EDTA chelation for symptomatic band keratopathy: results and recurrence.

PurposeTo identify causes of symptomatic band keratopathy, and assess the results and long-term recurrence rates following chelation with topical ethylene-diamine-tetra-acetic acid (EDTA).Patients and methodsA retrospective review of surgical logbooks identified patients managed by EDTA chelation for symptomatic band keratopathy from 2009 to 2015.ResultsWe identified 108 cases; 89 case notes were available for analysis. Most cases of band keratopathy were idiopathic (36%). The most commonly identified underlying diagnosis was long-term topical glaucoma therapy (27%). Median presenting visual acuity was 6/18 (range 6/6-NPL) with the visual axis affected in 97.8% of cases. Treatment involved corneal epithelium removal, recurrent application of topical EDTA, and subsequent debridement. The mean duration of the operation was 20 min (range 10-45). Mean initial follow-up time was 40 days, and the visual axis was clear in 97.8%. Visual acuity was maintained or improved in 79.8%, with 13.5% improving by two lines or more. The mean length of follow-up was 581 days (median 374, maximum 2438). Twenty-five eyes (28.1%) showed localised recurrence of calcium with a mean time of 546 days (median 374), but only four cases required repeat EDTA chelation. The median time between operations was 430 days. Thirty-two per cent of the recurrence cases were associated with hypotony or chronic presence of silicone oil.ConclusionsChelation of calcium with topical EDTA is a safe and effective treatment for band keratopathy. Visual acuity improves in most eyes and while the rate of recurrence is moderate, the need for retreatment is low (4.5% overall).

Differentiation and molecular profiling of human embryonic stem cell-derived corneal epithelial cells.

It has been suggested that the isolation of scalable populations of limbal stem cells may lead to radical changes in ocular therapy. In particular, the derivation and transplantation of corneal stem cells from these populations may result in therapies providing clinical normality of the diseased or damaged cornea. Although feasible in theory, the lack of donor material in sufficient quantity and quality currently limits such a strategy. A potential scalable source of corneal cells could be derived from pluripotent stem cells (PSCs). We developed an in vitro and serum-free corneal differentiation model which displays significant promise. Our stepwise differentiation model was designed with reference to development and gave rise to cells which displayed similarities to epithelial progenitor cells which can be specified to cells displaying a corneal epithelial phenotype. We believe our approach is novel, provides a robust model of human development and in the future, may facilitate the generation of corneal epithelial cells that are suitable for clinical use. Additionally, we demonstrate that following continued cell culture, stem cell-derived corneal epithelial cells undergo transdifferentiation and exhibit squamous metaplasia and therefore, also offer an in vitro model of disease.

Xerophthalmia--a potential epidemic on our doorstep?

PURPOSE: Xerophthalmia refers to the ocular manifestations associated with vitamin A deficiency, including xerosis, keratomalacia, nyctalopia and Bitot's spot. Hypovitaminosis A is well-recognised in developing countries, but is rare in the developed world. Most cases in the latter relate to fat malabsorption. Conditions in which vitamin A metabolism or storage is deranged (chronic liver disease, including alcoholism) are also aetiologies. We wanted to see whether this was common in our department. METHODS: Oral vitamin A supplements were given to patients who presented with hypovitaminosis A. RESULTS: All patients were found to have hypovitaminosis A on biochemical testing and responded dramatically to oral vitamin A supplementation, resulting in an improved final visual outcome. DISCUSSION: This series demonstrates that prompt recognition and treatment of xerophthalmia can lead to rapid recovery and avert significant visual morbidity. The prevalence of xerophthalmia is likely to increase in the developed world largely owing to alcoholic liver disease. It is thought by some that we are on the verge of a potential epidemic. We hope that by increasing the profile of this important public health issue, we may be able to influence future prevalence of hypovitaminosis.

New insight into non-healing corneal ulcers: iatrogenic crystals.

