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

1
Benefit of silicon-hydrogel contact lenses for
patients undergoing combined surgical myopia
correction

• Vjacheslav Kuznetsov, Inga Borisikova
• Acu Mikrokirurgijas Centrs
• (Eye Microsurgery Centre)
• Riga, Latvia

2
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?

3
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

4
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

5
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?

6
Rationale for combined surgery
7
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.

8
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.

9
Benefits

• 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

10
The idea applied

• 2006 2008

11
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

12
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.

13
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 8,48,6).
• These lenses were very well tolerated after
  surgery, had the advantage of constant wear.

14
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.

15
Controls

• 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 havent found detectable permanent changes of
  astigmatism status in both groups.

16
Conclusions

• (preliminary!!)

17
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.

18
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.

19
Benefits

• The use of dense contact lenses at the
  intermediate stage between the surgeries seems to
  be very promising.
• Gentle unpretentious RK that doesnt 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.

20
Thank you for attention!