Opposite Eye Research Articles

Surgical correction of enophthalmos and diplopia. A report of 38 cases.

Enophthalmos, hypophthalmos, and diplopia are complications of orbital injury. This article reviews the causes of these sequelae, describes a method of strategic implantation of bone grafts to the orbit (and malar bone), and reports the long-term (six months to eight years) results in 38 cases. As a result of bone grafting, all but two patients had a correction of the enophthalmos to within 1 to 2 mm of the opposite eye. Of the 20 patients with diplopia, 15 had correction, and an additional four had an improvement of diplopia so it occurred in only one field of gaze. Of the 22 patients with grafts to the malar bone, 16 were thought to have good to excellent results; however, six developed some degree of reabsorption at the graft site. No patients had any decrease in vision. The advantages and disadvantages of the surgical procedure are described and compared with other methods.

Penetrating keratoplasty in rabbits induces latent HSV-1 reactivation when corticosteroids are used

The increased incidence of corneal graft failure in patients with herpes simplex virus (HSV) keratitis may be due in part to reactivation of latent HSV following surgical corneal trauma and postoperative corticosteroid therapy. To determine the onset, frequency, and nature of HSV recurrences following penetrating keratoplasty (PKP), 21 HSV type 1 (HSV-1) latently infected rabbits underwent unilateral autograft PKP. Opposite unoperated eyes served as HSV-1 latently infected controls. Corneal autografts were performed so that immunologic graft rejection would not be confused with recurrent HSV-1 stromal disease. After PKP, 11 of the 21 eyes were treated with dexamethasone. Ocular cultures and slit-lamp examinations were performed daily for the first postoperative 8 days and every other day thereafter for 82 days. Nine (82%) of the 11 dexamethasone-treated PKP eyes, 2 (20%) of the PKP eyes not treated with dexamethasone, and 3 (17%) of the 18 unoperated eyes had positive HSV-1 ocular cultures. Geographic ulcers appeared only in the PKP eyes treated with dexamethasone; 9 (82%) of the 11 PKP eyes treated with dexamethasone developed geographic ulcers. Between the 24th and 90th postoperative days, stromal keratitis appeared in 5 (56%) of the 9 PKP eyes treated with dexamethasone and in 2 (25%) of the 8 PKP eyes not treated with dexamethasone. Autograft PKP with postoperative corticosteroids significantly increased HSV-1 ocular shedding, epithelial ulceration, and stromal keratitis. This experimental model provides a useful tool to further investigate the development and treatment of HSV-1 epithelial and stromal recurrences after PKP.

Monensin induces distortion of optic nerve crossing at the chick embryo chiasm

The effects of intraocular injection of monensin, a specific inhibitor of membrane glycoprotein transport within the axon, on the development of the chick embryo optic nerve were examined. A proportion of axons growing from the monensin-injected eye were misrouted into the opposite optic nerve at the chiasm and grew to the retina of the opposite eye. These results suggest that formation of the decussation pattern at the chiasm primarily depends on neurite fasciculation mediated by membrane glycoproteins.

Cortical contrast gain control in human spatial vision.

