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PubMed1996

Visual phenomena, disturbances, and hallucinations.

The visual system and its processing of sensory information can be affected in a variety of ways that may be either normal or associated with numerous disorders and diseases. Visual images produced by the intrinsic components of the eyes are often normal and are known as entoptic phenomena. In contrast, the visual system may be disrupted by various disorders and pathologic processes, which can result in metamorphopsia, transient loss of vision, and positive scotomas. Such disruptions can be secondary to retinal and optic nerve disease, migraines associated with visual auras, and cerebrovascular and neurologic diseases; they can also be side effects of certain drugs. In addition, the visual system may process incoming sensory information in such a way that what is seen is perceived incorrectly, i.e. illusion; or the visual system may produce images of things not really there, i.e. hallucination. Various types of visual phenomena, disturbances, and hallucinations are discussed. The numerous visual presentations need to be differentiated so that appropriate treatment, management, and patient education can be rendered.

Diagnosis, Differential↗
PubMed1991

[Entoptic detection of choriocapillaris].

Entopic perception of the central choriocapillaris is documented by personal experience. Seen in this manner, the choriocapillaris appears due to circulatory conditions as a wavy convolute of fresh capillaries whose paths are paralleled by numerous, irregularly distributed, round, black structures. The latter have been presumed to be corpuscles, i.e. erythrocytes, and can be seen entopically as single rows of radial capillaries. Histological studies have shown, however, that these rows of erythrocytes are not always isolated; they have also been found in the choriocapillaris in clusters of rows. Moreover, analogously to the lack of entopic perception of erythrocytes in the retinal vessels in Purkinje's images, the erythrocytes of the choriocapillaris may likewise not be perceived for physical and optical reasons. Therefore the round, black formations are not entoptically perceivable erythrocytes of the choriocapillaries but can only originate in the circular network of the central choriocapillaris. Light directed experimentally into the eye and focussed on the choriocapillaris through a narrow slit positioned nasally leads via reflection to stimulation of the retina from outside to inside and so to entoptic perception of the choriocapillary network. Closer analysis of entoptic perception of the choriocapillaris is significant in view of its heuristic value.

Adult↗
PubMed1990

Visually evoked potentials in response to rotating plane-polarized blue light.

Visually evoked cortical potentials closely related to the appearance and disappearance of Haidinger's brushes were obtained in response to onset and offset of rotation of plane-polarized blue light. The method provides a means of investigating macular function in man; it is fairly independent of ocular opacities and relates, for the first time, entoptic phenomena to those evoked by extrinsic light stimulation.

Adult↗
PubMed2004

An aura of confusion: 'seeing auras-vital energy or human physiology?' Part 1 of a three part series.

The first of three papers that considers claims made for the perception or detection of vital energy. Many systems of Complementary and Alternative Medicine (CAM) assume the existence of a vital force that mediates therapeutic efficacy, for example chi or qi in Traditional Chinese medicine. Vital energy directly perceived or imaged that surrounds living organisms is frequently termed the aura. This paper aims to show how phenomena that arise as a consequence of the normal functioning of the human visual system can be inappropriately offered as support of claims for the direct perception of vital energy or the aura. Specifically, contrast and complementary colour phenomena, entoptic phenomena and the deformation phosphene, the 'flying corpuscle effect', the blind spot and the 'reverse telescope effect' are explained and discussed.

Color↗
PubMed1994

[Sensory and electrical responses in stimulation of the macula with short-wave (407-527 nm) linear polarized light (Haidinger polarization brushes)].

We investigated Haidinger's (1844) entoptic polarization brushes of the macula psychophysically and electrophysiologically during rotation of plane-polarized blue (< 520 nm) light projected to a polarization screen. Psychophysically the sensitivity of the brushes was highest between 470 and 490 nm, with a steep decrease at longer wavelengths. Increase of adaptive illumination (I) above 0.1 cd/m2 increased the increment threshold (delta I) of the brushes between 407 and 515 nm about equally (delta I/I = 0.9). Comparison of the action spectrum of different photoreceptors with the spectral sensitivity of Haidinger's brushes suggested synergistic contributions of blue, green and red photoreceptors. A decrease in visual acuity to 0.01 by plus lenses did not affect the light threshold of the brushes significantly, while blurring by Bangerter foils increased the threshold markedly (about eightfold at visual acuity of 0.01). Thus, the determination of threshold of Haidinger's brushes provides the means of investigating certain macular functions behind, and widely independent of, opacities of the ocular media. While no retinal potentials (ERG) were seen during rotation of the polarizer, we obtained cortical potentials (VEP) closely related to the appearance of Haidinger's brushes in response to rotation onset of blue polarized light. The potential derived from Oz+Ol+Or consisted of a phasic negative response after a peak latency of 295 +/- 34 ms (N 295). Similar responses were also obtained to medium and long wavelengths (extrinsic windmill rotation during foveal fixation at stimulus conditions closely related to Haidinger's brushes: 3 degrees field, 2 cy/rev, 2 cd/m2, contrast 0.15). Thus VEP recording permits the comparison of entoptic and extrinsic excitation of the macula.