AIMS: To characterise and correlate crystalline precipitations implicated in non-healing corneal ulceration in two patients with a previous history of acanthamoeba keratitis. MATERIALS AND METHODS: Persistence of acanthamoeba and secondary bacterial infection was excluded with negative corneal scrapes. Confocal microscopy identified crystal-like deposits within the corneal stroma. To investigate possible precipitating combinations, all concurrent treatments at the time of presentation were mixed in wells, with observation of precipitate formation. Precipitates were observed with phase-contrast microscopy, and subsequently characterised via crystallography techniques and electrospray ionisation mass spectrometry. RESULTS: Combinations of dexamethasone 0.1% minims and chlorhexidine gluconate 0.2% formed an amorphous material characterised by electrospray ionisation mass spectrometry as an insoluble chlorhexidine salt. Combinations of chloramphenicol drops and timolol 0.5% formed a crystal identified via X-ray crystallography as santite (K(B5O6(OH)4).(H2O)2). This is a borate mineral identified in nature, arising from thermal springs, but never reported in biological tissues. Clinical improvement was observed following the cessation of the implicated precipitating combinations. CONCLUSION: Our observations suggest iatrogenic precipitate formation, with a potential deleterious effect upon healing. The substrates for these precipitates include several frequently prescribed topical ophthalmic treatments. These findings shed new light on the aetiopathogenesis of non-healing corneal ulceration, and have broad implications on topical prescribing for this challenging condition.

Catatrac: a novel red light-emitting diode device for screening cataracts in the developing world.

BACKGROUND/AIMS: The purpose of this study was to critically evaluate the Catatrac device as a potential tool for rapid cataract screening in the developing world. METHODS: Patients attending the day case unit at Gartnavel General Hospital for routine cataract surgery were recruited into the study, and divided into two groups: those with mild cataracts with LogMAR acuities <0.48, and those with advanced cataracts with LogMAR acuities ≥0.48. The subjects were examined without pharmacological dilation in a dimly lit room independently by two nurses. Each patient was then examined by an ophthalmologist with a slit lamp, after dilation. If present, cataracts were graded objectively according to the LOCS III classification system. RESULTS: One hundred and twenty-two eyes of 73 patients were screened for the presence or absence of cataract using the Catatrac device. Thirty-nine eyes had mild cataracts, 43 eyes had advanced cataracts, and there were 40 control eyes with no cataracts. For detecting advanced cataracts, the two nurses using the Catatrac device had a specificity of 95.0%, a sensitivity between 86.0 and 93.0%, and κ values between 0.81 and 0.88 for agreement with slit lamp assessment. For detecting mild cataracts the two nurses using the Catatrac device again had a specificity of 95%, sensitivity of 71-84.6%, and κ values between 0.67 and 0.80 for agreement with slit lamp assessment. Interobserver agreement between the two nurses had a κ value of 0.61 for mild cataract and 0.74 for advanced cataract. CONCLUSION: The Catatrac device has a high specificity, sensitivity, and interobserver agreement for advanced cataracts. Although having a slightly lower sensitivity for mild cataracts, the authors believe that this study has demonstrated that it may be a low cost and easy to use device for rapid screening of visually significant cataracts in the developing world.

The effect of pH, dilution, and temperature on the viscosity of ocular lubricants--shift in rheological parameters and potential clinical significance.

OBJECTIVE: To investigate the effect of temperature, dilution, and pH on the viscosity of ocular lubricants. DESIGN: Laboratory based investigation of viscosity. PARTICIPANTS: No human subjects. METHODS: Hypromellose 0.3%, sodium hyaluronate 0.4%, carboxymethylcellulose sodium 0.5%/glycerin 0.9%, and carmellose sodium 0.5% were investigated. Ostwald capillary viscometers were utilised for viscosity measurements. The kinematic viscosity of each lubricant was tested quantitatively from 22 to 40 °C, and over a pH range of 5-8 under isothermal conditions. The kinematic viscosity of each eye drop was also tested under dilution by varying the mass fraction of each eye drop under isothermal conditions. MAIN OUTCOME MEASURE: Changes in kinematic viscosity. RESULTS: Hypromellose 0.3% had an initial pH of 8.34, while the other lubricants had a pH close to neutral. From 22 to 35 °C, the kinematic viscosity of sodium hyaluronate 0.4 fell by 36% from 37.8 to 24.4 mm(2)/s, carboxymethylcellulose sodium 0.5%/glycerin 0.9% fell by 35% from 16.98 to 11.1 mm(2)/s, hypromellose fell by 37% from 6.89 to 3.69 mm(2)/s, and carmellose sodium 0.5% fell by 25% from 2.77 to 1.87 mm(2)/s. At 32 °C only sodium hyaluronate 0.4%, and carboxymethylcellulose sodium 0.5%/glycerin 0.9% retained sufficient kinematic viscosity to maintain precorneal residence. Kinematic viscosities of all the topical lubricants were unaffected by pH but decreased significantly with dilution. CONCLUSIONS: This study suggests that currently used ocular lubricants have limited bioavailability due to reductions in viscosity by temperature and dilutional changes under physiological conditions. Developing lubricants with stable viscosities may maximise therapeutic efficacy.

