scholarly journals Estimation of Line Orientation Depends on the Set of Additional Images

2021 ◽  
Vol 14 (1) ◽  
pp. 64-79
Author(s):  
V.N. Chikhman ◽  
V.M. Bondarko
Keyword(s):  
Visual Acuity ◽  
Receptive Fields ◽  
Line Orientation ◽  
Tilt Illusion ◽  
The Difference

The orientation of the lines, to which additional inclined lines could adjoin, was estimated. We have found a distortion in estimation of lines orientation by 1—2° (tilt illusion) when additional lines were presented, depending on a set of additional lines. For different observers, in the case of the presence of additional lines with a difference in orientation between the lines of up to 12°, both the effect of attraction (the lines seemed to be turned towards the additional) and the effect of repulsion could be detected. With a larger difference, only the repulsive effect is revealed. The discrepancy in the dependences can be explained by the difference in the visual acuity of observers associated with the size of the smallest receptive fields of striatal cortex neurons

Comparison of the Effectiveness of Intravitreal Ranibizumab for Diabetic Macular Edema in Vitrectomized and Nonvitrectomized Eyes

2016 ◽  
Vol 236 (2) ◽  
pp. 67-73 ◽  
Author(s):  
Yoshito Koyanagi ◽  
Shigeo Yoshida ◽  
Yoshiyuki Kobayashi ◽  
Yuki Kubo ◽  
Muneo Yamaguchi ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Macular Edema ◽  
Diabetic Macular Edema ◽  
Treatment Option ◽  
Central Macular Thickness ◽  
Intravitreal Ranibizumab ◽  
Corrected Visual Acuity ◽  
The Mean ◽  
The Difference ◽  
Best Corrected Visual Acuity

Purpose: To compare the effectiveness of intravitreal ranibizumab (IVR) for diabetic macular edema (DME) between eyes with and without previous vitrectomy. Procedures: We prospectively assessed the best-corrected visual acuity (BCVA) and central macular thickness (CMT) after IVR for 6 months. Results: There were no significant differences in the baseline BCVA and CMT between both groups. In the nonvitrectomized group (n = 15), the mean changes of BCVA and CMT from baseline to month 6 were significant (p < 0.01). In the vitrectomized group (n = 10), the improvement appeared to be slower, and the mean BCVA improvement was not significant (p = 0.5), although the mean CMT decrease was significant (p < 0.05). There were no significant differences in the mean changes of BCVA and CMT between both groups at 6 months. Conclusions: The difference in the effectiveness of IVR between both groups was not significant. IVR can be a treatment option even for vitrectomized DME eyes.

scholarly journals Outcomes of Femtosecond Laser Assisted Cataract Surgery Performed by Resident and Attending Surgeons

2021 ◽  
Vol 13 (01) ◽  
pp. e26-e31
Author(s):  
Spencer C. Cleland ◽  
Daniel W. Knoch ◽  
Jennifer C. Larson
Keyword(s):  
Visual Acuity ◽  
Femtosecond Laser ◽  
Cataract Surgery ◽  
Retrospective Chart Review ◽  
Dissipated Energy ◽  
Independent Practice ◽  
Postoperative Visual Acuity ◽  
Included Patient ◽  
Duration Of Surgery ◽  
The Difference

