A historical review of distance vision screening eye charts: what to toss, what to keep, and what to replace

Omnidirectional Virtual Visual Acuity: A User-Centric Visual Clarity Metric for Virtual Reality Head-Mounted Displays and Environments

Users' perceived image quality of virtual reality head-mounted displays (VR HMDs) is determined by multiple factors, including the HMD's structure, optical system, display and render resolution, and users' visual acuity (VA). Existing metrics such as pixels per degree (PPD) have limitations that prevent accurate comparison of different VR HMDs. One of the main limitations is that not all VR HMD manufacturers released the official PPD or details of their HMDs' optical systems. Without these details, developers and users cannot know the precise PPD or calculate it for a given HMD. The other issue is that the visual clarity varies with the VR environment. Our work has identified a gap in having a feasible metric that can measure the visual clarity of VR HMDs. To address this gap, we present an end-to-end and user-centric visual clarity metric, omnidirectional virtual visual acuity (OVVA), for VR HMDs. OVVA extends the physical visual acuity chart into a virtual format to measure the virtual visual acuity of an HMD's central focal area and its degradation in its noncentral area. OVVA provides a new perspective to measure visual clarity and can serve as an intuitive and accurate reference for VR applications sensitive to visual accuracy. Our results show that OVVA is a simple yet effective metric for comparing VR HMDs and environments.

Effect of Frame Rate on User Experience, Performance, and Simulator Sickness in Virtual Reality

The refresh rate of virtual reality (VR) head-mounted displays (HMDs) has been growing rapidly in recent years because of the demand to provide higher frame rate content as it is often linked with a better experience. Today's HMDs come with different refresh rates ranging from 20Hz to 180Hz, which determines the actual maximum frame rate perceived by users' naked eyes. VR users and content developers often face a choice because having high frame rate content and the hardware that supports it comes with higher costs and other trade-offs (such as heavier and bulkier HMDs). Both VR users and developers can choose a suitable frame rate if they are aware of the benefits of different frame rates in user experience, performance, and simulator sickness (SS). To our knowledge, limited research on frame rate in VR HMDs is available. In this paper, we aim to fill this gap and report a study with two VR application scenarios that compared four of the most common and highest frame rates currently available (60, 90, 120, and 180 frames per second (fps)) to explore their effect on users' experience, performance, and SS symptoms. Our results show that 120fps is an important threshold for VR. After 120fps, users tend to feel lower SS symptoms without a significant negative effect on their experience. Higher frame rates (e.g., 120 and 180fps) can ensure better user performance than lower rates. Interestingly, we also found that at 60fps and when users are faced with fast-moving objects, they tend to adopt a strategy to compensate for the lack of visual details by predicting or filling the gaps to try to meet the performance needs. At higher fps, users do not need to follow this compensatory strategy to meet the fast response performance requirements.

Functional evaluation in inherited retinal disease

Functional assessments are a fundamental part of the clinical evaluation of patients with inherited retinal diseases (IRDs). Their importance and impact have become increasingly notable, given the significant breadth and number of clinical trials and studies investigating multiple avenues of intervention across a wide range of IRDs, including gene, pharmacological and cellular therapies. Moreover, the fact that many clinical trials are reporting improvements in vision, rather than the previously anticipated structural stability/slowing of degeneration, makes functional evaluation of primary relevance. In this review, we will describe a range of methods employed to characterise retinal function and functional vision, beginning with tests variably included in the clinic, such as visual acuity, electrophysiological assessment and colour discrimination, and then discussing assessments often reserved for clinical trials/research studies such as photoaversion testing, full-field static perimetry and microperimetry, and vision-guided mobility testing; addressing perimetry in greatest detail, given it is commonly a primary outcome metric. We will focus on how these tests can help diagnose and monitor particular genotypes, also noting their limitations/challenges and exploring analytical methodologies for better exploiting functional measurements, as well as how they facilitate patient inclusion and stratification in clinical trials and serve as outcome measures.

Comparison of the pediatric vision screening program in 18 countries across five continents

PURPOSE

Incorporating mass pediatric vision screening programs as part of a national agenda can be challenging. This review assessed the implementation strategy of the existing pediatric vision screening program.

METHODS

A search was performed on PubMed, EBSCO host MEDLINE Complete, and Scopus databases encompassing the past ten years for mass pediatric screening practice patterns that met the selection criteria regarding their objectives and implementation. Results were analyzed from 18 countries across five continents.

RESULTS

Eight countries (44%) offered screening for distance visual acuity only, where the majority of the countries (88%) used either Snellen or Tumbling E chart. High-income countries initiated screening earlier and applied a more comprehensive approach, targeting conditions other than reduced vision only, compared with middle-income countries. Chart-based testing was most commonly performed, with only three countries incorporating an instrument-based approach. Lack of eyecare and healthcare practitioners frequently necessitated the involvement of non-eyecare personnel (94%) as a vision screener including parent, trained staff, and nurse.

