Biomedical subjects

M G Harris

Publications and source records attributed to M G Harris.

At least 73 records · Page 4Linked to original sources

PubMed1989

Microwave disinfection of soft contact lenses.

We evaluated the effectiveness and convenience of microwave irradiation as a method of disinfecting soft contact lenses. Soft contact lenses from each of the four Food and Drug Administration (FDA) categories were placed in sterile vials and immersed in 2 ml of saline which had been contaminated with one of three common species of bacteria. The contaminated lens vials were placed in a standard 600 W microwave oven and exposed to microwave irradiation times ranging from 30 to 180 s. Significant reductions in bacteria colony counts were found after 30 s of microwave irradiation. Few of the bacteria survived 60 s of microwave exposure and none survived 90 s. Our findings indicate that microwave disinfection can be an effective and rapid means of killing bacteria on soft lenses and in the storage solution. However, further studies are necessary to determine the minimum exposure time required, the effect of microwave disinfection on other microorganisms, and the effect of microwave irradiation on contact lens polymers and lens dimensions.

Bacterial Infections↗

PubMed1989

The pH of over-the-counter hydrogen peroxide in soft lens disinfection systems.

We evaluated the pH of six hydrogen peroxide (H2O2) soft lens disinfection systems which had over-the-counter (OTC) H2O2 substituted for the manufacturer's recommended H2O2. Substitution of four brands of OTC H2O2 into the five two-step disinfection systems resulted in a pH after neutralization which ranged from 6.70 to 7.55 pH units. There was a small but statistically significant difference in the pH after neutralization when OTC H2O2 was substituted for the manufacturer's recommended H2O2. There was a significantly lower pH after neutralization when the same brands of OTC H2O2 were substituted for the manufacturer's recommended H2O2 in a one-step H2O2 disinfection system. The pH after neutralization for the manufacturer's recommended H2O2 was 6.50 pH units. The pH after neutralization for the OTC H2O2 ranged from 3.35 to 4.77 pH units. This range is below the ocular comfort range of 6.6 to 7.8 pH units. These findings, along with other possible differences between OTC H2O2 and the manufacturer's recommended H2O2, indicate that OTC H2O2 should never be substituted for the manufacturer's recommended H2O2 in any H2O2 soft lens disinfection system.

Contact Lenses, Hydrophilic↗

PubMed1989

Computerized optometric records and the law.

Today, most computerized optometric records contain the financial and business data for a practice. As technology advances in both optometric instrumentation and computerization, data for the optometric examination is also becoming part of the computerized recordkeeping system. This paper discusses legal aspects of computerized optometric examination records with respect to content, patient confidentiality, authentication for litigation defense, and proper handling by staff.

Confidentiality↗

PubMed1988

Monovision contact lens wear and occupational task performance.

The effects of monovision (MV) contact lens wear on the performance of occupational-type nearpoint tasks was evaluated on 18 presbyopic subjects (ages 44 to 67 years) by comparing MV performance (MV condition) to that with distance contact lenses with reading glasses (BV condition). Each subject had correctable distance visual acuity of 6/6 (20/20) in each eye, at least 60 sec arc of near stereopsis, good ocular health, and no previous MV experience. Time performance and error performance for 3 nearpoint occupational tasks (pointers and straws, card filing, and letter editing) were measured with the MV correction and BV correction. Measurements were taken at dispensing and at 2 weeks and 8 weeks after dispensing. Subjects were instructed to wear the MV soft spherical contact lenses at least 8 h per day. We measured BV time performance to be better than MV time performance by 2.8 to 5.7% and also measured an increased number of errors with MV.

Aged↗

PubMed1988

pH and H2O2 concentration of hydrogen peroxide disinfection systems.

Hydrogen peroxide disinfection has caused discomfort for some soft contact lens wearers even though the solution was neutralized properly. The discomfort could be due to the endpoint pH of the system used or the residual H2O2 concentration. Using a digital pH meter and H2O2 concentration detection strips, we measured the pH and H2O2 concentration of seven different hydrogen peroxide disinfection systems over their recommended disinfection and neutralization cycles to determine their time courses and endpoint values. The final pH of the seven systems varied from 6.15 to 7.74 pH units. All systems resulted in residual H2O2 concentrations below threshold values. These findings indicated that the final pH may be the cause of patient discomfort after hydrogen peroxide disinfection and neutralization.

