Human Oral Mucosal Fibroblasts from Limbal Stem Cell Deficient Patients as an Autologous Feeder Layer for Epithelial Cell Culture

PURPOSE

To investigate if human oral mucosal fibroblasts (HOMF) from patients with limbal stem cell deficiency (LSCD) can be used as an autologous feeder layer to support the culture of epithelial cells for potential clinical use.

METHODS

HOMF were isolated from oral mucosal biopsies obtained from the following groups of patients with LSCD: aniridia, mucous membrane pemphigoid (MMP), Stevens-Johnson syndrome (SJS), and ectodermal dysplasia (ED). The ability of these cells to support the culture of human limbal epithelial cells (HLE) was compared to that of HOMF from non-LSCD donors and 3T3s commonly used to culture epithelial cells for use in the clinic to treat LSCD.

RESULTS

HOMF were successfully obtained by explant culture for 3/3 aniridia patients, 3/3 MMP patients, 1/3 SJS patients, and 1/1 ED patients. All HOMF cultured from these LSCD groups supported the expansion of HLE with epithelial culture times and total colony forming efficiency (CFE) comparable to those achieved on HOMF isolated from donors without LSCD. PCR showed that all HLE cultured on LSCD donor HOMF expressed p63α, CK15, PAX6, CK12, and MUC16 as did HLE cultured on the control non-LSCD donor HOMF and 3T3s. Western blotting detected CK15 and MUC16 protein expression in all groups.

CONCLUSIONS

HOMF from patients with LSCD can be successfully used to support the expansion of epithelial cells. These cells may therefore be useful as autologous feeder fibroblasts for the expansion of epithelial cells for use in the clinic to treat LSCD.

Descemet's membrane endothelial keratoplasty (DMEK) versus Descemet's stripping automated endothelial keratoplasty (DSAEK) for corneal endothelial failure

BACKGROUND

Corneal endothelial transplantation has become the gold standard for the treatment of corneal endothelial dysfunctions, replacing full thickness transplantation, known as penetrating keratoplasty. Corneal endothelial transplantation has been described using two different techniques: Descemet's membrane endothelial keratoplasty (DMEK) and Descemet's stripping automated endothelial keratoplasty (DSAEK). Both are still performed worldwide.

OBJECTIVES

To compare the effectiveness and safety of Descemet's membrane endothelial keratoplasty (DMEK) versus Descemet's stripping automated endothelial keratoplasty (DSAEK) for the treatment of corneal endothelial failure in people with Fuch's endothelial dystropy (FED) and pseudophakic bullous keratopathy (PBK).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2017, Issue 7); MEDLINE Ovid; Embase Ovid; LILACS BIREME; the ISRCTN registry; ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). The date of the search was 11 August 2017.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and non-randomised paired, contralateral-eye studies in any setting where DMEK was compared with DSAEK to treat people with corneal endothelial failure.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the search results, assessed trial quality and extracted data using the standard methodological procedures expected by Cochrane. Our primary outcome was best corrected visual acuity (BCVA) measured in logarithm of the Minimum Angle of Resolution (logMAR). Secondary outcomes were endothelial cell count, graft rejection, primary graft failure and graft dislocation. We graded the risk of bias of non-randomised studies (NRSs) using ROBINS-I.

MAIN RESULTS

We did not identify any RCTs but found four non-randomised studies (NRSs) including 72 participants (144 eyes), who had received DSAEK in the first eye followed by DMEK in the fellow eye. All the studies included adult participants where there was evidence of FED and endothelial failure requiring a corneal transplant for the treatment of visual impairment. We did not find any studies that included PBK. The trials were published between 2011 and 2015, and we assessed them as high risk of bias due to potential unknown confounding factors since DSAEK preceded DMEK in all participants. Two studies reported results at 12 months, one at 6 months, and one between 6 and 24 months. At one year, using DMEK in cases of endothelial failure may result in better BCVA compared with DSAEK (mean difference (MD) -0.14, 95% confidence interval (CI) -0.18 to -0.10 logMAR, 4 studies, 140 eyes, low-certainty evidence). None of the participants had severe visual loss (BCVA of 1.0 logMAR or more; very low-certainty evidence). Regarding endothelial cell count data (4 studies, 134 eyes) it is hard to draw any conclusions since two studies suggested no difference and the other two reported that DMEK provides a higher cell density at one year (very low-certainty evidence). No primary graft failure and only one graft rejection were recorded over four studies (144 eyes) (very low-certainty evidence). The most common complications reported were graft dislocations, which were recorded in one or two out of 100 participants with DSAEK but were more common using DMEK, although this difference could not be precisely estimated (risk ratio (RR) 5.40, 95% CI 1.51 to 19.3; 4 studies, 144 eyes, very low-certainty evidence).

AUTHORS' CONCLUSIONS

This review included studies conducted on people with corneal endothelium failure due to FED for whom both DMEK and DSAEK can be considered, and found low-certainty evidence that DMEK provides some advantage in terms of final BCVA, at the cost of more graft dislocations needing 're-bubbling' (very low-certainty of evidence).

Quantum dot labeling and tracking of cultured limbal epithelial cell transplants in vitro

PURPOSE

Cultured human limbal epithelial cells (HLECs) have shown promise in the treatment of limbal stem cell deficiency but little is known about their survival, behavior, and long-term fate after transplantation. The aim of this research was to evaluate, in vitro, quantum dot (Qdot) technology as a tool for tracking transplanted HLECs.

METHODS

In vitro cultured HLECs were labeled with Qdot nanocrystals. Toxicity was assessed using live-dead assays. The effect on HLEC function was assessed using colony-forming efficiency assays and expression of CK3, P63alpha, and ABCG2. Sheets of cultured HLECs labeled with Qdot nanocrystals were transplanted onto decellularized human corneoscleral rims in an organ culture model and observed to investigate the behavior of transplanted cells.