1. We evaluated human visual cortical contrast gain using visual evoked potential (VEP) measurements. The steady-state VEP was elicited by 7.5 Hz contrast modulation of a 6 cycles/deg sinusoidal grating. The stimulus may be regarded as the sum of a steady grating (C) and a counterphase grating of the same spatial frequency (delta C). The counterphase grating is modulated sinusoidally in time. 2. The VEP was measured to combinations of different modulation contrasts (delta C) and different mean levels of grating contrast (C) which produced stimuli with contrast modulation depths (delta C/C) ranging from 0.0625 to 1.0 ('on-off'). 3. The VEP signals were Fourier analysed and the amplitude and phase of the first (7.5 Hz) and second (15 Hz) harmonic frequency components were examined. The monocular VEP to a contrast-modulated grating contains significant first and second harmonic frequency components. 4. The amplitude and phase of the monocular VEP was plotted as a function of delta C for each mean level of contrast explored. The amplitudes of both the first and second harmonic frequency components grow with increasing delta C. However, the slope of each function depends on the mean contrast (C): with higher levels of C, the slope of the function is more shallow. Furthermore, at each level of C the amplitude of the first harmonic frequency saturates at a lower delta C than does the second harmonic frequency component. VEP amplitude is therefore not determined by the absolute contrast change (delta C) alone. The VEP phase of the first harmonic frequency shows less dependence on either modulation or on mean contrast; the phase of the second harmonic frequency component is strongly dependent on mean contrast (C) but not on delta C. 5. When the second harmonic amplitude component of the VEP response (R) is expressed as Ractual/Rmax, where Rmax is the response to C = delta C (i.e. 'on-off'), all second harmonic VEP functions can be well fitted with a power function. This is not the case for the function of the first harmonic amplitude data. 6. A dichoptic VEP was obtained by presenting the steady and counterphase gratings to opposite eyes. The dichoptic VEP, in distinction to the monocular VEP, contains only a second harmonic frequency component. The amplitude of the second harmonic frequency component grows with increasing delta C, similar to the function seen for the monocular VEP.(ABSTRACT TRUNCATED AT 400 WORDS)

Simultaneous Bilateral Conjunctival and Orbital Lymphoma Presenting as a Conjunctival Lesion

A 44-year-old man with the diagnosis of a conjunctival lymphoma in the left eye was also found on further evaluation to have a lymphoma in the opposite orbit. The patient had no systemic signs of the disease, and was treated with localized radiation therapy. Although simultaneous presentation of lymphoma affecting the conjunctiva in one eye and the orbit on the opposite side is rare, any patient with an isolated conjunctival lymphoma should have a careful evaluation of the opposite eye and orbit, including an orbital computed tomographic scan to rule out simultaneous involvement.

Interocular transfer of extinction of visual pattern discriminations in split-chiasm and split-brain cats

The interocular transfer of the extinction of visual pattern discriminations was studied in cats with either section of optic chiasm (split-chiasm cats) or combined sections of chiasm and forebrain commissures (split-brain cats). Visual pattern discriminations were monocularly learned and their interocular transfer was assessed through the opposite eye. Then, learning was unilaterally extinguished and interocular transfer of extinction was tested on the other side. In split-chiasm cats, the total number of trials to extinction criterion (EC) was significantly lower with the second eye than with the first eye, indicating a successful interocular transfer. In split-brain cats, EC with the second eye was attained faster than with the first in some performances; it was similar with both eyes in other tasks, and with the second eye was higher than with the first in still other tasks. Statistical analysis applied to this group of split-brain cats pointed out that extinction performances with the two eyes were not significantly different. These findings suggest that interocular transfer of extinction was abolished in split-brain cats and that memory for extinction was unilaterally established in the absence of forebrain commissures.

Neural correlates of motion after-effects in cat striate cortical neurones: interocular transfer

Interocular transfer of motion after-effects was assessed in the lightly-anaesthetized feline striate cortex. Neurones were adapted with square-wave gratings of optimal orientation and spatial frequency, or with randomly textured fields, drifting continuously at optimal velocity in their preferred or null directions. Neural after-effects were assessed as consequent changes in directional bias, using similar test patterns swept back-and-forth in the same directions and presented to the same or opposite eyes. All results were compared with controls, embodying similar tests following a period of exposure to a uniform background or stationary textured field. The majority of binocularly-driven complex and simple cells tested evinced positive interocular transfer of after-effects. After-effects, whether elicited monocularly or interocularly, were direction-specific. With gratings, after-effects elicited interocularly were always weaker than those obtained monocularly. After-effects evoked monocularly by texture adaptation were weak in comparison to those evoked by gratings; interocular transfer in this case was negligible. In neurones strongly dominated by one eye, adaptation of the non-driving eye yielded, at best, extremely weak after-effects through the other eye. In purely monocular neurones, no transfer could be induced. These results confirm the expectation that motion after-effects arise cortically rather than precortically. The partial interocular transfer seen in binocularly-driven cortical cells suggests that these neurones represent a second-stage processing of inputs from lower-order complex (or simple) cells, themselves driven monocularly or strongly dominated by one eye.

