2

Indications and Contraindications of LASIK

Jeewan S Titiyal, Rakesh Ahuja, Namrata Sharma

Laser in situ keratomileusis (LASIK) is one of the most popular techniques for the correction of refractive errors myopia, hyperopia and astigmatism. However, a proper patient selection is of vital importance in accomplishing optical visual outcomes. A patient is selected to undergo LASIK on the basis of proper ophthalmologic screening and personal requirements.

INDICATIONS OF LASIK

The most common indication for LASIK surgery in the present times is myopia, although it is also being increasingly utilized to treat hypermetropia and astigmatism.1–7 Other indications in which LASIK may be performed are anisometropia, induced refractive errors after other surgical procedures such as penetrating keratoplasty, radial keratotomy or cataract surgery.8 Recently, LASIK has also been undertaken to treat presbyopia although the option of mono vision is also possible in these patients and may be offered to them.9–12 Irrespective of the indications a patient who undergoes LASIK has certain basic requirements to be fulfilled (Table 2.1)

Myopia

Laser-in-situ keratomileusis (LASIK) has been used to treat myopia ranging from −1 to −29 dioptres.13 However the optimum correction is done for myopia up to −12.00 diopters since correction of myopia of more than −12 diopters (depending on the corneal thickness) entails excessive stromal ablation with a danger of producing corneal ectasia. It is important to remember that the amount of myopic correction possible in a particular patient is determined by the central corneal pachymetry and correction of myopic refractive errors in excess of −12 dioptres may not be possible if the central pachymetry is less than 500 µm. For myopia, we recommend that treatment be done up to −12 diopters, if corneal thickness allows the desired ablation with a residual bed thickness of 250 µm or preferably of 300 µm as cases ectasia has been noted in cases of residual bed thickness of >250 µm.14

Indications and contraindications of LASIK 9

Figure 2.1 Videokeratography in a case of keratoconus

Figure 2.2. Orbscan showing thin cornea—Contraindication for LASIK

Step by step LASIK surgery 10

Residual Refractive Errors after Previous Surgical Procedures

LASIK has also been used to treat residual refractive errors after radial keratotomy, penetrating keratoplasty, epikeratoplasty and cataract surgery8. Although there are no separate nomograms for LASIK after these procedures optimal surgical results have been reported by various authors. It is vital to ensure adequate wound healing and rule out corneal thinning prior to considering LASIK surgery in these patients.

CONTRAINDICATIONS OF LASIK

Since LASIK is an elective surgery, any condition that would counter a safe result postLASIK should be looked for and patient counseling should be done to deter the patient from having surgery, thereby avoiding complications, unfavorable results and a dissatisfied patient. Contraindications of LASIK include absolute and relative conditions (Table 2.2).

Table 2.2: Patient exclusion criteria for LASIK

1.Ectatic corneal disease

2.Thin corneas

3.Active ocular infection

5.Glaucoma (especially if a large bleb is present)

6.Blepharophimosis

7.Monocular patients

8.Large pupil size

9.Systemic or retinal vascular disorder

10.Autoimmune disease

11.Pregnancy

Absolute Contraindications for LASIK

In certain cases, LASIK is absolutely contraindicated and should not be undertaken. Refractive instability is important to document, as results are not predictable in such

eyes and the patient may become dissatisfied due to requirement of glasses soon after surgery.

Indications and contraindications of LASIK 11

Figure 2.3. Orbscan showing posterior corneal elevation more than 40 µm

Conditions such as ectatic corneal diseases like keratoconus (Fig. 2.1), Terrien’s and pellucid marginal degeneration 16–18 may be aggravated by LASIK and lead to severe ectasia and decrease in the best corrected visual acuity. LASIK should also not be performed in forme fruste kertoconus or subclinical cases of keratoconus. Further, the posterior corneal elevation pre-operatively should be greater than at least 40 µm.19

Patients with a thin cornea of thickness of less than <490 µm should not undergo LASIK since there is not enough cornea available to ablate and correct the refractive error (Fig. 2.2). It may lead to ectasia and associated problems. LASIK surgery is also contraindicated in any case where preoperative corneal thickness does not allow 250 or preferably 300 µm of residual stromal bed following laser ablation. The posterior corneal elevation before LASIK should be less than 40 µm. This is important to avoid occurrence of posterior ectasia of the cornea. LASIK surgery is also contraindicated in any case where preoperative corneal thickness does not allow 250 or preferably 300 µm of residual stromal bed following laser ablation. This is important to avoid occurrence of posterior ectasia of the cornea.