RESULTS

Quantum dot labeling had no detrimental effect on HLEC viability or function in vitro. Proliferation resulted in a gradual reduction in Qdot signal but sufficient signal was present to allow tracking of cells through multiple generations. Cells labeled with Qdots could be reliably detected and observed using confocal microscopy for at least 2 weeks after transplantation in our organ culture model. In addition, it was possible to label and observe epithelial cells in intact human corneas by using the Rostock corneal module adapted for use with the Heidelberg HRA.

CONCLUSIONS

This work demonstrates that Qdots combined with existing clinical equipment could be used to track HLEC for up to 2 weeks after transplantation; however, our model does not permit the assessment of cell labeling beyond 2 weeks. Further characterization in in vivo models are required.

Optimization of optical and mechanical properties of real architecture for 3-dimensional tissue equivalents: Towards treatment of limbal epithelial stem cell deficiency

Limbal epithelial stem cell (LESC) deficiency can cause blindness. Transplantation of cultured human limbal epithelial cells (hLE) on human amniotic membrane (HAM) can restore vision but clinical graft manufacture can be unreliable. We have developed a reliable and robust tissue equivalent (TE) alternative to HAM, Real Architecture for 3D Tissue (RAFT). Here, we aimed to optimize the optical and mechanical properties of RAFT TE for treatment of LESC deficiency in clinical application. The RAFT TE protocol is tunable; varying collagen concentration and volume produces differing RAFT TEs. These were compared with HAM samples taken from locations proximal and distal to the placental disc. Outcomes assessed were transparency, thickness, light transmission, tensile strength, ease of handling, degradation rates and suitability as substrate for hLE culture. Proximal HAM samples were thicker and stronger with poorer optical properties than distal HAM samples. RAFT TEs produced using higher amounts of collagen were thicker and stronger with poorer optical properties than those produced using lower amounts of collagen. The ‘optimal’ RAFT TE was thin, transparent but still handleable and was produced using 0.6 ml of 3 mg/ml collagen. Degradation rates of the ‘optimal’ RAFT TE and HAM were similar. hLE achieved confluency on ‘optimal’ RAFT TEs at comparable rates to HAM and cells expressed high levels of putative stem cell marker p63α. These findings support the use of RAFT TE for hLE transplantation towards treatment of LESC deficiency.

Culture and Characterization of Oral Mucosal Epithelial Cells on a Fibrin Gel for Ocular Surface Reconstruction

AIM OF THE STUDY

To develop a clinical grade fibrin gel for the culture of oral mucosal epithelial cells (OMEC) intended for ocular surface reconstruction in the treatment of limbal stem cell deficiency (LSCD).

MATERIALS AND METHODS

Transparent fibrin gels composed of fibrinogen and thrombin were developed for the culture of epithelial cells. Oral mucosa was harvested from the buccal region of healthy volunteers and cultured as explants on fibrin gels. Tranexamic acid (TA), a clinically approved anti-fibrinolytic agent was added to prevent the fibrin gel from digesting due to cellular activity. The gels were stained for p63α (as a marker of poorly differentiated epithelial cells), CK19, CK13 and CK3 (expressed by OMEC). Epithelial cell stratification was observed using hematoxylin-eosin staining.

RESULTS

Addition of TA prevented gels from dissolving during the culture period. OMEC proliferated on the fibrin gel and attained confluence over a 2-week period (±2 d) and exhibited a typical epithelial, cobblestone morphology. Basal OMEC exhibited positive staining for p63α while the superficial cells exhibited positive staining for CK3. The cells expressed a strong immunoreactivity for CK19 and CK13 suggesting that they retained a normal oral epithelial phenotype.

CONCLUSION

Fibrin gels, maintained in the presence of TA, to control the rate of substrate degradation, provide a more robust yet transparent substrate for the culture and transplantation of cultured OMEC. The fibrin gels are easily standardized, the components commercially available, and produced from clinically approved materials. The resulting stratified OMEC-derived epithelium displays characteristics similar to that of a human cornea, e.g. CK3 expression. The conventional dependence on a murine feeder layer for support of epithelial cells is unnecessary with this technique and hence, provides for an attractive alternative for treatment of LSCD.

Endothelial keratoplasty versus penetrating keratoplasty for Fuchs endothelial dystrophy

BACKGROUND

Fuchs endothelial dystrophy (FED) is a condition in which there is premature degeneration of corneal endothelial cells. When the number of endothelial cells is reduced to a significant degree, fluid begins to accumulate within the cornea. As a result, the cornea loses its transparency and the individual suffers a reduction in vision. The only successful surgical treatment for this condition is replacement of part or all of the cornea with healthy tissue from a donor. The established procedure, penetrating keratoplasty (PKP), has been used for many years and its safety and efficacy are well known. Endothelial keratoplasty (EK) techniques are relatively new surgical procedures and their safety and efficacy relative to PKP are uncertain.

OBJECTIVES

The objective of this review was to compare the benefits and complications related to two surgical methods (EK and PKP) of replacing the diseased endothelial layer of the cornea with a healthy layer in people with FED.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2014, Issue 1), MEDLINE (January 1950 to January 2014), EMBASE (January 1980 to January 2014), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to January 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) and ClinicalTrials.gov (www.clinicaltrials.gov). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 27 January 2014.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing EK versus PKP for people (of any age and gender) who had been clinically diagnosed with FED.

