John Kenneth George Dart

Acanthamoeba keratitis in England and Wales: incidence, outcome, and risk factors

AUTHOR:e-mail address please Aim: To determine the incidence, regional variation in frequency, outcome, and risk factors for acanthamoeba keratitis (AK) in England and Wales. Methods: AK cases presenting from 1 October 1997 to 30 September 1999 were identified by the British Ophthalmic Surveillance Unit active reporting system. Clinical and patient postal questionnaire data were analysed. Results: 106 reported cases met study criteria. The annual incidence for the 2 years was 1.26 and 1.13 per million adults and, for contact lens (CL) wearers, 21.14 and 17.53 per million. There was marked regional variation in incidence (0 to 85.13 per million adult CL wearers), with CL wearers in the south having a ninefold increased risk of AK compared with those resident in the north (95% confidence limits: 2.2–38.9, p<0.0001), and a threefold increased risk with hard as opposed to soft domestic water (95% confidence limits: 1.73 to 6.58, p<0.001). Treatment and outcome data were similar to those previously reported. 93/106 (88%) patients were CL wearers. Among these, 46/77 (60%) were disinfecting irregularly, and 20/63 (32%) had been swimming in CLs. One step hydrogen peroxide and chlorine release soft CL (SCL) disinfection systems were significantly over-represented among the cases. Among SCL users, one or more previously established risk factors for AK were identified in 50/55 (91%) patients. Conclusions: The incidence was considerably higher than most previous estimates, and was static. The geographical variation in incidence may be partly related to the increase in risk associated with hard water. The fact that water quality can have such an effect on the risk of AK suggests that many CL wearers must be letting tapwater come into contact with their lenses or storage cases. Improved education for CL wearers and practitioners about hygiene practice and the variable efficacy of contact lens systems could be expected to reduce the incidence of this disease.

Treatment of Acanthamoeba Keratitis with Polyhexamethylene Biguanide

Polyhexamethylene biguanide (PHMB) is a polymeric biguanide disinfectant that has not previously been used in the treatment of infection. Six patients with confirmed Acanthamoeba keratitis were treated with PHMB 0.02%. All patients had uncontrolled keratitis refractory to therapy with multiple conventional antiamebic agents. The rationale for use and the dose of PHMB was determined by in vitro sensitivity testing of the Acanthamoeba corneal isolates to the drugs available for use. Trophozoite forms were sensitive to most agents. Only PHMB was cysticidal at low concentrations in all cases. Sensitivity to the other drugs, including propamidine, showed wide variation. In 5 of 6 cases, complete resolution of inflammation followed the introduction of PHMB. Toxicity to the ocular surface was not evident with PHMB, unlike propamidine or neomycin. The reasons for the treatment failure in one case, despite cyst sensitivity to both PHMB and propamidine, are not clear. PHMB is a promising new treatment for this infection.

Anterior chamber flare after trabeculectomy and after phacoemulsification

AIMS To evaluate and compare prospectively the anterior chamber inflammatory response after phacoemulsification cataract surgery and after trabeculectomy with peripheral iridectomy. METHODS Anterior chamber inflammation was measured using the Kowa FM-500 laser flare meter in 131 patients undergoing trabeculectomy and 148 patients undergoing phacoemulsification cataract extraction with intraocular lens implantation. Flare was measured before surgery and on each postoperative visit up to 12 months. RESULTS Before surgery there was no significant difference in flare readings between the two groups. Following trabeculectomy flare returned to baseline levels 4 weeks after surgery, while following phacoemulsification cataract extraction it remained significantly higher at week 6 (p<0.006) and month 3 (p<0.05). CONCLUSIONS Anterior chamber inflammation is more prolonged after cataract surgery than after trabeculectomy. This may have implications for the timing of trabeculectomy in relation to cataract surgery.

