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Biomedical subjects

R Lakowski

Publications and source records attributed to R Lakowski.

At least 19 recordsLinked to original sources
PubMed1998

Applications of neural networks to colour recognition.

Colour specification and matching are important tasks used in a number of different industries. However, current methods can employ very complicated, elaborate pieces of laboratory equipment which are not portable, such as spectrophotometers with combinations of calibrated light sources and a large number of narrow band filters. Simpler, portable devices are typically not sophisticated enough to give a high degree of quality control due to the less sophisticated light sources and the necessarily smaller number of filters employed. Lastly, techniques such as the 'match by eye' method can lead to deceptive metameric matches. This paper outlines the beginning of the development of a colour measurement system which is portable, easy to use, and more accurate than other portable devices by virtue of an artificial neural network used to analyze the data. With specialized training of the neural network, it could even be used in applications such as teeth and skin colour measurements.

Color↗
PubMed1989

A comparison of the blue color mechanism in high- and low-tension glaucoma.

Twenty-five eyes of 25 high-tension glaucoma patients and 25 eyes of 25 low-tension glaucoma patients matched for similar visual field defects had their spectral increment threshold measured. Patients with high-tension glaucoma showed significant losses in both chromatic and achromatic sensitivities when compared with low-tension glaucoma patients. The results support the hypothesis that there may be different mechanisms of damage in glaucoma.

Aged↗
PubMed1988

Correlation between color vision and highest intraocular pressure in glaucoma patients.

We examined 75 glaucoma patients to determine the relationship between losses in color vision and their highest intraocular pressure. The losses of blue chromatic (P less than .0001) and achromatic (P = .0006) sensitivity were strongly related to highest intraocular pressure. The dysfunction of blue chromatic and achromatic pathways may therefore indicate damage from increased intraocular pressure.

Color Perception↗
PubMed1986

Color vision and retinal nerve fiber layer in early glaucoma.

We tested 47 eyes in 47 patients (ten normal subjects, 15 with suspected glaucoma, and 22 with glaucoma) with the Pickford-Nicholson anomaloscope to assess the retinal nerve fiber layer and measure color vision. The 47 subjects were randomly selected from a group of 132 for whom Farnsworth-Munsell 100-hue color error scores were known. The yellow-blue and green-blue anomaloscopic matching ranges correlated significantly with diffuse retinal nerve fiber loss. There was no correlation with localized retinal nerve fiber loss.

Adult↗
PubMed1981

Acquired color vision changes in glaucoma. Use of 100-hue test and Pickford anomaloscope as predictors of glaucomatous field change.

A five-year follow-up of eyes with elevated intraocular pressures, but without field defects, in which the color vision had been assessed by the 100-Hue test and an anomaloscope was carried out. Field defects developed in eight of 42 eyes with a low 100-Hue score, whereas field defects developed in ten of 13 eyes with a high abnormality in the 100-Hue test score. In the case of the anomaloscope (Pickford Nicholson) scores, field defects developed in four of five eyes with poor yellow-blue scores, whereas similar field defects developed in only nine of 40 years with a normal yellow-blue scores. With regard to blue-green scores, field defects developed in six of 11 eyes with a poor blue-green score, whereas field defects developed in only seven of 40 eyes with a normal blue-green score. These differences are statistically significant, and the probabilities of an abnormal color vision the results in subsequent field defects have been worked out. The red-green scores were not predictive.

Color Perception Tests↗
PubMed1977

The effect of oral contraceptives on colour vision in diabetic women.

The results of previous studies of the effect of oral contraceptives on visual function have produced discrepancies and have lacked specific restraints on the control and experimental groups. We compared 14 diabetics with normal acuity who were taking oral contraceptives with equivalent diabetic and control groups and used the Pickford-Nicholson anomaloscope and the Farnsworth-Munsell 100-Hue test. Diabetics using oral contraceptives showed a definite trend to increases in tritanomaly and extended red-green matching ranges. When these losses were classified by degree of defect a significantly higher incidence of major defects was found among diabetics on "the pill". Partial correlations for colour variables, duration of diabetes and duration of contraceptive therapy revealed a compounding effect. While subjects using oral contraceptives demonstrated trends toward the extreme scores, these effects were found only in one out of every four users.

Adolescent↗
PubMed1977

A Goldmann perimeter with high luminance chromatic targets.

We have modified the original Goldmann perimeter by replacing the source and shutter by a Xenon arc source with maximum target luminance of 3183 cdm-2, and a quartz iodine lamp yielding maximum background luminance of 150 cdm-2, both measured at the bowl. Colorimetric and spectrophotometric specifications of the new colour targets are comparable to the original, but give luminance intensities equivalent to 318 cdm-2: levels only realized for the white target in the original system. Chromatic profiles are comparable to previous profiles for achromatic targets and the close correspondence between the retinal threshold gradients produced by the two methods simplifies comparison of data obtained with out instrument with those obtained from routine static perimetry. Under high luminance conditions we do not find the relative foveal scotoma for blue targets observed by other researchers. The use of photometrically equated targets well withi; the photopic levels is an improvement on present methods of colour perimetry.

Color↗
PubMed1976

A study of dark adaptation in ocular hypertensives.

Previous studies of dark adaptation in glaucoma have been hampered by lack of standardization and poor definition of clinical categories. A new method of testing has been used on ocular hypertensives. A modified Goldmann/Weekers adaptometer and an 11 degree centrally fixated test patch were used to obtain two dark adaptation threshold curves for each subject -- one for blue-green and one for yellow. Results indicate that ocular hypertensives with no field loss and normal fundi have impaired normal subjects. The differences in the thresholds for blue-green were especially noticeable with the blue-green showing the greater difference. The 2.8 minute difference in mean curve cross-over time between normal and ocular hypertensive was also found to be significant. It appears that ocular hypertensives have impaired rod and cone functions, as well as deficient rod-cone interaction.

Animals↗
PubMed1976

Object analysis of the Stilling tables.

The CIE space that is occupied by the Stilling tables was found to be similar to that occupied by the Ishihara plates [LAKOWSKI, 1965] with the notable exceptions of a single table that extends into the blue area and two others that extend further into the green (fig. 4). Spectrophotometric curves show that the inks used are similar to those in other PIC plates, i.e. they have reflectance curves with broad-band characteristics. All tables are of the vanishing type and there is an attempt to differentiate between protan and deutan defects. Colorimetrically, tables I, II, VII and VIII have figure and background colours aligned mainly along the deutan isochromatic lines and only table III is a clear protan plate. Tables V, VI, IX, X and XI are ambiguous in design, i.e. they would be confused by most colour-deficient persons. Of the tables designed to detect blue-yellow deficiencies (tables V, VI, XI and XII), only the colours in table XII are aligned along tetartan confusion lines, while the other three tables are indefinite in their design. Thus the usefulness of these plates for detecting acquired dyschromatopsias is limited.

Color Perception Tests↗