Stereoacuity Research Articles

Randomised trial of three treatments for amblyopia: Vision therapy and patching, perceptual learning and patching alone.

Active vision therapy for amblyopia shows good results, but there is no standard vision therapy protocol. This study compared the results of three treatments, two combining patching with active therapy and one with patching alone, in a sample of children with amblyopia. Two protocols have been developed: (a) perceptual learning with a computer game designed to favour the medium-to-high spatial frequency-tuned achromatic mechanisms of parvocellular origin and (b) vision therapy with a specific protocol and 2-h patching. The third treatment group used patching only. Fifty-two amblyopic children (aged 4-12 years), were randomly assigned to three monocular treatment groups: 2-h patching (n = 18), monocular perceptual learning (n = 17) and 2-h patching plus vision therapy (n = 17). Visual outcomes were analysed after 3 months and compared with a control group (n = 36) of subjects with normal vision. Visual acuity (VA) and stereoacuity (STA) improved significantly after treatment for the three groups with the best results for patching plus vision therapy, followed by monocular perceptual learning, with patching only least effective. Change in the interocular difference in VA was significant for monocular perceptual learning, followed by patching. Differences in STA between groups were not significant. For VA and interocular differences, the final outcomes were influenced by the baseline VA and interocular difference, respectively, with greater improvements in subjects with poorer initial values. Visual acuity and STA improved with the two most active treatments, that is, vision therapy followed by perceptual learning. Patching alone showed the worst outcome. These results suggest that vision therapy should include monocular accommodative exercises, ocular motility and central fixation exercises where the fovea is more active.

Contrast Sensitivity and Low Contrast Visual Acuity in Children With Normal Visual Acuity

To measure and report the distribution of distance and near contrast sensitivity (CS) and low contrast visual acuity (LCVA) at 5% and 2.5% contrast in children aged 5-15 years with normal visual acuity (VA). Prospective, cross-sectional study. Schools in Southern India. One thousand fifty-two children aged 5 to 15 years (mean age 10.61 ± 2.85 years) with a presenting visual acuity of 0.00 logMAR or better in both eyes and a stereo acuity of 40 seconds of arc or better were recruited from nine schools. Repeatability of contrast sensitivity and low contrast visual acuities were tested in 246 children. Pelli-Robson charts were used to measure the distance and near contrast sensitivity at 1 m and 40 cm, respectively. The low contrast visual acuity was recorded at 5% and 2.5% contrast using LEA Symbols at 3 m. Overall, the mean ± SD, (95% CI) monocular distance and near CS were 1.75 ± 0.11 (1.76-1.75) logCS and 1.72 ± 0.10 (1.73-1.71) logCS, respectively. The mean LCVA at 5% and 2.5% contrasts were 0.20 ± 0.10 (0.21-0.20) logMAR and 0.39 ± 0.11 (0.40-0.39) logMAR, respectively. Distance and near CS gradually improved till the ages of 11 and 13, respectively, and then plateaued. Similarly, LCVA at 5% and 2.5% contrasts gradually improved till age ten before plateauing. The Coefficient of Repeatability (CoR) for CS was ±0.02 logCS for distance, ±0.05 logCS for near, and ±0.01 logMAR for both LCVA contrasts. The study provides age-specific normative values for distance and near CS, and LCVA in a cohort of children aged 5-15 years. These results are important to understand the impact of ocular conditions on CS in children and have utility in clinical evaluations.

Refractive error and abnormal stereopsis association with road traffic accidents in Saudi Arabian truck drivers.

To investigate the visual functions of truck drivers of the Kingdom of Saudi Arabia (KSA) in the region of Qassim and Dammam and to see if is there any association between these visual functions and self-reported road traffic accidents (RTA). It is a cross-sectional, descriptive study. LogMAR visual acuity, refractive error, color vision, stereopsis, and confrontation visual fields were measured in 300 truck drivers in the Qassim and Dammam regions of KSA. Driving-related history and incidence of RTA from the past 3 years, systemic history, and general eye compliance history were collected through a self-reporting questionnaire. Among 300 truck drivers examined, 54 (18.4%) subjects have a refractive error, 14 (4.7%) subjects have color vision deficiency, 37 (12.2%) subjects have abnormal stereo acuity, and none of them have confrontation visual field defect. RTA was reported in 25 (8.3%) subjects. The current study has found RTA is significantly associated with refractive error (P = 0.01) and abnormal stereopsis (P < 0.01). Systemic history revealed that 11% of the subjects had diabetes mellitus. The current study is the first to report on the visual functions of KSA truck drivers. Hence, the current study has found a significant association between visual functions and RTA among truck drivers, we recommend a comprehensive examination need to be part of issuing driver's licenses in KSA. More studies with larger samples from different regions of KSA are needed to extrapolate these findings.

