Biomedical subjects
Publications and source records attributed to M Marré.
Pathologic scotopization, an important symptom of retinal disease, can be studied by means of the Nagel II anomaloscope. This method is called the micro-screw method. The micro-screw method was performed in 14 congenital and 13 acquired colour vision defective individuals. The method proves to be useful in detecting symptoms of rod intrusion in colour vision under photopic conditions.
Examination of a great number of patients resulted in the depth localisation theory. The combination of this theory with the fixation-eccentrisation theory is clinically useful: acquired colour vision defects can be subdivided by the fixation mode and by signs of receptor damage. There are indications that in multiple sclerosis the slowly progressive cases present with more receptor damage than the acute cases.
With a routine clinical colour vision test battery we found scotopization in 32% of retinal diseases presenting with pseudoprotanomaly as sign of an acquired type III blue-yellow colour vision defect. In blue-yellow colour vision defects of retinal origin scotopization is a transient phenomenon, present in early stages of the disease, but it is not an obligatory finding. There is no evident relationship between visual acuity and scotopization.
The Nagel anomaloscope can be incorporated in the diagnosis of eye diseases. Three parameters are relevant: 1. The measure of the absolute matching range (scale units) 2. The preferred direction of the widened matching range (to red or to green) 3. The luminance matches with the yellow (decreasing matches indicating a pathologic scotopisation). - Six pathologic anomaloscope findings can be differentiated: 1. Pseudoprotanomaly (retinal diseases; type III acquired blue-yellow defects) 2. Symmetrically widened absolute matching range (reduced hue discrimination without reference to its etiopathology) 3. Absolute matching range asymmetrically widened to red with scotopisation (retinal diseases; type III acquired blue-yellow defects or type I acquired red-green defects) or without scotopisation (retinal diseases or optic nerve diseases; type III acquired blue-yellow defects) 4. Absolute matching range asymmetrically widened to green (mostly optic nerve diseases; type II acquired red-green defects) 5. Acceptance of both end matches ("0" up to "73") with scotopisation (retinal diseases) or without scotopisation (optic nerve diseases) 6. Achromatic matches (selective cone diseases, such as Stargardt's dystrophy or progressive cone dystrophy). Indications for anomaloscope examinations and clinical application of the method are discussed in ten cases. The utility of the Rayleigh-equation consists in diagnosing pathologic scotopisation (differential diagnosis between retinal diseases and optic nerve diseases) and in making a quantitative evaluation of the acquired color vision defect (follow-up examination).
In three series of examinations, 3375 male preschool-age children and 93 adult normal trichromates were tested using the Velhagen Pflügerhaken charts. The authors recommend modifying the evaluation of the results slightly by introducing a "doubteful" category for children who make one mistake or who show hesitation and lack of assurance in interpreting the charts. Using this modified form of assessment, diagnoses of "probably achromatopic" and "doubtful" were made in 7.16% and 2.13% respectively of 1689 preschool-age boys. The failure rate during the test and the duration of the examination were age-dependent, and declined with increasing age from 4.15% to 0.45% and from 1.18 min to 0.59 min, respectively. Most mistakes were made with charts nos. 9, 3, and 5. The results of tests with Pflügerhaken charts are fully comparable with those of other internationally used tests for adults. They can be recommended for screening preschool-age children.
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Color vision examinations were performed using a clinical test battery and two spectral laboratory methods. With aphakia and iris-clip lenses (ICL) there were slight acquired blue-yellow defects six months to three years after surgery, especially when the more sensitive laboratory methods were used. They were possibly caused by photochemical damage to the retina or by a barrier deprivation syndrome. Color vision with posterior chamber lenses (PCL) was superior to that with ICL, and in aphakic subjects it was quite normal. In the clinical tests no differences could be found between PCLs of clear PMMA material and those with UV absorbing properties. Slight acquired blue-yellow defects in the immediate postoperative phase after implantation of PCLs can be attributed to postoperative irritation and are reversible. Lasting and severe blue-yellow defects indicate inflammation or macular edema.
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Acquired colour vision defects are directly related to the fixation mode: blue-yellow defects in foveolar fixation, blue-yellow or red-green defects in eccentric fixation. The primary localization of a disease can be retraced from the degree of cone damage. Optic nerve diseases essentially lack signs of cone damage. Processes at the level of the choriocapillaris/retinal pigment epithelium induce a non-selective receptor impairment. There are minor signs of cone damage. In cone dystrophies there is selective cone damage. Scotopization indicates a relatively well-preserved rod function.
Colour vision in squint amblyopia depends on the fixation modus. In eyes with foveolar or unsteady foveolar from fixation the 3 primary colour vision mechanisms (CVMs) gave normal foveolar CVM patterns. The absolute spectral retinal sensitivity was somewhat, but not significantly lowered. The spectral sensitivity for hue discrimination was either normal, or slightly reduced in the short wavelength side, or slightly reduced over the whole visible spectrum. The spectral sensitivity for saturation discrimination showed normal curves. -- In amblyopic eyes with parafoveal to perifoveal fixation mode the absolute spectral retinal sensitivity is lowered for about 0.45--0.60 log units in comparison to an approximately corresponding excentric retinal area in a normal eye. In eyes with parafoveolar to perifoveal fixation mode measurements of CVMs and of hue discrimination gave better results than could be expected with regard to the position of the fixating area as determined by visuscope. The values correspond to those obtained in retinal areas at least as close to the foveola as the amblyopic fixation point, but usually of an even more central position. The sensitivity for saturation discrimination showed no significant disturbance.
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