Blepharokeratoconjunctivitis in children: diagnosis and treatment

Aim: Blepharokeratoconjunctivitis (BKC) is a poorly described entity in children. This study characterises this syndrome in childhood and evaluates epidemiology, clinical grading, and treatment strategies. Methods: 44 children (20 white, 22 Asian, 2 Middle Eastern, median age 5.4 (range 1–14) years) with a diagnosis of BKC were followed for a median of 7 years. Diagnostic criteria included recurrent episodes of chronic red eye, watering, photophobia, blepharitis including recurrent styes or meibomian cysts, and a keratitis. Clinical features were graded as mild, moderate, or severe. The lids and conjunctiva were cultured. The treatment regimen incorporated lid hygiene, topical and/or systemic antibiotics, and topical corticosteroids. Results: The disease was most severe in the Asian and Middle Eastern children (p <0.001), who had a statistically higher risk of subepithelial punctate keratitis (p = 0.008), corneal vascularisation (p <0.001), and marginal corneal ulcerations (p = 0.003), than the white group. 15 children had culture positive lid swabs. Most children had a reduction in symptoms and signs with treatment, and progression of disease after the age of 8 was rare. Conclusions: BKC in children can be defined as “a syndrome usually associated with anterior or posterior lid margin blepharitis, accompanied by episodes of conjunctivitis, and a keratopathy including punctate erosions, punctate keratitis, phlyctenules, marginal keratitis, and ulceration.” BKC is common in children in a tertiary referral corneal and external diseases clinic, with the more severe manifestations in the Asian and Middle Eastern populations. Therapy is effective and loss of sight can be prevented in most cases.

Topical Heparin in the Treatment of Ligneous Conjunctivitis

BACKGROUND Ligneous conjunctivitis is a rare acute or subacute membranous conjunctivitis of unknown etiology for which no generally accepted form of treatment is available. METHODS Between 1972 and 1993, 17 patients with ligneous conjunctivitis were treated with excision biopsy, meticulous hemostasis, and immediate, intensive topical treatment with heparin, steroids, and, in 12 patients, alpha-chymotrypsin until all signs of conjunctival inflammation had subsided. RESULTS On histologic examination, the lesions consisted of subepithelial deposits of fibrin in all patients. Eight patients had no recurrence (mean follow-up, 33.1 months) and in four patients the conjunctivitis was controlled after one repeat excision and topical treatment (mean follow-up, 40.3 months). One patient had three recurrences before responding to treatment (follow-up, 24 months). In four patients, treatment was unsuccessful, although lesion-free intervals were longer than usually seen in this condition (mean, 7.8 months). CONCLUSION These results suggest that intensive and early use of topical heparin may improve therapy results in ligneous conjunctivitis.

Legeais BioKpro III keratoprosthesis implantation: long term results in seven patients

Aims: The long term results of the Legeais BioKpro III keratoprosthesis are presented for seven patients with severe corneal scarring. Methods: The study took place at Moorfields Eye Hospital, London. Patients had either end stage ocular surface disease or corneal opacification after multiple failed graft surgery, with the potential for significant visual improvement. After insertion the device was covered with a conjunctival flap or buccal mucous membrane graft, which was later opened to expose the optic. The outcome measures were vision, complications, and retention of the device. Results: The BioKpro III was inserted into seven patients with severe corneal scarring: ocular cicatricial pemphigoid, measles keratitis, thermal injury, Stevens-Johnson syndrome, aniridia, chemical injury, and congenital rubella. The follow up was 18–48 months. The keratoprosthesis failed in six, because of extrusion occurring 2–28 months postoperatively. Retroprosthetic membranes occurred in three patients, and endophthalmitis in one. Vision improved from hand movements to 6/12 in the only patient who retained the KPro; however he was troubled by mucus accumulation on the optic. Conclusions: The one success has been in a patient with thermal burns. The remaining results have been poor, with the KPro extruding in six of the seven patients.

Clinical Study of Therapeutic Ocular Surface Medium for Persistent Epithelial Defect

Purpose: To investigate therapeutic ocular surface medium (TOSM), a potential physiological tear replacement therapy, for persistent epithelial defect (PED). Methods: 11 eyes of 10 patients with PED for ≥2 weeks without improvement despite conventional treatment were enrolled in a prospective pilot study of TOSM over 1 month. Results: Healing of the PED occurred in 3 out of the 11 eyes at 1, 2 and 4 weeks, respectively. At week 4, 2 eyes were almost healed (PED area ≤0.5 mm2). In 4 of the remaining 6 eyes, the PED area was reduced. Failure occurred in 1 case with end-stage ocular cicatricial pemphigoid and severe dry eye, and 1 patient withdrew due to a mild allergic reaction. There were no serious or irreversible side effects with TOSM. Conclusions: TOSM is a potential novel physiological therapy for PED that, unlike autologous serum, has the potential to be easily manufactured and widely available.

