Isometric force measured in human horizontal eye muscles attached to or detached from the globe

Background Human eye muscle tension has been measured directly only in detached condition. The purpose of this study is to compare force development in single, horizontal human eye muscle during saccadic eye movements, first when the muscle was still attached and later when it was detached from the globe.Methods Eleven horizontal muscles of eight patients were examined during surgery under topical anesthesia for concomitant strabismus. None of the muscles examined had been operated before. Isometric muscle tension was recorded with a strain gauge system, to which the muscle tendon was attached by a silk suture. The subjects made saccadic eye movements with the non-recorded eye by fixating light-emitting diodes in the center and at 10, 20, and 30° horizontally to each side. Continuous and stepwise saccades were produced. In the tension signals, peak tension (Fp), steady tension (Fs), and the ratio Fp/Fs were measured. Statistical analysis was done with multivariate analysis of variance.Results The values of Fp, Fs, and Fp/Fs at different amplitudes of the saccadic eye movements were compared in the attached and the detached muscle. There were no consistent statistical differences between the values obtained in the two conditions.Conclusions The muscle force development, measured at the tendon, was the same in muscles attached to the globe and in muscles free from the globe. Thus isometric muscle tension can be adequately recorded in muscles still attached to the globe, which increases the possibilities for studying contractile properties of various eye muscles during ophthalmic surgery procedures performed under topical anesthesia.Financial support for this study was obtained from The Sigvard & Marianne Bernadotte Research Foundation for Children’s Eye Care to the authors GL, RB and MB; The Research Council of the Stockholm County to GL; The Karolinska Institute Research Foundation, to GL and ST; a grant of the University of Bologna to ECC (ex 60% MIUR); a donation of the Fondazione Cassa di Risparmio in Bologna to ECC; and a grant of the MIUR (ex 40%) to CS.     

Changes of visual localization induced by eye and neck muscle vibration in normal and strabismic subjects

· Background: It has been reported that vibratory activation of eye- and neck-muscle proprioception can induce eye position changes in normal and strabismic subjects. This study investigated the effects of proprioception in the eye and neck muscles on space localization. · Method: Vibration was applied to either the eye or neck muscle in normal subjects, intermittent exotropes, and constant exotropes/esotropes. The subjects pointed at the immediately remembered position of an extinguished visual target with the hand both before and immediately after vibration of the muscles under binocular and monocular viewing conditions. The hand-pointing performance in darkness was recorded by an infrared camera, and the pointing shifts were analyzed qualitatively and quantitatively. · Results: With vibration of the vertically moving muscles of the eye and neck, the direction of the pointing shifts was the same in all groups of the subjects and under all viewing conditions. With vibration of the horizontally moving muscles of the eye and neck, the directions were the same in the normals and in most of the intermittent exotropes. However, in the constant exotropes and esotropes, the directional shifts were dependent on which eye was vibrated, and the directions were more variable, always directed only to one side. · Conclusion: Proprioception in the eye and neck muscles participates in visual space localization, but the effects of proprioceptive activation were differed in normal subjects from those in patients having constant strabismus. The differences may be related to the level of binocular function. Received: 4 January 1999 Revised version received: 22 April 1999 Accepted: 22 April 1999     

Eye position changes induced by neck muscle vibration in strabismic subjects

· Background: In normal subjects vibratory stimulation of neck muscle proprioceptors can induce eye position change and visual illusory movement. The direction of apparent movement is vertical when the back muscles of the neck are stimulated and horizontal when lateral-rotation muscles are stimulated. The effect of muscle proprioceptor stimulation in individuals with defects in binocular vision, such as strabismus, has not been studied previously and is the subject of the present report. · Methods: In 23 strabismic patients with different levels of binocular vision, 70-Hz mechanical vibration was applied to three groups of neck muscles under both dark and normal light conditions, and eye position changes were recorded for each eye using an infrared reflection technique. The dominant eye fixated on a target while the non-dominant eye was covered. · Results: When the back muscles were stimulated, eye position changed in a downward direction, as previously demonstrated in the normal subjects. However, in strabismic subjects with poor binocular vision, stimulation of the horizontal rotation neck muscles resulted in eye position changes generally to the same side regardless of the muscle group activated. This differed from normal subjects, where the direction of the eye position changes is related to the group of muscles stimulated. The direction and amplitude of the eye position changes were the same under dark and light conditions. · Conclusion: Proprioceptive information from neck muscles plays an important role in regulation of gaze direction. The difference that exists between normal subjects and strabismic patients is most likely related to differences in binocular function. Received: 10 October 1997 Revised version received: 12 March 1998 Accepted: 17 March 1998     

