IN THE NAME OF GOD

 Dr. Memarzadeh Ophthalmologist 1389

 = alter refr state of eye => enable px to see without visual aids  refr surgery divided into FOUR major areas: ◦ 1. INCISIONAL TECHNIQUES ◦ 2. INTRAOCULAR LENSES ◦ 3. THERMAL TECHNIQUES ◦ 4. LAMELLAR PROCEDURES

 Conductive keratoplasty is a non-ablative, non-lamellar technique in which low radiofrequency energy (350 kHz) is applied with a probe tip to the peripheral corneal stroma.  A full circle of CK spots applied to the corneal mid-periphery causes peripheral flattening and central steepening, inducing a myopic shift. The effect of CK is determined by the number of spot (8, 16 or 24) and the optical zone of the treatment (6 mm, 7 mm, and/or 8 mm).   With the “Firm-Pressure” technique, the energy is delivered after the Keratoplast™ tip is inserted into the cornea with some pressure applied.  Recently, a “Light-Touch” technique was introduced, in which the pressure is released before applying the energy. Theoretical advantages of this technique include higher corrections, larger optical zone and possibly smaller amount of induced astigmatism.

 Eg. THERMOKERATOPLASTY:  involves creation of two sets of 8 spot burns using holmium YAG laser - in ring pattern - peripheral cornea  Heat => coagulation - up to 90% of corneal depth  Coagulation => collagen shrinkage in periphery => generalised central steepening => correct hyperopia (up to +2.50D

 Thermokeratoplasty : Consists of heating the cornea to shrink the peripheral and paracentral stromal collagen to produce a peripheral flattening and a central steepening of the cornea to treat HYPEROPIA. Solid state infrared lasers, such as the holmium:yttrium,aluminum, and garnet (Ho:YAG ) laser of nm,have been used in a peripheral intrastromal radial pattern ( Laser Thermokeratoplasty ), to treat hyperopia of 2.50D.and less.

 7) Another form of thermokeratoplasty is the so called ( Conductive Keratoplasty ) which used a handheld radiofrequency probe to shrink the peripheral collagen.  The shrinkage temperature of the corneal collagen is between degrees.  Despite the instability of corrections and regressions, laser thermokeratoplasty and conductive keratoplasty have the major advantage of untouched the central cornea.

 Electromagnetic Spectrum

The CK probe (displayed next to a 10-0 nylon suture for comparison) consists of a thin conductive wire, 450µ long and 90 µm wide.

CONDUCTIVE KERATOPLASTY:  A probe touches the cornea with High Radiofrequency and by collagen shrinkage reshapes the cornea.  Produces controlled monovision inducing Myopia  Only suitable for Hyperopes  FDA approved as Monovision Blended Vision  Rapid loss of effect is the main problem  Its use has decreased in the last years.

During conductive keratoplasty, the eye surgeon will topically anesthetize the eye and then insert a speculum to hold the eye open. The surgeon will then use a thin tipped, pen-like instrument to draw small circles around the cornea with radio waves, or radiofrequency (RF) energy. This energy creates a mild heat that shrinks the peripheral corneal collagen into a tight band. This reshapes the curvature of the cornea, making it a steeper angle. The new curvature allows light to be bent more drastically as it enters the eye so that the patient can focus at a shorter distance.speculum

 Another form of thermokeratoplasty is the so called ( Conductive Keratoplasty ) which used a handheld radiofrequency probe to shrink the peripheral collagen.  The shrinkage temperature of the corneal collagen is between degrees.  Despite the instability of corrections and regressions, laser thermokeratoplasty and conductive keratoplasty have the major advantage of untouched the central cornea.

 Thermokeratoplasty : Consists of heating the cornea to shrink the peripheral and paracentral stromal collagen to produce a peripheral flattening and a central steepening of the cornea to treat HYPEROPIA . Solid state infrared lasers, such as the holmium:yttrium,aluminum, and garnet (Ho:YAG ) laser of nm,have been used in a peripheral intrastromal radial pattern ( Laser Thermokeratoplasty ), to treat hyperopia of 2.50D.and less.

 Conductive keratoplasty is a non-ablative, non-lamellar technique in which low radiofrequency energy (350 kHz) is applied with a probe tip to the peripheral corneal stroma.   A full circle of CK spots applied to the corneal mid-periphery causes peripheral flattening and central steepening, inducing a myopic shift. The effect of CK is determined by the number of spot (8, 16, 24 32) and the optical zone of the treatment (6 mm, 7 mm, and/or 8 mm).   With the “Firm-Pressure” technique, the energy is delivered after the Keratoplast™ tip is inserted into the cornea with some pressure applied.   Recently, a “Light-Touch” technique was introduced, in which the pressure is released before applying the energy. Theoretical advantages of this technique include higher corrections, larger optical zone and possibly smaller amount of induced astigmatism.

 Scheimpflug images of different areas of the same cornea demonstrating adjacent CK spots (arrows) that extend approximately 80%  to 90% of stromal thickness in this eye 1 year following surgery

The Food and Drug Administration (FDA) approved conductive keratoplasty for use in 2002; first only for patients over forty with farsightedness, and later for patients with presbyopia. Unlike hyperopic patients, CK patients with presbyopia only have one eye treated and leave the dominant eye untreated. The untreated eye may then focus on greater distances, while the treated eye can focus on objects at close range. For this reason, conductive keratoplasty is often preferred to glasses or contact lenses because it is less likely to impair distance vision. The procedure for presbyopia may not be the best option for all patients, so doctors will often examine the patient beforehand with single lenses over the non-dominant eye to test if vision remains clear at distances.FDA

 Treatment range (+1.00 to +2.25D) ◦ 16 and 24 spot patterns ◦ Conventional Pressure  Myopic target (-1.00 to -2.00D) ◦ non-dominant eye for monovision

 Dominance testing : A) Both eyes are focused on the 20/400 E while holding the dominance card at arm’s length. B) The dominance card is centered just below the 20/400 E. C) The patient raises the dominance card to perfectly center the “E” in the middle of the hole in the card. D) The patient then moves the, card towards his/her face while keeping the “E” in the center of the hole

Ways CK Has Been Used in Keratoconus 1. Previously, CK has been used to steepen the flat meridian (Boxer Wachler 1 ) [place CK spots in flat area] More recently, [place CK spots in most elevated area] 2. To shrink and “centralize” the cone (Hardten 2 ) [place CK spots in most elevated area] 3. The method described here shrinks and centralizes the cone under keratometric guidance 1.Personal communication 2.Personal communication

Patients and Methods Data was collected retrospectively from 30 eyes of 30 patients, 46 years of age or older, with plano to diopters (D) of hyperopia and ≤ D of cylinder treated with CK with a target refraction of up to D. Patients were treated during the learning curve phase of firm-pressure CK (8 to 24 spots; Group 1; n=20) and light-pressure CK (8 to 16 spots; Group 2; n=10). All procedures were performed with the ViewPoint CK System (Refractec, Inc.) by the same surgeon (DTA) at the Massachusetts Eye and Ear Infirmary. In Group 1 all patients completed 6 months follow-up. Three patients were retreated between 6 months and 1 year. In Group 2, two patients were retreated before the 6-month visit and were excluded from analysis. Firm Touch X Light Touch CK Nomograms SpotsDiameterFirm Pressure D 166 & D 246, 7 & D SpotsDiameterNeutral Pressure D D 167 & D

Thanks for attention attention