Toxicity of natural tear substitutes in a fully defined culture model of human corneal epithelial cells

PURPOSE Serum and saliva have recently been advocated as natural tear substitutes for intractable aqueous-deficient dry eyes, but the effects of these fluids on corneal epithelium have not been well characterized. A laboratory study was performed in a defined test model to compare the toxicity of natural and pharmaceutical tear substitutes and to identify potentially toxic factors in natural tear substitutes, such as amylase, hypotonicity, and variations in preparation. METHODS Primary human corneal epithelial cells were cultured with defined keratinocyte serum-free medium. The cells were incubated with hypromellose (hydroxypropylmethylcellulose 0.3%) with and without benzalkonium chloride 0.01%, saliva with differing osmolalities, 100% serum, and 50% serum (1:1 vol/vol with chloramphenicol 0.5%) for varying times and concentrations. Toxicity was examined in four ways. Microvillous density was assessed with scanning electron microscopy. Cell membrane permeability and intracellular esterase activity were analyzed after staining with fluorescent calcein-AM/ethidium homodimer and cellular adenosine triphosphate (ATP) was quantified using a luciferin-luciferase-based assay. RESULTS The toxicity ranking of the tear substitutes correlated in all assays. The ATP assay was the most sensitive, followed by ethidium cell permeability, and finally the esterase activity. Preserved hypromellose was more toxic than the unpreserved preparation. Among natural tear substitutes, natural saliva was most toxic. Isotonic saliva and 50% serum were of similar toxicity, and 100% serum was least toxic. Natural tear substitutes were-except for natural saliva-less toxic than unpreserved hypromellose. Hypotonicity, but not amylase, was the major toxic effect associated with saliva. The dilution of serum with chloramphenicol induced toxicity. CONCLUSIONS This is the first toxicity study using human primary corneal epithelial cells cultured under fully defined conditions as an in vitro model. Cellular ATP is a sensitive parameter for quantifying toxicity. Isotonic saliva and serum offer greater therapeutic potential for severely aqueous-deficient dry eyes than do pharmaceutical tear substitutes.

The management of severe sclerokeratitis following corneal transplantation surgery

There is a paucity of information in the scientific literature regarding post keratoplasty inflammation and the management of this rare but serious problem. Although corneal graft survival is known to be reduced when keratoplasty is undertaken in inflamed eyes,1 and published data are available for patients with known risk factors of atopy2 and acanthamoeba keratitis,3 little is known in this regard for grafted eyes in individuals without discernable risk factors who develop severe (non-rejection) inflammation following surgery. We describe a series of six disparate patients who developed severe scleral inflammation in the postoperative period and outline our management strategy in each case. Scleritis was diagnosed using the following criteria: severe diffuse scleral inflammation associated with pain and photosensitivity. All the cases manifested diffuse rather than nodular scleral involvement without involvement of the residual host cornea. The corneal grafts were secured using 10/0 nylon monofilament suture mounted on a 3/8 circle side-cutting stainless steel needle (Catalogue No 8065-208001 Alcon Laboratories, Hemel Hempstead, UK). Two cases are described in detail and a comparison in all the cases of the salient features is made in a summary table 1. View this table: Table 1  Summary of each patient and their clinical course (including ocular history) before and after developing postoperative scleral inflammation A 40 year old man presented with a left central corneal abscess. He had been treated for a presumed episode of herpetic epithelial keratitis and conjunctivitis several years before this but had had documented recurrent corneal erosion syndrome and blepharitis for the previous 2 years. On examination his left visual acuity was hand motions. He was found to have a central left corneal abscess 2.3 mm in width and 2.6 mm in height; this was covered by a mucous …