Unilateral pigmentary degeneration of the retina associated with heterochromia iridis

· Background: For the past 5 years, a 56-year-old patient has been displaying monocular progressive pigmentary changes in the left eye. Heterochromy of the left eye has been known since childhood. The other eye is clinically and functionally normal. The patient was adopted and he has no children. Therefore, we have no family history. · Methods: The patient was examined clinically and by means of electroretinography, electrooculography, perimetry, computer tomography, pulsatile ocular blood flow (POBF) measurement, serology and Doppler sonography. · Results: Electrophysiology displayed a considerable reduction of scotopic and photopic ERGs, a reduced dark-through, and a reduced light-rise in the left eye, whereas the fellow eye was normal. The visual field was limited to 5 deg around the fixation point, and a peripheral crescent-shaped arch encircled the temporal-inferior quadrant concomitant to the pigmentary changes. By computer tomography and Doppler sonography a vascular affection was excluded. The left eye displayed lower POBF values. All serological tests were found negative. · Conclusion: The clinical picture and negative exclusion criteria indicate a unilateral retinitis pigmentosa. However, with regard to the literature an unequivocal diagnosis can only be made upon hereditary evidence. Received: 30 January 1998 Revised version received: 6 April 1998 Accepted: 7 April 1998     

Effects of eye muscle proprioceptive activation on eye position in normal and exotropic subjects

Background: Activation of muscle spindles by vibration of eye muscles is known to induce illusory movements of fixated targets, but the effects on eye position have not been studied, either in normal subjects or in patients with exotropia. Methods: Eye position was recorded from the covered, non-dominant eye with an infrared system in 11 subjects with normal eyes and binocular vision and in 10 patients with exotropia and abnormal binocular function. Activation of eye muscle spindles was done by vibration at 70 Hz of the inferior and lateral rectus muscles of the dominant eye, fixating a light-emitting diode in subdued light. Results: Vibratory activation of proprioceptors in the inferior rectus muscle induced an eye movement mainly directed upward in both normal and exotropic subjects. The magnitude of the movement was on average 2.7 deg in normals and 2.4 deg in exotropes. Lateral rectus vibration induced a movement that was mainly temporally directed (abduction) of an average 2.1 deg in normal subjects, but a nasally directed (adduction) movement of 4.2 deg in exotropic subjects. In normal subjects the eye movement is of the same direction as the earlier reported visual illusory movements induced by the same type of proprioceptive activation, but in exotropic subjects the movements is in the opposite direction. Conclusions: Proprioceptive activation of eye muscles affects eye position, and the results also indicate that signals from eye muscles are processed differently in normals and strabismics, probably depending on the level of binocular function.     

Bielschowsky head-tilt test—II. Quantitative mechanics of the Bielschowsky head-tilt test

In ten recent cases of superior oblique (SO) palsy the involved eye elevated by 8.2 +/- 3.8 deg (standard deviation) on 45 deg ipsilateral head tilt. A computer model predicted a rise to only 4.1 deg but could easily achieve 8.2 deg by including reactions in the other cyclovertical muscles, notably on overaction of the superior rectus (SR). In 17 older cases the elevation on tilt rose to an average of 15 deg. The model shows that these deviations must be due to SR overaction. The analysis suggests that SR overaction is the main cause of the rapid increase in eye elevation in recent cases and further increases in older cases.     