Major Visual Impairment in Special Children

Objective: This study aims to identify the major visual impairment among special children. Methods: This cross-sectional study was conducted among 120 children within 3-15 years of age group at a vision therapy centre between April-June of 2023. Results: Low visual acuity was seen in children who had a development delay of 0.79%. In 15.7% of cases of autism spectrum disorder (ASD), astigmatism was present. Nystagmus was seen in 5.8% of cases of cortical visual impairment (CVI). 9.9% of those with attention-deficit/hyperactivity disorder (ADHD) were unable to both accommodate and converge. In 14.0% of cases, the stereo acuity was poor. Ocular mobility was impaired in 9.1% of developmental delay cases, 14.0% of CVI cases, and 25.6% of ASD cases. Fusion was not performed well by 9.9% of ADHD patients. Suppression and diplopia were present in 25.6% of ASD cases, 14.0% of CVI cases, and 9.1% of developmental delay cases. 7.4% of ADHD patients and 12.4% of CVI patients had photophobia. 9.9% of ADHD patients and 14.0% of CVI patients were unable to perform spatial orientation. Children with developmental delays, ASD, ADHD, and CVI were more likely to be impacted and had abnormal visual function.

Assessment of stereoacuity (3D vision) using TNO random dot stereo acuity chart in medical undergraduate students: A cross-sectional study

The study aimed to estimate the level of stereoacuity in medical undergraduate students, factors associated with reduced stereoacuity, and time taken to interpret plates. Cross-sectional study was done at the Medical College of South Gujarat from April 2021 to June 2022, enrolling 400 consenting students. Detailed ocular history was taken; best corrected visual acuity was assessed for distance and near after cycloplegic refraction for cases with subnormal visual acuity and power of glasses documented. Level of Stereopsis was assessed using TNO random dot stereoacuity chart and time taken to read plates 1 and 5 was recorded. Data were entered and appropriate statistical tests were applied. Out of 400 students, 64.25% had a refractive error. Simple myopia was most prevalent refractive error (43.25%), followed by compound myopic astigmatism (19.5%). Seven students had anisometropic amblyopia and two had strabismic amblyopia. 19.75% cases had subnormal stereopsis. Among them, 10.25% cases had simple myopia, 7.25% had high compound myopic astigmatism, 1.75% had anisometropic amblyopia and 0.5% cases had strabismic amblyopia. Average time taken by emmetrope to read plate 1 and plate 5 was 13.93 ± 14.03 and 19.03 ± 20.66 respectively and for cases with refractive errors, time taken was 17.59 ± 13.95 and 27.83 ± 20.77 respectively. This was statistically significant (P &amp;#60;0.05). Most of the students had good stereoacuity as they were already wearing refractive correction. Commonest cause of subnormal stereopsis ware simple myopia, compound myopic astigmatism and amblyopia. Time taken to read the plates is more for refractive error as compared to emmetropes.

Efficacy of anti-suppression therapy in improving binocular vision in children with small-angle Esotropia

