144 THE FUTURE: WILL LASEK SUPERSEDE LASIK?

Short-term postoperative risk/complications

•There is a risk of infection postoperatively as the epithelium regenerates. This is minimised with the use of a topical antibiotic prophylactically.

•Abrasion or poor epithelial adhesion in some patients may result in slower recovery and increased discomfort postoperatively.

•In the case of flap loss or if a viable flap cannot be created during treatment, the patient feel moderate-to-severe pain postoperatively which may be controlled with oral and topical analgesics.

•Most patients experience a mild degree of haze postoperatively which may cause a reduction of vision and haloes around lights. Significant haze is managed with the use of topical anti-inflammatory or anti-metabolite agents where necessary (see box on Mitomycin C).

•There is a risk of dry eye postoperatively.

Mitomycin C

Haze formation after surface treatments has been the focus of many studies and the use of the powerful antimetabolite Mitomycin C immediately after ablation is known to inhibit this response.6,7 Mitomycin C is a cytotoxic agent which inhibits DNA synthesis and is effective at preventing cell division. This reduces the healing response and the formation of scar tissue. The protocols for using this controversial agent in refractive surgery vary between surgeons. Most surgeons will only use Mitomycin C prophylactically on high myopic treatments or to treat existing haze. When used, it is usually used in a concentration of 0.02% or 0.03% for 15–45 seconds, then copiously irrigated off. The use of this DNA inhibiting agent is controversial as the long-term effects on the cornea are not fully known.

Long-term complications

•There is a risk of under or overcorrection by the laser. This may mean a difference in the prescription and acuity between the eyes.

•Persistent haze can cause scarring and the loss of up to 2 lines of best corrected acuity is possible (BVCA). However haze of greater than grade 1 is unusual3,5 and grade 1 or less is unlikely to affect BCVA.

•A persistent epithelial defect may occur and can cause pain and watering of the eye as well as increasing the risk of infection. If this persists, a reduction or aberrations in the vision may occur.

•Regression of the laser treatment can occur with time and the patient may require further treatment.

Other side effects

Due to the changed shape of the cornea it may be more difficult to wear contact lenses postoperatively.

Typical postoperative symptoms 145

TYPICAL POSTOPERATIVE SYMPTOMS

Although the procedure itself is painless due to the anaesthesia, the patient will feel some discomfort when the anaesthetic wears off. Some patients may experience severe discomfort while the epithelium heals; if there is significant pain, analgesics can be used. The discomfort will be significantly better after 48 hours. A protective pad or shield may be placed over the eye for the first 24 hours.

By day 3 or 4 the patient will feel comfortable and the vision will feel less blurred. Patients are advised not to drive until after they have had their vision checked and it has been confirmed to be adequate.

Postoperative care

This will vary from surgeon to surgeon, but the first aftercare is usually carried out within the first 4 days after treatment. Some surgeons prefer to see the patient daily until the contact lens is removed. This is usually done on day 4 and, depending upon the status of the epithelium, the surgeon may choose to insert a new bandage lens if necessary. The visual acuity is checked, but the patient is not expected to achieve the target unaided acuity until 1 week after treatment. The cornea will be checked for any early signs of haze. It is common practice for surgeons to prescribe topical anti-inflammatory agents prophylactically for shortterm use to minimise the risk of haze formation.

The patient is then checked after one week when a reliable refraction is more likely to be obtained. By this stage, the cornea should be completely re-epithelialised with no sign of an epithelial defect.8,9 The practitioner should also look for soft lens related infiltrates (Figure 10.1) as the bandage lens is worn continuously for up to 4 days postoperatively. There may also be a build up of

Figure 10.1 Soft contact lens related infiltrate

146 THE FUTURE: WILL LASEK SUPERSEDE LASIK?

Figure 10.2 Punctate staining is seen after a toxicity reaction

Figure 10.3 Corneal haze may be seen after LASEK or PRK

preservative in the lens if multidose topical agents have been used which could cause a toxicity reaction (Figure 10.2).

At 1 month, the vision and refractive error are generally stable. Mild haze may be seen, though it is rarely greater than grade 1.3,5 If PRK was performed due to the loss of the epithelial flap, then the risk of haze is greater and is usually maximal at 1–3 months’ postoperatively.10 If significant haze is seen (Figure 10.3), referral to the surgeon is required as treatment may be required.

By 6 months, the eye there should be no significant haze and the vision should be stable. A further check at 12 months is advisable to ensure that the patient has

Discussion 147

achieved a stable refraction and that risk of late onset haze has passed. This has not been documented with LASEK yet but is a known risk of PRK.9 The patient can be discharged if the refraction is stable and the patient is happy.

DISCUSSION

LASEK appears to have few risks and the procedure is less invasive than LASIK; however, it is not the first choice procedure for most surgeons. The reasons for this are multifactorial.