Abstract Objective The study aimed to evaluate the safety and efficacy of resident surgeons performing femtosecond laser assisted cataract surgery (FLACS). Methods A retrospective chart review was conducted at the University of Wisconsin-Madison from postgraduate year four residents performing FLACS between 2017 and 2019. Data were also collected from residents performing manual cataract surgery, and attending surgeons performing FLACS for comparison. Recorded data included patient demographics, pre- and postoperative visual acuity, pre- and postoperative spherical equivalent, nuclear sclerotic cataract grade, ocular and systemic comorbidities, intraocular lens, duration of surgery, cumulative dissipated energy (CDE), and intraoperative and postoperative complications. Results A total of 90 cases were reviewed with 30 resident manual cases, 30 resident FLACS cases, and 30 attending FLACS cases. Resident manual (25.5 ± 6.8 minutes) and resident FLACS (17.5 ± 7.1 minutes) cases took a significantly longer time to complete compared with attending FLACS cases (13.6 ± 4.4 minutes; p < 0.001). There was higher CDE in resident FLACS and resident manual cases compared with attending FLACS cases, but the difference was not statistically significant (p = 0.06). Postoperative visual acuity was not statistically different at 1-day and 1-month after surgery among the three groups. Resident FLACS complications, which included one case requiring an intraoperative suture to close the wound, two cases with intraoperative corneal abrasions, two cases with postoperative ocular hypertension, and one case with cystoid macular edema, were not significantly greater than attending FLACS complications (p = 0.30). Conclusion The FLACS performed by resident surgeons had comparable visual acuity outcomes to FLACS performed by attending surgeons, and to manual cataract surgery performed by resident surgeons. However, resident FLACS cases took significantly longer time to complete, and they were associated with a higher CDE and minor complication rate compared with attending FLACS cases. Introducing advanced technologies into surgical training curricula improves resident preparedness for independent practice, and this study suggests FLACS can be incorporated safely and effectively into resident education.

scholarly journals Visual performance in behaving cats after prenatal unilateral enucleation

1993 ◽  
Vol 90 (23) ◽  
pp. 11142-11146 ◽  
Author(s):  
S Bisti ◽  
C Trimarchi
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
Receptive Field ◽  
Receptive Fields ◽  
Direction Selectivity ◽  
Visual Performance ◽  
Field Size ◽  
Electrophysiological Recordings ◽  
Severe Impairment ◽  
Orientation Columns

Prenatal unilateral enucleation in mammals causes an extensive anatomical reorganization of visual pathways. The remaining eye innervates the entire extent of visual subcortical and cortical areas. Electrophysiological recordings have shown that the retino-geniculate connections are retinotopically organized and geniculate neurones have normal receptive field properties. In area 17 all neurons respond to stimulation of the remaining eye and retinotopy, orientation columns, and direction selectivity are maintained. The only detectable change is a reduction in receptive field size. Are these changes reflected in the visual behavior? We studied visual performance in cats unilaterally enucleated 3 weeks before birth (gestational age at enucleation, 39-42 days). We tested behaviorally the development of visual acuity and, in the adult, the extension of the visual field and the contrast sensitivity. We found no difference between prenatal monocularly enucleated cats and controls in their ability to orient to targets in different positions of the visual field or in their visual acuity (at any age). The major difference between enucleated and control animals was in contrast sensitivity:prenatal enucleated cats present a loss in sensitivity for gratings of low spatial frequency (below 0.5 cycle per degree) as well as a slight increase in sensitivity at middle frequencies. We conclude that prenatal unilateral enucleation causes a selective change in the spatial performance of the remaining eye. We suggest that this change is the result of a reduction in the number of neurones with large receptive fields, possibly due to a severe impairment of the Y system.

Responses of Medullary Dorsal Horn Neurons to Corneal Stimulation by CO2 Pulses in the Rat

1999 ◽  
Vol 82 (5) ◽  
pp. 2092-2107 ◽  
Author(s):  
Harumitsu Hirata ◽  
James W. Hu ◽  
David A. Bereiter
Keyword(s):  
Thalamic Nucleus ◽  
Receptive Fields ◽  
Male Rats ◽  
Cervical Cord ◽  
Type I ◽  
Type Ii ◽  
Upper Cervical ◽  
The Difference ◽  
Evoked Activity ◽  
Stimulation Of

