Ocular Fluorometry Research Articles

Optical sensors for clinical ocular fluorometry

Abstract The subject of Clinical Ocular Fluorometry is reviewed. The initial chapters deal with the basic principles of ocular flurometry and review the most recent efforts on harmonization and standardization of the various techniques available. The techniques and applications of ocular fluorometry using fluorescein as an exogenous tracer and the techniques and applications of ocular fluorometry looking at the natural fluorescence of ocular tissues are reviewed extensively, with special emphasis being given to their interpretation and present and potential clinical applications. Finally, new developments in optical sensor systems and future directions for clinical ocular fluorometry are analyzed. Recent developments in new optical sensors for fluorometry offer much promise. Topographic imaging vitreous fluorometry is expected to clarify the relationship between the alteration of the blood-retinal barrier and the development of retinal lesions. New sensor systems for noninvasive measurement of naturally occurring fluorophores in the cornea, lens and retina are expected to contribute to such clinically important areas as diabetic ocular complications, measurement of cataract formation and characterization of retinal degenerations. The transfer to routine clinical practice of ocular fluorometry, using fluorescein as the tracer, is considered to depend on simpler and easily available instrumentation together with the adoption of methodologies avoiding blood sampling and involving oral administration of fluorescine.

The improvement of solid state light sensors' performance using temperature control in ocular fluorometry applications

Ocular fluorometry is a non-invasive diagnostic technique that has been used widely in research to measure the amount of fluorescein leakage from the blood into the ocular tissues and fluids after intravenous injection. This information has been demonstrated to be valuable in a number of clinically relevant situations. This paper mainly deals with demonstrating how the use of modern sensors associated with effective temperature control can configure a low-cost solution to an ocular fluorometry instrument and still upgrade the performance previously obtained with bench-top units only. A new ocular fluorometer is briefly described and special attention is dedicated to the temperature cooling and control system that has been developed and to the quantification of its effects on the detector signal-to-noise ratio (SNR), lowest level of detection (LLOD) and error of measurement (EOM) within the context of ocular fluorometry requirements. Experimental evidence is given that shows not only the improvements in LLOD with moderate cooling (more then 35% for a decrease in temperature in the range), but also the attenuation of the EOM by temperature stabilization ( uncertainty in the range induces a EOM), the current LLOD being lower then , as we will see.

Lens autofluorescence is increased in newly diagnosed patients with NIDDM.

Lens and cornea autofluorescence has been shown to be increased in patients with insulin-dependent diabetes mellitus and to be positively correlated to glycaemic control and duration of diabetes. We have studied lens and cornea autofluorescence at the clinical onset of non-insulin-dependent diabetes mellitus (NIDDM), in comparison with age-matched subjects with normal glucose tolerance. Fourteen subjects with NIDDM diagnosed less than 6 months prior to the examination were characterised by ocular fluorometry, glycosylated hemoglobin A1c, plasma lipid status, arterial blood pressure, and an oral glucose tolerance test (OGTT). Eleven age- and gender-matched healthy subjects without a family history of diabetes and with a normal glucose tolerance underwent the same examinations. In 11 of the 14 diabetic patients lens autofluorescence was increased to levels higher than the age-related mean + 2SD of healthy subjects. For the entire study population, control and diabetic subjects, lens fluorescence was positively correlated with HbA1c (p < 0.0001, r = 0.73), fasting plasma glucose (p = 0.002, r = 0.60) and the plasma glucose level 2 h after an OGTT (p = 0.004, r = 0.55). Cornea autofluorescence was also significantly increased in the group of newly diagnosed NIDDM patients, but only 9 patients had values above the mean + 2SD of the healthy subjects. NIDDM could be detected by ocular fluorometry with a sensitivity of 79% and a specificity of 100%. We conclude that lens and cornea autofluorescence is abnormally increased in the majority of patients with newly diagnosed NIDDM. The sensitivity and specificity of the method indicate that lens fluorometry may potentially be useful for screening for undiagnosed NIDDM in the general population. Additionally, we propose that the method may be a clinically useful indicator of cumulative glycaemia and risk of development of secondary complications in patients with diabetes.

