Hyperopia and Presbyopia - part 4 pdf

Hyperopia correction bynoncontact holmium: YAG laser thermal keratoplasty.. Treatment of hyperopia with contactHo:YAG laser thermal keratoplasty.. Hyperopia correction by tact holmium:YA

corneal thickness Clinical studies have established the safety and efficacy of Ho:YAGLTK up to 2 years after treatment LTK may also be used to treat PRK and LASIK-induced hyperopia Diode lasers may help further improve stability of refractive effectwith LTK Wavefront-guided LTK may further improve the predictability of this procedureand allow for predictable outcomes even for retreatments of initial undercorrections.

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re-21 Seiler T, Matallana M, Bende T Laser themokeratoplasty by means of a pulsed holmium:YAGlaser for hyperopic correction J Refract Corneal Surg 1990; 6:335–339

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to CO2laser radiation Exp Eye Res 1983; 37:543–550

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30 Koch DD, Berry MJ, Vassiliadis A Non-contact holmium:YAG laser thermal keratoplasty.In: Salz JJ, ed Corneal Laser Surgery Philadelphia: Mosby-Year Book, 1994:247–254

31 Alio´ JL, Pe´rez-Santonja JJ Correction of hyperopia by laser thermokeratoplasty (LTK) In:Agarwal S, Agarwal A, Pallikaris IG, Neuhann TH, Knorz MC, Agarwal A, eds RefractiveSurgery New Delhi: Jaypee, 2000:583–591

32 Cavanaugh TB, Durrie DS Holmium YAG laser thermokeratoplasty: synopsis of clinicalexperience Semin Ophthalmol 1994; 9(2):110–116

33 Koch DD, Kohnen T, McDonnell PJ, Menefee RF, AAS, Berry MJ Hyperopia correction bynoncontact holmium: YAG laser thermal keratoplasty United States phase IIA clinical studywith a 1-year follow-up Ophthalmology 1996; 103(10):1525–1535

34 Tutton MK, Cherry PM Holmium:YAG laser thermokeratoplasty to correct hyperopia: twoyears follow-up Ophthalm Surg Lasers 1996; 27(5 suppl):S521–S524

35 Eggink CA, Bardak Y, Cuypers MHM, Deutman AF Treatment of hyperopia with contactHo:YAG laser thermal keratoplasty J Refract Surg 1999; 15(1):16–22

36 Lim KH, Kim WJ, Wee WR, Shin DE, Lee JH, Chang BL Holmium: YAG laser toplasty for astigmatism in rabbits J Refract Surg 1996; 12(1):190–193

thermokera-37 Hennekes R Holmium:YAG laser thermokeratoplasty for correction of astigmatism J RefractSurg 1995; 11(3 suppl):S358-S360

38 Thompson V Holmium: YAG laser thermokeratoplasty for correction of astigmatism J RefractCorneal Surg 1994; 10:S293

39 Ariyasu RG, Sand B, Menefee R, AAS, Hennings D, Rose C, Berry M, Garbus JJ, McDonnell

PJ Holmium laser themokeratoplasty of 10 poorly sighted eyes J Refract Surg 1995; 11:358–365

40 Koch DD, Kohnen T, McDonnell PJ, Menefee RF, Berry MJ Hyperopia correction by tact holmium:YAG laser thermal keratoplasty United States phase IIA clinical study with a1-year follow-up Ophthalmology 1996; 103(10):1525–1535

noncon-41 Kohnen T, Husain SE, Koch DD Corneal topographic changes after noncontact holmium:YAGlaser thermal keratoplasty to correct hyperopia J Cataract Refract Surg 1996; 22:427–435

42 Koch DD, Abarca A, Villarreal R, Menefee R, AAS, Kohnen T, Vassiliadis A, Berry M.Hyperopia correction by noncontact holmium:YAG laser thermal keratoplasty Clinical studywith two-year follow-up Ophthalmology 1997; 104(11):1938–1947

