PREPARATION OF THE ALCOHOLIC SOLUTION
Alcoholic solution routine: BSS (8cc) + pure alcohol ( 98%) ( 2cc)
Reinforced alcoholic solution: Distilled water (8cc) + pure alcohol (98%) (2cc)
Aspirate 2 cc of alcohol from the bottle, then 8cc of BSS or of distilled water. In order to help the mixture, it is suggested to aspirate an air bubble and to shake the syringe for 30 seconds.
It is important that the mixture is prepared before any surgery session and that, afterwards, it is thrown away or, in case, changed every 3 hours.
I do strongly suggest to shake the mixture in the syringe with an air bubble and then to empty the needle before any laser treatment otherwise it would be possible to stratify the solution and consequently to distort the percentages.
It is also important to use an olive needle on the syringe in order to avoid any possible risk of damage on the epithelium.
N.B.: Do not use plastic syringes as they could react with the solution and release toxic monomers.In order to have the best result it is suggested to heat at 32°.
EPITHELIAL TREPHINATION
After positioning the speculum, the trephination is performed with a special micro-trephine with an 80 um depth calibrated blade for the 8mm optic zone, and a 90 um depth calibrated blade for the 9mm zone.
The trephine is held with the right hand and it creates a hinge (the epithelium is not cut) at the 12-o’clock position. Theoretically, the width of the hinge should be 90°, but, as a small rotation of the blade (about 5° on the right and 5° on the left) is made in order to facilitate the incision, the hinge will be of about 80°.
A relative strong pressure has to be made followed by rotatory movements.
It is important that the trephination is efficient so that the solution can slide easier under the epithelium.
The use of a serrated blade trephine creates small epithelial holes, which facilitate the slide of the alcoholic solution under the epithelium.
I have never experienced any lesion on the Bowman membrane close to the incision. The trephine can be used for about 100 trephination.
The centring of the trephination will be obviously performed on the pupil.
PROBLEMS AND SOLUTIONS STAGE 2
1 The patient moves during the placing of the trephine with a consequent epithelium lesion
- The trephine must be repositioned and the lesion ignored; an easier detachment will be noticed as the solution slide through the iatrogenic lesion. Particular attention should be taken during the dragging of the epithelium in order to avoid enlarging the hole.
2 The trephination does not hit perfectly the centre of the pupil
- Carry on ignoring it, after the alcoholization, the edge of the epithelium will be widen with the microhoe in order to guarantee the right dimension of exposure of the stroma that will be treated compared to the pupil.
3 The trephination is too superficial
- Try, as much as possible, to reposition the trephine and perform a new trephination; this will probably create a double way. In any case, the next steps will not be compromised.
4 Wrong choice regarding the trephine’s diameter
- If a larger diameter trephine is wrongly used, it will be enough to use the corresponding cone. If, on the contrary, a smaller trephination is made, follow the indications given at point 2, that is to widen the edge of the incision for all its length.
APPOSITION OF THE CONE
The cone has to be slightly wider than the trephine that we used. Precisely, for the 8mm trephine, the 8.5mm cone while for the 9mm trephine the 9.5mm cone must be used. It is important this slight superior diameter as it will allow the penetration of alcoholic solution inside the pre-cut. For this, it is important to give particular attention to the centring which needs to be concentric at the pre-cut.
The cone has got a double hinge which, not only guarantees the control of the solution but also maintains the eyeball firm.
However, it is suggested to exert pressure in order to avoid alcohol leakage.
It is not advised to use a normal Keratotomy marker, as it does not avoid the accidental movements of the eye and consequently the contaminatin of the conjunctiva through the alcoholic solution.
INSTILLATION OF THE SOLUTION
With one hand, keep strongly the cone and proceed with the instillation of some drops of alcoholic solution.
The alcoholic solution to be used initially is BSS+ alcohol (heated at 32°).
It is necessary to fill the cone up to the edge.
The time has to be counted only after that all the epithelium is covered.
The standard initial time is 20’.
If necessary, re-position the strengthened solution (Alcohol + distilled water) for further 5 or 10 seconds after detaching the edge of the epithelium with the ” spatula”. After the 20’ seconds, you need to aspirate the inside of the cone with a sponge trying carefully to drain the solution in the best possible way. The appearance of a light epithelial edema after a few seconds is the first sign that the epithelium flap is detached and it is shown through a light lost of transparency.