DATA COLLECTION AND ANALYSIS

Two authors independently screened the search results, assessed trial quality and extracted data using the standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We included three RCTs that enrolled a total of 139 eyes of 136 participants and analysed 123 (88%) eyes. Two RCTs randomised eyes into either the endothelial keratoplasty (EK) group or penetrating keratoplasty (PKP) group and one RCT randomised eyes into either the femtosecond laser-assisted endothelial keratoplasty (FLEK) group or PKP group. The RCTs comparing EK with PKP did not show any significant differences between procedures with respect to best corrected visual acuity (BCVA) at two years (mean difference (MD) 0.14 logMAR; 95% confidence interval (CI) -0.08 to 0.36; P = 0.23) or at one year (MD 0.09 logMAR; 95% CI -0.05 to 0.23; P = 0.22), whereas the trial comparing FLEK with PKP showed significantly better BCVA after PKP (MD 0.20 logMAR; 95% CI 0.10 to 0.30; P = 0.0001). Only one RCT reported on irregular astigmatism (higher-order aberration), which was less with EK than PKP (MD -1.20 µm; 95% CI -1.53 to -0.87; P < 0.001). Only one RCT reported on endothelial cell counts (lower after FLEK than PKP: MD -969 cells/mm²; 95% CI -1161 to -777; P < 0.001), primary graft failure (higher after FLEK than PKP: RR 7.76; 95% CI 0.41 to 145.22; P = 0.10), and graft rejection (more after FLEK than PKP: RR 1.11; 95% CI 0.07 to 17.12; P = 0.94). Only one RCT reported that 27.8% of participants had graft dislocation, 2.8% had epithelial ingrowth and postoperative pupillary block, and 13.9% had intraocular pressure (IOP)-related problems in the FLEK group compared with the PKP group, in whom 10% had suture-related problems, 5% had wound dehiscence and 10% had suture revision to correct astigmatism. Overall, the adverse events in the FLEK group appeared to be more frequent than in the PKP group. No trials reported information about quality of life or economic data. The overall methodological quality of the three trials was not satisfactory as most did not perform allocation concealment or masking of participants and outcome assessors, and all trials had a small sample size.

AUTHORS' CONCLUSIONS

The rapid growth of endothelial keratoplasty as the treatment of choice for FED is based upon the belief that visual recovery is more rapid, surgically induced astigmatism (regular and irregular) is less and rates of transplant rejection are lower with EK. This change in practice also assumes that the rates of long term transplant survival are equal for the two procedures. The practical differences between the surgical procedures mean that visual recovery is inherently more rapid following EK, but this review found no strong evidence from RCTs of any difference in the final visual outcome between EK and PKP for people with FED. This review also found that higher order aberrations are fewer following EK but endothelial cell loss is greater following EK. The RCTs that we included employed different EK techniques, which may have a bearing on these findings. EK procedures have evolved over the years and can be performed using different techniques, for example deep lamellar endothelial keratoplasty, Descemets stripping endothelial keratoplasty (DSEK), Descemets stripping automated endothelial keratoplasty (DSAEK), femtosecond laser-assisted endothelial keratoplasty and Descemet membrane endothelial keratoplasty (DMEK). More RCTs are needed to compare PKP with commonly performed EK procedures such as DSEK, DSAEK and DMEK in order to determine the answers to two key questions, whether there is any difference in the final visual outcome between these techniques and whether there are differences in the rates of graft survival in the long term?

Three-year outcomes of cultured limbal epithelial allografts in aniridia and Stevens-Johnson syndrome evaluated using the Clinical Outcome Assessment in Surgical Trials assessment tool

Limbal stem cell deficiency (LSCD) is an eye disorder in which the stem cells responsible for forming the surface skin of the cornea are destroyed by disease. This results in pain, loss of vision, and a cosmetically unpleasant appearance. Many new treatments, including stem cell therapies, are emerging for the treatment of this condition, but assessment of these new technologies is severely hampered by the lack of biomarkers for this disease or validated tools for assessing its severity. The aims of this study were to design and test the reliability of a tool for grading LSCD, to define a set of core outcome measures for use in evaluating treatments for this condition, and to demonstrate their utility. This was achieved by using our defined outcome set (which included the Clinical Outcome Assessment in Surgical Trials of Limbal stem cell deficiency [COASTL] tool) to evaluate the 3-year outcomes for allogeneic ex vivo cultivated limbal epithelial transplantation (allo-CLET) in patients who had bilateral total LSCD secondary to aniridia or Stevens-Johnson syndrome. The results demonstrate that our new grading tool for LSCD, the COASTL tool, is reliable and repeatable, and that improvements in the biomarkers used in this tool correlate positively with improvements in visual acuity. The COASTL tool showed that following allo-CLET there was a decrease in LSCD severity and an increase in visual acuity up to 12 months post-treatment, but thereafter LSCD severity and visual acuity progressively deteriorated.

The impact of age on the physical and cellular properties of the human limbal stem cell niche

The limbal niche in the corneoscleral junction of the eye, habitat of the limbal epithelial stem cells (LESC), facilitates corneal epithelial regeneration by providing physical support and chemical signalling. Anatomical structures within the limbus, namely, limbal epithelial crypts and focal stromal projections, are believed to function as a putative niche for LESCs. In this study, the impact of age on the topography of this niche was investigated. Also, the relationship between niche topography and limbal epithelial cell phenotype was assessed. Ex vivo imaging of the limbus in cadaveric tissue of donors aged from infancy to 90 years was carried out using electron and confocal microscopy. The data suggested that the area occupied by the crypts was sharply reduced after the age of 60 years. The niche microstructures also became smoother with donor age. The phenotypic assessment of cultured limbal epithelial cells harvested from donors of different ages showed that the levels of putative stem cell markers as well as telomerase activity and telomere length remained unchanged, regardless of niche topography. However, the colony forming efficiency of the cultures was significantly reduced with age (p < 0.05). This is the first comprehensive study of the effect of age on the structural and phenotypic characteristics of the human limbal niche. The results have a significant biological value as they suggest a correlation of limbal architecture with decline of re-epithelialisation rate in older patients. Overall, the data also suggest that LESCs harvested from younger donors may be more suitable for cultured LESC therapy production.

Laser-assisted in-situ keratomileusis (LASIK) versus photorefractive keratectomy (PRK) for myopia

BACKGROUND

Myopia (also known as short-sightedness or near-sightedness) is an ocular condition in which the refractive power of the eye is greater than is required, resulting in light from distant objects being focused in front of the retina instead of directly on it. The two most commonly used surgical techniques to permanently correct myopia are photorefractive keratectomy (PRK) and laser-assisted in-situ keratomileusis (LASIK).