Septic thrombosis of the cavernous sinuses.

Cavernous sinus thrombosis may occur as a complication of infectious and noninfectious processes. Septic thrombosis of the cavernous sinuses most commonly follows infections of the middle third of the face due to Staphylococcus aureus. Other antecedent sites of infection include paranasal (usually sphenoid) sinusitis, dental abscess and, less often, otitis media. Fever is a nearly constant finding, but headache may not be prominent. Periorbital edema, chemosis, proptosis, and limitation of extraocular movements (especially lateral gaze) develop in almost all recognized cases. Involvement of the opposite eye frequently appears within two days following the onset of unilateral signs. Although computed tomography may be helpful, magnetic resonance imaging is probably the diagnostic procedure of choice. Treatment includes appropriate antibiotics and, oftentimes, surgical drainage of the primary focus of infection. Less than half of the patients recover completely; the mortality rate is approximately 30%.

Contrast Sensitivity After Epikeratophakia

Epikeratophakia is a rapidly evolving surgical procedure for the refractive correction of aphakia. Even when Snellen acuity after epikeratophakia is normal, patients often report a subjective degradation of the visual image through the surgically corrected eye. To further define visual performance in the patient with optically successful epikeratophakia, we examined contrast sensitivity in two patients surgically corrected for monocular aphakia. Contrast thresholds were measured over a range of spatial frequencies using both computer-generated sinusoidal gratings and a commercially available wall chart system. The eye with epikeratophakia in each case was compared with the opposite normal eye with comparable acuity. One patient was also tested prospectively in the same eye both before and after surgery. Data demonstrate a depression of the contrast sensitivity function in the middle and high spatial frequencies induced by the placement of an epikeratophakia lenticule when compared with the normal eye or contact lens-corrected, preoperative aphakic eye with comparable good acuity. These findings may explain the subjective experience of epikeratophakia patients.

Immunological analysis of a destructive pattern of intraocular tumor resolution.

Spontaneous rejection of syngeneic intraocular P91 mastocytoma occurred by a T cell-dependent immune process that produced extensive, irreparable damage to normal ocular tissue indicative of a delayed-type hypersensitivity (DTH) lesion. We investigated the contribution of other effector modalities in this tumor resolution. Antibody was not responsible for either tumor rejection of phthisis of the tumor-containing eye since passively transferred hyperimmune serum failed to produce either tumor rejection or the characteristic ocular lesions. Moreover, the destructive pattern of tumor rejection occurred in splenectomized hosts which had depressed anti-P91 serum antibody and in a congenic strain (B10.D2oSn) lacking the C5 complement component. The likelihood that tumor necrosis factor (TNF) was involved in this pathogenesis was also ruled out by the observation that P91 tumor cells were not susceptible to lysis by recombinant TNF. A different pattern of tumor resolution was observed when the opposite eye was challenged with tumor. In this case, the tumor was rejected without damaging any major ocular structures. Histological analysis demonstrated a mononuclear cellular infiltrate which was identified by immunohistology to be Thy 1+, Lyt 2+. Thus, although both forms of cell-mediated immunity are available to the host, only one predominated in each eye. These results suggest that unique immunological control mechanisms influence the outcome of tumor resolution in the eye.

The cyclopean eye and its implications: Vergence state and visual direction

The cyclopean illusion ( Hering, 1861) is an anomalous lateral shift in the apparent direction to a monocularly seen target, which arises when a change in vergence is made by the opposite (nonobserving) eye. Surprisingly, this directional illusion does not arise, when the observed target is an afterimage or an intermittently illuminated (4–8 Hz) object. Instead, during convergence, a monocularly imprinted afterimage seems to move toward the observer, and a stroboscopically illuminated target seems to remain fully stationary. The apparent displacement of an afterimage in depth is particularly puzzling. Since binocular interactions in the persistance of monocularly induced afterimages can be demonstrated, it is conceivable that long-persistant afterimages arise, in part, from binocularly driven neurons in the visual cortex, and that a monocularly induced afterimage can thereby become the perceptual equivalent of a binocularly fused target.

