Slit-lamp Fluorophotometer Research Articles

EXPERIENCES WITH FLUOROPHOTOMETRY

Fluorophotometry using the Metricon Model 120 slit-lamp fluorophotometer showed, at an anterior focus, two peaks which corresponded to the cornea and ciliary region--the latter predominantly due to the ciliary body but contributed to by the lens--and following this, at a posterior focus, a mid-vitreous minimum and a chorioretinal peak. Tracings made both before and after fluorescein injection were similar but the levels were higher post-injection, with increasing age and with non-pigmented irides. The change in fluorescein distribution with time after injection is described. Abnormally high fluorescein levels were found in the normal fellow eye in retinal vein occlusion, in diabetes, in senile macular degeneration with neovascular membrane, in active central serious retinopathy and in acute optic neuritis. It is of use in the differentiation of primary choroidal melanoma from naevus and metastases. There was no correlation between isolated measurements of the haemoglobin A1C level and leakage; plasma and ultrafiltrate fluorescein levels in diabetics did not differ from normal.

Effect of Beta-Blocker Eyedrops on Corneal Epithelial Barrier Function

To investigate the long-term effect of a topically applied β-blocker on human corneal epithelium, the corneal epithelial barrier function and the superficial cell area of the corneal epithelium were evaluated. Seventeen normal healthy volunteers (without medication), 7 cataract patients (treated with pyrenoxine eyedrops) and 7 glaucoma or ocular hypertension patients (treated with 0.5% timolol maleate) were assigned to this study. The eyedrops had been used on a daily basis for at least 3 months. In the evaluation of corneal epithelial barrier function, fluorescein uptake was measured using a slitlamp fluorophotometer after application of 3 μl of 0.5% fluorescein for 10 min. In the evaluation of the superficial cell area, the central corneal epithelium was measured by tandem scanning confocal microscopy (TSCM). The healthy control and timolol groups were compared. Corneal fluorescein uptake in the healthy control, pyrenoxine and timolol groups was 20.3 ± 3.2, 21.5 ± 4.0 and 76.2 ± 30.0 ng/ml (mean ± standard error), respectively. There was a significantly higher fluorescein uptake in the timolol group compared to the pyrenoxine group (p = 0.0088) and the healthy control group (p = 0.0055). TSCM showed no significant difference in the superficial cell areas of the corneal epithelium between the healthy control and timolol groups. β-Blocker eyedrops decreased the corneal epithelial barrier function. Their application was not accompanied by any biomicroscopic change in the superficial cell area.

Fluorophotometric Assessment of Rabbit Corneal Epithelial Barrier Function After Rigid Contact Lens Wear

The effect of overnight wear of graded rigid gas-permeable (RGP) contact lenses on the rabbit corneal epithelial barrier function was assessed by fluorophotometry. RGP lenses with optimal fitting were worn by rabbits for 24 h. The values of oxygen transmissibility (Dk/L) of lenses used were 0, 10, 27, 43, 84, and 109 x 10(-9) (cm/s)(ml O2/ml mm Hg); lens thickness (0.15 mm) and diameter (14.0 mm) were standardized. Corneal epithelial barrier function was measured by a slit-lamp fluorophotometer. Corneal surface lesions by fluorescein staining were observed by a slit-lamp biomicroscope with the aid of fluorescein filter paper and were scored. Corneal epithelial structure was observed by scanning electron microscopy (SEM). After 24-h wear of RGP lenses, fluorescein uptake by the cornea increased, and this increase depended on the Dk/L value of lenses worn; mean +/- standard error, 1,601+/-454 (Dk/L 0), 347+/-226 (Dk/L 10), 144+/-42 (Dk/L 27), 100+/-25 (Dk/L 43), 56+/-18 (Dk/L 84), 51+/-15 (Dk/L 109), and 49+/-4 ng/ml (control). There was a significant correlation between the fluorophotometric value and the biomicroscopic scores of corneal lesions. SEM showed progressive desquamation of epithelial superficial and wing cells for lower-value Dk/L lens groups. This study demonstrated for the first time that overnight wear of Dk/L 84 and 109 lenses does not alter the barrier function of the rabbit corneal epithelium. In contrast, wear of a PMMA lens greatly alters the corneal epithelial barrier function. It is suggested that RGP lenses with a Dk/L >80 can provide safe overnight wear, based on the epithelial barrier function.

