Diagnosing dry eye disease (DED) is a common challenge in clinical practice. The prevalence of dry eye has been estimated in a meta-analysis to be between 5 and 50%, with significant variation in data due to age, sex, location, and diagnostic criteria.1
The differential diagnoses for dry eye disease are extensive, and effectively using clinical examination techniques to rule out dry eye mimicking diseases is crucial to accurate diagnosis.
The third Tear Film and Ocular Surface Society Dry Eye Workshop (TFOS DEWS III) has updated the definition of dry eye to require both patient symptoms and clinical signs.2 Using patient symptoms alone to diagnose DED may fail to identify conditions that have similar symptoms but different etiologies.
Ocular surface imaging can assist with identifying clinical signs and help limit subjective interpretation issues. It is also helpful with patient education, and invaluable in the decision-making process regarding treatment recommendations.
Imaging techniques that assist in DED diagnosis
TFOS DEWS III states that dry eye can be diagnosed when there is a positive patient symptom questionnaire result (such as a score of ≥4 on the Ocular Surface Disease Index [OSDI-6]) along with one or more of the following indicating loss of tear film homeostasis:2
- A non-invasive tear breakup time (TBUT) of <10 seconds or a fluorescein TBUT of <5 seconds
- Hyperosmolarity of ≥308mOms/L in either eye or a difference of >8mOms/L between the eyes
- >5 punctate spots of corneal fluorescein staining
- >9 punctate spots of conjunctival lissamine green staining
- ≥2mm in length and ≥25% of the width of the lid margin lissamine green staining
Figure 1: Lid margin staining in a 54-year-old female.
Figure 1: Courtesy of Roxanna Potter, OD, FAAO, FSLS.
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Ocular Surface Imaging for DED
Use this cheat sheet to compare corneal imaging modalities that can enhance and guide dry eye disease diagnosis and management.
Tear breakup time
Ocular surface imaging can increase the ease and accuracy of finding these signs. Tear breakup time is a clinical test often performed to assess tear stability. The instillation of fluorescein allows for the visualization of the tear film under slit lamp examination but is considered invasive as it can cause measurement inaccuracy by itself increasing tear film volume and instability.2,3
Assessing non-invasive tear breakup time (NITBUT) is preferred and can be performed using various instruments. Tear film interferometry can detect changes in the tear interference patterns between blinks.4
Instruments like topographers that project Placido-disc patterns onto the cornea can measure NITBUT by timing how long it takes for distortion of the mires to occur.5 Unfortunately, the variability of the tear film itself can decrease the repeatability of both tear breakup measuring modalities.6
Figure 2: NITBUT of a 47-year-old female.
Figure 2: Courtesy of Roxanna Potter, OD, FAAO, FSLS.
Ocular surface staining
Ocular surface staining is another important criterion used in dry eye diagnosis. This can be done during a normal slit lamp examination, but anterior segment photography can better capture staining extent and pattern, be repeated to monitor for therapeutic improvement, and provide patient education.
Future studies in ocular surface staining may reveal more specific connections between patterns of staining and dry eye disease drivers.7
Figure 3: Corneal staining on a 73-year-old male.
Figure 3: Courtesy of Roxanna Potter, OD, FAAO, FSLS.
Imaging techniques that assist in treatment decision-making
Ocular surface imaging can help with more than diagnosis. Using imaging to aid in the classification of a patient’s dry eye can help determine the therapeutic approach.
TFOS DEWS III also subclassifies the etiological drivers of dry eye disease into four broad categories, the first three of which ocular imaging can help determine:2
- Tear film deficiencies
- Eyelid anomalies
- Ocular surface abnormalities
- Systemic conditions
Tear film deficiencies
The tear meniscus and its associated properties, such as height (TMH), width, area, and curvature, can be used not only in measuring decreased tear film volume but also in specifically identifying aqueous deficiency.8,9 Meniscometry is generally done in the center of the lower lid while the patient is in primary gaze, with a value < 0.20mm being indicative of dry eye disease.2
The tear meniscus can be observed at the slit lamp during normal examination, analyzed with anterior segment photography or keratography, or with the use of anterior optical coherence tomography (OCT).10
However, in the presence of lid margin, conjunctival, or other structural ocular surface abnormalities, the reliability of meniscus measurement may be reduced.
