Cortical Deficits are Correlated with Impaired Stereopsis in Patients with Strabismus

In this study,we explored the neural mechanism underlying impaired stereopsis and possible functional plasticity after strabismus surgery.We enrolled 18 stereo-deficient patients with intermittent exotropia before and after surgery,along with 18 healthy controls.Functional magnetic resonance imaging data were collected when participants viewed three-dimensional stimuli.Compared with controls,preoperative patients showed hypoactivation in higher-level dorsal(visual and parietal)areas and ventral visual areas.Pre-and postoperative activation did not significantly differ in patients overall;patients with improved stereopsis showed stronger postoperative activation than preoperative activation in the right V3A and left intraparietal sulcus.Worse stereopsis and fusional control were correlated with preoperative hypoactivation,suggesting that cortical deficits along the two streams might reflect impaired stereopsis in intermittent exotropia.The correlation between improved stereopsis and activation in the right V3A after surgery indicates that functional plasticity may underlie the improvement of stereopsis.Thus,additional postoperative strategies are needed to promote functional plasticity and enhance the recovery of stereopsis.

Stereopsis after bilateral implantation of Toric intraocular lenses in high myopic cataract patients with astigmatism

Purpose:To evaluate near,intermediate,distance visual acuity and stereopsis after bilateral implantation of Toric intraocular lenses(IOLs)in high myopic patients with astigmatism.Methods:Bilateral Toric or non-Toric IOL implantation(n¼40 eyes each)was performed on high myopic cataract eyes with astigmatism.Best-corrected distance visual acuity(BCDVA),uncorrected intermediate visual acuity(UCIVA),uncorrected near visual acuity(UCNVA),residual refractive astigmatism(RRA),and near,intermediate,and distance stereoacuity were measured postoperatively at 7 days,1 month,and 3 months.Results:The three-month postoperative BCDVA,UCIVA,and UCNVA of the Toric group were 0.08±0.07,0.30±0.11,and 0.23±0.14 LogMAR.All improved over the preoperative assessments(P<0.05).The RRA,UCIVA,and UCNVA were significantly better in the Toric group than the non-Toric group at all follow-up examinations(all P<0.05).At 3 months,the median near and intermediate stereoacuity of the Toric group were 100(range 40–400)and 120(range 50–400)arcsec,which were better than the non-Toric group(both P<0.05).Fine near stereopsis100 arcsec was present in 65%of the Toric patients,and 50%had good intermediate stereopsis of100 arcsec.However among non-Toric patients,only 15%and 5%achieved fine near and intermediate stereopsis.The postoperative BCDVA and best-corrected distance stereoacuity were similar in the two groups(P>0.05).Conclusions:In bilateral high myopic cataract patients with astigmatism,Toric IOLs not only improved UCIVA,UCNVA,and RRA,but also enhanced near and intermediate stereopsis acuity.

Assessment of the effects of induced anisometropia on binocularity with glasses-free 3D technique

AIM:To assess the effect of experimentally induced anisometropia on binocularity in normal adults with glassesfree three-dimensional(3D)technique.METHODS:Totally 54 healthy medical students with normal binocularity in the cross-sectional study were enrolled.Anisometropia was induced by placing trail lenses over the right eye,in 0.5 D steps including lenses of-0.5,-1,-1.5,-2,-2.5 D(hyperopic anisometropia)and lenses of+0.5,+1,+1.5,+2,+2.5 D(myopic anisometropia).The glasses-free 3D technique was used to evaluated not only fine stereopsis,but also coarse stereopsis,dynamic stereopsis,foveal suppression,and peripheral suppression in these subjects.One-way analysis of variance was used to compare quantitative data such as fine stereopsis,coarse stereopsis.Pearson’s Chi-square test was performed to compare categorical data such as dynamic stereopsis,foveal suppression and peripheral suppression.RESULTS:The subjects showed a statistically significant decline in fine stereopsis,coarse stereopsis,and dynamic stereopsis with increasing levels of anisometropia(P<0.001).Binocularity was af fected when induced anisometropia was more than 1 D(P<0.05).Foveal suppression and peripheral suppression were evident and increased in proportion to anisometropia(P<0.001).CONCLUSION:The relatively low degrees of anisometropia may have a potentially significant effect on high-grade binocular interaction.The mechanisms underlying the defect of binocularity seem to involve not only foveal suppression,but also peripheral suppression.

