.

RESULTS

After grown in CM for 5d, CECs in each experimental group remained polygonal, in a cobblestone-like monolayer arrangement. Immunocytofluorescence revealed positive expression of Na(+)/K(+)-ATP, aquaporin 1 (AQP1), and zonula occludens 1 (ZO-1). Based on quantitative polymerase chain reaction (qPCR) analysis, Na(+)/K(+)-ATP expression in CSC-CM was notably upregulated by 1.3-fold (±0.036) (P<0.05, n=3). The expression levels of ZO-1, neuron specific enolase (NSE), Vimentin, paired homebox 6 (PAX6), and procollagen type VIII (COL8A1) were notably upregulated in each experimental group. Each CM had a positive effect on CEC proliferation, and CSC-CM had the strongest effect on proliferation.

CONCLUSION

CSC-CM, BEPC-CM, and BMSC-CM not only stimulated the proliferation of CECs, but also maintained the characteristic differentiated phenotypes necessary for endothelial functions. CSC-CM had the most notable effect on CEC proliferation.

Determinants of visual quality after endothelial keratoplasty

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

[Complications of Descemet Stripping Automated Endothelial Keratoplasty (DSAEK)]

BACKGROUND

Lamellar keratoplasties, e.g. Descemet's stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK) are considered the procedures of choice for corneal endothelial diseases. In comparison to penetrating keratoplasty (PK) they are associated with faster visual rehabilitation, a lower risk of complications and a decreased necessity for follow-up visits, which reduces the burden on quality of life in elderly patients. In order to advise patients regarding the indications for surgery and to facilitate the follow-up management, it is important to know the most important complications associated with these keratoplasty techniques.

RESULTS AND DISCUSSION

The most important preoperative complication is a delayed indication for the operation. In contrast to PK, DSAEK and DMEK surgery should be provided at an earlier stage of disease as chronic edema alters the stroma and reduces the speed of visual recovery. The most important complications during or early after surgery are detached lamellae, pupillary blocks with increased pressure or air bubbles in the vitreous cavity in patients with previous vitrectomy. The main long-term complications include chronic increased intraocular pressure and immune-mediated graft rejections in DSAEK patients after reducing or stopping topical corticosteroid therapy. This article describes the potential complications of endothelial keratoplasty and provides a detailed explanation of strategies to avoid these complications.

Bioengineered Corneas Grafted as Alternatives to Human Donor Corneas in Three High-Risk Patients

Corneas with severe pathologies have a high risk of rejection when conventionally grafted with human donor tissues. In this early observational study, we grafted bioengineered corneal implants made from recombinant human collagen and synthetic phosphorylcholine polymer into three patients for whom donor cornea transplantation carried a high risk of transplant failure. These patients suffered from corneal ulcers and recurrent erosions preoperatively. The implants provided relief from pain and discomfort, restored corneal integrity by promoting endogenous regeneration of corneal tissues, and improved vision in two of three patients. Such implants could in the future be alternatives to donor corneas for high-risk patients, and therefore, merits further testing in a clinical trial.

Manual Medium Incision Cataract Surgery with Descemet's Stripping Endothelial Keratoplasty: A Novel Triple Procedure

Purpose. To describe the surgical technique and outcomes of combined Descemet's stripping endothelial keratoplasty and medium incision manual cataract surgery (MICS) in Chinese eyes. Methods. Surgery was performed in 8 eyes of 7 patients (5 females, 2 males). Primary outcomes included success of the surgery and final outcomes. Results. Surgery was performed in patients with Fuchs' endothelial dystrophy and cataract (mean age 75.5 ± 3.64 years). MICS tunnel was used to insert the donor lenticule into the anterior chamber. All surgeries were performed successfully. Graft dislocation was seen in 1 eye requiring repositioning with intracameral sulfur hexafluoride gas on the first postoperative day. Graft rejection was noted in one patient at the end of one year. The mean decimal best-corrected visual acuity improved from 0.1 ± 0.07 to 0.3 ± 0.15. Suboptimal visual acuity in 2 cases was due to radiotherapy-related optic neuropathy (n = 1) and myopic maculopathy (n = 1). The mean target spherical refraction was −1.11 ± 0.17 diopters (myopic) and the mean achieved spherical refraction was 1.18 ± 0.87 diopters (hyperopic) resulting in a mean hyperopic shift of 2.2 diopters. Conclusions. The approach of combined Descemet's stripping endothelial keratoplasty and MICS is a viable surgical technique for cases with endothelial dysfunction and cataract.