A Technique to Visualize Corneal Incision and Lamellar Dissection Depth During Surgery

To describe a surgical technique to visualize the depth of corneal incisions and lamellar stromal dissections during surgery. In porcine cadaver eyes, the aqueous was exchanged by air. Thus an air-to-endothelium interface (i.e., a useful optical surface) was created at the posterior corneal surface. The air-to-endothelium interface was used as a reference plane to visualize the corneal thickness and the relative depth of corneal incisions and dissections. Freehand peripheral corneal incisions, tangential keratotomy incisions, and lamellar stromal dissections were made at an intended corneal depth of 60, 80, and 99%. Light microscopy was used to measure the relative depth of the incisions and dissections. Achieved depth for peripheral corneal incisions averaged 65.2+/-5.3%, 78.8+/-5.1%, and 93.4+/-6.0%, respectively (p<0.05); and for tangential keratotomy incisions, 68.2+/-7.3%, 83.2+/-4.4%, and 95.8+/-3.6%, respectively (p<0.05). Achieved depth for lamellar stromal dissections averaged 58.3+/-9.4%, 81.1+/-3.4%, and 94.4+/-1.5%, respectively (p<0.05). Microperforations occurred with three incisions made at 99% intended depth. During surgery, the depth of incisions and lamellar dissections relative to the corneal thickness can be visualized by filling the anterior chamber with air (i.e., by creating an optical interface at the posterior corneal surface).

Impairment of ocular surface epithelium barrier function in patients with atopic dermatitis

AIMSTo assess the integrity of the ocular surface epithelium in patients with atopic dermatitis from the viewpoint of its barrier function.METHODS49 patients with atopic dermatitis with blepharoconjunctivitis (ABC group), 27...

Effects of aldose reductase inhibitor CT-112 on the corneal epithelial barrier of galactose-fed rats

PURPOSE. To investigate whether the barrier function of the corneal epithelium is disrupted in galactosemic rats, and to assess the effects of the aldose reductase inhibitor CT-112, in the form of eyedrops, on the corneal epithelial barrier in galactosemic rats. METHODS. Forty rats were divided into 3 groups based on their diet: a control group, a galactose group and a CT-112 treated galactose group (CT-112 group). After 3 weeks, 31 rats from the 3 groups were subjected to fluorophotometry, in which fluorescein (F) was instilled into one eye and carboxyfluorescein (CF) was instilled into the other eye in a random fashion. The F and CF uptakes were then measured at the central cornea by a slit-lamp fluorophotometer. Three rats from each group were exposed to a horseradish peroxidase (HRP) solution for one hour, and the HRP-reactive substances within the corneal epithelium were also examined via electron microscopy. RESULTS. There was significantly higher F uptake in the galactose group than in the control (p = 0.003) and CT-112 groups (p = 0.028). There were no significant differences in CF uptake between the 3 groups. Histologically, HRP-reactive substances were found in much greater quantities within the superficial corneal cells of the galactose group than in the control or CT-112 groups. CONCLUSIONS. These results suggest that cell membrane disruption, as detected by F uptake and HRP penetration, was found in the superficial corneal cells of galactose-fed rats, and that intercellular junction integrity can be assayed by CF uptake and histological evaluation. Moreover, CT-112 eyedrops were effective in improving the corneal epithelial barrier dysfunction of galactose-fed rats.

Effects of hypoxia and hypercapnia on contact lens-induced corneal acidosis.

