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Moria Epi-K™ for Epi-LASIK

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While LASIK remains the procedure of choice for most refractive surgeons in the treatment of mild to moderate myopia, new types of surface ablations are gaining popularity as an option for a cross-section of patients who are unsuitable candidates for such procedures. At a EuroTimes Educational Satellite Symposium held at the XXIII Congress of the ESCRS Lisbon, speakers explored the potential advantages of the new surface ablation procedure Epi- LASIK performed with the Moria Epi-KTM epithelial separator.

Alaa El-Danasoury, FRCS Medical Director Chief, Refractive Surgery Service Magrabi Hospitals & Centers malaa@magrabi.com.sa

Jorge L. Alio MD PhD Professor and Chairman of Ophthalmology VISSUM, Instituto Oftalmologico de Alicante Universidad Miguel Hernandez, Alicante, Spain jlalio@vissum.com

Dr Alaa El-Danasoury told the symposium that LASIK is likely to remain the preferred option for patients who are suitable for such procedures because it involves less pain provides more rapid visual recovery and entails no risk of haze. However, there are patients with low to moderate refractive errors who are unsuitable for LASIK but who may nonetheless be suitable for surface procedures. They include patients with relatively thin corneas and those who are extremely cautious about ocular surgery involving separators.

New surface ablation techniques
A number of new variations on conventional PRK have been developed over recent years to address the needs of such patients.They include LASEK, the application of mitomycin-C and, more recently, Epi-LASIK. Each of the techniques aims to reduce postoperative pain, speed visual recovery and above all, eliminate haze.There remains some controversy, however, regarding both their superiority in terms of safety and efficacy compared with conventional PRK.

In the case of LASEK, there have been conflicting reports regarding reduced pain and haze with the procedure.The LASEK technique involves loosening and lifting the epithelium with alcohol and replacing it after the ablation.The theory is that the epithelium will remain viable and therefore not stimulate a healing response in the keratocytes in the underlying stroma. However, it has been demonstrated that the alcohol used in the procedure actually kills the epithelial cells. It is therefore debatable whether the epithelial flap actually confers any benefits.

Mitomycin-C is used in surface ablation procedures as a means of preventing haze by dampening down the keratocyte response to the ablation. But the agent is extremely toxic, and its longterm effects on the keratocytes and the corneal collagen remains unknown.

“This is an area of controversy, it is unknown when the cornea will recover its normal immune physiology and there are no longterm studies on the effect of mitomycin on the cornea. I am reluctant to kill the stromal keratocytes because these patients have to live the rest of their lives with a good corneal immunity.”

Epi-LASIK flaps more viable

The newest of the techniques Epi-LASIK is free of the many of the drawbacks of the older surface ablation techniques. The procedure involves the mechanical separation of the epithelium from the stroma with a specially designed device. It therefore involves no toxic substances. Moreover, the technique separates the epithelial sheet below the lamina densa. Research has shown that the epithelial tissues in the separated flap remain viable in 85% of cases (Pallikaris et al, JCRS, August, 2003).

Dr El-Danasoury noted that a surface ablation procedure that does not cause haze would be of particular value in the treatment of patients who are more prone to haze, such as brown-eyed Middle-Eastern individuals.

“In the Middle East we do not perform many PRKs because of the higher risk of haze.We’ve seen haze for very low myopia, as low as two or three dioptres. But there are many patients who are not good candidates for LASIK and surface ablations would be a good choice for them if we could do it without inducing haze.”

The Moria Epi-K epithelial separator
Surgeons now have at their disposal a new system that fully automates the creation of epithelial flaps in the form of the Moria Epi-KTM.The new device consists of a special lightweight handpiece and a disposable head.

The Epi-K’s handpiece has two motors, one for head advancement and the other for oscillation of the separator.The advancement speed is specifically calibrated for epithelial separation.
The disposable head encases a pre-assembled non-cutting separator.The angle of the separator to the epithelium allows for cleavage of the epithelial layer while an applanation front plate prevents the instrument from cutting into the stroma.

“The Epi-K really does what it says, we have used the device in 60-65 patients and we have not really had any problems so I am confident that the machine is very precise.”

