How do we use the Galilei for cataract and refractive surgery? Douglas D. Koch, MD Mariko Shirayama, MD* Li Wang, MD, PhD* Mitchell P. Weikert, MD Cullen Eye Institute Baylor College of Medicine Houston, TX *Financial Interest Disclosure: travel expenses covered by Ziemer
The problems Even in eyes without currently detectable risk factors, there is still risk of ectasia after LASIK Subclinical corneal ectatic disorders are major risk factors for ectasia after refractive surgery Forme fruste keratoconus (FFKC) Forme fruste pellucid marginal degeneration (PMD)
What do you check before refractive surgery? Age Refraction / visual acuity Dry eye screening Central K value Anterior corneal topography Central corneal thickness Residual stromal bed thickness Keratoconus prediction indices Anything else?
Now we can check two additional parameters: Thinnest point of the cornea Posterior corneal curvature
Corneal thickness from the Galilei* CCT repeatability CCT compared with ultrasonic pachymetry (USP-GP) Virgin corneas (77 eyes) Post-LASIK/PRK (39 eyes) *Weikert MP and Al-Mohtaseb, ZN
Repeatability of 3 CCT measurements Virgin Cornea (77 eyes) Average of 3 measurements Galilei US Pachymetry CV(%) 0.37 0.32 SD(μm) 2.0 1.8 Repeatability Coefficients(μm) 3.92 3.53 Post LASIK / PRK (39 eyes) Average of 3 measurements Galilei US Pachymetry CV(%) 0.50 0.39 SD(μm) 1.9 2.4 Repeatability Coefficients(μm) 4.7 3.7 CV= Coefficient of variance; SD= Standard deviation Repeatability Coefficient = 1.96* SD
US pachymetry vs. Galilei (CCT) Virgin cornea Mean difference = -0.7 ± 7.1 µm Differences in CCT (USP Galilei) LoA=27.8 µm Mean CCT (µm) of USP and Galilei
US pachymetry vs. Galilei (CCT) Post LASIK / PRK Mean difference = -6.2 ± 9.9 µm Differences in CCT (USP Galilei) LoA=38.8 µm Mean CCT (µm) of USP and Galilei
Use CCT data with Galilei before surgery High repeatability Comparable to US pachymetry for virgin eyes as well as Post-LASIK/PRK Enables us to determine true thinnest portion of the cornea
The critical role of the posterior elevation map Helps to diagnose FFKC or early KC Helps to distinguish normal from early change of FFKC or KC Excellent for educating the patient
Case 1 A 40 year-old man Wishes to correct his myopia and high astigmatism Not a contact wearer MR OD: -4.00 +3.00 4 BSCVA 20/20 OS: -3.75 +3.00 168 BSCVA 20/20 Slit-lamp Both eyes were normal
Case 1: OD-Corneal topography Against-the Against-the rule rule astigmatism astigmatism Slightly protruding Slightly protruding
Case 1: OS-Corneal topography Against-the rule astigmatism Slightly protruding
Case 1: OD- Galilei Keratoconus report CCT: 514μm thinnest point: 505μm KPI: 0% Posterior elevation: 11 μm
Case 1: OS- Galilei Keratoconus report Skewed meridia CCT: 517μm thinnest point: 507μm KPI: 0% Posterior elevation: 8 μm
Case 1 Recommend not to have refractive surgery Follow-up to monitor status
Case 2 A 75 year-old man Has cataract in both eyes Topographically diagnosed keratoconus in the right eye MR OD: -0.75 +0.50 130 BSCVA 20/70* OS: -1.00 +0.50 90 BSCVA 20/30 Slit-lamp OD: no apparent keratoconus findings OS: normal cornea * The BSCVA in the right eye improved to 20/25 after cataract surgery
Case 2: OD-Corneal topography Inferior steepening Inferior steepening
Case 2: OS-Corneal topography Looks OK
Case 2: OD- Galilei Keratoconus report CCT: 539μm thinnest point: 516μm KPI: 43.4% Posterior elevation: 35 μm
Case 2: OS- Galilei Keratoconus report Normal! CCT: 548μm thinnest point: 533μm KPI 14.6% Posterior elevation: 27 μm
Case 2: Issues raised Does posterior corneal shape change before anterior corneal shape in some or all cases of KC or FFKC? Or are early anterior corneal changes masked by the epithelium?
