Myths and Realities of Post-LASIK Dry Eye

Pretreatment of ocular surface disease and thin-flap protocols can alleviate most concerns.

BY WILLIAM TRATTLER, MD AND PARAG A. MAJMUDAR, MD

Laser vision correction has been shown in numerous studies to provide very good visual results for the vast majority of individuals, with a low rate of intraoperative and postoperative complications.^1,2 However, at the FDA hearings on LASIK conducted in the summer of 2008, the most common complaint from a small group of dissatisfied LASIK patients was chronic dry eye. There has been a considerable amount of research looking into the reasons for the development of dry eye post-LASIK. In addition, research has looked at steps that can be taken to minimize the risk of developing dry eye and to minimize the severity of dry eye if it were to occur post-LASIK. However, despite greater understanding of post-LASIK dry eye, there remain a variety of controversies.

Identifying Dry Eye Prior to LASIK

One area in the discussion of dry eye and LASIK is not controversial. That is: it is critical to evaluate patients interested in LASIK for the presence and severity of dry eye and blepharitis. Patients presenting for consideration of LASIK often report issues of contact lens intolerance. A careful evaluation of the ocular surface with fluorescein dye will help evaluate the quality of tears with a tear break up time test and also reveal the presence of any corneal staining. Evaluation of the eyelids will determine if there are any signs of anterior or posterior blepharitis.

If dry eye or blepharitis is present, it is critical to treat the condition prior to performing the final measurements for the procedure. Dry eye and blepharitis often lead to inaccurate refraction, topographic abnormalities and a poor quality wavefront analysis, all of which can contribute to a suboptimal refractive result with either PRK or LASIK.

Further, untreated dry eye will lead to an increased level of dry eye postoperatively. Treatment options include topical cyclosporine, a pulse of topical steroids, punctal plugs, and lubricating drops and gels. Blepharitis can be treated with topical azithromycin, warm compresses and lid scrubs if needed.

Lissamine green staining revealed mild dry eye that required pretreatment to achieve optimal results.

The Impact of Corneal Sensitivity

One of the main theories on the underlying cause of dry eye following LASIK is related to the creation of a LASIK flap and the associated reduction in corneal sensitivity. Since tears are secreted based on a neural-feedback loop, a disruption of the loop due to a desensitized cornea can lead to reduced tear production and dry eye signs and symptoms.

Studies have shown that it can take months to even years for corneal sensation to return to normal following LASIK. The timeframe for normalization of corneal sensitivity has been correlated to the thickness of the flap and depth of laser ablation. Additionally, the presence of untreated dry eye preoperatively has been shown to dramatically reduce corneal sensitivity postoperatively, compared to patients without pre-existing dry eye. This may significantly prolong the recovery of corneal sensitivity postoperatively.³

A recent study demonstrated that topical cyclosporine may help speed the return of corneal sensitivity following LASIK.⁴ The mechanism, although unknown, theoretically could be related to reducing ocular surface inflammation and an improvement in the quality of the tear film.

Flap Factors for Dry Eye After LASIK

Researchers have long debated issues regarding surgical technique and the degree to which they increase the risk of dry eye. With LASIK, early research suggested that flaps with superior hinges were more likely to lead to postoperative dry eye.⁵ A study conducted at Baylor found that even in eyes with no preoperative signs of dry eye, 41% of superior-hinged flaps compared to just 31% of eyes with nasal flap hinges experienced dry eye at the six-month postoperative visit. Eyes with superior flap hinges had a worse tear break up time at all time points tested from one week to six months postoperatively compared to eyes treated with nasal flap hinges.

Other researchers have suggested that PRK leads to less dry eye than LASIK, since no flap is cut, and the total depth of the treatment within the cornea is less.⁶

A study by Dan Durrie, MD and Steve Slade, MD suggested that thin, planar LASIK flaps created with the femtosecond laser are less likely to induce dry eye signs and symptoms compared to microkeratome flaps.⁷ The same study also found that in comparison to surface ablation, the signs and symptoms of dry eye were similar when a thin, custom planar femtosecond flap is created.

Is There Hope for Patients With Severe Post-LASIK Dry Eye?

Just as patients who have never undergone LASIK can develop severe dry eye, it is possible for some patients to develop severe dry eye following LASIK. There are a variety of advanced treatment options for these patients. In one study of severely dry patients post-LASIK, researchers suppressed inflammation with preservative-free topical steroids.⁸

Once the ocular surface inflammation was under control, the investigator closed the puncta inferiorly, and as needed, superiorly. Finally, the researcher instituted a therapy consisting of heat to the eyelids. The study found that all patients achieved a significant resolution of their signs and symptoms.

Other treatment options for severe dry eye patients include Lacrisert, which provides sustained release of artificial tears, and autologous serum drops. Oral supplementation with omega fatty acids may also be beneficial in certain cases. Additionally, many severely dry patients have a component of evaporative dry eye, so addressing any meibomian gland dysfunction can be helpful.

Mild punctate staining after LASIK.

Summary

Dry eye is a common condition following both PRK and LASIK, but the risk of developing permanent dry eye symptoms can be reduced by identifying and treating dry eye preoperatively as well as continuing treatment postoperatively. Modifications in surgical technique, such as creating thin, planar femtosecond flaps or performing surface ablation can potentially help reduce the incidence and severity of post-laser vision correction dry eye. Finally, if dry eye persists after LASIK, it is important to counsel patients that it is a treatable condition.

References

1. Liu Z, Li Y, Cheng Z, Zhou F, Jiang H, Li J. Seven-year follow-up of LASIK for moderate to severe myopia. J Refract Surg. 2008 Nov;24(9):935-40.
2. Ang EK, Couper T, Dirani M, Vajpayee RB, Baird PN. Outcomes of laser refractive surgery for myopia. J Cataract Refract Surg. 2009 May;35(5):921-33.
3. Albietz JM, Lenton LM, McLennan SG.; Effect of laser in situ keratomileusis for hyperopia on tear film & ocular surface. J Refract Surg. 2002 Mar-Apr;18(2):113-23.
4. Donnenfeld E, Pflugfelder SC: Topical ophthalmic cyclosporine: pharmacology and clinical uses. Surv Ophthalmol. 2009 May-Jun;54(3):321-38.
5. De Paiva CS, Chen Z, Koch DD, Hamill MB, Manuel FK, Hassan SS, Wilhelmus KR, Pflugfelder SC.;The incidence and risk factors for developing dry eye after myopic LASIK. Am J Ophthalmol. 2006 Mar;141(3):438-45.
6. Lee HK, Lee KS, Kim HC, Lee SH, Kim EK. Nerve growth factor concentration and implications in photorefractive keratectomy vs laser in situ keratomileusis. AJO. 2005 June;139(6):965-71.
7. Slade SG, Durrie DS, Binder PS. A prospective, contralateral eye study comparing thin-flap LASIK (sub-Bowman keratomileusis) with photorefractive keratectomy. Ophthalmology. 2009 Jun;116(6):1075-82.
8. Di Pascuale M, Liu T, Trattler W, Tseng S. Lipid Tear Deficiency in Persistant Dry Eye After Laser in situ Keratomileusis and Treatment Results of New Eye-Warming Device; J Cataract Refract Surg. Sep 05; 32 (9)1741-49.