Corneal-responsive neurons were recorded extracellularly in two regions of the spinal trigeminal nucleus, subnucleus interpolaris/caudalis (Vi/Vc) and subnucleus caudalis/upper cervical cord (Vc/C1) transition regions, from methohexital-anesthetized male rats. Thirty-nine Vi/Vc and 26 Vc/C1 neurons that responded to mechanical and electrical stimulation of the cornea were examined for convergent cutaneous receptive fields, responses to natural stimulation of the corneal surface by CO2 pulses (0, 30, 60, 80, and 95%), effects of morphine, and projections to the contralateral thalamus. Forty-six percent of mechanically sensitive Vi/Vc neurons and 58% of Vc/C1 neurons were excited by CO2 stimulation. The evoked activity of most cells occurred at 60% CO2 after a delay of 7–22 s. At the Vi/Vc transition three response patterns were seen. Type I cells ( n = 11) displayed an increase in activity with increasing CO2 concentration. Type II cells ( n = 7) displayed a biphasic response, an initial inhibition followed by excitation in which the magnitude of the excitatory phase was dependent on CO2 concentration. A third category of Vi/Vc cells (type III, n = 3) responded to CO2 pulses only after morphine administration (>1.0 mg/kg). At the Vc/C1 transition, all CO2-responsive cells ( n = 15) displayed an increase in firing rates with greater CO2 concentration, similar to the pattern of type I Vi/Vc cells. Comparisons of the effects of CO2 pulses on Vi/Vc type I units, Vi/Vc type II units, and Vc/C1 corneal units revealed no significant differences in threshold intensity, stimulus encoding, or latency to sustained firing. Morphine (0.5–3.5 mg/kg iv) enhanced the CO2-evoked activity of 50% of Vi/Vc neurons tested, whereas all Vc/C1 cells were inhibited in a dose-dependent, naloxone-reversible manner. Stimulation of the contralateral posterior thalamic nucleus antidromically activated 37% of Vc/C1 corneal units; however, no effective sites were found within the ventral posteromedial thalamic nucleus or nucleus submedius. None of the Vi/Vc corneal units tested were antidromically activated from sites within these thalamic regions. Corneal-responsive neurons in the Vi/Vc and Vc/C1 regions likely serve different functions in ocular nociception, a conclusion reflected more by the difference in sensitivity to analgesic drugs and efferent projection targets than by the CO2 stimulus intensity encoding functions. Collectively, the properties of Vc/C1 corneal neurons were consistent with a role in the sensory-discriminative aspects of ocular pain due to chemical irritation. The unique and heterogeneous properties of Vi/Vc corneal neurons suggested involvement in more specialized ocular functions such as reflex control of tear formation or eye blinks or recruitment of antinociceptive control pathways.

scholarly journals The effect of amblyopia on clinical outcomes of children with astigmatism

2021 ◽  
Vol 13 ◽  
pp. 251584142110408
Author(s):  
Burçin Çakır ◽  
Nilgün Özkan Aksoy ◽  
Sedat Özmen ◽  
Özlem Bursalı
Keyword(s):  
Visual Acuity ◽  
Clinical Outcomes ◽  
Medical Records ◽  
Convergence Insufficiency ◽  
Corrected Visual Acuity ◽  
Ocular Deviation ◽  
The Mean ◽  
The Difference ◽  
Best Corrected Visual Acuity

Background: Amblyopia is more common in children with high astigmatism, but factors contributing to development of amblyopia and visual outcomes are not fully understood. Objective: To evaluate the effect of amblyopia on the clinical outcomes in children with ⩾1.75 diopter (D) astigmatism. Methods: We reviewed the medical records of children with ⩾1.75 D astigmatism with and without amblyopia (amblyopes group and non-amblyopes group). The mean age, gender, amount and type of ocular deviation, presence of convergence insufficiency (CI), stereopsis, time of initial spectacle use and follow-up time, differences in best-corrected visual acuity (VoD) and spherical equivalent (SE) between eyes were assessed and compared between the groups. Best-corrected visual acuity (BCVA), mean SE, astigmatism measurements were assessed and compared between amblyopic, fellow, and non-amblyopic eyes. Results: The records included 68 eyes of 34 children with amblyopia and 56 eyes of 28 children without amblyopia. The mean age, gender, amount and type of ocular deviation, presence of CI, stereopsis, time of initial spectacle use, follow-up time, and the difference in SE did not differ between groups. In amblyopes, exodeviation was more common and statistically greater in near (33 cm) than at distance (6 m) (p = 0.005). The mean BCVA and astigmatism values were statistically different between amblyopic, fellow, and non-amblyopic eyes. Conclusion: A greater near than distance exodeviation and higher mean astigmatism value were found in amblyopic children with astigmatism.

