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The Research of Gwen Musial

Gwen Musial

Personal Background:

I studied biomedical engineering for both my bachelor’s degree (University of Rochester, NY, USA) and my PhD (University of Houston, TX, USA) with a focus on biomedical imaging. My research focus during both degrees was on retinal imaging. I was first introduced to high-resolution retinal imaging by a summer internship in the lab of Dr. Alfredo Dubra in 2013. I was fascinated by the ability of adaptive optics scanning laser ophthalmoscopes (AOSLO) to non-invasively image individual photoreceptors. I continued working in an adaptive optics research group for my graduate thesis under the supervision of Dr. Jason Porter. For this work, I used an AOSLO with a novel split detection set-up to examine the capillaries around the optic nerve head throughout experimental glaucoma. After spending eight years in the world of retinal imaging,

I decided to take a new position at the University of Cologne as a PI in DFG Research Unit 2240 ( for the Cologne Experimental Eye Imaging Center where I work on projects that image the cornea. Additionally, I have the great opportunity to be a co-supervisor in the EU Marie Curie Action IT-DED3 (Integrated Training in Dry Eye Disease Drug Development) program. In the vision science research world, it sometimes feels like retinal research and corneal research are working on solving problems in different organs despite the fact that both the neuroretina and the cornea are multi-layered optically transparent structures. Corneal imaging has historically not received the same amount of research attention as retinal imaging developments; however, corneal imaging does have unique opportunities for advancements in clinical care, pharmacology development, and more.

Current Research Background:

In the healthy eye, the transparent cornea refracts light and forms a barrier which defends the eye from chemical, biological, and mechanical insults from the environment. The tight junctions between basal corneal epithelium cells, the outermost layer of the cornea, is the primary component of this barrier system [1]. If the corneal epithelium barrier becomes disrupted from chemicals or disease, the transparency of the cornea can become compromised leading to diminished vision.

Clinically, the cornea epithelium can be assessed by fluorescein staining [2], which is applied to the ocular surface and indicates areas of increased permeability in corneal epithelium and illuminates foreign bodies (Figure 1). This test is simple to perform and is very useful in assessing diseases such as dry eye disease. However, this test is non-specific and does not give detailed information about the structure of the epithelium cells or the status of their health.

Experimentally, the corneal epithelium response to drugs and chemics can be assessed using cell culture assays. These tests place cultured, single/or multi-layered corneal epithelium cells in a tissue dish with media containing the chemical to be tested. Then, different assays can detect if the cells dislodge from the tissue dish or if the cells die [3]. These tests are helpful to see if a chemical severely impacts the corneal epithelium cells but do not fully mimic the multi-layered structure of the cornea epithelium and how it would respond to a chemical insult. In-vivo tests with animal models are a solution, however, current testing methods do not evaluate subtle changes of the health of the cells at the ocular surface [4].

There is a need for a specific and non-invasive method that can determine the health of corneal epithelium cells in a living eye. An optical technique, such as optical coherence tomography (OCT), is a promising candidate as devices are already clinically available that can already image the cornea and be used to determine the thickness of the corneal layers. However, these devices lack the resolution and contrast to image the different layers of the corneal epithelium or the individual cells. A new technique called microscopic OCT (mOCT), leverages the high lateral resolution of microscope objectives and the high axial resolution of OCT [5], paired with post-processing software called dynamic contrast intensity [6], could be the next step forward in corneal toxicity testing and evaluation of diseased corneas.

Figure 1. Fluorescein staining in highly diseased eye. Conventional clinical analysis of an eye with this amount of staining indicates that the cornea epithelium barrier function is impaired. Unpublished figure courtesy of UniKlinik Kӧln AugenKlinik.