Effects of N-acetylcysteine on matrix metalloproteinase-9 secretion and cell migration of human corneal epithelial cells.

BACKGROUND: Matrix metalloproteinase-9 (MMP-9) secreted by corneal epithelial cells has a role in the remodelling of extracellular matrix and migration of epithelial cells. Elevated levels of MMP-9 activity in the ocular surface may be involved in the pathogenesis of corneal diseases. N-acetylcysteine (NAC) has been used to treat corneal diseases, including recurrent epithelial erosions. In this study, its effects on the MMP-9 secretion and human corneal epithelial (HCE) cell migration were evaluated in vitro. METHODS: Confluent HCE cell cultures were treated with 0-20 mM NAC, and tested for MMP-9 secretion and epithelial cell migration by gelatin zymography and scratch wound assay, respectively. Comparisons between different treatment groups were made using analysis of variance, followed by multiple pairwise comparisons. RESULTS: Twenty mM NAC inhibited the secretion of MMP-9 significantly. Cell migration, assessed after 24 h of wounding, showed a highly significant dose-dependent inhibitory effect. CONCLUSIONS: This study shows that NAC reduces MMP-9 production by HCE cells and inhibits cell migration in vitro. This information helps to elucidate the mechanisms by which NAC may be beneficial therapeutically and suggests that NAC may be useful for managing corneal erosions and related conditions.

Assessment of a variable frame (polygonal) method to estimate corneal endothelial cell counts after corneal transplantation.

PURPOSE: To assess the agreement of the 'polygonal' variable frame cell count option on a confocal microscope after keratoplasty, with planimetry as the reference method. METHODS: One hundred clear corneal grafts of 83 patients attending the cornea clinic at Gartnavel General Hospital in Glasgow underwent slit-scanning in vivoconfocal microscopy. Endothelial cell images were assessed with the Nidek Advanced Vision Information System (NAVIS), using the polygonal variable frame and the manual fixed-frame methods. Planimetry was used as the reference. The agreement between methods was assessed by Bland-Altman analysis. RESULTS: Planimetry provided a mean (± SD) endothelial cell density (ECD) of 1348 ± 726 cells/mm(2), a value that was very similar to that found by the polygonal method (1404 ± 784 cells/mm(2)). The fixed-frame method provided lower cell counts with a mean ECD of 1026 ± 610 cells/mm(2) (P<0.001). When compared with the reference ECD, the polygonal method overestimated the ECD only very slightly with a mean difference of 58 cells/mm(2) (limits of agreement, LoA, of -222 and 339 cells/mm(2)). Manual counting underestimated the ECD with a mean difference of -320 cells/mm(2) (LoA -814 and 173 cell/mm(2)). CONCLUSION: Following keratoplasty, endothelial cell counts with the NAVIS polygonal method are in good agreement with planimetry. The 'polygonal' option is proposed as the method of choice for clinical applications with this confocal microscope and a good compromise between reliability and ease of use.

Free radicals and the pH of topical glaucoma medications: a lifetime of ocular chemical injury?

INTRODUCTION: Preservatives in ophthalmic preparations are known to cause ocular surface damage. Excipients can also contribute to oxidative stress in the compromised ocular surface. We evaluated commonly used topical glaucoma medications to ascertain pH levels and the intrinsic presence of free radicals. METHODS: Samples of 27 topical glaucoma preparations were analysed for total free radical presence using a Randox Kit for total antioxidant status. Analytical grade indicator paper was used to ascertain pH levels. RESULTS: Free radical concentrations for these 27 glaucoma preparations ranged from 0 to 4.54 mmol/l, with a median value of 0.66 mmol/l (mean value of 0.662 mmol/l, SD 0.839). Levels of pH ranged from 4.0 to 7.4, with a median value of 6.5 (mean 6.252, SD 0.826). There was no evidence of a direct correlation between these two variables (r=0.232, P=0.275). CONCLUSION: This study is the first to document the range of pH and concentrations of free radicals intrinsically present in commonly used glaucoma medications. Long-term exposure to preservatives, free radicals, and pH levels could all contribute to ocular surface damage. The effect of excipients could be responsible for patient intolerance when changing products in the compromised ocular surface.

