Minimizing Risk in Visian ICL Implantation.

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Minimizing Risk in Visian ICL Implantation.

• NO FINANCIAL DISCLOSURE
• Dr. MATHEW KURIAN
• Dr. ROHIT SHETT Y, Dr. HEMAMALINI M. S., Dr.
  SHETT Y BHUJANG K.
• CATARACT REFRACTIVE LENS SURGERY SERVICES
• NARAYANA NETHRALAYA, BANGALORE

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Implantable Collamer Lens

• The ICL(Staar Surgical AG) is FDA approved for
  myopia
• It is a plate haptic lens implanted in the sulcus
  with an aqueous layer separating it from the
  lens.
• This requires accurate intraocular sizing
  calculations.
• Horizontal white to white diameter (Orbscan II)
  estimates sulcus (Recommended method)
• However, estimating sulcus size through white to
  white measurements could lead to improper sizing1
  that would only be detected in the postoperative
  period.
• Recent literature UBM is more reliable2.

1. Werner L, et.al,Correlation between different
measurements within the eye relative to phakic
intraocular lens implantation JCRS 3019828 2.
Choi KH, et.al, Ultrasound biomicroscopy for
determining visian implantable contact lens
length in phakic IOL implantation. JRS. 362-7.
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AIMS AND OBJECTIVES

• To study the sizing of the Visian implantable
  Collamer lens (ICL)
• by white to white measurement using the Orbscan
  II and
• sulcus diameter using ultrasound biomicroscopy
  (UBM)
• To correlate the results to the postoperative
  vaulting assessed by
• Slit lamp evaluation
• UBM measurement from the anterior capsule to the
  posterior ICL surface.

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MATERIALS AND METHODS

• Prospective study with IERB clearance informed
  consent
• All cases which underwent Implantable Collamer
  Lens (ICL) implantations for the correction of
  myopia from Jan to Dec 2007
• Standard inclusion and exclusion criteria for ICL
  implantation
• Surgeries performed by a single surgeon.
• Standardized UBM scans (single examiner)

• ICL POWER CALCULATION
• Refraction (manifest/cycloplegic)
• Keratometry
• Desired target post-operative refraction
• Corneal thickness

• ICL SIZING
• Horizontal white to white (Orbscan)
• Horizontal sulcus diameter (UBM).
• ACD

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SULCUS ESTIMATION
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POST-OPERATIVE FOLLOW UP

• Reviewed on day 1 7, 6 weeks
• Thorough ocular examination
• Correction of residual refractive error
• ASSESSMENT OF VAULT
• Central distance between anterior surface of the
  crystalline lens and posterior surface of the
  ICL
• Ideal sized ICL will provide a vault of 0.250 to
  0.750 mm ( ½ CT to 1 ½ CT)
• An undersized ICL (less than 0.125 mm vault) may
  increase the risk of anterior subcapsular
  opacification.
• An oversized ICL (more than 1 mm vault) may cause
  angle closure glaucoma, endothelial damage and
  glare.

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RESULTS

• The mean for the measurements
• Orbscan II (white to white) 11.63mm 0.35
• UBM (sulcus diameter) 11.73mm 0.30
• Paired measures one by each technique and
  analyzed by the Bland Altman Technique3,4 that
  plotted the difference between the results by the
  two measuring instruments against their means.

• Twenty one eyes of 17 patients
• 11 men and 6 women
• 11 right 10 left eyes
• Mean age was 25.24yrs 5.72
• Mean refractive spherical equivalent
• PREOP 16.51 D 3.68
• POSTOP -1.16 D 0.87
• Vault
• NO LOW VAULTS
• 1 High vault 1.51mm
• Mean Vault (UBM)
• 0.67 0.29

3. Altman DG and Bland JM Measurement in
Medicine the Analysis of Method Comparison
Studies, The Statistician, 32, 307-317. 4.
Bland JM and Altman DG Statistical Methods for
Assessing Agreement between 2 Methods of Clinical
Measurement, Lancet, 986, 307-310.
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HIGH VAULT
ICL
Iris
Anterior Capsule
Cornea
ICL
Anterior Capsule

• Shallow anterior chamber
• Large gap between
• ICL Anterior Capsule

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Bland Altman Plot

• X- Axis Mean of a pair of values obtained by
  Orbscan and UBM
• Y- Axis Difference between each pair of
  measurements
• 95 of the values fall within Mean Difference
  2 standard deviations
• Good agreement between the values obtained by
  the 2 instruments
• However the trendline indicates that Orbscan
  would
• Underestimate in small eyes
• Overestimate in large eyes

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IMPACT ON ICL SIZING
VAULT ASSESSMENT VAULT ASSESSMENT
Slit Lamp UBM
1.51 High

0.54 Normal
0.65 Normal
0.63 Normal

• X- Axis ICL diameter as calculated by Orbscan
• Y- Axis Difference between Orbscan UBM ICL
  diameters
• The trendline indicates that Orbscan ICL
  diameter is
• Underestimated in small eyes Overestimated in
  large eyes
• The vault assessment by slit lamp UBM are
  denoted alongside
• Normal vault Difference in ICL diameter as
  calculated by the 2 techniques is lt 0.5mm

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DISCUSSION

• All techniques have some measurement error
• "Do the two methods of measurement agree
  closely?"
• Does the technique used influence the ICL
  diameter?
• How does the difference affect the vault?
• Same ICL diameter irrespective of the technique
  in 12 of 21 eyes (57.14)
• The height of the vault remains within normal
  limits if ICL diameter does not vary by gt 0.5mm
  (20 of 21 eyes 95.24)
• If Orbscan underestimates then the vault would be
  lower.
• If Orbscan overestimates then the vault would be
  high (1 eye 4.76)
• Caution for larger eyes as Orbscan seems to over
  estimate

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CONCLUSION

• The Visian implantable contact lens (ICL)
  requires accurate measurements of sulcus to
  sulcus diameter for implantation.
• There was good agreement between the UBM
  OrbscanII
• UBM may be better in relative anterior
  megalophthalmos as Orbscan tends to over estimate
  in larger eyes.
• UBM should be mandatory in the preoperative
  evaluation as it increases the predictability of
  the postoperative vault and thus enhances the
  safety of the procedure.