Epi-LASIK in haze-prone eyes
He added that in a comparative study he recently carried out involving haze prone eyes, PRKtreated eyes had significantly more haze than eyes that underwent Epi-LASIK with Moria Epi-K. In fact, the Epi- LASIK-treated eyes were virtually haze-free in all cases.

The prospective bilateral randomised clinical trial study involved 26 eyes of 22 Middle- Eastern brown-eyed patients who underwent Epi-LASIK with the Epi-K device.A subgroup of 15 consecutive patients underwent Epi-LASIK in one eye and PRK in the other.

The patients in the study had a mean age of 22.3 years (range: 9-33 yrs). All were unsuitable for LASIK because of thin corneas. Their mean preoperative spherical equivalent was-2.90 D (range: -4.75D to -1.13 D). Patients were excluded from the treatment if they were keratoconus suspects, had dry eyes, unstable refraction, or had undergone previous ocular surgery.

Epi-LASIK technique
Dr El-Danasoury commences his Epi-LASIK procedures by first applying topical anaesthesia.After putting on the suction ring he then assembled the device on the eye and used the slow speed of the Epi-K device to move it forward across the eye.

“The eye should be continually moistened throughout the procedure to avoid tearing the epithelial tissues. Once you reach the hinge site you reverse the motor and it goes backwards. It is really simple and easy to use,” Dr El-Danasoury noted.

When he has created the flap he uses balanced salt solution to move it out of the way during the ablation. Following the ablation he manipulates the flap back into place with a salinesoaked sponge. He then applies hypertonic saline to make the epithelial flap more adherent. He then applies antibiotic drops and places a bandage contact lens on the eye.

Operative complications in his study included a total flap cut in one eye, which subsequently underwent conventional PRK and was excluded from the study results. In another eye a stromal injury occurred when the epithelial separator hit a metallic instrument.Although the eye had a good visual outcome, Dr El- Danasoury said he now preassembles the Epi-K instrument before applying it on the eye to avoid such complications.

Similar efficacy and predictability
The uncorrected visual acuity results at two months were very similar in the two treatment groups. In the Epi-LASIK group, 73% achieved 20/20 or better, 93% achieved 20/25 or better, and 91% achieved 20/30 or better. In the PRK group, 71% achieved 20/20 or better, 86% achieved 20/25 or better, and 93% achieved 20/30 or better. All eyes were 20/40 or better at three months.

The Epi-LASIK treated eyes appeared to fare slightly better than the PRK-treated eyes in terms of BCVA, although the difference did not reach statistical significance. Half of the eyes in the Epi-LASIK group gained one or two lines, compared to 43% in the PRK group, while 5.0% of the Epi- LASIK group and 7.0% in the PRK group lost one line of BCVA. No eyes in either group lost two or more lines of BCVA. Visual rehabilitation appeared to be more rapid in the Epi- LASIK treated eyes. At the fourth postoperative day, 50% said they saw better in their Epi-LASIK eye, while only 16.7% said they could see better in their PRK eye.

In addition, 18% had achieved their final refraction by day four in the Epi-LASIK group, compared to only 7% of eyes in the PRK group. By day seven 27% had achieved their final refraction in the Epi-LASIK group, compared to only 14% in the PRK group. However by two months all eyes in both groups had achieved their final refraction.

The two groups had similar results in terms of postoperative pain. On the first postoperative day, four patients (28.6%) reported less pain in the Epi- LASIK treated eye and six (42%) reported less pain in the PRKtreated eye and the remaining patients reported no difference between their two eyes. By the second day six (54.5%) reported less pain in their Epi-K eye and two (18.2%) reported less pain in PRK eye. By the fourth day all patients said they were virtually pain-free in both eyes.

“There was not much difference between the two groups in the pain they experienced.The first couple of days patients reported pain in both eyes but by the fourth day they were almost free of pain.”