PurposeTo evaluate the efficacy of anti-suppression exercises in children with small-angle esotropia in achieving binocular vision. MethodsA retrospective review of patients aged 3–8 years who underwent anti-suppression exercises for either monocular or alternate suppression between January 2016 and December 2021 was conducted. Patients with esotropia less than 15 prism diopters (PD) and visual acuity ≥ 6/12 were included. Patients with previous intra-ocular surgery or less than three-month follow-up were excluded. Success was defined as the development of binocular single vision (BSV) for distance, near, or both (measured clinically with either the 4 prism base out test or Worth four dot test) and maintained at two consecutive visits. Qualified success was defined as the presence of diplopia response for both distance and near. Additionally, improvement in near stereo acuity was measured using the Stereo Fly test. ResultsEighteen patients with a mean age of 5.4 ± 1.38 years (range 3–8 years) at the time of initiation of exercises were included in the study. The male female ratio was 10:8. The mean best corrected visual acuity was 0.18 LogMAR unit(s) and the mean spherical equivalent was +3.8 ± 0.14 diopters (D). The etiology of the esotropia was fully accommodative refractive esotropia (8), microtropia (1), post–operative infantile esotropia (4), partially accommodative esotropia (1), and post-operative partially accommodative esotropia (4). Patients received either office-based, home-based, or both modes of treatment for an average duration of 4.8 months (range 3–8). After therapy, BSV was achieved for either distance or near in 66.6 % of patients (95 % CI = 40.03–93.31 %). Binocular single vision for both distance and near was seen in 50 % of children. Qualified success was observed in 38.46% of patients. Persistence of suppression was observed in one patient (5.5 %). Near stereopsis improved to 200 s of arc or more in 60% of the patients. The mean esotropia reduced from 5.7 ± 4.0 PD for distance and 6.2 ± 4.66 PD for near to 2.7 ± 2.4 PD and 3.38 ± 4.7 PD respectively, at the last follow-up (p-value 0.004 and 0.006). Failure of therapy was noticed after six months of follow-up in the child with infantile esotropia. ConclusionAnti-suppression exercises may be beneficial to improve binocular vision functions in children with small-angle esotropias of variable etiologies. Recurrence of suppression after cessation of therapy is possible, warranting regular follow up.

Comparison of stereopsis thresholds measured with conventional methods and a new eye tracking method.

Stereopsis is the ability to perceive depth using the slightly different views from two eyes. This study aims to conduct innovative stereopsis tests using the objective data outputted by eye tracking technology. A laptop and an eye tracker were used to establish the test system. Anaglyphic glasses were employed to execute the stereopsis assessment. The test symbol employed was devised to emulate the quantitative measurement component of the Random Dot 3 Stereo Acuity Test. Sub-pixel technology was used to increase the disparity accuracy of test pages. The tested disparities were: 160″, 100″, 63″, 50″, 40″, 32″, 25″, 20″, 16″, and 12.5″. The test was conducted at a distance of 0.65m. Conventional and eye tracking stereopsis assessments were conducted on 120 subjects. Wilcoxon signed-rank test was used to test the difference, while the Bland-Altman method was used to test the consistency between the two methods. The Wilcoxon signed-rank test showed no significant difference between conventional and eye tracking thresholds of stereopsis (Z = -1.497, P = 0.134). There was a high level of agreement between the two methods using Bland- Altman statistical analysis (The 95 per cent limits of agreement were -0.40 to 0.47 log arcsec). Stereoacuity can be evaluated utilizing an innovative stereopsis measurement system grounded in eye tracking technology.

A Comparative Study of Manual and Digital Methods and Stereopsis Assessment in Young Adults

Reduced stereopsis or depth perception may be the early indicator of abnormal motor functions in people therefore, the stereopsis test is considered ideal for visual screening. It can accomplish the need for the assessment of stereopsis by using a cost-effective smartphone application. Objective: To compare the stereo acuity values of manual and digital stereopsis tests by using the Random Dot Stereo Acuity test with Lea Symbols (Manual) and the SAT App for Android (Digital). Methods: A comparative cross-sectional study was carried out in the Eye department at The University of Lahore Teaching Hospital from February 2023 to May 2023. A total of 62 subjects aged 15-35 years were included in our study, out of which 31 were emmetropes and 31 were ametropes. Screening of subjects was done which included torch light examination and basic refraction. Manually stereopsis was measured using Random Dot stereo acuity test with Lea symbols and digitally it was measured by SAT application. Results: The mean ± SD stereo acuity value of the manual test (N=62) was 60.5242 ± 36.47607 seconds of arc and the mean stereo acuity value of the digital test (N=62) was 70.0968 ± 28.29569 seconds of arc. P-value was 0.006 which confirmed that our results were statistically significant. Conclusions: Our study highlighted the comparison of digital and manual stereopsis tests. We obtained different stereo acuity values from both tests on the same individuals. Hence, the manual test gave better values of stereopsis than the digital test.