Macular rotation with and without counter-rotation of the globe in patients with age-related macular degeneration

· Background: Macular rotation to treat exudative age-related macular degeneration (AMD) involves translocation of the fovea to a site with intact retinal pigment epithelium. To avoid the inevitable postoperative cyclotropia we combined this procedure with torsional muscle surgery. · Patients and methods: In 30 eyes the macula was rotated upward by 30–50° following complete artificial retinal detachment and a 360° retinotomy. Simultaneous torsional muscle surgery was not carried out in the first 8 eyes; in the remaining 22 eyes surgery of the oblique muscles was performed alone or in combination with surgery of two or four rectus muscles. Simultaneously or later, muscle surgery was performed on the fellow eye in 17 of these patients. Three of the eight patients who had no primary muscle surgery were operated on later. They had muscle surgery on the macular-rotated eye and on the fellow eye. · Results: Postoperatively, the silicone oil was removed from all but one eye and an intraocular lens implanted in all but two eyes. Five eyes developed a postoperative retinal detachment, three of them with proliferative vitreoretinopathy. Three other eyes developed a recurrence of the choroidal neovascularization. At last examination, 18 of the 30 eyes (60%) had a near vision of 0.4 or better, sufficient for the reading of normal newsprint. Six of the eight patients who did not undergo muscle surgery reported considerable disorientation caused by the postoperative diplopia and cyclotropia. The muscle operation, which has been performed in a total of 25 patients, conferred complete freedom from complaints in all but one patient. · Conclusion: Macular rotation succeeded in restoring reading vision in about half of cases of exudative AMD, at least in the short term. The most serious complication was the development of a retinal detachment. The extremely disorienting side effects of diplopia and tilted image could be prevented or effectively treated by muscle surgery for counter-rotation of the globe, if need be also in the fellow eye. Received: 16 September 1998 Revised version received: 27 November 1998 Accepted: 30 November 1998     

Eosinophilic granuloma (Kimura’s disease) of the orbit: a case report

· Background: Eosinophilic granuloma of the soft tissue, Kimura’s disease, is a benign slow-growing tumor that is manifested clinically by one or more inflammatory nodules involving mainly the face and scalp, but rarely the eye. · Case report: The patient was a 32-year-old male with swelling of the left lower eyelid, marked peripheral blood eosinophilia and increased serum immunogloblin E. MRI revealed swelling of all rectus muscles of the left eye, but no tumor mass. Corticosteroid treatment reduced the swelling of the eyelid, but it recurred after corticosteroid was discontinued. Eight years later the patient returned with a complaint of increased swelling of the left lower eyelid. An elastic, nontender, soft tumor mass was palpable subcutaneously in the left lower eyelid extending into the orbit. MRI revealed a tumor mass in the left orbital space. The parotid gland was also swollen and palpable. Both tumors were resected surgically, and histopathological study revealed prominent proliferation of lymphoid follicles with germinal centers showing interfollicular infiltration by eosinophils. The pathological findings in the parotid gland were similar. The diagnosis was Kimura’s disease. · Conclusion: This patient is unique in that he had no tumor at the first examination, only swelling of the rectus muscles, and a tumor mass appeared many years later. Unilateral swelling of the rectus muscles may be one of the first signs of Kimura’s disease. Not only tumor but also swelling of the rectus muscles limited ocular movement. Received: 30 June 1998 Revised version received: 5 October 1998 Accepted: 6 October 1998     

双眼集合持续状态时眼外肌结构的磁共振研究

目的应用磁共振成像（MRI）研究对称和非对称集合运动时眼外肌的影像学特征。设计实验研究。研究对象平均年龄（27．4±3．1）岁的正常志愿受试者8人。方法受试者先在非集合状态（不放置三棱镜）下进行眼眶水平、冠状、矢状位MRI扫描。然后分别在非对称性集合状态（将底向外的20“三棱镜置于右眼及左眼前）及对称性集合状态（双眼前各置底向外的10△三棱镜）下行眼眶三轴位MRI扫描。检查时受试者经45。反射角镜注视5m处点光源以克服复视。主要指标双眼集合时眼外肌收缩性变化和眼球转动角度。结果非对称性集合状态下，集合眼（置三棱镜眼）平均内转11．03°±1．44°，内旋1．0°，对侧眼内转1．40°±0．46°。集合眼较非集合眼的外直肌有显著性舒张性变薄（截面面积分别是0．4710±0．1077与0．5155±0．1168cm^2,P=0．037），其他眼外肌无显著性伸缩改变。对称性集合状态下，双眼平均内转5．26°±1．15°，集合眼与非集合眼比较，各眼外肌无显著收缩性变化。结论非对称性集合运动时，集合眼的外直肌舒张性变薄显著。对称性集合状态下和非对称性集合状态下，眼球内转幅度有显著性差异。     