OBJECTIVES

To compare the effectiveness and safety of LASIK and PRK for correction of myopia by examining post-treatment uncorrected visual acuity, refractive outcome, loss of best spectacle-corrected visual acuity, pain scores, flap complications in LASIK, subepithelial haze, adverse events, quality of life indices and higher order aberrations.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 11), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to November 2012), EMBASE (January 1980 to November 2012), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to November 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 15 November 2012. We also searched the reference lists of the studies and the Science Citation Index.

SELECTION CRITERIA

We included randomised controlled trials comparing LASIK and PRK for the correction of any degree of myopia.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. We summarised data using the odds ratio and mean difference. We combined odds ratios using a random-effects model after testing for heterogeneity.

MAIN RESULTS

We included 13 trials (1135 participants, 1923 eyes) in this review. Nine of these trials randomised eyes to treatment, two trials randomised people to treatment and treated both eyes, and two trials randomised people to treatment and treated one eye. None of the paired trials reported an appropriate paired analysis. We considered the overall quality of evidence to be low for most outcomes because of the risk of bias in the included trials. There was evidence that LASIK gives a faster visual recovery than PRK and is a less painful technique. Results at one year after surgery were comparable: most analyses favoured LASIK but they were not statistically significant.

AUTHORS' CONCLUSIONS

LASIK gives a faster visual recovery and is a less painful technique than PRK. The two techniques appear to give similar outcomes one year after surgery. Further trials using contemporary techniques are required to determine whether LASIK and PRK as currently practised are equally safe. Randomising eyes to treatment is an efficient design, but only if analysed properly. In future trials, more efforts could be made to mask the assessment of outcome.

New clinical pathways for keratoconus

Pre-2000, the clinical management of keratoconus centred on rigid contact lens fitting when spectacle corrected acuity was no longer adequate, and transplantation where contact lens wear failed. Over the last decade, outcome data have accumulated for new interventions including corneal collagen crosslinking, intracorneal ring implantation, topographic phototherapeutic keratectomy, and phakic intraocular lens implantation. We review the current evidence base for these interventions and their place in new management pathways for keratoconus under two key headings: corneal shape stabilisation and visual rehabilitation.

Plastic compressed collagen as a novel carrier for expanded human corneal endothelial cells for transplantation

Current treatments for reversible blindness caused by corneal endothelial cell failure involve replacing the failed endothelium with donor tissue using a one donor-one recipient strategy. Due to the increasing pressure of a worldwide donor cornea shortage there has been considerable interest in developing alternative strategies to treat endothelial disorders using expanded cell replacement therapy. Protocols have been developed which allow successful expansion of endothelial cells in vitro but this approach requires a supporting material that would allow easy transfer of cells to the recipient. We describe the first use of plastic compressed collagen as a highly effective, novel carrier for human corneal endothelial cells. A human corneal endothelial cell line and primary human corneal endothelial cells retained their characteristic cobblestone morphology and expression of tight junction protein ZO-1 and pump protein Na+/K+ ATPase α1 after culture on collagen constructs for up to 14 days. Additionally, ultrastructural analysis suggested a well-integrated endothelial layer with tightly opposed cells and apical microvilli. Plastic compressed collagen is a superior biomaterial in terms of its speed and ease of production and its ability to be manipulated in a clinically relevant manner without breakage. This method provides expanded endothelial cells with a substrate that could be suitable for transplantation allowing one donor cornea to potentially treat multiple patients.

Stability of eyelid height after graded anterior-approach lid lowering for dysthyroid upper lid retraction

OBJECTIVE

To investigate the outcome of a modified anterior approach surgical procedure for the correction of primary upper eyelid retraction in thyroid eye disease.

METHODS

A retrospective review of 52 consecutive cases (in 32 patients) of anterior-approach graded upper lid lowering for the treatment of primary eyelid retraction, carried out at Moorfields Eye Hospital between 2006-2009 was conducted. Measurements of upper margin-reflex distance (MRD), upper lid skin crease height and skin fold height were taken from clinical records and photographs. A comparison between pre-operative and both early and late post-operative measurements was conducted, with a maximal follow-up of 12 months. Surgery was considered successful when all of the following criteria were met; an upper lid margin covering 0.5-1.5 mm of the superior cornea in the 12 o'clock position, smooth eyelid contour, skin crease height within 6-10 mm or upper lid skin fold within 2-5 mm of the lid margin, symmetry of lid position (difference in MRD of < 1 mm between both eyes) and patient satisfaction.

RESULTS

A successful outcome was achieved in 86.5% (45/52) of lids with a single procedure. For the whole group, the mean MRD was 7.0 mm pre-operatively and 3.6 mm at 1 month after surgery. The corresponding values from photographic estimates were 6.5 mm and 3.6 mm, respectively. These values remained stable over the maximum follow-up period of 12 months. Under-correction occurred in 6/52 (11.5%) lids, one of which had persistent lateral flare, whereas over-correction occurred in 1/52 (2%).

CONCLUSIONS

The described surgical approach produces reasonably predictable and stable outcome for upper eyelid lowering in patients with thyroid eye disease.

Endothelial keratoplasty versus penetrating keratoplasty for Fuchs endothelial dystrophy

BACKGROUND

Fuchs endothelial dystrophy (FED), first described by Ernst Fuchsis in 1910, is a condition in which there is premature degeneration of corneal endothelial cells. When the number of endothelial cells is reduced to a significant degree fluid begins to accumulate within the cornea. As a result the cornea loses its transparency and the individual suffers a reduction in vision. The only successful surgical treatment for this condition is replacement of part or all of the cornea with healthy tissue from a cadaveric donor. The established procedure, penetrating keratoplasty (PKP), has been used for many years and its safety and efficacy are well known. Endothelial keratoplasty (EK) is a relatively new surgical procedure and the safety and efficacy relative to PKP are unknown.