Patient recommendation

It is a relatively new procedure and does not yet have the same reputation as LASIK among patients, so is in less demand. The recovery period when compared to LASIK is slower and so does not create the same ‘wow’ factor which motivates personal recommendation from treated patient to prospective patient.

FDA approval

In the US, the Food and Drug Administration (FDA) approves drugs and devices for medical procedures, but not the actual procedures themselves. Currently, the use of the excimer laser for LASEK is not FDA-approved. However, those lasers that have earned approval based on PRK or LASIK data can be used in LASEK procedures. The use of approved devices in such an instance is called an ‘off-label’ use. As the approved lasers have proven safe and effective in other procedures, ophthalmologists may use them off-label if they feel it is in their patients’ best interest to do so. As the use of excimer lasers in LASEK is not FDA approved, advertising of the procedure is restricted. This may have an impact on the confidence and awareness of the procedure among patients.

Haze and discomfort

Advocates of LASEK claim that postoperative discomfort and haze formation is less than with PRK and that visual recovery is better. Despite studies showing excellent visual results,3,5 there is a belief among some surgeons that LASEK is a re-packaged PRK and that the decrease in haze and regression is more due to improved lasers and drug regimens than the technique itself.10,11 Haze formation may also be linked to the surgeon’s technique for creating the epithelial flap as it is not straightforward and there is a learning curve.7 The benefits of the epithelial flap still need to be validated as there are studies which do not show any significant difference between PRK and LASEK.8,9

Future developments

Flap creation in LASIK has been shown in some studies to increase higher order aberrations.15,16 Wavefront-guided ablations that are based upon the untreated

148 THE FUTURE: WILL LASEK SUPERSEDE LASIK?

eye result in the correction of aberrations that were detected prior to the flap being cut only. This limits the benefits of wavefront technology. The use of wave- front-guided treatment with surface ablation may remove this limitation as the cornea re-epithelialises after LASEK/PRK and flap-related aberrations are not induced. This theory needs more research as one study found no significant difference in the visual performance of eyes that had undergone PRK when compared to LASIK.17

CONCLUSION

The creation of the LASEK flap can be done in several ways with variations in the shape of the flap, the type and strength of alcohol used, the duration of alcohol exposure and the way the flap is lifted. Until the procedure is standardised, it may be difficult to get consistent findings for this procedure. The postoperative recovery period may be reduced in LASEK if a less traumatic method of creating the epithelial flap was developed. However, the convenience that LASIK offers in terms of rapid visual recovery and minimal pain is hard to beat, and until LASEK can do that it will not seriously threaten the popularity of LASIK.

References

1.Hoffer K. Reflections on the origins of LASEK, 1990. Rev Ophthalmol 2003;11:10/05.

2.Camellin M. Laser epithelial keratomileusis for myopia. J Refract Surg 2003;19:666–670.

3.Bilgihan K, Hondur A, Hasanreisoglu B. Laser subepithelial keratomileusis for myopia of 6 to 10 diopters with astigmatism with the MEL60 laser. J Refract Surg 2004;20:121–126.

4.Chen CC, Chang JH, Lee JB et al. Human corneal epithelial cell viability and morphology after dilute alcohol exposure. Invest Ophthalmol Vis Sci 2002;43:2593–2602.

5.Gabler B, Winkler von Mohrenfels C, Herrmann et al. Laser epithelial keratomileusis (LASEK) for treatment of myopia up to 6.0 D. Results from 108 eyes after 12 months. Ophthalmologe 2004;101:146–152.

6.Carones F, Vigo L, Scandola E et al. Evaluation of the prophylactic use of mitomycin-C to inhibit haze formation after photorefractive keratectomy. J Cataract Refract Surg 2002;28:2088–2095.

7.Xu H, Liu S, Xia X, Huang P et al. Mitomycin C reduces haze formation in rabbits after excimer laser photorefractive keratectomy. J Refract Surg 2001;17:342–349.

8.Litwak S, Zadok D, Garcia-de Quevedo V et al. Laser-assisted subepithelial keratectomy versus photorefractive keratectomy for the correction of myopia. A prospective comparative study. J Cataract Refract Surg 2002;28:1330–1333.

9.Pirouzian A, Thornton JA, Ngo S. A randomized prospective clinical trial comparing laser subepithelial keratomileusis and photorefractive keratectomy. Ophthalmology 2004;122:11–16.

10.Lohmann CP, Gartry DS, Muir MK, Timberlake GT, Fitzke FW, Marshall J. Corneal haze after excimer laser refractive surgery: objective measurements and functional implications. Eur J Ophthalmol 1991;1:173–180.

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Index

Note: page numbers in italic type refer to tables and in bold type to figures.

152 Index

Index 153

154 Index