ABSTRACT
Many parameters affect tear film thickness and fluorescent intensity distributions over time; exact values or ranges for some are not well known. We conduct parameter estimation by fitting to fluorescent intensity data recorded from normal subjects' tear films. The fitting is done with thin film fluid dynamics models that are nonlinear partial differential equation models for the thickness, osmolarity and fluorescein concentration of the tear film for circular (spot) or linear (streak) tear film breakup. The corresponding fluorescent intensity is computed from the tear film thickness and fluorescein concentration. The least squares error between computed and experimental fluorescent intensity determines the parameters. The results vary across subjects and trials. The optimal values for variables that cannot be measured in vivo within tear film breakup often fall within accepted experimental ranges for related tear film dynamics; however, some instances suggest that a wider range of parameter values may be acceptable.
Subject(s)
Models, Biological , Tears/physiology , Computational Biology , Computer Simulation , Dry Eye Syndromes/diagnostic imaging , Dry Eye Syndromes/physiopathology , Fluorescein , Fluorescent Dyes , Fluorophotometry/methods , Fluorophotometry/statistics & numerical data , Humans , Hydrodynamics , Least-Squares Analysis , Mathematical Concepts , Nonlinear Dynamics , Osmolar Concentration , Tears/chemistry , Tears/diagnostic imagingABSTRACT
Ocular burns are ophthalmological emergencies, owing to their potentially serious visual complications. Prompt recognition, irrigation and comprehensive examination including fluorescein staining is recommended to optimise outcomes. Burns standards recommend ophthalmological services be available in a 'timely' manner. This paper is a retrospective review of facial burn admissions between November 2017 and November 2018 at the Queen Elizabeth Hospital Birmingham (QEHB), a regional burns centre in the United Kingdom. This study aims to assess referral rates to ophthalmology, timeliness of review and the proportion of patients reviewed within a 24h window. From the data available we also aim to determine the frequency of fluorescein examination. Of 88 patients admitted with facial burns, data was available for 80 patients. The majority (n=77, 87.6%) suffered thermal burns. Twenty-two (27.5%) patients were referred to ophthalmology, and 18 (22.5%) had a documented review. Mean time from admission to review was 45.0h, with 10 (52.6%) patients being seen within 24h. Of 80 patients, 50 (62.5%) patients had no documented fluorescein examination. Further prospective studies are necessary to inform clinical guidelines and optimise management of facial burns.
Subject(s)
Burns/therapy , Eye Burns/diagnosis , Eye Burns/therapy , Facial Injuries/therapy , Fluorophotometry/statistics & numerical data , Practice Patterns, Physicians'/statistics & numerical data , Referral and Consultation/statistics & numerical data , Burn Units , Disease Management , Humans , Ophthalmology , Time Factors , Trauma Severity Indices , United KingdomABSTRACT
PURPOSE: To explore the relationships among length of contact lens (CL) wear, degree of corneal staining and severity of dryness symptoms, and to determine whether these relationships differ between Asians and non-Asians. METHODS: Adapted soft CL wearers (n=395; 180 Asian, 215 non-Asian) were required to discontinue CL wear for at least 24h and report to the University of California, Berkeley Clinical Research Center (UCB-CRC). Fluorescein corneal staining was graded according to Brien Holden Vision Institute scales. Length of CL wear was reported by subjects and subjective dryness ratings were collected using the UCB-CRC Dry Eye Flow Chart (DEFC). RESULTS: More Asian CL wearers exhibited corneal staining compared to non-Asians, and Asian CL wearers had a higher mean grade of corneal staining (p<0.001), as well as a higher mean DEFC classification (p<0.001). The difference between Asians and non-Asians in grades of corneal staining extent and depth were significant (p<0.001). Among non-Asian CL wearers, dryness symptoms decreased with more years of CL wear and increased in the presence of corneal staining, which was not the case for Asian CL wearers. CONCLUSIONS: Asian soft CL wearers reported more severe dryness symptoms and demonstrated more severe corneal staining overall compared to non-Asians. Among non-Asians, dryness symptoms were less severe on average with increased years of CL wear and more severe in the presence of corneal staining. Dryness severity does not appear to be related to years of CL wear or corneal staining among Asians.
Subject(s)
Asian/statistics & numerical data , Contact Lenses/statistics & numerical data , Cornea/pathology , Dry Eye Syndromes/diagnosis , Dry Eye Syndromes/ethnology , Fluorophotometry/statistics & numerical data , Adolescent , Adult , California/epidemiology , Causality , Female , Humans , Male , Prevalence , Reproducibility of Results , Risk Factors , Sensitivity and Specificity , Staining and Labeling , Young AdultABSTRACT
Video images of the cornea in photorefraction keratectomy (PFK) are analyzed by computer-aided microdensitometric analysis of televideo images of the eye. Optic density of various layers of the cornea and fluorescein penetration through the cornea were assessed in patients with myopia (235 eyes) and hypermetropia (65 eyes) before the after PFK. PFK was carried out by Nidek excimer laser (Japan). Analysis was carried out with consideration for the degree of emmetropia and patients' ages. Corneal transparency and index of fluorescein penetration through the cornea correlated with patient's age and emmetropia. Computer-aided microdensitometric analysis of televideo images of the eye earlier detects changes in the cornea than routine methods. The authors discuss the probability of assessing corneal transparency for selection of patients for PFK.