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Posterior-segment Complications of Keratorefractive Surgery

Retinal Physician January 1, 2010

Posterior-segment Complications of Keratorefractive Surgery

Advice from retinal specialists and refractive surgeons on areas of common concern.

STEPHEN G. SCHWARTZ, MD, MBA ∙ THOMAS A. ALBINI, MD ∙ HARRY W. FLYNN, JR., MD

Posterior-segment complications are unusual following keratorefractive procedures such as laserassisted in situ keratomileusis (LASIK). These complications may be broadly divided into vitreoretinal complications, macular complications and optic nerve complications.

VITREORETINAL COMPLICATIONS

Symptoms consistent with vitreous syneresis or posterior vitreous detachment (PVD) may occur following LASIK, and they are more likely with increasing degrees of myopia.1 Similarly, retinal tear and rhegmatogenous retinal detachment (RD) may be associated with LASIK. RD has been reported less than one day following LASIK in a −12 D myopic patient (spherical equivalent) who had a normal peripheral retina prior to the treatment.2 In two very large series, RD developed in 33 of 38,823 eyes (0.09%) within 60 months of LASIK (mean 16.3 months)3 and in 49 of 59,424 eyes (0.08%) within 76 months of LASIK (mean 27.3 months).4 There were several similarities among the patients reported in the two series, including mean pre-LASIK refraction (about −8.5 D spherical equivalent) and most common location of retinal breaks (temporal quadrants). No matched control group without LASIK was available for comparison in either of these reports.

Recently, a case of culture-negative endophthalmitis was reported following LASIK. A retrobulbar injection of balanced salt solution had been used to prolapse the globe to facilitate the procedure, and this procedure resulted in scleral perforation.5

Stephen G. Schwartz, MD, MBA, Thomas A. Albini, MD, and Harry W. Flynn, Jr., MD, all practice at the Bascom Palmer Eye Institute of the University of Miami Medical Center in Florida. None of the authors report any financial interest in any products mentioned in this article. Dr. Schwartz can be reached via e-mail at sschwartz2@med.miami.edu.

MACULAR COMPLICATIONS

Myopic choroidal neovascularization (CNV) may also be associated with LASIK. In a series of almost 3,000 eyes, 0.10% of subjects developed CNV within 26 months, with a mean interval of 13 months.6 Myopic macular hemorrhage, without associated CNV, has been reported following LASIK,7 including one case with bilateral macular hemorrhages noted 17 days following LASIK in a −16 D myopic patient.8 Subhyaloid (premacular) hemorrhage has been reported less than one day following LASIK in a +4 D hyperopic patient.9

In a retrospective study of almost 84,000 eyes, 0.02% of subjects developed full-thickness macular hole within 83 months of LASIK, with 60% occurring within six months.10 Again, no matched control group without LASIK was available for comparison.

OPTIC NERVE COMPLICATIONS

There have been several reports of optic neuropathy following LASIK, typically occurring within several days of surgery.11 These complications typically appear similar to ischemic optic neuropathies. Optic disc edema may be noted initially, and optic atrophy generally develops (Figure 1). Currently, there is no published estimate of the frequency of this complication.

Figure 1. Post-LASIK optic disc edema with optic atrophy.

The LASIK procedure may also cause changes in retinal nerve fiber layer measurements using the GDx Nerve Fiber Analyzer (Carl Zeiss Meditec, Dublin, CA), but this effect is believed to be an artifact of the altered corneal birefringence, rather than true damage to the nerve fiber layer.12

POSSIBLE ETIOLOGIES

Explanations for various posterior-segment complications of LASIK remain conjectural. There is some suggestion in the literature that the major causative factor is mechanical trauma induced by the suction ring used to fixate the eye while the microkeratome creates the flap.13 Most, if not all, reported posterior-segment complications have occurred following either primary LASIK or LASIK enhancement using a microkeratome to recut the flap. In contrast, LASIK enhancement using flap relifting does not appear to be associated with posterior-segment complications.13

Cutting the flap with a femtosecond laser rather than a microkeratome requires lower suction but longer duration. LASIK with the femtosecond laser has been reported with rhegmatogenous RD,14 macular hemorrhage15 and optic neuropathy.16 Epi-LASIK, which also requires relatively longer suction durations, has been associated with optic neuropathy.17

RECOMMENDATIONS FROM A POSTERIOR-SEGMENT PERSPECTIVE

Myopia is a strong risk factor for many posterior-segment diseases, which represents an important confounding variable. For example, in the largest published series, the annual incidence of RD following LASIK is reported as 0.032%,18 or 32 per 100,000. In contrast, the annual incidence of RD in the general public varies according to the population studied, but it is reported to be about 10.5 per 100,000.19 Compared with emmetropic eyes, myopic eyes with a spherical equivalent between −1 D and −3 D have about four times the increased risk of RD, and myopic eyes with a spherical equivalent greater than −3 D have about 10 times the increased risk.19 Therefore, in any individual case, it is difficult or impossible to prove causation, especially if the RD follows LASIK by one year or more. Nevertheless, patients should be advised of this possibility during the informed-consent process.