The position of the crossed and uncrossed optic axons, and the non-optic axons, in the optic tract of the rat

The position of the crossed and uncrossed optic axons, and of the non-optic axons, within the optic tract was determined in the adult hooded rat. Horseradish peroxidase histochemistry and lesion-induced degeneration of axonal profiles were independently used to study the position of the three relevant populations of axons within the optic tract. The boundaries of the optic tract are distinct at all but its caudomedial border, where it abuts the supra-optic commissures running parallel to the fibres of the optic tract. Labelling the crossed population of optic axons, or inducing their degeneration, both demonstrate a clear caudomedial border of the optic tract, although a number of optic axons stray out of the optic tract and course within the supra-optic commissures immediately caudomedial to the tract. The uncrossed optic axons are, as a population, positioned relatively deep in the optic tract, towards its dorsal border. A few occur at further ventral positions, but their density is greatly reduced there. There is also a very thin region along the dorsalmost edge of the optic tract free of uncrossed optic axons. The relative position of the uncrossed to the crossed optic axons is discussed in the context of the mammalian optic tract as a chronological map: spatial position in the tract may reflect temporal order of axonal arrival during early development. A large population of non-optic axons belonging to Gudden's commissure courses within the boundaries of the optic tract at a relatively ventral position. They are most frequent caudomedially, and are absent rostrolaterally. Hence, axons of the optic tract and Gudden's commissure are substantially intermingled in the caudomedial half of the optic tract. These non-optic axons greatly outnumber the uncrossed optic axons, and will consequently distort counts of uncrossed optic axons based on intact profiles that remain after removal of the opposite eye. However, they are still a minority in comparison to the crossed optic axons in this region.

Pseudoscopic viewing: transfer and persistence of reversed depth relations from the viewing of photographs to the real scene.

After viewing stereo pictures pseudoscopically (that is, with the pictures of the stereo-pair presented to the opposite eyes) part of the real scene depicted was perceived as inside out from the standpoint of depth during normal binocular vision. Experiments were designed to investigate this form of transfer but, since serious consequences can arise when an inside-out percept persists in normal binocular vision, it was intended that the experiments would be restricted to transfer of a less extreme kind. The scene chosen had not developed persistence during early trials but, surprisingly, one subject taking part in these experiments did experience some transfer from pseudoscopic direct viewing to normal binocular vision.

CYSTEAMINE EYEDROPS DISSOLVE CORNEAL CRYSTALS IN YOUNG PATIENTS WITH NEPHROPAT11IC CYSTINOSIS

In nephropathic cystinosis, corneal cyatine crystals are present by one year of age and increase in density with time. The crystals are blamed for the photophobia and corneal erosions which plague older patients. He studied the safety and efficacy of eyedrops containing cysteamine, a cystine-depleting agent, in dissolving corneal crystals. First, cystinotic corneal stromal cells, cultured from a penetrating keratoplasty specimen, were depleted of 82% of their cystine by 1 mM cysteamine within 30 min. Second, rabbits treated for 8h per day for 3 weeks with 50 mM cysteamine eyedrops in a placebo-controlled, masked study exhibited no toxicity. Third, two cystinotic children (<2 years old) received cysteamine eyedrops (10 mM, hourly while awake) in a double-masked, placebo controlled trial. Normal saline was put in the opposite eye. In both children, biomicroscopic examination and silt lamp photography documented : a) Bilateral increase of crystals in the cornea between the start of oral cysteamine and the start of the eyedrop protocol; b) Nearly complete clearing of crystals from the cysteamine-treated corneas after 4-5 months of eyedrops; c) Progression or lack of regression in the corneas not treated with cysteamine. No toxicity was observed, and we are now treating the placebo eyes with cysteamine and enrolling older patients. This represents the first in vivo demonstration of crystal dissolution by cysteamine in cystinosis, and suggests that oral cysteamine, if adequately delivered to target tissues, might dissolve crystals in other cystinotic organs also.

