Metamorphopsia and letter recognition

The influence of visual distortion on face recognition

A person's ability to recognise familiar faces is critical to their participation in many aspects of society. Following an acquired brain injury or retinal disease, however, faces can appear distorted, a phenomenon known as prosopometamorphopsia. Although case reports have described a variety of changes in the appearance of faces during prosopometamorphopsia, the influence of the disorder on face recognition has not been rigorously investigated. In the present report, we quantify how well healthy observers can recognise familiar faces that have been distorted using a parametric model of prosopometamorphopsia. Our results reveal that face recognition varies systematically with the parameters of visual distortion, which, importantly, interact with the size of the face in a nonlinear but highly predictable manner. Our findings demonstrate that prosopometamorphopsia can lead to a surprising range of changes in the appearance of faces. The impact of visual distortion on face recognition thus depends critically on the distance at which the face is viewed, which is likely to change across social and clinical contexts.

Clinical Update on Metamorphopsia: Epidemiology, Diagnosis and Imaging

Purpose: To discuss the pathophysiology of metamorphopsia, its characterisation using retinal imaging and methods of assessment of patient symptoms and visual function.Methods: A literature search of electronic databases was performedResults: Metamorphopsia has commonly been associated with vitreomacular interface disorders (such as epiretinal membrane) and has also regularly been noted in diseases of the retina and choroid, particularly age-related macular degeneration and central serous chorioretinopathy. Developments in optical coherence tomography retinal imaging have enabled improved imaging of the foveal microstructure and have led to the localisation of the pathophysiology of metamorphopsia within the retinal layers of the macula. Alteration of alignment of inner and outer retinal layers at various retinal loci has been identified using multimodal imaging in patients with metamorphopsia in a range of conditions. Although the Amsler Grid assessment of metamorphopsia is a useful clinical indicator, new emerging methods of metamorphopsia assessment with psychophysical tests such as M-CHARTS and preferential hyperacuity perimetry, have been developed.Conclusions: It appears that there is a complex relationship between visual acuity and metamorphopsia symptoms that vary between retinal conditions. Although metamorphopsia has traditionally been challenging to measure in the clinic, advances in technology promise more robust, easy-to-use tests. It is possible that home assessment of metamorphopsia, particularly in conditions such as age-related macular degeneration, may help to guide the need for further clinic evaluation and consideration of treatment.

Stress and vision-related quality of life in acute and chronic central serous chorioretinopathy

BACKGROUND

To compare vision-related quality of life (VRQOL) between acute and chronic Central serous chorioretinopathy (CSC) and correlate this with Cohen's Perceived Stress Scale (PSS) questionnaire.

METHODS

Patients who were diagnosed with both acute and chronic CSC were recruited in this study. Vision-related quality of life (VRQOL) was assessed with Rasch revised National Eye Institute Visual Functioning Questionnaire 25 (NEI-VFQ25) and perceived stress with Cohen's PSS questionnaire in 118 subjects with either acute or chronic CSC. The quality of life score was compared between patients with acute and chronic CSC. Correlations between the functional score and visual acuity (VA), stage of CSC, and stress were studied.

RESULTS

There was no significant difference in VRQOL between Acute and Chronic CSC. In Acute CSC, affected eye VA correlated significantly with near vision question of the visual function subscale. Better eye VA correlated significantly with distance vision, social function, role limitation and dependency of the socioeconomic subscale. In chronic CSC, affected eye VA correlated with social function question of the socioemotional subscale and the better eye VA correlated with driving and distance vision of the visual function subscale. No other significant correlations with VA were noted. No correlations were observed between outcome of Cohen's PSS questionnaire and NEI-VFQ25 scores of acute and chronic CSC.

CONCLUSION

The VRQOL is similar between acute and chronic CSC. Perceived stress was not found to influence the VRQOL in CSC.

Digital Nullification of Visual Distortion to Quantify Metamorphopsia: A Pilot Study

BACKGROUND AND OBJECTIVE

To evaluate a novel digital method of metamorphopsia quantification in patients with symptomatic visual distortion as determined by M-CHARTS.

PATIENTS AND METHODS

In this institutional review board-approved, prospective, cross-sectional observational study, subjects were presented with an objectively straight dotted line that bisects a central fixation point. The subjects digitally altered the line's contour until it appeared straight. Calculation of the area between the original objectively straight line presented to the subject and their newly manipulated line was performed to determine the manipulated area under the curve (M-AUC).

RESULTS

Sixty-two percent of test targets were fully or significantly straightened by affected subjects. M-AUC was significantly correlated with M-CHARTS scores in both the horizontal (P < .001) and vertical (P = .05) orientations.

CONCLUSIONS

The deformation of an objectively straight line by a subject with metamorphopsia may be a viable way of both quantifying and spatially characterizing visual distortions. [Ophthalmic Surg Lasers Imaging Retina. 2020;51:11-20.].

Spatial-frequency dependent binocular imbalance in amblyopia

While amblyopia involves both binocular imbalance and deficits in processing high spatial frequency information, little is known about the spatial-frequency dependence of binocular imbalance. Here we examined binocular imbalance as a function of spatial frequency in amblyopia using a novel computer-based method. Binocular imbalance at four spatial frequencies was measured with a novel dichoptic letter chart in individuals with amblyopia, or normal vision. Our dichoptic letter chart was composed of band-pass filtered letters arranged in a layout similar to the ETDRS acuity chart. A different chart was presented to each eye of the observer via stereo-shutter glasses. The relative contrast of the corresponding letter in each eye was adjusted by a computer staircase to determine a binocular Balance Point at which the observer reports the letter presented to either eye with equal probability. Amblyopes showed pronounced binocular imbalance across all spatial frequencies, with greater imbalance at high compared to low spatial frequencies (an average increase of 19%, p < 0.01). Good test-retest reliability of the method was demonstrated by the Bland-Altman plot. Our findings suggest that spatial-frequency dependent binocular imbalance may be useful for diagnosing amblyopia and as an outcome measure for recovery of binocular vision following therapy.

Novel quantitative assessment of metamorphopsia in maculopathy

PURPOSE

Patients with macular disease often report experiencing metamorphopsia (visual distortion). Although typically measured with Amsler charts, more quantitative assessments of perceived distortion are desirable to effectively monitor the presence, progression, and remediation of visual impairment.

METHODS

Participants with binocular (n = 33) and monocular (n = 50) maculopathy across seven disease groups, and control participants (n = 10) with no identifiable retinal disease completed a modified Amsler grid assessment (presented on a computer screen with eye tracking to ensure fixation compliance) and two novel assessments to measure metamorphopsia in the central 5° of visual field. A total of 81% (67/83) of participants completed a hyperacuity task where they aligned eight dots in the shape of a square, and 64% (32/50) of participants with monocular distortion completed a spatial alignment task using dichoptic stimuli. Ten controls completed all tasks.

RESULTS

Horizontal and vertical distortion magnitudes were calculated for each of the three assessments. Distortion magnitudes were significantly higher in patients than controls in all assessments. There was no significant difference in magnitude of distortion across different macular diseases. There were no significant correlations between overall magnitude of distortion among any of the three measures and no significant correlations in localized measures of distortion.

CONCLUSIONS

Three alternative quantifications of monocular spatial distortion in the central visual field generated uncorrelated estimates of visual distortion. It is therefore unlikely that metamorphopsia is caused solely by retinal displacement, but instead involves additional top-down information, knowledge about the scene, and perhaps, cortical reorganization.