A Prospective Trial to Assess the Efficacy of Eye-Tracking-Based Binocular Treatment versus Patching for Children’s Amblyopia: A Pilot Study

ABSTRACT Purpose To assess visual acuity (VA) and stereoacuity (SA) improvements in children with amblyopia treated with either binocular dichoptic treatment or patching treatment. Methods In this pilot prospective coherent study, 34 participants between 4 and 9 years of age with unilateral anisometropic amblyopia and without history of prior amblyopia treatment were enrolled into three groups. Full treatment group (FTG; n = 12): participants were prescribed the binocular dichoptic treatment to watch for 90 minutes per day, 5 days a week. Part-time treatment group (PTTG; n = 8): participants were prescribed the same binocular treatment as FTG, 90 minutes per day, 3 days per week. Patching treatment group (PTG; n = 14): participants wore an adhesive patch over the dominant eye for 2 hours per day, 7 days per week. Amblyopic-eye distance visual acuity (DVA), near visual acuity (NVA) and SA were evaluated at baseline, 4, 8, and 12 weeks. Results At 12 weeks, mean amblyopic-eye DVA improved 1.8 lines (95% CI, 1.1–2.5) in FTG, 1.5 lines (95% CI, 0.4–2.7) in PTTG and 3.0 lines (95% CI, 2.0–4.0) in PTG. The amblyopic-eye NVA improved 2.9 lines (95% CI, 2.4–3.5) in FTG, 1.7 lines (95% CI, 0.5–3.0) in PTTG and 2.8 lines (95% CI, 1.8–3.9) in PTG. The SA improved 0.38 log-arcseconds (95% CI, 0.24–0.53) in FTG, 0.59 log-arcseconds (95% CI, 0.36–0.82) in PTTG and 0.40 log-arcseconds (95% CI, 0.13–0.67) in PTG. No significant differences were found in DVA, NVA or SA improvement between FTG and PTG at 12 weeks. Conclusions VA and SA after binocular dichoptic treatment produced a similar therapeutic outcome to patching, suggesting a potential value for binocular therapy when treating anisometropic moderate degree of Children’s amblyopia.

Commentary: Leap forward in presbyopia management - Correcting beyond spectacles.

Commentary: Leap forward in presbyopia management - Correcting beyond spectacles.

Evaluation of Visual Skills Between Cricket Players and Sedentary Individuals

Aim: This study aims to evaluate the visual skills between cricket players and sedentary individuals of the same age group and to determine that visual skills are beneficial for both competitive sports performance and daily task activities. Settings and Design: It was a sports vision-based comparative study conducted in the outpatient department of ophthalmology for preliminary ocular examination as well as in the cricket ground for sports vision-based tests. Methods and materials: This study carries 200 subjects out of which 100 cricket players and 100 sedentary individuals (i.e individuals who are not involved in any sports activities) participated between the age group of 18 to 26. Participants underwent preliminary ocular examinations in which all those ocular diseases and binocular vision anomalies are excluded. All subjects were undergone the following sports vision test: stereopsis was measured by Randot stereo acuity chart, accommodative facility with +/- 2.00 flippers, saccadic eye movement was measured by Lang fixation stick and eye-hand coordination was recorded by Alternate hand wall toss test. Result: The cricket players exhibited better accommodative facility (p=0.05) saccadic eye movements (p=0.03) and better eye-hand coordination (p=0.01) stereopsis was good in sedentary individuals (p=0.06) confirming that basic visual skills were high in sedentary individuals. Conclusion: These findings evidence that cricket players exhibit better performance in more visual skills in comparison with a group of individuals without sporting background, suggesting an improvement in visual skills due to routine systematic activity in sports as well as daily tasks.

The Effects of Binocular Visual Function Training after Concomitant Exotropia Surgery

Purpose This study investigated the effect and long-term efficacy of binocular visual function training after concomitant exotropia surgery. Methods A total of 92 patients who underwent concomitant exotropia surgery were randomly divided into group A (the training group) (n = 54), who received binocular four-dimensional (4D) visual function training after surgery, and group B (control group) (n = 38). The patients in group A received personalized 4D visual function training 2 weeks after surgery and were followed up for 12 months. The eye position, distant and near stereo acuity, respectively, and postoperative efficacy were compared with those of the patients in group B. Results The normal eye position rate in group A was higher than in group B at the end of the overall follow-up period (p < .05), and the near stereo acuity rate was higher than the distant stereo acuity rate in both groups A and B at 2 weeks after surgery and at the end of follow up. The distant and near stereo acuity rates of the patients in group A were higher than those in group B (p < .05) at the end of the follow-up period, and the distant stereo acuity of group A was significantly improved (p < .05). The functional complete and incomplete response rates of group A were significantly higher than those of group B at the end of the follow-up period (p < .05). Conclusions Four-dimensional visual function training for patients after concomitant exotropia surgery could facilitate the recovery of postoperative binocular visual function, as well as prevent the recurrence of exotropia after surgery.