Abduction nystagmus in internuclear ophthalmoplegia.

We tested the hypothesis that abnormalities of the abducting eye in internuclear ophthalmoplegia reflect an adaptive process that helps overcome the adduction weakness of the opposite eye. This response operates under the constraints of Hering's law of equal innervation: any attempt to increase the innervation to a weak muscle in one eye must be accompanied by a commensurate increase in innervation to the yoke muscle in the other eye. In 4 patients with internuclear ophthalmoplegia, we patched one eye for 1 to 5 days to allow time for the central nervous system to optimize innervation for the habitually viewing eye. We predicted that there would be a conjugate adjustment of innervation that would diminish the abduction overshoot and backward postsaccadic drift made by the habitually viewing eye. This was the case in 3 of our 4 patients. Our findings show that the abduction nystagmus is a manifestation of a normal adaptive response in some patients with INO.

The crossed projection from the temporal retina to the dorsal lateral geniculate nucleus in the rat

The crossed projection from the temporal crescent in the rat's retina was studied by producing a discrete retinal lesion in one eye and examining the dorsal lateral geniculate nucleus and superior colliculus contralateral to the lesion for anterograde degeneration products. The position of this crossed degeneration was described in relation to the uncrossed retinal termination in the same structures by injecting the opposite eye with [ 3H]proline and processing the tissue for autoradiography. The location of the retinal lesion in relation to the temporal cresent was identified by injecting the dorsal lateral geniculate nucleus ipsilateral to the lesioned eye with a fluorescent tracer, to retrogradely label the ipsilaterally projecting retinal ganglion cells in the lesioned eye. Retinal lesions that were histologically verified to be restricted to the temporal crescent produced crossed degeneration in the superior colliculus at its rostral border, in accord with this projection's published visual topography. These same lesions consistently yielded a very circumscribed and sparse amount of degeneration in the contralateral dorsal lateral geniculate nucleus at its dorsomedial border, abutting the optic tract dorsally and the lateroposterior nucleus medially. The degeneration bore no consistent relationship to the position of the uncrossed retinal terminal field, which is situated further 9ventrally in the dorsal lateral geniculate nucleus; rather, this crossed temporal projection terminated in the outer shell of the nucleus along its medial border. This crossed temporal retinogeniculate projection, together with the crossed projection from nasal retina, forms a continuous map of the complete contralateral retina in the outer shell of the dorsal lateral geniculate nucleus, likely to arise from a population of retinal ganglion cells possessing small soma sizes. This dorsomedial part of the rat's dorsal lateral geniculate nucleus, receiving a crossed projection from the temporal retina, may by similar to the cat's lamina 3 in the medial interlaminar nucleus of its retinogeniculate pathway. This result clarifies the homologous subdivisions of the dorsal lateral geniculate nucleus in the rodent and feline thalamus.

The penetration of ceftazidime into the inflamed rabbit eye.

Acute endophthalmitis was unilaterally induced in 8 rabbits by intravitreal injection of 5 micrograms Escherichia coli endotoxin. A reproducible increase in aqueous humour polymorphonuclear neutrophils and total protein content was observed after 24 h (mean +/- SD: 2400 +/- 274 X 10(6)/l and 3.7 +/- 0.4 g/l, respectively). In the opposite eye only minor changes occurred, making it suitable as a paired control. The intraocular penetration of ceftazidime was then studied in 30 rabbits after i.v. injection of 50 mg/kg body weight. The mean penetration into aqueous humour of the eyes with and without endophthalmitis was 64 and 10%, respectively. In the vitreous body the corresponding penetration was 5 and 1%. The concentration of ceftazidime achieved in the intraocular structures was sufficient to inhibit the growth of pathogens, i.e. Enterobacteriaceae, commonly responsible for intraocular infections.

Fate of uncrossed retinal projections following early or late prenatal monocular enucleation in the mouse.

