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Biomedical subjects

P Hendrickson

Publications and source records attributed to P Hendrickson.

17 recordsLinked to original sources

Lateral differences indicate future glaucoma.

Since eye pairs are anatomically and pathologically asymmetrical, we attempted to determine whether the transition from ocular hypertension to glaucoma might be typified by lateral differences in either intraocular pressure (IOP), papillary excavation, or visual field. Such lateral differences were sought in a retrospective study of the medical records of 47 patients exhibiting ocular hypertension, of whom 25 remained hypertensives and 22 developed glaucoma during the period considered. Although all visual field indices in the latter group had remained within the normal range, the same side consistently yielded significantly worse results in mean sensitivity, and the absolute value for the lateral difference in these individuals was significantly higher than that found for the patients who did not develop glaucoma. Future glaucoma is manifested when the mean sensitivity remains worse in one eye.

Adult

Protracted ruthenium treatment of recurrent pterygium.

By combining excision with 106ruthenium irradiation in 17 patients previously operated on for persistently recurrent pterygium, we have devised an effective therapy that produces virtually no side effects and further prevents events recurrence. The ruthenium applicator shell was left in place for 2-3 h, yielding a total dosage of 2000 cGy. Only 2 of 17 patients suffered even slight recurrences, and 2 more had either motility disturbance or corneal haze. Through application of the internationally accepted total dosage of 2000 cGy, but at a relatively low dose rate, which especially protects the tissue responsible for proper healing, strong support is provided for the principle of protracted irradiation in recurrent (and possibly even primary) pterygium, permitting milder treatment and fewer recurrences.

Adult

[Autoregulation in the choroid].

The cerebral perfusion is continuously and highly sensitively dependent on arterial pCO2. Does the ocular perfusion behave in a similar manner? To answer this question, the authors measured the following parameters before and after the inhalation of 10% CO2: a) the increase of capillary pCO2, using a transcutaneous sensor, and b) the redness (pallor) of the retinal tissue, an expression of its hemoglobin content, was measured at two retinal locations with the Ocular Photometer (OPM). Initial results from young test-volunteers and patients with documented carotis stenoses show that the choroid is able to maintain constant its blood-volume even under changing loads.

Adult

[Discrete media clouding and its effect of contrast transfer coefficients, the pattern ERG and contrast sensitivity].

As a model for our study we selected 11 pseudophacic patients with secondary cataracts who experienced good postoperative visual acuity after extracapsular cataract extraction. Besides best visual acuity and contrast sensitivity Pattern-ERG (PERG) and Contrast-Transfer-Ratio (CTR) were measured before and after YAG-Kapsulotomy was performed. Visual acuity and contrast sensitivity increased in all patients after treatment, whereas CTR increased in eight patients. PERG was measured in five patients, in two cases its amplitudes were higher, the other measurements revealed unchanged or lower amplitudes. Our model shows that in addition to the usual psychophysic tests, with CTR and PERG there are objective methods available to measure discrete opacities of the visual system.

Cataract

[Sources of error in planimetry of the optic nerve].

No matter how "sophisticated" they may seem to have become, contemporary methods for bioplanimetry of the optic disc vary in precision; easily overlooked or neglected optical influences must, indeed, be taken into consideration; and, of greatest detriment to the meaningfulness of any and all such results is the fact that even "experts" have difficulty in uniformly and reproducibly indicating where the boundaries of the optic disc and its excavation actually lie.

Fluorescein Angiography

["ORO" (Opportunity Recycling in Ophthalmology) Project '90: Collection of usable ophthalmologic equipment for the Dr. Bétrix Clinic for Women/Cameroon].

The developmental-assistance entreprise, "Opportunity Recycling in Ophthalmology (ORO)", recycles used but still usable equipment in Ophthalmology and material from the storage-rooms of eye clinics and private ophthalmological practices to responsible recipients in the Third World. ORO was found in 1977 and was given "Honorable Mention" from "Prix Rolex à l'esprit d'entreprise" in 1978. The current project consists of locating, reconditioning, and organizing the transport of material for the Dr. A.-F. Bétrix Clinic in Kusseri, in the most northern province/Cameroon. As always, ORO is here, too, dependent on the generosity of clinics and private ophthalmologists.

Cameroon

Papillary circulation dynamics in glaucoma.

The ability of glaucomatous eyes to adjust to a sudden increase in intraocular pressure was investigated in nine certain glaucoma cases and in ten normal subjects. The "dynamic provoked circulatory response" (DPCR) was determined by continuously measuring the brightness of the papilla before (baseline), during, and after an abrupt artificial elevation in intraocular pressure. Following the onset of intraocular pressure elevation, the period during which the baseline brightness of the papilla persisted (latency time) was significantly (P less than 0.001) shorter in glaucomatous eyes (0.64 +/- 0.25 s) than in normal eyes (2.39 +/- 0.68 s). This led to the suggestion that the extent to which an eye can adjust to abruptly higher intraocular pressure is measurably reduced in glaucoma. That this effect can be quantified indicates a potentially useful method for detection and follow-up of glaucoma.