Presence of any other active corneal pathology and severe ocular surface disease like Steven-Johnson’s syndrome and ocular cicatricial pemphigoid is an absolute contraindication for LASIK.

LASIK should not be performed in cases of glaucoma, either known previously or diagnosed immediately prior to surgery, as during the suction ring application the intraocular pressure raises to greater than 65 mm Hg. This may lead to further damage to the optic nerve and loss of vision.

In pregnant or nursing women or women planning to conceive in the next 6–12 months, LASIK is not predictable because of change in corneal hydration and refraction. Hence, it should not be performed.

Step by step LASIK surgery 12

Relative contraindications for LASIK

Patients on certain medications like oral or topical steroids or taking hormone replacement therapy are likely to have delayed healing which may interfere with the results of LASIK surgery. In such cases, the indication for taking steroids should be discussed and the patient advised to refrain from undergoing surgery.

Patients with disorders like diabetes, collagen vascular disease, autoimmune or immunodeficiency diseases, patients with a history of keloid formation, or in patients with a tendency to form scars, which are likely to lead to unpredictable results after LASIK, should be not be operated.

Patients with any previous history of Herpes simplex or Herpes zoster in the eye may not be operated, since these may be reactivated by LASIK.20

In blepharophimosis and patients with small palpebral apertures, LASIK may be more difficult to perform with the currently available microkeratomes. This may change with the introduction of newer techniques of flap making using femto-second laser, which does not require placement of suction ring.

Any active ocular infection or inflammation like conjunctivitis and scleritis is a contraindication for performing LASIK. Local diseases like blepharitis, meibomitis, severe atopic disease, and a poor ocular surface, which are likely to lead to tear film instability after LASIK may not be operated. Corneal neoυascularization within 1.0 mm of the ablation zone is also a relative contraindication, since there is increased risk of interface hemorrhage. LASIK should preferably be avoided in monocular patients. Dry eye, sunken eye, a pupil size larger than the optic zone for the laser ablation, systemic or ocular vascular disease are some of the other relative contraindications for LASIK.

LASIK may be contraindicated in certain occupations and both the current and the future occupational requirements of the patient are an important criterion in determining whether one should undergo LASIK surgery. Armed forces, fighter pilots as well as the Railways have certain regulations regarding visual fitness, which should be obtained from the source and referred to by the patient.21 These regulations may or may not allow performance of LASIK to obtain a 6/6 vision. Depending upon these regulations, a particular patient may or may not be operated.

Patients indulging in contact sports or athletes should be explained the risk of flap dehiscence and globe rupture from a minimal or trivial trauma. Professional scuba divers should be informed that waiting a minimum of one month would be required before resuming diving after LASIK. This is important since they may have potential complications like globe rupture from facemask barotraumas, interface keratitis and flap displacement from interface bubbles.

Of particular importance are the patients whose occupation is dependent on the quality of the visual function based on contrast sensitivity and glare. The contrast sensitivity may decrease after LASIK. So, it is possible that following LASIK treatment, patient may find it more difficult than usual to see in very dim light, rain, fog, or experience glare from oncoming vehicles at night. Visual performance may be worsened by a larger mesopic pupillary size.

Hori-Komai have analyzed the reasons for not performing laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) in 2784 patients who requested surgical correction of their refractive errors.22 Out of these, 2079 patients (74.7%) had PRK or LASIK and 705 patients (25.3%) did not. The reasons they did not receive refractive

Indications and contraindications of LASIK 13

surgery (PRK or LASIK) were myopia greater than −12.0 diopters and/or high astigmatism (20.7%), insufficient corneal thickness (8.2%), keratoconus (6.4%), cataract (5.7%), and hyperopia and/or hyperopic astigmatism (4.1%).

In conclusion, the safety and effectiveness of the excimer laser have not been established in patients with unstable or worsening myopia or astigmatism, higher degree of refractive error, diseased or abnormal corneas and any previous insults to the cornea. In such cases, LASIK should not be performed.

REFERENCES

1.Buratto L, Ferrari M. Indications, techniques, results, limits, and complications of laser in situ keratomileusis. Curr Opin Ophthalmol. 1997; 8(4):59–66.

2.Mulhern MG, Condon PI, O’Keefe M. Myopic and hyperopic laser in situ keratomileusis retreatments: indications, techniques, limitations, and results. J Cataract Refract Surg. 2001; 27(8):1278–87.

