Biomarkers of Ocular Surface Disease Using Impression Cytology

Abstract

Impression cytology (IC) is a technique which permits the retrieval of the outermost layer of ocular surface cells via the use of various types of filters. It is a minimally invasive method of evaluating human conjunctival epithelial cell morphology in the diagnosis of dry eye disease, a common and distressing disorder associated with ageing, contact lens wear, autoimmune disorders and refractive (LASIK) surgery. IC may also be utilized in the diagnosis of other ocular diseases, such as keratoconus and thyroid orbitopathy. More recently, IC has been utilized for the subsequent investigation of gene and protein expression of conjunctival cells in order to identify novel diagnostic biomarkers and to further our understanding of the mechanisms underlying ocular surface disease. This review will therefore examine the literature concerning the role of IC in identifying cellular markers of eye disease, systemic diseases with ocular involvement and potential novel therapeutic targets. Impression cytology (IC) is a minimally invasive method of evaluating human ocular surface cells and is considered as the 'gold standard' technique for assessing cell morphology. Introduced by Thatcher et al. [1] and Egbert et al. [2], IC is an easy-to-use technique of directly retrieving (mainly conjunctival) cells, using various filter types which are gently applied to exposed (interpalpebral) conjunctival surfaces. The filters used include cellulose acetate [3], polycarbonate (Biopore, Millipore UK Ltd, Watford, UK) [4], nitrocellulose [5] or polyethersulfone (PES) [6] which are gently applied to exposed (interpalpebral) conjunctival surfaces. Recently, a more standardized tool for IC sampling has been introduced (Figures 1 & 2). The Eyeprim is a new single-use PES filter sampling medical device for retrieval of conjunctival cells (Opia Technologies, France) and a recent study by Lopez-Miguel et al. [7] performed an analysis of this tool versus the traditional IC method (PES). On a cohort of 20 healthy individuals, they extracted and compared RNA from both devices and found no significant differences in the mean yield (p ≥ 0.45), the total RNA amount (μg), or the amount normalized to membrane area [7]. Although an earlier study of the Eyeprim [8], suggested that it recovered more cells than traditional IC, Lopez-Miguel et al. [7] did not observe differences in the RNA collected between this device and PES.Historically, IC has been used to analyze pathological changes to conjunctival cells for indicators of squamous metaplasia in ocular surface disease (OSD) [9]. More recently, however, researchers have used IC to examine specific markers of inflammation, for example, HLA-DR, ICAM-1 and CD8 [10][11][12], and to examine novel biomarkers of dry eye disease (DED). The latter is performed in an attempt to understand the mechanisms underpinning DED pathophysiology and is now feasible, due to vast improvements in the assay sensitivities for gene and protein examination [13]. As a result, IC membranes can be subsequently analyzed using techniq...

Review of Biomarkers in Ocular Matrices: Challenges and Opportunities

“…It is easily repeatable, minimally invasive, and rapid collection technique for sampling superficial conjunctival epithelial cells in an almost painless manner ( 101 , 102 ). This technique uses absorbent filters which are applied to conjunctival surfaces and are made of cellulose acetate, polycarbonate, nitrocellulose or polyethersulfone (PES) ( 103 ). Recently, a single-use PES filter sampling device known as the Eyeprim device (Opia Technologies, France) has been introduced for IC sampling to better standardize the procedure.…”

Novel Approaches for Imaging-Based Diagnosis of Ocular Surface Disease

“…Impression cytology can be applied in various diseases of the ocular surface because it provides information about conjunctival histology. The technique, however, requires that a filter is pressed against the conjunctiva and therefore cannot be considered to be non-invasive [ 10 ].…”

Ocular Surface Changes in Prostaglandin Analogue-Treated Patients

“…Dry eye disease, one of the most common eye diseases [56], was redefined by the Asia Dry Eye Society as follows: “dry eye is a multifactorial disease characterized by unstable tear film causing a variety of symptoms and/of visual impairment, potentially accompanied by ocular surface damage.” As discordance between symptoms and signs of dry eye has been recognized [57], studies focused on the neurological or psychiatric factors in the development of dry eye have raised our concern [58, 59]. In addition, some researchers have proposed the concept of ocular surface microenvironment in both diagnosis and treatment of dry eye [60, 61].…”