Association of Optometric Contact Lens Educators

Contact Lens Associated Dry Eye

SYMPTOMS and OCULAR SIGNS:
Symptoms1-7 of CL-associated dry eye include foreign body sensation, tearing or burning, ocular discomfort, red irritated eyes and a sensation of ocular surface dryness. Symptoms often worsen with the progression of the day and are exacerbated by drafts, air conditioning or heating vents, wind, tobacco smoke, chemical vapors, dust,  lint and other pollutants.

The ocular sign 1-2  most commonly associated with CL-induced dry eye is corneal staining. Varying degrees and extent of staining will indicate the severity of CL-induced dryness. Using a standardized grading scale, such as the CCLRU 8 grading scale (Figure 1), the progression and regression of the corneal staining can be monitored with more precision. With rigid gas permeable (RGP) lenses, the corneal staining is most often found at 3 and 9 o'clock, close to the limbus. With soft hydrogel lenses, the staining is most commonly found on the lower third of the corneal surface.

Other common signs 1-2 are lens surface dehydration, surface deposits, bulbar hyperemia and an increased conjunctival papillary response. 
 

INCIDENCE:  It is challenging to find a consensus on the incidence and/or prevalence of contact lens induced dry eyes. This is due in part to the varying definitions of dry eye that exist in the literature coupled with the myriad of symptoms the patient describes and the numerous diagnostic tests available. In an effort to better compare future dry eye studies, a special National Eye Institute (NEI)/Industry Workshop on Clinical Trials of Dry Eye held in 1995 6   established a working definition of dry eye as;

Dry eye is a disorder of the tear film due to tear deficiency or excessive tear evaporation which causes damage to the interpalpebral ocular surface and is associated with symptoms of ocular discomfort.

This should standardize somewhat the definition of dry eyes and faciliate comparison and interpretation of international studies. Contact lens associated dry eye falls within the evaporative dry eye section of the above definition.

Depending on the methodology, age group and gender of those studied, dryness symptoms have been reported anywhere between 10-28% 4.  Surveys by Robboy and Orsborn9  indicate that dryness is the most common complaint and reason for discontinuation, up to 40%.  Doughty et al. 10 reported 28.7% of all CL wearers in Canada report dryness.  Other studies confirm that dryness increased by the end of the day 11-15 and that symptoms correlate well with ocular signs. Symptoms are more prevalent in females and in the elderly population. 5
 

ETIOLOGY:
The etiology of CL associated dry eye can be either one of two things; the alteration of the PCTF and/or the CL itself, that is its water content, lens material and lens thickness.

PCTF

A marginally unstable or insufficient PCTF may become exacerbated in the presence of a CL. Identifying patients with this type of PCTF and other precursors can limit CL-associated dry eye and decrease chair time of unnecessary subsequent visits.

The McMonnies Dry Eye Questionnaire 16-17 has been designed to identify factors such as medication use, systemic and ocular surface disease, pre-existing symptoms of dryness and other factors which can lead to identifying marginally dry and potentially unstable PCTF. A comprehensive history is vital in identifying potential factors including environmental factors at home and at the workplace that places the CL candidate at risk for dryness.

A comprehensive anterior segment examination, with particular attention to the PCTF and lid margins, can often unmask numerous problems when dry eye is suspected. An evaluation of the PCTF’s production, distribution, outflow and stability as well as ocular surface structure integrity needs to be meticulously performed.

Production. The lacrimal gland produces the majority of the aqueous layer of the PCTF, while the meibomian glands produce the outermost lipid layer. The Schirmer tear test 18 or the Phenol Red Cotton Thread Test (CTT) 19 will identify if production of the PCTF is sufficient. Table 1 identifies values that are indicative of an unstable or inadequate PCTF.

Digital expression of the meibomian glands should provide clear sebaceous fluid-like secretions indicative of a healthy lipid layer 20-21. The tear meniscus adjacent to the meibomian gland orifices can be observed to be slightly colored by the oily secretions. A colored PCTF throughout the ocular surface, without forced gland expression, is indicative of overactive sebaceous glands and will contribute to a sticky PCTF, attracting various debris.

Observation of the tear meniscus height 22-23 is an approximation of tear production. Usually the inferior meniscus is larger than the superior and approximately the same in both eyes (given that there are little anatomical differences between the two eyes). An inferior tear meniscus height less than 0.3 mm is suspect and is indicative of aqueous deficiency. 

Distribution. Uniform distribution of the PCTF 1-2 is directly related to the action of the lids. Observation of the blink for completeness and lid-globe apposition is necessary for proper PCTF distribution. A loss of lid conformity due to scars, deformation or anomalies such as entropion or ectropion will disrupt the flow along the lid margin.