OBJECTIVES

The objective of this review is to collate information on the benefits and complications related to two surgical methods (PKP and EK) of replacing the diseased endothelial layer of the cornea with a healthy layer in people with FED.

SEARCH STRATEGY

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2011, Issue 2), MEDLINE (January 1950 to February 2011), EMBASE (January 1980 to February 2011), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to February 2011), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) and ClinicalTrials.gov (www.clinicaltrials.gov). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 6 February 2011.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing EK versus PKP for people (of any age and gender) who had been clinically diagnosed with FED. When assessing the primary and secondary outcome measures, only RCTs were included in the analysis. As per our protocol a description of data from non-randomised comparative studies is also reported. As RCTs may not detect differences in frequency of adverse events, when assessing these we included data from cohort studies with more than 50 participants and a follow-up of up to five years.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data.

MAIN RESULTS

The electronic searches identified one RCT, five non-randomised comparative studies and 34 cohort studies with a sample size of over 50 participants for inclusion. The RCT was conducted in the USA and included 28 eyes of 25 participants with FED. Although this is a very good RCT, there may be potential for bias due to lack of masking of assessors and possible selective reporting not being clearly reported. In this RCT, comparing EK versus PKP, best corrected visual acuity (BCVA) was similar at 24 months (PKP 0.20 ± 0.20 logMAR; EK 0.34 ± 0.35 logMAR; P = 0.23) and higher order aberrations (HOAs) (deviations of the performance of an optical system from the predictions of paraxial optics) were lower with EK. No other data were reported by the trial. Based on data obtained from both non-randomised comparative studies and individual cohort studies the endothelial rejection rate was between 5.3% and 23.2% for PKP and 2% and 4% for EK. However the mean follow-up duration in the EK cohort studies was noticeably shorter. The rate of EK graft dislocation requiring repositioning ranged from 3% to 63%, with the majority of studies having a rate of < 10%.

AUTHORS' CONCLUSIONS

There is no high quality evidence that EK is superior to PKP in the treatment of FED considering the studies that satisfied our primary and secondary outcome measures. One RCT demonstrated that HOAs are lower following EK and some lower quality evidence suggests that endothelial rejection episodes may be less with EK. These findings should be interpreted with caution as they are based on data with risk of biases. Further RCTs of visual and refractive outcomes needs to be performed in this field, comparing EK to PKP, with a larger sample size and at least five years of follow up. To avoid bias due to a surgeon's learning curve, procedures should be performed by experienced surgeons only. Quality of life and vision should also be evaluated. The risk of endothelial rejection will be difficult to address in the context of a RCT because of power considerations but large non-randomised comparative case series and corneal graft registry outcome data will be useful in this regard.

Simultaneous extrusion and intrusion of a scleral buckle in a patient with Marfan's syndrome

An Asian male in his late 50s with known Marfan's syndrome (MFS) presented with sudden deterioration in vision and loss of globe structure 13 years after the placement of a silicone scleral encircling band for the management of retinal detachment. Surgical exploration revealed simultaneous intrusion and extrusion of the encircling band resulting in globe perforation and collapse. This was managed by removal of the encircling band and a scleral patch graft over the defect. This case highlights that in patients with thin sclera, such as in MFS, scleral perforation is a potential complication that should be considered in patients undergoing scleral buckling. Management of this complication is also technically difficult because of impaired healing of the sclera in these patients.

Corneal stem cells in the eye clinic

INTRODUCTION OR BACKGROUND

Corneal opacity is a common cause of blindness. The majority of cases result from ulceration and scarring following infection or trauma, but in a proportion corneal epithelial stem cell (SC) deficiency leads to an inability to maintain a healthy corneal surface.

SOURCES OF DATA

This review includes systematic reviews and individual case series of treatments for corneal epithelial SC deficiency.

AREAS OF AGREEMENT

Two techniques such as transplantation of large segments of cornea from a healthy eye and ex vivo expansion of corneal SCs in the laboratory were compared. Both have merits and their clinical outcomes are similar. The smaller biopsy in the cell expansion approach has less risk for the donor eye, which is a significant advantage.

AREAS OF CONTROVERSY

Treatment algorithms for different aetiologies of SC failure are evolving. The proportion of true corneal epithelial SCs in ex vivo culture is unclear and it is unknown whether these cells survive long term.

GROWING POINTS

In this study, the optimum method of cell culture and transplantation is being intensively investigated.

AREAS TIMELY FOR DEVELOPING RESEARCH

Development of tissues using multiple cell types, genetic modification to treat hereditary corneal disorders and development of cell therapy for other eye diseases are future possibilities.

IL6 and the human limbal stem cell niche: a mediator of epithelial-stromal interaction

The corneal epithelium is maintained by the limbal epithelial stem cells (LESCs). In this study, an in vitro model is proposed for the investigation of cell-cell interactions involving LESC maintenance. Imaging of the limbal niche demonstrated close spatial arrangement between basal limbal epithelial cells within putative LESC niche structures and fibroblasts in the stroma. Interactions of the human limbal epithelial (HLE) cells and mitotically active human limbal fibroblasts (HLF) were studied for the first time in a serum-free in vitro model that simulated aspects of the limbal niche microenvironment. HLE cocultured in a ratio 3:1 with HLF exhibited enhanced expression of the putative stem cell markers ABCG2 and p63α and holoclones were preserved as shown by colony-forming efficiency assays, clonal analysis, and colony characterisation. Interleukin 6 (IL6) was found to be up-regulated in the 3.1SF system when compared to the HLE culture with growth-arrested fibroblasts and serum (gold standard system, GS). IL6 caused a time-dependent phosphorylation of STAT3 in HLE cells. STAT3 and IL6 inhibition in 3.1SF cultures significantly reduced HLE colony-forming efficiency, suggesting a previously undetected STAT3-mediated involvement of IL6 in the maintenance of HLE cells in a progenitor-like state.

