Ocular surface disease limits surgical options
Prepare your patient by assessing and treating the ocular surface
As laser vision correction outcomes continue to improve, the occasional limiting factor for the patient’s success is the ocular surface.
Ocular surface disease (OSD) is a commonly diagnosed ocular condition in the general population. It is estimated that over 30 million people in the United States suffer to some extent from dry eye.1
As the U.S. population continues to age, the number of patients with dry eye also increases.
In 2016, OSD became the most common complication of laser vision correction.2 The incidence peaks at one week and up to 48 percent of patients still have some dry eye symptoms at three months.2
Also, dry eye symptoms and irritation associated with contact lens wear is one of the most common reasons why patients elect laser vision correction.3
This means diagnosing and treating dry eye in the management of refractive surgery patients and identifying those patients at risk prior to surgery is important. From history there are many factors that identify at risk patients.
Related: Extended depth-of-focus IOLs may provide improved visual performance
OSD treatment, diagnostics continue to evolve
Female patients have an increased risk of dry eye in the general population and an increased risk of dry eye after laser-assisted in situ keratomileusis (LASIK) surgery.
Research found females to be 32 percent more likely to have dry eye symptoms after surgery. Hyperopes are also more likely to have dry eye symptoms.
While hyperopic treatments remove a larger amount of tissue-albeit in the periphery of the cornea-it is believed that more corneal nerves are damaged, leading to the increase in dry eye.
It was also reported that there is not an increase in dry eye as corneas get steeper in hyperopic treatment.4
There is an increased risk of dry eye in treatments for patients over -6.00 D. Asians and patients who are on medicines that may dry the eyes are at an increased risk of post-operative dry eye as well.5
Diagnosing patients with ocular surface disease continues to evolve as we learn more about the tear film and its effect on the cornea.
Osmolarity, inflammatory mediators, lipid layer, and tear lake volume are in the constellation of tests we now conduct for a patient’s ocular surface.
We now are able to better analyze the meibomian glands, blink rate, and the scatter created by an abnormal tear layer. Patient symptoms are still relevant to preparing the ocular surface for refractive surgery.
Hyperosmolarity is both sensitive and specific for dry eye syndrome. This is valuable for a disease in which patient signs and symptoms are often in conflict.
Related: The role of lid hygiene in ocular surface disease
We are just beginning to understand the value of tear osmolarity in surgical eye care. In a 2015 study Matossian and colleagues found an increase in keratometric variability in patients with hyperosmolarity.6
This variability created significant variability in intraocular lens (IOL) calculations and thus patients’ refractive outcomes.
In a study published in IVOS 2010 Donnenfeld et al found that patients with hyperosmolarity had poorer uncorrected visual acuity (UCVA) at three months after LASIK.7
InflammaDry (RPS Diagnostics) is an in-office test that detects MMP-9, an inflammatory marker that is consistently elevated in the tears of patients with dry eye disease. MMP-9 has also been implicated in poor epithelial healing, epithelial ingrowth, and corneal ulceration after refractive surgery.
Testing MMP-9 levels prior to surgery can help guide treatment if inflammation is detected and look for other causes of symptoms of it is normal. For example, in patients with anterior basement membrane dystrophy (ABMD) and conjuctival chalasis MMP-9 levels are likely to be normal.
Meibomian gland health also plays role
Meibomian gland disease (MGD) has been found to be a leading cause of ocular surface disease.8
Meibomian gland expressability is a simple yet effective diagnostic test to determine the functionality of the glands. Evaluating the meibum expressed from the gland is clinically significant and relates to its free fatty acid (FFA) composition. The Nichols grading system identifies meibum as either clear, cloudy, yellow, or absent. Grading the meibomian glands may correlate to meibomian gland loss as well as tear break-up time (TBUT) and corneal staining.
Lipid layer thickness can be objectively measured with interferometry and may be thinner in patients with obstructive meibomian gland disease.
Related: A new tool for managing ocular surface disease
Meibomian gland disease plays a larger role in ocular surface disease than previously understood. Today there are commercially available diagnostic devices that allow the clinician to image and as importantly show the patient the damage to those glands.
It is not completely understood if or how atrophied glands can be revived. It may be that a significant loss of meibomian glands leads to dry eye symptoms. The lower glands seem to have a greater impact and along the lower lid the nasal glands may have the greatest impact.
