Smaller Fixation Target Size Is Associated with More Stable Fixation and Less Variance in Threshold Sensitivity.

The aims of this randomized observational case control study were to quantify fixation behavior during standard automated perimetry (SAP) with different fixation targets and to evaluate the relationship between fixation behavior and threshold variability at each test point in healthy young participants experienced with perimetry. SAP was performed on the right eyes of 29 participants using the Octopus 900 perimeter, program 32, dynamic strategy. The fixation targets of Point, Cross, and Ring were used for SAP. Fixation behavior was recorded using a wearable eye-tracking glass. All participants underwent SAP twice with each fixation target in a random fashion. Fixation behavior was quantified by calculating the bivariate contour ellipse area (BCEA) and the frequency of deviation from the fixation target. The BCEAs (deg2) of Point, Cross, and Ring targets were 1.11, 1.46, and 2.02, respectively. In all cases, BCEA increased significantly with increasing fixation target size (p < 0.05). The logarithmic value of BCEA demonstrated the same tendency (p < 0.05). A positive correlation was identified between fixation behavior and threshold variability for the Point and Cross targets (ρ = 0.413-0.534, p < 0.05). Fixation behavior increased with increasing fixation target size. Moreover, a larger fixation behavior tended to be associated with a higher threshold variability. A small fixation target is recommended during the visual field test

Typical Example of Fixation Behavior among the Three Fixation Targets.

<p>(Top) Fixation behavior of the visual field within 30° and (Bottom) expanded within 5°.</p

Schematic of Tobii Glass I.

<p>The wearable eye-tracking glasses consist of a camera with a resolution of 640×480 pixels mounted on the right temple, which records the eyesight of the participant; it also includes a pupil detection camera with a sampling frequency of 30 Hz located on the right temple of the glasses for recording the participant’s fixation.</p

Study Protocol in this prospective observational case control study.

<p>Study Protocol in this prospective observational case control study.</p

Sizes of the Point, Cross, and Ring Fixation Targets.

<p>The internal diameters and external diameters are presented for the Cross and Ring marks.</p

Comparison of Fixation Behavior and its Frequency among the Point, Cross, and Ring Targets.

<p>Comparison of Fixation Behavior and its Frequency among the Point, Cross, and Ring Targets.</p

Participant Demographic and Ocular Characteristics.

<p>Participant Demographic and Ocular Characteristics.</p

Relationship between Fixation Behavior and Threshold Sensitivity.

<p>(Top) Scatter plots of the relationship between the root mean square error (RMSE) at each test point and the bivariate contour ellipse area (BCEA). (Bottom) The relationship between RMSE and log(BCEA). Correlation coefficients (ρ) were calculated with Spearman's rank correlation coefficient.</p