Single retinal ganglion cell responses in the dark-reared rat: Grating acuity,contrast sensitivity,and defocusing

The visual acuity, refractive state, and depth of focus of the dark-reared hooded rat's dark-adapted eye were determined by recording the responses of retinal ganglion cell axons in the optic tract. The smallest square-wave grating to which the units responded subtended 0.22 c/deg. The contrast sensitivity function for sine-wave gratings peaked at 0.02–0.07 c/deg. Corrective lenses of ± 14 D reduced the responsiveness of optic tract units to 100% contrast square-wave gratings by only 20%, implying (1) that objects from 7 cm in front of the eye to optical infinity are in equivalent focus, and (2) that the depth of focus of the rat's eye is enormous.     

Improvement of the Osteo-odonto-keratoprosthesis according to Strampelli: influence of diameter of PMMA cylinder on visual field

· Background: In surgical management of severe corneal scarring, the osteo-odonto-keratoprosthesis (OOKP) according to Strampelli is recognised as the best choice. Nevertheless, the patients are handicapped by a restricted visual field. Enlarging the optical cylinder diameter should allow better rehabilitation of the patients. · Patients and methods: A mathematical model to calculate the theoretical maximum visual field according to the length and the diameter of the cylinder of a keratoprosthesis was developed. The theoretical values were compared with our findings in three OOKP patients operated on in our hospital. · Results: The theoretical extent of the visual field with a cylinder of 8 mm length is 55 deg if the diameter is 3 mm and 62 deg if the diameter is 3.5 mm. The visual fields of our OOKP patients in both types of keratoprosthesis are, however, below the theoretically calculated values. Implantation of a prosthesis with a diameter of 3 mm produced horizontal visual fields of 30 and 36 deg in two patients. In one patient with a prosthesis diameter of 3.5 mm the field was 53 deg. · Conclusions: The diameter of the visual field increases with the diameter and decreases with increasing length of the optical cylinder. In OOKP the implantation of a PMMA cylinder with a diameter of 3.5 mm is possible. The enlargement of the diameter of the optical cylinder leads to significant enlargement of the visual field. The size of the cylinder is limited by the diameter of the available root of the tooth. Received: 28 January 1998 Revised version received: 9 September 1998 Accepted: 10 September 1998     

The upper limit of human smooth pursuit velocity

The maximum smooth pursuit eye velocity was determined in five human subjects. Eye movements were recorded with the d.c.-coupled EOG. On each trial the target moved in a ramp, at a constant velocity between 10 and 200 deg/sec. In four subjects eye velocity was approximately 90% of target velocity up to a target velocity of 100 deg/sec. Eye velocity then saturated with a large variability from trial to trial (standard deviation 16 deg/sec). The fifth subject had eye velocities only 60% of these values.     

ISO-frequency curves of oculomotor neurons in the rhesus monkey

Static firing frequencies have been determined in extraocular motoneuronal discharge patterns for different eye positions within +/- 30 deg around the primary position. From these data iso-frequency curves were plotted stating all possible eye positions for a given firing rate. Such curves have been constructed for the lateral, medial, and inferior recti, the superior oblique and for the upward pulling muscles (without distinguishing superior rectus and inferior oblique). Fixation of eye position always involved natural synergistic action of all muscles. The iso-frequency curves of individual motoneurons are a family of almost parallel curves with mainly horizontal or vertical gradients. Especially for the superior oblique, the innervation gradients depend strongly on eye position. Motoneurons subserving the same muscle can have different innervation gradients at the same eye position.     

