Publication Date




Embargo Period


Degree Type


Degree Name

Doctor of Philosophy (PHD)


Ergonomics (Engineering)

Date of Defense


First Committee Member

Shihab S. Asfour

Second Committee Member

Francesco Travascio

Third Committee Member

Moataz Eltoukhy

Fourth Committee Member

Jean-Marie A. Parel


Photophobia, also called visual photosensitivity is a debilitating symptom and is commonly associated with numerous ophthalmic and neurological pathologies including achromatopsia, dry eye, and traumatic brain injury. The Ocular Photosensitivity Analyzer (OPA), a new automated instrument utilized to quantify the visual photosensitivity thresholds (VPT) in healthy and light sensitive subjects, is described. The Ocular Photosensitivity Analyzer generates light stimuli of varying intensities utilizing unequal ascending and descending steps to yield the visual photosensitivity threshold. Catch trials were integrated within the OPA psychophysical testing paradigm as a performance metric to measure the response reliability of the subject during the OPA VPT measurement session. The OPA longitudinal study revealed that the OPA reliably measured VPT in healthy subjects. The OPA feasibility study evaluated the performance of the OPA in healthy subjects, as well as light sensitive subjects with achromatopsia or traumatic brain injury. Light sensitive subjects manifested significantly lower VPT compared to healthy subjects. The OPA meta-analysis study assessed the VPT of 31 achromatopsia and 43 healthy subjects. Visual photosensitivity was investigated and has been comprehensively assessed using a combination of: (1) psychophysical testing methods utilizing the OPA (VPT, subjective outcome measure) and (2) evaluation of physiological parameters using the OPA post-processing software (OPA PPS): pupil diameter (PD) and palpebral fissure height (PFH) as a function of illuminance (PD and PFH, objective outcome measures). In addition, the Visual Light Sensitivity Questionnaire – 8 (VLSQ-8, subjective outcome measure), a self-reported questionnaire was administered to 25 achromatopsia and 35 healthy subjects, to evaluate the presence and severity of visual photosensitivity symptoms in subjects prior to undergoing OPA testing. Utilizing a variety of validated statistical analyses, each of the above methods has discovered a significant difference between the healthy and achromatopsia subjects. A multiple regression analysis found that both the TYPE of subject and the PDST (pupil diameter prior to stimulus presentation) significantly predicted VPT. Furthermore, the achromatopsia subjects had a lower VPT and higher scores on the VLSQ-8 as opposed to the healthy subjects who had a higher VPT and lower scores on the VLSQ-8. The VLSQ-8 provides an additional assessment tool in determining the presence and severity of visual photosensitivity. The long-term benefits of the dissertation were: (1) to provide clinicians with a portable ophthalmic instrument that can be integrated into the clinic and reliably quantify VPT as well as evaluate physiological parameters (i.e. PD and PFH) as a function of illuminance using the OPA PPS and (2) to provide comprehensive clinical outcome measures (i.e. VPT, PD, PFH, and VLSQ-8) for the diagnostic, predictive, prognostic, and therapeutic assessments of visual photosensitivity.


visual photosensitivity threshold; photophobia; achromatopsia; psychophysical testing; illuminance; outcome measure

Available for download on Saturday, May 01, 2021