If there is, in fact, a causal link between LASIK and posterior-segment disease, and if the suction ring is, in fact, responsible for these complications, then certain recommendations become evident.

A careful preoperative screening evaluation is generally recommended to identify patients with risk factors for posterior-segment complications. For example, patients judged to be at risk for glaucoma,20 as well as patients with myopic lacquer cracks,21 have been suggested as poor candidates for LASIK. Peripheral retinal lesions that predispose to RD should be documented, and some authors have suggested consideration for treatment of these lesions prior to performing LASIK.21

In patients without obvious risk factors, lower suction pressures and shorter durations of suction would seem preferable. There is currently insufficient evidence with which to evaluate the use of the microkeratome versus the femtosecond laser with respect to posterior-segment complications.

When planning surgical treatment of RD following LASIK, certain factors should be considered. Post-LASIK patients may be dissatisfied with the myopic shift following encircling scleral buckling, and alternative techniques (such as segmental scleral buckling, pars plana vitrectomy [PPV], or pneumatic retinopexy) may be considered. If scleral buckling is performed, the vitreoretinal surgeon should understand that the patient may desire future LASIK enhance ment if retinal reattachment is achieved and if good central vision returns. Conjunctival scarring and anterior placement of an encircling buckling element may prevent proper placement of a microkeratome following successful scleral buckling.22

If PPV is chosen to treat RD or macular hole, the surgeon should attempt to protect the corneal flap during surgery. Flap dislocation during PPV has been reported as late as 69 months following LASIK.21 Avoidance of corneal epithelial debridement appears to be important in vitreoretinal surgery for these eyes.

CONCLUSION

Refractive surgeons should be prepared to recognize posterior-segment complications and to either manage them or refer them appropriately. In many cases, excellent anatomic and visual outcomes may be obtained with early recognition and treatment. RP

REFERENCES
  1. Luna JD, Artal MN, Reviglio VE, et al. Vitreoretinal alterations following laser in situ keratomileusis: clinical and experimental studies. Graefes Arch Clin Exp Ophthalmol. 2001;239:416-423.
  2. Reviglio VE, Kuo IC, Gramajo L, et al. Acute rhegmatogenous retinal detachment immediately following laser in situ keratomileusis. J Cat Refract Surg. 2007;33:536-539.
  3. Arevalo J F, Ramirez E, Suarez E, et al. Retinal detachment in myopic eyes after laser in situ keratomileusis. J Refract Surg. 2002;18:708-714.
  4. Faghihi H, Jalali KH, Amini A, et al. Rhegmatogenous retinal detachment after LASIK for myopia. J Refract Surg. 2006;22:448-452.
  5. Han Y, Lam HH, Stewart JM. Endophthalmitis due to inadvertent globe penetration during retrobulbar injection of saline solution for laser in situ keratomileu-sis. J Cat Refract Surg. 2009;35:1132-1133.
  6. Ruiz-Moreno JM, Perez-Santonja JJ, Alio JL. Choroidal neovascularization in myopic eyes after laser-assisted in situ keratomileusis. Retina. 2001;21:115-120.
  7. Principe AH, Lin D Y, Small KW, Aldave AJ. Macular hemorrhage after laser in situ keratomileusis (LASIK) with femtosecond flap creation. Am J Ophthalmol. 2004;138:657-659.
  8. Luna JD, Reviglio VE, Juarez C P. Bilateral macular hemorrhage after laser in situ keratomileusis. Graefe's Arch Clin Exp Ophthalmol. 1999;237:611-613.
  9. Moshfeghi AA, Harrison SA, Reinstein DZ, Ferrone PJ. Valsalva-like retinopathy following hyperopic laser in situ keratomielusis. Ophthalmic Surg Lasers Imaging. 2006;37:486-488.
  10. Arevalo JF, Mendoza AJ, Velez-Vazquez W, et al. Full-thickness macular hole after LASIK for the correction of myopia. Ophthalmology. 2005;112: 1207-1212.
  11. Lee AG, Kohnen T, Ebner R, et al. Optic neuropathy associated with laser in situ keratomileusis. J Cataract Refract Surg. 2000;26:1581-1584.
  12. Nevyas J Y, Nevyas HJ, Nevyas-Wallace A. Change in retinal nerve fiber layer thickness after laser in situ keratomileusis. J Cataract Refract Surg. 2002; 28:2123-2128.
  13. Mirshahi A, Baatz H. Posterior segment complications of laser in situ keratomileusis (LASIK). Surv Ophthalmol. 2009;54:433-440.
  14. Hori S, Shimada H, Hattori T, et al. Early onset of rhegmatogenous retinal detachment after LASIK with femtosecond laser. Jpn J Ophthalmol. 2009;53:75-76.
  15. Principe AH, Lin DY, Small KW, Aldave AJ. Macular hemorrhage after laser in situ keratomileusis (LASIK) with femtosecond flap creation. Am J Ophthalmol. 2004;138:657-659.
  16. Maden A, Yilmaz S, Yurdakul NS. Nonarteritic ischemic optic neuropathy after LASIK with femtosecond laser flap creation. J Neuroophthalmol. 2008;28: 242-243.
  17. Montezuma SR, Lessell S, Pineda R. Optic neuropathy after epi-LASIK. J Refract Surg. 2008;24:204-208.
  18. Faghihi H, Jalali KH, Amini A, et al. Rhegmatogenous retinal detachment after LASIK for myopia. J Refract Surg. 2006;22:448-452.
  19. Mitry D, Charteris DG, Fleck BW, Campbell H, Singh J. The epidemiology of retinal detachment: geographic variation and clinical associations. Br J Ophthalmol. 2009 Jun 9 [Epub ahead of print].
  20. Nevyas J Y, Nevyas HJ, Nevyas-Wallace A. Change in retinal nerve fiber layer thickness after laser in situ keratomileusis. J Cataract Refract Surg. 2002;28: 2123-2128.
  21. Arevalo J F. Posterior segment complications after laser-assisted in situ ker-atomileusis. Curr Opin Ophthalmol. 2008;19:177-184.
  22. Barequet IS, Levy J, Klemperer I, et al. Laser in situ keratomileusis for correction of myopia in eyes after retinal detachment surgery. J Refract Surg 2005; 21:191-193.
Recommendations From an Anterior-segment Perspective
TERRENCE P. O'BRIEN, MD ∙ JONATHAN ETTER, MD