In mammals binocular vision is made possible by the existence in the temporal retina of ipsilaterally projecting ganglion cells (IGCs) (with axons that do not cross the brain midline and join optic fibers from the opposite eye). To learn whether early interactions between fibers of each eye play a role in generating a mixed ipsi + contralateral projection pattern, we studied with horseradish peroxidase the origin of uncrossed retinal projections in mice that developed after one eye was destroyed at very early embryonic ages. One eye was removed on embryonic day 16 (E16; when optic fibers have grown past the chiasm bilaterally, but very few have grown into the visual centers) or on E13 or E12 (when few or no optic fibers have passed the presumptive chiasm region). Normal adult mice have a mean of 946 IGCs (range: 784-1,073) within the temporal sector of the retina, and less than 25 in the rest of the retina. In adult mice enucleated at E16, an average of 1,354 (1,215-1,484) IGCs are present within a clearly demarcated temporal sector of the remaining retina and 265 (152-312) are present throughout the rest of the retina. In both the temporal and nasal retina the excess IGCs in these mice have, generally, very small somas. In some of these mice the most peripheral part of the temporal sector contains fewer IGCs. In E12 or E13 enucleates, IGCs are also generally located in a narrow (often narrower than normal) region along the temporo-inferior retinal border, but their number is less than in normal or E16-enucleated mice: E13 enucleates have a mean of 639 cells (range: 361-875) in the temporal sector and 109 (8-275) in the rest of the retina. Following enucleation of one mouse at E12, the respective values are 349 and 31 cells. The reduction in numbers of IGCs in these mice is especially pronounced for ganglion cells with small cell bodies. These findings suggest that the development of uncrossed projections in mice depends on selective guidance mechanisms of axons from temporal retina through the chiasm. These may consist of interactions of optic axons with guidance cues distributed in the presumptive chiasm (possibly at early stages) and also of fiber-fiber guidance mechanisms, in particular between fibers from each eye.

Changes in the oscillatory potentials of the electroretinogram in glaucoma.

Dark adapted and progressively light adapted electroretinograms (ERGs) were recorded from 34 normals and from 45 glaucoma patients. To enhance the oscillatory potentials (OP) the ERGs were highpass-filtered. The OP were characterized by two indices: their root-mean-square value and the inter-flash interval for which the maximal amplitude was obtained. In most of the glaucomatous OP, 50 of 81 eyes, both indices were abnormal, in 22 one parameter was abnormal and only in 9 were both parameters normal. In 13 of the 14 OP recorded from the opposite ('normal') eye of patients with unilateral glaucoma either one or both of the indices were abnormal. These findings indicate that the damage to the retina in glaucoma may extend more distally than the ganglion cell layer and that subclinical changes might be revealed by OP changes.

Distribution of motoneurones innervating extraocular muscles in the brain of the marmoset (Callithrix jacchus).

Extraocular muscle motoneurones were localised in the oculomotor nucleus (ON), trochlear nucleus (TN) and abducens nucleus (AN) in the marmoset brain using the horseradish peroxidase (HRP) retrograde labelling technique. HRP pellets injected into individual extraocular muscles revealed one or more groups of labelled neurones occupying discrete loci within these nuclei. Relatively little overlap of motoneurone pools was observed, except in the case of the inferior oblique and superior rectus muscles. Injections of HRP into the medial rectus muscle revealed three separate populations of labelled cells in the ipsilateral ON. Motoneurones innervating the inferior rectus muscle were mainly localised in the lateral somatic cell column of the ipsilateral ON. A second smaller grouping was observed in the medial longitudinal fasciculus. The inferior oblique muscle motoneurones were localised in the ipsilateral medial somatic cell column intermingled with motoneurones supplying the superior rectus muscle of the opposite eye. The superior oblique muscle motoneurones occupied the entire TN and the lateral rectus muscle motoneurones the AN. It was concluded that the organisation of nuclei and subnuclei responsible for controlling the extraocular muscles in the marmoset is broadly similar to that of other primates.