Changing trends in keratoplasty in the West of Scotland: a 10-year review.

BACKGROUND/AIMS: To review the indications and types of keratoplasty performed in the West of Scotland between 2001 and 2010. METHODS: A retrospective analysis of the histopathological diagnoses of all corneal buttons submitted to the regional Ocular Pathology Laboratory (Glasgow, UK) between January 2001 and December 2010 was performed. RESULTS: Between 2001 and 2010, a total of 921 keratoplasties were performed in the West of Scotland. These included 646 (70.1%) penetrating keratoplasties and 275 (29.9%) lamellar keratoplasties (LK). Keratoconus (n=264, 28.7%) was the leading indication for keratoplasty, followed by graft failure (n=177, 19.2%), Fuch's endothelial dystrophy (n=124, 13.5%), keratitis (n=106, 11.5%), pseudophakic/aphakic bullous keratopathy (n=88, 9.6%), endothelial failure (n=67, 7.3%), non-Fuch's corneal dystrophies (n=21, 2.3%), trauma (n=19, 2.0%), autoimmune/inflammatory diseases (n=16, 1.7%) and others (n=39, 4.2%). A significant increase in the proportion of LK over penetrating keratoplasty was observed during this 10-year period: from 14.1% LK (2001-2005) to 40.4% LK (χ(2)=71.78, p value<0.001). CONCLUSION: Keratoconus was the leading indication for keratoplasty in the West of Scotland. Both anterior LK and endothelial keratoplasty seemed to show an emerging trend as the procedures of choice for dealing with anterior and posterior corneal pathologies, respectively.

In vivo confocal microscopy of the corneal endothelium: comparison of three morphometry methods after corneal transplantation.

PURPOSE: The purpose of this study was to assess the endothelium of corneal grafts by in vivo confocal microscopy (IVCM), and to evaluate an automated endothelial software system in comparison with a manual cell count and planimetry. PATIENTS AND METHODS: Overall, 40 corneal grafts (20 deep anterior lamellar keratoplasties (DALKs) and 20 penetrating keratoplasties (PKs)) were assessed by scanning-slit IVCM. The endothelial cell density (ECD) was estimated with the automated and the manual cell count method of the instrument's Nidek Advanced Vision Information System (NAVIS) software. The results were compared with planimetry as the reference method, and the agreement was assessed. RESULTS: The mean (±SD) automated ECD was 2278±524 cells/mm(2) (range 1167-3192 cells/mm(2)), whereas the manual cell count method gave significantly lower ECDs with a mean of 1213±677 cells/mm(2) (range 218-2440 cells/mm(2); P<0.001). The manual cell counts were also significantly lower than those by planimetry, with a mean ECD of 1617±813 cells/mm(2) (range 336-2941, P<0.001). Bland-Altman analyses indicated that the limits of agreement (LoA) between the automated and the planimetry method were -671 and +1992 cells/mm(2), whereas they were -1000 and +202 cells/mm(2) when comparing the manual cell counts with planimetry. CONCLUSION: Following keratoplasty, the NAVIS automated method is likely to overestimate endothelial cell counts due to oversegmenting of the cell domains. Automated ECDs are substantially higher than those by the manual counting method or planimetry. The differences are considerably larger post-keratoplasty than for normal corneas, and the methods should not be used interchangeably.

Surgical management of healed hydrops: a novel modification of deep anterior lamellar keratoplasty.

PURPOSE: The purpose of this case series was to evaluate the effectiveness of modified deep anterior lamellar keratoplasty in eyes with scarring secondary to hydrops associated with keratoconus. METHODS: Four patients underwent modified deep anterior lamellar keratoplasty. This was performed by controlled air injection and layer-by-layer dissection of the corneal stroma. The corneal stroma was dissected up to 95% thickness using a Beaver blade. The host Descemet membrane (DM) (4 mm in diameter) that was incorporated in the scar was excised. The DM and the endothelium from the donor button were removed, and the graft was applied to the recipient bed. Twenty percentage sulfur hexafluoride gas was injected to tamponade the host DM to the donor cornea. The graft was sutured with 10-0 monofilament nylon. An amniotic membrane dressing was applied. RESULTS: The preoperative visual acuity was between counting fingers to 6/36. Six weeks postoperatively, the grafts were clear. At 1-year follow-up, the best-corrected visual acuity was 6/12 or better in all patients. CONCLUSION: Modification of deep anterior lamellar keratoplasty may be an effective alternative to penetrating keratoplasty in eyes with corneal scarring because of previous hydrops.

