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Precision dynamic pupillometry is now a fundamental part of qualification, screening and planning in refractive surgery. Due to iris vibrations and various noises, measuring pupil diameter is more complicated than it might seem. The pupil is never at rest, it performs continuous oscillations with an amplitude of +/- 0.5mm, so an attempt to measure the pupil diameter relying on a single scan is not sufficient to estimate the true average value of the pupil diameter – the examiner may capture the image of the pupil at the minimum, or maximum.

Dynamic Pupillometry allows recording with high temporal resolution (100 measurements per second) and linear resolution (< 0.01 mm) of pupil movement and size and centration using an infrared camera. In addition to traditional systems, consisting of a PC and a measurement part consisting of a chromatic stimulation module, an IR illumination module, a recording module and an analysis module, modern ophthalmology also has handheld pupillometers that compensate for the effects of frontal distance, iris vibrations and other noise on measurement accuracy. Modern handheld pupillometers provide accurate, reliable and objective data on pupil size and reactivity, regardless of the test person.

Why is measuring the pupil diameter so important before eye surgery?

Measuring the diameter of the pupil is so important because the doctor needs to determine what area of the cornea (optical zone) will be modified. With an increase in the size of the optical zone, the risk of complications arising from higher-order aberrations increases. These aberrations are often responsible for glare and halo phenomena during nighttime driving resulting from refractive surgery. Pupillometry measures photopic and mesopic pupillary diameters. Photos of the pupil taken with the device accurately show the shape of photopic pupils (i.e., working under normal conditions, with enough light to fully utilize the capabilities of the sense of sight) and mesopic pupils (so-called twilight vision under transient conditions, i.e., with insufficient light), which can alter refraction and important surgical data.

Dynamic pupillometry in the diagnosis and monitoring of ocular and systemic diseases

Dynamic pupillometry is also a very sensitive method, also determining disorders of autonomic nervous system function.

The function of parasympathetic innervation of the pupil is mainly measured by the following parameters:

  • Output pupil diameter (mm),
  • Time to reach minimum diameter in contraction (s),
  • The amplitude of contraction (mm),
  • relative amplitude of contraction (% of initial diameter)
  • maximum contraction speed (mm/s)

The function of sympathetic innervation of the pupil is best determined by:

  • maximum diastolic velocity (mm/s)
  • 75% diastolic time (s)

The function of parasympathetic innervation of the pupil is mainly measured by the following parameters:

  • Output pupil diameter (mm),
  • Time to reach minimum diameter in contraction (s),
  • The amplitude of contraction (mm),
  • relative amplitude of contraction (% of initial diameter)
  • maximum contraction speed (mm/s)

The function of sympathetic innervation of the pupil is best determined by:

  • maximum diastolic velocity (mm/s)
  • 75% diastolic time (s)

In neuro-ophthalmology, pupillometry is also used to quantify relative afferent pupillary defect (RAPD, relative afferent pupillary defect), estimate visual field spread, assess optic nerve function in glaucomatous neuropathy, in optic neuritis (multiple sclerosis, myasthenia gravis, among others), and evaluation of retinal function in retinitis pigmentosa, central retinal vein occlusion (CRVO), and age-related macular degeneration.

Patients with craniocerebral injuries (subdural hematomas, intracranial injuries) also require pupil function monitoring with a pupillometer.