Effect of changing mesopic and photopic light conditions on visual functions

AIM:To determine the effects of change in light conditions on refractive error and visual functions including visual acuity,stereopsis and contrast sensitivity.METHODS:This cross-sectional study was conducted in the optometry clinic of the Shahid Beheshti School of Rehabilitation on 48 students in 2021-2022.All of them had eye health and normal visual function and could have refractive errors or not.Light intensity of 4 lx was considered equivalent to photopic light condition and light intensity of 1 lx was considered to be equivalent to mesopic light condition.The amount of refractive error was checked by auto refractometer and its changes in mesopic light condition were subjectively measured.Also,visual acuity,stereopsis and contrast sensitivity(in five spatial frequencies of 1.5,3,6,12,and 18 cycles per degree),were measured first in photopic light condition and then in mesopic light condition,by Snellen control vision chart,stereo butterfly test and the M&S technology monitor test respectively.RESULTS:In the 48 student subjects with an average age of 22.69±3.56y,mean of refractive error as sphere equivalent,visual acuity and stereopsis were-1.25±1.74 diopters,0 logMAR,44.37±13.03 seconds of arc,respectively in photopic light condition while in mesopic light was equal to-1.56±1.75 diopters,0.12±0.09 logMAR and 50.62±33.35 seconds of arc,respectively.The mean of contrast sensitivity measured at spatial frequencies of 1.5,3,6,12,and 18 cycles per degree in photopic condition was equal to 2.38±0.04,2.37±0.07,2.04±0.21,1.27±0.32,0.82±0.27 logarithm of contrast sensitivity,respectively and in mesopic lighting condition was equal to 2.34±0.12,2.30±0.16,1.84±0.28,1.02±0.28,0.63±0.24 logarithm of contrast sensitivity,respectively.Statistical analysis showed a significant difference between the two lighting conditions in all evaluated variables[refractive error(P<0.001),visual acuity(P<0.001),stereopsis(P=0.008)and contrast sensitivity(P<0.001)].CONCLUSION:The refractive error of the student subjects in mesopic light condition change towards myopia,and its amount is clinically significant.Also,the examination and comparison of the factors of visual acuity,stereopsis and contrast sensitivity in these two lighting conditions show that the decrease in brightness level to the mesopic level causes a decrease in the aforementioned visual functions.

在以前未经治疗的 anisometropic 弱视的屈光参差症大小和视觉赤字

AIM:To assess the quantitative association between anisometropia magnitude(AM) and the losses of resolution and contrast sensitivity;and to exemplify how the function of fusion and stereopsis vary with AM in previously untreated anisometropic amblyopia. METHODS:A total of 57 patients with previously untreated anisometropic amblyopia without strabismus(range:8-35 years),were measured refractive error,best corrected visual acuity(BCVA),fusion and stereopsis,and 48 patients have completed contrast sensitivity function test.AM was determined by dioptric vector addition model,and the amblyopia depth was determined by the difference of BCVA in logMAR units between the amblyopic and fellow eyes.RESULTS:AM was significantly correlated with both amblyopia depth(Pearson R=0.728,P【0.001) and the inter-ocular difference of the area under the log contrast sensitivity function(AULCSF)(R=0.505,P【0.001).Depth of amblyopia and the inter-ocular difference of AULCSF was also significantly correlated(R=0.761,P【0.001).The more severity of amblyopia,the poorer levels of contrast sensitivity.Most pure anisometropes with AM was less than 3.0D retain fusion and some stereopsis,but when AM were more than 3.0D,especially for the anisometropes whose AM was more than 6.0D,fusion and stereopsis function were seriously impaired.CONCLUSION:In the patients with previously untreated anisometropic amblyopia,higher degree of anisometropia is significantly associated with deeper amblyopia,worse contrast sensitivity,fusion and stereopsis functions.

Comparison of trifocal toric and bifocal toric intraocular lens implantation in patients with cataract and high corneal astigmatism