An abundance of debris along the tear meniscus will increase the viscosity and slow down the flow towards the punctum. Make-up and debris, from untreated blepharitis or other environmental debris, will contribute to a reduced flow and distribution.

Outflow. A good apposition 1-2, 24 between the globe and an open punctum is necessary for proper outflow of the PCTF. The PCTF leaves the ocular surface via the nasolacrimal route. A positive Jones test 1-2 will reveal a fluorescein stained PCTF in the ipsilateral nostril indicating an unobstructed nasolacrimal route.

Stability. In addition to evaluating PCTF production, distribution and outflow, it is equally important to evaluate PCTF stability 24. Although the tear break up time (TBUT) test is very variable, it still remains a clinically relevant and popular test of PCTF stability 24. Using a broad illumination beam and the appropriate excitation (Cobalt) and barrier (Yellow Wratten #12) filters should enhance visibility of the break. To further improve this technique, the Dry Eye Test (DET) was introduced in which the fluorescein strips are narrower and deliver a smaller amount of fluorescein to the PCTF. This methodology has improved the repeatability of the TBUT 5-6. Non-invasive tests of PCTF stability, such as tear thinning time (TTT) 25-26 and non-invasive break up time (NIBUT) 27 using the Tearscope 28 generally reveal longer tear rupture times. Table 1 indicates expected values of the PCTF stability.

Corneal and Conjunctival Integrity. Following observation of the cornea and conjunctiva, the integrity of these structures is evaluated using vital stains such as fluorescein, rose bengal or lissamine green 29-30 . Fluorescein stains defects of the corneal epithelium and are best observed using a Cobalt excitatory filter coupled with a yellow Wratten barrier filter to maximize fluorescence. Rose bengal or lissamine green, used with white light, stains devitalized corneal and conjunctival cells as well as normal conjunctival mucus. Lissamine green is reported 31 to be gentler upon instillation as compared to rose bengal which is photosensitizing. Expected results of normal ocular surface structures with vital stains range from scant to no staining. Generally signs of dry eye are revealed as inferior and/or 3-9 o'clock corneal and conjunctival staining.

Laboratory Tests. Many other tear film tests 1-2, 5   are available such as osmolarity, lactoferrin levels, and impression cytology of the conjunctival epithelium. However these require special instrumentation and technical knowledge that are not always available in, or conducive to, a  clinical setting.
 

CL Dehydration and Induced Dryness

A hypothesis put forth by some authors 32 is that as the CL loses water while wearing the lens, the oxygen transmissibility of the lens is reduced, which in turn increases the hypoxic stress on the cornea and reduces its sensitivity.  Therefore, there is reduced reflex tearing and thus you have a dryer eye.  Also contributing to this process is the increased tear osmolarity which dehyrates the lens and the cornea resulting in a dryer lens/eye. 33

Still little is known about the effect of lens dehydration and its relationship to the symptom of dryness.  Conflicting results also exist, where a relationship was found by Efron and Brennan 34 and no relationship was found with studies by Pritchard and Fonn  35 and Fonn, Situ and Simpson. 36 

Lens Material. Pusch and Walch 37  describe the differences between soft CL materials (unrelated to water content) but, varying with temperature.  CL’s containing methacrylic acid (MA) are composed of more free water molecules.  This wetting agent attracts more water and thus can release more water, readily when the lens goes from the container to the increased ocular temperature and then, throughout the day.  Whereas, lenses containing n-vinyl pyrrolidone (nPVP) are composed of more bounded water molecules.  The lens loses its ability to hydrate ions thus is limited in the amount of hydration energy which limits the amount of water loss i.e. less dehydration on eye.

It is unknown as of yet whether silicone hydrogel lenses have similar properties, related to the use of silicone and other components used to make the surface wettable.

We suspect RGP lenses, having mixtures of silicone and fluorine, that, it is the property of these materials to attract deposits (protein and lipid, respectively) that may more affect the dryness of the surface rather than the material itself.

Water Content. Many studies have tried to relate water content to lens dehydration and symptoms of dryness.  The higher the water content, the greater the water loss from 11 to 15% with increased symptoms of dryness and the lower water content lenses dehydrated the least, from 2 to 6% with less symptoms of dryness. 38-40

On the other hand other studies by Pritchard and Fonn, 35 and Fonn, Situ et al 36 have not shown this relationship between dehydration and symptoms of dryness.  They allude to other causes for symptoms of dryness other than material or water content of the contact lens. 

