Efficacy of visual process improvement in patients with homonymous hemianopia

Homonymous hemianopia is a visual field defect following a stroke, tumor development, traumatic brain injury and other rare causes. Due to the damage to the visual system, lateral neglect occurs that induces difficulties with detecting objects on one side of the binocular visual field, which exposes patients to potential danger during daily activities, especially performed outside – in traffic. Different optical aids such as Fresnel prism have been developed to help those patients by increasing the perception of the affected hemifield. This prism correction can appear in various configurations, for instance: yoked prism, monocular and binocular sector prisms placed with a base to the affected side. The other option to deal with these patients is visual training based on stimulating the affected hemifield.

Impact of binocular visual field loss on driving performance in glaucoma patients

AIM: To evaluate the driving performance in young and middle-aged Chinese glaucoma patients with mild to severe visual field loss compared to those without glaucoma by using a driving simulation test. METHODS: Twenty-nine participants were included in this study: nine patients with glaucoma but pass the binocular Esterman visual field test, ten patients with glaucoma and fail the binocular Esterman visual field test, and ten age-matched healthy controls. A driving simulation test was designed as a frequency-based analysis of a lane-keeping task. The total performance error, the control-response amplitude and delay were calculated. RESULTS: Esterman visual field test fail group showed the longest delay of control-response among three groups (P=0.02). And the delay in lane-keeping task was significantly associated with inferior field of better-eye (r=0.51, P=0.004) and integrated visual field (r=0.55, P=0.002). CONCLUSION: Young and middle-aged glaucoma patients with binocular visual field loss suffered from a longer delay of response in driving simulation test, while inferior visual field having more impact than superior visual field.

Is the Horizontal-Vertical Illusion Mainly a By-Product of Petter’s Rule?

The horizontal-vertical (HV) illusion is a classical example of an asymmetrical perception of size in the vertical and horizontal axes, also known as ‘anisotropy of the perceived space’. Several authors argued that the horizontally-oriented ellipse of the binocular visual field might play an important role in the emergence of this illusion. Alternatively, a length bisection bias and size-constancy mechanisms have been advocated to account for the asymmetrical perception in the two dimensions. To investigate this phenomenon, participants are commonly required to estimate the length of two separate lines, one vertical and one horizontal, often arranged in an inverted-T pattern. Here we suggest that this type of stimulus may introduce physical and subjective biases that prevent a fine investigation. In particular, we believe that Petter’s rule, that applies to two-dimensional patterns formed by two overlapping surfaces, may play a critical role that will not support an interpretation based on the shape of the binocular visual field nor a length bisection bias.

Utility of CLOCK CHART binocular edition for self-checking the binocular visual field in patients with glaucoma

Background/aimsCar accidents caused by drivers unaware of their visual field (VF) defects under binocular vision have become an issue. We developed a simple self-check chart (CLOCK CHART binocular edition (CCBE)) to help patients with glaucoma recognise their abnormalities in the binocular VF and evaluated its usefulness.MethodsThe chart has four targets displayed at 10°, 15°, 20° and 25° eccentricities. The examinee gradually rotates the chart 360° clockwise. At every 30°, the examinee confirms the fixation and indicates if all four targets can be seen. This study enrolled 88 eyes of 44 patients with glaucoma (mean age, 64.4±13.1 years) and 64 eyes of 32 visually normal individuals (mean age, 32.0±8.4 years). Except the CCBE test, static VF testing using the Humphrey field analyser (HFA) Swedish Interactive Threshold Algorithm-Standard 30-2 and binocular Esterman programmes was also performed for the subjects with glaucoma.ResultsVF abnormality was defined as two or more contiguous points with a sensitivity of <10 dB within the central 30°. The CCBE test had sensitivities of 85% and 82% with respect to the HFA and Esterman results, respectively. We also used the British VF standards for Group 1 (car/motorcycle) drivers, and a sensitivity of 88% was obtained for the CCBE. The chart had a specificity of 100% for the visually normal subjects.ConclusionThe CCBE test enables drivers with glaucoma to notice their VF abnormalities under binocular condition. The application of this simple self-check method appears promising for occasions such as driver licensing.