It has been assumed that contact lens wear (CLW) may induce stromal acidosis, which is a result of corneal hypoxia and the accumulation of CO2 (hypercapnia) at the tear-lens interface. However, it has not been directly shown whether hypoxia and hypercapnia are the only causes of CL-Induced corneal acidification. In this study, we provide preliminary data about the relative contributions of hypercapnia and hypoxia to CL-induced stromal acidification by monitoring pH while the cornea was exposed to a hyperbaric oxygen atmosphere. This paradigm minimized if not eliminated the pH effects of lens-induced hypoxia on all but one subject without altering the pH effect of hypercapnia. Seven subjects were fitted with hydrogel lenses; 5 with low O2 transmissibility (Dk/LO2 = 14.0 x 10(-9) (cm/s) (ml O2/[ml x mm Hg)]), and 2 with medium O2 transmissibility (Dk/LO2 = 17.2 x 10(-9) (cm/s) (ml O2/[ml x mm Hg])) lenses. After lens insertion, modified goggles were fitted to control the corneal environment by exposing 1 eye to 20%O2 and 80%N2 (air), and the contralateral eye to 80%O2 and 20%N2 (hyperbaric O2). Corneal thickness (CT) was measured before CL insertion and over 120 min of wear. We assumed that corneal hypoxia was present if CT increased during the test period. Stromal pH was measured using a slitlamp fluorophotometer before lens insertion and at 20-min intervals for a total of 80 min. After 80 min of wearing the low Dk/L lens under hyperbaric exposure, 4 of 5 subjects showed reduced pH (mean delta pH = 0.23 +/- 0.05) and no increase in CT, suggesting that only hypercapnia was contributing to acidosis. For the same lens, but with exposure to air, 4 of 5 subjects showed a larger drop in pH (mean delta pH = 0.62 +/- 0.48) compared to hyperbaric exposure and an increase in CT, indicating that both hypoxia and hypercapnia reduced pH. Subjects wearing the medium Dk/L lens showed a small but equal drop in pH under both air and hyperbaric conditions without changes in CT, suggesting that only hypercapnia was contributing to acidosis. These preliminary results suggest that both mechanisms contribute to the pH shift accompanying CLW and that the contribution of hypercapnia is approximately 30%. Finally, the effects of hypercapnia and hypoxia are dependent on individual metabolic requirements and the transmissibility of the lens to O2 and CO2.

Clinical Evaluation of Corneal Epithelial Barrier Function with the Slit-Lamp Fluorophotometer

We designed a simple and quantitative method for the clinical evaluation of corneal epithelial barrier function using a slit-lamp fluorophotometer and applied it to healthy volunteers and dry-eye patients. The fluorophotometric method used was as follows: Three microliter of 0.5% fluorescein solution was applied to the cornea in the untouched fashion. Ten minutes after instillation, the ocular surface was washed. Twenty minutes afterward, corneal fluorescence intensity was measured and converted into fluorescein concentration. Corneal condition was classified into four grades: no superficial punctate keratopathy (SPK) anywhere on the cornea (grade 0); no SPK at the central cornea (grade 1), mild SPK at the central cornea (grade 2), and severe SPK at the central cornea (grade 3). In the volunteers, corneal condition was classified as grade 0 and fluorescein uptake (ng/ml) was 22.4 +/- 16.9 (mean +/- SD, n = 86). In dry eye, fluorescein uptakes showed significant increase in accordance with SPK severity: grade 1: 96.4 +/- 51.2 (n = 13); grade 2: 318.6 +/- 146.0 (n = 11); and grade 3: 1479.1 +/- 671.9 (n = 10) (each p < 0.0005). This simple method with the slit-lamp fluorophotometer can be used for the clinical grading of SPK in dry eye or other ocular surface diseases.

INTEGRITY OF THE BLOOD-OCULAR BARRIER AFTER INTRAVITREAL GAS INJECTION

The authors studied the effect of various intravitreal gases on the integrity of the blood-ocular barrier using a fluorophotometric technique. The gas (0.3 ml) was injected into the vitreous cavity of a pigment rabbit after paracentesis. Air and two long-acting gases, sulfur hexafluoride and perfluoropropane, were studied. The eyes that received only paracentesis served as controls. Fluorescein concentrations in the anterior chamber were determined by slit-lamp fluorophotometer 30 minutes following intravenous fluorescein administration. Fluorophotometry was repeated on days 1, 3, 7, and 14 after the gas injections. The eyes that received sulfur hexafluoride and perfluoropropane showed increased aqueous fluorescein concentrations in comparison with the control eyes and the air-injected eyes, although conventional slit-lamp biomicroscopic examination detected no anterior chamber inflammatory signs in these eyes. The aqueous fluorescein leakage decreased to the normal level after the intravitreal gas bubble was absorbed. These results suggest that intravitreal gas bubbles induce subclinical breakdown of the blood-aqueous barrier, which becomes re-established soon after the gas is absorbed.

