A method to determine the impact of reduced visual function on nodule detection performance

Reduction of visual acuity decreases capacity to evaluate radiographic image quality

INTRODUCTION

To determine the impact of reduced visual acuity on the evaluation of a test object and appendicular radiographs.

METHODS

Visual acuity was reduced by two different magnitudes using simulation glasses and compared to normal vision (no glasses). During phase one phantom images were produced for the purpose of counting objects by 13 observers and on phase 2 image appraisal of anatomical structures was performed on anonymized radiographic images by 7 observers. The monitors were calibrated (SMPTE RP133 test pattern) and the room lighting was maintained at 7 ± 1 lux. Image display and data on grading were managed using ViewDEX (v.2.0) and the area under the visual grading characteristic (AUC_VGC) was calculated using VGC Analyzer (v1.0.2). Inferential statistics were calculated using SPSS.

RESULTS

For the evaluation of appendicular radiographs the total interpretation time was longer when visual acuity was reduced with 2 pairs of simulation glasses (15.4 versus 8.9 min). Visual grading analysis showed that observers can lose the ability to detect anatomical and contrast differences when they have a simulated visual acuity reduction, being more challenging to differentiate low contrast details. No simulation glasses, compared to 1 pair gives an AUC_VGC of 0.302 (0.280, 0.333), that decreases to 0.197 (0.175, 0.223) when using 2 pairs of glasses.

CONCLUSIONS

Reduced visual acuity has a significant negative impact on the evaluation of test objects and clinical images. Further work is required to test the impact of reduced visual acuity on visual search, technical evaluation of a wider range of images as well as pathology detection/characterization performance.

IMPLICATIONS FOR PRACTICE

It seems that visual performance needs to be considered to reduce the risks associated with incomplete or incorrect diagnosis. If employers or professional bodies were to introduce regular eye tests into health screening it may reduce the risk of misinterpretation as a result of poor vision.

Visual function assessment of diagnostic radiography students

INTRODUCTION

Deterioration of visual acuity (VA) and visual impairment has been linked to age-related subtle changes, gender, and a correlation to socioeconomic status. This study aimed to assess first-year diagnostic radiography students' visual functional abilities by applying the International Classification of Impairments, Disabilities and Handicaps (ICIDH) recommendations of functional VA screening and health-related quality of life questionnaire (HRQOL).

METHODS

The design followed the World Health Organisation (WHO) electronic VA testing of monocular sight using LogMAR charts and binocular vision using Snellen charts, and an HRQOL questionnaire assessing for reduced ability of visual-based tasks in activities of daily living (ADL). The data was evaluated in correlation to the participant's visual correction, age, gender, and socioeconomic background.

RESULTS

Seventy students were recruited, all meeting the WHO standard level for visual ability, with 100% (n = 70/70) met or achieved above normal binocular vision, correlating to expected normal population results from published studies for age. The monocular vision demonstrated 74% (n = 52/70) for the right eye, and 80% (n = 56/70) for the left eye for normal vision levels. The results did not differ significantly between each eye (p = 0.21), gender variations between the left eye (p = 0.27) and the right eye (p = 0.10) results were affected by sample ratio of females (80%; n = 56/70) to males (20%; n = 14/70), the visual correction did not impair binocular VA. The HRQOL assessment indicated no significant functional VA issues in the study sample. The study demonstrated no association between the participant's socioeconomic background that may influence their VA ability.

CONCLUSION

The results provided normative binocular and monocular data on visual function in a sample of student radiographers and indicated that their thresholds align to normal (or near-normal) VA standards.

IMPLICATIONS FOR PRACTICE

The visual health data was reviewed for subgroup comparison and trend analysis, and did not identify risk factors within this sample group that their VA and visual functioning would impact upon radiography clinical placement tasks and activities. The sample is not generalisable to the wider population; further studies are recommended.