Biomedical subjects

F W Fitzke

Publications and source records attributed to F W Fitzke.

At least 73 records · Page 4Linked to original sources

PubMed1997

Laser treatment in subjects with high-risk clinical features of age-related macular degeneration. Posterior pole appearance and retinal function.

OBJECTIVES: To verify that a few laser lesions in the posterior pole can cause drusen to resolve in patients with age-related macular degeneration, and to document central retinal sensitivity as drusen resolve. DESIGN: In a pilot study, 12 patients considered to be at high risk for sight-threatening complications from age-related macular degeneration were treated with 12 argon laser lesions in the posterior pole, with review for 12 to 24 months. RESULTS: Choroidal neovascularization developed in 1 patient 8 months after treatment, with consequent loss of central vision. In 9 of the remaining 11 patients, high-risk characteristics of drusen were reduced. Four patients had retinal pigment epithelial depigmentation, and all maintained 20/40 visual acuity at 12 months. One patient lost 3 lines of vision due to geographic atrophy after 12 months. Scotopic retinal threshold was elevated before treatment in 8 patients, compared with an age-matched comparison group. Of these, 4 patients underwent retesting 3 to 6 months after treatment, and all had improved thresholds, but only 1 patient sustained the improvement at 12 months. At 12 months, 3 of the 8 patients showed an improvement in their mean retinal threshold. Of those in whom the mean retinal threshold worsened, the mean elevation in threshold was not more than 0.6 log units. CONCLUSIONS: A few laser lesions in the posterior pole leads to resolution of drusen. There does not appear to be an increased risk for choroidal neovascularization. Retinal threshold measurements show no indication of geographic atrophy at 1 year, but cannot be excluded as a late outcome. Laser treatment may reduce the risk for profound sight-threatening lesions in age-related macular degeneration.

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PubMed1997

In vivo fundus autofluorescence in macular dystrophies.

OBJECTIVE: To document the deviation from normal of fundus autofluorescence in patients with inherited macular dystrophies. METHODS: The intensity and spatial distribution of fundus autofluorescence was documented in 118 patients with inherited macular dystrophies by means of a confocal laser scanning ophthalmoscope, and the images were compared with the fundus appearance and fluorescein angiograms. RESULTS: Background autofluorescence appears to be elevated in all forms of macular dystrophies examined. The pale deposits at the level of the retinal pigment epithelium in disorders such as Best disease, adult vitelliform macular dystrophy, and fundus flavimaculatus were consistently associated with higher levels of autofluorescence than the background signal. There was no strong correlation between the intensity of autofluorescence and the fluorescein angiographic sign of a dark choroid. Increased levels of autofluorescence were present in a subject with a mutation known to cause macular dystrophy but in whom there were no manifest ophthalmoscopic or functional abnormalities. CONCLUSIONS: All dystrophies examined have in common accumulation of autofluorescent material in the retinal pigment epithelium to a greater degree than that seen with age. The abnormal high background autofluorescence associated with inherited macular dystrophies confirms the impression derived from histological studies that these disorders affect the entire retinal pigment epithelium. The lack of correlation between autofluorescence and the presence of a dark choroid implies that there may be different fluorophores in different disorders. The pale deposits at the level of the retinal pigment epithelium-Bruch membrane seen in macular dystrophies have similar autofluorescence characteristics. This technique may be useful in detecting the abnormal phenotype in early disease.

Adolescent↗

PubMed1997

Fourier transform analysis of human corneal endothelial specular photomicrographs.

Fourier analysis of in vivo human corneal endothelial cell structure was investigated using specular photomicrographs for a range of ages from less than one year to over 70. The theoretical basis for this analysis was investigated using mathematical models of cell structures where the elements determining their form could be modified in a controlled and quantified manner. The resulting Fourier transform properties were related to properties of cell structure. The experimental factors underlying this analysis were then studied using digitized images of corneal endothelial cells. It was found that the Fourier transforms provided quantitative descriptions of population cell size and organisation. For the smaller, more regular cell structure from the younger eyes, the expected larger rings of the Fourier transforms were demonstrated. Specular photomicrographs of older eyes gave rise to smaller diameter rings in their Fourier transforms. These results are consistent with the previous studies which used manual tracings of human endothelial cell patterns. This is the first demonstration of the direct Fourier analysis of clinical human corneal specular photomicrographs.

