Rose K2 IC Lens
Article by Alan Saks - NZ Optics Magazine, May 2008
....I've been having some good results with the relatively new Rose K2 IC lens. It's now almost a year since I first started using Paul Rose's Irregular Cornea version of his evolving series of Rose K lens designs. For a couple of patients in need of large lenses on grafted or surgically altered corneas (re-fractive surgery complications), I've found significant improvements. These improvements are particularly notable in terms of vision and comfort but post lens 'spectacle blur' has also been reduced in some cases.
The lens is also indicated for decentred cones, conditions such as Pellucid Marginal Degeneration (PMD) and other irregular and tricky corneas. So far I've only used them to fit or refit Post Lasik Ectasia and complex Penetrating Keratoplasty (PKP) cases. As with all such things I tend to reserve judgement until I have more cases and longer term follow up but so far results have been promising. Time will tell.
A Case in Point
This case concerns a patient with an unsatisfactory visual outcome following bilateral LASIK. Post-op topographies show signs of LASIK induced keratectasia.
With many of these grief cases one starts with a very unhappy patient. To make matters worse they often have a history of contact lens intolerance. Many were simply tired of the restrictions or hassles of years of contact lens or spectacle use. For some soft disposable lenses had been relatively trouble free.... We're faced with frustrated contact lens refugees who now need to wear complex RGP's - at best soft lenses - that may be less comfortable than their pre-op lenses.
I first saw the pleasant thirty three year old IT professional in October 2005. He had a history of previous RGP's, followed by relatively trouble free low Dk soft torics, prior to LASIK in January 2004. His pre-op Orbscan's were classic regular astigmatism bow-ties with a normal thickness profile. His post LASIK Orbscan and Medmont topographies were diagnostic of LASIK induced corneal ectasia with an unusual asymmetric 'torsional' pattern. Analysis of successive topographies indicated that the left seemed to be progressing.
After battling along with reduced vision and attempts elsewhere with spectacles over nearly two years he consulted me during October 2005 reporting difficulty with computer work and close vision and complaints of ghosting and so on. His history was further unremarkable. Retinoscopy revealed zonal reflexes OU. Subjective refraction revealed;
R 6/15+ +1.75/-1.50 x 13 6/7.5p
L 6/60 +3.75/-3.75 x 141 6/7.5p
With effort he obtained right 6/12 unaided and 6/7.5p binocularly. Near vision was somewhat reduced at only 1.25 M acuity at his habitual computer working distance of 67cm. His main concern was that he'd suffered no problems with close work, prior to LASIK. His current reduced vision and uncompensated, hyperopic irregular-astigmatism was causing occupational issues and stress. We discussed his various options.
Trials and Tribulations
Having previously converted from RGP's to soft lenses for comfort reasons, we initally decided to try the proven SoftLens Toric, whose design generally provides better fitting and stability on Post LASIK topography. Initial trial on the right provided decent 6/9 to 6/7.5p but he felt that this was no better than the unaided vision he was already obtaining. The left trial indicated potential 6/12 to 6/9 VA with the SoftLens Toric.
I previously mentioned the unusual 'torsional' aspect to the topographies and wondered whether a rather unusual superior lid position, with a strong angular effect across the corneas, was responsible. It also affected soft toric rotation and stability. At this point we both agreed that the soft option did not offer the vision he required and we proceeded to fit Capricornia Post Corneal Surgery (PCS) lenses, with which I have obtained good results in similarly tricky cases over the past few years.
He did reasonably well wearing these PCS large-diameter RGP's however became increasingly unhappy wearing his right lens as he developed lens-induced topographic changes which caused spectacle blur. When he removed his lenses at the end of the day he felt totally lost. He thus preferred the relatively good uncorrected right vision which took over and provided 'cover' at night, when he removed the left.
He consulted me for a follow-up in June 2007. He was by now habitually wearing only the left lens. I suggested a refit of his left eye with the then new Rose K2 IC lens to see if we could improve on the fit, comfort and vision. The large diameter RK2 IC is similar in some ways to the PCS but with advanced abberation control optics and improved back surface geometry, it seems to provide better results. This lens indeed provided a better fit in this case with better centration, improved comfort and a full line or two of improved acuity. He was rather pleased and achieved 6/6- for the first time since undergoing LASIK in January 2004.
In January 2008 he reported being so happy with the left he requested we have another go at improving his right vision. We duly did and obtained excellent results in terms of VA with the RK2 IC and at the same time scored the added bonus of eliminating the spectacle blur. Comfort and tolerance proved to be very good.
His current RK2 IC RGP Rx is;
R BC: 8.07mm / Ø: 11.2mm / F = -2.75 6/7.5
Boston XO UV Violet with one step increased edge lift.
L BC: 7.33mm / Ø: 11.2mm / F = -7.00 6/6
Boston XO UV blue with Double increased edge lift.
One can do simulations of lift for this design with recent versions of Medmont Studio 4. Bear in mind NaFl simulations tend to be less reliable with extreme corneas but they can be a guide. There's no substitute for actual trial lenses.
I've just added a 6.00mm and 6.20mm base curve to my RK2 IC fitting set for a rather steep-apex, hydropsed cone I am attempting to refit. Even the 6.00 looked too flat. I've also recently done one with some ACT 'tuck'.
Another, on a 90 year old with a graft due to Fuch's and radical astigmatism led to some trapping, dimpling and variable vision. She opted to remain with her old PCS version that's done the trick for the better part of this century. I'm tending to flatten my fits as I fine tune things to avoid trapping/dimpling or peripheral tightness. Of course there are cases where I need to go significantly steeper. It's always a fine balance between apical, peripheral and mid peripheral clearance or bearing.
One must take great care to custom fit the base curve and periphery.
Just because we get decent vision and centration doesn't mean that's the best, safest fit. Too many people have for too long made that mistake; fitting cones way too flat with resultant apical scarring.
We must also be ever cautious of limbal insult and resulting vascularised limbal keratitis. Inducing such vessel growth is never desirable and indicates physical and physiological insult. In grafts, the sequelae of this neovascular and inflammatory cascade can be particularly severe and can ultimately lead to graft rejection. It can seemingly develop surprisingly fast in some cases, judging by images and case histories I've been sent and cases I've seen. Its best to avoid all the resulting cortisone nad immunosuppression... At any rate with the necessary due care and attention, the benefit of modern lathe technology, CNC,CAD/CAM and the vision of many, we can achieve some fantastic results. We have at our disposal lens designs that were not possible just a decade or two ago. We should use them.
Enhancing 'quality of life' for these otherwise visually frustrated individuals is most satisfying. I received the following email from the aforementioned patient a few weeks ago.
Just a quick note to let you know how the lenses are now. The right lens has settled down nicely and I'm up to full wear (12-16 hours/day). The vision is excellent and having both lenses has improved my general depth perception (as you said, not dropping too many balls when playing cricket!) Anyway, thanks again for all your help...
It's my pleasure.
Happy to oblige.
Dip. Optom (SA), MCOptom (UK), FAAO (USA), FCLS (NZ)