Figure 4: Tear meniscus height of a 28-year-old female.
Figure 4: Courtesy of Roxanna Potter, OD, FAAO, FSLS.
Lipid deficiencies can be detected using tear film interferometry. Tear film interferometers measure the thickness, stability, and quality/overall pattern of the lipid layer of the tear film via multicolor interference patterns.4 Careful examination of meibomian gland structure with meibography can also indicate a lipid-based driver of dry eye disease.
Figure 5: Interferometry of a 54-year-old female.
Figure 5: Courtesy of Roxanna Potter, OD, FAAO, FSLS.
Evidence of mucin deficiency may be captured using anterior segment photography of lissamine green staining of the conjunctiva, or with in vivo confocal microscopy of conjunctival goblet cells, though this is less common in clinical practice.2
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Eyelid abnormalities
Anterior segment photography and videography can also be useful in studying lid and blinking abnormalities such as partial blinking, lagophthalmos, blepharitis, lid margin malposition and keratinization, lid wiper epitheliopathy, and ocular rosacea.2
Figure 6: Anterior segment camera photo of ocular rosacea in a 68-year-old male.
Figure 6: Courtesy of Roxanna Potter, OD, FAAO, FSLS.
Meibography can be performed using infrared, confocal microscopy, or anterior OCT. Pairing the collected imaging information on meibomian gland number, size, and morphology with manual expression findings can inform treatment decisions that address meibomian gland dysfunction and the replenishment of lipids in the tear film.8,11
Figure 7: Meibography showing extensive gland dropout in a 49-year-old female.
Figure 7: Courtesy of Roxanna Potter, OD, FAAO, FSLS.
Ocular surface abnormalities
Ocular surface staining indicates cellular damage and, as aforementioned, can be imaged with anterior segment photography. Corneal topography may help identify dry-eye mimicking differentials such as pterygium, keratoconus, and corneal dystrophy.
Anterior segment OCT can also be used to investigate some more novel ocular surface abnormalities. Changes and patterns in corneal epithelial thickness have been found with OCT mapping to correlate with other signs and symptoms in dry eye patients and may help determine severity of disease.12,13
Lid-parallel conjunctival folds (LIPCOF) can be imaged grossly by anterior segment photography, but also with much higher resolution using anterior OCT. This finding has a strong correlation with dry eye disease presence and severity and is an important future area of dry eye disease research.2,14
Figures 8 and 9: LIPCOF as seen on both OCT (Fig 8) and anterior segment camera (Fig 9) of a 54-year-old female.
Figure 8: Courtesy of Roxanna Potter, OD, FAAO, FSLS.
Figure 9: Courtesy of Roxanna Potter, OD, FAAO, FSLS.
Additional imaging techniques that may elucidate neural or inflammatory etiological drivers of dry eye disease include photographic analysis of conjunctival hyperemia and confocal microscopy of the cornea and lacrimal gland.2
Most primary care optometrists do not have access to confocal microscopy, and more research is needed to better define grading scales for both of these modalities, so the practical use of either is currently limited.
Integration and follow-up
A primary advantage of ocular surface imaging is that it can often be performed by a trained technician prior to the doctor’s assessment. This can be integrated into the patient workup automatically after a positive result on the patient symptom questionnaire, or as part of a more in-depth dry eye follow-up appointment.
More complex imaging may be ordered or performed by the doctor after other clinical findings are identified for patient education or to establish baseline images for future reference.
Providing the patient with visual evidence of their disease drivers can help with treatment compliance and provide doctors with more accurate diagnoses and more targeted treatment recommendations. It is far easier to observe improvement in clinical signs when imaging is done regularly, reinforcing both the doctor's and patient’s desire to continue with successful treatments.
Conclusion
With a wide range of symptoms and signs, and an extensive list of etiological subtypes and treatment options, dry eye disease can be overwhelming to both patient and practitioner. Utilizing ocular surface imaging techniques can simplify the approach to both diagnosis and treatment.