Dynamic Contrast Intensity microscopic Optical Coherence Tomography (DCI-mOCT) as a novel method of evaluating ocular toxicity:

The first step in establishing a new method for evaluating ocular toxicity is to ensure that images and quantification metrics can be consistently acquired in healthy tissue. A conventional OCT B-scan of a healthy mouse in-vivo (Figure 2A) shows the cornea epithelium across the whole eye, while only a sub-section of the cornea, shown with a red box in Figure 1A, can be captured in a single B-scan with the mOCT system (Figure 2B). The higher resolution in the mOCT b-scans come at the cost of total area covered, yet even with this increased resolution, the individual cells are not visible in a single B-scan. If multiple B-scans are acquired at the same location, then different processing algorithms can be applied to reveal different structures.  Conventional processing algorithms over these B-scans, like maximum intensity projection (Figure 2C) and standard deviation (Figure 2D), result in images with higher signal-to-noise ratio and better cell resolution. But, dynamic contrast intensity processing (Figure 2E) results in images that clearly resolve the individual corneal epithelium cells. This contrast enhancement is achieved by converting the stack of B-scans to the frequency domain using a Fourier transform, binning the frequencies into high, mid, and low frequencies, then summing the frequencies in these bins to form the red, green, and blue channels in an RGB image [7]. The enhanced contrast images enable segmentation of the superficial and basal layers of the epithelium. Then, different cell viability metrics, motility coefficient and decorrelation time, can be analyzed within the whole epithelium and separated by the superficial and basal layers.

Figure 2. Dynamic contrast mOCT shows individual epithelium cell structure better than conventional OCT and convention mOCT processing. A) Conventional anterior chamber OCT B-scan in mouse. Red box shows area covered by mOCT B-scan. Scale bar 100 µm. B) Single mOCT B-scan. Scan bar 100 µm. C) Maximum intensity projection of 150 mOCT B-scans. D) Standard deviation image across 150 mOCT B-scans. E) Result of dynamic contrast intensity processing over 150 mOCT B-scans. Unpublished figure.

The second step in establishing a new method for evaluating ocular toxicity is to ensure that images and quantification metrics can be consistently acquired in dead and severely injured tissue. The third step in establishing a new method for evaluating ocular toxicity is to ensure that images and quantification metrics can be consistently acquired after exposure to a substance that is known to be toxic to the corneal epithelium cells. This work is currently being prepared for publication.


  1. M. Sosnová-Netuková, P. Kuchynka, and J. V. Forrester, “The suprabasal layer of corneal epithelial cells represents the major barrier site to the passive movement of small molecules and trafficking leukocytes,” Br. J. Ophthalmol., vol. 91, no. 3, p. 372, Mar. 2007.
  2. M. C. Holland, “Fluorescein Staining of the Cornea,” JAMA, vol. 188, no. 1, pp. 81–81, Apr. 1964.
  3. A. Iwasawa, M. Ayaki, and Y. Niwano, “Cell viability score (CVS) as a good indicator of critical concentration of benzalkonium chloride for toxicity in cultured ocular surface cell lines,” Regul. Toxicol. Pharmacol., vol. 66, no. 2, pp. 177–183, Jul. 2013.
  4. A. Secchi and V. Deligianni, “Ocular toxicology: the Draize eye test,” Curr. Opin. Allergy Clin. Immunol., vol. 6, no. 5, pp. 367–372, Oct. 2006.
  5. J. Horstmann, H. Schulz-Hildebrandt, F. Bock, S. Siebelmann, E. Lankenau, G. Hüttmann, P. Steven, and C. Cursiefen, “Label-free in vivo imaging of corneal lymphatic vessels using microscopic optical coherence tomography,” Investig. Ophthalmol. Vis. Sci., vol. 58, no. 13, pp. 5880–5886, Nov. 2017.
  6. C. Apelian, F. Harms, O. Thouvenin, and A. C. Boccara, “Dynamic full field optical coherence tomography: subcellular metabolic contrast revealed in tissues by interferometric signals temporal analysis,” Biomed. Opt. Express, vol. 7, no. 4, p. 1511, 2016.
  7. M. Münter, M. vom Endt, M. Pieper, M. Casper, M. Ahrens, T. Kohlfaerber, R. Rahmanzadeh, P. König, G. Hüttmann, and H. Schulz-Hildebrandt, “Dynamic contrast in scanning microscopic OCT,” 2020.

Gwen Musial

Cologne Experimental Eye Imaging Center (CEE-IC)
Ocular Surface Group
University of Cologne, Department of Ophthalmology

E-mail: gwen.musial[at]