Article

CLINICAL: Cornea

Diagnose Corneal Disease

Streamline detection and care with these diagnostic tools

A 10-year-old boy presented with conjunctivitis the day before his first day of school. A decade ago, I would have told him to stay home: Viral and bacterial conjunctivitis can have similar clinical presentations. At this visit, however, I utilized a point-of-care diagnostic test to help me definitively identify his conjunctivitis.

Specifically, via a sterile sample collector stick, test cassette and buffer vial, the test confirms whether a patient’s conjunctivitis is viral, with 90% sensitivity and 96% specificity rates. Performing the test takes a few minutes, and results are available in roughly 10 minutes.

Here, I discuss additional advanced diagnostic tools for the cornea, in order of condition, and the outcome of the aforementioned test.*

ALLERGY

  • Point-of-care scratch test. This test, comprised of a plastic applicator that contains small amounts of 60 allergens specific to each region of the United States, takes three minutes to perform and between 10 to 15 minutes for results.**

DRY EYE DISEASE

  • Interferometry. This tool measures the sub-micron thickness of the lipid layer to help determine whether it is insufficient, due to meibomian gland dysfunction (MGD).
  • Meibography. This captures images of the meibomian gland structures to aid O.D.s in identifying gland loss, gland atrophy and MGD at all stages.
  • Point-of-care inflammatory marker test. This test, via a sterile sample collector stick, test cassette and buffer vial, detects matrix metalloproteinase-9 (MMP-9), which are non-specific proteolytic enzymes linked with dry eye disease (DED). The test, which has 85% specificity and 94% sensitivity, takes a few minutes to perform and reveals results in 10 minutes. A positive test occurs when >40 ng/ml of MMP-9 is detected in the tears.
  • Point-of-care Sjögren’s test. This test assesses the blood for four historic biomarkers and three proprietary biomarkers of Sjögren’s syndrome to aid in early diagnosis.**
  • Tear osmolarity testing. This tool provides a range of DED severity, based on high or low osmolarity levels. Specifically, it examines the concentration of electrolytes in the tear film with high osmolarity numbers >308, and differences between the eyes >8, indicating DED.

INFECTIOUS AILMENTS

  • Culture plates. Culturing is vital for conditions, such as herpes simplex virus (HSV) and infectious keratitis and corneal ulcers because they give optometrists a proper diagnosis to help form the appropriate treatment plan. The most common culture types:
    1. Sabouraud: Fungal
    2. Chocolate: Haemophilus, Moraxella, Neisseria
    3. Blood: Bacteria, fungal, Haemophilus, Moraxella
    4. Thioglycollate broth: bacteria, fungi
  • Microscope slides. Slides for microscopy stains are ideal for a variety of organisms, such as bacteria, fungi, microsporidia, acanthamoeba and mycobacterium, as they enable optimum viewing.

VARIOUS CONDITIONS

  • Vital dyes. Stains, such as lissamine green, NaFl and Rose Bengal, aid in the detection of conditions, such as anterior basement membrane dystrophy, corneal abrasions, corneal ulcers, DED, HSV keratitis, punctate epithelial keratoconjunctivitis, analyzing TBUT and Thygeson’s superficial punctate keratitis. Lissamine green dye stains devitalized and membrane-damaged cells, making it ideal for viewing conjunctival staining. Rose Bengal dye stains damaged, dead and living corneal and conjunctival cells seen in DED. NaFL is viewed with cobalt blue light to identify punctate keratitis and to perform TBUT testing.
  • Specular microscopes. These allow for the evaluation of endothelial cell counts and morphology. As a result, they are useful in diagnosing and monitoring corneal edema, corneal guttata, Descemet membrane endothelial keratoplasty, Descemet stripping endothelial keratoplasty, Fuchs’ corneal dystrophy and keratoconus, among other conditions.

    DED with diffuse punctate epithelial and filamentary keratitis is shown.
    Image courtesy of Dr. Josh Johnston

  • Topography. Topographers aid in identifying corneal diseases, such as keratoconus, and a myriad of other inherited corneal dystrophies, such as pellucid marginal degeneration, corneal ectasia, Salzmann’s nodular degeneration and corneal scars, to name a few. Some topographers can now aid in scleral contact lens and soft contact lens fits and perform meibography and non-invasive TBUT.

THAT 10-YEAR-OLD BOY

The point-of-care test confirmed non-infectious conjunctivitis. The boy was ecstatic when I told him he could go to his first day of school. While this case was not critical, having this tool at my fingertips to streamline the diagnosis was invaluable. The diagnostic tools outlined above can be implemented today to aid in detecting corneal conditions and, thus, elevate our practices in the eyes of patients. OM

* Optometrists should inquire with their state boards about using, as these tests can fall outside scope-of-practice laws.

** Billing and coding for such procedures is determined by each individual insurance plan.