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Biomedical subjects

J A van Best

Publications and source records attributed to J A van Best.

At least 19 recordsLinked to original sources
PubMed1996

Long term changes in human corneal endothelium following toxic endothelial cell destruction: a specular microscopic and fluorophotometric study.

AIMS: To investigate the long term relation between corneal thickness, endothelial morphometric variables, and endothelial permeability in patients with endothelial cell counts under 900 cells/mm2 as a result of endothelial cell destruction after cataract surgery. METHODS: Eighteen patients developed the so called toxic endothelial cell destruction (TECD) syndrome following routine cataract surgery because of the intracameral injection of a toxic detergent residue. Ten patients with a mean (SEM) initial cell loss of 72% (2%) were followed for 4 years. Data were obtained at 6 months and 4 years postoperatively and compared between TECD eyes and contralateral control eyes. RESULTS: Mean (SEM) endothelial cell density of the TECD eyes increased from 642 (41) cells/mm2 to 849 (50) cells/mm2 at 4 years postoperatively (p = 0.005). There was no difference in coefficient of variation or percentage hexagonals between 6 months and 4 years postoperatively. Mean (SD) corneal thickness of the TECD eyes and control eyes was similar, 0.51 (0.02) mm and 0.49 (0.01) mm, respectively (p = 0.65). Mean (SD) endothelial permeability was also similar for TECD eyes and control eyes (4.3 (0.9) x 10(-4) cm/min and 4.4 (0.6) x 10(-4) cm/min, respectively (p = 0.57). There was no correlation between endothelial cell density, coefficient of variation, or percentage of hexagonal cells and endothelial permeability in the TECD eyes. In three patients a permanent corneal decompensation occurred. CONCLUSIONS: Four years after TECD corneal endothelial wound healing is stable and the barrier function has been restored.

Adult↗
PubMed1995

Measurement of basal tear turnover using a standardized protocol. European concerted action on ocular fluorometry.

BACKGROUND: The aim of this study was to compare basal tear turnover values of healthy volunteers in different countries. METHODS: Healthy volunteers aged between 20 and 70 years were selected in three European cities. Basal tear turnover values were calculated according to a standardized protocol from the decay of the fluorescein concentration in tears after instillation of 1-microliters drop of fluorescein in the conjunctival sac. Fluorescein concentration was measured with identical commercial fluorophotometers. A mono-exponential decay of fluorescein was assumed to represent basal tear flow. RESULTS: The mean tear turnover values were 13.1%/min +/- 4.6 SD (n = 4), 16.0%/min +/- 5.2 SD (n = 24) and 17.5%/min +/- 3.4 SD (n = 20) in Clermont-Ferrand (France), Leiden (The Netherlands) and Madrid (Spain), respectively. The differences between the values were not significant (Mann-Whitney test P > 0.09). CONCLUSIONS: The tear turnover in the different cities was similar. The methods used were simple and the software easy to use.

Adult↗
PubMed1995

Corneal endothelial permeability and aqueous humor flow using a standard protocol.

BACKGROUND: The study was carried out to compare corneal endothelial permeability and aqueous flow values of healthy volunteers measured in different countries with identical fluorophotometers using a standardized protocol. METHOD: Healthy volunteers aged between 20 and 70 years were studied in five European cities. Fluorescence scans of the anterior segment of both eyes were made using a commercial fluorophotometer. Beginning 4 h after instillation of four drops of fluorescein 10%, 12 scans of the anterior segment of each eye were performed in 2 h. The values of corneal endothelial permeability and aqueous flow were calculated with standardized software from the decay of the fluorescein concentration in the cornea and anterior chamber. RESULTS: The mean permeability values (x 10(-4) cm.min-1) +/- SD were 3.7 +/- 1.6 (n = 19; Coimbra, Portugal), 4.3 +/- 1.1 (n = 19; Frankfurt, Germany), 3.9 +/- 0.9 (n = 19; Leiden, The Netherlands) and 5.4 +/- 1.2 (n = 10; Milan, Italy). The values were not significantly different (ANOVA, P > 0.3), except those in Milan. The mean flow values (microliters.min-1) +/- SD were 2.3 +/- 0.9 (n = 17; Coimbra), 1.9 +/- 0.7 (n = 10; Cologne, Germany), 2.6 +/- 1.2 (n = 19; Frankfurt), 2.0 +/- 0.6 (n = 19; Leiden) and 1.7 +/- 0.8 (n = 10; Milan). The values were not significantly different (Kruskal-Wallis test, P > 0.1). CONCLUSIONS: Permeability and flow values in the different cities had similar values and standard deviations. The Concerted Action demonstrated the usefulness of a standardized protocol.