Adolescent↗

PubMed1997

How often do patients need visual field tests?

BACKGROUND: This study was undertaken to determine whether the interval between visual field tests affects the ability to detect progressive glaucomatous field loss. METHODS: One hundred and nineteen retinal locations which were deteriorating significantly by > or = 1 dB/ year (untreated normal tension glaucoma patients: 6 eyes) were studied. Analysis was repeated using 'thinned' visual field tests: one test per year instead of the complete three per year over a period of 4 years. RESULTS: The 'thinned' tests identified only 45.4% of the deteriorating points over the 4-year period. Furthermore, there was a mean delay of 1.10 years in detection (P < 0.01). CONCLUSIONS: Less frequent visual field testing detects fewer progressing locations and detects them later.

Adult↗

PubMed1997

Effect of surgery on visual field progression in normal-tension glaucoma.

PURPOSE: The effect of intraocular pressure-lowering surgery on the rate of visual field progression in normal-tension glaucoma (NTG) was studied. METHODS: Seventeen patients with NTG who underwent trabeculectomy in one eye for worsening visual field loss were included in the first part of the study. All patients had Humphrey 24-2 visual fields at the rate of 2-3 fields per year. Pointwise linear regression analysis of the visual field data was done separately for the preoperative and postoperative periods. This was performed for both operated and fellow eyes. The mean slope (MS), which indicates rate of visual field progression, was calculated. Change in MS was correlated with change in intraocular pressure (IOP). For the second part of the study, 11 patients who had a minimum of 4 visual fields and 18 months of follow-up before surgery were identified. Using the preoperative fields, the rate of sensitivity loss for each visual field location in the operated eye was ascertained for every patient. This rate of loss was extrapolated to generate the expected visual fields, assuming an unchanged rate of progression. The mean sensitivity of the expected visual field was compared with that of the actual field at the last follow-up. RESULTS: The MS in the operated eyes improved from -2.97 +/- 3.21 (mean +/- SD) in the preoperative period to 0.53 +/- 3.83 (P < 0.005; Student's t test) postoperatively. In the fellow eyes the MS changed from -1.78 +/- 2.55 to -1.43 +/- 3.01 (P = 0.754). There was a weak correlation between change in MS and percentage IOP decrease (correlation coefficient 0.39). The difference in mean sensitivity between the expected and actual visual fields was -3.72 dB (P = 0.002), and was better in the actual field. CONCLUSIONS: In this study, surgical lowering of IOP resulted in a slower rate of visual field loss in the operated eye.

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PubMed1997

Improving the prediction of visual field progression in glaucoma using spatial processing.

PURPOSE: The authors show how the predictive performance of a method for determining glaucomatous progression in a series of visual fields can be improved by first subjecting the data to a spatial processing technique. METHOD: Thirty patients with normal-tension glaucoma, each with at least ten Humphrey fields and 3.5 years of follow-up, were included. A linear regression model of sensitivity against time of follow-up determined rates of change at individual test locations over the first five fields (mean follow-up 1.46 years; standard deviation = 0.08) in each field series. Predictions of sensitivity at each location of the field nearest to 1 and 2 years after the fifth field were generated using these rates of change. Predictive performance was evaluated by the difference between the predicted and measured sensitivity values. The analysis was repeated using the same field data subjected to a spatial filtering technique used in image processing. RESULTS: Using linear modeling of the unprocessed field series, at 1 year after the fifth field, 72% of all predicted values were within +/- 5 dB of the corresponding measured threshold. This prediction precision improved to 83% using the processed data. At the 2-year follow-up field, the predictive performance improved from 56% to 73% with respect to the +/- 5 dB criterion. CONCLUSIONS: Predictions of visual field progression using a pointwise linear model can be improved by spatial processing without increased cost or patient time. These methods have clinical potential for accurately detecting and forecasting visual field deterioration in the follow-up of glaucoma.

Adult↗

PubMed1997

Quantitative analysis of the lamina cribrosa in vivo using a scanning laser opthalmoscope.