Diurnal changes in retinula cell sensitivities and receptive fields (two-dimensional angular sensitivity functions) in the apposition eyes of Ligia exotica (Crustacea, Isopoda)

2001 ◽  
Vol 204 (2) ◽  
pp. 239-248 ◽  
Author(s):  
T. Hariyama ◽  
V.B. Meyer-Rochow ◽  
T. Kawauchi ◽  
Y. Takaku ◽  
Y. Tsukahara
Keyword(s):  
Receptive Fields ◽  
Resolving Power ◽  
Pigment Cells ◽  
Diurnal Changes ◽  
Two Dimensional ◽  
Angular Sensitivity ◽  
Pigment Granules ◽  
Screening Pigment ◽  
The Difference ◽  
Night And Day

The structural organization of the retinula cells in the eye of Ligia exotica changes diurnally. At night, the microvilli elongate, losing the regular and parallel alignment characteristic of the day condition. Crystalline cones and distal rhabdom tips are not pushed into each other during the day, but at night the rhabdoms protrude into the crystalline cones by up to 5 microm. Screening pigment granules in the retinula cells disperse during the night, but migrate radially towards the vicinity of the rhabdom during the day. No such displacements of the pigment granules of either distal or proximal screening pigment cells were observed. The sensitivity of the eye, monitored by electroretinogram (ERG) recordings, changes diurnally: values at midnight are, on average, 10 times those occurring during the day. However, intracellular recordings from single retinula cells (50 during the day and 50 at night) indicate that the difference between night and day sensitivities is only 2.5-fold. Two-dimensional angular sensitivity curves, indicative of a single unit's spatial sensitivity, had considerably less regular outlines at night than during the day. If based on the 50 % sensitivity level, day and night eyes possessed receptive fields of almost identical width (approximately 2 degrees), but if sensitivities below the 50 % limit were included, then receptive fields at night were significantly more extensive. We suggest that the morphological adaptations and diurnal changes in chromophore content seen in the apposition eye of L. exotica allow this animal to improve its photon capture at night while preserving at least some of the spatial resolving power characteristic of the light-adapted state. This would explain why this animal is capable of performing complex escape behaviours in the presence of predators both in bright and in very dim light.

Recovery of function in dorsal horn following partial deafferentation

1980 ◽  
Vol 43 (1) ◽  
pp. 102-117 ◽  
Author(s):  
L. M. Pubols ◽  
M. E. Goldberger
Keyword(s):  
Dorsal Horn ◽  
Recovery Of Function ◽  
Receptive Fields ◽  
Body Region ◽  
Partial Recovery ◽  
Collateral Sprouting ◽  
Somatotopic Organization ◽  
Tactile Input ◽  
Spinal Cord Segment ◽  
The Difference

1. Collateral sprouting of L6 dorsal root afferents within the dorsal horn of the L6 spinal cord segment has been shown anatomically to occur following transection of all other lumbosacral dorsal roots in the cat. The present study was performed to examine a possible physiological correlate of that sprouting, namely, an altered somatotopic organization of the dorsal horn at L6. This was evaluated by microelectrode mapping of the L6 dorsal horn in normal cats and in cats with L6 spared, lumbosacral dorsal rhizotomies performed 2 days (subacute spared root) or more than 8 wk (chronic spared root), prior to recording. 2. In normal cats the mediolateral somatotopic sequence of hindlimb representation in the L6 dorsal horn is ventral digits 2 and 3, dorsal digits 2 and 3, dorsal foot, rostral and lateral ankle, lateral leg, lateral thigh, and back. In both subacute and chronic spared-root cats the somatotopic sequence is similar to that of normal cats, but there is a loss of proximal thigh and back representation. This proximal body region is represented at the lateral edge of the dorsal horn in normal animals. 3. There was a partial loss of responsiveness of cells in the dorsal horn in the subacute spared-root group and a partial recovery of responsiveness in the chronic group. In the subacute group punctures exhibiting no responses to tactile input tended to be clustered in the lateral dorsal horn. 4. The lateral one-fourth of the dorsal horn in each animal was analyzed in terms of the percentage of recording loci occurring within it. The percentages of recording loci having receptive fields proximal to, distal to, and spanning the middle of the thigh (proximal, distal, and intermediate RFs) were tabulated for each animal. Subacute animals had a significantly lower-than-normal overall percentage of responsive loci in the lateral dorsal horn, but chronic animals did not. The percentage of distal fields therein was not different for the normal versus the subacute group, signifying that the loss of proximal and intermediate fields was responsible for the difference in overall percentage. Chronic animals, however, had significantly more distal fields than did normals. When all fields having any distal component were compared (i.e., distal and intermediate), the difference between the chronic and normal groups did not reach significance. One possible explanation of these findings is that loci having both proximal and distal RF components are unresponsive 2 days after partial denervation, but recover responsiveness to their spared distal input over an 8-wk period. One possible mechanism mediating these changes is localized sprouting of intact, spared axons. Other mechanisms of functional recovery, such as interneuronal sprouting, denervation supersensitivity, and unmasking of latent synapses, are discussed in relation to these and other data.