Although LASIK surgery is among the most frequently performed outpatient ophthalmic procedures, posterior-segment complications of LASIK are fortunately rare.

The most significant adverse events involving the posterior pole after LASIK have been mentioned above and include rhegmatogenous retinal detachment, macular and submacular hemorrhage, and optic nerve compromise. Given the paucity of these events, little is known regarding their etiology.

Overall, it is felt that flap creation with suction ring is the most potentially dangerous portion of LASIK, whereas excimer laser is thought to have minimal ability to cause posterior-segment damage.1 Traditional automated mechanical microkeratomes employ a suction ring and increase intraocular pressure to over three times what is considered physiologic. IOP increases even more when the microkeratome blade is used to create a corneal flap. Moreover, these alterations in IOP likely alter vector forces within the eye, which predispose patients to vitreous traction and possibly retinal tears.2 Other surgeons hypothesize that increased IOP induced by the suction ring also compromises optic nerve perfusion, which can lead to ischemia and visual field loss.3

Recently, use of the femtosecond laser for flap creation has increased. While the femtosecond laser still employs a suction ring, there is not as dramatic a rise in IOP during flap creation when compared to that generated by the microkeratome. Many physicians feel that the diminished vacuum level associated with femtosecond flap creation is less harmful to the posterior segment.

This sentiment is slightly controversial. Despite the fact that femtosecond flap creation results in less of an overall IOP spike, it maintains an increased IOP for a longer period of time than newer automated mechanical microkeratomes. There are surgeons who believe that increased suction duration is more deleterious to optic nerve perfusion.4,5 There are newer-model femtosecond lasers that use curved contact glass to support the cornea for flap creation. This technique reportedly results in minimal IOP alteration. It will be interesting to see whether the introduction of these newer modalities with femtosecond lasers will change the incidence of posterior-segment complications.

As general rule, it is very important to conduct a meticulous examination of the posterior pole prior to performing refractive surgery. Great caution must be demonstrated when considering refractive surgery in patients with glaucoma, nerves at risk of ischemic optic neuropathy, or peripheral retinal pathology and in those patients with high degrees of myopia.

Patients with high myopia are especially abundant in the refractive clinic because it is often those patients who are most dependent on spectacle correction and who are most debilitated without correction. It cannot be overstated enough that, if there is any question regarding the status of the posterior pole in a potential refractive surgical patient, it is beneficial to have that patient evaluated by a retinal subspecialist. Additionally, if there is concern regarding the potential effects of flap creation in a patient (and the patient is still a good candidate for refractive surgery in general), it may be advantageous to consider advanced surface ablation as an alternative to application of suction if suitably indicated.

  1. Krueger RR, Seiler T, Gruchman T, et al. Stress wave amplitudes during laser surgery of the cornea, Ophthalmology. 2001;108:1070-1074.
  2. Mirshahi A, Schopfer D, Gerhardt D, et al. Incidence of posterior vitreous detachment after laser in situ keratomileusis, Graefes Arch Clin Exp Ophthalmol. 2006;244:149-153.
  3. Bushley DM, Parmley VC, Paglen P. Visual field defect associated with laser in situ keratomileusis, Am J Ophthalmol. 2000;129:668-671.
  4. Maden A, Yilmaz S, Yurdakul NS. Nonarteritic ischemic optic neuropathy after LASIK with femtosecond laser flap creation, J Neuroophthalmol. 2008;28: 242-243.
  5. Montezuma SR, Lessell S, Pineda R. Optic neuropathy after epi-LASIK, J Refract Surg. 2008;24:204-208.

Terrence P. O'Brien, MD, and Jonathan Etter, MD, practice at the Bascom Palmer Eye Institute of the University of Miami Medical Center in Florida. Neither author reports any financial interest in any products mentioned in this article. Dr. O'Brien can be reached via e-mail at tobrien@med.miami.edu.

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