Adult↗
PubMed1995

Decreased basal tear turnover in patients with untreated primary open-angle glaucoma.

PURPOSE: To detect whether untreated primary open-angle glaucoma or ocular hypertension is associated with an impaired basal tear turnover. METHODS: Basal tear turnover was determined by fluorophotometry in 18 patients with newly detected, untreated primary open-angle glaucoma and 29 patients with untreated ocular hypertension. The results were compared with those of 27 age-matched control subjects. RESULTS: The basal tear turnover in glaucoma patients (mean +/- S.D., 11.4 +/- 3.1%/min) was 22% lower than in patients with ocular hypertension (14.7 +/- 3.0%/min; P = .0007) and 27% lower than in control subjects (15.7 +/- 5.3%/min; P = .001). Tear turnover of patients with ocular hypertension did not differ significantly from that of control subjects (P = .4). The basal tear turnover values were found to decrease with increasing vertical or horizontal cup/disk ratios (P = .004 and P = .008, respectively). CONCLUSIONS: Primary open-angle glaucoma, but not ocular hypertension, was found to be associated with an impaired basal tear turnover. Dry eye complaints may originate from decreased basal tear turnover as a result of glaucoma drug therapy as well as from primary open-angle glaucoma itself.

Adult↗
PubMed1995

Effect of timolol with and without preservative on the basal tear turnover in glaucoma.

AIMS: The purpose of this study was to assess whether the preservative benzalkonium chloride (BAC 0.01%) present in timolol induced a decrease in basal tear turnover and a deterioration of precorneal tear film in patients with glaucoma and ocular hypertension using topical timolol. METHODS: The basal tear turnover of 20 patients with open angle glaucoma or ocular hypertension was measured by computerised objective fluorophotometry when using topical timolol preserved with BAC and 2 weeks after changing to topical timolol containing no preservative. Evaluation of the precorneal tear film was done by measuring the break up time (BUT) before and 2 weeks after changing medication. RESULTS: The tear turnover of the patients before the change was 32% lower than that of healthy controls (mean tear turnover values (SD) (%/min): 10.7 (3.0) and 15.6 (5.4), respectively, p < 0.0001). A mean increase of 28% (47%) in the individual tear turnover values was found after the change to the preservative-free timolol (p = 0.04). The BUT values before the change of medication did not differ significantly from those after the change (p = 0.5) but both values were significantly lower than the values of healthy controls (p = 0.009 and p = 0.003, respectively). CONCLUSION: Preservative-free timolol solution has a favourable effect on the tear turnover of patients with glaucoma and ocular hypertension in comparison with timolol containing BAC. The integrity of the precorneal tear film persisted to be affected when using timolol without BAC. Timolol without preservative can be recommended in those patients who have keratoconjunctivitis sicca or a borderline tear production since BAC may exacerbate a dry eye state.

Benzalkonium Compounds↗
PubMed1995

Corneal epithelial permeability during extended wear of disposable contact lenses versus daily wear of soft contact lenses.

