Sighting dominance and egocentric localization

Theories of the perception of visual direction use, either a hypothetical "projection center" midway between the two eyes, or the line of sight of the sighting dominant eye, as a reference point for egocentric localization. Seventy-five observers made judgments of the visual straight ahead. Their judgments varied as a function of both viewing condition and eye dominance. Judgments were biased toward the side of the viewing eye during monocular exposure, while binocular judgments were intermediate in their placement. Both monocular and binocular judgments were shifted in the direction of the sighting dominant eye, suggesting that the reference point for visual localization lies between the midpoint of the interocular axis and the line of sight of the sighting eye.     

Sighting ocular dominance magnitude varies with test distance

Background

Ocular dominance can be defined as the preference of an individual for viewing with one eye over the other for particular visual tasks. It is relevant to monovision contact lens wear, cataract surgery and sports vision. Clinically, the measurement of ocular dominance is typically done at an arbitrary distance using a sighting test, such as the hole‐in‐card method that has a binary outcome. We investigated the effect of test distance on ocular dominance measured using a binocular sighting test that provided a continuous measurement of dominance.

Methods

Ten participants with normal binocular vision took part in this study. Their binocular sighting ocular dominance and phorias were measured at one, two, four, eight and 10 metres. During the dominance tests participants made a binocular alignment judgment and then were asked to indicate the relative alignment of each eye using a visual analogue scale as a reference.

Results

Eight participants had strong ocular dominance (five right, three left). For these participants, there was a significant increase in the magnitude of dominance with increasing test distance (p < 0.001). This could not be fully explained by changes in convergence demand. Two participants showed very weak ocular dominance across all test distances (p > 0.05), despite changes in convergence demand.

Conclusion

When ocular dominance is present, its magnitude varies significantly with test distance. This has significant implications for the accurate measurement of ocular dominance in the clinic and may reflect the neural processes that influence eye preference.

     

Sighting dominance and monovision distance binocular fusional ranges.

Clinicians typically apply the distance correction to the dominant sighting eye in fitting presbyopic patients with monovision (MV) contact lenses. We evaluated the effect of this fitting strategy on distance binocular fusional ranges for 23 presbyopic subjects. This sample was composed of successful and unsuccessful MV wearers. Fusional ranges for the two MV fitting possibilities (distance lens on the dominant eye, near lens on the dominant eye) were compared to fusional ranges in which both eyes were fitted with the distance correction. A greater esophoric shift and greater reduction in vergence ranges were demonstrated when the non-dominant eye received the clear image compared to when the dominant eye received the clear image. Successful MV patients demonstrated these effects to a lesser degree than did unsuccessful patients. In general, effects of MV on distance binocular fusional ranges were fewer when successful MV subjects received the clear image in the dominant eye.     

Sighting dominance: An explanation based on the processing of visual direction in tests of sighting dominance

This study investigated the meaning of sighting dominance by examining its relationship to the processing of visual direction. In one experiment subjects' behavior in two sighting tests was evaluated. The data indicated that the reference point used in the tests is not the dominant eye but a central point consistent with the location of the visual egocenter. In a second experiment sighting dominance and the location of the egocenter were measured. The results indicated that the sighting eye is the eye nearest to the egocenter. Further analysis confirmed that sighting tests involve the processing of visual direction specified from the egocenter. The findings suggest that one eye is used in sighting tests because the tests force monocular viewing. The meaning of sighting dominance within the context of sighting behavior was discussed with the conclusion that sighting dominance is best understood as a residual effect caused by the egocenter being to one side of the midline and by the monocular demands of sighting tests.     

Eccentric visual acuity in patients with macular disease

A series of cards each containing a two dimensional array of identical Snellen "E's" was used to determine best eccentric visual acuity in patients with macular disease having Snellen visual acuity of 20/70 or worse. Each "full field E" card simultaneously presents the same letter to foveal and parafoveal areas. This test can therefore determine quickly if potentially useful vision is present in any area of the central visual field. In our study of 37 eyes, 70% demonstrated potential visual acuity at least two times better than visual acuity measured by conventional methods, and 20% demonstrated at least a fourfold improvement. This suggests that most patients with macular disease do not spontaneously employ their best remaining area of retina for fixation.     