Once that the cone is removed, the assistance has to thoroughly wash with Voltaren Ofta. It is strongly recommended to avoid any contact between alcoholic solution residuals and the conjunctiva, as they are very irritating.
PROBLEMS AND SOLUTION STAGE 4
1 Some drops goes on the conjunctiva during the installation of the solution
- Wash intensively and, at the same time, carry on the calculation of the time.
2 There is a leakage of the alcoholic solution for various reasons such as a movement of the patient
- Try to hit the centre again and wash the conjunctiva. In the case that there is a remarkable leak, you should instil new alcoholic solution
3 As washing, there is a epithelium breaking due to the excessive fluid pressure
- Ignore the problem and be careful during the next stages regarding the flap.
EPITELIOTOMY WITH EPITHELIAL DETACHING SPATULA
Gently dry the edge of the trephination in order to highlight it.
It is suggested to use a sponge during this stage, being particularly careful to avoid any loss of hair. Also avoid drying the centre of the flap as it stays more vital if moist.
From the 6 o’clock position, start the detachment of the edge with small movement. The detachment can be made either clockwise or anticlockwise. Carrying on the procedure towards right, it is suggested to tilt the microhoe on the right side in order to avoid covering the pre-cut. The same procedure has to be followed on the left side.
This stage ends when the only part intact of the epithelium is the part of the hinge at 12 o’clock.
PROBLEMS AND SOLUTION STAGE 5
1 The margin is not sufficiently highlighted due to a superficial pre-cut.
- Look for a gap between the transparent and opaque epithelium and then carry on.
2 It is impossible to detach the epithelium
- Create some small breaking using the angles of the microhoe, which have been especially designed in orders to scrape the epithelium. Afterwards, instil again the strengthened alcoholic solution for 5 or 10 seconds.
DRAGGING WITH EPITHELIUM SPATULA
After highlighthing the edge of the epithelium, roll it back keeping the spatula inclines on the flap trying to avoid touching the stromal surface that needs to be treated.
With the experience it will be easy to feel when the resistance to the traction is too much and consequently it is more convenient to move to another zone.
Gently roll the flap back to the hinge.
The superior part is normally more adherent and consequently, carry on with the spatula in a vertical position, pressing on the stroma with small movements. In this way the detachment will be completed.
As an alternative, it is possible to use a bow-dissector. Slip it under the epithelium at 6 o’clock position while applaning the cornea.
During this stage, with a Mendez no traumatic ring, keep the eye steady. The dissector wire has to compress the cornea as a stromal microkeratom. If there are excessive adhesions, it is suggested to use the spatula with small vertical movements.
PROBLEMS AND SOLUTION STAGE 6
1 The flap puts up resistance to the traction
- It is possible to instil again the alcoholic solution for a total of 50 seconds and then proceed.
2 The flap does not detach in spite of the repeated instillation of the alcoholic solution
- This happens particularly in adults who were old wearers of contact lenses. In these cases, since the beginning the spatula has to be used in a vertical position and it is important to be careful not to damage the hinge. Obviously, in these cases, the scarping is similar to a mechanics desepitelization pre-PRK. Certainly, during the first days, the flap will not have opltical propierties but it will guarantee a complete re-epithelialization in 3 days time thanks to a mechanism called ” feeder layer” that is a dead cells layer which allow to the limbus cells to regrow over the surface in a short time.
7th fase
THE FLAP IS GATHERED AT 12°’CLOCK POSITION
It is suggested to gather the flap in order to keep it moist during the Laser treatment. To make this procedure easier, use a blunt spatula ( better if with another one)
PROBLEMS AND SOLUTION STAGE 7
- The hinge has been broken and we have a free cap
- fold very carefully keeping in mind that it needs to be repositioned and be careful to the free cap during the Laser treatment.
8th stage
LASER TREATMENT
Treatment proceeds as for traditional PRK except regarding the increase corrective effect (about 10% more compared to a PRK). Consequently, I do suggest to reduce the value of the myopia that has to be corrected by about 10% until 10dt and progressively by 20% until –10dt to –20dt.
It is possible to use the following formula in order to calculate it : Laser = myopia x (0,9 + ( myopia / 200 ) )
For example : Refraction – 5 dt > Laser Setting = – 5 X ( 0,9 + ( 5 / 200 ) ) = – 4,375
For example : Refraction – 10 dt > Laser Setting = -10 X ( 0,9 + ( 10 / 200 ) ) = -8,5
For example : Refraction – 20 dt > Laser Setting = -20 X ( 0,9 + ( 20 / 200 ) ) = -16
The cause for this over-correction is maybe the reduction of the regression present in the PRK of which the Laser protocol takes into account.
