Eyeworld

Supported by Alcon Laboratories Inc., Allergan Inc., Shire Pharmaceuticals, TearLab, and TearScience 7 density decreased significantly, as demonstrated on conjunctival impression cytology, and it did not recover three months after surgery. 14 This reduction was highly associated with time in surgery. Figure 2. Tear film structure and composition Figure 1. Refractive index Refractive index Air 1.00 Tear film 1.34 Cornea 1.38 Aqueous humor 1.33 Crystalline lens 1.41 Vitreous humor 1.34 Furthermore, BAK-contain- ing postoperative drops may cause additional surface toxicity, eye disease may worsen if patients stop or decrease their topical treatments, and meibomian gland disorder may worsen if patients stop using warm compresses and lid hygiene. Conclusion The tear film is the first and most important refractive interface in the eye. Irregularities may result from dry eye, evaporation, or long between-blink intervals, degrad- ing image quality and affecting patient comfort and refractive outcomes after surgery. References 1. Palanker D. Optical Properties of the Eye. AAO One Network, Oct. 28, 2013. 2. Tutt R, et al. Optical and visual impact of tear break-up in human eyes. Invest Ophthalmol Vis Sci. 2000;41:4117–4123. 3. Montés-Micó R. Role of the tear film in the optical quality of the human eye. J Cat- aract Refract Surg. 2007;33:1631–1635. 4. Goto E, et al. Impaired functional visual acuity of dry eye patients. Am J Ophthal- mol. 2002;133:181–186. 5. Benito A, et al. Objective optical as- sessment of tear-film quality dynamics in normal and mildly symptomatic dry eyes. J Cataract Refract Surg. 2011;37:1481– 1487. 6. Németh J, et al. Corneal topogra- phy changes after a 15 second pause in blinking. J Cataract Refract Surg. 2001;27:589–592. 7. Shtein RM. Post-LASIK dry eye. Expert Rev Ophthalmol. 2011;6:575–582. 8. The epidemiology of dry eye disease: report of the Epidemiology Subcommittee of the International Dry Eye WorkShop (2007). Ocul Surf. 2007;5:93–107. 9. Lee JB, et al. Comparison of tear secretion and tear film instability after photorefractive keratectomy and laser in situ keratomileusis. J Cataract Refract Surg. 2000;26:1326–1331. 10. Broadway DC, et al. Adverse effects of topical antiglaucoma medication. Arch Ophthalmol. 1994;112:1437–1445. 11. Baudouin C, et al. Short-term com- parative study of topical 2% carteolol with and without benzalkonium chloride in healthy volunteers. Br J Ophthalmol. 1998;82:39–42. 12. Kohlhaas M. Corneal sensation after cataract and refractive surgery. J Cataract Refract Surg. 1998;24:1399–1409. 13. Donnenfeld ED, et al. CLEAR Trial. 14. Oh T, et al. Changes in the tear film and ocular surface after cataract surgery. Jpn J Ophthalmol. 2012;56:113–118. Dr. Farid is associate professor of ophthalmology, director of cornea, cataract, and refractive surgery, and vice chair of ophthalmic faculty, Gavin Herbert Eye Institute, Univer- sity of California, Irvine. She can be contacted at mfarid@uci.edu.

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