This tests a square grid of 16 points 2 degrees apart centred around the point of fixation .
It is used to monitor the central field in advanced glaucoma
l Standard full threshold
l SITA :Swedish Interactive Threshold Algorithm
|SITA STANDARD||STANDARD FULL THRESHOLD|
|1.Prior probability model of thresholds based on age corrected values in normal and glaucomatous popln.||1. No such model present|
|2.Use of information index to determine threshold endpoints i.e. it is faster.||2. Thresholds are determined in each points by up-down staircase by 4-2 steps.|
|3.Test pacing is more comfortable.|
|4.Post test computation –greater sensitivity and reproducibility and less intertest variability||4.Not present.|
|5.Fewer catch trials-reduces testing time (time almost of half of SFT)|
|SITA FAST||SITA STANDARD|
|1.At first same process to determine thresholds at 4 primary points-4-2dB step staircase|
|2.If errors are larger ,a single reversal staircase of 4dB is used.(2nd staircase used if value deviates >12dB than expected value)||2.Full staircase 4-2dB is used with two reversals|
|3.Stimulus sequences interrupted earlier by increasing ERF cut off value|
|1. Longer time||1. Half the time of fastpac with same reproducibility|
|2.Glaucoma hemifield test is not available, can not detect early changes.||2.GHT present.|
- compiled & published by Dr Dhaval Patel MD AIIMS
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