Effects of enucleation of the fixating eye on strabismic amblyopia in monkeys

The effects of enucleation of the fixating eye on the visual function of the deviating eye were studied in two rhesus monkeys with strabismic amblyopia. An esotropia was surgically induced when the monkeys were approximately 1 mo of age, and the fixating eyes were then enucleated at age 3 yr 11 mo. Four measures of visual function (photopic increment-threshold spectral sensitivity, scotopic spectral sensitivity, spatial modulation sensitivity, and temporal modulation sensitivity) were determined for both eyes prior to enucleation and for the deviating eyes over an 11-month period following the surgical removal of the fixating eye. Both monkeys showed some recovery of contrast sensitivity of their deviating eyes. The extrapolated cut-off values for their spatial modulation sensitivity functions increased from .27 to 2.8 c/deg for one animal and from .28 to 6.3 c/deg for the other. The extrapolated cut-off frequencies for the temporal modulation sensitivity functions of both animals showed an increase of 20-25 Hz compared to the pre-enucleation values. The spectral sensitivity functions of one monkey recovered to near normal values following enucleation, while both the photopic and scotopic functions of the other animal remained at pre-enucleation levels. Overall, the results of the experiments indicate that the removal of the fixating eyes of monkeys with strabismic amblyopia can result in significant improvements in the functional capacity of their deviating eyes.     

The effect of axial length on photodynamic therapy

PURPOSE: To determine the effect of the axial length of the eye on photodynamic therapy (PDT) light fluence. DESIGN: Laboratory investigation. METHODS: A calibrated Gullstrand-type model eye was used for this study. The axial length of the model eye was set to different values ranging from 20 to 31 mm, and the light fluence rate for treating a spot of 4 mm was recorded and compared with a fluence rate of 600 mW/cm2 with four indirect condensing laser lenses. RESULTS: The axial length of the eye is inversely related to light fluence. From myopia to hyperopia, the total deviation from 600 mW/cm2 was -37.7% to +53.8% (Mainster Standard; Ocular Instruments Inc, Bellevue, Washington, USA), and -48.3% to +20.5% (Mainster Wide Field; Ocular Instruments Inc), -52.3% to +16.7% (Volk Transequator; Volk Optical Inc, Mentor, Ohio, USA), and -52.3% to +15.3% (Volk PDT Laser; Volk Optical Inc). CONCLUSIONS: Axial length of the eye has a considerable effect on PDT light fluence rate in this model. These findings may be important for optimizing PDT, particularly in eyes with high refractive errors.     

The Limulus-eye view of the world.

The compound lateral eye of the adult horseshoe crab, Limulus polyphemus, views the world with approximately 1000 ommatidia. Their optical properties and orientation determine the eye's resolution, field of view, and light collecting ability. Optic axes of adjacent ommatidia diverge from 1-15 deg with an average value of 5.5 deg yielding an average resolution of 0.1 cycles/deg. Resolution is not uniform across the eye: along horizontal planes, it is maximal in the anterior region of the eye (0.22 cycle/deg) and minimal in the posterior region (0.07 cycle/deg); along vertical planes, it is maximal near or just below the horizon (0.23 cycle/deg) and minimal above the horizon (0.04 cycle/deg). Together the ommatidia of one eye view approximately 60% of the hemispheric world on one side of the body. There is little binocular overlap (< 1% of total field). Ommatidial facets of up to 320 microns in diameter (among the largest known in the animal kingdom) make the eye a superb light collector. Limulus are known to use vision to find mates both day and night. Apparently, the optics of the lateral eye sample a large enough part of the world with sufficient resolution and light-collecting ability for the animal to succeed at this essential task.     

Tear evaporimeter for measuring water evaporation rate from the tear film under controlled conditions in humans

The rate of water evaporation from the tear film depends on the conditions under which it is determined. If measured in a controlled and easily reproducible setting, tear evaporation rate could serve as a useful diagnostic and research tool. We have developed a tear evaporimeter that provides a non-invasive method for evaluating water evaporation rate in eyes with normal or pathologic tear films. The subject is fitted with a pair of swimmer's goggles modified so that the air over the test eye is conditioned to a desired baseline of relative humidity (29·5%) and temperature (23 ± 1°C). To eliminate other sources of water, the lids and skin under the goggles are covered with petroleum jelly. The subject is asked to keep his/her eye open and to avoid blinking during the 1-min test. The increase in relative humidity due to water evaporation from the tears is then determined. The surface area of the eye exposed to evaporation is calculated from the lid aperture.We measured the water evaporation rate in 52 normal eyes (average = 4·07 × 10^?7 ± 0·40 × 10^?7 g/cm²/sec) and compared the results with values obtained in 52 eyes with various tear-film abnormalities (average = 8·17 × 10^?7 ± 2·65 × 10^?7 g/cm²/sec). The difference between the two groups is statistically significant (P < 0·01). In normal eyes, after the instillation of one drop of 0·5% proparacaine, the increase in evaporation rate was statistically significant.     