PURPOSE: Structural changes in the lamina cribrosa have been implicated in the pathogenesis of glaucomatous optic nerve atrophy. The purpose of this study was to develop a method for morphometric analysis of the lamina cribrosa pores in vivo, using a scanning laser ophthalmoscope. METHODS: A prototype Zeiss confocal laser scanning ophthalmoscope was used to acquire images of the lamina cribrosa. The images were digitised and aligned to compensate for eye movements. Thirty-two consecutive images were averaged to reduce noise. The images were processed to adjust for luminance gradients prior to segmentation and analysis. Details of the image processing are described. RESULTS: The end result of processing the images was a binary (black and white) image that can be used for automated computer assisted measurements. The pores of the lamina cribrosa are well represented and retain their overall shape in the binary image, as judged by superimposing the binary image on the unprocessed image. We also established the repeatability, reproducibility and intercession variability of this technique. Repeated images of the internal lamina cribrosa of 10 patients were acquired by two observers in two separate visits, and the images were processed before automated computer measurements. The parameters evaluated were number of pores, area covered by the pores and area covered by the visible lamina cribrosa. The coefficient of variation for number of pores, pore area and lamina area was 6.9%, 2.1% and 4.3% for observer A and 5.5%, 2.1% and 5.8% for observer B. Pearson product moment correlation coefficient between the two observers was 0.94, 0.99 and 0.97 for the above parameters respectively. There was no significant difference between the measurements on visit 1 and 2 for both observers. CONCLUSIONS: The technique described allows, for the first time, in vivo morphometry of the internal lamina cribrosa surface. This method has good reproducibility, suggesting future clinical applications.

Aged↗

PubMed1997

Early detection of visual field progression in glaucoma: a comparison of PROGRESSOR and STATPAC 2.

AIM: To compare the performance of PROGRESSOR (pointwise linear regression) and STATPAC 2 (comparison with baseline values) in detecting early deterioration in the visual fields of glaucoma patients. METHODS: Visual field series from 19 untreated normal tension glaucoma eyes which were deteriorating on clinical grounds were analysed by PROGRESSOR and STATPAC 2. Progression criteria for PROGRESSOR were (1) inner points: slope < -1 dB/year, p < 0.05 and (2) edge points: slope < -2 dB/year, p < 0.05. Criteria for STATPAC 2 were p < 0.05 change probability for any point on three consecutive fields. Detection time was defined as the time interval between the initial field and the first field in which at least one progressing point was identified. Detection times produced by the two techniques were compared. RESULTS: PROGRESSOR and STATPAC 2 agreed on progression in all 19 eyes. Mean detection time for PROGRESSOR was 1.077 (SD 0.985) years and for STATPAC 2 was 2.161 (1.357) years. PROGRESSOR detected progression sooner than STATPAC 2 in 18 eyes (p < 0.01), Wilcoxon matched pairs signed rank test). PROGRESSOR detected progression earlier by a mean of 1.085 (0.936) years. CONCLUSIONS: PROGRESSOR consistently detected progression earlier than STATPAC 2. The PROGRESSOR software is a useful tool for the early detection of visual field deterioration in glaucoma.

Algorithms↗

PubMed1997

Variation of nerve fibre layer thickness measurements with age and ethnicity by scanning laser polarimetry.

AIMS: Scanning laser polarimetry is a new technique allowing quantitative analysis of the retinal nerve fibre layer in vivo. This technique was employed to investigate the variation of the retinal nerve fibre layer thickness in a group of normal subjects of different ages and ethnic groups. METHODS: 150 normal volunteers of different ages and ethnic groups were recruited for this study. Three consecutive 15-degree polarimetric maps were acquired for each subjects. Nerve fibre layer thickness measurements were obtained at 1.5 disc diameters from the optic nerve. Four 90-degree quadrants were identified. RESULTS: The mean nerve fibre layer thickness varied from a minimum of 55.4 microns to a maximum of 105.3 microns, with a mean thickness value of 78.2 (SD 10.6) microns. Superior and inferior quadrants showed a comparatively thicker nerve fibre layer than nasal and temporal quadrants. Retinal nerve fibre layer thickness is inversely correlated with age (p < 0.001). White people showed thicker nerve fibre layers than Afro-Caribbeans (p = 0.002). CONCLUSION: The results indicate a progressive reduction of the nerve fibre layer thickness with increasing age. This may be due to a progressive loss of ganglion axons with age as suggested in postmortem studies. A racial difference in nerve fibre layer thickness is present between whites and Afro-Caribbeans.

