## 1 Introduction  
USN (unilateral spatial neglect), a condition characterized by an impaired ability to perceive visual information in the space contralateral to the damaged hemisphere following brain damage, is commonly caused by stroke [1, 2]. In particular, USN occurs in approximately 50% of patients who have suffered an acute stroke and is often manifested as left-sided neglect resulting from damage to the temporal and frontal lobes of the right hemisphere [3, 4]. Right-sided neglect caused by damage to the left brain has also been reported [5]. UN (unilateral neglect), including USN, is classified as motor neglect or sensory neglect according to the type of deficit [6, 7]. Due to a lack of awareness of space contralateral to the side of the brain that has been damaged, patients with UN experience difficulties in performing daily activities. They typically leave food on the opposite side of the damaged brain untouched during meals, frequently bump into objects, and have problems reading and writing [8, 9]. In addition, sitting or standing balance can be difficult for UN patients and there is an increased risk of falls [10]. Therefore, UN treatment and rehabilitation are critical for a patient's recovery to an independent daily life.  
The occurrence of UN is a result of complex causes in the cerebrum, and the approaches to the treatment of UN include medication therapy, promotion of sustained arousal and attention, neck vibration, neck electrical stimulation, eye patching, and wearing prism glasses [10]. Of these, prism adaptation, a bottom-up approach classified by [PERSON] et al. [11], changes the external environment using prism refractive power towards the direction of the base, which is helpful for improving perception; this method is the most commonly examined therapeutic approach for UN, and the efficacy of wearing prism glasses has been previously demonstrated [12; 13]. Research on a large number of assessment tools for the diagnosis of UN is currently underway [14]. Among the assessment tools, the pen-and-paper test is used most often because of its convenience. The types of tests include the line bisection test, copying and drawing test, and cancellation test [14; 15]. In particular, when compared with other tools, the cancellation test is preferred for the diagnosis of UN [16]. [PERSON] et al. [17] reported the development of a cancellation test, which was later modified by [PERSON] et al. [18], which involved the replacement of the stimulus shape with an apple shape. The apple cancellation test can enhance patients' interest in the test, leading to a more accurate determination of UN. This test has recently attracted significant attention for distinguishing between two different types of UN, EN (egocentric neglect: missing information in the space opposite the brain injury centered on the viewer) and AN (allocentric neglect: missing information in the space opposite the brain injury centered on the object) [19].  
However, the apple cancellation test is a subjective test conducted in the form of a pen-and-paper test where the subject looks directly at the evaluation sheet. Nevertheless, no reference for conditions for the correction of visual acuity prior to the test has been specified. The use of the method for the correction of visual acuity (for distance or near visual acuity) may cause errors in test results due to the use of different corrective refractive powers for the correction types. Therefore, this study examined the effect of conditions for the correction of visual acuity on the diagnosis of UN syndrome caused by brain diseases such as stroke and provides guidelines for the correction of visual acuity that can be referenced for use in the performance of pen-and-paper tests. We hope that the information provided in the study will be helpful for professionals in the field.