1. 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

2. 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 30:1982–8
2. Choi KH, et.al, “Ultrasound biomicroscopy for determining visian implantable contact lens length in phakic IOL implantation.” JRS

3. 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.

4. 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

5. SULCUS ESTIMATION ORBSCAN UBM

6. 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 to mm ( ½ CT to 1 ½ CT)
An undersized ICL (less than 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.

7. RESULTS Twenty one eyes of 17 patients 11 men and 6 women
11 right & 10 left eyes
Mean age was 25.24yrs
Mean refractive spherical equivalent
PREOP: D
POSTOP: D
Vault
NO LOW VAULTS
1 High vault: 1.51mm
Mean Vault (UBM):
The mean for the measurements
Orbscan II (white to white) = 11.63mm
UBM (sulcus diameter) = 11.73mm
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.
3. Altman DG and Bland JM “Measurement in Medicine: the Analysis of Method Comparison Studies,” The Statistician, 32,
4. Bland JM and Altman DG “Statistical Methods for Assessing Agreement between 2 Methods of Clinical Measurement,” Lancet, 986,

8. ICL to Anterior Capsule = 1.51mm
HIGH VAULT
ICL to Anterior Capsule = 1.51mm
Endothelium to ICL = 1.32 mm
ICL
Iris
Anterior
Capsule
Cornea
ICL
Anterior
Capsule
Shallow anterior chamber
Large gap between
ICL & Anterior Capsule

9. Bland Altman Plot
Mean Difference =
Limits of Agreement = and
Pitman’s test of difference in variance
p = 0.426
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

10. IMPACT ON ICL SIZING VAULT ASSESSMENT Slit Lamp UBM 0.54 Normal 0.65
1.51
High
0.54
Normal
0.65
0.63
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 < 0.5mm

11. 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 > + 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

12. 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.