AIMS: The corneal epithelial permeability during extended wear of disposable contact lenses was compared with that during daily wear of soft contact lenses. The study was performed to verify whether the extended wear of disposable contact lenses would result in a higher permeability value than the daily wear of soft contact lenses. A higher permeability makes the cornea more vulnerable for bacterial infections and thus could explain the higher incidence of bacterial keratitis found in extended wear of disposable contact lenses in comparison with the daily wear of soft contact lenses. METHOD: The corneal epithelial permeability was determined by fluorophotometry in 33 healthy volunteers after the wear of soft, daily wear contact lenses for at least 6 months. Thereafter the determination was repeated in each volunteer after extended wear of disposable contact lenses for 1 month. The permeability in 34 healthy non-contact lens wearing volunteers was determined as a control. The permeability value was calculated from the amount of fluorescein that passed into the cornea after application by means of an eyebath. RESULTS: The mean permeability values after daily and extended wear were 0.032 nm/s and 0.031 nm/s, respectively. The values were not significantly different (Wilcoxon paired test p > 0.5). The mean permeability for the non-contact lens wearing controls was 0.042 nm/s. CONCLUSION: The results do not sustain the explanation that a difference in permeability value is the main cause of the increased incidence of keratitis during extended wear of disposable contact lenses in comparison with daily wear.

Adolescent↗
PubMed1995

Is glaucoma associated with an increased risk of cataract?

AIMS: The risk of developing cataract in patients with untreated glaucoma or with ocular hypertension was evaluated by comparing the values of lenticular autofluorescence and light transmission in 16 patients with primary open angle glaucoma and 22 patients with ocular hypertension with those of 24 healthy controls. METHODS: Increase of lenticular autofluorescence and decrease of transmission values in comparison with controls were considered to be precursors of cataract. The values of both variables were determined by fluorophotometry. Each value was normalised for age by dividing it by the value for a healthy control of the same age. RESULTS: The mean age normalised autofluorescence and transmission values of all patients did not differ significantly from those of the controls (difference < 5%; p = 0.6 and p = 0.2, respectively). Also the mean age normalised autofluorescence and transmission values between glaucoma and ocular hypertension patients did not differ significantly (p = 0.8 and p = 0.9, respectively). CONCLUSION: The study indicates that untreated primary open angle glaucoma or untreated ocular hypertension do not seem to increase significantly the risk of developing cataract.

Adult↗
PubMed1995

Endogenous fluorescence of ocular malignant melanomas.

The endogenous fluorescence of human choroid, sclera, and retinal pigment epithelium (RPE) in normal tissue and tissue with uveal melanoma was studied in vitro by a non-invasive and non-destructive fluorescence technique which had previously been applied for the diagnostic evaluation of pigmented lesions of the skin. The fluorescence of the normal choroid is rather dark, the normal sclera exhibits blue fluorescence and the RPE bright yellow fluorescence due to deposits of lipofuscin. In choroidal melanoma, the lipofuscin granulae at the level of the retinal pigment epithelium are cleaved off above the tumour and broken up into small remnants. The fluorescence intensity emitted from the tumour is rather low which agrees with previous findings on skin melanomas. The results may become interesting for diagnostic evaluation of uveal melanomas, uveal naevi, and pigmented conjunctival tumours by endogenous fluorescence.

Choroid Neoplasms↗
PubMed1994

Effects of aldose reductase inhibition with tolrestat on diabetic retinopathy in a six months double blind trial.

To study the effects of the new aldose reductase inhibitor tolrestat on diabetic retinopathy, 31 diabetic patients with various degrees of retinopathy were randomly assigned to either tolrestat (200 mg once daily) or placebo treatment for six months. Separate morphological features of diabetic retinopathy were assessed by fundus photography and fluorescein angiography before and at the end of the study. The results showed some amelioration of clinical signs of diabetic retinopathy during aldose reductase treatment. Hard exudates, intraretinal hemorrhages and focal fluorescein leakage increased on average in the placebo and decreased in the tolrestat group. The difference was statistically significant for focal fluorescein leakage only. The permeability of the blood retinal barrier was determined by vitreous fluorophotometry before and at the end of the study. No change in permeability values was found.

Administration, Oral↗
PubMed1994

The blue-green autofluorescence of the human ocular lens after the wear of PMMA contact lenses.

