Pupillometry has been used in healthy volunteers to investigate the usefulness of the pupil light reflex as an indicator of pain intensity on pressure as a nociceptive stimulus. In this sense, it is necessary to check if the pupillometry is sensitive to different types or sources of pain. One of these devices is the Algiscan® portable pupillometer (IdMed, Marseille, France), which we propose to use in the present study. This pupillometer has previously been used in healthy volunteers, and in patients admitted to the intensive care unit, subjected to mechanical ventilation and sedation / analgesia.

This study in healthy volunteers aims to evaluate whether the PDR can be a reliable and discriminatory measure of the intensity of nociception, applying various types of nociceptive stimuli. If so, this study could lead to the use of pupillometry as an objective measure of nociception in settings where patients cannot communicate, such as intensive care areas or perioperative settings.

Inclusion Criteria:

1. Subjects of both sexes (balanced)
2. Caucasian race
3. Ages between 25 and 65 years old (balanced, 50% from 25-45 and 50% from 45-65)
4. Body weight within the normal range (Quetelet index: 19-30)
5. Clinical history, physical examination and vital signs within normality
6. Free acceptance to participate, with written informed consent

Exclusion Criteria:

1. Previous history of alcoholism or drug dependence (year prior to the screening visit or daily alcohol consumption> 40 gr / day for men or> 24 gr / day for women)
2. Significant consumption of stimulating drinks (> 5 coffees, teas, chocolate or cola drinks / day).
3. Taking any medication in the 15 days prior to the study and / or medicinal plants that may have an effect on the pupil (beta-blockers, droperidol, metoclopramide, clonidine ...). Oral contraceptives and paracetamol will be allowed.
4. Pregnancy (β-hCG test).
5. Menstruation and / or dysmenorrhea on the day of the study
6. Family or personal history or clinical evidence of psychiatric, neurological or ophthalmological problems: anxiety, depression, Parkinson's, glaucoma, dry eyes, retinal diseases, eye surgery and pupil abnormalities, presenting migraine pathology and diabetes
7. Pupillary diameter ≥ 5mm
8. Smokers or ex-smokers <6 months.
9. Have participated in a clinical trial in the 3 months prior to the start of this study.