ICL (Intraocular Collamer Lens)
The implantable collamer lens (ICL) is a lens designed to rest in front of the natural human lens of the eye floating on an aqueous layer. This lens is called the VISIAN EVO+ ICL and is made of an advanced collamer lens material that is highly biocompatible with the eye. It is a co-polymerisation product of hydrophobic and hydrophilic acrylic material polymerised with telo-collagen. It has excellent UV blocking incorporated, is soft and elastic allowing gentle implantation by the surgeon. The lens is not normally felt by the recipient when implanted within the eye.
The lens has a low refractive index, so it does not back reflect or glint and is normally invisible to an observer.
The ICL has been in use since 1993 and over the past 31 years there has been improvement in manufacturing technology and design, so the current model has a much bigger optical zone than previously, which helps night vision.
The ICL is available up to -18.0 D with up to 6 Dioptres of astigmatism. For eyes with more extreme refractive error and optical distortions limiting vision it is possible to perform a wavefront-guided excimer laser custom treatment to treat residual refractive error. This is termed “bioptics”.
The ICL lens design features the “KS-Aquaport”, which is a small central hole in the lens optic that facilitates aqueous flow and eliminates the need to make a small hole in the iris (iridectomy). This has minimised or eliminated risk of aqueous flow blockage and appears to prevent anterior cataract development which could previously occur with phakic lens implants. The central drainage hole can induce early halos and glare, but in 95% of cases, they reduce significantly or disappear in the first 3 to 6 months after implantation. There are some people who still see haloes after ICL implantation when the pupil is very large at night, and this is due to some light coming into the eye around the edge of the ICL lens.
The ICL is preferred over corneal excimer laser eye surgery (PRK or LASIK) or SMILE where there is higher refractive error. It is also favoured where there is significant dry eye or where there is a thin or irregular cornea and laser eye correction may be contraindicated.
The ICL can reduce or eliminate total dependence on glasses or contact lenses. ICL and wavefront-guided surface treatment or LASIK all have the potential to provide very high quality of vision. Generally, the bigger the intended treatment the more the ICL is favoured. An alternative is to continue to use glasses or contact lenses.
ICL vision correction is becoming increasingly popular and there have been over 2 million ICL lenses implanted worldwide.
The ICL lens is low refractive index and is transparent
ICL Information 2022
Corneal cross linking
Corneal collagen cross linking (CXL) has been developed over the last 15 years. The procedure aims to strengthen the cornea of the eye by application of vitamin B2 (riboflavin), followed by treatment with ultraviolet A (UV-A) light.
This procedure is often recommended when the cornea needs strengthening; especially for the treatment of keratoconus, or where there is an unstable cornea.
How does corneal cross linking work?
Corneal cross linking works by increasing the number of bonds between collagen fibres. It can be performed as a staged procedure with wavefront-guided LASEK (surface excimer laser treatment). After cross linking the corneal shape can improve with a significant increase in mechanical stiffness of the cornea.
The cross linking procedure
Prior to treatment corneal scans are performed to measure the contour and thickness.
You lie down on a flat bed, and after applying topical anaesthetic drops, the corneal epithelium is partially scored using a special instrument.
Riboflavin drops are then applied until the cornea is yellow coloured (due to the Riboflavin).
Using an Avedro™ cross-linking system ultraviolet light (UVA) is applied at 365 nm wavelength, for between 8 to 30 minutes. A calibrated UVA light source is used.
At the end of the procedure, a medical contact lens is placed over the cornea and this is removed in the clinic after three days.
Possible complications
Mr Stevens has an excellent track record for achieving a very low complication rate with his surgery. However all procedures carry some risk.
When performed by a skilled surgeon with modern equipment, corneal cross-linking has a low risk of serious complication. Possible complications include prolonged healing of the corneal epithelium with delayed recovery of vision, corneal stromal scarring or melting and failure of the cross-linking to increase corneal strength and stability. Overall the risk to benefit ratio for cross-linking is generally considered good and cross-linking should be considered where there is weakening of the cornea and progression of warpage.
Lesser but common issues may include some degree of dry eye or blepharitis (irritation of the eyelids) in the healing period.
There is some degree of unpredictability in outcome as with any corneal surgery. You should read all the information given to you about possible complications before undergoing any treatment.
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Riboflavin (Vitamin B2)
Photo therapeutic keratectomy (PTK)
Photo Therapeutic Keratectomy (PTK) is when surface excimer laser treatment is used to treat a medical corneal condition or corneal irregularity.
A PTK procedure is often used to treat loose corneal epithelium (corneal erosion, recurrent erosion syndrome), corneal scars, injury or irregularity.
Treatment technique
PTK may be an entirely manual treatment, based on the skill and experience of the surgeon. Alternatively, it may be a customised wavefront-guided or corneal topography-guided laser treatment.
Individual advice
PTK is sometimes performed as a staged series of procedures improving corneal contour and the refractive state (your vision). Since each treatment is tailored to the individual eye and condition, specific advice is given on an individual basis.
Possible complications
Mr Stevens has an excellent track record for achieving a very low complication rate with his surgery. However all procedures carry some risk.
PTK treatment can range from a simple procedure to highly complex treatment involving manual and wavefront-guided treatments, staged over time. Possible complications are then similar to surface excimer laser treatment (LASEK), but for complex PTK the main issue is unpredictability.
Lesser but common issues may include some degree of dry eye or blepharitis (irritation of the eyelids) in the healing period.
Corneal transplantation
As a specialist corneal surgeon, Mr Stevens performs corneal transplantation, including femtosecond laser lamellar and penetrating keratoplasty corneal transplantation, which he performs at Moorfields Eye Hospital.