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A report on three patients with illustrations of their visual anomalies following light coagulation for their CSR disease is presented. The correspondence of the phenomena illustrated with the ophthalmoscopically visible fundus changes prove their objective origin.
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The cellular source of the blue field entoptic phenomenon was investigated in two microvascular preparations using video-microscopy with lighting conditions similar to those under which the entoptic phenomenon is visualized within the human eye. In the wing of the hibernating bat, microvascular flow was simultaneously videotaped under transmission illumination at 430 nm and under unfiltered illumination. In the rat cremaster alternating observations were made using transmission illumination at 430 nm and epi-illumination fluorescence microscopy with leukocytes rendered fluorescent by intravenous Quinacrine. In both preparations, low magnification video-microscopy using 430 nm illumination produced a field of particles, which were brighter than the background, flowing within a network of dark vessels. The appearance of the particles and their movement simulated the blue field entoptic particle motion. Under higher magnification, the particles appeared brighter than the plasma gaps between red blood cells and were demonstrated to be leukocytes by morphology, by specific staining and by typical behavioral movement. The particles were observed in terminal arteriols capillaries, and post-capillary venules where they were not obscured by red blood cells. The results of this study of two microvascular preparations strongly suggest that in the human eye the blue field entoptic phenomenon is produced by leukocytes flowing within the macular retinal microvasculature.
The blue field entoptic phenomenon (BFE), which allows the observation of one's own leukocytes flowing in macular retinal capillaries, was used to predict postoperative macular function in 136 consecutive patients undergoing uncomplicated cataract operation. The results were compared to those obtained with three commonly used tests: two-light discrimination, color perception, and the Purkinje vascular entoptic phenomenon. All four tests identified a nearly equal number of the good maculae (visual acuity 20/40 of better) ranging from 87% for the two-light discrimination test to 94% for the BFE test. However, the tests varied greatly in predicting poor macular function (visual acuity 20/50 or worse). The BFE test identified more than 75% of the poor maculae; the Purkinje vascular entoptic test and the two-light discrimination test, only 22%; and the color perception test, 11%. A positive response to the BFE test indicated a .98 probability of good macular function; a negative response indicated a .82 probability of poor macular function, predictions that were better than the other three tests or their combination.
The entoptic phenomenon of the flying corpuscles (FLC) consists of the perception of one's own leukocytes flowing in the perifoveal capillaries. A method has been developed to investigate the type of motion of the FLC, their relative number and speed, and their distribution over the central visual field. The results in 38 patients with disease affecting the macula correlated well with the clinical findings obtained by ophthalmoscopy, visual field tests, and fluorescein angiography. The test is noninvasive, inexpensive, easy to perform, and provides information on the perifoveal retinal circulation and on macular function.
With splitting of macula by perimetry, the entopic phenomena (the perception of one's own foveal xanthophilic pigment and macular vessel leukocytes) were utilized to study the character of macular sparing or splitting in patients with pregeniculate or postgeniculate hemianopsia. In the pregeniculate group, 11 of 14 eyes perceived the Haidinger brushes figure as a half circle corresponding to the perimetric macular splitting, whereas flying corpuscles were not perceived at all or were less numerous on the hemianoptic side than on the normal field side. In contrast, six of seven patients with postgeniculate lesions perceived the Haidinger brushes figure as a complete circle, four of six perceived fewer flying corpuscles on the hemianoptic side than on the normal field side, and two patients reported perceiving an equal number in all quadrants. This study indicated that in pregeniculate hemianopsia there is usually a true splitting of the macula, whereas in postgeniculate hemianopsia, there is some macular sparing even when perimetry shows macular splitting.
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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.
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.
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.
Entoptic visualisation of cataract is a simple technique to use. Retro-illumination photography demonstrates that it can also be accurate. The optics of the methods used are discussed.
A measurement system for macular blood flow using the blue field entoptoscope and a microcomputer was devised by Riva & Petrig in 1980. However, there have been difficulties in applying their system to some clinical cases, especially when subjects are aged and their responses are not reliable. A modified method suitable even for such cases is presented.
Autoregulation of the macular capillary blood flow was investigated using a blue-field entoptoscope and OCVM suction cup system. The perfusion pressure was reduced by elevation of the intraocular pressure with a Langham's suction cup placed on the temporal sclera. The results showed that the autoregulatory response maintains the macular capillary blood flow velocity until the perfusion pressure is reduced to approximately 25 mmHg. The Closed-loop gain of the autoregulatory response functions at a perfusion pressure as low as approximately 10 mmHg, below which it did not work well.
The authors attempted to predict postoperative visual acuity in patients undergoing cataract extraction by comparing the results obtained using two subjective methods: Lotmar's visometer test and the blue-field entoptic (BFE) test. Both tests allow assessment of retinal visual acuity in the presence of opacities of the ocular media. Measurements were made on 60 patients before cataract extraction. These subjects were followed for three months in order to assess their postoperative visual acuity and to ascertain the reliability of the tests. Analysis of the data demonstrates the high level of reliability of both methods. Lotmar's visometer test gives a more exact assessment of macular function. However, in the presence of total lens opacity, the BFE test becomes necessary since Lotmar's test loses reliability in such cases.
The blue light entopic phenomenon was used to measure retinal blood flow in 87 diabetics and 10 normal controls in a longitudinal study. The time interval between the initial and final studies was 21-39 months (mean 31.4). The retinal blood flow velocity did not change in the 10 subjects in the control group nor in those nine patients with no retinopathy, all but one of whom remained free of retinal lesions. In the 24 with background retinopathy the flow velocity fell significantly from 0.71 (SD 0.35) mm/s to 0.48 (0.13) mm/s (p less than 0.01). The velocity also decreased in the preproliferative group of 16 patients from 0.62 (0.39) mm/s to 0.41 (0.14) mm/s (p less than 0.05). The retinopathy status changed in 11 of this group. In those with proliferative retinopathy (now treated) and those treated previously there was no change in flow velocity.