Blink rate major factor
Why meibomian glands become damaged is not completely known, but it appears to be related to inflammation and blink rate. Blinking is the mechanism that causes the release of meibum into the tear layer.9
Today we spend a significantly more time exposed to digital devices such as phones, tablets, and computers, which all lead to a lower blink rate and poorer quality of blink.10
Observing a patient’s blink rate and pattern can identify which patients are at greater risk. It is not uncommon to observe patients and only every fourth or fifth blink is a complete blink. This leaves the cornea exposed and as important the meibum not expressed from the gland.
Meimography is an imaging technology that allows the clinician to evaluate a digital image of the meibomian glands. The clinician is able to identify distorted, truncated, or atrophied glands.
Related: Amniotic membrane in ocular surface disease
While a patient can be sign and symptom free with a minimal number of functioning glands, there appears to be a correlation between functioning glands and ocular surface disease-with functioning glands on the lower lid more important than upper lid glands.11
A patient with fewer glands may require more aggressive treatment.
Patient qualification is key
Using an objective and consistent method of qualifying and quantifying patients’ symptoms prior to surgery is valuable. Several validated dry eye questionnaires provide useful information.
The Ocular Surface Disease Index (OSDI) is a 12-question survey to evaluate the symptoms of dry eye disease and how they affect the quality of vision. The Standard Patient Evaluate of Eye Dryness (SPEED) survey is eight questions aimed at identifying the frequency and severity of dry eye symptoms.12
A number from one of these questionnaires can aid the doctor in categorizing the patient. It can also help identify if and where there is a disconnect between signs and symptoms of the disease.
While staining, tear break-up time and Zone Quick are still used in the diagnosis of ocular surface disease, we now have an array of new tests that help refine both the diagnosis and treatment.
It is far easier to explain to a patient prior to surgery why he is at greater risk of dry eye symptoms then trying to solve that riddle after.
Related: Clinical challenges in anterior segment ocular disease
References
1. Market Scope. Report on the Global Dry Eye Market. St. Louis, Mo: Market Scope, July 2004.
2. De Paiva CS, Chen Z, Koch DD, Hamill MB, Manuel FK, Hassan SS, Wilhelmus KR, Pflugfelder SC The incidence and risk factors of dry eye after lasik. Am J Ophthalmol. 2006 Mar;141(3):438-45.
3. Hovanesian JA, Shah SS, Maloney RK. Symptoms of dry eye and recurrent erosion syndrome after refractive surgery. J Cataract Refract Surg.2001 Apr;27(4):577-84.
4. Toda I, Asano-Kato N, Hori-Komai Y, Tsubota K. Laser-assisted in situ keratomileusis for patients with dry eye. Arch Ophthalmol. 2002;120:1024-28.
5. Albietz JM, Lenton LM, McLennan SG. Effect of laser in situ keratomileusis for hyperopia on tear film and ocular surface. J Refract Surg. 2002 Mar-Apr;18(2):113-23.
6. Epitropoulos AT, Matossian C, Berdy GJ, Malhotra RP, Potvin R. Effect of tear osmolarity on repeatability of keratometry for cataract surgery planning. J Cataract Refract Surg. 2015 Aug;41(8):1672-7.
7. Eldridge DC, Donnenfeld E, Burr T, et al. Presurgical hyperosmolarity and treatment with AMO Blink Tears predicts refractive outcomes. 2012 Association for Research in Vision and Ophthalmology Annual Meeting, Fort Lauderdale, FL.
8. Schaumberg DA, Sullivan DA, Buring JE, Dana MR. Prevalence of dry eye syndrome among US women. Am J Ophthalmol. 2003 Aug;136(2):318-26.
9. Linton RG, Curnow DH, Riley WJ. The meibomian glands: An investigation into the secretion and some aspects of the physiology. Br. J. Ophthalmol. 1961 Nov;45(11):718-723.
10. Wolkoff P, Nojgaard JK, Troiano P, Piccoli B. Eye complaints in the office environment: precorneal tear film integrity influenced by eye blinking efficiency. Occup Environ Med. 2005 Jan; 62(1):4-12.
11. Eom Y, Choi KE, Kang SY, Lee HK, Kim HM, Song JS. Comparison of meibomian gland loss and expressed meibum grade between the upper and lower eyelids in patients with obstructive meibomian gland dysfunction. Cornea. 2014 May;33(5):448-52.
12. Blackie C, Albou-Ganem C, Korb D. Questionnaire assists in dry eye disease diagnosis: Four-question survey helps evaluate patients’ dry eye symptoms to improve screening. Ocular Surg News. 2012 Nov. Available at: Questionnaire assists in dry eye disease diagnosis: Four-question survey helps evaluate patients’ dry eye symptoms to improve screening. Accessed 1/24/17.