If you perform a smoothing, protect in advance the flap with a fluid
REPOSITIONING OF THE FLAP ON THE TREATED AREA
If you performed a smoothing, it is suggested to dry gently the area. Otherwise, instil a drop of BSS in order to help the flap to slide into its natural position.
Use a blunt spatula and place it at the 12 o’clock position under the flap, in touch with the epithelium surface.
Gently reposition all the epithelium so that all the pre-cut is covered. Due to its elasticity, the flap will be bigger and this will allow to cover all the small irregularities of the edge.
PROBLEMS AND SOLUTION STAGE 9
- The hinge is completely detached
- It is necessary to use two micro spatulas simultaneously. Place the first spatula on the edge of the flap, towards the limbus in order to keep it steady. The second spatula will collect the peripheral part towards the periphery and it will roll dawn it on the stromal bed. After spreading it, it is suggested to wait a light desiccation which improve the adhesion.
2 The epithelium is completely pulpy. It can happen during the retreatment post KR or post Haze.
- Collect the debris and position it at the centre of the cornea. It is suggested to use a narrow soft protection lens. Even if these conditions do not allow to have a fast corrected visual acuity and do not reduce the post-operative pain, there will be a re-epithelialization in 3-4 days time (feeder effect) and consequently a considerable delay will be avoided with all the problems that we know.
3 Impurity under the epithelium
- If there are some small hairs, try to turn the epithelium upside down and wash it even if it will be very difficult to remove them. The clinical impression is that, in any case, the impurity will be ejected during the coming months.
APPOSITION OF A SOFT CONTACT LENS
I do suggest to use lenses with high hydrophily (60-70°) with basal ray slightly narrow (8,4).
Place the lens at 12 o’ clock position and let it fall in the centre of the cornea
PROBLEMS AND SOLUTIONS STAGE 10
- After positioning the lens, there are some small folds on the flap
- It is enough to massage the lens with a spatula and to reposition correctly.
POST-OPERATIVE MEDICATION AND CHECK UP
The first medication is made with topic antihistaminic, antibiotic, mydriatic and steroids . Remove the speculum like in a Lasik procedure and ask the patient to keep the eye close for a minute. Do not bandage the eye and, since the first day, prescribe antibiotics and non steroid anti-inflammatory. The light steroid therapy + artificial tears starts from the 4th day after the removal of the contact lens.
In the case of a not perfect integral flap, in the old wearers of contact lenses and in the myopia superior to 8dt, I introduced, as a standard, the use of auto-serum, prepared from 10cc of autologus blood centrifuged. Instil it 4 times a day during the first days and keep it in the fridge. It is suggested to use a stiff shell as a protection during the first 4 nights. The first check up has to be made the day after the surgery in order to check the presence of the lens and the flap. The second after 3-4 days in order to remove the lens.
The removal of the lens allows to notice some parts or irregularity epithelial with a fluorescein colouring. If there are not desepithelitationed parts , leave the patient without contact lens. After removing the lens, it is absolutely normal that the patient has got some annoyances for about a hour. There will be no problems or pain if the flap is treated correctly, without trauma of the Bowman membrane and without contamination of the conjunctiva with the alcoholic solution. In any case, the pain and its duration are remarkably less than in a traditional PRK Laser treatment.
Obviously the visual recovery will be faster if the flap results optically good since the beginning.
A week after the removal of the lens, it is expected to have a visual recovery of about 80-90% of the visual acuity, but it is also possible to see such recover also during the first days.
Lasek gives the possibility to correct any kind of refractive defect without the limitation given by PRK. Also for high level of myopia (-16dt) I have never experienced haze higher than 1° in all the cases treated until today.
It can happen , in same cases a hyperopic shift (from 1 to 3dt) for a few weeks due to a not completed growth of the epithelial layers in the central portion of the epithelium.
PROBLEMS AND SOLUTIONS STAGE 11
1 The loss of the lens and flap during the first day
- Put the lens again and follow the patient as for a normal PRK until the re-epithelialization is completed
2 Partial breaking of the flap
- if the detached part is well noticeable, it is suggested to remove with a micro scissors and then place again the lens
3 In the 10th day, it could appear some small islands of whitish epithelium as a sign of fast death
- Increase the dosage of steroid in order to reduce the inflammatory reaction. It is also suggested to use a big quantity of artificial tears with ringer
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