Use of contact lenses in patients with filtering blebs

Purpose: The purpose of this study was to describe the outcome of patients with filtering blebs who were fit with contact lenses. Methods: We retrospectively studied patients with filtering blebs secondary to glaucoma or cataract surgery who were fit with contact lenses. Eight eyes from seven patients were identified. Results: Five patients (six eyes) were fit with gas permeable contact lenses and two patients (two eyes) were fit with soft contact lenses. Successful fits were achieved in all patients. No complications were observed after a mean follow-up of 64.6±28.5 months. Conclusions: No significant complications were recorded in our series of patients with filtering blebs who were fit with contact lenses. We think that when indications for fitting contact lenses are justified, patients with filtering blebs are acceptable candidates for contact lens use. However, adequate selection of cases, careful contact lens fitting, patient education, and close follow-up are necessary.

Evaluation of contamination of used disposable contact lenses by Acanthamoeba

Purpose: The purpose of this study was to evaluate the contamination of used disposable soft contact lenses with Acanthamoeba. Methods: We evaluated 51 consecutive disposable soft contact lens wearers in a prospective study. Before their check-up visits, patients were offered a free new contact lens in exchange for donating their old one. The used contact lenses (n=102) were then removed and placed in culture medium for Acanthamoeba. We subsequently investigated patterns of wear and hygiene habits. Results: The mean age of this population was 32.6±11.0 years. The average time of disposable soft contact lens wear was 13.7 hours per day. The contact lenses were disinfected daily with commercial solutions. Twenty-five (49.0%) subjects did not clean their lens cases properly. Acanthamoeba was not isolated from any of the 102 lenses. Conclusions: There were no cases of Acanthamoeba contamination in a small population of disposable soft contact lens wearers who regularly disinfected their lenses with standard commercially available contact lens solutions.

Non-Acanthamoeba amebic keratitis

Purpose. To describe the clinical presentation and outcome of two cases with presumed non-Acanthamoeba amebic keratitis. Methods. Case reports. Results. Both patients presented with typical symptoms and signs of Acanthamoeba keratitis. The patients' soft contact lenses, lens cases, open solutions, and conjunctival samples were cultured. Diagnosis of non- Acanthamoeba amebic keratitis was based on the presence of keratitis and amebic growth from patients' contact lenses of the affected eyes. Amebic culture from the contralateral contact lens was negative. Vahlkampfia cysts were identified in case 1, and Naegleria cysts in case 2. Topical treatment with polyhexamethylene biguanide and propamidine resolved the keratitis in case 1. Case 2 was lost to follow-up. Conclusion. Non-Acanthamoeba amebic keratitis was diagnosed in two patients based on the clinical presentation (resembling Acanthamoeba keratitis), culture of the contact lens, and response to antiamebic treatment (in one case). Keratitis associated with Naegleria contamination of contact lenses has not been previously reported.

Contact lens use after contact lens-associated infectious ulcers

Purpose: The purpose of this study was to evaluate the outcome of patients with healed moderate to severe contact lens-associated corneal infectious ulcers who were re-fit with contact lenses. Methods: We retrospectively studied patients who were fit with contact lenses on our service and who had had moderate to severe corneal infectious ulcers associated with previous contact lens use. Six patients were included in the study. Results: Gas permeable contact lenses were fit in five patients, and a soft contact lens was fit in one patient. Successful fit was achieved in all cases and visual acuities were equal to or better than 20/30 in all patients. No significant complications were observed after a mean follow-up of 23 months (range, 6-45 months). Conclusion: In this small series of patients with a history of moderate to severe contact-lens related infectious keratitis, no complications were observed after contact lenses were refit. Contact lens wear in patients with a history of infectious keratitis may be safe and useful in order to achieve visual rehabilitation.

Key biological issues in contact lens development

A contact lens is a medical device widely used as an alternative to spectacles in order to correct refractive vision problems. The evolution of polymeric biomaterials has heralded a continuous development in the materials used to produce contact lenses and maximize patient comfort and limit adverse events. Microbial keratitis (MK) is a relatively rare but potentially devastating condition associated with contact lens use, particularly with the extended wear of hydrogel lenses. It is the principal complication related to contact lens wear and the large population at risk make it a public health concern. Bacterial binding to the contact lens material is a precursor to the development of MK and is influenced by properties of the material and the bacteria. In order for bacteria to infiltrate the cornea there must be some degree of corneal damage, usually caused by trauma or hypoxia. The most recent materials available aim to allow the continuous wear of lenses while limiting corneal hypoxia, thus helping to prevent the development of MK. Limitations to the treatment of MK require that novel approaches may be necessary in order to limit bacterial adhesion to contact lens materials.

Successful medical treatment of Acanthamoeba keratitis

Purpose: To describe the outcome of a series of Acanthamoeba keratitis treated with a similar regimen. Methods: All cases diagnosed with Acanthamoeba keratitis in a referral centre from June 1994 through June 1997 were included. Diagnosis of Acanthamoeba keratitis was based in clinical presentation and laboratory results. Positive laboratory identification of Acanthamoeba from corneal scraping or contact lens was required, unless the patient had very characteristic symptoms (severe pain) and signs of the infection, including perineural infiltrates. Initial intensive treatment included topical polyhexamethylene biguanide (PHMB) 0.02%, propamidine isothionate 0.1% and broad-spectrum antibiotics. The treatment was gradually tapered. After documented response to anti-acanthamoeba therapy, topical steroids were introduced; they were discontinued before cessation of the antiAcanthamoeba regimen. Results: Six males and four females, with a mean age of 30.0 ± 7.4 years were included in this study. All cases weared contact lenses. On presentation all cases had severe pain, and epitheliopathy was associated with stromal infiltrate in most (seven of ten) cases. Four patients had anterior uveitis. Perineural infiltrates were present in three cases and ring infiltrate in one patient. Anti-amoebic treatment was started 12.7 ± 7.2 days after beginning of symptoms. The clinical response to therapy was very satisfactory in all patients. Within two to three weeks all patients had remarkable lessening of pain and photophobia, and improvement of clinical signs. At two to three months, visual acuity had improved in all patients. Two patients required penetrating keratoplasty for visual rehabilitation. Conclusion: The use of PHMB and propamidine cured all cases of Acanthamoeba keratitis. Cautious introduction of steroids was associated with expedited resolution of inflammation and provided symptomatic relief.

A laboratory based model study. Experimental observations of footings supported on soft clay reinforced with granular columns.

The inclusion of granular columns in soft clay deposits leads to improvements in bearing capacity and overall stiffness along with a reduction in consolidation settlement. Many laboratory investigations have focused on aspects of bearing capacity, but published data on settlement performance is limited. This paper reports on some interesting findings obtained from a laboratory model study in respect of these issues. In this investigation, 300 mm diameter by 400 mm long samples of soft kaolin clay were reinforced with single or multiple granular columns of various lengths using the displacement and replacement installation methods. The experimental findings revealed that, for the same area replacement ratio, limited settlement reduction was achieved for single long floating columns and end-bearing column groups. Marginal improvements in settlement performance were also achieved for columns installed by the displacement method. No settlement reduction was achieved for short single floating columns while short floating granular column groups produced increased settlements. These observations were verified using contact pressure measurements between the footing and column/surrounding clay.