Vjacheslav kuznetsov inga borisikova acu mikrokirurgijas centrs eye microsurgery centre riga latvia
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Benefit of silicon-hydrogel contact lenses for patients undergoing combined surgical myopia correction - PowerPoint PPT Presentation

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Vjacheslav Kuznetsov , Inga Borisikova Acu Mikrokirurgijas Centrs (Eye Microsurgery Centre) Riga, Latvia. Benefit of silicon-hydrogel contact lenses for patients undergoing combined surgical myopia correction. Contact lenses.

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Vjacheslav kuznetsov inga borisikova acu mikrokirurgijas centrs eye microsurgery centre riga latvia l.jpg

Vjacheslav Kuznetsov, Inga Borisikova

Acu Mikrokirurgijas Centrs

(Eye Microsurgery Centre)

Riga, Latvia

Benefit of silicon-hydrogel contact lenses for patients undergoing combined surgical myopia correction

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Contact lenses

  • Patients are not always satisfied by the constant wear of contact lenses:

  • Hence the need for other options:

    • orthokeratology

    • surgery

  • Surgery helps patients who are unhappy with lenses.

  • Could lenses help those who are not satisfied after surgery?

Eye microsurgery centre www lazer lv l.jpg
Eye Microsurgery Centrewww.lazer.lv

  • a private ophthalmology clinic established in 1998

  • the main activities of the Centre:

    • refractive surgery

    • surgical, therapeutic and laser treatment (cataract, glaucoma, retinal distrophy, etc)

  • we are one of very rare European clinics that offer all kinds of vision correction

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Classification of vision correction

We classify vision correction kinds according to their impact on the eye tissues:

1. Glasses – non-contact

2. Lenses – contact, but without permanent effect

3. Microsurgery – mechanical modification

4. Laser – excimer (ectomy) or coagulation

5. Implants – implantation of foreign bodies

(corneal rings and intraocular lenses)

6. Radiofrequency – conductive keratoplasty

Various combinations are possible

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Myopia correction

  • Lenses - most frequent

    • Plus - cheap, easily available, non-traumatic

    • Minus - care necessary, foreign body

  • Excimer laser - most frequent surgery

    • Plus - technically simple, high precision

    • Minus - expensive, anatomical limitations, complications

  • Radial keratotomy - gradually loses popularity

    • Plus - least traumatic and anatomically most advantageous technique:optical centre remains intact

    • Minus - experience and high skill necessary

      Could combining the methods overcome their shortcomings?

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Observation 1

  • Our Centre has been performing radial keratotomies (RK) for 10 years, since 1998.

  • We saw that it is not always possible to achieve eumetropia, both for anatomical and technical reasons.

  • Additional keratotomy for better vision is possible after the cornea stabilizes.

  • But we found it easier to make adjustment, modifying the untouched central cornea by excimer laser, than to cut once more at the scarred peripheral cornea.

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Observation 2

  • We have been using excimer laser for 2 years.

  • We see that the effect of laser surgery depends on the corneal thickness and is additionally restricted by wide pupils and high astigmatism.

  • In case of thin cornea:

    • the achievement of good vision by excimer laser alone is doubtful

    • postoperative keratoconus becomes a problem

  • If the eye anatomy had been pretreated by radial keratotomy on the periphery, one needs to slice less of central cornea.

  • In this case the use of laser for thin corneas becomes possible and reasonable.

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  • Methods complement each other, changing the sphere at different sites:

    • radial keratotomy incisions are applied outside the optical zone,

    • excimer laser cuts off a peace of cornea in the optical zone.

  • Methods become technically simpler:

    • imperfect correction by RK may be later compensated by laser

    • laser manipulations on thin corneas become safe

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2006 – 2008

The idea applied

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Equipment used

  • Surgery

    • Allegretto Wave Eye-Q

    • Zyoptix XP microkeratome

    • Leica M841 microsurgical microscope

    • Microkeratomes for radial keratotomy both American and Russian styles

  • Diagnostics

    • ALLEGRO Topolyzer

    • ALLEGRO Analyzer

    • Pachymeters

      • Humphrey ultrasonic pachymeter

      • Qvantel Medical POCKET II pachymeter

      • Heidelbeg Engineering pachymeter

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Our method for combined correction

  • Patients

    • total: 31 patients

    • with thin corneas (about 500 m)

    • Initial myopia: -7D to -14D

      • too high to correct by single step RK

  • Two steps:

    • first - ”soft” RK

    • followed by excimer laser (LASIC or PRK-like) correction when the cornea is completely stabilized

    • interval between steps: 11 - 18 months

  • Results: eumetropia in all cases.

  • Not a single case of keratoconus was noted, even in risk patients.

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Contact lenses in between

  • Since fast patient rehabilitation is paramount in vision correction, we recommended our patients to wear contact lenses early, in 4-5 weeks after the first step.

  • 24 patients agreed to constant wear of silicon-hydrogel contact lenses,

    • at the beginning Bausch & Lamb Pure Vision lenses (base curve 8,6) were used,

    • later we switched to CIBA VISION Air Optix Night & Day (base curve 8,4;8,6).

  • These lenses were very well tolerated after surgery, had the advantage of constant wear.

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Observation 3

  • In addition in the 24 patients we observed permanent decrease of astigmatism (due to post-operative corneal plasticity?).

  • Average improvement was 0,75D.

  • The lower degree of astigmatism allowed to enlarge the excimer correction zone and thus ensure better nigh vision.

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  • We have a group of 81 patients available for comparison, who:

    • did not achieve eumetropia after RK

    • and wore soft-hydrogel lenses.

  • In addition, there is a group of 7 patients who refused lenses between the first and second steps of combined correction.

  • We haven’t found detectable permanent changes of astigmatism status in both groups.

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Probable mechanisms

  • Cornea after RK is not rigid and remains bendable by weak but constant pressure for about half a year.

  • Application of dense silicon-hydrogel contact lenses at the time of increased corneal plasticity produced an effect that is similar to orthokeratology, but permanent.

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The role of lenses

  • Difference between Bausch & Lamb and CIBA VISION for our patients is being evaluated.

  • Further molding of the cornea could be achieved by orthokeratology methods

    • that, in contrast to a normal eye, should produce permanent effect in this case.

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  • The use of dense contact lenses at the intermediate stage between the surgeries seems to be very promising.

  • Gentle unpretentious RK that doesn’t aim at perfect and complete correction could be used as the first step for shaping the corneal surface.

    • In that way, RK will be easily manageable by most ophthalmic surgeons.

  • Additional indications for excimer laser surgery could appear and better results for patients with difficult eye anatomy should be expected.