Kanna Ramaesh

Microbial contamination of preservative free eye drops in multiple application containers

Background/aims: The majority of eye drops used in the United Kingdom contain preservatives and are bottled in plastic containers. Preservative free drops are used to avoid ocular irritation and allergies in certain individuals. The aim of this study was to investigate the incidence of microbial contamination of preservative free drops dispensed from multiusage containers. Methods: Eye drop bottles were collected from patients attending the Tennent Institute of Ophthalmology outpatient and inpatient departments. The bottles were collected on day 3 (for inpatients) and day 7 (for outpatients) of use. The drops were inoculated onto different culture plates (chocolate agar, blood agar, fungal culture media, and enriched media) and the resulting microbial growth was identified using standard microbial identification techniques. Results: 95 eye drop bottles were collected, containing a variety of 10 different eye drops. Significant bacterial growth was found in eight bottles. In total, seven different types of organism were identified from the eye drops. The organisms identified were Staphylococcus aureus, coagulase negative staphylococcus, Bacillus spp, Serattia spp, Klebsiella oxytoca, Enterobacter cloacae, and alpha streptococcus. Staph aureus was the commonest microbial organism. Conclusion: Preservative free eye drops in multiple application containers are at risk of contamination by potentially pathogenic micro-organisms.

Traumatic wound dehiscence after penetrating keratoplasty-a cause for concern.

AimWe report the incidence, causes, characteristics, and the outcome of traumatic corneal graft ruptures in a tertiary referral centre in the UK.MethodA retrospective analysis of all graft ruptures secondary to trauma that were treated at our centre between 1999 and 2005 was undertaken. Statistical analysis of possible prognostic factors was undertaken using the Fishers test.ResultsNineteen eyes in 18 patients sustained eye trauma resulting in graft rupture (median age of 53 years; range 27–82; 15 men and four women). Seventeen cases were accidental and two were from violence. The median time interval between grafting and rupture was 8.3 months (range 3 days to 15 years). The 6-year incidence was 3.8%. All graft ruptures occurred at the host–graft junction and ranged from 45 to 270°. Iris prolapse/loss was noticed in 89% and lens loss in 53%. The most common posterior segment complication was vitreous loss (74%), followed by vitreous haemorrhage (32%) and retinal detachment (21%). Grafts with 180° or more of dehiscence were more likely to fail (P<0.001), had more extensive posterior segment damage, and a poorer visual outcome. Grafts without sutures had a more extensive dehiscence (P<0.01). Final visual acuity was worse than 6/60 in 58%.ConclusionsThe risk of traumatic corneal graft rupture is significant and is associated with a poor visual outcome. This fact needs to be clearly emphasised during preoperative counselling and protective measures encouraged.

Brimonidine for glaucoma

Importance of the field: Brimonidine is a drug used in the management of glaucoma throughout the world and is the most modern α2-adrenoceptor agonist available. This review comprehensively discusses the use of brimonidine for glaucoma. Areas covered in this review: A historical insight into the development of selective adrenergic glaucoma drugs is given, followed by a description of the mechanisms of action and a discussion of the main clinical trials investigating clinical applications. The safety of brimonidine is evaluated, and our expert opinion is provided on how brimonidine is used in our clinical practice. The most relevant literature on the role of brimonidine in glaucoma is discussed. What the reader will gain: A clear understanding of the role of brimonidine for glaucoma treatment, with an explanation of its efficacy, limitations and use in clinical practice. Take home message: Brimonidine is an effective drug for lowering intraocular pressure. It has potentially serious systemic effects in children, in whom it is contraindicated. Its use in adults is limited by its ocular side effects such as allergy. Brimonidine is, however, an important part of the range of intraocular pressure lowering drugs available to prescribers.

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

PurposeThe purpose of this study was to assess the endothelium of corneal grafts by in vivoconfocal microscopy (IVCM), and to evaluate an automated endothelial software system in comparison with a manual cell count and planimetry.Patients and methodsOverall, 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 instruments Nidek Advanced Vision Information System (NAVIS) software. The results were compared with planimetry as the reference method, and the agreement was assessed.ResultsThe mean (±SD) automated ECD was 2278±524 cells/mm2 (range 1167–3192 cells/mm2), whereas the manual cell count method gave significantly lower ECDs with a mean of 1213±677 cells/mm2 (range 218–2440 cells/mm2; P<0.001). The manual cell counts were also significantly lower than those by planimetry, with a mean ECD of 1617±813 cells/mm2 (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/mm2, whereas they were −1000 and +202 cells/mm2 when comparing the manual cell counts with planimetry.ConclusionFollowing 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.