Influence of the Viscosity and the Surface Tension of Ophthalmic Vehicles on the Retention of a Tracer in the Precorneal Area of Human Eyes

AbstractThe influence of the viscosity and the surface active characteristics of dextran and polyvinylalcohol (PVA) solutions on the retention of fluorescein in the precorneal area of human eyes is investigated. A non-invasive method using a slit lamp fluorophotometer is employed. The tear elimination coefficient and the AUC value of the recorded fluorescence decay curve are calculated.The addition of dextran and polyvinylalcohol (PVA) to an iso-osmotic buffer solution retards the precorneal loss of fluorescein. The instillation of a 4.2% PVA solution, however, causes discomfort, inducing in some cases rapid blinking and elimination of the tracer.

The Influence of the Dropsize on the Elimination of an Ophthalmic Solution from the Precorneal Area of Human Eyes

In order to study the influence of the dropsize on the ocular contact time and on the drainage of a fluorescent tracer a non-invasive method, using a slit lamp fluorophotometer is employed. Quantitative measurements of the fluorescence decay in the tear film, after instillation of an iso-osmotic tracer solution ranging in volume from 20 to 1 μl, are performed.In most cases an initial fast decay is followed by a slower elimination after a few minutes. The initial phase of the decay profile obeyes fairly well first order kinetics and the tear elimination coefficient is calculated. Important intra and inter subject variations are noted.In contrast to results obtained with rabbits no linear relationship between dropsize and tear elimination coefficient is observed. The elimination coefficient is insensitive to the dropsize over the range of 1 to 10 μl and sometimes to 20 μl.In general a dropsize smaller than 20 μl should be preferred to improve the therapeutic effect of ophthalmic drugs.

Photometric oculometry: a slit-lamp technique for determination of intraocular distances.

The optics of slit-lamp fluorophotometry were analyzed. This analysis forms the basis of the formulation of a slit-lamp technique called photometric oculometry, which makes it possible to measure intraocular distances. A comparison between ultrasonography and photometric oculometry in the determination of the ocular axial length was carried out. Measurements in 11 eyes showed statistical agreement, with a mean of 22.90 mm, SD +/- 1.815 (ultrasound), and a mean of 23.17 mm, SD +/- 1.667 (photometry). The principle involved in photometric oculometry is of special importance for the calculation of the blood-retinal barrier permeability to fluorescein by vitreous fluorophotometry, since the method allows the volume of the vitreous body to be estimated directly from the slit-lamp fluorophotometer recording.

Measurement of aqueous humor flow with scanning ocular fluorophotometers.

A one-dimensional scanning fluorophotometer (Fluorotron Master) and a two-dimensional scanning fluorophotometer (McLaren and Brubaker) were used to measure rate of aqueous humor flow in normal volunteers. The precision of three protocols of dye application and flow determination was investigated. In all three protocols rate of flow was determined by observing the rate of disappearance of topically-applied fluorescein during an 8-hour period. The three protocols studied were: 1) Two drops of 10% fluorescein washed away five minutes later immediately before beginning measurements of fluorescence. 2) Application of 0.25% fluorescein every 5 minutes for 30 minutes, 6 hours before beginning measurements. 3) Iontophoresis for 7 seconds and irrigation of eye immediately before beginning measurements. Rate of flow was calculated by the methods of Jones and Maurice. The results were compared to measurements made with a slit-lamp fluorophotometer using the technique described by Coakes and Brubaker. The most satisfactory method of measuring flow when either scanning fluorophotometer was employed was to instill fluorescein many hours before measurements begin (protocol 2).

Fluorescein kinetics in perilymph and blood: a fluorophotometric study.