Vision Beyond Vision: Lessons Learned from Amblyopia

ABSTRACT Amblyopia is characterized by spatiotemporal uncertainty in the visual system. In addition to its effects on vision, amblyopia also exerts a widespread impact on other systems. Many of these changes are observed not only during amblyopic eye viewing but also during fellow eye and binocular viewing. They generally correlate with the severity of visual acuity and stereo acuity loss. The affected systems include: (1) oculomotor control manifested as abnormal fixation, saccades, smooth pursuit, and saccadic adaptation; (2) motor control with altered programming, execution, and temporal dynamics of eye-hand coordination, and decreased ability of the sensorimotor system to adapt to changes in the visual environment; (3) balance control with decreased postural stability; (4) multisensory integration characterized by reduced McGurk effect and altered cross-modal interactions in audiovisual perception; and (5) auditory localization manifested as impaired spatial hearing as a result of abnormal developmental calibration of the auditory map. To detect amblyopia early, a targeted approach is required to identify children from low-income families through in-school visual screening, supplemented by follow-up care and free eyeglasses in high-needs schools.

VISUAL IMPAIRMENT PREDICTS PHYSICAL FUNCTION DECLINE: THE HEALTH, AGING, AND BODY COMPOSITION (HEALTH ABC) STUDY

Abstract The relationship between visual impairment (VI) and decline in physical function with age is poorly understood. We constructed separate linear mixed models to evaluate the relationship of self-reported (visual function question (VFQ) score) or performance-based (visual acuity (VA); log contrast sensitivity (LCS); stereoacuity (SA)) VI with change in performance on the Short Physical Performance Battery (SPPB) over 8 years in 2219 Health ABC participants. Mean age was 75.5 years (range 71-82); 52.4% were female, and 37.4% were black. For all measures of visual function, better vision was associated with loss of approximately -0.3 SPPB units/year which was similar to the unadjusted change in SPPB over time (-0.328 units/year 95%CI (-0.35, -0.31)). Participants with LCS ≤1.3 log units experienced 58% faster rate of decline versus those with better LCS (test of difference in slopes p&amp;lt; 0.0001). Those with poor VA ≥20/50 showed a 50% greater decline in SPPB (p=0.0029), and those with low SA ≤85 arcsec demonstrated a 33% faster decline (p&amp;lt; 0.001) relative to those with better visual function. Compared to the slope at the mean VFQ score, a 1 standard deviation lower score was associated with 23% greater decline in SPPB (p&amp;lt; 0.0001). The difference in SPPB slopes remained significant across VI measures after adjusting for longitudinal decline associated with age, sex, and black race (all p&amp;lt; 0.05). Both self-reported and performance-based VI predicted faster declines in SPPB over time. Whether older adults with VI might benefit from targeted intervention to prevent declining mobility function remains to be evaluated.

Characteristics of visual function in children with autism complicated with mental retardation