Adolescent↗

PubMed1997

High spatial resolution automated perimetry in glaucoma.

BACKGROUND: Automated perimetry is of fundamental importance in assessing visual function in glaucoma. A technique was evaluated to perform high spatial resolution automated perimetry to allow a more detailed assessment of the luminance sensitivity in selected regions of the visual field than is possible with conventional perimetry. METHOD: High spatial resolution perimetry was performed using a Humphrey automated perimeter by measuring luminance sensitivity across a 9 by 9 degree custom grid of 100 test locations with a separation between adjacent locations of 1 degree. Quantitative analysis of the raw and Gaussian filtered thresholds was performed to assess the repeatability of the technique in normals, glaucoma suspects, and glaucoma patients. RESULTS: The testing protocol was well tolerated by all subjects. High spatial resolution perimetry in glaucomatous eyes demonstrated fine luminance sensitivity loss not suspected with conventional perimetry. High spatial resolution perimetry also demonstrated reproducible areas of sensitivity loss in some glaucomatous eyes in areas of the visual field which appear normal with conventional programmes. The repeatability of the technique correlated with mean threshold sensitivity and was substantially improved to clinically acceptable levels by Gaussian filtering the thresholds. CONCLUSION: This technique of high spatial resolution perimetry allows the practical assessment of selected regions of the visual field at higher resolution than conventional perimetry, and may be clinically useful in glaucoma.

Case-Control Studies↗

PubMed1997

[The test of motion perception in normal subjects].

OBJECTIVE: To study the properties of motion perception (MP) of normal Chinese subjects. METHOD: MPs were tested for 56 cases (112 eyes) of normal subjects, their ages ranging from 11 years to 68 years, by using vertical moving bars generated on VGA monitor in a PC compatible computer. RESULTS: MPs were affected by age when the bars moved horizontally for 2 pixels, the ratios of MP were increased with age growing from 10 year group to 30 year group, then the ratios of MP were gradually decreased from 40 year group. MPs were not affected by age under the horizontally moving conditions of 4 pixels and 6 pixels and > 40 Hz flicker movement. There were no relationships between either MP and sex or MP and eye side difference. CONCLUSIONS: The characteristics of MP are determined and the normal reference values are provided in normal Chinese subjects.

Adolescent↗

PubMed1997

Fundus autofluorescence in age-related macular disease imaged with a laser scanning ophthalmoscope.

PURPOSE: To image and quantify the spatial distribution of fundus autofluorescence in normal subjects, to determine its age dependence, and to document the deviation from normal in patients with age-related macular disease. METHODS: Using a confocal laser scanning ophthalmoscope (cLSO), the intensity and spatial distribution of fundus autofluorescence was studied in 33 normal subjects, 97 eyes with drusen only, and 111 eyes with visual loss caused by age-related macular disease. RESULTS: Fundus autofluorescence intensity in normal subjects was highest at the posterior pole and dipped at the fovea. Autofluorescence increased with age at the posterior pole. Fundus in eyes with age-related maculopathy showed localized high autofluorescence that did not correspond with drusen. Linear pigmentation at the level of the retinal pigment epithelium (RPE), whether detached or flat, fluoresced brightly, whereas plaques of melanin did not. Areas of low and high levels of autofluorescence were seen in lesions containing choroidal new vessels. In areas of geographic atrophy, autofluorescence was low. CONCLUSIONS: The spatial distribution of background fundus autofluorescence and the correlation of autofluorescence with age in normal subjects imply that autofluorescence is derived from lipofuscin at the level of the RPE. Focal accumulation of autofluorescent material occurs at the level of the RPE in patients with drusen, but the drusen do not show marked increases in autofluorescence. It is likely that melanolipofuscin accounts for the high levels of autofluorescence, corresponding to linear pigmentation at the level of the RPE. Low-intensity autofluorescence occurs in the presence of retinal photoreceptor loss, and variable levels over disciform lesions probably relate to variations in metabolic activity of the RPE.