43 Kohnen T, Koch DD, McDonnell PJ, Menefee RF, Berry MJ Noncontact holmium:YAG laserthermal keratoplasty to correct hyperopia: 18-month follow-up Ophthalmologica 1997; 211:274–282

44 Vinciguerra P, Kohnen T, Azzolini M, Radice P, Epstein D, Koch DD Radial and staggeredtreatment patterns to correct hyperopia using noncontact holmium:YAG laser thermal kera-toplasty J Cataract Refract Surg 1998; 24:21–30

45 Koch DD, Kohnen T, Anderson JA, Binder PS, Moore MN, Menefee RF, AAS, Valderamma

GL, Berry MJ Histologic changes and wound healing response following 10-pulse noncontactholmium:YAG laser thermal keratoplasty J Refract Surg 1996; 12:623–634

46 Kohnen T, Villarreal V, R, Menefee R, Berry M, Koch DD Hyperopia correction by noncontactholmium:YAG laser thermal keratoplasty: five-pulse treatments with 1 year follow-up GraefesArch Clin Exp Ophthalmol 1997; 235:702–708

47 Alio´ JL, Ismail MM, Sanchez Pego JL Correction of hyperopia with non-contact Ho:YAGlaser thermal keratoplasty J Refract Surg 1997; 13(1):17–22

48 Gezer A The role of patient’s age in regression of holmium:YAG thermokeratoplasty-inducedcorrection of hyperopia Eur J Ophthalmol 1997; 7(2):139–143

49 Nano HD, Muzzin S Noncontact holmium:YAG laser thermal keratoplasty for hyperopia JCataract Refract Surg 1998; 24:751–757

50 Aker AB, Brown DC Hyperion laser thermokeratoplasty for hyperopia Int Ophthalmol Clin2000; 40(3):165–181

51 Portellinha W, Nakano K, Oliveira M, Simoceli R Laser in situ keratomileusis for hyperopiaafter thermal keratoplasty J Refract Surg 1999; 15(2 suppl):S218–S220

52 Attia W, Pe´rez-Santonja JJ, Alio´ JL Laser in situ keratomileusis for recurrent hyperopiafollowing laser thermal keratoplasty J Refract Surg 2000; 16:163–169

53 Pop M Laser thermal keratoplasty for the treatment of photorefractive keratectomy tions: a 1-year follow-up Ophthalmology 1998; 105(5):926–931

overcorrec-54 Alio´ JL, Ismail MM, Artola A, Pe´rez-Santonja JJ Correction of hyperopia induced by fractive keratectomy using non-contact Ho:YAG laser thermal keratoplasty J Refract Surg1997; 13:13–16

photore-55 Eggink CA, Meurs P, Bardak Y, Deutman AF Holmium laser thermal keratoplasty for opia and astigmatism after photorefractive keratectomy J Refract Surg 2000; 16:317–322

hyper-56 Goggin M, Lavery F Holmium laser thermokeratoplasty for the reversal of hyperopia aftermyopic photorefractive keratectomy Br J Ophthalmol 1997; 81:541–543

57 Pe´rez-Santonja JJ, Bellot J, Claramonte P, Ismail MM, Alio´ JL Laser-in-situ keratomileusis

to correct high myopia J Cataract Refract Surg 1997; 23:372–385

58 Ismail MM, Alio´ JL, Pe´rez-Santonja JJ Noncontact thermokeratoplasty to correct hyperopiainduced by laser-in-situ keratomileusis J Cataract Refract Surg 1998; 24:1191–1194

59 Bende T, Jean B, Oltrup T Laser thermal keratoplasty using a continuous wave diode laser

J Refract Surg 1999; 15:154–158

60 Brinkmann R, Koop N, Geerling G, Kampmeier J, Borcherding S, Kamm K, Birngruber R.Diode laser thermokeratoplasty: application strategy and dosimetry J Cataract Refract Surg1998; 24(9):1195–1207

61 Koop N, Wirbelauer C, Tu¨ngler A, Geerling G, Bastian GO, Brinkmann R Thermal damage

to the corneal endothelium in diode laser thermokeratoplasty Ophthalmologe 1999; 96(6):392–397

