Time is a concept understood only by humans apparently. Very few creatures in the animal world have much concept of yesterday or tomorrow. In the medical profession, we certainly understand the concept of time. Time heals. Time left. Time in theatre. Time out. The list goes on.
In the field of ophthalmology, time passes more quickly given the pace of innovation.
I want to share the concept of time and how it changes the management of common conditions over a short period, perhaps 15 years or less.
Take the case of a patient with progressive keratoconus (steepening of the cornea resulting in irregular astigmatism and reduced quality of vision) who also has a cataract that requires surgery. Three eras, within the timeframe of less than 15 years, provide fascinatingly different approaches and outcomes.
Keratoconus treatment: pre-2007
Before 2007 there was no treatment for progressive keratoconus in Ireland until corneal cross-linking (CXL) was introduced in January 2007, the same month that CXL was approved in the EU.
The keratoconus aspect was previously managed either by rigid contact lenses and if the steepening progressed, by means of a corneal transplant. The cataract was removed using phaco-emulsification of the cataract (breaking the natural lens up into small pieces that can be aspirated through a tiny, sutureless incision, using ultrasound) and replacing it with an intraocular lens (IOL). A challenge in this case would also be the calculation of the IOL power required. When replacing the natural lens, the surgeon has it within his or her power, to select an IOL of the appropriate power to improve the patient’s vision without the use of spectacles. IOL power calculation is notoriously difficult, even today, in these aberrated corneas and getting the IOL power right was a particularly difficult issue.
Furthermore, the diagnosis was very much a clinical diagnosis and there was not much objective validation of the corneal contribution versus the lens contribution to the reduced vision.
Keratoconus treatment: 2007 to present day
From 2007 to the present day CXL has changed the way that we manage keratoconus completely. Back in 1994, I was doing more than 50 corneal transplants per year, that number now is so small, that I no longer do corneal grafts. I refer them to someone that is still doing a reasonable number. This is all thanks to CXL. This procedure strengthens the cornea and, in some cases, even improves the corneal shape thereby improving the quality of vision. CXL was traditionally performed by removing the corneal epithelium, hence leading to a healing phase of the epithelium. For the past six years we are performing 90 per cent of our CXL procedures without removing the corneal epithelium, making the procedure safer, allowing less time off work with much less morbidity.
Combining the procedure with topography-guided photo-refractive keratectomy (TG-PRK) has also allowed the regularisation of the cornea before the improved corneal shape is stabilised by the CXL. This leads to improved corneal optics and simpler and more accurate IOL power calculations for the IOL to be selected. The only IOL in these aberrated corneas that could be contemplated was a monofocal (single focal power) IOL. More recently, we are implanting pinhole optic IOLs (the IC-8 IOL from AcuFocus) in these eyes and the results are outstanding, with the pinhole reducing much of the corneal higher order aberrations that lead to starburst, halos and glare. The pinhole IOL is also more forgiving in terms of refractive accuracy due to the increased depth of focus provided by the pinhole.
Patient undergoing CXL treatment
The diagnosis has become more objective too with devices like the iTrace and the HD Analyzer being able to illustrate the optical contribution from the cornea and from the cataract, making it simpler to plan surgery. Should the cataract be treated first, or should the cornea be treated first? Could they be treated at the same surgical procedure?
Today and the near future
Corneal regularisation may soon be achieved by tissue addition rather than tissue subtraction as we currently do (excimer laser ablation by means of photo refractive keratectomy (PRK)). Allotex Ltd is a company providing excimer laser shaped human corneal lenticules for refractive use. This allows tissue with 0.25-micron accuracy to be used for corneal addition procedures. Clinical trials, expected to commence in Q3 of this year in eight European sites including the Wellington Eye Clinic in Dublin for presbyopia and hyperopia, are expected to prove the value of this technique for regular corneas and lay the foundation for the use of allograft onlays and inlays for keratoconic corneas. As corneal surgeons, adding thickness to a keratoconic cornea resonates well. With improved corneal regularity, IOL power calculations become more predictable.
However, with keratoconus the posterior corneal surface can also be distorted and current IOL power formulae do not account for this. Refractive surprises are therefore not uncommon. This is where the RxSight Light Adjustable Lens (RxLAL) may play a significant role in improving outcomes. We are currently enrolling eyes in a four-site European study on using this IOL that can be adjusted using UV light after it has been implanted in the eye and allowed time to settle into its final effective lens position (ELP). ELP has always been blamed for missing refractive targets as we have found it challenging to predict the healing and contraction of the capsular bag and its effect on the final IOL position within the eye. With the RxLAL, this no longer matters. Once the IOL has stabilised within the eye, the IOL power is adjusted using a light delivery device (LDD) that can change the power of the IOL to achieve a desired refractive outcome. Incredibly, early results show the accuracy and predictability even supersede that of LASIK. The IOL power can be adjusted up to three times and then ‘locked-in’ with a final treatment after which no further adjustments can occur.
This case study shows how in the relatively short time-frame, that something regarded as radical and innovative only 11 years ago, has evolved in a short time to be potentially replaced by fundamentally different approaches that have led to increased safety, increased predictability and ultimately, increased patient satisfaction.
In the interests of brevity certain further innovations were deliberately omitted, but it is worthwhile mentioning that femtosecond laser innovation is set to further disrupt the current cataract techniques where phaco is used. Within the next 12 months we are commencing a clinical trial where phaco is no longer required following femtosecond laser fragmentation of the cataract.
New drugs are in the pipeline whereby retinal dosages of some pharmacologic agents can be achieved with topical application of drops rather than intravitreal injections.
Innovation is alive and well and ophthalmology has proven to be a fitting partner for our engineering and physics PhD colleagues to apply their considerable talents. It would be wonderful, however, if time could slow down just a tad.
Mr Arthur B Cummings, Consultant Ophthalmic Surgeon, Wellington Eye Clinic and Beacon Hospital, Dublin
Leave a Reply
You must be logged in to post a comment.