Rainbow Glare as an Optical Side Effect of IntraLASIK Ronald Krueger , MD The Cole Eye Institute Ivey Thornton, MD The University of Alabama School of Medicine Thomas Van den Berg, PhD The Netherland of Ophthalmic Institute
PURPOSE To describe a NEW optical side effect associated with IntraLASIK, called Rainbow Glare
BACKGROUND Retinal images are affected by: • Diffraction • Aberrations • Light scatter
Spectrum or Irregularity from Aberrations to Light Scatter Mrochen M, Semchishen V. From Scattering to Wavefronts- What’s in Between?J Refract Surg 2003; 19: S597-S601.
Aberrations vs. Light Scatter Mrochen M, Semchishen V. From Scattering to Wavefronts- What’s in Between? J Refract Surg. 2003; 19: S597-S601.
Monochromatic Light source “I see 12 spots of red lights surrounding the red stop light!” “When I look at the green light, I see 12 green spots of light instead!” 64 YOWM 3 mth s/p IntraLASIK
Polychromatic light source- Spectrum of Rainbow Colors “ Around white light, the lights are multi-colored!” “they become 12 bars of lights with a prism pattern with colors like the rainbow!” 64 YOWM 3 mth s/p IntraLASIK
LightSource Constructed by patient of Karl Stonecipher, M.D.
METHODS Retrospective review: • 585 eyes (312 patients) sequentially treated with IntraLASIK by R.K. • 6/04 to 8/05 • Group 1: 399 eyes (215 patients) treated with our First IntraLASE • Group 2: 186 eyes (97 patients) treated with our Second IntraLASE
METHODS IRB protocol Post-operative questionaire were completed through clinic/phone follow-up • Halo/ Starburst/ Glare • Transient Light Sensitivity • Rainbow colors around light
First IntraLASE Pulse spot size SMALLER cone angle/ numerical aperture of the focusing optics Second IntraLASE LARGER cone angle Tighter Focus of pulses Size of spot =SMALLER Less Energy per pulse Closer Spacingbetween the pulses METHODS
Intra-Operative Ablation Depth IntraLASE settings METHODS Pre/Post Operative • Refraction • Visual Acuity • Pupil Size • Pachymetry • IOP • Wavefront Ab • Topography • Report of Symptoms
Group 1 contacted 194/215 patients (90.2 %) H/G/SB 31.6% Photophobia/TLS 21.3% Rainbow Glare 37 pt in 69 eyes 19.3% eyes (19.1% patients) Group 2 contacted 85/97 Patients (87.6%) H/G/SB 32.1% Photophobia/TLS 11.7% Rainbow Glare 2 pt in 4 eyes 2.47% eyes (2.36% patients) RESULTS The spectral pattern most closely represented 4-12 radiating bands of rainbow colored light
RESULTS- Statistics Further risk factors related to model type: IntraOp Raster Energy 0.04 0.005,0.36 IntraOp Spot Separation 2.8 1.2,6.2
RESULTS The level of refractive error in IntraLASE I eyes shows a greater incidence of Rainbow Glare in 26 out of 66 hyperopic eyes (39.4%) than in 43 out of 291 myopic eyes (15.17%) • Higher myopic eyes (> -6.00 D)= 21.43% • Moderate myopic eyes (-3.00 to -6.00 D)= 14.38% • Low myopic eyes (< or equal to -3.00 D= 8.82%
TIMING of Rainbow Glare All patients except 1 stated that symptoms occurred immediately after IntraLASIK • One patient: 1 week post-operative Rainbow Glare lasted • < 3 mth: 4.1% • 3-9 mth: 30.1% • > 9 mth: 63.0% • Fail to recall: 2.8%
SPECTRUM PATTERN For each of the 73 eyes (39 patients): • 4 OR 6 bands= 17 eyes • 8, 10 OR 12 bands= 18 eyes • multiple bands= 12 eyes • 5 patients described a halo-like confluent annulus of dispersive rainbow colors= 10 eyes • 8 patient (16 eyes) could not recall the spectral pattern of the resolved rainbow glare.
Discussion Known Spectral Phenomena in Ophthalmic Optics Include: Lenticular Halo – causes a true annulus of rainbow color due to the spacings between the lens fibers in the aging patient (lens fiber spacing ~9 um) Ciliary Corona – diffuse white and multicolored glare radiating from a point light source • Due to small particle light scatter in pre-cataract lens Light source
Discussion Known Spectral Phenomena in Ophthalmic Optics Include: Corneal Edema Related Colors – Rainbow-like pattern associated with an increase in fluid spacing within the stroma Grating Filter Glasses – creates temporary spectral pattern for education and entertainment Other - ? CrystaLens IOL ? LASIK?, etc.
INTRALASE™ Photodisruption Gas & water are absorbed or liberated when corneal flap is lifted Not a cleavage plane that is created, rather a photodisruption plane or an array of microcraters Back Surface The micro-irregularities of the back surface of the flap can create light scatter
Monochromatic Red Light Polychromatic White Light
If the IntraLASE pulse pattern is lined up perfectly from roll to roll… The grating line is perpendicular to the spectrum Directon of Spectrum Horizontal vertical, or even Oblique spectral pattern
Point Light Source 4 or 8 Bands Of Rainbow color
Directiob of Spectrum If the IntraLASE pulse pattern is not lined up perfectly…
Point Light Source 6, 10, or 12 Bands Of Rainbow color
Ө Angular extension (Ө)is inversely proportional to the distance between the spot irregularities (A) • A sin θ = m λ;Θ = angular extent, λ = wavelenth of light, A = grating constant m = diffractive order • The grating constant (A) is the periodicity of the grating lines. λ (violet) = 450 nm, λ (blue) = 470 nm λ (yellow) = 570 nm, λ (red) = 640 nm
Among our patients,The angular extent of the color ranged from 2-5 degrees of arc around point light sources, which could be calculated to correspond to a ~9 um sized spot separation within the corneal interface The SAME spot separation setting in the Intralase models Ө
Why is there a greater relative risk in Group 1? The intensityof rainbow color is brighter when: • The Intralase creates bigger spot sizes • The intensity is proportional to the optical weight of the microcrater • Optical Weight = Volume X Change in Refractive Index • The number of grating lines is greater The relative risk of Rainbow Glare increases with ablation depth. • This may be associated with more interface mismatch & optical weight due to the additional spacing created through increase ablation.
Conclusion • Light scattering from the back surface of the IntraLASIK flap causes a constructive interference and is believe to cause ~20% Rainbow Glare Symptoms of Group I eyes. • The angular extent can be calculated to correspond to a grating size that matches the approximate raster spot separation of IntraLase.
Conclusion • Except for two patients, the Rainbow Glare symptoms was not observed in Group II eyes. This may be due to a tighter focus that minimizes the light scattering phenomenon. • Variance in the quality and numerical aperture of focusing optics can be optimized to minimize the phenomenon of rainbow glare as an optical side effect.
Thank you for your attention