Ex vivo cultured limbal epithelial transplantation. A clinical perspective

The term ex vivo cultured limbal epithelial transplantation (CLET) refers to the process of culturing a sheet of human limbal epithelium in the laboratory and transplanting this sheet back onto the limbal stem cell-deficient cornea of the same patient or another recipient. This emerging technology represents one of the earliest successes in regenerative medicine. CLET is, at present, best suited to patients who have unilateral total limbal stem cell deficiency arising from chemical injury and who are suitable for autologous cell culture and transplantation. Although the results of allogeneic cell transplantation are encouraging and superior to conventional stem cell transplantation techniques, insufficient follow-up precludes conclusions regarding the long-term outcomes. Other tissues, such as oral mucosal epithelium, are emerging as viable alternative sources of cells, especially for patients with bilateral disease.

Current Prospects for Adult Stem Cell–Based Therapies in Ocular Repair and Regeneration

Recent advances in stem cell biology have led to the exploration of stem cell-based therapies to treat a wide range of human diseases. In the ophthalmic field, much hope has been placed on the potential use of these cells to restore sight, particularly in those conditions in which other established treatments have failed and in which visual function has been irreversibly damaged by disease or injury. At present, there are many limitations for the immediate use of embryonic stem cells to treat ocular disease, and as more evidence emerges that adult stem cells are present in the adult human eye, it is clear that these cells may have advantages to develop into feasible therapeutic treatments without the problems associated with embryonic research and immune rejection. Here we discuss the current prospects for the application of various adult ocular stem cells to human therapies for restoration of vision.

The effect of amniotic membrane preparation method on its ability to serve as a substrate for the ex-vivo expansion of limbal epithelial cells

Human amniotic membrane (HAM) is employed as a substrate for the ex-vivo expansion of limbal epithelial cells (LECs) used to treat corneal epithelial stem cell deficiency in humans. The optimal method of HAM preparation for this purpose is unknown. This study evaluated the ability of different preparations of stored HAM to serve as substrates for LEC expansion ex-vivo. The effect of removing the amniotic epithelial cells (decellularisation) from HAM prior to seeding of LECs, the effect of glycerol cryopreservation and the effect of peracetic acid (PAA) sterilization and antibiotic disinfection were evaluated using different HAM test groups. Human LECs were cultured on each preparation and the following outcomes were assessed: confluence of growth, cell density, cell morphology and expression of the putative LESC markers deltaN-p63alpha and ABCG2. Removing amniotic epithelial cells prior to seeding of LECs resulted in a higher percentage of confluence but a lower cell density than intact HAM suggesting that decellularisation does not increase proliferation, but rather that it facilitates migration of LECs resulting in larger cells. Decellularisation did not affect the percentage of cells expressing the putative LESC markers deltaN-p63alpha (< or =4% in both intact and acellular groups) and ABCG2 (< or =3% in both intact and acellular groups). Glycerol cryopreservation of HAM resulted in poor morphology and a low proportion of cells expressing deltaN-p63alpha (< or =6%) and ABCG2 (< or =8%). HAM frozen at -80 degrees C in Hank's Balanced Salt Solution (HBSS) was superior, demonstrating excellent morphology of cultured LECs and high levels of deltaN-p63alpha (< or =68%) and ABCG2 (< or =62%) expression (p<0.001). The use of PAA or antibiotics to decontaminate HAM does not appear to affect this function. The variables affecting the ability of HAM to serve as a substrate for LEC expansion ex-vivo are poorly understood. The use of glycerol as a cryoprotectant impairs this ability whereas simple frozen HAM appears to work extremely well for this purpose.

Ex vivo expansion and transplantation of limbal epithelial stem cells

OBJECTIVE

To determine, using objective measures, the outcome of ex vivo cultured limbal epithelial stem cell (LESC) transplantation performed in compliance with good manufacturing practice using a novel culture system without 3T3 feeder cells.

DESIGN

Prospective, noncomparative, interventional case series.

PARTICIPANTS

Ten eyes of 10 patients with profound LESC deficiency arising from chemical injury (4 eyes), aniridia (3 eyes), ectodermal dysplasia (1 eye), Reiger's anomaly with Pax6 haploinsufficiency (1 eye), and unknown cause (1 eye).

METHODS

Allogeneic (7 eyes) or autologous (3 eyes) corneal LESCs were cultured on human amniotic membrane. Tissue was transplanted to the recipient eye after superficial keratectomy. Impression cytology and confocal microscopy were performed 6 months after surgery with clinical follow-up to 13 months. Success was defined as an improvement in the defined clinical parameters of LESC deficiency, an improvement in visual acuity, the restoration of a more normal corneal phenotype on impression cytology, and the appearance of a regular hexagonal basal layer of cells on corneal confocal microscopy.

MAIN OUTCOME MEASURES

Clinical parameters of LESC deficiency (loss of epithelial transparency, superficial corneal vascularization, epithelial irregularity, and epithelial breakdown), visual acuity, impression cytology and cytokeratin expression profiles, and in vivo confocal corneal confocal microscopy.

RESULTS

The success rate using this technique was 60% (autografts 33%, allografts 71%). All patients with a successful outcome experienced an improvement in visual acuity of >/=2 lines Snellen acuity. Preoperatively, CK3+ and CK19+ cells accounted for 12+/-2.4% (mean +/- standard error of the mean) and 80+/-2.15% of cells, respectively, whereas postoperatively these accounted for 69+/-6.43% (P<0.0001) and 30+/-6.34% (P<0.0001) of cells, respectively. Goblet cells accounted for 8+/-1.19% of cells preoperatively and 1+/-0.35% of cells postoperatively (P<0.0001).

CONCLUSIONS

These data demonstrate that it is possible to culture LESCs ex vivo in compliance with good manufacturing practice regulations. A set of objective outcome measures that confirm the efficiency of this technique in treating LESC deficiency is described. The widespread use of such standardized and objective outcome measures would facilitate a comparison between the different culture methods in use.

