Ask Dr. Nick Tarantino: Health of the Tear Film

Nicholas Tarantino, OD, FAAO, is head of global clinical research & development at Abbott Medical Optics Inc.

Q: What is the new definition of dry eye from the International Dry Eye Workshop (DEWS)?

A: Dry eye is a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance and tear film instability with potential damage to the ocular surface.¹ It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface.

Q: How is this different from contact-lens-related dry eye?

A: Contact lenses can contribute to tear film thinning and evaporative dry eye, and ocular surface irritation can trigger an inflammatory response.

Q: How do tear dynamics contribute to ocular health and good vision?

A: The tear film helps smooth out irregularities on the corneal refractive surface to improve refraction at the tear film. It removes environmental contaminants from the bulbar surfaces and it lubricates the corneal epithelium.

Q: What do you look for to ensure ocular health in contact lens wearers?

There are three options I approach in this order — certainly you can mix and match:

A: The table below summarizes the main variables (See "Variables for good ocular health with contact lens wear.").

Q: How do contact lenses contribute to dry eye? How is this being studied?

A: Contact lenses divide the tear film into two parts, the pre- and post-lens tear film. Alteration of the tear system during contact lens wear may contribute to dry eye. Chen et al² used optical coherence tomography to image and measure volumes in the tear menisci of each of 20 patients in 3 groups. Group 1 consisted of soft contact lens wearers with selfreported dryness. Group 2 consisted of asymptomatic wearers. Group 3 consisted of asymptomatic non-contact lens wearers. Tear volumes were lower in the 2 groups of symptomatic wearers.

Additionally, interferometry has shown tear film thinning behavior and tear film thickness to be promising areas of research for the treatment of patients with dry eye.³

References

1. International Dry Eye WorkShop. Ocular Surf. 2007;5:75-92.
2. Chen Q et al. Invest Ophthalmol Vis Sci. 2009;50:3159-3163.
3. Huth S et al. Interferometry poster. American Academy of Optometry. Oct. 22-25, 2008. Anaheim, Calif.