The green ocular lens autofluorescence was determined in 30 Poly Methyl Meth Acrylate (PMMA) contact lens wearing volunteers and compared to that of 21 healthy non-contact lens wearing controls to determine whether a contact lens, reducing UV-A intensity reaching the eye, might protect the ocular lens against cataract formation. Increased autofluorescence was considered an indicator of increased probability for cataract formation. A multiple regression procedure revealed a significant yearly increase of autofluorescence with age (p < 0.01) which did not differ significantly (p > 0.86) from that in the controls. The regression procedure also revealed a decrease of the autofluorescence as a function of contact lens wear, but this decrease was not significant (p = 0.3). The order of magnitude of the decrease (-25%) corresponded to that of the calculated decrease in UV-A intensity at the ocular lens (-39%). This study could not support the thesis that cataract formation can be prevented by wearing PMMA contact lenses.

Adult↗
PubMed1994

Analysis of tear fluid proteins in insulin-dependent diabetes mellitus.

Secretory immunoglobulin A, lactoferrin, lysozyme and tear specific pre-albumin were analyzed in stimulated tear fluid of 25 diabetic patients without retinopathy and in 29 diabetic patients with (pre) proliferative retinopathy using high performance liquid chromatography. Results were compared to those obtained in 26 healthy controls to determine the effect of diabetes mellitus on the exocrine function of the main lacrimal gland. Sodium dodecyl sulfate polyacrylamide gel electrophoresis onto minigels was performed on 20 tear samples for verification of high performance liquid chromatography fractions recorded. The mean total protein values in tear fluid (Bradford assay) of diabetics without retinopathy, with retinopathy and healthy controls did not differ significantly (mean in mg/ml +/- SD: 6.4 +/- 2.2, 5.9 +/- 2.0 and 5.7 +/- 1.7, respectively; Mann-Whitney; p > 0.02). High performance liquid chromatography showed an increased secretory immunoglobulin A and decreased peak 5 OD280 (+56% and -38%, respectively; p < 0.02) in patients without retinopathy, whereas in patients with retinopathy lysozyme was increased (+27%; p < 0.01) and tear specific pre-albumin and peak 5 OD280 decreased (-24% and -42%, respectively; p < 0.04), when compared to healthy controls. These inconsistent differences do not uniformly suggest an exocrine dysfunction of the main lacrimal gland in diabetic patients.

Adolescent↗
PubMed1994

Contact lens care solutions and corneal epithelial barrier function: a fluorophotometric study.

The aim of the study was to evaluate the effect of residual concentrations of two contact lens care solutions (hydrogen peroxide and polyaminopropyl biguanide) on corneal barrier function in vivo. The barrier function was determined by fluorophotometric measurement of corneal epithelial permeability in 30 contact lens wearing healthy subjects after 1 month's use of each of the solutions. All participants except one had corneal epithelial permeability values within the range for non-contact lens wearing healthy volunteers (0.011-0.061 and 0.008-0.090 nm/s, respectively). The deviating value (0.14 nm/s) was due to improper use of the contact lens care system. No statistical significant difference between the permeability values after use of the two contact lens care solutions was found (Wilcoxon ranked paired test: p = 0.2). It can be concluded that both solutions do not have harmful effects on corneal epithelial barrier function, provided the handling instructions are followed.

Adolescent↗
PubMed1993

Spectral sensitivity of the blood-retinal barrier at the pigment epithelium for blue light in the 400-500 nm range.

To specify the spectral sensitivity of the retinal pigment epithelium (RPE) for blue light damage, pigmented rabbits were exposed to light of 408, 418, 439, 455, 485, and 500 nm (half-peak bandwidth approximately 12 nm). The range of radiant exposure was 15-275 J cm-2 (1.7-19 mW cm-2 for 0.5-5 h). Vitreous fluorophotometry was used to functionally evaluate the blood-retinal barrier at the RPE in vivo, and electron microscopy to visualize RPE ultrastructure in vitro. A significant increase in permeability of the blood-retinal barrier was seen only after exposure to light of 418 nm. Radiant exposure at threshold for permeability increase was 18 J cm-2. Electron microscopy of the RPE demonstrated dispersion and clumping of melanin granules. The results suggest that the RPE is most sensitive to light in the range 412-425 nm, possibly due to damage-mediating chromophores such as cytochrome c oxidase and lipofuscin.