Aged

An injection/circulation-timing switch for angiography.

An injection/circulation-timing switch was developed to simply and precisely initiate the timing unit of the fundus camera for angiographic documentation. After starting the timer, the switch, mounted on the syringe used for injection of the tracer material, subsequently provides documentation of the total elapsed time of injection. Such quantitative data can enhance the evaluation of angiographic results and contribute to their universal comparability when combined with such qualitative data as injection location and total injectate.

Fluorescein Angiography

[Improved method of lens photograpy using retroillumination (author's transl].

Lens photography with a fundus camera using retroillumination is suited for long term follow-ups of senile cataract development. An improved method using a 9 grade colour standard is presented, which makes a comparative evaluation of the colour of the fundus reflex possible. A colour filter effect of the lens nucleus in nuclear sclerosis can thus be evaluated.

Aged

[Experimental fluorescein angiographic and microscopic investigations on laser treated rat eyes (author's transl)].

On fundi of pigmented rats, with Argon laser constantly 300 mW of power. 2 seconds exposure time and 50 microns spot diameter, coagulations have been performed. The eyes have been observed up till 3 months after the intervention, then angiographies were performed, and the following enucleated eyes have been examined with the fluorescence microscope. Neovascularizations and dye diffusions were observable mainly in the marginal zones of the arised cicatrices. The neovascularizations were starting from the choroid and penetrating into the outer retinal layers.

Animals

Observation of injected fluorescein diffusion after laser treatment of cat fundi. An experimental study with angiography and microscopy.

Argon laser coagulations with a power of 100 mW and 300 mW, exposure time 0.02 and 0.02 sec, and constant spot size of 100 microns were applied on normal cat fundi. From 1 and 2 hrs to 7 days after the coagulation, the treated eyes were observed angiographically and by fluorescence microscopy after dye injection; freeze dried eyes were examined under a fluorescence microscope. Abnormal dye leakages originated from the chorid and from retinal vessels were detected in the specimens examined within 72 hrs after the coagulation.

Animals

Iris angiography in cystoid macular edema after cataract extraction.

Iris angiography was performed on eight patients (nine eyes), who had cystoid macular edema postcataract extraction. The fundus fluorescein angiographies showed typical star-shaped, multiloculated staining of the macular area. The iris angiographies demonstrated moderate to massive leakage of dye from the iris, and possibly leakage of ciliary body vessels into the anterior chamber, thus evidencing the until now suspected but undocumented fact that fluorescein leakage is not restricted to the fundus vessels. These data tend to support the idea that this type of macular edema is due to a vascular abnormality, and not to altered vitreous mechanics.

Aged

Provoked iris ischaemia in the rabbit: A fluorescien angiographic study.

We studied experimental anterior segment ischaemia in rabbits by fluorescein angiography of the iris. Nine rabbits were subjected to diathermy occlusion of one or both long posterior ciliary arteries or to disinsertion and reattachment of up to 4 rectus muscles. Occlusion of one LPCA or up to 3 recti had only a minor ischaemic effect on the iris vessels. Occlusion of both LPCAs produced necrosis of the anterior segment or ischaemia of the iris detectable by angiography. Disinsertion of 4 recti produced small patches of transient ischaemia in those areas of the iris most distal from the LPCAs. When further surgery is planned after retinal detachment cyclodiathermy or strabismus operations, fluorescein angiography is a useful indicator of the vascular status of the iris and hence of the possibility of necrosis of the anterior segment.

Animals

[Monitoring the progress of lens opacities in cases of senile cataract by retro-illumination photography (author's transl)].

A follow-up study of lens opacities, utilizing retro-illumination photography with the fundus camera is described. After giving technical details, results are discussed and possible errors pointed out. If evaluation by planimetry or other devices is not possible, a useful procedure is the evaluation of simultaneous projected slides by a group of ophthalmologists not directly involved in the trial. This is demonstrated by testing the effect of 1-hydroxy-pyrido-(3,2alpha)-5-phenoxazone-3-carboxylic acid on the progress of senile cataract in a total of 48 eyes. Together with slit image photography of Brown (2, 3) the method of retro-illumination photography of the lens presented in this paper is a definite improvement in demonstrating the temporal course of cataract development.

Aged

[Experimental fluorescence angiographic and microscopic investigations on laser treated animal eyes (author's transl)].

The effects of laser coagulation on rat fundi were studied angiographically and with the fluorescence microscope. The coagulations were performed using constantly 300 mW and 0.2 second exposure time and 50 microns spot diameter. We observed the animals for 3 months, after which we could still observe dye diffusion by fluorescence angiography. With the fluorescence microscope we could localize these diffusions as originating from neovascularisation starting from the choroid. These new vessels penetrated subsequently into the exterior retinal layers. At the beginning of our observation time, the retinal vessels showed some sinuosities, dilatations and solitary stenosis, but no disturbance of circulation was demonstrable.

Animals