Feasibility and outcome of automated static perimetry in children using continuous light increment perimetry (CLIP) and fast threshold strategy

Abstract

ABSTRACT.Purpose: Visual field testing in children is always a challenge as testing is hampered by fatigue effects, easy distraction and lack of comprehension. For that reason new testing strategies for automated perimetry have mainly been evaluated on adults. We tested the feasibility and outcome of automated static perimetry in children in a standard clinical setting. Methods: Twenty-eight children aged 5-14 years were examined at the Twinfield perimeter, including healthy children, children with unilateral pathologies (normal eye tested) and children with strabismus. Fast threshold strategy (FT) and continuous light increment perimetry (CLIP) strategy were used in a randomized order. One eye per subject was examined and each test was performed twice. Results: Reliable results were obtained in many children starting from the age of 8 years. In children aged 13 years and over, adult testing strategies were possible in most cases with good reproducibility. No significant difference was found between the children with strabismus and the other children. Mean sensitivity (MS) increased and fixation losses decreased as a function of age. Continuous light increment perimetry showed a lower number of abnormal fields and fewer false-positive errors compared to FT. Conclusion: Automated static perimetry is possible in many children in a clinical setting using a commercially available Twinfield perimeter in a session of clinically practical duration. Test performance was not only dependent on age, but also on the child's maturity and ability to concentrate. Especially in children up to the age of 8 years, testing with the ramp stimulus (CLIP) was easier than with a staircase strategy (FT).

A Comparison between the Pulsed Rising Amplitude Perimetry and the Normal Staircase Strategy in Standard Automated Perimetry

“…Here, the absolute mean local deviation of the defects, evaluated with the pulsed RAMP (r=0.38), differed considerably and in cases with more advanced visual field defects was more pronounced and showed more outliers than with the NS. Therefore, and in analogy to previously reported results on CLIP strategy [10,11], we assume the higher sLV of the pulsed RAMP to be related more to the difficulty of estimating the thresholds, using patient's reaction times, compared to either continuous RAMPs or pulsed RAMPs with step sizes of 4 dB threshold evaluation.…”

“…Previous studies, concerning the RAMP and its modification -the CLIP -, show the influence of a stimulus duration longer than 200 ms on the temporal summation, and thus on the scotoma depth, when compared to the regular short stimulus pulse [10,11,[13][14][15][16]. In this study, we tested a new RAMP strategy using discrete stimuli of increasing luminance with a stimulus duration of 100 ms and an inter stimulus interval of 600 ms.…”

“…With longer stimulus duration, compared to the usual 100 ms or 200 ms, the temporal summation in SAP results in an increase in threshold [2,10,11,[13][14][15][16]. Therefore here, the difference between abrupt-and continuous onset stimuli seems to be a key factor affecting thresholds.…”

“…In order to compare the pulsed RAMP to the NS, the RAMP influences the threshold determination while presenting higher thresholds [10,11,13,14].…”

“…The rising amplitude perimetry (RAMP) and its modification -the continuous light increment strategy (CLIP) [10,11], in contrast to the TOP strategy, is assessing every single test location independently. Here, the slow temporal onset algorithm starts from invisible (subthreshold) light and increases in luminance until the patient responds to the light.…”