Case 3 A 48 year-old man Referred for evaluation of correcting myopia in his left eye MR OD: no MR recorded UCVA 20/25 OS: -2.00 +0.75 150 BSCVA 20/15 Slit-lamp Both eyes were normal
Case 3: OS-Corneal topography Slight steepening
Case 3: OS-TMS4 (Corneal videokeratography) Klyce/Maeda KCI 0.0% Severity Smolek/Klyce KSI 0.0% Severity Keratoconus pattern was not detected
Case 3: OS- Galilei CCT: 518μm thinnest point: 503μm KPI: 8.6% Posterior elevation: 17 μm
Case 3: OS- RTVue (OCT) CCT: 484μm thinnest point: 472μm
Case 3 Recommend not to have refractive surgery Follow-up to monitor status
Case 4 A 26 year-old woman Wishes to correct her high myopia MR OD: -6.75 +1.00 130 BSCVA 20/20 OS: -4.75 +0.50 55 BSCVA 20/20 Slit-lamp Both eyes were normal
Case 4: OD-Corneal topography Slightly inferior steepening
Case 4: OS-Corneal topography Slightly inferior steepening
Case 4: OD-TMS4 Klyce/Maeda KCI 0.0% Severity Smolek/Klyce KSI 0.0% Severity Keratoconus pattern was not detected
Case 4: OD- Galilei CCT: 549μm thinnest point: 538μm KPI: 0% No abnormality in Posterior elevation map
Case 4: OS- Galilei CCT: 548μm thinnest point: 536μm KPI: 0% No abnormality in Posterior elevation map
Case 4 Posterior elevation map might help to distinguish normal from FFKC or early KC
Pearls in screening for refractive surgery Use CCT data Use posterior elevation map Even if the patients have no abnormalities on anterior surface, something might be hidden on posterior cornea
Suggestions before refractive surgery Check the Placido mires first to search for surface irregularity Inspect color maps Axial curvature Tangential curvature Corneal pachymetry Anterior elevation best fit sphere Posterior elevation best fit sphere
Future needs Better keratoconus detection indices combining data from: Anterior corneal surface Posterior corneal surface Pachymetry
What can we obtain from the Galilei before cataract surgery?
1) Corneal powers from the Galilei Sim K Anterior cornea using combined information from the Placido rings and the Scheimpflug image Measured area is 1-4mm diameter
Corneal powers from the Galilei Total corneal power (TCP) Ray Tracing both anterior and posterior corneal powers and corneal thickness TCP Meridian Steep and flat meridians 1-4mm diameter TCP Central Over 4mm central zone
Corneal power from the Galilei Recent study SimK Repeatability SimK compared with Atlas, IOLMaster and Manual ketatometer Virgin corneas (20 eyes)
Repeatability of 3 corneal power measurements Virgin Cornea (20 eyes) Galilei (Ave SimK) Atlas (Ave SimK) IOLMaster Manual CV (%) ± SD 0.12±0.07 0.22±0.12 0.09±0.07 0.18±0.12 SD (D) 0.055 0.096 0.042 0.077 ICC 0.998 0.994 0.996 0.996 There were no statistically significant differences among the devices (All P > 0.05), although there were trends for better repeatability for the IOLMaster and Galilei CV= Coefficient of variance; SD= Standard deviation; ICC= Intraclass correlation coefficient
Galilei vs. other devices Virgin Cornea (20 eyes) Difference in corneal power (D) 0.5 0.3 0.1-0.1-0.3-0.5 Galilei vs. IOLMaster Mean Difference = -0.12 ± 0.07 D 40 42 44 46 Mean corneal power (D) of Galilei and IOLMaster LoA=0.27* Difference in corneal power (D) 0.5 0.3 0.1-0.1-0.3-0.5 Galilei vs. Atlas Mean Difference = -0.08 ± 0.14 D 40 42 44 46 Mean corneal power (D) of the Galilei and Atlas LoA=0.54 95% LoA between Galilei and IOLMaster was significantly smaller than those for the other paired comparisons