Again, silicone hydrogel lenses have not been yet directly related to the performance of other lenses, but, we perhaps could imply that the lower water content of these lenses would perform similarly.

Material dehydration due to water loss is not an issue with RGP lenses having no water to lose.

Center Thickness. Conflicting results have been reported regarding center thickness (CT).  Some have shown that there is a relationship between thickness and water loss 41 and others 42,43 reported no role of CT.  They found that thicker lenses had a slower dehydration rate initially but, reached the same equilibrium water content as the thinner lenses of the same water content.
 

MANAGEMENT:
PCTF
There is an intimate relationship between contact lenses and the PCTF, hence factors affecting one will have an influence on the other 3, 44-46 . Management of CL-associated dry eye will depend on the problem identified 1-4, 46. Factors identified during history such as medication use and systemic diseases need to be further considered for their potential effects on the PCTF. Medications 1-2, 46  often associated with reduced tear production include anti-histamines, tricyclic anti-depressants, beta-blockers, oral contraceptives and non-steroidal anti-inflammatory agents. An understanding of the work/leisure environment needs to also identify if a more ergonomic approach would avoid heating and air condition vents .

Any preexisting condition, such as blepharitis or Meibomian gland dysfunction (MGD) needs to be treated prior to CL wear. 

For production problems such as aqueous deficiency, tear substitutes (preferably non-preserved), inserts or punctal plugs can offer relief. An improvement of symptoms with trial dissolvable plugs can indicate if a more long term approach would be beneficial. For mucin deficiency, mast cell stabiliser can aid in the treatment of the tarsal plate as well as vitamin A drops 47 and hypotonic solutions. For severe cases  acetylcystine can be used for mucous strands. For lipid deficiency, hot compresses, lid scrubs, topical antibiotics can be useful to stimulate the sebacous glands. Systemic tetracycline may also be useful in severe cases.

For distribution problems such as incomplete blinks, the patient may be made aware of the problem and that in itself (with a post-it reminder at the work space) may induce more frequent blinking, however variable. Surgical intervention for lid scars and abnormalities should be considered if they cause a poor lid/globe apposition, especially around the punctum area.

For outflow problems, dilation and irrigation (D&I) procedures should eliminate any obstruction. Dilating a closed punctum and then irrigating the nasolacrymal route should restore a proper outflow. The Jones test #2 (following a D&I) should show fluorescein in the ipsilateral nostril. 

Stability problems, caused by blepharitis, MGD or excessive make-up debris should be treated with proper lid hygeine (daily lid scrubs, warm compresses) to improve the quality and hence the stability of the PCTF. Addressing the production problems mentioned above will also contribute to an increased stability of the PCTF, as documented by an increased rupture time.

In order to compare clinical studies, it is recommended that standardized documentation be used. Corneal staining caused by dryness can be documented using the standardized CCLRU grading scale 8 and tracked for progression and/or regression with better precision. Improvement is expected as causative factors are eliminated or controlled, hence an improvement of corneal staining should be evident.
 

Contact lenses Options

Lens Material. Change lens material, if ionic go to non-ionic, that is, increase the material wettablility by adding n-vinyl pyrrolidone (nPVP) instead of methacrylic acid (MA) or visaversa.  Try a combination lens (omafilcon A) that has properties of a Group 2 material, such as the Proclear lens, which recently received FDA approval as a material for the dry eye patient. 48-50 

Water Content. Change the water content, if high go lower or visaversa.

Center Thickness. Try a slightly thicker lens, but, do not compromise oxygen transmission.

Overall, going to a more frequent replacement schedule of any lens will reduce the incidence of deposits which contribute to the feeling of dryness.  Take into consideration the solutions the patient is using, perhaps a non-preserved system would prevent preservative-deposit binding that contributes to dryness and inflammation.

In severe cases, a reduced wearing schedule of daily replaced lenses would be ideal. If optically viable, going to an RGP with a low amount of silicone content could also be considered.

