Keratos - Post LASIK (& other refractive surgery-induced) Dry Eye

Refractive operations to corrrect myopia, hyperopia and astigmatism are often presented as a compete liberation of constraints (but to be honest just from using glasses!). Nevertheless, LASIK and other refractive surgeries - PRK, LASEK, Excimer, are nonetheless invasive operations and any such intervention carries more or less risks depending on individual fragilities. Short term to very long term dry eyes and corneal impaired healing are just some of these "inconveniences". If you are wondering wether or not to pursue such an operation jjust for aesthetical reason (avoid glasses) or because you can no longer tolerate contact lenses due to mild dry eyes: Keratos cannot answer directly to your query but we may give our general opinion on such procedures for aesthetical or practical reasons only.

The last call pertains to the ophthalmologist, however an association such as Keratos can only dissuade this type of intervention for aesthetical or practical reasons only when a therapeutical risk exists, even for persons who did not present previously any contraindication. One of the possible complications is indeed dry eyes, which is clearly underestimated by many ocular surgeons - although severe dryness is clearly a huge handicap - and probably worse corneal healing impairment. These "side-effects" are said to occur in a minority of cases. Amongst Keratos' members, we have a few examples of this unfortunate minority... often silent... but much more important than most people are lead to believe. Some of them have testified of their plight... (see bellow).

According to medical litterature, it is obvious that this intervention is all the more unadvisable when a person already suffer from dry eyes or some kind of corneal healing or lachrymal impairment. You may ask for a second or third independent opinion, and we would be surprised if there were no negative opinion regarding that surgery. At their first signs of reticence, it would certainly be better to refrain from taking such risk for entirely aesthetical or practical reasons. Modern ophthalmology is able to correct visual defaults (with more of less success actually) but it is still unable to re-establish a normal corneal sensitivity or a lachyrmal function when these are impaired. Living with constant pain and using constantly eye drops cannot be seen as a panacea. Eye drops are usually insufficient to achieve relief.

Many eye centers sell these interventions as having no side-effects and just benefits, but the simple fact that person who underwnet LASIK and other refractive surgeries is disqualified as corneal graft donor in many countries, suggest that the future may not be that "bright" and that these interventions induce signigicant alterations of the properties of the cornea.

Additional information on refractive surgeries and links:

LASIK is the contraction of LASer In situ Keratomileusis. A keratomileusis ( meaning refractive surgery), is a surgery to destined to modify the optic convergence of the eye by re-shapping the corneal surface to correct myopia and hyperopia. However, there are other refractive surgeries such as PRK ("photo-refractive keratectomy"), Excimer, LASEK (more similar to PRK than to LASIK), Epi-LASIK, Intralase, LASIK wavefront, etc.

Any refractive surgery remains an invasive surgical procedures. Thus, complications cannot be totatally discarted. One of the main complications is dry eyes probably due to reduced corneal sensitivity after the operation. In principle, the eye is said to recover most of the sensitivity in the 6 following months. But some people suffer from theses sequels for several years and chronic dryness sets in demonstrating that the said recovery might not be sufficient to avoid. Amongst our members we have several cases of persons suffering from LASIK induced dryness for at least 6 years, which were deemed to be ideal candidates before surgery. Some of these have even suffered from ulcerations episodes that have left significants corneal scars leading to a reduced eyesight. These "symptoms" can objectively been seen using corneal staining tests, reduced Tear Break-up Time, reduced corneal sensitivity, reduced visual acuity (notably when compared to the visual acuity obtained previously using glasses and contact lenses).

Apparently the major cause of dry eyes after refractive surgery is corneal hypoaesthesia (reduced sensitivity) since corneal nerves are severed during the operation. As such, LASIK induced dry eyes may be considered a very mild form of Neurotrophic Keratitis, with which it shares the same challenges. In all these situations, the nerves, which normally enable to maintain the regular lachrymal metabolism are unable to defend the eye from any type of aggression including direct air contact. The sensitivity reduction affects all defence mechanisms, including reflex tears, aqueous, lipid and mucin production, the frequency of blinking, etc...

In the absence of the nerve signals enabing to maintain the mechanisms a dry eye state appears. Let's not forget that lachrymal function relies on one functional unit combining tears (and the various lachrymal glands), the eye surface and its alert and communication system: nerves. These eyes, just as neurotrophic eyes, suffer from dryness but may not feel it or worse feel it but cannot react to it. However, other mechanisms may be involved as well besides hypoaesthesia.

One major public health issue is: considering that age aggravates both dryness and loss of sensivitivity and that these reduce the regeneration and defence capacities of the eye surface, is it reasonnable to continue to offer these interventions in such a large scale without knowing what the consequences will be in in the very long term or without knowing how to circumvene the its side effects. By long term, we are considering old age as well. We don't have enough experience to consider the consequences. As said above, these persons are often disqualified as corneal donors for some reason. This leads us to believe that to additional aspects should be considered: the operation modifies the properties of the normal cornea and the shortage of donated corneas is likely to become more than dramatic.

A recent study by doctor Tseng has demonstrated that the lipid deficiency due to the meibomius glands is one the predominent cause of dry eyes in post lasik dry eye. "Persistent nature of dry eye after LASIK is attributed to in part to delayed tear clearance, undercorrected aqueous tear deficiency, and nonrecognized lipid tear deficiency".

Lipid tear deficiency in persistent dry eye after laser in situ keratomileusis and treatment results of new eye-warming device. Di Pascuale MA, Liu TS, Trattler W, Tseng SC. Ocular Surface Center, Miami, Florida 33173, USA. Cataract Refract Surg. 2005 Sep;31(9):1741-9. PMID: 16246778.

Most studies, however, indicate that LASIK-induced dry eye is due to the severed corneal nerves in the cornea. Thus confirming the theory of neuro-lachrymal unit. Nevertheless, the lipid deficiency itself may be caused by the severed nerves and loss of corneal sensitivity. A similar conditions has been reported in neurotrophic keratitis.

Another study by Plugfelder and al. states that "Dry eye occurs commonly after LASIK surgery in patients with no history of dry eye. The risk of developing dry eye is correlated with the degree of preoperative myopia and the depth of laser treatment."

The incidence and risk factors for developing dry eye after myopic LASIK. De Paiva CS, Chen Z, Koch DD, Hamill MB, Manuel FK, Hassan SS, Wilhelmus KR, Pflugfelder SC. Am J Ophthalmol. 2006 Mar;141(3):438-45. PMID: 16490488

Regarding the NGF could play in the treatments of dry eyes after LASIK:

The effect of nerve growth factor on corneal sensitivity after laser in situ keratomileusis. Joo MJ, Yuhan KR, Hyon JY, Lai H, Hose S, Sinha D, O'Brien TP, Wilmer Eye Institute, The Johns Hopkins Hospital, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA, Arch Ophthalmol. 2004 Sep;122(9):1338-41.

A study carried out by a panel of refractive surgery specialists for the American Academy of Ophthalmology states that "side effects such as dry eyes, night time starbursts, and reduced contrast sensitivity occur relatively frequently":

Laser in situ keratomileusis for myopia and astigmatism: safety and efficacy: a report by the American Academy of Ophthalmology. Sugar A, Rapuano CJ, Culbertson WW, Huang D, Varley GA, Agapitos PJ, de Luise VP, Koch DD. Ophthalmic Technology Assessment Committee 2000-200, Refractive Surgery Panel. Ophthalmology. 2002 Jan;109(1):175-87.