62 Wirbelauer C, Koop N, Tu¨ngler A, Geerling G, Birngruber R, Laqua H, Brinkmann R Cornealendothelial cell damage after experimental diode laser thermal keratoplasty J Refract Surg2000; 16:323–329

63 Geerling G, Koop N, Brinkmann R, Tu¨ngler A, Cand med.m, Wirbelauer C, Birngruber R,Laqua H Continuous-wave diode laser thermokeratoplasty: first clinical experience in blindhuman eyes J Cataract Refract Surg 1999; 25:32–40

Conductive Keratoplasty for the Correction of Low to Moderate

Tulane University School of Medicine, New Orleans, Louisiana, U.S.A.

A HYPEROPIA CORRECTION BY CONDUCTIVE KERATOPLASTY

1 Thermokeratoplasty Procedures

Surgical correction of hyperopia has been a greater challenge to ophthalmology than thecorrection of myopia Attempts to steepen the central cornea by non-ablative methods,such as thermal keratoplasty, date back to the rabbit studies by Lans in the nineteenthcentury During the 1980s, hot-wire thermokeratoplasty, a technique developed in the

95

Soviet Union, was used to produce thermal burns (up to 600⬚C) that penetrated to 95%

of corneal depth (1) Studies showed substantial overcorrection followed by marked sion (2–4) Evaluation of the procedure through well-designed clinical trials before adop-tion and dissemination was recommended (5)

regres-The failure of high-temperature probes to produce a stable, predictable, and safehyperopic correction led to the investigation of other modalities of thermal keratoplasty,including contact holmium: YAG laser thermal keratoplasty (Holmium 25, Technomed,Baesweiler, Germany) (6–8), pulsed, noncontact holmium:YAG laser keratoplasty (non-contact LTK, Hyperion System, Sunrise Technologies, Fremont, CA) (9–18), continuous-wave diode laser thermokeratoplasty (DTK, Rodenstock, ProLaser Medical Systems, Inc.,Dusseldorf, Germany) (19–20), and radiofrequency-based conductive keratoplasty (CK)(Refractec, Inc., Irvine, CA) (21) These techniques have been more successful than theoriginal hot-needle technique, although regression and induction of astigmatism have con-tinued to be concerns with some techniques

In addition to thermokeratoplasty procedures, ablative methods, such as tive keratectomy (PRK) (22–27) and laser in situ keratomileusis (LASIK) (28–34), havebeen used to correct hyperopia Generally, attempted hyperopia corrections with thesemethods have been higher (⬎3.00 D) than the range recommended for CK

photorefrac-2 Conductive Keratoplasty: The Mechanism

The conductive keratoplasty procedure performed with the ViewPoint CK System (Fig.1) is designed to treat spherical, previously untreated hyperopia of 0.75 to 3.00 D Treat-ment of astigmatism, presbyopia, and over- or undercorrections following LASIK or otherrefractive procedures are other potential applications

Conductive keratoplasty delivers low-energy, high-frequency (radiofrequency, 350kHz) current directly into the corneal stroma by means of a Keratoplast tip inserted intothe peripheral cornea at eight or more treatment points (Fig 2) Collagen within the targetedtreatment zone is heated in a gentle, controlled fashion as a result of the natural resistance

of stromal tissue to the flow of the current (35) Because resistance to the flow of the

Figure 1 The ViewPoint Conductive Keratoplasty (CK) System: console, probe, and specula

Figure 2 The CK Keratoplast tip shown next to a 7–0 suture (Courtesy of Refractec, Inc., Irvine,CA.)

current increases with increasing dehydration of collagen, the process tends to be limiting A thermal model predicts a cylindrical footprint approximately 150 to 200␮mwide by 500␮m deep that extends to approximately 80% of the depth of the mid-peripheralcornea at each treated spot (36) Striae form between the treated spots, creating a band

self-of tightening that increases the curvature self-of the central cornea, thereby decreasing opia The Hyperion noncontact LTK technique, on the other hand, applies heat directly

hyper-to the surface of the cornea, heating tissue in a gradient, and generates a conical footprint(10)