Fixation in patients with juvenile macular disease.

PURPOSE: The instability of fixation with central scotoma has been mainly studied in patients with age-related macular diseases (MDs). However, early macular lesions can lead to different characteristics of fixation. The aim of this work was to study fixation in patients with juvenile MD. METHODS: Eye movements of 10 patients and 10 controls were monitored during fixation. Visual fields were assessed by static perimetry to determine the extent of the field defects. Eye movements were separated into saccades and drifts, with fixation stability assessed by bivariate contour ellipse area (BCEA). To quantify the number and location of preferred retinal loci (PRL), the kernel density estimator and expectation maximization for mixtures of gaussians were used. RESULTS: Patients have worse fixation stability than controls and large BCEAs resulted in more than one PRL. It was found that central field defects (10 degrees) have negative correlation with the size of BCEA. In addition, the meridian of saccades during fixation was correlated with the meridian inter-PRL. CONCLUSIONS: Patients with juvenile MDs have large BCEAs, frequently associated with two PRL. Similar results had been found for patients with age-related MDs. Also, the meridian of involuntary saccades during fixation was found to be correlated with the location of PRLs, suggesting a useful role of these movements in alternating between them.     

Local macular ERG in patients with Best's disease

We examined a pair of siblings, a 10-year-old girl (case 1) and a 12-year-old girl (case 2), with Best's diease. The visual acuity was nearly normal in both patients. The central visual field measured with auto-plot tangent screen revealed a small relative paracentral scotoma only in the left eye of case 2. We failed to detect any abnormality in photopic and scotopic electroretinogram (ERG) recorded with Ganzfeld stimuli and the electrooculogram light rise was absent in both patients.Local macular ERG was recorded under a fundus monitor by infrared television fundus camera with test spots of 5, 10, and 15 degrees in diameter. The center of the stimulus spot was always on the fovea during the recording. The local macular ERG was absent in both patients. Our results of local macular ERG may indicate disturbance of the central portion of the retina.     

Predicting reading fluency in patients with macular disease.

PURPOSE: Difficulty in reading is the most frequent complaint of patients with macular disease (MD). This article assesses whether clinical variables measured at the onset of MD can be used to predict patients' future reading ability. METHODS: Twenty-five patients with MD were recruited within 4 weeks of the onset of symptoms in their second affected eye. Clinical and demographic features were recorded at baseline and at the exit point of the study 3 to 12 months later. Odds ratios (OR's) were constructed to assess the predictive value of these variables in terms of reading fluency and any change in reading speed at the exit point of the study. RESULTS: Baseline contrast sensitivity was associated with future fluent reading (OR, 2.40; interval size, 0.15; 95% confidence interval, 1.13 to 5.07). Age, sex, scotoma size, disease type, visual acuity, and reading speed were not statistically significant predictors of future fluent reading. It was not possible to predict fully in which patients reading speed improved or deteriorated. CONCLUSIONS: Contrast sensitivity can predict the likelihood of future fluent reading in patients with MD. Baseline reading speed, visual acuity, age, disease type, and scotoma size are poor predictors of future reading performance.     

