Kazuo Mukuno

Presynaptic Effects of Botulinum Toxin Type A on the Neuronally Evoked Response of Albino and Pigmented Rabbit Iris Sphincter and Dilator Muscles

PURPOSEnTo investigate the effects of botulinum toxin type A(botulinum A toxin) on the autonomic and other non-adrenergic, non-cholinergic nerve terminals.nnnMETHODSnThe effects of neurotoxin on twitch contractions evoked by electrical field stimulation (EFS) were studied in isolated rabbit iris sphincter and dilator muscles using isometric tension recording.nnnRESULTSnBotulinum A toxin(150 nM) inhibited the fast cholinergic and slow substance P-ergic component of contraction evoked by EFS in the rabbit iris sphincter muscle without affecting the response to carbachol and substance P. Botulinum A toxin(150 nM) did not affect the twitch contraction evoked by EFS in the rabbit iris dilator muscle.nnnCONCLUSIONnThese data indicated that botulinum A toxin may inhibit not only the acetylcholine release in the cholinergic nerve terminals, but also substance P release from the trigeminal nerve terminals of the rabbit iris sphincter muscle. However, neurotoxin has little effect on the adrenergic nerve terminals of the rabbit iris dilator muscle.

Ocular dominance and patient satisfaction after monovision induced by intraocular lens implantation.

Purpose: To elucidate the relationship between ocular dominance and patient satisfaction with monovision induced by intraocular lens implantation. Setting: Eye Clinic, Kitasato University School of Medicine Hospital, Sagamihara, Kanagawa, Japan. Methods: The durations of exclusive visibility of dominant‐ and nondominant‐eye targets were measured in 16 patients with successful monovision and 4 patients with unsuccessful monovision to determine the characteristics of ocular dominance. The dominant eye was determined using the hole‐in‐card test (sighting dominance). The contrast of target in nondominant eye was fixed at 100%; the contrast of target in the dominant eye varied (ie, 100% to 80% to 60% to 40% to 20%) using rectangular gratings of 2 cycles per degree that were 4 degrees in size. Results: In the successful monovision group, the reversal thresholds (ie, exclusive visibility of the nondominant eye crosses over that of the dominant eye) were displayed only at low decreasing contrast (80% and 60%). However, in the unsuccessful monovision group, the reversal thresholds were at high decreasing contrast (20%) or not at all. The reversal thresholds in patients with unsuccessful monovision were at a significantly lower contrast than in patients with successful monovision (P<.05). Conclusions: Success and patient satisfaction in monovision patients were significantly influenced by the magnitude of ocular dominance. The balance technique seems to be a good method to evaluate the quantity of ocular dominance and prospectively evaluate the monovision technique.

Effects of dominant and nondominant eyes in binocular rivalry.

Purpose. To investigate the relation between sighting and sensory eye dominance and attempt to quantitatively examine eye dominance using a balance technique based on binocular rivalry. Methods. The durations of exclusive visibility of the dominant and nondominant eye target in binocular rivalry were measured in 14 subjects. The dominant eye was determined by using the hole-in-card test (sighting dominance). In study 1, contrast of the target in one eye was fixed at 100% and contrast of the target in the other eye was varied from 100% to 80% to 60% to 40% to 20%, when using rectangular gratings of 1, 2, and 4 cycles per degree (cpd) at 2°, 4°, and 8° in size. In study 2, contrast of the target in the nondominant eye was fixed at 100% and contrast of the target in the dominant eye was varied from 100% to 80% to 60% to 40% to 20%, when using a rectangular grating of 2 cpd at 4° in size. Results. In study 1, the total duration of exclusive visibilities of the dominant eye target; that is, the target seen by the eye that had sighting dominance was longer compared with that of the nondominant eye target. When using rectangular gratings of 4 cpd, mean total duration of exclusive visibility of the dominant eye target was statistically longer than that of the nondominant eye target (p < 0.05). In study 2, reversals (in which duration of exclusive visibility of the nondominant eye becomes longer than the dominant eye when the contrast of the dominant eye target is decreased) were observed for all contrasts except for 100%. Conclusions. The dominant sighting eye identified by the hole-in-card test coincided with the dominant eye as determined by binocular rivalry. The contrast at which reversal occurs indicates the balance point of dominance and seems to be a useful quantitative indicator of eye dominance to clinical applications.

Diurnal variation of human corneal curvature in young adults.

PURPOSEnTo elucidate the diurnal variation of human corneal curvature with regard to gender and menstrual cycle.nnnMETHODSnChanges in corneal curvature and intraocular pressure (IOP) were measured over 24 hours in 14 young adults using corneal topography and a non-contact tonometer. In study 1, seven males and seven females (after menses) were measured. In study 2, four females out of the seven volunteers who participated in study 1 were measured again during menses.nnnRESULTSnThe females after menses showed a remarkable diurnal variation throughout 24 hours. A significant difference between the light-wake periods and dark-sleep periods of 0.83 +/- 0.15 D was found (P < .01). Corneal curvature was significantly flatter during menses than after menses in the light-wake period (P < .05). In the males, no significant diurnal change (0.21 +/- 0.12 D) was measured in corneal curvature.nnnCONCLUSIONSnDiurnal variation of corneal curvature was significant, approximately 0.83 D in young females after menses, and corneal curvature became flatter during menses in young females. Diurnal variation of corneal curvature is an important parameter for planning refractive surgery and contact lens wear.

