Published in Ocular Surface

A Spectrum of Dysfunction: Differentiating the Types of Dry Eye

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7 min read

Learn the techniques available to optometrists for identifying the various types of dry eye.

A Spectrum of Dysfunction: Differentiating the Types of Dry Eye
While dry eye has traditionally been divided into the categories of aqueous deficient and evaporative, in many ways, this is an oversimplification. Thanks to advancements in our understanding of dry eye disease (DED), we are well aware it is a multifactorial condition.1
So, in reality, most cases of dry eye do not neatly fit into the buckets of aqueous deficient or evaporative but rather exist on a spectrum that comprises many different ocular surface disorders. These other conditions, such as blepharitis and ocular rosacea, also contribute to dry eye by feeding into and often exacerbating one another.
However, there is significant clinical relevance to delineating the contributing factors to an individual patient’s dry eye. This value lies not solely in assigning a label to the type of dry eye but rather in teasing apart the specific elements of the patient’s condition.

Contributing conditions in dry eye

In the majority of cases, a patient will have several conditions contributing to their dry eye at once, and each one must be addressed to treat the disease completely. However, because dry eye exists on a spectrum and the signs and symptoms of the contributory conditions are often nonspecific and inevitably overlap, it can be somewhat challenging to determine which factors are in play.

For this reason, I attempt to simplify this process by assigning each of the most common contributing factors to DED a single unique sign or symptom that sets it aside from the myriad of other ocular surface diseases which allows for easy identification, diagnosis, and subsequent treatment.

The most common, and perhaps the most easily identifiable, contributing condition to DED is meibomian gland dysfunction (MGD).2
Figure 1 is a clinical image of inflamed, distended, and inspissed meibomian glands caused by MGD.
Inflamed, Distended, and Inspissed Meibomian Glands
Figure 1: Courtesy of Cory Lappin, OD, MS, FAAO
These dysfunctional glands have turbid or toothpaste-like secretions upon expression rather than the typical olive-oil consistency observed in healthy glands. These findings are indicative of evaporative dry eye, as the abnormal meibum secreted (or lack of secretion) results in a poor lipid layer that causes instability and premature evaporation of the tear film.3

Evaluation through meibography

If available, meibography is the single best way to evaluate the health of the meibomian glands, as this will display signs of meibomian gland dysfunction.
Figure 2 highlights meibography OU showing meibomian gland obstruction, inflammation, and drop out.
Meibography OU
Figure 2: Courtesy of Cory Lappin, OD, MS, FAAO
If a meibographer is unavailable, transillumination of the eyelids can also reveal the general state of the meibomian glands, including gland morphology.
Additionally, lipid layer interferometry, such as that obtained by the LipiView II, is an excellent way to assess meibomian gland function, as this can act as a proxy for meibum production.
Figure 3 features the results of lipid layer interferometry from the LipiView II on a patient with MGD.
MGD lipid layer interferometry from the LipiView II
Figure 3: Courtesy of Cory Lappin, OD, MS, FAAO
Cases of aqueous deficient dry eye, while much less common than MGD, can be identified by a low tear volume characterized by a reduced tear meniscus height (usually lower than 0.20mm), as illustrated in Figure 4.4,5
Figure 4 highlights a meibomian gland dysfunction patient with decreased tear meniscus height.
Decreased Tear Meniscus Height
Figure 4: Courtesy of Cory Lappin, OD, MS, FAAO
Although tear production is traditionally evaluated using Schirmer strips, I have found this provides relatively little practical value as this is not a “real-world” test. By inserting the strip, you are introducing a foreign body onto the ocular surface that elicits reflex tearing which is fundamentally different than basal tear production, which is the primary concern in dry eye. Also, performing the test with anesthetic blocks corneal nerve function, which is instrumental to normal blinking and lacrimation.

Aqueous deficient dry eye is typically associated with Sjogren’s Syndrome, so patients will also often report dry mouth and dry skin in addition to dry eye. Therefore, an effective way to assess aqueous deficiency is by evaluating tear meniscus height and taking a detailed patient history.

Analysis of tear breakup time and corneal staining

It is important to mention tear breakup time (TBUT) in the context of differentiating the causes of dry eye. While TBUT can be crucial to diagnosing dry eye in general, it is relatively nonspecific as it can be reduced in both aqueous deficient and evaporative dry eye, even though it is classically associated with MGD.6 Therefore, its ability to differentiate the subtypes of dry eye is somewhat limited.
Vital dyes, such as sodium fluorescein and lissamine green, are also essential to evaluate the health of the ocular surface. Sodium fluorescein is ideal for assessing the integrity of the cornea, as it stains damaged and degenerated corneal cells as well as epithelial defects, whereas lissamine green is well-suited for evaluation of the conjunctiva (due to its enhanced contrast) where it stains dead and devitalized cells.7 Staining, in either case, can signify the presence of dry eye and ocular surface inflammation.7,8
However, similar to TBUT, staining is relatively nonspecific in regard to the subtypes of dry eye. While the presence of SPK, which is highlighted by staining, is typically associated with aqueous deficient dry eye (due in part to its association with Sjögren’s Syndrome and the inflammatory nature of the condition), SPK and staining can also be present in MGD.9

So, while valuable in assessing the state of the ocular surface, the use of vital dyes and the presence of staining do not readily separate the different types of dry eye.