Anterior-segment optical coherence tomography investigation of corneal deturgescence and epithelial remodeling after DSAEK

PURPOSE

The aim of this study was to evaluate via Fourier-domain anterior-segment optical coherence tomography 3-dimensional corneal, epithelial, and graft thickness changes after Descemet stripping automated endothelial keratoplasty (DSAEK).

METHODS

Sixteen eyes were investigated preoperatively and up to 6 months postoperatively for preoperative and postoperative central corneal thickness (CCT), minimum corneal thickness, central graft thickness (CGT), and for epithelial topographic thickness variability. An age-matched and gender-matched control group of 32 healthy eyes was used for comparison.

RESULTS

In the DSAEK group, the preoperative CCT was 582.32 ± 45.24 (550-615) μm. One-month postoperatively, the CCT was 736.26 ± 34.52 (713-771) μm, and the CGT was 210.42 ± 34.52 (145-243) μm. Three months postoperatively, the CCT was 641.39 ± 38.75 (569-684) μm, and the CGT was 171.23 ± 27.54 (119-185) μm. The preoperative center epithelial thickness was 55.74 ± 9.29 (45-74) μm, the minimum was 32.53 ± 14.30 (13-53) μm, the maximum was 76.00 ± 11.32 (64-105) μm, and the topographic thickness variability was 10.84 ± 4.09 (5.90-18.80) μm. Three months postoperatively, the center epithelial thickness was 47.21 ± 5.45 (43-56) μm, the minimum was 35.11 ± 4.70 (30-41) μm, the maximum was 58.11 ± 6.51 (49-65) μm, and the topographic variability was 4.77 ± 1.48 (2.90-6.50) μm. The average differences were -8.53, +4.53, and -17.89 μm for the center, minimum, and maximum (P < 0.001, <0.001, and <0.001). Similar results were obtained 3 and 6 months postoperatively.

CONCLUSIONS

We present a near-term postoperative investigation of the corneal and epithelial thickness changes after DSAEK for bullous keratopathy, by in vivo, clinical anterior-segment optical coherence tomography. Epithelial thickness recovery and normalization and corneal deturgescence were noted as early as in the first postoperative month.

High-resolution optical coherence tomography-guided donor tissue preparation for descemet membrane endothelial keratoplasty using the reverse big bubble technique

PURPOSE

The aim of this study was to assess the feasibility of high-resolution spectral domain optical coherence tomography (HR-SDOCT) to guide donor tissue preparation in Descemet membrane endothelial keratoplasty using the reverse big bubble technique.

METHODS

Three corneoscleral discs were included in this ex vivo experimental study. A 27-G cannula was introduced into each cornea at the periphery by 3 different surgeons. Each surgeon attempted to achieve the ideal depth (pre-Descemetic plane) of the tip of the cannula for air injection to produce the reverse big bubble to separate the Descemet membrane (DM) from the posterior stroma. A supine optical coherence tomography system built at the Ophthalmic Biophysics Center of the Bascom Palmer Eye Institute was used to estimate in real-time the depth reached by the tip of the cannula in the posterior stroma during tissue preparation.

RESULTS

After air injection, 1 successful big bubble was obtained, while each of the other corneoscleral discs had intrastromal emphysema and DM perforation. On HR-SDOCT evaluations, artifacts were noticed at the tip of the cannula. The successful big bubble demonstrated the separation of the DM and the stroma without intrastromal hyperreflectivity. Emphysema was visualized on the HR-SDOCT as a hyperdense intrastromal area shadowing the posterior structures of the anterior chamber.

CONCLUSIONS

The HR-SDOCT-guided reverse big bubble technique may be a useful method to prepare donor tissue in Descemet membrane endothelial keratoplasty. Further improvements in high-resolution optical coherence tomography technology are needed this promising technique.

Outcomes of descemet stripping automated endothelial keratoplasty in patients with an anterior chamber versus posterior chamber intraocular lens

PURPOSE

The aim of this study was to assess the implications of a retained anterior chamber intraocular lens (ACIOL) during Descemet stripping automated endothelial keratoplasty (DSAEK) and to compare the outcomes in this group with those in patients who underwent DSAEK and had a posterior chamber intraocular lens (PCIOL).

METHODS

This is a retrospective cohort study conducted in a tertiary medical center, which compares patients who underwent DSAEK and had a retained ACIOL with patients who underwent DSAEK and had a PCIOL regarding operative and postoperative complications, visual acuity, endothelial cell density, and long-term graft survival.

RESULTS

Eleven eyes with an ACIOL and 50 eyes with a PCIOL met the study criteria. No significant differences were found between the groups in terms of operative complications, change in visual acuity, graft survival, and endothelial cell loss.

