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.

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.

Deep anterior lamellar keratoplasty on a previously failed full-thickness graft.

PURPOSE: To report a case of deep anterior lamellar keratoplasty (DALK) on a previously failed full-thickness graft in a case of herpetic keratitis. METHODS: A 70-year-old patient with a history of penetrating keratoplasty for herpetic keratitis performed 30 years ago presented with blurry vision in her left eye. She had corneal stromal scarring secondary to herpetic keratitis. The endothelium was spared. We performed a DALK with big-bubble technique. RESULTS: Postoperatively, corneal edema was noticed initially, which resolved in 3 months. Her best-corrected visual acuity is 6/12 in her left eye. CONCLUSION: DALK on a previous penetrating keratoplasty is a technical possibility when there is a functioning endothelium.

Is microbiological analysis of donor cornea transport culture media necessary?

PURPOSE: To investigate microbial contamination of the transport medium. Examination of corneoscleral rims is not included in this series. METHODS: Transport media of 63 consecutive grafts done at Tennent Institute of Ophthalmology, Glasgow, were collected for microbial examination. RESULTS: None of the culture plates showed any growth after prolonged culture, and microscopy was negative in 100% of cases. CONCLUSIONS: Routine culture of transport media may not be necessary.

Intravitreal bevacizumab and augmented trabeculectomy for neovascular glaucoma in young diabetic patients.

PURPOSE: To report two cases of young diabetic patients with intractable neovascular glaucoma (NVG) who were successfully managed with bevacizumab and mitomycin C-augmented trabeculectomy. RESULTS: Two young patients present with severe NVG secondary to diabetic proliferative retinopathy. The glaucoma was unresponsive to conventional medical therapy and complete panretinal photocoagulation. Both patients underwent augmented trabeculectomy with MMC and intravitreal injection of bevacizumab. Iris rubeosis resolved within 48 h. Both patients have a follow-up period of 6 months and the intraocular pressure (IOP) remain between 10-15 mmHg. CONCLUSIONS: Controlling IOP due to NVG in young diabetic patients is difficult and augmented trabeculectomy has a very high failure rate. The addition of intravitreal bevacizumab in the management of NVG particularly in young diabetic patients may improve the success rate of IOP control. It is known that bevacizumab retards neovascularisation. It may also be modulating wound-healing response as well. Bevacizumab may have a potential role in the surgical management of NVG.

The use of a "cheese-wire" suture in trabeculectomy.

AIM: To report a preliminary study on the safety and efficacy of the use of a cheese-wire suture in trabeculectomy. PATIENTS AND METHODS: The case notes of 32 eyes of 25 patients with medically uncontrolled glaucoma who underwent trabeculectomy with cheese-wire suture at Stobhill Hospital, Glasgow, UK, between July 2001 and September 2002 were studied retrospectively. Diagnoses included primary open angle glaucoma (n = 24), normal tension glaucoma (n = 3), angle closure glaucoma (n = 2), ocular hypertension (n = 1), angle recession glaucoma (n = 1) and combined mechanism glaucoma (n = 1). The mean presenting intraocular pressure (IOP) was 29.5 mm Hg and mean intraocular pressure before operation was 23.5 mm Hg OUTCOME MEASURES: Success was defined as lowering of IOP by at least 15% compared with IOP before removal. RESULTS: A total of 20 eyes (62%) underwent removal of the cheese-wire suture. 17 eyes (85%) underwent removal for therapeutic reasons (failing/failed blebs) and three eyes (15%) underwent suture removal as the suture loops were exposed. The timing of removal was between 2 weeks and 12 months following surgery. A successful outcome was seen in 12/17 (70%) eyes in the eyes that had therapeutic suture removal. 15 eyes had undergone previous surgical interventions (trabeculectomy n = 12, extracapsular cataract extraction n = 1 and laser peripheral iridotomies n = 2). Mean IOP before removal was 23.66 mm Hg and mean IOP immediately following removal was 11.33 mm Hg. Of the 32 eyes that underwent trabeculectomy with cheese-wire suture, 24 eyes had intraoperative mitomycin C and one eye had 5-fluorouracil. The remaining seven eyes did not have any antimetabolites. Early complications related to the surgical procedure included conjunctival haematoma in one eye (3%), corneal abrasion in one eye (3%), wound leak in five eyes (15%), shallow anterior chamber in one eye (3%), hyphaema in six eyes (18%), choroidal effusion in six eyes (18%) and raised IOP in two eyes (6%). Late complications of suture exposure occurred in three eyes (9%). Complications related to removal of the cheese-wire suture included suture breakage in two eyes (10%), hypotony in one eye (5%) and transient hyphaema in one eye (5%). CONCLUSION: The use of cheese-wire suture in trabeculectomy appears to be safe and may provide an alternative strategy in the management of bleb failure.

