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Biomedical subjects

F W Fitzke

Publications and source records attributed to F W Fitzke.

At least 109 records · Page 6Linked to original sources
PubMed1993

Symptomatic abnormalities of dark adaptation in patients with age-related Bruch's membrane change.

Some patients with age-related changes at the level of Bruch's membrane and good visual acuity report poor vision in dim light, fading vision in bright light, and a central scotoma noticeable in the dark. Ophthalmic examination, scotopic thresholds, and dark adaptation kinetics were recorded in 12 eyes of 12 patients with such symptoms. All had macular drusen which were hypofluorescent on fluorescein angiography in nine subjects, and six had evidence of prolonged choroidal filling on fluorescein angiography. Scotopic thresholds were depressed in six patients who all experienced a central scotoma in the dark or poor night vision. The kinetics of dark adaptation were abnormal in all 10 patients in whom reliable measurements were possible. The findings suggest that visual symptoms reflect abnormality of both scotopic sensitivity and the time course of dark adaptation in patients with age-related Bruch's membrane change.

Aged↗
PubMed1993

Three-dimensional visualization of confocal sections of in vivo human fundus and optic nerve.

A confocal scanning laser ophthalmoscope was used to image the human fundus in vivo at a series of 32 sections from near the retinal surface to deep within the optic nerve head. The optical sections were digitized and aligned to compensate for eye movement during image acquisition and stored on a computer. This registered stack of optical sections was reconstructed using specialized computational software. The three-dimensional volume rendering of the stack of optical sections results in a new way to view the in vivo optic nerve in three dimensions. This technique is of clinical importance since structural factors of the lamina cribrosa of the optic nerve may be important in glaucomatous damage. There may be diagnostic potential in the in vivo observation of the three-dimensional structure of the optic nerve.

Fundus Oculi↗
PubMed1992

Myopia following penetrating keratoplasty for keratoconus.

The frequent occurrence of spherical myopia after penetrating keratoplasty for keratoconus is partly the result of the excessive dioptric power of the grafted cornea which occurs when the diameter selected for the donor button is greater than the diameter of the host incision. This excessive power could be reduced by eliminating disparity between the diameters of the graft and host. To determine what proportion of the myopia in these eyes would persist as a result of axial myopia the axial lengths of 60 patients grafted for keratoconus and 25 emmetropic controls were compared. A keratometry, objective refraction, and contact probe ultrasonic biometry were performed on all eyes. A comparison of the results with a representational schematic eye indicated that the mean spherical refractive error of the grafted keratoconic eyes (-4.83 dioptres) was the combined effect of steepness of the corneal graft (mean radius of curvature 7.46 mm) and an abnormally great axial length (mean 24.84 mm). The increased axial length was mainly the result of elongation of the posterior segment of the globe with a small contribution from an increased anterior chamber depth. Though axial myopia is common in keratoconus, a further study of 70 keratoconic eyes that had not been grafted showed no statistically significant correlation between the posterior segment length and the severity of corneal ectasia. These data suggest that even if excessive corneal power is eliminated after penetrating keratoplasty for keratoconus the associated axial myopia would still produce a mean spherical refractive error of at least -2.8 dioptres.

Adult↗
PubMed1992

Abnormal dark adaptation kinetics in autosomal dominant sector retinitis pigmentosa due to rod opsin mutation.

The time course of dark adaptation was measured in 10 subjects from three families with autosomal dominant sector retinitis pigmentosa (RP) due to mutations in the first exon of the rod opsin gene. In each subject cone adaptation and the early part of the recovery of rod sensitivity followed the normal time course, but the later phase of rod adaptation was markedly prolonged. The recovery of rod sensitivity is much slower than that reported in any other outer retinal dystrophy. Using a model based upon primate data of rod outer segment length and turnover, we have calculated that the delayed phase of the recovery of rod sensitivity in the RP patients tested following strong light adaptation could be due in part to formation of new disc membrane with its normal concentration of rhodopsin rather than in situ regeneration of photopigment.

Adolescent↗
PubMed1992

Confocal imaging of the fundus using a scanning laser ophthalmoscope.

