Ammar Miri

Long-term Outcomes of Autolimbal and Allolimbal Transplants

OBJECTIVE To evaluate the long-term results of limbal stem cell transplantation (LSCT) in patients with ocular surface (OS) disease. DESIGN Retrospective consecutive cohort study. PARTICIPANTS Case records of 27 eyes of 26 patients (19 males and 7 females) who presented with unilateral or bilateral total limbal stem cell deficiency and treated at the Department of Ophthalmology were examined. METHODS All eyes that were treated with LSCT and that had at least 1 year follow-up were included. There were 12 autolimbal and 15 allolimbal transplants. Of the latter, 9 were from living related donors (LRDs) and 6 were from cadaver donors (CDs). A total of 9 eyes underwent LSCT and penetrating keratoplasty (PKP), and 11 eyes underwent LSCT and amniotic membrane transplantation (AMT). Cataract extraction with implant was carried out in 4 eyes. Some eyes had more than 1 associated procedure. Nine eyes had LSCT only. Patients with allolimbal transplants also received systemic immunosuppression. MAIN OUTCOME MEASURES Surgical success was measured by the duration for which a healthy corneal epithelium was maintained after LSCT. Visual success was measured by improvement in visual acuity (VA) in the operated eye during the follow-up period. RESULTS The follow-up period of all eyes was up to 119 months (mean 38+/-35.9 months, median 24 months). Survival of LSCT, as determined by the maintenance of healthy corneal epithelium until last follow-up, was seen in 22 eyes (82%). The surface failed within 3 months in 4 eyes (1 with LRD and 3 with CD) and after 43 months in the fifth patient (with CD). Subsequently, 6 eyes required PKP to achieve their maximum visual potential. The VA (measured in decimal fraction) improved over a period of 1 year from a mean of 0.121 (standard deviation [SD] 0.184) preoperatively to a mean of 0.313 (SD 0.348) postoperatively. CONCLUSIONS Limbal stem cell transplantation, in isolation or in combination with other procedures, is effective in improving corneal clarity and vision. Autografts have the best long-term outcome followed by LRD allografts. Cadaver donor allografts have a comparatively poor outcome. This may partly reflect the difference in case mix between unilateral and bilateral OS conditions.

Contemporary limbal stem cell transplantation – a review

Conjunctivalization of the cornea is the hallmark of limbal stem cell deficiency (LSCD). This is often associated with persistent corneal epithelial defects and a fibrovascular pannus. LSCD can be unilateral or bilateral and partial or total. In partial LSCD involving the visual axis sequential sector conjunctival epitheliectomy (SSCE) is a useful option. In total LSCD, transplantation of limbal tissue or of ex vivo expanded sheets is the mainstay. In unilateral cases autolimbal transplant is the procedure of choice. In bilateral cases living (related) and cadaver donors are considered. The former has the advantage of being fresh and can be human leucocyte antigen matched. Procedures for harvesting limbal tissue from living donors are identical. Different strategies are required for harvesting tissue from cadaver whole globes or sclero‐corneal rims. Recipient eye preparation requires removal of the fibrovascular tissue. Donor explants are generally sutured directly on the denuded recipient surface without the preparation of a ‘bed’ to fit the explant. It is imperative that inflammation is meticulously controlled before limbal transplantation especially if tissue from living donors is used. Limbal transplantation, with the exception of a corneal graft, should be the last surgical intervention planned. Meticulous postoperative care and treatment with antibiotics, steroids, artificial tears and autologous serum are required. With allografts long‐term immunosuppression is necessary. Limbal transplantation is contraindicated in the presence of severe dry eye. Despite its complexities limbal transplantation does significantly improve vision related quality of life. Autografts give the best results and living related donor grafts are next best. Majority of cadaver grafts fail in 5 years.

In vivo confocal microscopic findings in patients with limbal stem cell deficiency

Aim To describe in vivo confocal microscopy (IVCM) findings in patients with limbal stem cell deficiency (LSCD). Methods 23 eyes of 17 consecutive patients suffering from LSCD were included in this study. A detailed examination by IVCM was performed in addition to a routine slit-lamp biomicroscopy. Size and density of corneal epithelial and conjunctival epithelial cells on cornea were measured and statistically analysed using SPSS version 8.0 software. Results were compared with histology in select cases. Results Anatomical and morphological differences were observed between normal corneal cells and conjunctival epithelial cells on cornea. Size and density differences reached statistically significant levels between the normal corneal cells and the conjunctival epithelial cells on cornea (p<0.01). Goblet cells were visible throughout the conjunctivalised corneal epithelium in eight eyes. Several IVCM features could be correlated with histology in six of our patients. Conclusions A number of features were demonstrated by laser IVCM in patients presenting clinically with LSCD. Some of these features were corroborated with features observed on histological examination of tissue samples.

