IntraStromal Lens (ISL)

ntrastromal lenses are so-called alloplastic implants which are placed into the cornea approximately 50% of the way down. These are usually done by first removing a portion of the cornea with a device called a microkeratome (see MKM). The power of the implant is tailored to the patient's refractive error. The inlay is then laid in place and the tissue removed is sutured back into place. Sometimes a pocket is dissected into the corneal stroma and the lens placed that way.

None of these procedures using various plastics were wholly successful. The hydrogel implant gave the most promise. To the author's knowledge, few, if any, of these procedures are currently being performed today.

KeratoGel^TM stromal implants

A soft hydrophilic plastic material, similar to that of soft contact lenses, has been employed to correct aphakia. Not all patients who need cataract extractions can have, or get, intraocular lens implants. The patient may have diabetes or glaucoma or have some other problem making such an implant risky. In the past, these patients were forced to wear contact lenses (which may be impossible for an arthritic or one- eyed individual) or thick glasses which distort vision. It is possible to implant a lens into the corneal stroma to provide the benefits of the IOL implant. This device was under investigation and implanted by the Bores Eye Institute and a few other facilities in the U.S. but the study has been suspended.

References

1. Werblin TP, Patel AS, Barraquer JI: Initial human experience with Permalens myopic hydrogel intracorneal lens implants. Refract Corneal Surg 8(1):23-6, 1992.
2. Werblin TP, Peiffer RL, Binder PS, McCarey BE, Patel AS: Eight years experience with Permalens intracorneal lenses in nonhuman primates. Refract Corneal Surg 8(1):12-22, 1992.
3. Werblin TP, Blaydes JE, Fryczkowski A, Peiffer R: Refractive corneal surgery: the use of implantable alloplastic lens material. Aust J Ophthalmol 11(4):325-331, 1983.
4. Werblin TP, Blaydes JE, Fryczkowski AW, Peiffer R: Stability of hydrogel intracorneal implants in non-human primates. CLAO J 9(2):157-61, 1983.
5. Werblin TP, Fryczkowski AW, Peiffer RL: Myopic correction using alloplastic implants in non-human primates--a preliminary report. Ann Ophthalmol 16(12):1127-30, 1984.
6. Werblin TP, Peiffer RL, Fryczkowski A: Myopic hydrogel keratophakia: preliminary report. Cornea 3(3):197-204, 1984.
7. Werblin TP, Fryczkowski AW, Peiffer RL: Hydrogel keratophakia: measurement of intraocular pressure. CLAO J 11(4):354-7, 1985.
8. Peiffer RL, Werblin TP, Fryczkowski AW: Pathology of corneal hydrogel alloplastic implants. Ophthalmol 92:1294-1304, 1985.

Intracorneal Ring (ICR)

This is a stromal alloplastic implant using a clear flexible ring. This ring is implanted using a special device which produces a tunnel within the corneal stroma at a preset depth. The ring, which has an oval cross-section, is threaded into this tunnel and its ends sutured together. The amount of refractive correction is determined by the thickness of the cross-section of the ring material. This is an experimental procedure which shows great promise. It has some obvious advantages: the central visual zone is undisturbed; it is easy to remove and/or replace; it sometimes produces a multifocal surface which provides both improved near and distance vision.

References

Keratophakia (KP)

Keratophakia uses a so-called homoplastic implant which is placed into the cornea approximately 50% of the way down. These are usually done by first preparing a lens from corneal donor tissue using a cryo-lathe. They are implanted by removing a portion of the cornea with a device called a microkeratome (see MKM). The inlay is then laid in place and the tissue removed is sutured back into place. Sometimes a pocket is dissected into the corneal stroma and the lens placed that way.

References

1. Friedlander MH, Rich LF, Werblin TP, Kaufman HE, Granet N: Keratophakia using preserved lenticules. Ophthalmology 87 (7):687-92, 1980.