Adolescent↗

PubMed1996

Visual field progression: comparison of Humphrey Statpac2 and pointwise linear regression analysis.

BACKGROUND: Humphrey Statpac2 "glaucoma change probability analysis' is a widely available analysis technique to aid the clinician in the diagnosis of glaucomatous visual field deterioration. A comparison of this technique with the more recently described pointwise linear regression analysis (PROGRESSOR) is given. METHODS: Series of visual field data from a group of nine eyes of nine patients with normal-tension glaucoma were selected. Each series had 16 fields with mean follow-up of 5.7 years (SD 0.6 years). Statpac2 "glaucoma change probability analysis' was used to define test locations that had unequivocally deteriorated in the last three fields of each series. The accuracy of both Statpac2 and PROGRESSOR in providing early detection of these deteriorated locations was assessed. RESULTS: The sensitivity and specificity of the two techniques in predicting deteriorated locations were similar when a rate of luminance sensitivity loss of faster than 1 dB/year (2 dB/year for outer locations beyond 15 deg of eccentricity) with a slope significance of P < 0.10 was used as the regression definition of deterioration. The difficulties of comparing two techniques in the early diagnosis of field progression without a true external standard for field loss are illustrated. CONCLUSIONS: PROGRESSOR closely emulates the performance of Statpac2 in detecting sensitivity deterioration at individual test locations. This new technique, which uses all available data in a field series and gives the rate of sensitivity loss at each location, may provide a clinically useful method for detecting field progression in glaucoma.

Disease Progression↗

PubMed1996

Analysis of visual field progression in glaucoma.

BACKGROUND: Despite the widespread use of computerised perimetry the diagnosis of visual field deterioration in following glaucoma patients over time remains particularly difficult. A new method of analysis using a novel graphical display of longitudinal field data is presented. METHODS: A linear regression model of the luminance sensitivity at each stimulus location against time of follow up transforms the quantitative data from a series of fields into a colour coded form which illustrates the spatial configuration of change to aid the interpretation of field loss. The method of analysis and the developed computer software (PROGRESSOR) is described. Comparison with STATPAC-2 glaucoma change probability analysis is given including levels of agreement between the techniques using series of fields of 10 eyes from patients with normal tension glaucoma. RESULTS: Examples of this new method compare well with STATPAC-2 analysis. The level of agreement between the techniques to separate progressing from stable retinal locations is good (kappa = 0.62; SE = 0.04). CONCLUSIONS: This new technique, which combines the change in perimetric sensitivity over time with colour coding of significant change into one image may provide an efficient method to detect true progression in glaucomatous field loss.

Diagnosis, Computer-Assisted↗

PubMed1996

A computer model for predicting image quality after photorefractive keratectomy.

BACKGROUND: Accurately predicting visual performance remains a concern in refractive surgery. The effects of the eye's optics on retinal image quality were investigated using computer ray tracing to model the human eye after photorefractive keratectomy (PRK). METHODS: Ray-tracing analysis was used with an anatomically realistic model of the human eye including aspheric surfaces and crystalline lens gradient index distributions. The contribution of corneal curvature to refractive error was investigated using data of axial length, corneal power, anterior chamber depth, and lens power from 318 eyes from the literature. The computer interface was specifically designed for use with PRK and provides graphical plots of the remodeled eye, ray paths and retinal image formation. RESULTS: Modeling the optical contribution of corneal curvature resulted in an improvement in predicted refractive state of the eye as a function of axial length expressed as the R2 value of the regression analysis from 0.88 to 0.96. Subsequently, analyses were conducted for single and multizone treatment areas of differing diameter and with varying pupil size. Retinal image quality following PRK for the human cornea was found to be affected by not only the corneal parameters of anterior curvature and thickness, but also by axial length, pupil size, and anterior chamber depth. CONCLUSIONS: The inclusion of multiple interdependent optical parameters showed differences from conventional methods in predicting refractive outcome following PRK and revealed factors affecting image quality may account for some imperfections in visual performance based on simpler optical modeling.