Objective: To explore the characteristics of visual function and eye diseases in children with autism spectrum disorder (ASD) and mental retardation. Methods: It was a cross-sectional study. Two hundred and ninety-two cases (584 eyes) of children with ASD combined with mental retardation from 7 special education schools in Chaoyang District of Beijing, including 235 males (80.48%) and 57 females (19.52%); The age ranged from 2 to 18 years old. Subjective far and near vision, near stereoacuity, objective vision, diopter, anterior segment and fundus were examined. In addition, 300 students with normal intelligence level, aged 2 to 18 years, were included as controls. LogMAR was used to record vision examination. Subjective, objective vision and diopter were examined. Mann Whitney U test or Kruskal Wallis H test was used for the data of children with different genders, different age. Results: Among 584 eyes of children with ASD and mental retardation, 272 eyes (47.22%) were ametropia, 260 eyes (45.14%) were astigmatism, 29 eyes (5.03%) were hyperopia, 10 eyes (1.74%) were myopia, and 47 eyes (8.16%) were amblyopia risk factors. Among 292 children, there were 20 cases of strabismus (6.85%), 3 cases of color weakness (1.03%), and 4 cases of external eye abnormalities (1.37%). Two hundred and eleven children completed near stereopsis examination, of which 54 (25.59%) were within 100″ and 157 (74.41%) were within 200″ to 900″. Two hundred and seventy-two eyes with ametropia, 157 eyes (57.72%) needed correction but did not. The median and quartile of subjective and objective logMAR visual acuity were 0.22(0.10, 0.35), 0.10(0.00, 0.22), respectively; There were no significant differences in far visual acuity, near visual acuity, objective visual acuity, diopter, and near stereoacuity between different genders of ASD children with mild or moderate mental retardation (all P>0.05); There was a statistically significant difference in ASD children with mild mental retardation at different age rangs (H=21.453, P<0.001). There was a statistically significant difference in subjective tests such as far visual acuity and near visual acuity, for children with moderate mental retardation (Z=-3.508, -4.503; P<0.001). There was no statistically significant difference in objective visual acuity, diopter and near stereo acuity(all P>0.05). There are 300 healthy children as the control group, with LogMar's subjective far vision is 0.10(0.00, 0.22), and the objective vision is 0.00(0.00, 0.10), diopter 0.25 (-0.25, 0.50) D. Compared with healthy children, ASD children with mental retardation had a significant difference in subjective far vision and objective vision (Z=-8.527, -10.393; P<0.001). There was no significant difference in diopter (Z=-1.274, P=0.203). Conclusions: The subjective and objective visual acuity of children with ASD combined with mental retardation was lower than that of healthy children. The prevalence and uncorrected rate of refractive errors, strabismus, amblyopia and other eye diseases were significantly higher than those of healthy children. Their refractive errors were mainly astigmatism, and the rates of correction and treatment were low.

A Digital Alternative to the TNO Stereo Test to Qualify Military Aircrew

INTRODUCTION: Stereopsis is usually required in military aviators and may become increasingly important with reliance on newer technologies such as binocular Helmet-Mounted Displays (HMDs) and stereo displays. The current stereo test used to qualify UK military aircrew (TNO test) has many limitations. To address these limitations, two computer-based digital versions of a random dot stereogram (RDS) were developed: a static version (dRDS-S), and a version in which the dots appear to move dynamically within the depth plane (dRDS-D), both capable of measuring stereo acuity to threshold.METHODS: There were 41 participants who performed all 3 stereo tests, TNO and both digital dRDS tests, on two separate occasions.RESULTS: The best (lowest) mean stereo acuity threshold was measured with dRDS-S (33.79 arcseconds, range 12.64-173) and the worst mean stereo acuity thresholds were measured with the TNO test (91 arcseconds, range 60-240). Both dRDS tests were strongly correlated, but neither correlated with the TNO test. Both dRDS tests were more reliable, as indicated with tighter limits of agreement.DISCUSSION: With a large floor effect at 60 arcseconds, the TNO test was unable to characterize any finer degree of stereo acuity. Both dRDS tests demonstrated better test-retest reliability and addressed many of the limitations seen with the TNO test. The dRDS tests were not correlated with the TNO test, which suggests that the TNO test does not provide the accuracy or reliability for use as a meaningful aeromedical screening test. The dRDS tests will enable research to investigate the relationship between stereo acuity and operational performance.Posselt BN, Seemiller E, Winterbottom M, Baber C, Hadley S. A digital alternative to the TNO stereo test to qualify military aircrew. Aerosp Med Hum Perform. 2022; 93(12):846-854.