Disease laterality,eye dominance,and visual handicap in patients with unilateral full thickness macular holes

AIM: To investigate the association between visual handicap, laterality, and historical eye dominance in patients presenting with unilateral full thickness macular holes (FTMH). METHODS: Consecutive patients presenting with unilateral FTMH and no other visually significant ocular pathology including abnormalities of binocular vision were included. A questionnaire and case note review were performed to determine the mode of presentation, presence of symptomatic binocular interference, historically dominant eye, and whether they elected to undergo surgery. RESULTS: 44 eyes of 44 patients fulfilled the inclusion criteria. 21 (48%) affected eyes were right sided and 56% of FTMH were in the historically dominant eye. 76% of FTMH in historically dominant eyes presented symptomatically compared to 36% in non-dominant eyes (p= 0.003). 72% of patients with FTMH affecting their historically dominant eye were aware of binocular interference in day to day binocular viewing compared with 21% when the FTMH was in the non-dominant eye (p= 0.001). 23 (52%) patients elected to undergo surgery, of whom 18/23(78%) had FTMH in their historically dominant eye (p= 0.0003). CONCLUSION: This study suggests that eye dominance may be an important determinant of the visual handicap suffered by patients with unilateral FTMH.     

Asymmetry of the macular structure is associated with ocular dominance

Objective

We hypothesized that the ocular dominance associated with brain asymmetry would influence macular structure. We assessed the structural asymmetry of the macula by ocular dominance.

糖尿病性黄斑病变

本文观察65例有黄斑病变的糖尿病患者。全部患者均作眼科常规检查,详细检查眼底,除8只眼不能窥见眼底外,其余122眼均作彩色眼底照像和眼底血管荧光造影。属单纯型者40眼,占32.80%,增殖型82眼,占67.20%。按Sigelmen’s分期法,糖尿病性黄斑病变Ⅰ期17眼,占13.93%,Ⅱ期41眼,占33.60%,Ⅲ期40眼,占32.80%,Ⅳ期24眼,占19.67%。本组病例视力≥0.3者66眼,占54.00%,<0.3者56眼,占46.00%,<0.05者22眼,占18.00%。近半数患者为低视力和盲目,这些患者主要血糖控制不佳,病程较长,患者来诊时均属较晚期。故此作者认为眼科医师和内科医师有责任对糖尿病患者作有效的指导,以便避免严重的糖尿病视网膜病变和其他并发症的发生。本文还讨论了发病机理和治疗方法。     

Fixation stability and reading speed in patients with newly developed macular disease.

BACKGROUND: Patients with macular disease and central scotomas must use a peripheral, preferred retinal locus (PRL) in place of their damaged fovea. This paper investigates the development of the PRL, with particular reference to the stability of fixation. METHODS: Twenty-five patients with age-related and juvenile macular disease were recruited. All patients had developed a scotoma in their better eye within the previous 2 weeks. Patients were assessed using a scanning laser ophthalmoscope and an infra-red gazetracker on four further occasions over the next 12 months. RESULTS: A linear relationship exists between reading speed and fixation stability for patients and control subjects. Fixation stability was not related to scotoma size, visual acuity or contrast sensitivity. Changes in fixation stability account for 54% of the variance in change in reading speed over the course of this study. CONCLUSIONS: The deficit in reading speed in patients with macular disease can be partially attributed to impairments in fixation stability.     

Blue on yellow perimetry with scanning laser ophthalmoscopy in patients with age related macular disease

BACKGROUND/AIM: The loss of short wavelength sensitive (SWS) cone mechanism sensitivity is related to severe vision loss in patients with age related maculopathy (ARM). A case-control study of patients with ARM and age matched controls was performed, using blue on yellow static perimetry. METHODS: A bright yellow background at 594 nm isolated the responses of short wavelength cone mechanisms to 458 nm targets. A scanning laser ophthalmoscope produced stimuli and provided real time, simultaneous fundus illumination. The macula was probed with 16 Goldmann IV targets, 1-10 degrees from fixation, using a staircase method. RESULTS: 24 patients with non-exudative ARM were matched to 24 subjects with normal fundus appearance. SWS cone pathway sensitivity for macular targets was significantly reduced in the patients with ARM compared to normals--15.45 (SD 4.56) dB v 17.22 (0.28) dB, respectively (p<0.0005). There was not only a diffuse loss of sensitivity in ARM patients, but also a localised loss of sensitivity over drusen (p<0.025). Neither the mean age, 69 (8) years, nor the mean visual acuity differed between groups, logMAR 0.09 (0.10) v 0.05 (0.06) for ARM patients v normals, respectively. Patients with soft drusen had lower sensitivity than those with hard drusen (p<0.05). CONCLUSION: A loss of SWS cone pathway sensitivity occurred in most patients with early ARM, despite good visual acuity, demonstrating a loss of visual function that cannot be attributed to ageing changes. The loss of sensitivity, despite good visual acuity, included both a diffuse loss and localised losses.     