Visual response properties of neurons in four extrastriate visual areas of the owl monkey (Aotus trivirgatus): a quantitative comparison of medial, dorsomedial, dorsolateral, and middle temporal areas

1981 ◽  
Vol 45 (3) ◽  
pp. 397-416 ◽  
Author(s):  
J. F. Baker ◽  
S. E. Petersen ◽  
W. T. Newsome ◽  
J. M. Allman
Keyword(s):  
Receptive Fields ◽  
Field Size ◽  
Visual Response ◽  
Response Properties ◽  
Middle Temporal ◽  
Optimal Direction ◽  
Visual Areas ◽  
Direction Of Movement ◽  
Owl Monkeys ◽  
The Difference

1. The response properties of 354 single neurons in the medial (M), dorsomedial (DM), dorsolateral (DL), and middle temporal (MT) visual areas were studied quantitatively with bar, spot, and random-dot stimuli in chronically implanted owl monkeys with fixed gaze. 2. A directionality index was computed to compare the responses to stimuli in the optimal direction with the responses to the opposing direction of movement. The greater the difference between opposing directions, the higher the index. MT cells had much higher direction indices to moving bars than cells in DL, DM, and M. 3. A tuning index was computed for each cell to compare the responses to bars moving in the optimal direction, or flashed in the optimal orientation, with the responses in other directions or orientations within +/- 90 degrees. Cells in all four areas were more sharply tuned to the orientation of stationary flashed bars than to moving bars, although a few cells (9/92( were unresponsive in the absence of movement. DM cells tended to be more sharply tuned to moving bars than cells in the other areas. 4. Directionality in DM, DL, and MT was relatively unaffected by the use of single-spot stimuli instead of bars; tuning in all four areas was broader to spots than bars. 5. Moving arrays of randomly spaced spots were more strongly excitatory than bar stimuli for many neurons in MT (16/31 cells). These random-dot stimuli were also effective in M, but evoked no response or weak responses from most cells in DM and DL. 6. The best velocities of movement were usually in the range of 10-100 degrees/s, although a few cells (22/227), primarily in MT (14/69 cells), preferred higher velocities. 7. Receptive fields of neurons in all four areas were much larger than striate receptive fields. Eccentricity was positively correlated with receptive-field size (r = 0.62), but was not correlated with directionality index, tuning index, or best velocity. 8. The results support the hypothesis that there are specializations of function among the cortical visual areas.

Prospective analysis of visual function changes in patients with dermatochalasis after upper eyelid blepharoplasty

2019 ◽  
Vol 30 (5) ◽  
pp. 978-984
Author(s):  
Meryem Altin Ekin ◽  
Seyda Karadeniz Ugurlu
Keyword(s):  
Visual Acuity ◽  
Contrast Sensitivity ◽  
Visual Function ◽  
Spherical Aberration ◽  
Higher Order ◽  
Rank Test ◽  
Higher Order Aberrations ◽  
Upper Eyelid ◽  
Spatial Frequencies ◽  
The Difference

