Transcript Matt Sheehan - PhD progress presentation

Personalised eye modelling for
customised intraocular lens designs
Matthew Sheehan, Eamonn O’Donoghue, Conor Sheil and Alexander Goncharov
Photonics Ireland, Dublin, Ireland, September 7th- 9th 2011
History
• Ridley’s first intraocular lens – 1949
• Kelman’s first phacoemulsification procedure - 1967
• First FDA approval for an intraocular lens - 1981
• Refractive surgery increases in popularity – 1990s
Intraocular lens power calculations
• Geometrical optics equations - 1973
• Linear regression equations - 1980
• Modern formula - 1980s to 1990s
What lens power should we use ?
n aq
n vit
P

l  c (n aq /K)  c
P  A  2.5l  0.9K
Refractive surgery popularity increases
Experiment
Aims
• Investigate corneal shape changes due to the surgical incision
• Find parameters for predicting the implant resting position/depth
• Perform surface metrology for a specific implant design
Protocol – measurements performed pre and post cataract surgery
• Wavefront aberration of the eye (ZyWave)
• Refractive error and corneal curvature (Nidek ARK)
• Segmented axial length (Lenstar)
• Corneal topography (Atlas)
• Interferometry on the specific intraocular lenses (FISBA)
Final Goal
• Aquire knowledge to perform personalised eye modelling for
customised intraocular lens designs
Biometry data summary
• 165 patients enrolled (64 males, 101 females)
• 33 excluded eyes
• 303 included suitable eyes (pre-surgery)
• age range: 32 to 98 years (mean 74 years)
• 88 eyes with usable post-surgery review data
• 74 eyes with usable single-echo implant data
• 14 eyes with usable double-echo implant data
• review period: 10 to 122 days (mean 31 days)
Lens implantation depth
Cornea ~ 500 microns
Retina ~ 200 microns
Cataractous Lens ~ 4 mm
Vitreous ~ 16 mm
Intraocular lens ~ 900 microns
Predicting lens implantation depth
Surgery-induced corneal topography changes
Personalised eye modeling
Conclusions
• Early days for personalised eye modelling and
customised intraocular lens designs
• Modern biometry instruments allow accurate
measurement of two key parameters
- optical segmented axial length
- posterior corneal topography
• This methodology may be beneficial for typical
cataract surgery patients as well as those with
extreme ocular parameters (previous refractive
surgery patients, high hyperopia)