CONCLUSIONS

DSAEK in the setting of an ACIOL produced similar results to those of uncomplicated PCIOL cases. Although further studies are needed to gain more accurate information on this subject, it seems that DSAEK can be performed while retaining an ACIOL with favorable results.

New perspectives on lamellar keratoplasty

Lamellar (anterior and posterior) keratoplasty entails the surgical replacement of diseased-only corneal tissue, while healthy host corneal tissue is preserved. Selective keratoplasty offers several advantages in comparison to penetrating keratoplasty such as a lower rate of graft rejection, less endothelial cell loss, faster/superior visual rehabilitation and enhanced resistance to closed injury. The surgical approach of "partial corneal transplantation" may be divided into anterior and posterior: techniques including superficial and deep anterior lamellar keratoplasty (SALK and DALK, respectively) and endothelial keratoplasty as well as Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK). These novel surgical procedures are rapidly becoming the preferred therapy option for specific corneal dysfunctions involving the corneal stroma (SALK, DALK), or corneal endothelium (DSAEK, DMEK). During the past decade, the continuing advancement of surgical techniques and the development of innovative surgical instruments have significantly enhanced corneal transplantation. Lamellar keratoplasty techniques facilitate corneal surgery, provide patients with superior outcomes and can successfully restore vision in corneal-related blindness. Nevertheless, more long-term evidence is needed to better evaluate these promising new techniques.

Anterior corneal buttons from DSAEK donor tissue can be stored in optisol GS for later use in tectonic lamellar patch grafting

PURPOSE

The aim of this study was to evaluate the feasibility of storing anterior corneal buttons split from donor Descemet stripping automated endothelial keratoplasty (DSAEK) tissue for later use in tectonic lamellar patch grafting.

METHODS

Donor corneas for DSAEK were split into anterior and posterior lamellae using a 350-μm depth microkeratome, and the remaining anterior corneal buttons were stored for up to 4 weeks at 4°C in Optisol GS before use in patch grafting of the cornea and sclera.

RESULTS

Optisol GS-preserved anterior lamellar patch grafts successfully restored and maintained corneoscleral integrity after the removal of limbal dermoids (5 cases), after the coverage of the exposed polypropylene suture ends of scleral fixated posterior chamber intraocular lenses (2 cases), corneoscleral melting after pterygium excision (3 cases), sterile corneal ulceration with or without perforation (5 cases), Mooren ulceration (3 cases), and pseudomonas corneal ulceration with impending perforation (1 case). It was also used as a temporary substitute while waiting for a full-thickness corneal graft in a fulminant candida infection after DSAEK (1 case). All grafts remained structurally intact at the last postoperative examination of 19.2 ± 7.6 months after the tectonic surgery.

CONCLUSIONS

Anterior corneal buttons from DSAEK donor tissue may be stored in Optisol GS for later use in tectonic patch grafting. This method obviates the longer operating time required for the surgeon to manually dissect the donor cornea in the operating room and reduces the wastage of precious donor corneas in countries where there are chronic shortages of eye bank donor tissue.

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.

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.

Descemet stripping endothelial keratoplasty--rapid recovery of visual acuity

BACKGROUND

Technical innovations in corneal transplantation have now made it possible to replace only the diseased part of the cornea, rather than the entire cornea as in penetrating keratoplasty (PKP). Patients with endothelial insufficiency due to Fuchs endothelial dystrophy, bullous keratopathy, or endothelial failure after keratoplasty can be treated with the new methods of posterior lamellar corneal transplantation: Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK). It remains unclear which of these methods is better in the individual case.

METHODS

We review the pertinent literature retrieved by a selective search in Medline and the Cochrane Library employing the terms "DMEK," "DSAEK," "DSEK," and "posterior lamellar keratoplasty." The publications considered in this article are those that contain important clinical information on the operative techniques.

RESULTS

No randomized controlled trials of these techniques have been published to date. Numerous case series have shown that patients who undergo DSAEK (postoperative visual acuity ≥0.5 in 38-100%), and especially those who undergo it in early or intermediate stages of endothelial insufficiency, achieve a better functional result more rapidly than patients treated with PKP (postoperative visual acuity ≥0.5 in 47-61%). Only 23-47% of DSAEK patients achieve a visual acuity of 0.8 or more, compared to 36-79% of DMEK patients. Moreover, transplant rejection is seen in only 1-3% of cases of DMEK, compared to 0-8% after DSAEK and 1-23% after PKP.

CONCLUSION

Numerous case series show clear advantages of DMEK over DSAEK, which, in turn, has better results than PKP. Nonetheless, randomized controlled trials are needed to determine which operative method is best in each stage of corneal disease.