The Clamshell Dynamically Accommodating IOL

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The Clamshell Dynamically Accommodating IOL  

• Dr Keiki R. MehtaDr Cyres K. Mehta

Mehta International Eye Institute Bombay
India Purpose of the paper To demonstrate the
possibility of an Dynamically accommodative IOL
, which would have adequate range and be
impervious to capsular fibrosis
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Problems with existent accommodative IOL's

• Essentially static lenses when the the entire
  concept of accommodation is that of an active
  one.
• Present concept is based on a single plate IOL.
  Capsular collapse of the anterior on the
  posterior is inevitable with resultant freeze of
  function.
• None of the present crop of IOL really fill a
  bag, leaving it lax. For a relax- contract
  zonular concept to work, a partial bag which is
  loose and thus, by inference , lax, leads to poor
  zonulartug / relax functioning.

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The Clamshell IOL

• Consists of two separate parts , The anterior
  plate with a hole in the middle. This plate
  merely keep the bag inflated and permits the
  accommodative mechanism to function, The
  posterior plate with the dioptric carrier.
• The two pieces interlock with an open meshed
  hinge system which is very flexible .
• The foldable dual IOL has a central optic of 5.5
  mm and an overall diameter of 9.8 mm, made of a
  hydrophilic acrylic material with a UV-inhibitor
  .Refractive index of 1.46.
• Sub serves the basic requirements of filling the
  bag fully, thus unlikely to lead to any fibrosis
  in future and hence long term function assured..
• A true small incision IOL as injectible through a
  standard 2.8 mm incision.

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The posterior plate, with the dioptric carrier
The anterior perforated plate
Shows that even with lateral compression the
plates, once interlocked, do not separate
Plates interlocked to form one IOL
Schematic representation
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• The dioptric carrier moves forwards,
• through the central open plate thus getting the
  full range of accommodation

Surgical video
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First the dioptric carrier is prepared for
injection via a Rayner injector
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Implantation Steps
Step One Place the dioptric carrier on the
injector cartridge and insert into posterior
chamber
Step Two Place the open anterior stabilizer
ring and inject into the posterior chamber ,on
the top of the previous carrier
Step Three open up the folded anterior plate
and interlock with the posterior plate, thus
forming one , locked implant
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Results n 105 cases Follow up 28 months

• Mean values
• UCVA improved from 6/36 to 6/9 at
• distance and from J7 to J2 at near.
• BCVA 6/6 in 87 of cases, and J1 in 74  
•  Mean IOP ranged from 17.5 to 14.6mmHg
• The mean post-op accommodating index was
• 2.5D (1.0 to 3.5 dioptres)
• No complications were noted in this limited group

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Problems

• If the capsule opacities enough to require YAG
  capsulotomy  that may also disable the
  accommodating  mechanism.
•  What makes the surgery a little bit challenging
  is the  need for an immaculate phaco through a
  4.5 mm  capsullorhexis. A capsule tear may
  compromise the  perfect capsullorhexis and intact
  capsular bag and  further disable the
  accommodating mechanism.
•  

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In Summary

• The Clamshell Variable accommodative IOL appears
  to be safe and effective.
• Significant post-operative accommodation and
  reduction in refraction-corrective dependency.
•  After a mean follow-up of twenty eight months ,
  92 patients achieved vision sufficient for
  driving and reading a newspaper without spectacle
  correction. All of the patients are 20/30 or
  better and they are very happy because they do
  not use glasses.
• Tremendous refractive surgery tool for clear lens
  extraction, correcting not only high myopia and
  high hyperopia but also of retaining
  accommodation.