Treatment of corneal cystine crystal accumulation in patients with cystinosis

Cystinosis is a rare autosomal recessive disorder characterized by the accumulation of cystine within the cells of different organs. Infantile nephropathic cystinosis is the most common and severe phenotype. With the success of renal transplantation, these patients are now living longer and thus more long-term complications within different organs are becoming apparent. Ophthalmic manifestations range from corneal deposits of cystine crystals to pigmentary retinopathy. With increasing age, more severe ocular complications have been reported. Photophobia is a prominent symptom for patients. With prolonged survival and increasing age, this symptom, along with corneal erosions and blepharospasm, can become debilitating. This review revisits the basic pathogenesis of cystinosis, the ocular manifestations of the disease, and the treatment of corneal crystals.

Therapeutic deep lamellar keratoplasty for corneal perforations.

Objectives/aimsCorneal perforation can be potentially blinding unless the integrity of the globe is restored quickly. Although penetrating keratoplasty (PK) may achieve this, it carries a high risk of endothelial rejection in inflamed eyes. Deep lamellar keratoplasty (DLK) may be an alternative option to PK in such eyes owing to its potential for a lower incidence of rejection. We report the efficacy of DLK in patients with corneal perforations.Patients and methodsFour patients underwent layer-by-layer DLK for noninfective corneal perforation, after measures such as the use of a bandage contact lens, tissue adhesive, and conjunctival pedicle flap had failed. The preoperative visual acuity was hand movements in one patient, 1/60 in two, and 6/60 in one. All four had iris incarcerated within the corneal perforations. SF6 gas (three patients) and air (one patient) were injected into the anterior chamber at the end of surgery.ResultsThe integrity of the globe was restored in all four patients with an improvement in visual acuity (6/60 in one and 6/36 or better in three). The mean follow-up time was 7 months. All four patients had clear corneas 3 months postoperatively, apart from the area of the original perforation. There was no recurrence of ulceration or perforation.ConclusionDLK is a safe and effective therapeutic measure in the management of patients with corneal perforations acting to preserve the integrity of the globe and restore vision.

Presence of free radicals in intracameral agents commonly used during cataract surgery

Background Free radicals are known to cause cellular damage and are present in ophthalmic preparations. Corneal defence mechanisms are bypassed in intra-ocular surgery. We evaluated commonly used intracameral agents to ascertain the presence of free radicals and investigate the possibility of anterior segment and endothelial toxicity. Methods Samples of 19 commonly used intracameral preparations were analysed for total free radical presence on an Instrument Laboratory IL600 using a Randox Kit for Total Antioxidant Status (RANDOX Laboratories Ltd, Crumlin, UK). Results Free radical concentrations for the 19 intracameral agents ranged from 0 to 3.59 mmol/l, with median value of 0.34 mmol/l (mean value 0.933±1.19 mmol/l). Phenylephrine had the highest presence of free radicals, which were considerably higher than those for 0.5% hydrogen peroxide at all tested dilutions. Other notable results included cefuroxime (0.61 mmol/l), 2% undiluted lidocaine (0.34 mmol/l) and bevacizumab (0.59 mmol/l). Conclusion The results indicate that free radicals are present in intracameral surgical agents and some are in the order of 0.5% hydrogen peroxide. The risks of endothelial damage must be considered when using multiple intracameral preparations in complicated cataract surgery. Free radicals in intracameral preparations may be a contributing cause in cases of toxic anterior segment syndrome.

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.

Molecular profile of organ culture-stored corneal epithelium: Lgr5 is a potential new phenotypic marker of residual human corneal limbal epithelial stem cells

Long-term preservation of corneal limbal epithelium may decrease its quality and change the molecular signature of the limbal epithelial stem cells. In this study we have investigated the molecular profile of isolated corneal epithelial cells that have been in storage for an extended time. Isolated cells were characterised by the expression profile of different cytokeratins and markers of squamous metaplasia (vimentin and α‑actin). Furthermore, we examined global markers of adult stem cells including p63α and ABCG2 but also LGR5 as a novel stem cell marker. Immunocytochemical staining and PCR analysis of p63α, ABCG2 and LGR5 revealed the existence of side-population cells with a stem-cell phenotype and maintenance of corneal limbal stem cell properties. LGR5 expression can be related to cellular stemness and can be considered as a new phenotypic marker of residual human corneal limbal stem cells. However, the existence of CK10 together with co-expressed α-actin and vimentin suggests that the corneas investigated were under oxidative stress and showed evidence of squamous metaplasia.

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

PurposeTo assess the agreement of the ‘polygonal’ variable frame cell count option on a confocal microscope after keratoplasty, with planimetry as the reference method.MethodsOne 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.ResultsPlanimetry provided a mean (±SD) endothelial cell density (ECD) of 1348±726 cells/mm2, a value that was very similar to that found by the polygonal method (1404±784 cells/mm2). The fixed-frame method provided lower cell counts with a mean ECD of 1026±610 cells/mm2 (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/mm2 (limits of agreement, LoA, of −222 and 339 cells/mm2). Manual counting underestimated the ECD with a mean difference of −320 cells/mm2 (LoA −814 and 173 cell/mm2).ConclusionFollowing 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.