A modified slit lamp fluorophotometer was used to determine fluorescein concentration changes in the perilymph, cerebrospinal fluid and blood of chinchillas after intravenous injection of 0.2 ml of fluorescein sodium. This new technique provides a means of determining quantitative changes of fluorescein concentration in the perilymph without the need to withdraw fluid samples through the round window membrane of cochlear wall. Fluorescein was observed to enter the perilymph between 1 and 2 minutes after injection, and it reached its peak concentration in the mean time of 23 minutes. The mean peak concentration was 4.20 X 10-6 g/ml. Both increasing and decreasing fluorescein concentration changes in the perilymph followed an exponential time course. Although the observations of cerebrospinal fluid fluorescence were thought to represent a composite of the fluorescence of the cerebrospinal fluid itself and the underlying brain stem blood vessels, the peak fluorescence did not exceed that observed in the perilymph. These observations support the view that most of the perilymph is produced in the cochlea by ultrafiltration from the cochlear blood vessels. The slit lamp fluorophotometer appears to be a satisfactory means of recording fluorescein concentration changes in the perilymph without disturbing the cochlear physiology by penetrating the labyrinth to obtain fluid samples.

Ophthalmic fluorophotometry: an improved slit-lamp fluorophotometer

The use of fluorescein dye for the study of ocular dynamics in ophthalmology is briefly reviewed. General principles for designing objective fluorophotometers for measuring the rate of change of fluorescein concentration are discussed. Details of the circuitry and performance of a new improved objective fluorophotometer using a quartz-halogen excitation source and a synchronous detector are presented. In a preliminary clinical trial the mean tear turnover rate for ten normal subjects was found to be 21±13% min−1.

Use of a Xenon Flash Tube As the Excitation Source in a New Slit-Lamp Fluorophotometer

A new objective fluorophotometer measures fluorescein mass or concentration in the cornea or anterior chamber. The excitation source is a xenon flash tube that allows the measurement of fluorescence to be made rapidly and conveniently. The instrument is designed for use in clinical studies requiring quantitative measurements of fluorescence in the tears, the cornea, and the aqueous humor.

The active transport of fluorescein by the retinal vessels and the retina.

1. The movement of fluorescein across the retinal surface of the rabbit's eye was estimated by measuring the concentration gradient of the dye in the vitreous body. These measurements were made in vivo by means of a slit-lamp fluorophotometer, or were taken from frozen sections of enucleated eyes.2. In the normal eye, fluorescein does not pass from the blood to the vitreous body across any part of the retina. When injected into the vitreous body it passes rapidly out across the entire retinal surface, even against a very large concentration gradient.3. A variety of metabolic and competitive inhibitors, effective in blocking organic anion transport in the kidney and liver, tend to abolish this unidirectional movement of fluorescein across the retina.4. The region occupied by the retinal vessels is more sensitive to inhibition than other areas of the retina. Occlusion of the vessels by diathermy prevents the exchange of fluorescein in this region.5. It appears, then, that there is an active transport of organic anions out of the vitreous body, both by the retinal capillaries and by the retina itself. The latter system is probably located in the pigment epithelium and seems to be carried forward to the rear surface of the iris.6. Since the walls of the retinal vessels of the rabbit are freely in contact with the vitreous body, the active transport must take place across the capillary endothelial cells themselves. These vessels have structural and permeability characteristics found only in the central nervous system and it is to be presumed that the anion transport system is shared by the capillaries of the brain.7. The function of the transport in the retina may be to protect the nervous tissue from toxic materials by preventing their entry from the blood or by removing products of metabolism conjugated as organic anions. Alternatively, the mechanism may be concerned in maintaining the normal adhesion of the retina to the choroid, since retinal detachment was observed to follow its total inhibition.

New methods of measuring the rate of aqueous flow in man with fluorescein

Two methods of determining the rate of loss of fluorescein from the aqueous humour in man are described. The dye is introduced into the cornea by means of iontophoresis and estimated in the eye with the slit-lamp fluorophotometer. In the first method the time course of the fluorescein concentration in the anterior chamber is observed, from which its turnover rate in the chamber is derived. In the second method measurements of the ratio of the total fluorescence of the eye to that of the aqueous humour lead to a direct evaluation of the aqueous flow rate. The errors and limitations of the methods are discussed and it is concluded that the second method, though generally more reliable, is inapplicable to blue-eyed subjects. In other cases there is good accordance between the results obtained by the two methods. In a small group of young normal volunteers the mean turnover rate found by the first method was 0·015 min and the mean rate of flow by the second method 2·5 μl/min.