3.Gimbel HV, Levy SG. Indications, results, and complications of LASIK. Curr Opin Ophthalmol. 1998; 9(4):3–8.

4.Malecha MA, Holland EJ. Correction of myopia and astigmatism after penetrating keratoplasty with laser in situ keratomileusis. Cornea. 2002;21 (6):564–69.

5.Bains RA, Perreault S, Braun DA, Penno EEA, Gimbel HV. Patient Education, Assessment and Informed Consent. In: Refractive Surgery: A manual of principles and practice. Ed. Gimbel HV, Penno EEA. SLACK Inc. Thorofare, NJ. 2000; 23–38.

6.Bains RA, Penno EEA, Gimbel HV. Myopia, Hyperopia and Astigmatism In: Refractive Surgery: A manual of principles and practice. Ed. Gimbel HV, Penno EEA. SLACK Inc. Thorofare, NJ. 2000; 17–22.

7.Bains RA, Penno EEA, Gimbel HV. Laser in-situ keratoileusis In: Refractive Surgery: A manual of principles and practice. Ed. Gimbel HV, Penno EEA. SLACK Inc. Thorofare, NJ. 2000; 127– 57, 2000.

8.Guell JL, Gris O, de Muller A, Corcostegui B. LASIK for the correction of residual refractive errors from previous surgical procedures. Ophthalmic Surg Lasers. 1999; 30(5):341–49.

9.Jain S, Ou R, Azar DT. Monovision outcomes in presbyopic individuals after refractive surgery. Ophthalmology. 2001; 108(8):1430–33.

10.Sippel KC, Jain S, Azar DT. Monovision achieved with excimer laser refractive surgery. Int Ophthalmol Clin. 2001;41(2):91–101.

11.Boyd BF, Krueger R, Murube J. McDonald M, Wilson S. LASIK in Presbyopia. In: LASIK and Beyond LASIK. Ed. Boyd BF. Highlights of Ophthalmology Intl, Panama, Panama. 2001; 427– 33.

12.Avalos-Urzua G, Silva-Lepe A. Presbyopia. In: LASIK and Beyond LASIK. Ed. Boyd BF. Highlights of Ophthalmology Intl, Panama, Panama. 2001; 435–448.

13.Knorz MC, Liermann A, Seiberth V, Steiner H, Wiesinger B. Laser in situ keratomileusis to correct myopia of -6.00 to −29.00 diopters. J Refract Surg 1996; 12(5):575–84.

14.Ou RJ, Shaw EL, Glasgow BJ. Keratectasia after laser in situ keratomileusis (LASIK): evaluation of the calculated residual stromal bed thickness. Am J Ophthalmol. 2002; 134(5):771–73.

15.Salz JJ, Stevens CA. LASIK correction of spherical hyperopia, hyperopic astigmatism, and mixed astigmatism with the LADARVision excimer laser system. Ophthalmology. 2002; 109(9): 1647–56.

16.Schmitt-Bernard CF, Lesage C, Arnaud B. Keratectasia induced by laser in situ keratomileusis in keratoconus. J Refract Surg. 2000; 16(3):368–70.

Step by step LASIK surgery 14

17.Seiler T, Quurke AW. Iatrogenic keratectasia after LASIK in a case of forme fruste keratoconus. J Cataract Refract Surg. 1998; 24(7): 1007–09.

18.Lafond G, Bazin R, Lajoie C. Bilateral severe keratoconus after laser in situ keratomileusis in a patient with forme fruste keratoconus. J Cataract Refract Surg. 2001; 27(7):1115–18.

19.Rao SN, Raviv T, Majmudar PA, Epstein RJ. Role of Orbscan II in screening keratoconus suspects before refractive corneal surgery. Ophthalmology. 2002; 109(9):1642–46.

20.Perry HD, Doshi SJ, Donnenfeld ED, Levinson DH, Cameron CD. Herpes simplex reactivation following laser in situ keratomileusis and subsequent corneal perforation. CLAO J. 2002; 28(2):69–71.

21.Stern C. New refractive surgery procedures in ophthalmology and the influence on Pilot’s fitness for flying. Eur J Med Res. 1999; 9; 4(9):382–84.

22.Hori-Komai Y, Toda I, Asano-Kato N, Tsubota K. Reasons for not performing refractive surgery. J Cataract Refract Surg. 2002; 28(5):795–97.