CONCLUSIONS

Implementation of a vision screening program was diverse within countries preceded by limited resources issues. Lack of professional eyecare practitioners implied the need to engage a lay screener. The limitation of existing tests to detect a broader range of visual problems at affordable cost advocated the urgent need for the development of an inexpensive and comprehensive screening tool.

12 Components of a Strong Vision Health System of Care: Part 2-Vision Screening Tools and Procedures and Vision Health for Children With Special Health Care Needs

Successful vision screening efforts require the implementation of 12 key components of a strong vision health system of care. The National Center for Children's Vision and Eye Health (NCCVEH) at Prevent Blindness partnered with the National Association of School Nurses (NASN) to provide guidance around these 12 components via a Vision and Eye Health webpage on the NASN website ( https://www.nasn.org/nasn-resources/practice-topics/vision-health ). This online resource is organized according to the 12 Components of a Strong Vison Health System of Care to support school nurses accountable for screening the vision of preschool and K-12 students. This NCCVEH/NASN webpage addresses key activities that support a child's vision health-beginning with parent/caregiver education and ending with an annual evaluation of the school's vision health system. Each of these 12 components will be described in NASN School Nurse. The May 2019 installment provided information about the 12 components approach as a whole and details on Family Education and a Comprehensive Communication/Approval Process. This installment describes Components 3 and 4: Vision Screening Tools and Procedures and Vision Health for Children with Special Health Care Needs.

An Eye on Vision: 20 Questions About Vision Screening and Eye Health

Current evidence-based and best practice vision screening and eye health approaches, tools, and procedures are the result of revised national guidelines in the past 3 years and advances in research during the last 16 years. To help the busy school nurse with little time to keep up with changes in children's vision practices and a growing body of literature, the National Center for Children's Vision and Eye Health at Prevent Blindness is providing answers to 20 questions received most often from the field. Question topics are: (1) arranging the screening environment, (2) occluders to cover the eyes during vision screening, (3) optotype-based screening at distance, (4) optotype-based screening at near, (5) instrument-based screening, (6) muscle imbalance screening, (7) referrals, and (8) vision screening certification.

Vision and eye health: moving into the digital age with instrument-based vision screening

Significant advancements in vision screening research are leading to improved design, functionality, and reliability of screening tools. Presently, two vision screening approaches are available to school nurses for children ages 3 years and older: optotype-based screening and instrument-based screening. Optotype-based screening pertains to tests of visual acuity using optotypes (e.g., pictures, letters, and numbers), which children identify to determine visual acuity. Instrument-based screening pertains to automated devices that measure amblyogenic risk factors, such as refractive error, media opacities, and eye misalignment. Differences between the two approaches; best and acceptable practice recommendations for both approaches; unacceptable tests of visual acuity; and best, acceptable, and unacceptable occluders are described.

A near-vision chart for children aged 3-5 years old: new designs and clinical applications

AIM

To introduce a new near-vision chart for children aged 3-5 years old and its clinical applications.

METHODS

The new near-vision chart which combined the Bailey-Lovie layout with a newly devised set of symmetry symbols was designed based on Weber-Fechner law. It consists of 15 rows of symmetry symbols, corresponding to a visual acuity range from 1.3 to 0.1 logMAR. The optotypes were red against a white background and were specially shaped four basic geometric symbols: circle, square, triangle, and cross, which matched the preschool children's cognitive level. A regular geometric progression of the optotype sizes and distribution was employed to arrange in 15 lines. The progression rate of the optotype size between two lines was 1.2589 and two smaller groups of optotypes ranging from 0.7 to -0.1 logMAR were included for repetitive testing. A near visual acuity was recorded in logMAR or decimal, and the testing distance was 25 cm.

RESULTS

This new near-vision chart with pediatric acuity test optotypes which consists of 4 different symbols (triangle, square, cross, and circle) met the national and international eye chart design guidelines. When performing the near visual acuity assessment in preschoolers (3-5 years old). It overcame an inability to recognize the letters of the alphabet and difficulties in designating the direction of black abstract symbols such as the tumbling 'E' or Landolt 'C', which the subjects were prone to lose interest in. Near vision may be recorded in different notations: decimal acuity and logMAR. These two notations can be easily converted each other in the new near-vision chart. The measurements of this new chart not only showed a significant correlation and a good consistency with the Chinese national standard logarithmic near-vision chart (r=0.932, P<0.01), but also indicated good test-retest reliability (89% of retest scores were within 0.1 logMAR units of the initial test score) and a high response rate.

CONCLUSION

The results of this study support the validity and reliability of near visual acuity measurements using the new near-vision chart in children aged 3-5y over a wide range of visual acuities, and the new eye chart was especially suitable for the detection of amblyopia risk factors and low vision examination in children (3-5y of age). It can be applied in routine clinical practice.