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Pupillometry in Ophthalmology
Accurate pupillometry is now an essential part of the evaluation, screening, and refractive surgery planning process.
The NeurOptics VIP™-200 Pupillometer is a portable, battery-operated, hand-held device used to measure pupils and screen candidates for refractive procedures and other ophthalmic applications such as the fitting of multifocal intraocular lenses (IOLs).
Accurately measures pupils in darkness for 2 seconds (no background illumination or "Dark" mode);
Instantly and accurately measures, records, and reports average pupil size and standard deviation; accuracy greater than 0.1mm
"Variable" mode measures pupil diameter at variable simulated light levels in one sequence (scotopic, low mesopic and high mesopic) for a total of 10 seconds, allowing clinicians to make the best possible medical decisions for LASIK and premium IOL patients based on pupil size, stated daily activities, and patient preferences.
Has one-button activation
Requires no calibration by the user (just point and shoot)
Provides printed verification
Is pre-operative measurement of the pupils important?
Doctors must define the area of the cornea they will reshape (the optical zone). As the optical zone gets larger, complications from higher order aberrations become more likely. These aberrations are often responsible for post-surgical problems related to night driving such as glare or halos.
The latest article on this topic, "Pupil size and night vision disturbances after LASIK," published in August of 2004, recommended preoperative evaluation of pupil size in all patients prior to refractive surgery because of the correlation the researchers found between large scotopic pupil sizes and the impression of worsened night vision.
Pre-operative pupil measurement has become part of the guidelines for refractive surgery www.eyesurgeryeducation.com/LASIK_Patient_Screening_Guidelines.html published by the ASCRS.
Pupil size measurement during a pre-operative evaluation is particularly helpful for optimizing the premium IOL selection for the patient based on the patient's stated preferences about the level of vision he or she values most (e.g., distance, intermediate or near), occupation, lifestyle, and frequency of nighttime driving. Pupil size affects vision with any IOL, but even more so for so-called "pupil dependent IOLs." An avid reader, for example, especially one who reads in dim light, would be suited for a different premium lens than a golfer. The most pertinent information will be obtained by measuring a patient's pupils under varying light conditions which simulate real life conditions a patient may experience in daily life such as darkness, a dimly lit room, and driving at night with streetlights.
Why the NeurOptics™ Pupillometer?
The NeurOptics™ Pupillometer is consistent from unit to unit and operator to operator. The key to the reproducibility in measurement is the use of NeurOptics' exclusive VIP (Vertex Invariant Pupillometry) technology.
Measurement of the pupil is more difficult than it might seem because of the phenomenon of pupillary hippus or noise. The pupil is never entirely at rest but rather has normal, small continuous oscillations (±0.5mm). Therefore, when trying to measure the pupil, a single "snapshot" estimate is not a reliable predictor of the true mean size (because the clinician might catch the pupil at the maximum or minimum.) The NeurOptics™ Pupillometer records 3 seconds of data to ensure the effects of hippus are minimized. The average size (i.e., ensemble average) as well as the standard deviation of the pupil are reported by the instrument.
Another consideration is the importance of adjusting for differences in the distance from the lens of the Pupillometer to the front of the eye (the vertex distance). Vertex distance can vary up to 12mm in the normal population. This distance affects a pupillometer's calculation of pupil size. If the Pupillometer is not calibrated correctly to adjust for this distance it can create an error up to 20%. A pupillometer should calculate the distance variation to maintain accuracy.
The NeurOptics™ Pupillometer is the only hand-held Pupillometer on the market designed to compensate for vertex distance variance as well as accounting for pupillary noise and reporting an average measurement.
A recent study showed that the NeurOptics Pupillometer has high repeatability and agreement in scotopic pupil diameter for repeated measurements and therefore high safety. (List of studies using NeurOptics® Pupillometer in Ophthalmology.)