In vivo confocal microscopic features of normal limbus

Aim To describe in vivo confocal microscopy (IVCM) features of the limbus in normal eyes as related to the palisades of Vogts. Methods 46 eyes of 29 consecutive volunteers were recruited in this observational study. A detailed examination by IVCM was performed in addition to a routine slit-lamp biomicroscopy. Size and density of corneal and limbal epithelial cells were measured and statistically analysed using SPSS version 8.0 software. Results Anatomical and morphological features were noted between corneal and limbal cells. Size and density differences reached to significant levels (p<0.05). Different shapes of palisades of Vogt have been described clearly by confocal microscope. Cell-like structures were observed in the peripheral end of the palisades which might represent limbal stem cell crypts. Conclusions Laser IVCM can be used to establish the features of the normal limbus. The identified features demonstrate quantitative changes in the basal epithelium between the limbus and the central cornea and morphological differences between pigmented or non-pigmented studied subjects. Further studies should be performed to correlate with histology the possible crypts which were observed in this study.

Variations in amniotic membrane: relevance for clinical applications

The amniotic membrane (AM) has found several clinical applications for ophthalmic indications, in particular, those related to ocular surface (OS) diseases. Successful results have been reported after use in treatment of persistent corneal epithelial defects, bullous keratopathy, acute and late stages of chemical burns and OS inflammatory diseases such as Stevens Johnson syndrome and after excision of conjunctival lesions, besides others.1–3 The AM has a complex structure, and several layers have been described. Essentially, it is composed of a metabolically active epithelium, which rests on a basement membrane and an avascular stroma. The epithelium and the stroma contain several growth factors, cytokines and other metabolically active substances. The transforming growth factor (TGFb) and the epidermal growth factor (EGF) are major and important growth factors. Proinflammatory and anti-inflammatory cytokines, such as interleukin 6 (IL-6), IL-8, IL-10 and IL-1ra, metalloproteases and tissue inhibitors of metalloproteases, and others have also been described.3 4 The mechanism of action of the membrane is not precisely known. Much of its beneficial effect can be attributed to its role as a substrate or scaffold supporting cell growth, migration and adhesion.5 The actions …

Ex vivo confocal microscopy of human corneal nerves.

Aims To evaluate the distribution, morphometry and the postmortem changes of the central and peripheral human corneal nerves by exvivo laser-scanning confocal microscopy (EVCM). Methods 24 eyes from 14 cadavers were retrieved at different time intervals after death and examined by EVCM. Five regions were examined in each eye: central, superior, inferior, temporal and nasal. In each region, corneal nerve images were categorised according to their anatomical location in the cornea into sub-basal, stromal and limbal nerves. Five nerve parameters were measured: density, orientation, diameter, numbers and branching pattern. Results Exvivo confocal scanning of a motionless eye allows high quality imaging and tracking of corneal and limbal nerves. Stromal nerves from the sub-Bowmans plexus perforate the Bowmans zone and terminate in bulb-like structures, from each of which a leash of sub-basal nerves arises. Following death, sub-basal nerve parameters showed significant changes. The density decreased from 9.23±4.48 to 0.45±0.07 mm/mm2, the diameter from 4.01±0.81 to 2.08±0.20 μm, the numbers from 8.3 to 1.0 and branching pattern from 39.38% to 0% (p<0.05) from day 1 to day 5 postmortem. Stromal and limbal nerves showed no significant changes in their density and diameter. Conclusions This study establishes a direct link between sub-basal nerves and the sub-Bowmans nerves via distinct terminal bulbs. Limbal nerves are the thickest, are seen in all quadrants and can be traced to the corneal centre. The sub-basal nerve plexus rapidly degenerates after death but stromal and limbal nerves survive during the first five days after death.

