Biography
Dr. Ping Situ is currently an associate scientist at the Indiana University School of
Optometry (IUSO). She gained her MSc, and then PhD (under supervision of Dr. Trefford Simpson) in
Vision Science at University of Waterloo. She joined Dr. Carolyn Begley’s Dry Eye Research team at the
IUSO in 2012 after many years of clinical research experience at the Center for Contact Lens Research
(presently CORE) University of Waterloo. Her research interest has been on understanding the
neurological basis contributing to ocular surface sensation. To address this question, she uses a
combination of psychophysical, physiological and imaging approaches to study the roles of sensory
function of the ocular surface in dry eye disease and contact lens discomfort, and the impact of tear film
dynamics on ocular surface sensation.
Abstract
Corneal sensory nerves play a vital role in maintaining the homeostasis of the ocular surface
and the tear film, both of which are major optical components of the eye. While neurosensory
abnormalities are recognized as pathophysiological factors in DED and CLD, the exact sensory origins of
ocular discomfort and dryness associated with dry eye (DED) and contact lens wear (CLD) remain poorly
understood. Stimulation from the ocular surface and tear film can alter corneal sensory function and
induce adaptive plasticity in sensory pathways; however, these alterations may also result in maladaptive
plasticity. These changes in sensory function can complicate the relationship between DED symptoms
and clinical signs, such as cellular damage that does not fully align with symptoms, as seen in cases of
“pain without stain” and “stain without pain.” Our research focuses on understanding the link between
corneal sensory functions and the physical stimuli to the ocular surface, such as tear film instability and
contact lens wear. In this talk, I will discuss the effects of short-term and longer-term ocular surface
stimulation on sensory functions. Using the IU Belmonte esthesiometer, we investigated changes in
corneal sensory function in response to contact lens stimulation, comparing individuals who experience
CLD with those who do not. In addition, we employed a human-based DED model called STARE
(Sustained TeAR Exposure) to induce repeated tear film breakup (TBU) and mimic DED symptoms. The
ocular surface stimuli during STARE were evaluated using fluorescence and thermal imaging with
machine learning and mathematical modeling approaches while the sensory responses were assessed
through psychophysical methods. Our findings indicate that altered corneal sensory function associated
with contact lens wear and tear film breakup contribute to the sensations of ocular discomfort and
dryness in CLD and DED.
