The CLAO journal : official publication of the Contact Lens Association of Ophthalmologists, Inc最新文献

Purpose: Many in vitro alternatives to eye irritation testing are not mechanism-specific and do not employ ocular cell lines. We have developed an effective and reliable test battery that reveals toxicity mechanisms of contact lens solutions on cell metabolism and proliferation.

Methods: Cytotoxicity endpoints were quantified using bovine corneal epithelial cultures in 96-well microplates. A kenacid blue assay provided information on total cell protein, while lactate production and alamarBlue assays served as indicators of aerobic/anaerobic metabolism and redox state of cells grown in serum-free Dulbecco's modified Eagle's/Ham's F12 medium (DMEM/F12). Concentrations (% v/v) causing 10-90% inhibition of the control assay responses were used for correlations with in vivo data.

Results: Cytotoxicities of contact lens solutions correlated better with irritant symptoms than with corneal staining, and were ranked as follows: Lens Plus << Opti-Free < or = ContaClair < or = ReNu. Lens Plus was not toxic to cell glycolysis, respiration, and proliferation for up to 20% v/v. However, the multi-purpose solutions inhibited these endpoints in a concentration-dependent manner. Opti-Free and ReNu, containing Dymed and Polyquad (ammonium surfactants), showed non-specific cell inhibition. The lactate production assay had a flatter log concentration-response curve than the other two assays.

Conclusions: The proposed biochemically-based test battery using the target corneal epithelium has the potential to be a simple and effective method for screening and defining toxicity profiles of contact lens care solutions. The model can be applicable to small- or large-scale testing programs and research and development of new ocular products.

Purpose: To reshape or flatten the corneas of post-radial keratotomy (RK) patients with residual myopia to improve uncorrected vision.

Methods: Twenty-one eyes (12 patients) with undercorrected RK results were fit with the Lexington RK splint, a multicurve plateau concept RGP contact lens.

Results: After wearing the lens an average of 6.1 months, undercorrected visual acuity improved an average 3.4 lines; change in spherical equivalent averaged 0.77 D; and flat K change averaged 0.75 D. Seventeen of 21 eyes (81%) demonstrated improved uncorrected vision. Nine eyes (43%) subsequently had a decrease in vision after discontinuing lens wear. Patients fit within 7 months of their last RK procedure were more likely to achieve optimal results. Sixty-two percent of this group did not require glasses or contact lenses (range: 4 to 21 months).

Conclusions: A well-designed and fit plateau RGP contact lens can manipulate the healing post-RK cornea.

Purpose: The purpose of this study was to determine the changes in bacterial adhesion resulting from air-drying soft contact lenses.

Methods: An in vitro study was conducted on four sets of identical, unworn etafilcon A soft contact lenses, air-dried for varying periods of time. These lenses were placed in a bacterial suspension, rinsed, ground, and plated in order to determine bacterial adhesion.

Results: The increased bacterial adhesion to these high water content, ionic lenses was statistically significant following five minutes of drying. Reversal of the effect was noted after rehydration.

Conclusions: Soft contact lens drying results in increased bacterial adhesion.

Purpose: We report a case of Alcaligenes xylosoxidans keratitis following penetrating keratoplasty in a rigid gas permeable (RGP) lens wearer.

Methods: A 61 year old RGP lens wearer with a history of nonresponsive keratitis of the right eye which involved the graft margin was referred to us for treatment. Corneal cultures revealed growth of a gram-negative rod on the fifth day and the organism was subsequently identified as Alcaligenes xylosoxidans, which was resistant to most antibiotics and sensitive only to Bactrim, Timentin, and imipenem.

Results: Clinical improvement was observed within 24 hours after treatment with the use of topical i.v. Bactrim and topical i.v. Timentin 2% alternating every 30 minutes. Complete resolution of the infection with mild scarring was observed 6 weeks after treatment.

Conclusions: Alcaligenes xylosoxidans is a potential cause of bacterial keratitis which should be considered in cases of nonresponsive gram-negative keratitis. The addition of topical Bactrim or Timentin may need to be considered in such cases.

