Wavefront higher order aberrations in Dohlman/Boston keratoprosthesis and normal eyes Kalliopi Stasi, Seth Pantanelli, Geunyoung Yoon, Greg McCormick, James Aquavella Rochester Eye Institute and Center for Visual Sciences University of Rochester, NY Research supported in part by a grant from Research to Prevent Blindness
Background Dolman/ Boston keratoprosthesis (KPro) is an artificial cornea PMMA device Alternative to penetrating keratoplasty (PK) with good anatomic results and quick visual recovery, reserved usually for failed PK The wavefront aberrations through this device have not been reported or compared to PK patients or normal subjects
KPro patients can have good visual acuity and visual fields according to their visual potential as well as very good visualization of the fundus It is not known how the routine use of bandage contact lens on KPro eyes affects the quality of their vision
The quality of vision can be evaluated with measuring wavefront aberrations (deviation from ideal eye) lower order aberrations (like sph/cyl, correctable, 85% of total) higher order aberrations (not correctable w. glasses or CLs) Abnormal eyes such as PK and KCN eyes as well as symptomatic post-lasik eyes have significantly more higher-order aberrations (HOAs) than normal
Wavefront Aberration: deviation from reference (ideal) wavefront captured with Shack-Hartmann wavefront sensor Ideal (Perfect) Eye Perfect eye Aberrated Eye (displaced spots) Real eye Lenslet array Spot Image
Mathematical description of the wavefront: Zernike polynomials 2nd 3rd Lower-order aberrations (correctable) Zernike Pyramid Defocus Astigmatism 4th Higher-order aberrations (not correctable) 5th Trefoil Vertical Coma Horizontal Coma Trefoil Quadrafoil Secondary Spherical Secondary Quadrafoil AstigmatismAberrationAstigmatism Phase advance 0 Phase delay Pentafoil Secondary Coma Secondary Trefoil Secondary Trefoil Secondary Coma Pentafoil
Questions 1) What is the optical quality of Dohlman/Boston KPro before and after implantation? 2) How does the optical quality of KPro compare to normal eyes? 3) Does the routine bandage contact lens affect the optical quality of the implanted KPro?
Methods Wavefront aberrations: large dynamic-range Shack-Hartmann wavefront sensor Pupil camera Lenslet array
Groups: (I) KPro devices (n=3) mounted to custom made plastic stand (II) One patient implanted with KPro with and w/o bandage soft contact lens, dilation (1% tropicamide) 20 spot images acquired and averaged for single set of Zernike coefficients (III) Wavefront aberration data on 50 normal eyes adjusted for a 3mm pupil in order to be comparable to keratoprosthesis data (3.2mm optical zone) The higher order aberration root mean square (HORMS) was calculated up to the 5th order (mathematical way to appreciate the magnitude of aberrations like spherical equivalent for sph-cyl).
Results HORMS of normal eyes (3mm pupil, n=50) was 0.045 + 0.018μm HORMS of KPro devices (n=3) was 0.111 + 0.009 μm The difference between Kpro and normal eye groups was 0.068 μm This difference is equivalent to about 0.18 Diopters of sphere
Kpro patient 44yo CM s/p failed PK for advanced Lattice K pro & PCIOL (B&L aspheric-zero spherical aberrations IOL) Postop day 4 VA uncorrected: 20/30+2 POD 1 POD 4
HORMS (μm) Normal eyes (3mm pupil) n=50 0.045 + 0.018 KPro device (3mm optical zone) n=3 0.111 + 0.009 KPro pt w. PCIOL (dilated) n=1 without CL 0.344 with CL 0.420 with CL & lubr.. drop 0.399
HORMS (um) for 3mm pupil 0.5 0.4 0.3 0.2 0.1 0 normal eye Kpro device Kpro pt (naked) Kpro pt (w. CL) Kpro pt (CL & drop) n=50 n=3 n=1
Higher Order Aberrations increase with increasing pupil size Higher Order Rms Wavefront Error (μm) 2 1.5 1 0.5 0 n=33 n=32 n=31 n=26 3 4 5 6 Pupil Size (mm) KPro pt (PCIOL, POD4) All Symptomatic LASIK Normal Non-Surgical *McCormick et al. Higher Order Aberrations in Symptomatic Eyes with Irregular Corneas After Laser Refractive Surgery. Ophthalmology. 112(10):1699-709, 2005 Oct.
HORMS In Symptomatic Eyes 3.5 Higher Order RMS (6mm and 3 mm Pupil) RMS Wavefront Error (µm) 3 2.5 2 1.5 1 0.5 6mm pupil 3mm pupil 0 Penetrating Keratoconus (n=19) Symptomatic Post Normal LASIK Normal Pre Op Normal eyes, 3mm Kpro pt, 3mm (n=1) Keratoplasty (n=14) LASIK (n=25) (n=46) Eyes (n=46) (n=50) *McCormick et al. Higher Order Aberrations in Symptomatic Eyes with Irregular Corneas After Laser Refractive Surgery. Ophthalmology. 112(10):1699-709, 2005 Oct.
2o trefoil Pentafoil Trefoil Coma Coma Trefoil Quadrafoil 2o Astig Spherical Ab 2o Astig Quadrafoil Pentafoil 2o trefoil 2o coma 2o coma Astig Defocus Astig 0.5 0.4 0.3 0.2 0.1 0-0.1 <1.00 sph <0.25 cyl Wavefront aberrations in Kpro patient (3mm pupil) Kpro pt w. Contact Lens RMS Wavefront Error (μm)
Discussion It is possible to use wavefront technology to objectively measure quality of vision in Kpro pts To our knowledge, a keratoprosthesis device has never been evaluated this way. Higher order aberrations of the Dohlman/Boston Kpro device type I were 0.111μm (equivalent to about 0.18 D sph) and comparable to the optical quality of a normal eye
Discussion Preliminary results of one pt implanted with Kpro and an aspheric zero spherical aberrations PCIOL indicated correctable lower order aberrations equivalent to about 1.25 D sph and a modest amount of non correctable higher order aberrations of 0.4 μm (about 0.50 D sph) The use of routine bandage contact lens and lubricating drops did not alter significantly the amount of wavefront aberrations measured
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