The redevelopment of the Kay picture test of visual acuity

Abstract

Aims: To validate the design of updated optotypes to be used in the Kay picture acuity tests to improve the resolution acuity, recognition, repeatability and comparisons with gold standard logMAR acuity assessments. Methods: The study was completed in four phases. In all phases the pictures were presented on a monitor as a single crowded optotype, with five optotypes at each visual acuity (VA) level. Phase one assessed the resolution acuity for 25 pictures, eight Landolt Cs and five ETDRS letters. The recognition phase (phase two) assessed children (18 months to 5 years) to determine which pictures were most commonly identified. During phase three, the resolution acuity of a reduced number of pictures and the Landolt C were reassessed to ensure that fatigue had not influenced the initial results. Phase four compared the new Kay pictures with LEA symbols and the ETDRS (part a), and repeatability of the Kay pictures and the ETDRS chart (part b). Results: Phase one (resolution acuity): 50 adult subjects were tested. The mean (ÔSD) acuity scores achieved using each of the 25 pictures ranged from À0.123 Ô 0.124 to À0.308 Ô 0.105. The mean (ÔSD) acuity for the eight Landolt C orientations was À0.059 Ô 0.120, and À0.128 Ô 0.101 for the ETDRS letters. Following this analysis, three pictures were removed. Phase two (Recognition): 420 children were assessed (54% male) using the remaining 22 pictures. Analysis resulted in the removal of 10 pictures based on the recognition levels. Phase three (resolution acuity): 43 adult subjects were tested with the remaining 12 pictures. The picture selection was reduced to six based on a combination of similar mean bias levels, recognition levels in all children and recognition levels in the youngest children. Phase four (a) (comparability): 113 adult subjects were tested. The mean bias indicated similar results between the tests. The limits of agreement for ETDRS versus Lea symbols were slightly wider than for ETDRS versus Kay pictures. Phase four (b) (repeatability): 100 adult subjects were tested. Paired t-test analysis demonstrated no significant difference between tests in either ETDRS (p = 0.1) or Kay pictures (p = 0.1). Mean bias for both tests was 0.01 logMAR with similar limits of agreement. Conclusion: The newly designed Kay picture optotypes have been shown to be reliably recognised by a paediatric population. In a six-picture test format the newly designed optotypes with single picture presentation and crowding bars have been shown to be a reliable and repeatable VA test in an adult population with good agreement with current gold standard VA assessment methods. Normative data in a paediatric population are now required.

The Auckland Optotypes: An open-access pictogram set for measuring recognition acuity

“…Starting with enclosed shapes and intentionally limiting acute angles and internal lines reduced the presence of high contrast regions that can arise in vanishing Sloan letters (e.g., at line endings or junctions), further reducing interoptotype variability. This feature of the proposed optotype set is an additional advantage over other well designed pictogram sets (for example Lea symbols [Hyvarinen et al, 1980] and the newly designed Kay pictures [Milling et al, 2016]), adding a level of flexibility to the type of testing which can be done. For example, since vanishing optotypes may be helpful for monitoring visual loss arising from macular degeneration (Shah et al, 2016), having a set of 10 vanishing optotypes that do not rely on the familiarity with Roman letters could be useful in a culturally diverse clinical setting.…”

“…For adults with poor reading skills, or for whom language prevents use of standardized symbols, this group of 10 pictograms allows equity with the current 10-alternative standard for acuity testing. Paediatric optotype tests tend to use smaller numbers of alternatives (typically four [Hyvarinen et al, 1980;Holmes et al, 2001], six [Milling et al, 2016], or eight [Kay, 1983]). Although the increased number of symbol alternatives in TAO has the potential to increase test efficiency, whether this translates to a benefit when testing children remains to be seen, particularly as increased alternatives can increase indecision and cognitive load.…”

“…Some of these challenges have led to recent interest in redesigning picture optotypes, as seen in the new version of the Kay pictures (Milling, Newsham, Tidbury, O'Connor, & Kay, 2016). Although an encouraging development, these symbols are only available commercially, which limits their access by clinicians and researchers.…”

Parental Home Vision Testing of Children During Covid-19 Pandemic

“…Home vision testing applications (apps) exist and have been validated for use by healthcare professionals (Bastawrous et al 2015;Milling et al 2015;Zhao, Stinnett & Prakalapakorn 2019). They are not used in our routine clinical practice, by parents, or carers.…”

Grouping Effects on Foveal Spatial Interactions in Children

“…14 Vision charts in which a target is surrounded by flankers are recommended for children's vision screening programs to detect amblyopia, 25,26 as crowding is exaggerated if strabismus is present. [27][28][29][30][31] In currently available tests, targets are flanked by a box, [32][33][34] bars, 35 or other letters, 36 but these flanking features can have different effects on visual acuity in adults 4 and children. 37 Compared to effects of simple contours such as a box or bars, other letters placed around a target letter can lead to stronger interactions.…”