Contributing factors to dry eye with unique distinguishing features:

  • The presence of lash collarettes in Demodex blepharitis10,11
  • Tear saponification in bacterial blepharitis12
  • The presence of telangiectatic vessels on the lid margin or conjunctiva that flare with environmental triggers in ocular rosacea13,14
  • Reduced or absent corneal sensation determined by sensitivity testing with a cotton wisp in neurotrophic keratitis15,16
  • Incomplete lid closure is characterized by a gap between the upper and lower lid that can be revealed using a transilluminator with the patient’s eyes closed and their head in a reclined position17,18

Final thoughts

Therefore, the true importance of distinguishing the “types” of dry eye does not necessarily lie in the ability to put a label on the diagnosis but rather in identifying the individual elements of a patient’s dry eye so each factor can be properly addressed and the condition completely treated.
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  2. Lemp MA, Crews LA, Bron AJ, et al. Distribution of aqueous-deficient and evaporative dry eye in a clinic-based patient cohort: a retrospective study. Cornea. 2012;31(5):472-478. doi:10.1097/ICO.0b013e318225415a
  3. Tomlinson A, Bron AJ, Korb DR, et al. The international workshop on meibomian gland dysfunction: report of the diagnosis subcommittee. Invest Ophthalmol Vis Sci. 2011;52(4):2006-2049. Published 2011 Mar 30. doi:10.1167/iovs.10-6997f
  4. Chen Q, Zhang X, Cui L, et al. Upper and lower tear menisci in Sjögren's syndrome dry eye. Invest Ophthalmol Vis Sci. 2011;52(13):9373-9378. Published December 9, 2011. doi:10.1167/iovs.11-7431
  5. Zeev MS, Miller DD, Latkany R. Diagnosis of dry eye disease and emerging technologies. Clin Ophthalmol. 2014;8:581-590. Published March 20, 2014. doi:10.2147/OPTH.S45444
  6. McMonnies CW. Aqueous deficiency is a contributor to evaporation-related dry eye disease. Eye Vis (Lond). 2020;7:6. doi:10.1186/s40662-019-0172-z
  7. Rojas R. Vital dyes for Dry eyes. Review of Optometry. Published July 15, 2022. Accessed March 2, 2023.
  8. McKenzie M, Whitley W. A Closer Look at Corneal Inflammation. Review of Cornea and Contact Lenses. Published November 15, 2012. Accessed March 2, 2023.
  9. Suzuki T. Inflamed Obstructive Meibomian Gland Dysfunction Causes Ocular Surface Inflammation. Invest Ophthalmol Vis Sci. 2018;59(14):DES94-DES101. doi:10.1167/iovs.17-23345
  10. Gao YY, Di Pascuale MA, Li W, et al. High prevalence of Demodex in eyelashes with cylindrical dandruff. Invest Ophthalmol Vis Sci. 2005;46(9):3089-3094.
  11. Bitton E, Aumond S. Demodex and eye disease: a review. Clin Exp Optom. 2021;104(3):285-294. doi:10.1111/cxo.13123
  12. Putnam CM. Diagnosis and management of blepharitis: an optometrist's perspective. Clin Optom (Auckl). 2016;8:71-78. Published 2016 Aug 8. doi:10.2147/OPTO.S84795
  13. Wilkin J, Dahl M, Detmar M, et al. Standard classification of rosacea: Report of the National Rosacea Society Expert Committee on the Classification and Staging of Rosacea. J Am Acad Dermatol. 2002;46(4):584-587. doi:10.1067/mjd.2002.120625
  14. Vieira ACC, Höfling-Lima AL, Mannis MJ. Ocular rosacea--a review. Arq Bras Oftalmol. 2012;75(5):363-369.
  15. Bonini S, Rama P, Olzi D, Lambiase A. Neurotrophic keratitis. Eye (Lond). 2003;17(8):989-995.
  16. Chang BH, Groos EB Jr: Neurotrophic keratitis; in Krachmer JH, Mannis MJ, Holland EJ eds. Cornea. London, Elsevier, 2011.
  17. Tsai SH, Yeh SI, Chen LJ, et al. Nocturnal lagophthalmos. Int J Gerontol. 2009;3(2):89-95.
  18. Kabat A, Sowka J. 'Like Sandpaper in the Morning'. Review of Optometry. Published April 16, 2012. Accessed February 25, 2023.
Cory J. Lappin, OD, MS, FAAO
About Cory J. Lappin, OD, MS, FAAO

Dr. Cory J. Lappin is a native of New Philadelphia, Ohio and received his Bachelor of Science degree from Miami University, graduating Phi Beta Kappa with Honors with Distinction. He earned his Doctor of Optometry degree from The Ohio State University College of Optometry, where he concurrently completed his Master of Science degree in Vision Science. At the college he served as Class President and was a member of Beta Sigma Kappa Honor Society. Following graduation, Dr. Lappin continued his training by completing a residency in Ocular Disease at the renowned Cincinnati Eye Institute in Cincinnati, Ohio.

Dr. Lappin has been recognized for his clinical achievements, receiving the American Academy of Optometry Foundation Practice Excellence award. He has also been actively engaged in research, being selected to take part in the NIH/NEI T35 research training program and receiving the Vincent J. Ellerbrock Memorial Award in recognition of accomplishments in vision science research.

Dr. Lappin practices at Phoenix Eye Care and the Dry Eye Center of Arizona in Phoenix, Arizona, where he treats a wide variety of ocular diseases, with a particular interest in dry eye and ocular surface disease. He is a Fellow of the American Academy of Optometry, a member of the American Optometric Association, and serves on the Board of Directors for the Arizona Optometric Association. He is also a member of the Tear Film and Ocular Surface Society (TFOS) and volunteers with the Special Olympics Opening Eyes program.

Cory J. Lappin, OD, MS, FAAO
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