Significantly less haze

Dr El-Danasoury noted that the most important difference between the two groups was in the occurrence of subepithelial haze. At three months postoperative, in the Epi-LASIK eyes there was a trace of haze in 29% and the remaining eyes remained totally clear at three months. By comparison, in the PRK-treated eyes 29% had a trace of haze, 21 % had level one haze, seven percent had level 2 and a further 7% had level 3 haze.
In summary, Dr El-Danasoury said that the Epi-K epithelial separator is effective in creating epithelial flaps and that there is less risk of haze with Epi-LASIK compared with PRK.The technique also has efficacy and predictability similar to PRK but has a relatively faster, less painful visual recovery. “I think now we have a good alternative for many patients who are not good candidates for LASIK and do it without the need to place toxic substances on the cornea and if we can do it without haze then this represents a step forward.”

Epi-LASIK and corneal biomechanics

While LASIK does not entail the risk of haze, it may be less predictable than surface ablation procedures because of the effects of flap creation on corneal biomechanics, Prof. Jorge L.Alio MD PhD told the symposium. The degree to which flap creation alters the biomechanics
of the cornea depends on a range of factors.They include the size, thickness and regularity of the flap, the size, flap centration and position of the hinge, and the curvature of the interface. Postoperative factors also come into play including corneal wound healing and interface reactions. The result of all these factors is that the postoperative radius of corneal curvature will be at variance from what was intended. As a consequence eyes can be over- or under-corrected and customised ablations will lose some of their precision.

Comparative studies shows least change in corneal biomechanics with Epi-LASIK
Dr Alio told the symposium that in a comparative study he conducted involving 81 eyes of 81 patients, in those treated with Epi- LASIK there was only a negligible difference between the intended postoperative radius of curvature and that which was intended, while there were significant differences between the intended and achieved corneal curvatures in eyes treated with LASIK or LASEK.

The patients in the study had myopia or myopic astigmatism and a preoperative spherical equivalent ranging from–2.0 D and –8.0 D. They ranged in age between 22 and 57 years. Dr Alio randomised his patients into three treatment groups. In the first group, 40 patients underwent LASIK with flaps created with a Moria M2 microkeratome. In the second group, 21 patients underwent LASEK, and in the third group 20 patients underwent Epi-LASIK with the Moria Epi-K epithelial separator. In all eyes, Dr Alio performed the ablations with the Esiris excimer laser (Schwind) using the same standard algorithm.

Coefficient of biomechanical response
At one months’ follow-up Dr Alio used topography to determine the effect of corneal biomechanics on the resulting corneal curvature. He obtained a coefficient of the biomechanical response by dividing the difference between the post surgical corneal radius of curvature and the calculated sculpted curvature radius by the calculated sculpted radius of curvature.

“The coefficient characterises the change in corneal curvature due to such factors as flap relocation and the ablation profile by excimer laser. Therefore, if it is greater than zero it means the cornea has been excessively flattened, that, for myopic correction, is overcorrected. If on the other hand, the value is less than zero it means the cornea remains steeper than planned, or undercorrected,” Dr Alio explained.

The results showed that in the Epi-LASIK group the coefficient of variation between the precalculated sculpted radius and the postoperative radius was minimal (mean:0.09%). By comparison, the coefficient of the biomechanical response was –5.3% in the LASIK group and –2.3% in the LASEK group, indicating significant undercorrection. Correspondingly, the predictability of the procedure was higher in the Epi-LASIK group (0.97) than in the LASIK group (0.84) or the LASEK group (0.71).The superior predictability of the results in terms of topography was also reflected in the patients’ refractive outcomes he noted.

Different results with different surface ablation techniques

Dr Alio noted that the better predictability of Epi-LASIK compared with LASEK came as somewhat of a surprise. “We had thought that Epi- LASIK and LASEK were equivalent procedures in terms of the effect they have on biomechanical changes of the cornea, but our results indicate that they are not. It may be that the epithelial toxicity in LASEK plays a role that is not present in Epi-LASIK or that the smoother surface to be ablated preserves the corneal biomechanics.”

In conclusion, Dr Alio said that Epi-LASIK caused the least biomechanical change of the three techniques in the study. He suggested furthermore that an increase in the quality of excimer laser outcomes might be expected with Moria Epi-K epithelial separator.

“It is in the periphery of the ablation that most of the biomechanical changes of the cornea following corneal refractive procedures occur and the more we are able to control those changes, the more the quality of vision results will improve in our patients,” he added.