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Stuart G. Coupland, Vivek R. Patel, John Hamilton; Multifocal Pupillography In Normals And Clinical Population. Invest. Ophthalmol. Vis. Sci. 2011;52(14):266.
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Objective perimetry using the pupil light reflex has been well investigated and offers promising potential. Herein, we describe a technique using m-sequence stimulation technique with mutifocal pupillography to provide objective perimetric mapping in normals and in patients with demonstrated visual field defects.
Multifocal pupillography was performed using a standard VERIS multifocal ERG system with a fundus stimulator/camera. The stimulus consisted of either 19 or 37 hexagonal elements within a 45 degree field. The stimulus presentation duration was 120 msec per frame and an m-sequence=11 was used. Pupil size was monitored from the fundus stimulator/camera system and aided by an infrared LED source. The system was interfaced with another computer and changes in pupil size were recorded in real-time at a 10 Hz sampling rate. The software determined pupil size based on the number of black pixels located within the pupil margin which was depicted by a white circular outline using a Circle Hough Transform. Pupil size was then converted into a proportional voltage change (+5 to -5 V). The voltage representing pupil size was sent to the VERIS system for m-transform analysis and the first order kernel was displayed. Multifocal pupillography was performed on 20 normal subjects and 10 patients with lesions of the optic nerve and higher visual pathways.
In 20 normal subjects, the resulting 19 pupillographic traces were grouped in quadrants and rings. The foveal pupillogram had a peak latency of around 570 msec. in normal subjects. There was a characteristic decrease in pupillographic trace amplitude with increasing retinal eccentricity, this was confirmed by ring analysis which showed significant decrease in constriction amplitude in outer rings (p < 0.05). There was also significant decrease in constriction peak latency in the outer rings (p< 0.05). Constriction amplitude was significantly larger in the temporal versus nasal field (p< 0.05). No significant difference was found in constriction amplitude between superior and inferior visual fields. In patients with history of retrobulbar optic neuritis there was markedly reduced central response associated with delayed peak timing.
Multifocal pupil perimetry using the m-sequence produces reliable responses whose constriction timing and amplitude are consistent with retinal ganglion cell topography. Multifocal pupil perimetry has potential for objective perimetry.
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