Contact Lenses, Hydrophilic↗

PubMed1988

Contact lens prescriptions: a clinicolegal view.

The release of contact lens prescriptions is regulated by a variety of laws, and optometrists need to be familiar with these requirements to determine when prescriptions must be provided to patients or third parties. We recommend that contact lens prescriptions include the refractive data, lens parameters, lens manufacturer, expiration date, number of permissible refills, the notation "for daily wear only" if the lenses are not intended for extended wear, and other appropriate information intended to ensure that the patient will obtain the lenses prescribed if the prescription is presented to a dispenser.

Contact Lenses↗

PubMed1988

A review of five recent cases of significance for optometrists.

The standard of care expected of optometrists continues to be defined by the courts. Misdiagnosis of ocular disease and liability for injuries caused by ophthalmic products remain the leading causes of litigation. Documentation of findings, warnings, and key management decisions is an essential aspect of clinical practice and must not be neglected by clinicians.

Accidents, Occupational↗

PubMed1988

Clinicolegal considerations of monovision.

Patients who wear monovision contact lenses must be carefully selected, properly fitted, and adequately informed of the risks of reduced visual acuity and stereopsis. A demonstration of the visual effects of monovision should be used to determine the adaptability of patients to this form of lens wear, and patients should be advised to undergo a gradual adaptation to their lenses. Negligence in the prescribing, fitting, follow-up of these patients can create liability for the contact lens practitioner. Patients must be warned of the risks of monovision lens wear, as required by the doctrine of informed consent, and these warnings should be documented, either by making entries in the patient's record or through the use of forms. Contact lens prescriptions should include all the information necessary to ensure that replacement lenses are the same parameters as those prescribed.

Contact Lenses↗

PubMed1987

Use of high resolution in vivo volume selected 1H-magnetic resonance spectroscopy to investigate leukemia in humans.

In vivo high resolution volume-selected 1H magnetic resonance spectroscopy of human tibia has been undertaken using spatial coordinates obtained from magnetic resonance images. Adult tibial marrow has a 1H spectrum rich in fatty acid resonances and is readily distinguished from the 1H spectra of surrounding leg muscle. In all four leukemic patients examined, infiltration of fat cells of tibial marrow by proliferating cells rich in mobile H2O protons was evident by magnetic resonance imaging. Selective examination of volumes of tibial marrow (1 cm3) by 1H magnetic resonance spectroscopy confirmed marked differences in the 1H spectra of marrow from these patients. Increases in the H2O peak of the 1H spectra were correlated with infiltration of blast cells and lack of control of the neoplastic disease. These studies are the first to report the use of volume selected magnetic resonance spectroscopy to selectively monitor leukemia in humans.

Adolescent↗

PubMed1987

Sweet's syndrome, acute leukemia, and t(3;5).

We report herein the case of a 36-year-old woman who was diagnosed as having Sweet's syndrome 13 months prior to developing acute myeloid leukemia (FAB type M2). Her bone marrow karyotype was 46,XX,t(3;5)(q21;q31). Translocation t(3;5) has been reported in seven other cases of acute nonlymphocytic leukemia. None of these cases have been associated with Sweet's syndrome.

Adult↗

PubMed1987

Heart rate reactions to standard laboratory challenges and a naturalistic stressor.

Extreme high and low heart rate reactors were selected on the basis of responses to two laboratory stressors; a video game, and mental arithmetic. The heart rates of the same subjects were then recorded during a public speaking competition. Heart rate reactions to this more naturalistic stressor were generally in line with the laboratory-based designations.

Adult↗

PubMed1987

Flexure and residual astigmatism with Paraperm O2 and Boston II lenses on toric corneas.

It has been shown previously that thin polymethyl methacrylate (PMMA), cellulose acetate butyrate (CAB), and Polycon I contact lenses flex on toric corneas. We investigated the flexure and induced residual astigmatism of two gas permeable contact lens materials, Paraperm O2 and Boston II, and compared the results with those of other materials. Six subjects (12 eyes) with corneal toricities ranging from 1.75 to 3.25 D wore five Paraperm O2 lenses and five Boston II lenses with center thicknesses ranging from 0.10 to 0.20 mm. Flexure and induced residual astigmatism were measured on all corneas wearing all lenses in a double-masked fashion. All lenses studied showed flexure and induced residual astigmatism, which increased as center thickness decreased. For both lens types, lenses thinner than 0.15 mm flexed significantly more than thicker lenses. This critical center thickness should be considered when fitting these lens types on toric corneas.