Changes of Corneal Redox State in Diabetic Animal Models

Metabolic and biochemical changes of the corneal epithelium and endothelium were studied in experimental diabetic animal models. Ocular redox fluorometry was used to noninvasively determine tissue reduction-oxidation (redox) changes in organ cultured rabbit corneas incubated in high glucose concentration media, alloxan-induced diabetic rabbits, and nonobese diabetic mice. The ratio of autofluorescence from reduced pyridine nucleotide to oxidized flavoproteins (PN/Fp) was used as the indicator of the redox state. Chemical assays for NADH and NAD+ were performed on in vitro materials. Analysis of corneal endothelial morphology using specular microscopy was performed to study possible correlations with metabolic changes. Both the PN/Fp and NADH/NAD+ ratios increased in the corneal endothelium under all experimental conditions. Changes in redox state were not observed in the corneal epithelium in any of the models. Morphologic analysis of the corneal endothelium revealed no significant changes. These results indicate that redox changes occur in the diabetic corneal endothelium, but not the corneal epithelium. Ocular redox fluorometry is capable of detecting changes in the corneal endothelial redox state noninvasively.

Spatial Coordinates in Ocular Fluorometry

Acta OphthalmologicaVolume 71, Issue S211 p. 17-21 Spatial Coordinates in Ocular Fluorometry First published: November 1993 https://doi.org/10.1111/j.1755-3768.1993.tb03111.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume71, IssueS211November 1993Pages 17-21 RelatedInformation

Introduction to Ocular Fluorometry

Introduction to Ocular Fluorometry

Future developments in ocular fluorophotometry instrumentation

The scope of ocular fluorometry is to monitor exogenous and endogenous fluorophores in ocular tissues, in relation with ophthalmic and systemic diseases using the unique optical prospectives of the eye. The elderly population and the incidence of blindness are increasing rapidly due to more cases of diabetes, glaucoma, cataract and age-related macular degeneration. Monitoring changes in specific fluorophores in the eye may help identify the high risk groups in these diseases. New developments in instrumentation include differential fluorometry and introduction of confocal optics. Differential fluorometry has already achieved significant progress for the study of the autofluorescence of the lens and cornea and measurements in the aqueous. Improved spatial resolution obtained with improved optics opens interesting possibilities like measurement of corneal endothelial permeability and retinal vascular permeability. The results already obtained will be presented with particular incidence on measurements of lens fluorescence (normals--336.2 +/- 56.3; diabetes--659.9 +/- 123.9; age group--40-50 y) and corneal endothelial permeability (normals--3.14 +/- 60.10(-1) cm-1).

Ocular fluorometry: principles, fluorophores, instrumentation, and clinical applications.

Ocular fluorometry is rapidly evolving as a versatile technique for research and diagnosis in ophthalmology. The main reasons for this increasing success are 1) the ideal characteristics of the eye as an optical device for excitation of tissue fluorescence and for the detection of the fluorescent emission; 2) the development of novel fluorometric techniques, including differential and time-resolved fluorescence spectroscopy; and 3) the increasing use of coupling geometries with high-resolution and high spatial selectivity. Both endogenous and exogenous fluorophores are of interest to ocular fluorometry. The most significant among endogenous fluorophores are the fluorescing pigments of the lens and of the retinal pigment epithelium (RPE). The nature, topography, and fluorescence properties of such pigments depend on age and pathology and on the level of light exposure. Exogenous fluorophores of interest are both intentionally induced and unintentionally accumulated drugs (some of which are phototoxic). Laser-based fluorometric techniques play a leading role in ocular fluorometry. The peculiar properties of the laser for the excitation of fluorescence make this source a favorite candidate for ocular fluorometry both in vitro and in vivo.