Pathogenesis, clinical features and management of recurrent corneal erosions.

Recurrent corneal erosions (RCE) are common. They are characterised by repeated episodes of pain, difficulty in opening the eyes, watering, and photophobia resulting from poor epithelial adhesion. In the majority of patients with RCE, trauma is the initiating factor. Epithelial, stromal, and endothelial corneal dystrophies have all been described in association with RCE. Other causes that may lead to RCE include chemical and thermal injuries, previous herpetic keratitis, meibomian gland dysfunction, ocular rosacea, diabetes mellitus, Salzmann's nodular degeneration, band keratopathy, previous bacterial ulceration, kerato-conjunctivitis sicca, and epidermolysis bullosa. The conditions that are associated with RCE can be either primary or secondary depending on whether the basement membrane complex abnormality is intrinsic or acquired. Primary types tend to be bilateral, symmetrical and develop in multiple corneal locations. The pathogenetic mechanism of this disorder is related to poor adhesion of the corneal epithelium to the underlying stroma. Excessive matrix metalloproteinase (MMP) activity may play a role in the pathogenesis. Although the majority of patients will respond to simple measures such as padding and antibiotic ointment, RCE resistant to simple measures require approaches that are more elaborate. The common goal of these approaches is to encourage proper formation of adhesion complexes between the epithelium and the stroma. The use of long-term contact lenses, autologous serum eye drops, botulinum toxin, induced ptosis, oral MMP inhibitors, diamond burr polishing of Bowman's membrane have been reported with varying degree of success in treating RCE. Anterior stromal puncture with insulin needles or Neodymium : aluminium-yttrium-garnet may enhance the epithelial adhesion to the basement membrane by scar formation and success rates of up to 80% have been reported in the treatment of recalcitrant RCE. Excimer laser photo-therapeutic keratectomy (PTK) is now a well-established treatment modality for RCE and is being used both safely and effectively. Partial ablation of Bowman's layer with PTK gives a smooth surface for the newly generating epithelium to migrate and form adhesion complexes. The pathogenesis, clinical features, and management options of this common disorder are discussed in this review article.

Application of reversed-phase liquid chromatography and prepacked C18 cartridges for the analysis of oxytetracycline and related compounds.

The reversed-phase (RP) chromatographic separation of oxytetracycline (OTC) 4-epioxytetracycline (4-epiOTC), alpha-apooxytetracycline (alpha-apoOTC), and beta-apooxytetracycline (beta-apoOTC) has been accomplished on an Inertsil C8 column at ambient temperature. Using the simplex method of solvent optimization, a 0.1 M ammonium acetate buffer (pH 3.0)-acetonitrile-tetrahydrofuran (72.5:12.5:15, v/v/v) mobile phase was found to give excellent separation of the compounds. OTC, 4-epiOTC, alpha-apoOTC and beta-apoOTC were resolved in 35 min with calculated detection limits of 40, 20, 50 and 140 ng/ml, respectively. Solid-phase extraction (using RP C18 cartridges) of OTC and OTC degradation compounds from distilled water and porcine muscle was tested at four concentration levels ranging from 200 to 2000 ng/ml (g); overall mean recovery of OTC from distilled water and porcine tissue was greater than 90% and 70%, respectively.