A confocal scanning laser ophthalmoscope (cSLO) was used to examine the effects of confocal optics on the image of the human fundus in vivo. Patients from a retinal clinic and a glaucoma clinic were examined using the cSLO in the confocal mode. A degree of optical sectioning could be achieved, and the results agree with a best axial resolution of 300 microns measured in a model eye. The main advantage of using a confocal system was found to be the improved contrast of the images. This improved the resolution of structures such as the lamina cribrosa and optic disc drusen which are seen in low contrast in conventional images. The improved contrast of the confocal images is partly achieved by excluding light which has been scattered within the plane of focus. Structures which multiply scatter light will become less visible with confocal optics and hard exudates were found to be an example of such a structure. The cSLO and the fundus camera are seen as complementary instruments rather than as alternatives for imaging the fundus. It is envisaged that confocal imaging will enable details of the fundus to be revealed which are at present not seen in conventional images.

Fundus Oculi↗
PubMed1992

Use of scrolled text in a scanning laser ophthalmoscope to assess reading performance at different retinal locations.

A new technique is described for assessing reading performance using a scanning laser ophthalmoscope. Letters of different sizes and contrasts were projected onto specific retinal locations of normal and low vision observers. Successive letters were scrolled in a horizontal direction at different speeds through a 'window'. Throughout the experiments the subjects' fundus and the retinal location of the stimuli could be visualized. With this scanning laser ophthalmoscope text-scrolling computer program the subject does not search for adjacent letters, and because the eye is held relatively stationary the tedious eye movement analysis incurred in other studies is reduced. Five retinal areas were investigated in two normal observers. The percentage of letters correctly identified decreased with eccentricity, increased velocity of the text and reduced text contrast. The reading performance of two patients, one with age-related macular degeneration and the other with juvenile macular disease, was investigated. Decrements in performance were related to morphology of the lesions.

Adult↗
PubMed1992

Abnormal dark adaptation and rhodopsin kinetics in Sorsby's fundus dystrophy.

Scotopic visual thresholds and time courses for dark adaptation were determined in eight patients with Sorsby's fundus dystrophy. Rhodopsin regeneration also was recorded in two. All patients had poor night vision and a visible yellow deposit at the level of Bruch's membrane that was confluent in the posterior pole. In retinal regions with the yellow deposit, scotopic thresholds were elevated, the rod-cone break was delayed or indistinct, the time courses for the rod portion of the dark adaptation curve was prolonged, and rhodopsin regeneration was slow in the one patient in whom measurements were made. In regions of ophthalmoscopically normal retina, dark adaptation was affected minimally, and in one patient, rhodopsin was regenerated at a normal rate. It was hypothesized that the abnormal dark adaptation and rhodopsin kinetics might be caused by reduced metabolic exchange across a thickened Bruch's membrane.

Adult↗
PubMed1992

Functional loss in age-related Bruch's membrane change with choroidal perfusion defect.

During a prospective study of age-related macular degeneration, evidence of diffuse Bruch's membrane disease was sought using fluorescein angiographic evidence of a prolonged choroidal filling phase. Dark-adapted static perimetry was done on eight eyes with this angiographic sign and on six eyes with a similar number of drusen but no manifest choroidal perfusion abnormality. Scotopic threshold was measured using the Humphrey automated perimeter and fine matrix mapping. In eyes without delayed choroidal perfusion, no discrete areas of increased threshold were found compared with the background sensitivity. By contrast, in seven of the eight eyes with fluorescein angiographic evidence of prolonged choroidal filling, discrete areas of scotopic threshold elevation (up to 3.4 log units) were recorded; these corresponded closely to regions of choroidal perfusion abnormality. It was postulated that diffuse deposits of abnormal material might account for both the perfusion abnormality and functional loss by acting as a diffusion barrier between the choriocapillaris and the retinal pigment epithelium.

Aged↗
PubMed1990

Quantification of lens opacification with a commercially available lensometer.

A clinical trial was undertaken to determine whether a commercially available lens opacity meter (LM701), which measures backward scattered light from the lens, provides reliable clinical information about the effect of lens opacities on visual acuity. At the 0.001 level of probability we found a significant relationship between the lens opacity meter reading and both the Snellen acuity and patient's age. For a given individual there was also a relationship between the difference in the lens opacity readings between eyes and the difference in the Snellen acuities. We could not demonstrate a relation between the lens opacity reading and either the refractive error, pupil size, or near visual acuity at this level of significance.