Histopathological changes of cornea in long-term sympathetic ophthalmitis.

PURPOSE: To report the histopathological changes occurring in the cornea in sympathetic ophthalmitis. METHODS: Observational case series of 3 patients with sympathetic ophthalmitis who were treated with penetrating keratoplasty. We report the histopathological features of the cornea. RESULTS: In all 3 cases, the epithelium was edematous and bullous with extensive loss of the Bowman layer and calcification of the superficial stroma in all the 3 eyes. The deep stroma was unremarkable in appearance. Descemet membrane showed thickening in 2 of the corneas with nodular excrescences and folds noted in 1 of the specimens. The endothelium was attenuated with some residual cells containing pigment granules in 1 case. CONCLUSIONS: Endothelial loss and development of bullous keratopathy associated with band keratopathy are predominate histopathological features of the cornea. These changes are nonspecific and reflect a chronic anterior uveitis.

The outcome of deep anterior lamellar keratoplasty in herpes simplex virus-related corneal scarring, complications and graft survival.

AIMS: To determine the visual outcome, graft survival and complications after deep anterior lamellar keratoplasty (DALK) in patients with herpes simplex virus (HSV)-related corneal scarring. METHODS: A retrospective analysis of the patients who had DALK for HSV-related corneal scarring between January 2004 and February 2007 was performed. Mean follow-up was 30 months (range 16-48 months). The statistical significance of host corneal vascularisation was determined using Fisher's exact test. RESULTS: There were 18 eyes from 18 patients and the mean age was 57 years. Preoperative visual acuity ranged from hand movements (HM) to 6/12. Fifty per cent of the eyes achieved visual acuity of 6/12 or better postoperatively. Six eyes (33%) had recurrence of HSV-related inflammation, eight eyes (including four eyes with recurrence of HSV-related inflammation) developed graft rejection and four eyes (including two eyes with recurrence of HSV-related inflammation) had bacterial keratitis. The graft survival rate was 83%. Three eyes developed glaucoma and one eye required trabeculectomy. Immunohistochemistry revealed that HSV was focally positive or equivocal in four recipient corneal buttons, and transmission electron microscopy showed intracellular HSV virions in two of them. CONCLUSIONS: This is the largest series of DALK for herpetic corneal scarring that shows a comparable visual outcome and better graft survival rate than penetrating keratoplasty. There is significant risk of recurrence of HSV-related inflammation and graft rejection that requires timely recognition and adequate management.

Observation of the in vivo movement of host keratocytes into donor tissue following corneal graft; a novel technique.

BACKGROUND/AIMS: The cornea is a highly cellular structure that exists in a dynamic state of cell loss, renewal and replacement. The limbus contains corneal epithelial stem cells. The progenitor or stem cell of the keratocyte remains poorly defined. The authors sought to investigate the in vivo movement of corneal stromal and epithelial cells using a chromosome in situ hybridisation (CISH) technique on human tissue. METHODS: Four explanted sex-mismatched human corneal buttons were studied using the CISH technique to identify corneal epithelial and keratocyte cells containing the Y chromosome. Keratocyte identity and lack of infiltrating inflammatory cells were confirmed by immunohistochemistry. The sex mismatch of donor (XX) and host (XY) suggested any identified Y chromosomes cells were of host origin having migrated into the donor tissue. RESULTS: Host corneal epithelial cells were identified in all four buttons, and corneal stromal keratocytes were present in three of the four specimens in the central corneal area. CONCLUSION: Defining the corneal cell movements and the location of the progenitor or stem cells has important clinical implications. This study has successfully used the CISH technique to demonstrate the in vivo centripetal movement of corneal stromal keratocytes and epithelial cells. The CISH technique may allow further investigation of the corneal stromal dynamics using archival tissue.