for people ages 18 years and up (full criteria)
Healthy Volunteers
healthy people welcome
study started
estimated completion
Principal Investigator
Gerami D Seitzman, MD (ucsf)



The purpose of this study is to determine if there are microbiologic alterations of the ocular surface after hot tub exposure. The study will evaluate the number of microbes before and after hot tub use in order to find out whether hot tub exposure has any change on the organisms present on the ocular surface. Participants will be randomized to dunk or not to dunk their head during their time in the hot tub.


Keratitis is a rare destructive cause of blindness. It typically affects young and healthy individuals, is excruciatingly painful, and difficult to treat. With 60% of cases mis-diagnosed at presentation, acanthamoeba keratitis carries a far worse visual prognosis compared to other cornea infections. Exposure to hot tubs is a widely accepted risk factor. However, the mechanism of infection and prediction of who is at risk is unknown as the vast majority of hot tub users do not become infected.In vivo changes to ocular microbiology after hot tub exposure has never been described.

Changes to ocular microbiology after exposure to hot tubs have not been described. The purpose of this study is to investigate whether there are significant alterations in the microbiology of the conjunctiva after hot tub exposure that may contribute to these changes.

This study will recruit at least 34 subjects, who will be randomized to head submersion versus no head submersion, using at least three different hot tubs. A conjunctival swab, a minimal-risk test performed routinely in the eye clinic, will be performed before and after 15 minutes of hot tub exposure on one eye (randomized) per subject. The swabs will be plated on blood agar (bacterial cultures) and non-nutrient agar (acanthamoeba cultures).

In this prospective study, healthy subjects will be recruited. The study will be Health Insurance Portability and Accountability Act compliant and approved by the Institutional Review Board. All subjects will review and sign an informed consent form.

Each patient will have the conjunctiva of one eye (randomized) cultured. This practically no-risk technique entails touching a polyester-tip swab to the lining of the lower eyelid. Each subject will be randomized to head submersion or no head submersion; this exposure will be masked by the study coordinator. After 15 minutes of hot tub exposure, the subject will have the same eye swabbed for cultures.

Each sample (pre- and post-hot tub) will be randomly assigned a study number. One study coordinator will record and mask data. Water from each tub will be cultured.

The culture plates will be sent to our microbiology facility at UCSF and identification of organisms on the blood agar plates will be performed on our MALDI (mass spectrometry to identify bacteria and fungi). Non-nutrient agar plates will be plated with E. coli overlay and incubated for up to 7 days. The plates will be randomized and the microbiologists will be masked to exposures.


Conjunctivitis, Bacterial Keratitis Bacterial hot tub conjunctival cultures bacterial keratitis Conjunctivitis Keratitis Dunk Exposure to Hot Tub Head Dunk


You can join if…

Open to people ages 18 years and up

  • greater of 18 years of age
  • a willing participant
  • healthy

You CAN'T join if...

  • pregnancy
  • high or low blood pressure
  • active diarrhea
  • lymphedema
  • heart disease
  • seizure disorder.


  • UCSF accepting new patients
    San Francisco California 94122 United States

Lead Scientist at UC Health

  • Gerami D Seitzman, MD (ucsf)
    Gerami Seitzman, MD is an Associate Professor of Ophthalmology at the University of California, San Francisco. She is a cornea and external disease specialist at the F.I. Proctor Foundation. She also sees general ophthalmology patients in the comprehensive division of the UCSF Department of Ophthalmology.


accepting new patients
Start Date
Completion Date
University of California, San Francisco
Study Type
Last Updated