BEST REFERENCES:

1. Tomlinson A. Contact Lens-Induced Dry Eye. Chapter in Complications of Contact Lens Wear, Mosby, 1992. 
2. Snyder C. Preocular tear film anomalies and lens-related dryness. in Silbert J. ed Anterior Segment Complications of Contact Lens Wear. 2nd ed. Butterworth-Heinemann 2000 :3-21.
3. Albeitz JM. Dry eye : an update on clinical diagnosis, management and promising new treatments. Clinical and Exp Optom 2001;84 :4-18
4. Bron AJ. Understanding dry eye disease : An update on etiology, diagnosis and treatment. Surv Ophthalmol 2001;45 :Supplement 2.
5. Nichols KK. Dry eye : Overview 2000. CL Spectrum 2000;15 :42-47.
6. Lemp MA. Report of the National Eye Institute/Industry Workshop on clinical trials in dry eyes. CLAO J 1995;21 :221-232.
7. Ousler G, Abelson MB. An insider’s look at the NEI dry eye meeting. Rev Ophthalmol 2001;8 :82-84.
8. Terry RL, Schnider CM, Holden BA, et al. CCLRU standards for success of daily and extended wear contact lenses. Optom Vis Sci 1993;70:234-43.
9. Robboy M, Orsborn G, The responses of marginal dry eye lens wearers to a dry eye survey. Contact Lens J 1989;17 :8-9.
10. Doughty MJ et al. A patient questionnaire approach to estimating the prevalence of dry eye symptoms in patients presenting to optometric practices across Canada. Optom & Vis Sci 1997;74 (8):624-631.
11. Begley  CG, Caffery BE, et al. Responses of contact lens weares to a dry eye survey. Optom Vis Sci 2000;77(1) :40-7.
12. Lowther GE. Comparison of hydrogel contact lens patients with and without the symptom of dryness. Int Contact Lens Clin 1993;20 (9/10):191-194.
13. Nichols KK, Begley CG, Caffery B, Jones LA. Symptoms of ocular irritation in patients diagnosed with dry eye. Optom Vis Sci 1999;76 (12):838-844.
14. Sorbara L, Talsky C. Contact lens wear in the dry eye patient: predicting success and achieving it. Can J Optom 1988;50 (4):234-241.
15. Caffery BE, Richter D, Simpson T et al : CANDEES. The canadian dry eye epidemiology study. Adv Exp Med Biol 1998 :438 :805-806.
16. McMonnies CW. Key questions in a dry eye history. J Am Optom Assoc 1986;57 :512-517
17. McMonnies CW, Ho A. Patient history in screening for dry eye conditions. J Am Optom Assoc 1987;58 :296-301
18. Cho P, Yap M. Schirmer test. I. A review. Optom Vis Sci 1993;70 :152-156.
19. Hamano H, et al. A new method for measuring tears. CLAO. 1983;9 :281-289.
20. Efron N. Contact lens-associated meibomian gland dysfunction.  Optician 1998;215 :36-41.
21. Jones L, Jones D. Meibomian gland dysfunction. Optician 1995;209 :30-31.
22. Mainstone JC, Bruce AS, Golding TR. Tear meniscus measurement in the diagnosis of dry eye. Curr Eye Res 1996;15;:653-661.
23. Kwong YM, Cho P. Tear meniscus height in normal and dry eyes : Evaluation using the TOPCON IMAGEnet System. Optom Today 2001;28-31.
24. Cho P. Stability of the precorneal tear film : a review. Clin Exp Optom 1991;74 :19-25
25. Patel S, Murray D, McKenzie A, Shearer DS, McGrath BD. Effects of fluorescein on tear break up time and on tear thinning time. Am J Optom Physiol Optics 1985 ;62 :188-190.
26. Patel S, Bevan R, Farrell JC. Diurnal variation in precorneal tear film stability. Am J Optom Physiol Optics 1988;65 :151-154.
27. Madden RK, Paugh JR, Wang C. Comparative study of two non-invasive tear film stability techniques. Curr Eye Res 1994;13 :263-269.
28. Guillon JP, Guillon M. Tear film examination of the contact lens patient. Optician. 1993;206 :21-29.
29. Norn MS. Vital staining in practice. Acta Ophthalmologica 1964;42 :1046-1053.
30. Norn MS. Lissamine Green : Vital staining of cornea and conjunctiva. Acta Ophthalmologica 1973;51 :483-491.
31. Manning FJ, Wehrly SR, Foulks GN. Patient tolerance and ocular surface staining characteristics of lissamine green versus rose bengal. Ophthalmology 1995;102 :1953-1957.
32. Xu KP, Yagi Y,Tsubota K. Decrease in corneal sensitivity and change in tear function in dry eye. Cornea 1996;15 (3):235-239.
33. Gilbard JP, Gray KL, Rossi SR. A proposed mechanism for increased tear-film osmolarity in contact lens wearers. Am J Ophthalmol 1986;102 (4):505-507.
34. Efron N and Brennan NA, A survey of wearers of low water content hydrogel contact lenses.  Clinical and Experimental Optom 1988;71 (3):86-90.
35. Pritchard N, Fonn D. Dehydration, lens movement and dryness ratings of hydrogel contact lenses. Ophthalmic Physiol Opt 1995;15 (4):281-286.
36. Fonn D, Situ P, Simpson T, Hydrogel lens dehydration and subjective comfort and dryness ratings in symptomatic and asymptomatic contact lens wearers. Optom Vis Sci 1999;76 (10):700-4.
37. Pusch W, Walch A. Membrane structure and its correlation with membrane permeability. J Membrane Science 1982;10:325-360.
38. Andrasko G, The amount and time course of soft contact lens dehydration. J Am Optom Assoc 1982;53 (3):207.
39. Brennan NA and Efron N. Hydrogel lens dehydration : A materials dependent phenomenon? Contact Lens Forum 1987;12 (4):28-9.
40. Efron N, Brennan NA, Bruce S, Duldig DI and Russo NJ. Dehydration of hydrogel lenses under normal wearing conditions. CLAO J 1987;13 (3):152-6.
41. Andrasko G, Hydrogel dehydration in various environments. ICLC 1983;10 :22-8.
42. Kohler J and Flanagan G, Clinical dehydration of extended ­wear lenses. ICLC 1985;12 (3):152-161
43. Brennan NA, Lowe R, Efron N, Ungerer JL, Carney LG. Dehydration of hydrogel lenses during overnight wear. Am J Optom Physiol Opt 1987;64 (7):534-539.
44. Holly F. Tear film physiology and contact lens wear. II. Contact lens-tear film interaction. Am J Physiol Optics 1981;58 :331-341.
45. Caffery BE, Josephson JE. The preocular tear film in contact lens wear. Prac Optom 1992;3 :88-95.
46. Kinney KA. Detecting dry eye in contact lens wearers. CL Spectrum 1998;May :21-28.
47. Westerhout D. Treatment of dry eyes with aqueous antioxidant eye drops. Contact Lens J 1991;19(7);165-173.
48. Young G, Bowers R, Hall B and Port M. Clinical comparison of Omafilcon A with four control materials. CLAO J 1997;23 (4):249-58.
49. Lebow K, Bridgewater B. A three-month comparative daily-wear study of two high-water-content soft lenses. Int Contact Lens Clin 1997;24(6):198-206.
50. Lemp MA, Caffery B et al. Omafilcon A (Proclear) soft contact lenses in a dry eye population. CLAO J 1999;25 (1):40-7.