Purpose: Overall, contact lenses provide a safe and effective modality for vision correction. However, problems do occasionally arise. Up to 80% of contact lens complications can be traced to poor patient compliance with recommended lens care guidelines. We conducted a survey to evaluate the level of patient compliance in specific areas of lens care and maintenance and to assess patient knowledge of basic contact lens information.

Methods: Patients were asked to complete an anonymous 15 question survey that focused on lens care--specifically the use of contact lens cleaners, methods of disinfection, enzyme treatments, use of rewetting drops, and the frequency of follow-up exams. In addition, the survey included six true/false questions relating to contact lens care and safety.

Results: There were a total of 103 participants in the study. Approximately 24% of patients stated they never cleaned their lenses prior to disinfection, and 5% used saline solutions as their primary mode of disinfection. A sizable portion of those surveyed (43% of soft lens wearers and 71% of rigid gas permeable lens wearers) either never used enzyme cleaners or used them less than once a month. Seventy percent of patients either never used rewetting drops or used them less than once a day. Twenty-nine percent of patients consulted their eye care professionals every 2 years and 6% less often than every two years. Six questions assessed patient knowledge of contact lens care safety. Of a possible six out of six correct answers, the mean number of correct responses was 3.74.

Conclusions: A sizable proportion of contact lens wearers do not adequately adhere to recommended contact lens care, and many have an inadequate understanding of contact lens care guidelines. Therefore, it is important that practitioners place more emphasis on patient education at the time of initial contact lens fitting and reinforce such instruction during follow-up visits.

Purpose: The purpose of this study was to determine the clinical utility of computerized corneal topography (CCT) in the fitting of rigid gas permeable (RGP) contact lenses.

Methods: In this prospective study, we compared the clinically determined parameters to those obtained by CCT in 50 consecutive patients who underwent RGP lens fitting. The TMS-1 program was used for CCT, and we fit patients with Boston RGP contact lenses (type II, or Equalens). The final decision on the RGP lenses dispensed relied upon the clinical evaluation (slit lamp examination, fluorescein pattern, lens centration, and visual acuity).

Results: The base curve of RGP lenses proposed by CCT was similar to that selected clinically (mean: 7.74 mm versus 7.81 mm). However, the mean diameter of the CCT proposed lenses was smaller than that selected clinically (9.31 mm versus 9.6 mm, P < 0.01). Divergence was more pronounced in keratoconus.

Conclusions: CCT is an important tool in RGP contact lens fitting. Clinical evaluation remains mandatory in determining the appropriate RGP lens.

Purpose: To determine oxygen tension (PO2) on rabbit corneas beneath rigid gas permeable (RGP), hydrogel, and silicone elastomer lenses under open- and closed-eye conditions and to demonstrate the relationship between PO2 and overnight corneal swelling response in the rabbit model.

Methods: An improved PO2 monitoring system (PO-2080) with a platinum-micro-wire-electrode was used to measure PO2. An ultrasonic pachymeter (DGH-2000) was used to measure corneal thickness after overnight wear.

Results: The relationship between PO2 and oxygen transmissibility (Dk/ L) of the contact lens was linear for Dk/L between 0 and 70 x 10(-9) (cm/ sec)(mLO2/mL x mmHg). For Dk/L greater than 70 x 10(-9), PO2 gradually reached a plateau at 120 mmHg for open-eye conditions and 20 mmHg for closed-eye conditions. PO2 was inversely related to the overnight corneal swelling, ranging from 5.1% swelling at PO2 113.5/17.5 mmHg (open/closed-eye) for a hyper Dk/L lens (125 x 10(-9)) to 15.1% swelling at PO2 10.4/5.1 mmHg for a low Dk/L lens (11.5 x 10(-9)).

Conclusions: Polarographic determination of PO2 provides reliable information about the amount of oxygen available to the cornea under a lens for both open-eye and closed-eye conditions. The data demonstrate that it is not possible to achieve normal oxygen levels with contact lens wear, even when hyper Dk/L lenses are worn.