The Effect of Home-Based Dichoptic Therapy on Young Adults with Non-Strabismic Anisometropic Amblyopia on Stereo Acuity [Letter

The Effect of Home-Based Dichoptic Therapy on Young Adults with Non-Strabismic Anisometropic Amblyopia on Stereo Acuity [Letter

Options and considerations for the correction of presbyopia in the absence of cataract

AbstractPRESBYOND Laser Blended Vision is a treatment option for presbyopic patients that combines micro‐anisometropia with increased depth of field through non‐linear aspheric ablation profiles. This technique substantially improves visual outcomes in comparison with the conventional monovision approach. Trials show that PRESBYOND is effective in presbyopic patients with refractive errors between +5.75 and −9.00 D, including emmetropic presbyopes. With the safety advantages of modern femtosecond LASIK, retention of functional stereo acuity, contrast sensitivity and quality of vision, the rapid bilateral surgical procedure and a recovery time of a few hours, patient satisfaction is extremely high. In patients with no visually significant cataract, performing a corneal treatment avoids the increased risks associated with intraocular surgery, particularly risks that are relatively higher in younger presbyopic patients such as retinal detachment.

The Effect of Home-Based Dichoptic Therapy on Young Adults with Non-Strabismic Anisometropic Amblyopia on Stereo Acuity.

To evaluate the effect of home-based dichoptic visual therapy using anaglyphic red-green filters on the stereo acuity in a sample of young adults with non-strabismic anisometropic amblyopia. The study was observational and cross-sectional in design. Two groups (experimental vs control) were sourced using purposive sampling of young adults with non-strabismic amblyopia (experimental group) in comparison to an age-match control group without amblyopia. For the purpose of refractive adaptation, all participants in both groups were asked to wear their spectacle correction constantly for at least 16 weeks prior to exposure to home-based dichoptic therapy. Stereo acuity measurements using the Stereo Fly test were obtained before and after 40 hours exposure to home-based dichoptic therapy. The changes in stereo acuity post eight weeks (40 hours) training from baseline measurements was obtained. The difference in medians between the experimental and control groups using the Mann-Whitney U-test was measured with significance set at P value of <0.05. A total of 38 young adults (19 males, 19 females) with a mean age of 24.05 ± 5.66 years were enrolled in this study. Nineteen anisometropic amblyopes comprised the experimental group, fifteen of which were classified as moderate amblyopia (6/12-6/36) and 19 non-amblyopes comprised the control group. Home-based dichoptic therapy used on the experimental group after 8 weeks showed a significant improvement in stereo-acuity with a mean improvement of 345.26 ± 184.85 sec arc-1 [IQR:260;600; p<0.001] when compared to the control group. Home-based dichoptic therapy improved stereo-acuity in non-strabismic anisometropic amblyopes (moderate) in young adults. Thus suggesting that binocularity can improve in anisometropic adult amblyopes with a treatment modality that may be a convenient option better suit the demanding lifestyle of economically active adults who may not be able to comply with clinic-based therapy.

Assessment of depth perception with a comprehensive disparity defined letter test: A pilot study.

Current clinical tests mostly assess stereopsis with crossed disparity at near. These tests are designed with fine targets (high spatial frequency) and may fail to capture the “functional stereopsis” in real-world scenes, which consist of a range of spatial frequencies (SFs). We developed a stereo letter test that can assess crossed and uncrossed stereoacuity at near and far, at different SFs defined by the letter size. The test consists of disparity-defined letters embedded in random-dot stereograms. At each letter size, the letters are arranged in sets of trigrams like in the Pelli-Robson chart. The letter sizes correspond to SFs ranging from 0.3 to 2cpd. Within each triplet, all letters have the same disparity and the amount of disparity decreases after each set. Subjects report the letters verbally to determine the smallest disparity at each letter size. Twenty-four subjects were tested with eight different charts: crossed vs. uncrossed disparity at far and near, with two versions (different letter sequences). The disparity sensitivity function (DSF) had an inverted U-shape, with decreasing sensitivity for smaller stereo letters. The subjects had better stereopsis at far than near. All the subjects had lower stereo thresholds with crossed disparity than uncrossed, consistently at both distances. We found no effect of age or heterophoria on the DSF. The charts have good test-retest reliability (Pearson’s r = 0.89, p<0.001) and are easy to perform. Our results with stereo letters as stimuli are comparable to results from studies using depth corrugations. This stereo acuity letter test permits assessment of stereopsis at different testing distances, directionality of disparity, and across a range of SFs, which can help diagnose selective stereo losses in binocular vision anomalies and monovision. Assessment of stereopsis at different SFs may provide additional information for understanding daily stereovision demands than the conventional tests.