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J V Siertsema

Publications and source records attributed to J V Siertsema.

17 recordsLinked to original sources
PubMed1995

Morphometric analysis of the corneal endothelium with three different specular microscopes.

The morphometry of the central corneal endothelium of 10 eyes in 10 subjects was analyzed with three different specular microscopes. Computer-assisted analysis was performed with only two microscopes (Zeiss and Keeler Konan sp 3300) because the third microscope (Topcon sp 1000) could not be adapted to our computerized system. With this Topcon microscope a grid with standard densities was used to compare the images with, in addition, we also performed manual cell counting on the same Topcon images. The coefficient of variation of the cell analysis of three different images per cornea with the four methods varied between 3.4 and 4.7 percent. One-way analysis of variance showed a significant difference between the Zeiss and the other microscopes. So only the Keeler Konan and the Topcon microscopes could be used interchangeably. The computerized image analysis permitted also an evaluation of the hexagonality. The results of polygonality were not significantly different between the Zeiss and the Keeler Konan. For clinical purposes the Topcon specular microscope is more advantageous than the other two methods, since it is the most rapid way to record and analyze specular images. But for more precise measurements an image processing system is indispensable.

Adult↗
PubMed1995

Comparative study of three semiautomated specular microscopes.

We compared two clinical video-assisted specular microscopes (Zeiss, noncontact, and the wide-field Keeler Konan sp 3300, contact) with an autofocus microscope (Konan noncon Robo-ca sp 8000, noncontact) with built-in analyzing software by studying the morphometry of the central corneal endothelium of 12 eyes in 12 patients. The mean coefficients of variation of the cell size analysis of three successive images per cornea for the three methods were 3.9%, 4.0%, and 2.2%, respectively. One-way analysis of variance showed a significant difference in the mean cell area measured with the three methods; there was no significant difference in the results of hexagonality (pleomorphism) and coefficient of variation (polymegathism). Although each microscope showed a high reproducibility, we do not recommend using the three interchangeably. The Konan noncon Robo-ca sp 8000 specular microscope provides a rapid morphometric endothelial analysis. The Keeler Konan sp 3300 is better for more detailed studies and photography of the corneal endothelium.

Adult↗
PubMed1993

Negative implant. A retrospective study.

Implantation of a negative power intraocular lens is one of the options for surgical correction of high myopia. We studied 36 eyes with a Fechner Worst Claw Lens, implanted in Groningen between March 1987 and November 1991. The preoperative myopia ranged from -7.00 to -30.00 diopters. Twenty one eyes had a follow up period of more than 12 months. The IOL power was calculated with the van der Heyde method. Correction within 1 diopters of emmetropia has been achieved in 55.5% of the cases. Deviation of more than 2 diopters occurred in 25%. In 24 eyes the best corrected postoperative visual acuity improved. Due to the IOL the retinal image increases in size as compared to spectacle correction. In none of the cases complications were encountered during surgery. In the postoperative period one IOL had to be replaced because of an error made in the calculation of the lens power. In one case endothelial decompensation occurred, probably due to a combination of compulsive eye rubbing and a preexisting cornea guttata. The rim of the IOL optic is the part which is the closet to the endothelium. Our recommendation is that one should avoid indentation of the cornea. No other serious complications occurred in this study.

Adult↗
PubMed1993

Automated video image morphometry of the corneal endothelium.

The central corneal endothelium of 13 eyes in 13 subjects was visualized with a non-contact specular microscope. This report describes the computer-assisted morphometric analysis of enhanced digitized images, using a direct input by means of a frame grabber. The output consisted of mean cell area, cell density, frequency distribution of the individual cell area, and cell polygonality. Results showed that the mean coefficient of variation of images analyzed three times consecutively was 0.95 percent. The cell analysis of three different images of the same subject was accurate, with a mean coefficient of variation of 4.2 percent.

Adult↗
PubMed1992

Serotonin (5-HT) and the rat's eye. Some pilot studies.

Serotonin (5-hydroxytryptamine, 5-HT) is a biogenic amine which has a multitude of more or less clearly established effects on peripheral vessels. It influences blood viscosity, platelet aggregation, and vasoconstruction and -dilatation, it enhances capillary permeability, it is the precursor of melatonin (a hormone with diurnal production in the eye). Because of these actions a role for serotonin in the development of glaucoma and diabetic retinopathy might be suspected. In a series of pilot studies on rats the effects of serotonin on the anterior and posterior segments of the eye were studied. Serotonin had marked influence on the retinal and choroidal vasculature. The optic disk seemed to be very sensitive to serotonin. Possibly it had an influence on the blood-retinal barrier. It caused transient cataracts, probably by decreasing the production of aqueous. It blocked tropicamin-induced mydriasis. The techniques and provisional results of measurement of serotonin in human aqueous are also described.

Animals↗
PubMed1991

Lens reflectometry with a CCD video camera and computer image analysis.