Animals↗
PubMed1992

Effect of morphological abnormalities on blood retinal barrier permeability in diabetic retinopathy.

The morphological base for the impaired function of the blood retinal barrier was studied in 50 eyes of 10 insulin dependent and 21 non-insulin dependent patients with various levels of diabetic retinopathy. The permeability of the blood retinal barrier (PBRB) was determined by vitreous fluorophotometry with correction for autofluorescence, lens transmission and non-protein bound plasma fluorescein concentration. Morphological abnormalities of diabetic retinopathy assessed by fundus photography and fluorescein angiography were individually scored on a decimal scale and related to the PBRB by multiple regression analysis. The PBRB was not correlated to morphological abnormalities of non-proliferative retinopathy [(1) microaneurysms, (2) hard exudates, (3) soft exudates, (4) intraretinal hemorrhages, (5) fluorescein leakage, and (6) capillary closure, p greater than 0.3]. The PBRB was correlated to morphological abnormalities of (pre)proliferative retinopathy [(1) intraretinal microvascular abnormalities (SIRMA) and (2) new vessels (Sneo): PBRB = A+B.SIRMA + C.Sneo with PBRB in nm/sec, A = 1.5 +/- 0.5, B = 0.9 +/- 0.2 and C = 1.7 +/- 0.4, R2 = 0.65, p less than 0.0001]. It can be concluded that the increased blood retinal barrier permeability in diabetic patients is mainly due to (pre)proliferative abnormalities and not to non-proliferative abnormalities.

Blood-Retinal Barrier↗
PubMed1992

Toxicity of 1-(beta-D-arabinofuranosyl)cytosine after intravitreal injection in the rabbit eye.

The retinal toxicity of intravitreally injected 1-(beta-D-arabinofuranosyl)cytosine (cytarabine) was examined in 7 chinchilla rabbits to determine if cytarabine can be used as local therapy for vitreoretinal non-Hodgkin's lymphoma. Fractionated dose of 600 micrograms, 1500 micrograms, and 2700 micrograms cytarabine in stabilized saline were given intravitreally in one eye (2 x 300 micrograms, 5 x 300 micrograms, and 3 x 900 micrograms, respectively, with an interval time of 24 h) and stabilized saline in the other eye as control. Toxic effects were evaluated with biomicroscopy, direct ophthalmoscopy, fluorophotometry, electroretinography, light, and electron microscopy. Toxic effects were found with the 1500 micrograms and 2700 micrograms doses only. They consisted of a temporary impairment of the blood retina barrier function for fluorescein as measured by fluorophotometry and an irreversible change of the b-wave in the electroretinograms. No histopathologic changes were seen under the light microscope. Electron microscopic examination showed aberrations in the synaptic pedicles of the photoreceptor cells at a dose of 1500 micrograms cytarabine. The results suggest that the cytarabine dose that is expected to be therapeutic for vitreoretinal non-Hodgkin's lymphoma (about 90 micrograms given in three doses of 30 micrograms) is non-toxic for ocular structures.

Animals↗
PubMed1992

Fluorophotometric assessment of tear turnover under rigid contact lenses.

To examine the effect of rigid contact lens design on tear turnover the left and right eyes of 25 healthy volunteers were randomly fitted with either a spherical or an aspherical contact lens. Tear turnover is defined as the percentage of decrease of fluorescein concentration in the tear film per minute as a result of tear flow after instillation of fluorescein and can be determined with a fluorophotometer. A drop of fluorescein (1 microliter, 2%) was instilled in each contact lens-wearing eye, whereafter the decrease of the fluorescein was measured for about 30 min. The test was repeated without contact lenses. No statistically significant difference was found between the tear turnover in the spherical, the aspherical, and the non-contact lens-wearing eyes (mean values +/- SD: 15.2 +/- 4.9, 15.6 +/- 5.9, and 16.9 +/- 6.8%/min, p > 0.20).

Adult↗