Minimizing Risk in Visian ICL Implantation NO FINANCIAL

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

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 sizing 1 that would only be detected in the postoperative period. • Recent literature: UBM is more reliable 2. 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. 362 -7. dr. mkurian@gmail. com

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. dr. mkurian@gmail. com

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 dr. mkurian@gmail. com ICL SIZING • Horizontal white to white (Orbscan) • Horizontal sulcus diameter (UBM). • ACD

SULCUS ESTIMATION ORBSCAN dr. mkurian@gmail. com UBM

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. dr. mkurian@gmail. com

RESULTS • • Twenty one eyes of 17 patients – 11 men and 6 women – 11 right & 10 left eyes • Mean age was 25. 24 yrs + 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. 51 mm – Mean Vault (UBM): • 0. 67 + 0. 29 • The mean for the measurements – Orbscan II (white to white) = 11. 63 mm + 0. 35 – UBM (sulcus diameter) = 11. 73 mm + 0. 30 Paired measures one by each technique and analyzed by the Bland Altman Technique 3, 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, 307 -317. 4. Bland JM and Altman DG “Statistical Methods for Assessing Agreement between 2 Methods of Clinical Measurement, ” Lancet, 986, 307 -310. dr. mkurian@gmail. com

HIGH VAULT ICL to Anterior Capsule = 1. 51 mm ICL Iris Anterior Capsule Cornea • Shallow anterior chamber • Large gap between ICL & Anterior Capsule dr. mkurian@gmail. com ICL Anterior Capsule Endothelium to ICL = 1. 32 mm

Bland Altman Plot + 0. 592 Mean Difference = -0. 10 + 0. 35 Limits of Agreement = -0. 790 and + 0. 592 Pitman’s test of difference in variance p = 0. 426 - 0. 790 • 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 dr. mkurian@gmail. com

IMPACT ON ICL SIZING 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 < 0. 5 mm dr. mkurian@gmail. com

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. 5 mm (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 dr. mkurian@gmail. com

CONCLUSION • The Visian implantable contact lens (ICL) requires accurate measurements of sulcus to sulcus diameter for implantation. • There was good agreement between the UBM & Orbscan. II • 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. dr. mkurian@gmail. com