Other References:

1. Efron N, Golding TR, Brennan NA. The effect of soft lens lubricants on symptoms and lens dehydration. CLAO J 1991;17 (2):114-119.
2. Brennan NA, Lowe R, Efron N, and Harris MG. In vivo dehydration of disposable (Acuvue) contact lenses. Optom Vis Sci 1990;67(3):201-203.
   Efron N, Young G. Dehydration of hydrogen contact lenses in vitro and in vivo. Ophthalmic Physiol Opt 1988;8 (3):253-256.
3. Faber E, Golding TR, Lowe R, Brennan NA. Effect of hydrogel lens wear on tear film stability. Optom Vis Sci 1991;68 (5):380-384.
4. Young G, Efron N. Characteristics of the pre-lens tear film during hydrogel contact lens wear. Ophthalmic Physiol Opt 1991;11 (1):53-58.
5. Little SA, Bruce AS. Postlens tear film morphology, lens movement and symptoms in hydrogel lens wearers. Ophthalmic Physiol Opt 1994;14 (1):65-69.
6. Cedarstaff TH, Tomlinson A. A comparative study of tear evaporation rates and water content of soft contact lenses. Am J Optom Physiol Opt 1983;60 (3):167-174.
7. Sharma A, Ruckenstein E. Mechanism of tear film rupture and its implications for contact lens tolerance. Am J Optom Physiol Opt 1985;62 (4):246-253.
8. Israelachvili J, Wennerstrom H. Role of hydration and water structure in biological and colloidal interactions. Nature 1996;379 (6562):219-225.
9. Brennan NA, Efron N, Truong VT, Watkins RD. Definitions for hydration changes of hydrogel lenses. Ophthalmic Physiol Opt 1986;6 (3):333-338.
10. Allsopp JG. Performance review of a biocompatible monthly disposable lens. Optician 1997;213 (5595):30-32.
11. Bron AJ, Hornby S, Tiffany J, Ursell P. The management of dry eyes. Optician 1997;214 (5613):13-19.
12. Bruce AS, Golding TR, Wai Man Au S, Rowhani H. Mechanisms of dryness in soft lens wear - role of BUT and deposits. Clin Exp Optom 1995;78 (5):168-175.