Objective: To evaluate the changes of visual acuity, contrast sensitivity, astigmatism, and higher order aberrations after blepharoplasty in patients with dermatochalasis. Methods: Two hundred six eyelids of 103 patients with dermatochalasis were prospectively studied. Visual acuity, contrast sensitivity, corneal topography, astigmatism degree, and higher order aberrations were examined and recorded before and at 1 month after upper eyelid blepharoplasty. Change in contrast sensitivity and astigmatism values were determined according to margin reflex distance of patients, which were classified into three following groups: <2 mm, 2–3 mm, and ⩾ 4 mm. A Wilcoxon signed rank test was performed to compare the difference. Results: No significant differences were observed for visual acuity (p = 0.157). The contrast sensitivity of patients significantly increased at all spatial frequencies both under glare and nonglare conditions (p < 0.05). The mean refractive astigmatism significantly decreased from ‒1.01 ± 1.3 to ‒0.79 ± 0.71, postoperatively (p = 0.029). In patients with marginal reflex distance < 2 mm, mean contrast sensitivity was increased (p < 0.001) and mean astigmatism was decreased significantly (p < 0.001) compared with those with ⩾ 2 mm. Higher order aberrations decreased significantly from 0.62 ± 0.41 µm to 0.55 ± 0.38 µm (p = 0.038) after blepharoplasty. Root mean square of the vertical trefoil (p = 0.038), vertical coma (p = 0.002), horizontal trefoil (p = 0.027), third-order aberration (p = 0.005), secondary vertical stigmatism (p = 0.001), spherical aberration (p = 0.023), secondary horizontal astigmatism (p = 0.002), fourth-order aberration (p = 0.024), vertical pentafoil (p = 0.015), secondary horizontal coma (p = 0.035), secondary horizontal trefoil (p = 0.030), and horizontal pentafoil (p = 0.048) were decreased significantly. Conclusion: Upper eyelid blepharoplasty in patients with dermatochalasis has a significant improvement in visual function in terms of contrast sensitivity, astigmatism, and higher order aberrations.

Changes in Visual Acuity and Refraction in the Exfoliation Syndrome. A Five-Year Follow-up Study

2001 ◽  
Vol 11 (3) ◽  
pp. 245-251 ◽  
Author(s):  
P.M. Puska ◽  
A.H.A. Tarkkanen
Keyword(s):  
Visual Acuity ◽  
Main Type ◽  
Exfoliation Syndrome ◽  
Follow Up Study ◽  
Exfoliative Glaucoma ◽  
The Difference ◽  
Term Management ◽  
Fellow Eyes

Purpose To examine changes in visual acuity (VA) and refraction in non-glaucomatous patients with unilateral exfoliation syndrome (EXS). Methods The best corrected values for VA (Snellen acuity cards) subjectively adjusted for refraction, and IOP were measured, and the development of lens opacities was examined in 46 non-glaucomatous patients with unilateral EXS. Results After five years the rate of conversion to bilateral exfoliation was 22% and to exfoliative glaucoma 30%. There was a significant decrease in VA in the exfoliative (E) eyes (median; QI, QIII, range: 1; 0.8, 1, 0.4-1.3 vs. 0.55; 0.4, 1, 0.05-1.4, p<0.0001) and the fellow, initially non-exfoliative (NE), eyes (1; 0.9, 1, 0.3–1.3 vs. 0.7; 0.5, 0.9, 0.1–1.4, p<0.0001) and a significant myopic change in refraction in the E eyes (+1.02 ± 2.48 vs. +0.11 ± 3.06, p=0.0001) and the NE eyes (+0.99 ± 2.25 vs. +0.43 ± 2.55 D, p<0.01). At study entry the difference in refraction between the fellow eyes (refraction in the NE eye – refraction in the E eye) was −0.27 ± 1.00D. After five years it was +0.32 ± 1.44 (p 0.016), reflecting greater myopic changes in the E eyes. The main type of lens opacification was nuclear sclerosis. Conclusions In five years, significant decreases in VA and myopic shifts in refraction occurred in the E and fellow eyes. The E eyes showed significantly greater myopic changes than the fellow eyes; the cause was clearly nuclear sclerosis, which must be taken into account in the long-term management of patients with EXS.

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