特发性眼眶炎性假瘤治疗的远期随访观察

目的:探讨特发性眶内炎性假瘤药物联合手术治疗的远期效果。方法:回顾分析1986/2006年88例92眼住院患者,其中药物联合手术治疗的患者68例80眼,单纯药物治疗的患者20例,随访时间1～14(平均4.4)a。结果:患者88例中,男50例,女38例,右眼51例,左眼33例,双眼4例,年龄2.5～80(平均31.4)岁。其主要临床表现和体征有:眼球突出76例,前部眶间隙可触到肿块64例,眼睑浮肿伴眼部疼痛34例,眼球运动受限伴复视33例,眼外肌肥厚23例。其它:视神经增粗,脂肪垫水肿,眼环增厚等表现共27例,有68例经药物+手术+药物联合治疗。余20例单纯药物治疗,经随访完全治愈43例,部分治愈34例,复发11例,有效率88%。结论:表现有眶内实性包块的眶内炎性假瘤,采取药物联合手术方法综合治疗可明显提高此病的治愈率。     

The development of visual pursuit during the first months of life

· Background: There are few previous investigations of smooth pursuit in infants. The aim of our study was to quantify visual pursuit in infants between 1 day and 16 weeks of age. · Methods: Eye movements of 97 healthy infants between 1 day and 16 weeks of age were recorded one to seven times with infrared photo-oculography. For stimulation of visual pursuit a square of 9.4 deg of visual angle with vertical gratings moved horizontally at a constant velocity of 7.5 deg/s. · Results: In the first 2 weeks of life, segments of smooth pursuit were measured with a maximum velocity of 7.93 deg/s, with a maximum gain of 1.06 and a maximal duration of 3.16 s. In sequential recordings no significant increases of velocity, gain or duration were found. However, the total time the subjects followed the stimulus with smooth plus saccadic pursuit increased significantly with age (from a median of 39.0% to a median of 61.5% of examination time). · Conclusion: This study clearly demonstrates that smooth pursuit is already present in the first week of life. We found no significant increase in velocity, gain and duration of smooth pursuit segments in the first 16 weeks of life with our recording technique. However, the total pursuit time, reflecting attention, increased with age. The ocular machinery to drive pursuit appears to be in place at birth and seems not to be influenced by increased attention in the first months of life. Received: 23 June 1997 Revised version received: 14 August 1997 Accepted: 1 October 1997     

Effect of myopia on visual acuity measured with laser interference fringes

The aim was to determine how visual acuity is affected by myopia when optical factors of the eye are controlled. Grating acuity was measured with interference fringes to avoid the effects of aberrations, and ocular biometry was used to compensate for differences in retinal image size among subjects. Distance spectacle refractions ranged from +2.25 to -14.75 D. The retinal magnification factor (RMF) in mm/deg was computed for each eye from the distance refraction, central corneal power and ultrasound biometry. A forced-choice orientation discrimination method was used to measure acuity for high-contrast 543 nm laser interference fringes in three retinal locations: the fovea, and at 4 deg and 10 deg eccentricity in the temporal retina. Acuity, expressed in c/deg and adjusted for spectacle magnification, was not significantly correlated with refraction at any of the three retinal locations. When acuity was converted to retinal spatial frequency units (c/mm) via the RMF, acuity decreased with increasing myopia at all three retinal locations (significantly at the fovea and at 10 deg eccentricity). Retinal acuity values in highly myopic subjects (>6 D) are consistent with retinal sampling distances that are larger than published values of human cone or ganglion cell spacing. The results imply that a highly myopic eye has retinal neurons that are more widely spaced than normal, but the increased axial length enlarges the retinal image enough to compensate for the retinal stretching. The data are consistent with a retinal stretching model that primarily affects the posterior pole.