The surface of the human eye is covered with a protective tear film that refreshes with each blink. Natural blinking occurs involuntarily, but one can also voluntarily blink or refrain from blinking. The maximum time one can refrain from blinking until the onset of discomfort is the maximum interblink period (MIBP). During the interblink period the tear film evaporates and thins from the ocular surface. Infrared thermography provides a non-invasive measure of the ocular surface temperature (OST). Due to evaporation, ocular surface cooling (OSC) generally occurs when the eyes are open and exposed to the environment. The purpose of our study was to investigate the effect of OSC rate on the MIBP, and to investigate the association of the MIBP with tear film characteristics in subjects who do and do not exhibit OSC. The MIBP was measured simultaneously with OST over time. Non-invasive tear breakup time, tear meniscus height, tear lipid layer thickness, and Schirmer I test strip wetted lengths were measured on a day prior to the thermography visit. Subjects were divided into cooling and non-cooling groups based on OSC rate, and demographic and tear film characteristics were tested for inter-group differences. A faster OSC rate was associated with an exponentially shorter duration of the MIBP overall and within the cooling group alone. Faster non-invasive tear breakup time was significantly associated with a shorter MIBP in both groups. These results suggest that tear film evaporation initiates a pathway that results in the onset of ocular discomfort and the stimulus to blinking. The presence of a subset of subjects with no or minimal OSC who nevertheless have a short MIBP indicates that evaporative cooling is not the only mechanism responsible for the onset of ocular discomfort.
The surface of the human eye is covered with a protective tear film that refreshes with each blink. Natural blinking occurs involuntarily, but one can also voluntarily blink or refrain from blinking. The maximum time one can refrain from blinking until the onset of discomfort is the maximum inter-blink period (MIBP). In between blinks the tear film thins and evaporates from the ocular surface. Tear film evaporation can be measured with various instruments. Infrared thermography provides a non-invasive measure of the ocular surface temperature (OST). Due to evaporation, ocular surface cooling (OSC) generally occurs when the eyes are open and exposed to the environment. The purpose of our study was to investigate the effect of OSC on the MIBP, and to investigate the association of the MIBP with tear film characteristics in subjects who do and do not exhibit OSC. The MIBP was measured simultaneously with OST over time. Non-invasive tear breakup time, tear meniscus height, tear lipid layer thickness, and Schirmer I test strip wetted lengths were measured on a day prior to the thermography visit. Subjects were divided into cooling and non-cooling groups based on OSC rate, and demographic and tear film characteristics were tested for inter-group differences. A faster rate of OSC was associated with an exponentially shorter duration of the MIBP overall and within the cooling group alone. Faster non-invasive tear breakup time was significantly associated with a shorter MIBP in both groups. These results suggest that tear film evaporation initiates a pathway that results in the onset of ocular discomfort and the stimulus to blinking. The presence of a subset of subjects with no or minimal OSC who nevertheless have a short MIBP indicates that evaporative cooling is not the only mechanism responsible for the onset of ocular discomfort.
Background It is not uncommon for patients to have a labeled allergy to antibiotics without thorough investigation of their adverse reactions. The adverse reactions described by some patients are not immune-mediated and these patients are incorrectly labeled as having an antibiotic allergy. As clinical testing for antibiotic allergy is expensive and time intensive, recent initiatives have successfully used patient interviewing to differentiate non-immune mediated reactions from true antibiotic allergies. We investigated the prevalence of patients with non-immune mediated reactions to antibiotics among patients with documented antibiotic allergy by using a standardized questionnaire in the outpatient setting. Methods Patients with a documented antibiotic allergy were identified and recruited from 2 clinics located in the greater Chicagoland area. Subjects completed one standardized questionnaire regarding each of their previous adverse reaction to antibiotics. We then evaluated the questionnaire responses to extricate the non-immune-mediated adverse reactions. The full symptom classification can be found in Table 1 and Table 2. Results 98 patients were recruited with a total of 159 antibiotic questionnaires completed. At the patient level, 18 individuals had no immune-mediated reactions despite antibiotic allergy labels: 18.37% (95% CI: 10.7%, 26.3%). At the antibiotic level, 35 labels had corresponding clinical histories that were likely non-immune mediated: 22.0% (95% CI: 14.7%, 29.4%). Macrolides (8/11, 72.7%), nitrofurantoin (1/2, 50%), and amoxicillin/clavulanate (2/8, 25%) were the antibiotics with the highest percentage of corresponding clinical histories that were likely non-immune mediated (Figure 1). Penicillin was the most prevalently listed antibiotic allergy (43/159, 27.0%), followed by sulfonamides (25/159, 15.7%) and fluoroquinolones (21/159, 13.2%). Conclusion This study demonstrated the feasibility of using a standardized questionnaire to discern true antibiotic allergies from non-immune mediated adverse reactions. The improved accuracy of documented allergies allows for better optimization of antibiotic prescribing. Disclosures All Authors: No reported disclosures.
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