AIM:To investigate and compare the quality of life,satisfaction,contrast sensitivity,glare,depth perception,and intraocular lens(IOL)rotation in patients who underwent trifocal toric and bifocal toric IOLs.METHODS:A total of 80 eyes of 40 patients were included in this prospective study.Twenty patients in each group were implanted with trifocal toric and bifocal toric IOL,respectively.Preoperative and postoperative 6-month measurements were recorded for both patient groups.Comprehensive anterior and posterior segment examinations,distance-intermediate-near visual acuity values and the visual function scale questionnaire results were evaluated at these examinations.Patient satisfaction,contrast sensitivity,glare,intermediate-near and distance stereopsis and IOL rotation were also evaluated.RESULTS:No significant difference was found between the groups in terms of distance and near visual acuities(P=0.269,P=0.451).Intermediate visual acuity was significantly increased in the trifocal toric group(P<0.001).The visual function scale results were increased after surgery in both groups(P=0.001 and P<0.001),with no difference determined between them(P=0.158 and P=0.691).The number of patients wearing glasses was low in both groups and there was no significant difference between the groups(P>0.05).The overall satisfaction in the trifocal toric group was significantly higher than in the bifocal toric group(P=0.03).The highest sensitivity was observed at 6 cpd spatial frequency in all patients under photopic conditions(1.80±0.24 logU,1.74±0.20 logU).Distance-intermediate-near binocular depth perception results in both groups were higher in the trifocal toric group(P=0.02,0.048,0.003,respectively).Although there was no significant difference for 3 meters stereopsis,the trifocal toric group had higher depth perception(P=0.577).Mean rotation was 5.76°±3.93°in the trifocal toric group and 12°±7.1°in the bifocal toric group.CONCLUSION:Better results in the middle distance are obtained in the trifocal toric group and less IOL rotation due to digital system-coordinated surgery.Moreover,the overall satisfaction in the trifocal toric group is significantly higher than in the bifocal toric group.

Clinical efflcacy of botulinum toxin type A on acute acquired comitant esotropia

AIM: To investigate the effects of micro-injection of botulinum toxin A(BTXA) on acute acquired comitant esotropia(AACE). METHODS: A total of 33 AACE patients who underwent BTXA micro-injection at Renmin Hospital of Wuhan University from September 1^(st), 2019 to July 1^(st), 2021 were retrospective analyzed. Esotropia, eye alignment, stereopsis, and complications were examined at baseline(except complications), 1wk, 1, 3, and 6mo after injection. RESULTS: The average angle of deviation before injection was(+20.24±6.80)^(Δ) at near and(+24.76±6.43)^(Δ) at distance, while(+5.15±5.85)^(Δ) at near and(+7.30±6.17)^(Δ) at distance 6mo after treatment(P<0.05). Six months after injection, the stereopsis of patients had improved. The number of patients having no stereopsis(>800 seconds of arc) decreased from 11 to 3. The number of patients having peripheral stereopsis(300-800 seconds of arc), macular stereopsis(70-200 seconds of arc) and central concave stereopsis(≤60 seconds of arc) increased from 10 to 11, 10 to 12, and 2 to 7, respectively. At the follow-ups at 1wk, 1, 3, and 6mo after injection, success rates were 96.97%, 96.97%, 93.94% and 87.88%, respectively. One week after injection, two patients(6.07%) showed subconjunctival hemorrhage;three patients(9.09%) showed limited eye movement and one patient(3.03%) showed mild vertical strabismus. All the symptoms disappeared by the final follow-up.CONCLUSION: Micro-injection of BTXA can reduce diplopia and improve binocular vision function of AACE patients. Furthermore, the operation is relatively safe with few complications, making it an ideal treatment modality for AACE.

Factors influencing stereoacuity levels after surgery to correct unilateral developmental cataracts in children

AIM: To evaluate factors influencing stereoacuity after surgery to correct unilateral developmental pediatric cataracts. ·METHODS: We retrospectively surveyed 110 patients who had undergone removal of unilateral acquired developmental cataracts and primary posterior chamber intraocular lens implantation between February 1992 and December 2009. In all patients, stereoacuity was assessed using the Titmus test at the last follow -up period of minimum 2 years after surgery. Patients were divided into two groups according to the extent of stereoacuity : group 1 ( n = 42 ) had stereoacuity values ≤100sec/arc and group 2 (n =68) values >100sec/arc. The values of ten parameters associated with stereoacuity were measured in each group: Cataract types, preoperative best corrected visual acuity (BCVA) of the affected eyes, preoperative inter -ocular difference of BCVA, age at cataract surgery, operative method, secondary cataract, postoperative strabismus, postoperative BCVA of the affected eyes, postoperative inter-ocular difference of BCVA, and anisometropia. ·RESULTS: The extent of stereoacuity was significantly associated with both operative method and secondary cataract (P =0.000 and P =0.016, respectively). All patients in whom the posterior capsule was preserved, had poor stereoacuity >100sec/arc. Significant correlations with the extent of stereoacuity were found with postoperative strabismus (P =0.048),postoperative BCVA of the affected eyes (P =0.002), anisometropia (P =0.034). ·CONCLUSION: Postoperative stereoacuity was better in patients who underwent either optic capture or anteriorvitrectomy after posterior continuous curvilinear capsulorhexis, and who didn't develop secondary cataracts or strabismus postoperatively. Furthermore, postoperative BCVA of the affected eyes, and anisometropia influenced the stereoacuity of the patients surgically treated for unilateral developmental pediatric cataracts.

