The Cachet lens is a new flexible phakic lens implant designed to correct higher degrees of myopia from -6 to -16.5 D. The current design does not correct astigmatism.
Since the range of optical defects correctable by the Cachet lens overlaps with that which can be achieved with LASIK, or with Artisan, Artiflex, or Implantable Contact Lens (ICL) surgery, for some people there may be a choice between the treatments, decided upon by the following factors:
Easily adjusted optical outcome and generally effective correction of astigmatism.
Cheaper than Cachet lens surgery.
LASIK may be contra-indicated if the cornea is too thin, or if there are topographic signs suggestive of keratoconus.
LASIK causes irreversible changes to the corneal structure, and if too much corneal tissue is removed the cornea may undergo ectasia leading to poor vision and loss of correction.
The quality of the optical correction with LASIK may sometimes not be as good as that achieved by a Cachet lens, especially in high degrees of myopia. This is because the final optical surface created can be less regular than that of a manufactured lens, due to variables in the surgical procedure and the wound healing process.
If needed, fitting of contact lenses may be difficult post-operatively, due to the irregular shape of the cornea.
Cachet advantages :
Good quality correction of spherical optical defects.
No change in ease of contact lens correction post-operatively, should this is needed.
Possibility of adjustment or correction of final optical outcome by LASIK surgery (Bioptics).
Intraocular lens implantation carries an extremely small but unavoidable risk of introduction of infection into the eye. This is a very serious complication which can lead not only to loss of vision, but even to loss of the eye.
Intraocular surgery also carries the risk of damage to other structures in the eye, such as the lens, the iris, and the trabecular meshwork, giving potential complications of cataract, glaucoma, iritis, and also possible retinal complications such as cystoid macular oedema and retinal detachment.
Intraocular surgery causes some irreversible loss of corneal endothelial cells. Loss of these cells diminishes the functional reserve of the cornea, and could ultimately contribute to corneal failure due to endothelial cell depletion.
Because of the close proximity of the Cachet lens to the cornea, corneal complications may possibly be more frequent than with ICL implantation. The optical outcome may not be accurate, and can only be adjusted by replacement of the Cachet lens or additional surgery such as LASIK.
The quality of vision obtained in low light conditions may be poor if the size of the dilated pupil exceeds the size of the optical portion of the Cachet lens.
Previous designs of angle-supported phakic intra-ocular lenses have been sometimes complicated by distortion of the pupil shape (ovalling), but this does not appear to be a significant problem with the cachet so far.
Since the long-term acceptability of Cachet lenses has not been established, there remains the possibility that lenses implanted in young adults now, will need to be surgically removed at some point in the future, and such further surgery would add to the risk of potential complications.
Because of the risk of complications such as glaucoma, insertion of a Cachet lens makes regular long term follow-up advisable.
The presence of the Cachet lens may be noted on close inspection of the eye, and reflections from the surface of the optic can be seen under certain lighting conditions.
Cachet surgery is more expensive than LASIK.
Cachet Lens Surgery
The insertion of the Cachet lens is carried out with either local or general anaesthetic. In a local anaesthetic, drops are put into the eye to constrict the pupil and anaesthetise the cornea. A 2.6 mm incision is made at the edge of the cornea, and the lens is inserted into the eye and carefully positioned.
Since the surgical incision is small it is usually self sealing, so no sutures are required. After the operation antibiotic drops are given to help prevent infection, and steroid drops to suppress inflammation. Visual recovery is rapid, with functional vision virtually straight away and stabilisation of refraction after some weeks.