Biometry before catarct surgery Ulrich Spandau Department of Ophthalmology, University of Uppsala, Sweden
I will talk about: A-scan biometry – IOL Master biometry Examination of a patient IOL talk with the patienten Clinical examples Tipps & tricks
How good is today the quality of the calculation of an IOL ? Question: How many patients with target refraction emmetropia become hyperopic? Svar: 40% Question : How many patients land at ± 0,5D? Svar: Only 72% Question : How many patients land at ≥ 10D Svar: 40 patients Europeiska katarakt register (n=142572 patienter i 2014)
IOL-Master (laser, similar to TV) Difficult measurement for ultrasound Easy measurement för IOL master IOL-Master (laser, similar to TV) A-scan (ultrasound, (similar to radio) Ultraljud mäter med ljud, IOL master mäter med ljus Difficult measurement for IOL master Easy measurement for ultrasound
Ultrasound: A-scan Measures from cornea to ILM ILM
IOL Master Measures from cornea to RPE RPE 6
Important Biometry with PMMA IOL: Big mistake with ultrasound; small mistake with laser (IOL Master) Biometry with silicone oil filled eye: Big mistake with ultrasound (eye becomes 30% longer); small mistake with laser (IOL Master) Caution: In case of mature cataract=> ultrasound; in case of PMMA-IOL and silicone oil =>IOL Master Allt som är vattenfylld (biologisk, t.e.x matur katarakt) ultraljud; vid IOL, vid silikonolja IOL Master 7
IOL Master biometry Oculus Dexter Oculus Vänster IOL formula Three important parameters for formula AL=Axial length K=Keratometry Oculus Dexter Eye status Different lins types Oculus Vänster OD=Oculus dexter och OS=Oculus vänster; Vänster alla paramter av formeln AL, k1, k2
IOL formula Haigis Hoffer Holladay SRK
SRK Donald R. Sanders, PhD, MD; John A. Retzlaff, MD; Manus C. Kraff, MD SRK/T (Teoretisk)
SRK I functions well for 22.0 – 24.5 SRK II was developed for long and short eyes: < 20.0mm => add +3 to A constant 20.00 – 20.99 => add +2 to A constant 21.00 – 21.99 => add +1 to A constant 22.00 – 24.5 old SRK I formel > 24.5mm => add -0,5 to A konstant Problem: 20.99mm => add +3 BUT 21.00mm => add +2 => Development of SRK/T
IOL formula P= A – 2,5 x L – 0,9 x (K1+K2)/2 P= IOL power in emmetropia A= IOL constant L= axial length in mm K= corneal curvature i diopters
IOL formula contains 1) Keratometry 2) Axial length 3) A-constant
A-scan biometry Formula Tre essential parameter Different lins types Lins typ A
Examination of patient Examine ALLWAYS BOTH EYES 1) Autorefractor 2) Glasses 3) Biometry 4) Function of eye Viktigast är autorefraktor och biometri
Biometry: Status of eyes Pseudophakic Phakic
Measurement of axial length with IOL master
Choose correct eye status
Empty space=> do a manual entry
Target refraction
Target refraction Cataract surgery first eye ? OR Cataract surgery second eye?
Cataract surgery first eye Free choice for target refraction
Cataract surgery second eye Do an objective refracation of the first eye Target refraction of the second eye shall correlate with refraction of the first eye Example: Pseudophakic eye: -2,0D, phakic eye: +1,0D, which vilken target refraction? (-2,0D)
Target refraction => Talk with patient Required measurements: Refraction of eyes Refraction of glasses and biometry
Example 1 Patient is sailor and wishes to read his instruments in a disctance of 1,2m: Target refraction? Formula: 1/X => 1/1,2m=0,8D
Example 2: Hyperopia Refraction: +8,0D Patient wears his glasses the whole time Plan light hyperopia: +0,25-0,5D He/she will no become myopic
Example 3: Grav myopia Refraction: -8,0D Patient wears glasses constantly Plan myopia: -1,0D Patient does not want to be hyperopic
Example 4: Reading myopia Refraction: -3,0D Patient reads without glasses Target refraction: -3,0D
Caution: Hyperopic shift According to the cataract register many eyes become hyperopic after cataract surgery (cirka +0,5D) => In case of emmetropia plan for -0,5D
My favourite target refraction Dominant eye: Emmetropia Not-dominant eye: Light myopia (-0,75sph)
Wrong postoperative target refraction : Where is the mistake? Everything between +/- 1,5D is acceptable Double-check: Did I implant correct IOL? Was the biometry correct? => repeat biometry postoperatively (pseudophakic acryl) Do OCT to exclude a membrane 5 det borde vara rätt
Postoperative anisometropia: Surgical action 1) IOL change 2) Implantation of an add-ON IOL
Lins change
Video: Lens change
add-ON IOL Photocourtesy 1stQ, Tyskland
Tipps and tricks
Caution in case of white cataract !! Swinging flash-light test: RAPD pos => no surgery RAPD neg => surgery
Tipps in case of mature cataract Difficult to measure axial length with A- scan: Change settings to ”aphakic” BUT: AXL becomes too short Add 0,3mm to AXL
Caution in case of LASIK!! In case of LASIK surgery => Use formula Haigis-L
Caution!! Hard contact lenses => no contact lens use for 1 month, otherwise wrong biometry
Conclusion A-scan: measures from epithelium to ILM IOL Master: measures from epithelium to RPE Biometry: Are there strange values (for example IOL of 50D, AXL of 17mm)? Dialogue with patient regarding lins choice (In case of reading myopia => target refraction: -3,0D) 3 är näthinnan avlossad?
Thank you for your attention