Anterior Chamber↗

PubMed1996

A new computer assisted objective method for quantifying vascular changes of the bulbar conjunctivae.

A novel computer software method was used to quantify the conjunctival plexus on the scleral background for measurement of the vascular surface area from photographs. A previously described method was used (Palmer, J. R., Owen, C. G., Ford, A. M., Jacobson, R. E. and Woodward, E. G. (1996). Optimal photographic imaging of the bulbar conjunctival vasculature. Ophthal. Physiol. Opt. 16, 144-149) to optimise photographic imaging of the bulbar conjuctival vasculature by increasing the information content in the image. Repeatability of this technique was evaluated. Twenty subjects (20 eyes) free from ophthalmological and systemic abnormality were examined on two separate occasions. The maximum 95% confidence limits for repeatability are +8.58/-3.95%. For 10 consecutive estimates of vascularity the maximum 95% confidence interval lie between +/- 6.54%. To evaluate the technique the lateral-bulbar conjunctivaein 10 soft (SCL) and 10 rigid gas permeable contact lens (RGPCL) wearers during the first 10 months of contact lens wear, were assessed and compared with subjective grading of hyperaemia. The new method showed sufficient sensitivity in detecting increased hyperaemia in the RGPCL wearing group and demonstrated statistically significant change. Subjective graded assessment of vascularity (using established classifications) detected increased hyperaemia, however, this was not statistically significant. Conjunctival vasculature is a dynamic structure and a source of valuable quantitative information where the ocular environment is varied, or where the ocular surface is affected by disease. Hence it is worthy of further investigation. A simple inexpensive method of computer assisted determination of vascularity is described.

Adult↗

PubMed1995

Chromosome 19q cone-rod retinal dystrophy. Ocular phenotype.

OBJECTIVE: To describe the phenotype in a family with dominantly inherited cone-rod dystrophy with chromosome assignment to a 19q locus, and to correlate this with current classifications of this retinal dystrophy. DESIGN: A detailed clinical examination including Goldmann perimetry was undertaken in all family members. Six members under the age of 30 years underwent dark-adapted electroretinography, color contrast-sensitivity measurement, dark-adapted static perimetry, and dark adaptometry. PATIENTS: The study included 34 affected and 22 unaffected patients in four generations of a pedigree that manifested autosomal dominant cone-rod retinal dystrophy linked to a chromosome 19q locus by genetic linkage analysis. RESULTS: Loss of visual acuity occurred in the first decade of life, onset of night blindness occurred after 20 years of age, and little visual function remained after the age of 50 years. Central and, later, peripheral retinal fundus changes were associated with central scotoma, pseudoaltitudinal field defects, and finally global loss of function. Psychophysical and electrophysiologic testing before the age of 26 years showed more marked loss of cone than rod function. CONCLUSIONS: The phenotype associated with this mutation does not fit well into previous subtypes of cone-rod dystrophy. Further studies will be needed to correlate specific genetic mutations in this group of conditions with the various clinical phenotypes.

Adolescent↗

PubMed1995

Autosomal dominant pattern dystrophy of the retina associated with a 4-base pair insertion at codon 140 in the peripherin/RDS gene.

OBJECTIVE: To define the phenotype of a retinal dystrophy associated with a 4-base pair insertion at codon 140 of the peripherin/RDS gene. PATIENTS: Six affected members spanning two generations of a single family were examined. Five were studied in detail electrophysiologically and psychophysically. METHODS: Psychophysical testing included color vision testing, photopic and scotopic static threshold perimetry, and dark adaptometry. Electrophysiological testing included flash and pattern electroretinography, as well as electrooculography. RESULTS: Clinical findings ranged from subtle pigmentary changes at the level of the retinal pigment epithelium to more widespread pigmentary changes associated with choroidal neovascularization. Those with severe fundus changes exhibited greater abnormalities in psychophysical and electrophysiological testing than those with minimal fundus changes. CONCLUSIONS: This particular peripherin/RDS gene mutation is associated with dominantly inherited pattern dystrophy of the retina. The phenotypic expression is variable in a manner not explained by age.

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