Transplantation of ex vivo cultured limbal epithelial stem cells: a review of techniques and clinical results

Ex vivo cultured limbal epithelial stem cells have been used successfully to treat corneal limbal stem cell deficiency. We identified 17 reports of the application of this novel cell-based therapy in humans. In addition we identified four reports of the use of culture oral mucosal epithelial cells to treat limbal stem cell deficiency. We examined these reports to discern the success rate, complication rate, visual outcome, whether there is an optimal technique and which patients are the most likely to benefit. We also discuss the different culture methods employed and the regulations governing cell banks that are providing this service. We found that the techniques used to cultivate and transplant cells varied, but that no individual method was clearly superior. The reported success rate is similar across all studies for both allografts and autografts. The clinical indications for this treatment are not clearly defined as indicated by the variety of disorders treated. Follow-up is limited and the long-term success rate is yet to be established. Nonetheless, we conclude that there is sufficient evidence to support the continued use and refinement of this procedure as a treatment for corneal stem cell deficiency.

TGFbeta stimulated re-epithelialisation is regulated by CTGF and Ras/MEK/ERK signalling

The complex mechanisms by which transforming growth factor beta (TGFbeta) regulate re-epithelialisation following injury of stratified epithelia are not fully understood. TGFbeta signals via binding to distinct receptors activating downstream effectors, including Smads which initiate transcription of target genes. However, studies have shown that TGFbeta can also signal independently of Smads through MAPK pathways, demonstrating the diversity of TGFbeta signalling. Connective tissue growth factor (CTGF) is strongly induced by and acts downstream of TGFbeta causing pathophysiology in tissues by inducing matrix deposition, conversion of fibroblasts into contractile myofibroblasts (e.g. dermis and corneal stroma) and stimulation of epithelial-to-mesenchymal transition (e.g. kidney and lung) all of which are known to cause fibrosis. However, a role for CTGF in epithelial cell function which does not involve direct contribution to fibrosis has not been demonstrated. We show for the first time that synthesis of CTGF in cultures of human corneal epithelial cells is induced by TGFbeta through the Ras/MEK/ERK MAPK signalling pathway and that this is required for re-epithelialisation to occur through cell migration. These data reveal a novel function for CTGF in the regulation of epithelial tissue repair beyond its established role in fibrosis, and further highlight the complexity of TGFbeta regulation of epithelial cell function.

Characterization of the limbal epithelial stem cell niche: novel imaging techniques permit in vivo observation and targeted biopsy of limbal epithelial stem cells

It is anticipated that stem cell (SC) therapy will enable the regeneration of diseased tissues and organs. Understanding SC niches is an essential step toward realizing this goal. By virtue of its optical transparency and physical separation of SC and transient amplifying cell compartments, the human cornea provides a unique opportunity to visualize and observe a population of adult stem cells, limbal epithelial stem cells (LESCs), in their niche environment. To date, the characteristics of the LESC niche have remained unclear. State-of-the-art imaging techniques were used to construct a three-dimensional (3D) view of the entire human corneal limbus and identify the structural characteristics of the LESC niche. Two distinct candidate LESC niche structures were identified. Cells within these structures express high levels of the putative limbal stem cell markers p63alpha and ABCG2; however, current methods cannot identify for certain which exact cells within this cell population are truly LESCs. These structures could be located and observed in vivo in normal human subjects, but not in patients with clinically diagnosed corneal LESC deficiency. The distribution of these structures around the corneal circumference is not uniform. Biopsies targeted to limbal regions rich in LESC niche structures yielded significantly higher numbers of LESCs in culture. Our findings demonstrate how adult stem cell niches can be identified and observed in vivo in humans and provide new biological insight into the importance of LESC niche structures in maintaining normal LESC function. Finally, the concept of targeted biopsy of adult SC niches improves stem cell yield and may prove to be essential for the successful development of novel adult stem cell therapies. Disclosure of potential conflicts of interest is found at the end of this article.

Limbal epithelial stem cell therapy

Restoring vision in patients suffering from previously intractable blinding ocular surface disease has become possible with the advent of techniques for ex vivo expansion and transplantation of limbal epithelial stem cells onto the cornea. This approach represents one of the few adult stem cell therapies presently in the clinic. This article highlights several key research areas where progress will be made to specifically understand the biology and therapeutic potential of limbal epithelial stem cells, which may have an applicability to the understanding of other adult stem cell populations.

Evidence for Superior Efficacy and Safety of LASIK over Photorefractive Keratectomy for Correction of Myopia

PURPOSE

To examine possible differences in efficacy and safety between LASIK and photorefractive keratectomy (PRK) for correction of myopia.

DESIGN

Meta-analysis/systematic review.

PARTICIPANTS

Patient data from previously reported prospective randomized controlled trials (PRCTs) and a systematic review of prospective case series in the Food and Drug Administration (FDA) clinical trials database.

METHODS

A comprehensive literature search was performed using the Cochrane Collaboration methodology to identify PRCTs comparing LASIK and PRK for correction of myopia. A meta-analysis was performed on the results of PRCTs. In parallel, a systematic review of prospective data from FDA case series of LASIK and PRK for correction of myopia was undertaken.

MAIN OUTCOME MEASURES

Key efficacy outcomes (uncorrected visual acuity [UCVA] > or = 20/20, +/-0.50 diopters [D] of the target mean refractive spherical equivalent) and safety outcomes (loss of > or =2 lines of best spectacle-corrected visual acuity [BSCVA], final BSCVA > or = 20/40, and final BSCVA < 20/25 where preoperative BSCVA was > or =20/20).