Effects of ocular dominance on binocular summation after monocular reading adds

PURPOSE: To investigate the relationship between ocular dominance and binocular summation with monocular reading adds. SETTING: Department of Orthoptics and Visual Science, School of Allied Health Sciences, Kitasato University, Sagamihara, Kanagawa, Japan. METHODS: Contrast sensitivities were measured by having subjects view contrast charts at spatial frequencies of 1.5, 3.0, 6.0, 12.0, and 18.0 cycles per degree after the addition of positive spherical lenses that ranged from +1.0 to +3.0 diopters (D). Through the use of a balance technique, the test group was quantitatively divided into 12 weak and 8 strong ocular dominance subjects on the basis of binocular rivalry. In study 1, binocular contrast sensitivity was measured in the weak and strong ocular dominances by adding a positive spherical lens in front of 1 eye, whereas the other eye was fixed at a corrected distance. RESULTS: In study 1, the binocular summation was observed only after adding positive spherical lenses in the nondominant eye. The differences in binocular contrast sensitivity that occurred after adding a positive spherical lens in the dominant eye versus that seen in the nondominant eye were statistically significant in the strong ocular dominance subjects who had +1.5 D and +2.0 D defocuses (P<.05; analysis of variance). CONCLUSIONS: Binocular summation was effectively maintained with reading adds in the nondominant eye and was significantly influenced by the magnitude of ocular dominance. Evaluating binocular summation after monocular reading adds seems to be a good method to evaluate adaptability to monovision.

Electron-Microscopic Study of Iris Nerves and Muscles in Diabetes

The ultrastructure of the iris muscles and innervating nerves in patients with diabetes mellitus and approximately age-matched controls was examined by electron-microscopy. The specimens were obtained during cataract surgery. There were definite histopathological alterations at the nerve terminal innervating the dilator muscle, e.g. the presence of mitochondrial abnormalities, dense bodies and lamellar structures. No change was noted at the nerve terminal to the sphincter muscle. Moderate involvement of the muscle, especially at the sphincter, was observed in the specimens of diabetics. The control specimens had no change at the nerve terminals, while moderate change was observed at the sphincter muscle. Therefore, the change in the sphincter seen in the specimens of diabetics seemed to be mainly the result of the aging process, though the existence of early sympathetic neuropathy was confirmed.

Bilateral innervation of the musculus levator palpebrae superioris by single motoneurons in the monkey

The location of motoneurons innervating the musculus levator palpebrae superioris (LPS) was studied in the monkey (Macaca irus) by using Fast blue (FB) and propidium iodide (PI) as retrograde neuronal tracers. In each monkey, FB was injected into the LPS of one eye and PI into the LPS of the other eye. Neuronal cell bodies labeled with FB and/or PI were seen intermixed bilaterally through the entire rostrocaudal extent of the central caudal nucleus. While single-labeled (70%) cell bodies predominated, many double-labeled (30%) cell bodies were also encountered. Each of the double-labeled neurons was concluded to supply the LPS on both sides by way of axon collaterals.

Innervation of melanocytes in human iris

Contacts between melanocytes and nerve terminals in human iris stroma were investigated by means of electron microscopy. Four distinct types of nerve terminal making synaptic contacts with melanocytes can be distinguished: (1) nerve terminals containing only empty synaptic vesicles (400–800 Å in diameter) and with intervening basement membrane material (separation 1000 Å); (2) nerve terminals with both empty vesicles and granulated vesicles (600–1100 Å in diameter) also with intervening basement membrane material (separation 750 Å); (3) nerve terminals containing empty vesicles and forming close contacts with melanocytes (distance about 400 Å) without interposed basement membrane material, and (4) nerve terminals containing both empty and granulated vesicles (750 Å in diameter) which make closer contacts with melanocytes (distance 270 Å) without interposed basement membrane material. Type (1) and type (3) nerve terminals are thought to be cholinergic; type (2) and type (4) nerve terminals appear to be adrenergic. Taking into consideration these morphologic findings and previously reported data, it seems justified to postulate the presence of trophic innervation of melanocytes in the human iris.

Ischemic Optic Neuropathy Associated with Subarachnoid Hemorrhage after Rupture of Anterior Communicating Artery Aneurysm

Two clinical cases in which ischemic optic neuropathy (ION) occurred after subarachnoid hemorrhage (SAH) are reported. Hemorrhage in the proximity of the optic chiasm was confirmed in 2 cases following rupture of an anterior communicating artery aneurysm. Optic disk atrophy with excavation and permanent visual field defect (altitudinal superior hemianopia) occurred in both cases. ION seems to occur in association with the optic nerve coincidental with the hyperdensity side of SAH on head CT scan. The incidence of ION appears to be attributable to an insufficient blood supply to arteries distributed in the posterior part of the optic nerve as a result of SAH.

Short‐cycle periodic alternating (ping‐pong) gaze

Periodic a l t e rna t ing horizontal-gaze deviat ions may exhibit long or short In the long cycle, the eyes remain tonically deviated for 1 to 2 minutes before shifting to the opposite side; the rhythmicity is similar to that of periodic alternating nystagmus (PAN), prompting the presumption that the gaze deviation represents PAN without the fast p h a s e s . ’ ~ ~ , ~ In the shor t cycle, the eyes change directions immedia t e ly o r a f t e r a few seconds delay.3,6-1s Senelick7 designated this phenomenon as “pingpong gaze.” Most reports of this abnormality are descriptive and lack oculographic documentation of the slow eye movement waveform. We repor t a patient in whom we obtained oculography and a p o s t m o r t e m e x a m i n a t i o n , and review the 18 patients described in the literature.