Donor Site Complications in Autolimbal and Living-Related Allolimbal Transplantation

OBJECTIVE To study the long-term changes at donor sites and safety implications for donor eyes used for harvesting tissue for autologous and living-related donor limbal transplants. DESIGN Retrospective, observational, consecutive case series. PARTICIPANTS We examined 50 donor sites of limbal tissue belonging to 25 healthy eyes (23 human subjects). METHODS The corneas and limbus of donor eyes were assessed for symptoms and visual acuity and examined by slit-lamp biomicroscopy and in vivo confocal microscopy with particular emphasis on the donor sites and central cornea. MAIN OUTCOME MEASURES In the donor eyes, we assessed visual acuity, persistence of symptoms, stability of the corneal epithelium, and the clinical and microscopic changes that occurred at the donor sites. RESULTS Mean follow-up was 41±38 months (median, 24; range, 3-127). All eyes had symptoms of ocular discomfort up to 4 weeks postoperatively and remained asymptomatic thereafter. No patient reported subjective reduction in visual acuity. Mean best-corrected visual acuity (logarithm of the minimum angle of resolution fraction) preoperatively was 0.076±0.19 and postoperatively was 0.09±0.17 (P = 0.57). All donor sites showed re-epithelialization of the peripheral denuded limbus within 2 weeks. Observed complications were filamentary keratitis and subconjunctival hemorrhage in 4 eyes. In vivo confocal microscopy confirmed that the central corneal epithelium remained normal in all eyes. The re-epithelialized donor site was covered with conjunctival epithelium in 17 sites of 10 eyes and with corneal epithelium in 7 sites of 5 eyes. CONCLUSIONS Limbal donation of 2 clock-hours of the superior and inferior limbus with 3×3 mm of adjacent conjunctiva was a safe procedure in this group of patients, demonstrating stable vision and an intact corneal epithelium during the follow up period. Donor sites can be re-epithelized by multiple layers of either corneal or conjunctival epithelium and is associated with deep stromal scarring.

Profile of sight-threatening infectious keratitis: a prospective study.

Purpose:  To prospectively study patients presenting with sight‐threatening corneal ulcers with a view to identify the predisposing factors, causative organisms, clinical signs and treatment outcomes.

Organization of the Regenerated Nerves in Human Corneal Grafts

PURPOSE To examine by histopathology the degree of nerve regeneration in human corneal grafts and to determine the anatomic organization and morphology of the regenerated nerves. DESIGN Experimental laboratory investigation. METHODS Twelve corneal grafts from 12 patients (7 men and 5 women) aged 34-93 (mean, 66.9 years) were included. The most common indication for regrafting was late endothelial failure. The mean duration of graft survival was 6.41 years (range, 1-14 years). The freshly obtained specimens with a narrow rim of host tissue incorporating the graft-host junction were subjected to the acetylcholinesterase method for the demonstration of corneal nerves. RESULTS Subbasal nerves were found in 75% and 25% of the grafts at the periphery and center, respectively. They were mostly originated from the host subbasal nerves. Regenerated stromal nerves were detected in 83% of the specimens; half of them showed extension into the center of the graft. A lack of the normal link between the subbasal and stromal nerves was observed and almost all of the regenerated stromal nerves were found to remain within the stroma and did not contribute to the epithelial innervation. CONCLUSIONS A persistent anatomic disorganization of the corneal nerves in human grafts was found even 14 years after surgery. This could explain the significant reduction of corneal sensation reported in previous studies.

Intra-lesional 5 fluorouracil for the management of recurrent pterygium

AimRecurrence is the most common complication arising from pterygium surgery. The aim of this study was to investigate the effectiveness of 5 fluorouracil (5FU) in halting the recurrence of pterygium after surgical excision.MethodsA retrospective review of patients treated for pterygium recurrence was carried out. Patients with recurrent (secondary) pterygium were treated with multiple weekly intra-lesional injections of 0.1–0.2 ml (2.5–5 mg) 5FU post-operatively depending on the size of the recurrence. The treatment was started within 1 month from the date of recurrence. The time from surgery to start of recurrence, previous treatment modalities, and number of recurrences were documented. The number of injections required to induce arrest of progression and/or regression of vascularity and fleshiness of the pterygium and any complications related to 5FU treatment were examined.ResultsFifteen eyes from 14 patients with recurrent pterygium treated with intra-lesional 5FU injections were analysed. Three of the 15 eyes had undergone a secondary excision and 12 had undergone a primary excision. In all, 93.3% of patients showed regression of the fibrovascular tissue (thickness and vascularity) and arrest of progression following a dose of 0.1–0.2 ml (2.5–5 mg) 5FU. Twelve eyes required three injections or fewer, whereas one patient required eight injections. This beneficial effect was maintained over an average follow-up period of 17 months. No complications from 5FU were observed.ConclusionThe use of weekly intra-lesional 5FU injections for the treatment of recurrent pterygium is safe and effective in limiting the progression and inducing the regression of recurrent pterygium. The number of injections can be tailored according to clinical need.