Lens reflectometry is a useful method of determining the back scatter of light from the cataractous lens. Making use of normal programmes, the personal computer can be used for the quantitative determination of the lens reflex, as seen in the slit-lamp image. If three different images of the same eye are compared, it appears that the mean variation in the back-scatter readings made by our method is 8.3%.

Aged↗
PubMed1983

Fluoro-photometry in myotonic dystrophy.

We found pigment alterations in the anterior segments of the eyes of patients with myotonic dystrophy. We therefore performed fluoro-photometry in a group of ten myotonic patients and the results were compared with those of a group of normal persons. The fluorescence levels in the aqueous and vitreous of the myotonic eyes appeared to be two or three times higher than in the normal eyes. This brings us to the conclusion that myotonic eyes have a defect in the blood-ocular barriers.

Aqueous Humor↗
PubMed1983

Clinical applications of fluorometry.

An instrument has been developed that measures in ten seconds the level of fluorescein along a scanning line from the retina to the cornea. With spatial resolving power of 1.1 mm in the eye, concentrations of 1 X 10(-8) gr/ml fluorescein and higher are detectable. In this way an indication of the integrity of the blood-ocular barriers is achieved. In uveitis the dysfunction is mainly localised at the blood-aqueous barrier while in diabetic retinopathy the blood-retinal barrier is predominantly affected. Sources of error are discussed.

Adult↗
PubMed1982

Quantitative determination of fluorescein in the anterior chamber and vitreous body.

The blood-retinal barrier plays an important role in the physiology of the retina, the vitreous body and the aqueous humour. Many intra-ocular processes cause a breakdown of this barrier and this results in an increase in the concentration of fluorescein in the vitreous and the aqueous after it has been injected intravenously (Cunha-Vaz et al., 1975). In our clinic we have built an apparatus for the quantitative determination of the concentration of this fluorescein in both healthy and pathological eyes (Brubaker and Coakes, 1978). The goal of the present communication is to invite other workers with similar interests to compare their results with ours.

Aged↗
PubMed1981

Stereoscopic fluorescein angiography of the fundus.

The fundus of the eye is a three-dimensional organ. The usual two-dimensional representation of the angiogram provides us with incomplete information. It is true that it is usually possible by indirect means to deduce at which level the pathological process is taking place, but a simple technique enables one to register and project the angiogram stereoscopically. This gives the observer a direct visual impression of the spatial proportions of the pathological process.

Fluorescein Angiography↗
PubMed1981

The Kodak TP 2415: a good negative film for fluorescence angiography.

The Kodak TP 2415 is a panchromatic film which at the exposure index of ASA 200 combines a high resolving power (320 lines/mm) with an extremely fine granularity (RMS 8). It can be processed within 150 s by a modified Kodak Prostar I-L processing machine. These properties make this film very suitable to be used in clinical fluorescence angiography.

Fluorescein Angiography↗
PubMed1978

[Fixing the time and date of photograph (author's transl)].

A system is described to obtain on photographs and slides an automatic printout of patient number, eye and time. The time is recorded in minutes, seconds and tenth of seconds or in minutes and seconds. The time-recording can be switched off if only patient and eye identification is needed.

Documentation↗
PubMed1977

Changes in the structure of intra-ocular nylon.

When using a nylon thread for the attachment of a pseudophakos to the iris, it may happen that the suture is slung tightly around the implant-lens. In such a case this constitutes a clinical experiment where is one and the same eye one part of the nylon thread is in its normal state (the cut-off ends) and the rest is in a stretched state, both under the same environmental conditions and for the same length of time. The differences in structure of the parts of the nylon thread are thus fully comparable. Clinical observatons show that when the nylon thread is under tension it will be eroded by chemical influences. It does not make any difference whether the nylon is used for corneal, scleral or intra-ocular suturing. The duration of the observations is still too shor to predict the behaviour of nylon which is not stretched.

Cataract Extraction↗
PubMedDate not supplied

Correction of high myopia with the Worst myopia claw intraocular lens.

BACKGROUND: Phakic anterior chamber lenses is one of the modalities used to correct high myopia. We report the initial results of our prospective study on the Worst myopia claw intraocular lens (IOL) that is fixated to the anterior iris. METHODS: We studied 35 eyes in 18 patients with a preoperative myopia ranging from -6.00 to -28.00 diopters (D). The follow up ranged from 6 months (n = 15) to 12 months (n = 20). RESULTS: In 26 (74.3%) eyes, the postoperative spherical equivalent refractive error was within 1.00 D of emmetropia. The mean refraction was stable between 1 to 2 months and 12 months. The mean spectacle-corrected visual acuity improved from 20/50 to 20/40. The straylight measurements did not show a significant increase postoperatively (p = .64). The mean endothelial cell loss was 5.6% (range, +6.3% to -22.6%) at 6 months, and 8.9% (range, +0.77% to -23.5%) at 12 months. We did not encounter major complications. CONCLUSION: Implanting a Worst myopia claw IOL in high myopic eyes resulted in a stable, reasonably accurate refractive outcome. This group of patients will be followed longer because of concern over ocular complications with this technique.

Adolescent↗