1. AUTOMATED PERIMETRY DR.JYOTI SHETTY MEDICAL DIRECTOR BANGALORE WEST LIONS EYE HOSPITAL, BANGALORE

2. BASIC CONCEPTS Traquair's has defined the visual field as been a hill island of vision in a sea of darkness testing along X-Y axes of this 3 dimensional area determines the location in the visual field and along the Z axis identifies the visibility threshold. X - Y axis - kinetic perimetry Z axis - static perimetry Automated Perimetry - " Differential light threshold –Ability to differentiate an illuminated target against an illuminated background." Threshold Perimetry - Modality of choice

3. BASIC CONCEPTS --- contd THRESHOLD Luminance of stimuli that is seen 50% of times it is presented Logarithmic unit dB ( dB prop. 1 / brightness ) Bracketing strategy ( 4 - 2 - 2 algorithm ) Supra threshold - 95 % chance a stimulus is seen. Infra threshold - 5% chance a stimulus is seen.

4. BASIC MACHINE DESIGN Illuminated hemispherical bowl 33 cm away with target of fixation Stimuli - spot of light - LED / Projection system / Comp. Video monitor HFA - II ( 700 Series ) Aspherical bowl 30 cms away,smaller,more ergonomic stimuli in periphery more closer, programmed to decrease stimuli brightness (4dB).

5. FIXATION CONTROL CC TV monitor Heijl - Krakau Blind spot method Gaze tracker –Full time two variable Gaze monitor –Image analysis –Errors - upward / downward –Fixation checked 100 % of stim. Time –No testing time for fixation check

6. Basic software design Strategies for threshold detection – Intensity of the stimulus presented at a given point is related to the normal threshold at that stimulus site. Bracketing strategies to define threshold at any point. 4-2-2 algorithm SITA

7. INFORMATION DISPLAY Numeric data display actual dB value at each point Gray scale – range of decibels and their corresponding luminance Difference / Depth defect – actual value is arithmetically subtracted from a presumed expected field.

8. Parameters recommended for testing Foveal fixation target – small and large diamond with yellow lights. Goldmann size III target for stimuli & blind spot check. If excessive fixation loss it can be decreased to II or I or if vision less than 6/36 than it can be increased to V. White stimulus colour Normal testing speed. can be slow down if patient is slow to response. Foveal threshold - ON / OFF

9. Threshold tests Central 30-2 – 76 points are tested. Each point 6 deg apart. Straddling the horizontal and vertical axis so that the 2 inner most test points are 3 deg from fixation point. Central 24-2 – 56 points are tested. Avoids rim artifacts. Central 10-2 – 68 points space 2 deg apart. Useful in advance disease with spilt fixation. Macular threshold test – square grid of 16 points each 2 deg apart, with each point thresholded 3 times.

10. 30 – 2 24 – 2 Macular threshold

11. INTERPRETATION Factors for consistency in testing Best Refractive correction used. Contact lens to avoid rim artifacts. Pupil Diameter – at least 3.5 mm in size. Visual Acuity Date & Time of testing Age-For comparison with normative data Short term fluctuation-Fluctuation occurring within the test. Should be <3dB.

12. INTERPRETATION ----contd. Reliability of patient Fatigue, anxiety and learning effect Fixation loss – should be less than 20% False positive and negative response should be less than 33%.

13. Statistical global indices MD – mean deviation – sensitive to total loss PSD – pattern standard deviation – sensitive to localized loss. CPSD – corrected pattern standard deviation – PSD corrected for short term fluctuation. Very sensitive index.

14. Glaucoma defect with automated perimetry- Anderson's Criteria 3 or more cont.non edge points with >= 5 dB loss 2 or more cont. non edge points with >=10 dB loss Diff. of 10 dB across nasal hor. meridian at 2 or more adj. points ( nasal step.) GHT - ONL PSD plot - >= 3 pts, p< 5% of which one < 1% CPSD ( p <5% ) GHT ONL

15. INTERPRETATION ----contd. Progression of defect Test parameters comparable Defect - increased in size / depth >= 7 dB increase in depth of existing defect >= 9 dB depression adj. to abnormal point >= 11 dB depression of a normal point ( New Defect ) Box plot change analysis Overview Glaucoma change probability analysis

16. SWAP Tests subset of Ganglions affected earlier & selectively -- Blue / Yellow Reduces the redundancy of responsiveness to stimuli Intense yellow background - bleaches green / red cones Blue stim. ( 440nm ) - isolates blue cones Adaptation - 3 mts. Room illumination - minimal Stimulus size & BS check size V Mean threshold values lower than SAP - Gray scale darker Stat Pac probability plots more reliable

17. SWAP -- contd Field defect precedes SAP by >= 3 yrs Once abnormal - remain abnormal ( no recovery of damaged blue cones ) No role in advanced POAG / advanced lenticular changes / colour vision abnormalities Most useful in younger Glaucoma suspects, OHT, POAG with mild to mod.damage Time consuming - SITA optimised for SWAP / Fast Pac can be used