Technical aspects of static perimetry in the diagnosis of glaucoma

Relevance Glaucoma is a chronic neurodegenerative disease leading to irreversible blindness. Static perimetry is considered the "gold standard" for monitoring and diagnosing glaucoma. Today, the Octopus perimeters (Haag-Streit Diagnostics, Switzerland) and Humphrey Field Analyzer (Carl Zeiss Meditec, Germany) are considered the best in functional diagnostics [1]. The visual field is the angular space visible to the eye during a fixed gaze. It is divided into three zones: macular - within 8° from the fixation point, central - at 30° and peripheral - from 30°. In glaucoma diagnostics, the 30-2 and 24-2 HFA perimeter programs and the 32 and G-program for Octopus perimeters are used [2–4]. Programs 30-2 and 32 examine 76 and 74 points in a 30° zone, evenly distributed with the same distance between them of 6°. Program 24-2 is faster, in it the number of points is reduced to 54 due to the narrowing of the study zone in all meridians except the nasal. Also, the result of this program is less affected by the projection of the corrective glass frame. Also, for monitoring glaucoma patients, the program 10-2 HFA perimeter can be used, it is more detailed in assessing the central zone of the visual field. Static perimetry is carried out by presenting stationary white stimuli of different brightness on an illuminated background. The physical unit of measurement of stimulus brightness and background illumination is apostilb (asb). Currently, the standard background brightness is 31.5 asb due to achieving an optimal pupil diameter of 3.5 mm, no need for dark or light adaptation of the patient and achieving minimal photopic vision [5]. To determine the photosensitivity of the retina, it is customary to convert physical units of asb into physiological ones - decibels (dB), which are on an inverse logarithmic scale. The brightness range of the supplied stimuli varies from 0 dB (10,000 asb) to 51 dB (0.08 asb). During standard testing, a stimulus of size III according to Goldman (4 mm2) is supplied from 0.1 to 0.2 s. With low visual acuity, a stimulus of size V according to Goldman (52 mm2) is supplied for 0.2 s. Currently, the "gold standard" is the SITA algorithm. There are SITA Standard (SS) and SITA Fast (SF). SS is a more in-depth algorithm that takes 6-8 minutes, SF is no less high-quality, but requires more control and patient attention, so it is suitable for young patients. Conclusion Computer perimetry is the main method for diagnosing and assessing the progression of glaucoma. Key words: static perimetry; glaucoma; HFA; visual field