Depth perception on fundus images using a single-channel stereomicroscopy

Typical fundus photography produces a two-dimensional image.This makes it difficult to observe the microvascular and neural abnormalities,because the depth of the image is missing.To provide depth appreciation,we develop a single-channel stereoscopic fundus video imaging sys-tem based on a rotating refractor.With respect to the pupil center,the rotating refractor laterally displaces the optical path and the illumination.This allows standard monocular fundus cameras to generate stereo-parallax and image disparity through sequential image acquisition.We opti-mize our imaging system,characterize the stereo-base,and image an eyeball model and a rabbit eye.When virtual realities are considered,our imaging system can be a simple yet efficient technique to provide depth perception in a virtual space that allows users to perceive abnor-malities in the eye fundus.

Study of the Orthoptic Assessment in Refractive Eye Surgery

Purpose: The aim of our study was to assess the variations in fusion and stereopsis before and after refractive surgery. Methods: We conducted a retrospective study. 140 patients (78 M, 62 F) were selected, aged 20 - 59 years (mean age 36 ± 10 DS). All patients received a comprehensive ophtalmological and orthoptic examination. Surgery was performed using a MEL-80 excimer laser (Carl Zeiss Meditec, Jena, Germany). Results: Fusional convergence amplitudes after refractive eye surgery range from at near 18 - 20 PD in 42 (30%) patients;25 - 30 PD in 56 (40%) patients;35 - 40 PD in 42 (30%) patients, at far 20 - 25 PD in 84 (60%) patients;30 - 40 PD in 56 (40%) patients, fusional divergence at near after refractive eye surgery range from at near 6 - 8 PD in 108 (75.7%) patients;10 - 12 PD in 52 (37.1%), at far 6 - 8 PD in 126 (90%) patients;10 - 12 PD in 14 (10%) patients. None of the patients developed any ocular deviations. NCP, on average, decreases from 9.4 ± 1.5 cm to 9.1 ± 0.9 cm after. None of these patients with a normal NCP before surgery developed an abnormal NCP after refractive surgery. Eighteen patients (12.8%) had a stereopsis higher than 60 s of arch before surgical intervention. Of these, in 2 cases (2.8%) stereopsis increased from 200 to 40 s of arch after surgery. In the rest of patients stereopsis remained unchanged. Conclusion: The increase in fusion at near appears to be considerably interesting, whereas there is no worsening of stereopsis. A careful pre-surgery orthoptic evaluation is extremely revelant for a safe refractive surgery, this reducing the risk of complications associated with fusion and stereopsis.

Botulinum toxin type A in treating early-stage patients with small-angle acute acquired comitant esotropia

AIM:To investigate botulinum toxin A(BTXA)efficacy on small-angle(≤25Δ)acute acquired concomitant esotropia(AACE)in early-stage patients.METHODS:The electronic medical record data of AACE patients during March 2019 and June 2023 were collected in this retrospective and hospital-based cohort study.A total of 72 small-angle AACE patients received BTXA extraocular muscle injection.Patients were grouped by onset-to-treatment time(Group A:≤6mo,Group B:>6mo).Deviation of esotropia,eye alignment and stereopsis were analyzed at the period of pre/post-injection(1wk,1,3,and 6mo).Orthophoria rate at 6mo(horizontal deviation<10Δand binocular single vision)were considered as outcome index.RESULTS:There were no significant baseline differences(P>0.05)between two groups except onset-to-treatment time(2mo vs 11mo,P<0.001).Higher orthophoria rates were in Group A at last follow-up(94.74%vs 73.53%,P=0.013).Post-BTXA deviations of two groups at 1mo showed no difference(P>0.05);while in 3 and 6mo Group A was significantly smaller than group B(all P<0.001).No statistically significant differences were observed among all post-BTXA deviations of near and distance in Group A.In Group B,deviation at 3mo(near:2Δvs 0,P<0.001;distance:4Δvs 0,P<0.001)and 6mo(near:6Δvs 0,P<0.001;distance:6Δvs 0,P<0.001)was significant increased compared to deviation at 1wk after treatment.Group A showed better stereopsis recovery in last follow-up compared to Group B(80″vs 200″,P=0.002).Both groups obtained improved stereopsis after treatment(Group A:80″vs 300″,P<0.001;Group B:200″vs 300″,P=0.037).CONCLUSION:BTXA is effective for AACE with small deviation(≤25Δ)in early stage.Delayed treatment(>6mo)may reduce BTXA efficacy.Early BTXA intervention benefits long-term eye alignment and stereopsis recovery.