INTRAOCULAR LENS POWER CALCULATION BY IMMERSION A-SCAN BIOMETRY VERSUS CONTACT A-SCAN BIOMETRY MEASUREMENTS BEFORE CATARACT SURGERY

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INTRAOCULAR LENS POWER CALCULATION BY IMMERSION
A-SCAN BIOMETRY VERSUS CONTACT A-SCAN BIOMETRY
MEASUREMENTS BEFORE CATARACT SURGERY

• Burak Bilgin, M.D., Kadir Eltutar, M.D., N.
  Demet Ozcelik, M.D.

Istanbul Education and Research Hospital
Opthalmology Department, Turkiye. Almangoz
Eye Center, Nisantasi, Istanbul, Turkiye.
The authors state that they have no proprietary
interest and they have not received any grants or
funds in support of the study.
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PURPOSE

• The study was designed to evaluate the difference
  in contact A - scan biometry versus immersion A -
  scan biometry measurements for intraocular lens
  (IOL) power calculations before cataract surgery.
  .

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METHODS

• Foldable acrylic hydrophobic IOLs ( AcrySof
  SA60AT, SN60WF, SA30AT, SN60AT ) were implanted.
• Axial length (AxL) measured by contact A - scan
  and immersion biometry were compared.
• The estimated refraction ( -0,50 Diopters ) was
  compared with postoperative refraction achieved
  on the days 1, 7,15 and 30.
• Highly myopic eyes with posterior staphyloma were
  excluded from the study to avoid the
  miscalculation of IOL power.

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RESULTS

• Immersion A-scan measured longer axial length
  than contact A-scan biometry ( p lt 0,05 ).

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RESULTS

• Compared to contact A-Scan biometry, estimated
  refraction measurements with immersion A-Scan
  biometry were closer to refraction achieved
  postoperatively.

SE Spherical Equivalent
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RESULTS

• Lens power prediction error for the contact
  A-scan group was 0,93 0,67 D at the visit on
  day 30, and 0,47 0,46 for the immersion A-scan
  group respectively. The difference was
  statistically significant (plt0,05 ).

SE Spherical Equivalent
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CONCLUSIONS

• IOL power calculation to achieve postoperative
  emmetropia, is an important factor in
  phacoemulsification surgery.
• Our results show that lens power prediction
  error with immersion A-Scan biometry is lower
  compared to contact A-Scan biometry ( p lt 0,05 ).
• Immersion biometry gives longer axial length
  measurements compared to contact A-Scan biometry
  ( p lt 0,05 ).
• Choosing the appropriate formula for IOL power
  calculation according to axial length measured by
  ultrasound biometry plays a major role for
  achieving emmetropia after uncomplicated
  phacoemulsification surgery.