Adult↗
PubMed1978

Cocaine hallucinations.

The author reviews the literature on hallucinations that occur as a result of acute and chronic administration of cocaine. He examined the phenomenology of cocaine hallucinations in a group of 85 recreational cocaine users, 15 of whom reported hallucinatory experiences in visual, tactile, olfactory, auditory, and gustatory modalities. He discusses a new phenomenon of "snow lights" in terms of initiating a progression of symptoms leading to the classic "cocaine bugs." He also points out the similarity of cocaine hallucinations to entoptic phenomena and migraine hallucinations, which suggests a common mechanism of action based on CNS excitation and arousal.

Adult↗
PubMed1996

[Incidence of intra-individual lateral differences in interference fringe acuity and entoptic functions and their prognostic value with reference to lateral differences in optotypic acuity].

No adequate research results are available on the frequency and medical significance of intraindividual side differences in the entoptic functions and interference fringe acuity. We have collected data on these topics from examinations of 312 people with no eye defects; the subjects in this group were aged between 6 and 85 years and were divided into ten age-groups of approximately the same size. We were trying to find out to what extent a real side difference in the distant or near visual acuity can be deduced from an intraindividual side difference in the entoptic function test and/or laser interferometry as in healthy people. To allow grading of macular chagrin patches for the first time we defined the "microsymptoms of macular chagrin" patches. Moreover, we described the changes in interference fringe acuity and in entoptic function with advancing age. By using already established research approaches, we have evaluated the following parameters of examination: distant visual acuity with optotypes, near visual acuity (Nieden), entoptic functions (vessel figure of Purkinje and macular chagrin patches), laser interferometry (Retinometer) and ophthalmological findings. We found that of macular chagrin varied in appearance with the age of the patient. Patients with no eye defects seldom have an intraindividual side difference in the distant or near visual acuity, and any present is only marginal. This is why there seems to be too narrow a correlation with the results of the laser interferometry and of the entoptic function test. The negative predictive value is between 89% and 95%. This means that patients who have no side difference in interference fringe acuity or in the entoptic function test also have no intraindividual side difference in distant visual acuity with optotypes or near visual acuity (Nieden). This is the medical significance of our results in respect to more marked side differences such as are found in patients with eye defects. The predictive significance of the entoptic function test is enhanced by knowledge of microsymptoms of macular chagrin patches.

Accommodation, Ocular↗
PubMed1981

Blue field entoptic test in patients with ocular trauma.

The blue field entoptic test was applied to study macular function in 32 patients with severe ocular trauma and markedly reduced visual acuity (6/60 [20/200] or less) in whom fundus details could not be seen initially. This test is based on the entoptic phenomenon, whereby one can observe one's own leukocytes flowing in the perifoveal retinal capillaries. Twenty of the 21 patients (95%) with normal perception of the corpuscles regained a visual acuity of 6/12 (20/40) or better on follow-up, whereas ten of the 11 patients (91%) with abnormal test responses had, on follow-up, a visual acuity of counting fingers or less. The blue field entoptic test is therefore useful in prognosticating macular function in patients with reduced visual acuity due to media opacities secondary to ocular trauma.

Adolescent↗
PubMed2004

Scanning laser entoptic perimetry for the detection of age-related macular degeneration.

OBJECTIVE: To determine the sensitivity and specificity of scanning laser entoptic perimetry for detecting visual function damage due to age-related macular degeneration (ARMD). METHODS: We measured the presence or absence of visual field disturbances by entoptic perimetry and determined the severity of ARMD based on masked readings of fundus photographs. A prospective masked study comparing the findings of entoptic perimetry with fundus photographs was performed. We recruited 91 patients with ARMD and 24 patients without ARMD during ophthalmologic visits. An appropriate institutional review board approval was obtained for the project. The main outcome measure was the detection of visual scotomata. RESULTS: Scanning laser entoptic perimetry had an overall sensitivity of 82% and a specificity of 100% for the detection of ARMD. The sensitivity for early stages of the disease is greater than 70%, and increases to above 90% for moderate to late stages. CONCLUSION: Scanning laser entoptic perimetry is a specific and sensitive test for detecting ARMD, even at the earliest stages when patients are typically asymptomatic.

Aged↗