Perimetrie

Perimetrie, or perimetry, is a diagnostic method used in ophthalmology to measure the visual field, the area a person can see without moving the eyes or head. It maps retinal sensitivity to light stimuli across central and peripheral regions and helps identify scotomas, field defects, and changes over time. Perimetry is important for detecting and monitoring diseases that affect the optic nerve or cortical pathways, most notably glaucoma, but also various retinal and neurological conditions.

Perimetry methods are broadly divided into kinetic and static approaches. In kinetic perimetry, stimuli are moved from non-seeing to seeing areas along predefined paths, and the border of vision is mapped (isopters). In static perimetry, the patient fixes gaze on a central point while stationary stimuli of varying brightness are presented at fixed locations to determine threshold sensitivity. Modern instruments are automated and often use infrared fixation targets, delivering standardized test patterns and recording responses automatically.

Common test patterns include the 24-2 and 30-2 programs, which sample a grid of test points across the central and mid-peripheral visual field, and the 10-2 program for detailed central vision. Stimuli come in different sizes and intensities, with algorithms such as SITA (Swedish Interactive Threshold Algorithm) or full-threshold procedures determining the light levels at which stimuli are detected. Results are displayed as numerical indices and as visual field plots, sometimes with glaucoma-specific analyses like mean deviation, pattern standard deviation, and the glaucoma hemifield test.

Indications for perimetry include screening for glaucoma, assessing progression, evaluating unilateral or asymmetric vision loss, and monitoring neuro-ophthalmic or systemic diseases affecting vision. Reliability depends on patient cooperation and fixation stability; results can be influenced by media opacities, fatigue, and cognitive factors.