ABCA4 sequence variants in Chinese patients with age-related macular degeneration or Stargardt's disease

ABCA4 gene sequence alterations cause Stargardt's disease (STGD) and may cause some age-related macular degeneration (AMD). We sought to shed light on these associations among Hong Kong Chinese by genotyping 140 AMD, 18 STGD and 95 normal control subjects for 15 ABCA4 exons which were reported to often contain AMD- or STGD-associated mutations. Sequence alterations R212H, T1428M, V1433I, T1572M, I2166M, IVS6-5T>G and IVS33+1G>T were found in AMD patients. T1428M and R2040X occurred in STGD patients. Control subjects displayed all the above missense alterations but no splicing or nonsense changes. Therefore, ABCA4 splicing mutations may be associated with a small proportion of AMD cases.     

Serous detachments of the retinal pigment epithelium in patients with senile macular disease.

Thirty-one patients had senile macular disease with serous detachments of the retinal pigment epithelium without evidence of choroidal neovascularization. Of these 31 patients the natural history of 24 eyes was compared with 21 eyes treated with photocoagulation. Eight patients with bilateral detachments had treatment applied to one eye. There was no conclusive evidence that photocoagulation alters the natural course of this condition.     

Age-related macular degeneration in grandparents of patients with Stargardt disease: genetic study.

PURPOSE: To report clinical features and molecular genetic study in three unrelated families in which age-related macular degeneration was observed in grandparents of patients with Stargardt disease. METHODS: A complete ophthalmologic examination including best-corrected visual acuity measurement, fundus examination, and fluorescein angiography was performed on all members of the three families. The entire coding sequence of the ABCR gene was analyzed using a combination of single strand conformation polymorphism and direct sequence analysis of the 50 exons. RESULTS: Compound heterozygous missense mutations were observed in patients with Stargardt disease (Arg212Cys, Argl107Cys, Gly1977Ser, Arg2107His, and le2113Met). Heterozygous missense mutations were observed in the grandparents with age-related macular degeneration (Arg212Cys and Arg1107Cys). CONCLUSIONS: We report phenotype and genotype findings in three unrelated families segregating patients with Stargardt disease and age-related macular degeneration. The hypothesis that the Arg212Cys and Arg1107Cys ABCR gene mutations could be susceptibility factors for age-related macular degeneration is discussed. We speculate that the relatives of patients affected with Stargardt disease who are carriers of heterozygous ABCR gene mutations may have a higher risk of developing age-related macular degeneration.     

Evoked responses in patients with macular holes

Thirty-two eyes with idiopathic macular holes and one eye with a traumatic macular hole were assessed by pattern-reversal electroretinography, ganzfeld electroretinography and pattern-reversal visual evoked potentials. Results were inspected for qualitative abnormalities and then measured in comparison with fellow eyes and 41 control eyes of similar age. Qualitative abnormalities occurred in some eyes with macular holes, most commonly a reduction in pattern-reversal electroretinogram or pattern-reversal visual evoked potential amplitude; 15 check amplitudes were significantly lower in eyes with macular holes than in control eyes, but no significant difference in latency was found. Control pattern-reversal electroretinogram and pattern-reversal visual evoked potential amplitudes were noted to decline with age, and paired t-tests on an age-matched subgroup of eyes with macular holes and control eyes showed appreciable differences only in the pattern-reversal electroretinogram q-r (N95) amplitude.