Adult↗
PubMed1990

Computer assisted analysis of fluorescein videoangiograms.

The efficient analysis of fluorescein videoangiograms requires immediate access to any frame in a video sequence and complete control over the time base during replay. It should also be possible to compare any two frames by rapid subtraction or to subtract any phase of the study from the remaining sequence. A program that performs all these tasks has been written for a low priced desk-top microcomputer. This should facilitate the clinical introduction of fluorescein videoangiography.

Data Display↗
PubMed1990

Long-term effect of acetazolamide in a patient with retinitis pigmentosa.

The authors studied the therapeutic effect of acetazolamide on a patient with autosomal dominant retinitis pigmentosa complicated by retinal edema. In addition to reduction of macular edema and some improvement of central vision, they found an unexpected progressive increase in extrafoveal retinal sensitivity with prolonged medication. It is proposed that the therapeutic effect is mediated by alteration of retinal pigment epithelial function and that disturbed polarity is restored to a more normal state.

Acetazolamide↗
PubMed1989

Acute macular neuroretinopathy.

Acute macular neuroretinopathy is a rare, unilateral, or bilateral condition of abrupt onset causing parafoveal scotomata and occasionally reduced visual acuity. The features are described in five new cases, and the evolution of the lesions described over a period of 9 months to 9 years. One patient was studied by fine matrix perimetry, which indicated a generalized elevation of thresholds at the macula early in the disorder, together with parafoveal scotomata. The thresholds improved over several months, and the scotomata became less dense. In another case, the scotomata were still present at 9 years, although at this time they were less dense. The condition appears to mainly affect young women, and in this group there is a high incidence of a recent immunologic disturbance suggesting an immune-based etiology.

Adult↗
PubMed1989

Probing visual function with psychophysics and photochemistry.

New methods using computer based measurements and image analysis techniques can improve and expand our ability to investigate non-invasively the function of the retina in patients. These can provide insight into the underlying mechanism of an abnormality and further our understanding of disease processes.

Dark Adaptation↗
PubMed1989

Corneal topography: a new photokeratoscope.

The assessment of the topography of the cornea is an important modality in the management of surgical procedures complicated by astigmatism. Additionally, the outcome of corneal refractive surgery is often best illustrated by photokeratoscopy. Currently available photokeratoscopes suffer from a number of deficiencies that include (i) the lack of topographic detail from the central cornea, (ii) the difficulty in transporting these units, (iii) the cost of such units. A photokeratoscope which addresses these shortcomings is described.

Cornea↗
PubMed1988

Clinical psychophysics.

New developments in clinical psychophysics allow a non-invasive assessment of visual function which may otherwise not be possible. Measurements of spatial and temporal contrast sensitivity functions, perimetric rod and cone sensitivity, colour vision testing, and newer tests such as hyperacuity thresholds may provide information about the mechanism of an abnormality, allow earlier detection of damage, determination of retinal function in the presence of ocular media disturbances, and allow more sensitive detection of the effects of treatment on visual function. Some methods are more effective in screening or monitoring patients over time while others can be used as research tools to investigate the underlying causes of visual dysfunction. Emerging technologies such as those based on video displays and computer generated graphics and advances in methodology provide potential for new applications. The selection of which aspect of visual function to test depends on the condition (e.g., retinal degeneration or glaucoma), the goals of the investigation, and the facilities available. These non-invasive methods can provide accurate information about retinal function and further improve our ability to quantify and document this most important aspect of the eye--its role in visual function.

Humans↗
PubMed1988

Myopia: induced, normal and clinical.

A review is given of lid-suture myopia in monkeys, of the natural lower field myopia in the pigeon eye, and of myopias in chick eyes produced by visual occluders. The ametropias produced by ophthalmic lenses, and the pharmacology of experimental myopia, are reviewed. Human studies are reviewed which can be taken as models of the experimental myopias. Two theories of myopic growth are outlined and evaluated.

Animals↗