Adult↗

PubMed1987

Microbiological testing of the Blairex Water Purifier.

The Blairex Water Purifier (previously called The Blairex Deionizer) is a filtration unit designed to purify tap water for uses that require distilled or deionized water. The unit is intended to offer soft contact lens wearers a more convenient and safe method of obtaining distilled water when using salt tablets or enzymatic cleaning tablets. In this study, the safety of these units was analyzed from a microbiological point of view. The microbial starting state of 18 factory sealed Blairex Water Purifiers was evaluated by filtering sterile water through each unit and enumerating the organisms in the effluent. Then a known number of specific microorganisms was filtered through each unit. For the next 30 days, subsequent sterile distilled water filtrations were done each day. The effluent was collected with each filtration and enumerated for microorganisms. The results indicated that the majority of Blairex units tested were not sterile from the onset. Several Blairex units evaluated did support bacterial growth, as the bacteria that were passed through the unit on day 1 of the study were found in the effluent in increasing numbers with use. The clinical implications of our findings are discussed. Each time Blairex units were obtained for evaluation, the units appeared different in either filter attachments, plastic composition, or shape. The results varied according to which type of Blairex unit was tested.

Evaluation Studies as Topic↗

PubMed1987

Effect of refrigeration on microbial growth in the Blairex Water Purifier.

The Blairex Water Purifier is designed to make tap water into purified water that can be used to make saline solution for soft contact lens disinfection and rinsing. The micropore filters of eight Purifiers were perforated to allow a controlled contamination by either Pseudomonas aeruginosa or Serratia marcescens. The bacterial growth was evaluated in these altered Blairex Water Purifiers under refrigerated and unrefrigerated conditions. Those Purifiers that were refrigerated showed significantly less bacterial growth than those Purifiers that were kept at room temperature between samplings. Our findings imply that soft contact lens wearers may reduce the level of microbial growth in undamaged Purifiers by refrigerating the Purifiers between uses.

Contact Lenses, Hydrophilic↗

PubMed1987

Liability and extended wear contact lenses.

The fitting and dispensing of extended wear contact lenses places special clinical and legal demands upon optometrists. These patients must be monitored on a regular basis to minimize the risk of complications. To promote better understanding and compliance, the use of printed agreements is recommended. Failure to observe these factors--and to document patient care--may lead to professional liability claims based on allegations of negligence or product liability.

Contact Lenses, Extended-Wear↗

PubMed1987

Informed consent in contact lens practice.

The legal doctrine of informed consent mandates that the doctor provide sufficient information so a patient can refuse or consent to an optometric procedure in a knowledgeable, intelligent manner. Informed consent is especially important in contact lens practice. The informed consent procedures presented here are simple and straightforward. They should be a natural part of optometric practice, and will better educate patients who will less likely be displeased with the course of treatment because of unrealistic expectations.

Contact Lenses↗

PubMed1987

Oral idarubicin as single-agent treatment of acute nonlymphocytic leukemia in poor-risk patients.

Oral idarubicin was given as single-agent treatment of acute nonlymphocytic leukemia in 18 poor-risk patients. They comprised nine previously untreated elderly patients, age range 69-86, and nine relapsed pretreated patients, age range 41-76. Overall, two patients achieved complete remission (including one with preceding refractory anemia with excess of blasts) and seven achieved partial responses. Dose-limiting toxic effects were diarrhea and sepsis. In this limited study, oral idarubicin at a dose of 20-25 mg/m2/day X 3 was a well-tolerated drug with potent antileukemic effects. The oral formulation deserves more widespread evaluation.

Administration, Oral↗

PubMed1986

The perception of moving stimuli: a model of spatiotemporal coding in human vision.

An empirically plausible extension of the Marr and Ullman (1981) [Proc. R. Soc. Lond. B 211, 151-180 (1981)] model for coding movement direction uses the magnitude of spatial and temporal response derivatives to encode the speed as well as the direction of movement. The performance of the model is illustrated for drifting edges of different spatial scales and the properties of the components which separately compute the two derivatives are respectively compared to individual channels of the conventional pattern and flicker systems.

Flicker Fusion↗