RESULTS

Seven PRCTs were identified comparing PRK (683 eyes) and LASIK (403 eyes) for correction of myopia. More LASIK patients achieved UCVA > or = 20/20 at 6 months (odds ratio, random effects model [95% confidence interval], 1.72 [1.14-2.58]; P = 0.009) and 12 months (1.78 [1.15-2.75], P = 0.01). Loss of > or =2 lines of BSCVA at 6 months was less frequent with LASIK (2.69 [1.01-7.18], P = 0.05). Data from 14 LASIK (7810 eyes) and 10 PRK (4414 eyes) FDA laser approval case series showed that more LASIK patients achieved UCVA of 20/20 or better at 12 months (1.15 [1.03-1.29], P = 0.01), significantly more LASIK patients were within +/-0.50 D of target refraction at 6 months (1.38 [1.26-1.50], P<0.00001) and 12 months (1.21 [1.08-1.36], P = 0.0009) after treatment, and loss of > or =2 lines of BSCVA at 6 months was less frequent with LASIK (2.91 [2.22-3.83], P<0.00001).

CONCLUSIONS

LASIK appears to have efficacy and safety superior to those of PRK. However, the data examined are from studies conducted > or =5 years ago. It is therefore unclear how our findings relate to present-day methods and outcomes. Further trials comparing contemporary equipment and techniques are needed to reevaluate the relative merits of these procedures.

Stem cell therapy delivery: treading the regulatory tightrope

The concept of stem cell therapy has engaged the attention of the public and scientists alike. Intensive research effort is focused upon understanding the biology and therapeutic potential of embryonic and adult stem cells, with the eventual goal of treating such pathologies as Parkinson’s disease, diabetes, neurological injury and degenerations and cancer. Ex vivo expansion and transplantation of limbal epithelial stem cells to the corneas to treat blinding ocular surface disease was one of the first stem cell therapies to successfully reach the clinic. However, limbal epithelial stem cell research and therapy delivery has remained largely within the noncommercial academic clinician–scientist environment from which it was originally pioneered. In our experience, gaining regulatory approval has been as great a hurdle as surmounting the scientific challenges of stem cell therapy. Based upon our model of delivering ‘accredited’ limbal epithelial stem cell therapy to patients in compliance with Good Manufacturing Practice and the new European Union Tissues and Cells Directive, we address the key regulatory questions. This may help colleagues who are developing innovative academic research-driven stem cell therapies regarding donor consent, raw materials, quality assurance, laboratory specification, indemnity and funding.

Photorefractive keratectomy (PRK) versus laser-assisted in-situ keratomileusis (LASIK) for myopia

BACKGROUND

Myopia (also known as short-sightedness or near-sightedness) is an ocular condition in which the refractive power of the eye is greater than is required, resulting in light from distant objects being focused in front of the retina instead of directly on it. The two most commonly used surgical techniques to permanently correct myopia are photorefractive keratectomy (PRK) and laser-assisted in-situ keratomileusis (LASIK).

OBJECTIVES

The aim of this review was to compare the effectiveness and safety of PRK and LASIK for correction of myopia.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2005, Issue 3), MEDLINE (1966 to September 2005), EMBASE (1980 to September 2005) and LILACs (1982 to 3 November 2005). We also searched the reference lists of the studies and the Science Citation Index.

SELECTION CRITERIA

We included randomised controlled trials comparing PRK and LASIK for correction of any degree of myopia. We also included data on adverse events from prospective multicentre consecutive case series in the Food and Drugs Administration (FDA) trials database (http//www.fda.gov/cdrh/LASIK/lasers.htm).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. Data were summarised using odds ratio and mean difference. Odds ratios were combined using a random-effects model after testing for heterogeneity.

MAIN RESULTS

This review included six randomised controlled trials involving a total of 417 eyes, of which 201 were treated with PRK and 216 with LASIK. We found that although LASIK gives a faster visual recovery than PRK, the effectiveness of these two procedures is comparable. We found some evidence that LASIK may be less likely than PRK to result in loss of best spectacle-corrected visual acuity.

AUTHORS' CONCLUSIONS

LASIK gives a faster visual recovery than PRK but the effectiveness of these two procedures is comparable. Further trials using contemporary techniques are required to determine whether LASIK and PRK are equally safe.

Chronic systemic hypoxia causes intra-retinal angiogenesis

Retinal hypoxia occurs in many conditions that cause vascular disease in the eye and is an important stimulus to new vessel formation. However, the adult retina can also become hypoxic when there is systemic hypoxaemia such as occurs in chronic lung diseases, congenital cardiac disease and residence at high altitude. Little is known about the adaptive responses of the retinal vasculature in such circumstances. Previous research in the retinopathy of prematurity model may not apply to the adult tissue given the different mechanisms controlling angiogenesis in developing and mature circulations. We tested the hypothesis that chronic systemic hypoxia leads to angiogenesis in the adult retinal circulation, in the absence of pre-existing vascular disease. Adult male Sprague-Dawley rats (n=9) were exposed to a fraction of inspired oxygen of 0.10 for 2 weeks while control animals (n=10) were exposed to room air. Stereological techniques were used to quantify the vascular volume, endothelial surface area and the total number of branch points of all blood vessels in the superficial retinal vascular plexus. The mean volume and endothelial surface area of these vessels were significantly greater in the hypoxic than in the control group. The mean number of blood vessel branch points was also significantly greater in the hypoxic group. Our findings demonstrate that chronic systemic hypoxia, in the absence of other pathological processes, causes angiogenesis in the adult rat retina and provide an in vivo model for investigating this important process in the adult retina, in particular pathways specific to this tissue.

Pars plana lensectomy for the management of ectopia lentis in children

BACKGROUND

Nontraumatic ectopia lentis arises from a variety of inherited disorders. It may also occur as an isolated abnormality in an otherwise healthy individual. Surgical intervention is necessary when lens subluxation causes a significant refractive error resulting in amblyopia.

PATIENTS AND METHODS

We report the results of pars plana lensectomy for nontraumatic ectopia lentis in 24 eyes of 13 patients and provide data on the merits of this surgical approach. better in 17 of 22 eyes and 6/12 or better in 19 of 22 eyes. Other than contact lens-related problems, there were no perioperative or postoperative complications.

CONCLUSIONS

Pars plana lensectomy is a safe, effective procedure for the management of ectopia lentis. Visual outcomes are excellent. These findings should encourage earlier surgery when indicated to prevent amblyopia and improve visual acuity.