Galilei vs. other devices Virgin Cornea (20 eyes) Galilei vs. Manual Atlas vs. IOLMaster Mean Difference = 0.05 ± 0.13 D Mean Difference = -0.04 ± 0.12 D Difference in corneal power (D) 0.5 0.3 0.1-0.1-0.3-0.5 40 42 44 46 Mean corneal power (D) of Galilei and manual keratometer LoA=0.51 Difference in corneal power (D) 0.5 0.3 0.1-0.1-0.3-0.5 40 42 44 46 Mean corneal power (D) of Atlas and IOLMaster LoA=0.48
SimK values with Galilei High reproducibility Comparable to IOLMaster
Total corneal power from the Galilei Recent study IOL calculation accuracy with SimK and TCP from Galilei IOL calculation with Galilei compared to those with Atlas and IOLMaster Normal eyes (75 eyes)
IOL power calculation with Galilei 75 eyes with implantation SN60WF included Used Holladay 1 formula SF optimized for each method of corneal power measurement Refractive prediction error (PE) Postoperative MRSE compared to predicted refraction for implanted IOL MAE: mean absolute error
IOL power calculation with Galilei Normal eyes (75 eyes) Corneal power measurement MAE(D) ±SD Galilie SimK 0.39 ± 0.31 Galilei TCP Meridian 0.41 ± 0.32 Galilei TCP Central 0.42 ± 0.33 IOLMaster 0.37 ± 0.30 Atlas SimK 0.39 ± 0.34 There were no statistically significant differences among devices
IOL calculation with Galilei for post- LASIK/PRK eyes Recent study IOL calculation accuracy with SimK and TCP from Galilei Post-LASIK/PRK eyes (63 eyes)
IOL calculation with Galilei for Post- LASIK/PRK eyes Gold standard Corneal power obtained from clinical history method (HisRP) Corneal powers from the Galilei SimK AxialMerid: Steep and flat meridians 1-4 mm diameter AxialCen: Axial curvature central average over 4-mm zone Total corneal power ( Ray Tracing) RayMerid: Average of steep and flat meridians 1-4 mm diameter RayCen: Average over central 4-mm zone
IOL calculation with Galilei for Post- LASIK/PRK eyes Deviation from HisRP = Prediction error Value = (corneal power) - HisRP Positive = overestimate corneal power hyperopic surprise
IOL calculation with Galilei for Post-LASIK/PRK eyes Deviation from HisRP (D) 0.8 0.6 0.4 0.2 0.0-0.2-0.4-0.6-0.8 * 0.38 0.37-0.44-0.43 AxialMerid AxialCen RayMerid RayCen * Hyperopic results Myopic results No significant differences between methods
IOL power calculation with Galilei Normal eyes Galilei predicts IOL power as well as the IOLMaster Post-myopic LASIK/PRK Recommend use of Total Corneal Power from the Ray Tracing calculation Can be inserted into IOL power calculator at www.ascrs.org
ASCRS online IOL power calculator: http://www.ascrs.org/
2) Total corneal Wavefront Galilei measures the total corneal wavefront Data from both anterior and posterior surface Spherical aberration (SA) is linked to contrast sensitivity Use the corneal SA to determine IOL asphericity AcrySof IQ (SA: -0.20 μm) Tecnis (SA: -0.27 μm) SofPort AO (SA: 0 μm) Standard (SA: +0.18 μm)
3) Placido mires Assess surface irregularity If present, treat before cataract surgery Epithelial basement disease Epithelial debridement Salzmann s nodular degeneration Superficial keratectomy
4) Posterior elevation map Will we be able to perform corneal refractive surgery to refine the refractive outcome after cataract surgery? OK Pt will have an extra option (LASIK or PRK) to refine refraction after cataract surgery NO Pt will not be a candidate for corneal refractive surgery
Pearls for screening for cataract surgery Use the IOL power map including Corneal power Spherical Aberration Placido mires Posterior elevation
Thank you for your attention!