B THE CONDUCTIVE KERATOPLASTY PROCEDURE

1 The Conductive Keratoplasty Device

The Viewpoint CK system consists of a radiofrequency energy-generating console, a held, reusable, pen-shaped handpiece attached by a removable cable and connector, aspeculum (choice of two, Lancaster or Barraquer) that provides a large surface for anelectrical return path, and a pedal that controls release of radiofrequency energy Attached

hand-to the handpiece is the Kerahand-toplast tip, a single-use, disposable, stainless steel penetratingtip, 90␮m in diameter and 450 ␮m long, that delivers the current directly to the cornealstroma At the very distal portion of the tip is a Teflon-coated stainless-steel stop thatassures correct depth of penetration

2 Patient Selection

a Suitable Patients

Patients suitable for treatment with the Viewpoint CK System should have 0.75 to 3.00

D of spherical hyperopia andⱕ0.75 D of refractive astigmatism Visual acuity should becorrectable to at least 20/40 in both eyes Hard or rigid gas-permeable lenses should be

discontinued for at least 3 weeks and soft lenses for at least 2 weeks prior to the preoperativeevaluation Wearers of hard contact lenses should have two central keratometry readingsand two manifest refractions taken at least 1 week apart The manifest refraction measure-ments must not differ from the earlier measurements by more than 0.50 D in either merid-ian Keratometry mires must be regular.

b Unsuitable Patients

Patients with a peripheral pachymetry reading at the 6-mm optical zone of less than 560

␮m are not suitable for treatment with the Viewpoint CK System Also unsuitable arethose who have had strabismus surgery; have anterior segment pathology; have residual,recurrent, active ocular or uncontrolled eyelid disease or any corneal abnormality; or havesigns of progressive or unstable hyperopia Other relative contraindications are a history

of herpes zoster keratitis, herpes simplex keratitis, glaucoma, a history of sive rise in intraocular pressure (IOP), a preoperative IOP⬎21 mmHg, or narrow angles.Patients with diabetes, diagnosed autoimmune disease, connective tissue disease, an immu-nocompromised state, current treatment with chronic systemic corticosteroid or other im-munosuppressive therapy that may affect wound healing; a history of keloid formation;intractable keratoconjunctivitis sicca; or pregnancy are also contraindicated to receive the

steroid-respon-CK treatment

3 Examinations

Preoperative examinations should include a manifest and cycloplegic refraction, an rected and best spectacle-corrected visual acuity (distance and near), a slit-lamp and fun-doscopic examination, applanation tonometry, central keratometry, ultrasonic pachymetry,and computed corneal topography

uncor-4 Performing the CK Procedure

Correct the patient’s full cycloplegic spectacle refraction Administer one drop of topicalanesthetic three times at 5-min intervals and monitor the patient for degree of anesthesia

Do not use pilocarpine Insert the CK lid speculum to provide corneal exposure and act

as an electrical return path Do not use a lid drape, for it may prevent direct contact ofthe lid speculum and eyelid, which would disrupt the electrical current return path Tapethe fellow eye closed Position the operating microscope or slit-lamp biomicroscope over

or in front of the eye to be treated

Mark the cornea with the CK marker, and remind the patient to fixate on the lightfrom the microscope Dampen the CK marker with gentian violet or rose bengal stain.Center the marker’s cross hairs over the center of the pupil and apply light pressure onthe marker to make a circular mark with eight intersections on the cornea If using gentianviolet, irrigate with balanced salt solution to remove excess ink Dry the surface of thecornea thoroughly with a fiber-free sponge to avoid dissipation of applied energy by awet surface

Set the appropriate treatment parameters on the console according to the nomogram(Table 1) The default setting for treatment is 350 kHz, 60% power (0.6 W) for 0.6 s.Inspect the Keratoplast tip under the microscope to ensure it is not damaged or bent prior

to application When treating 0.75 to 0.875 D of hyperopia (eight spots), treat only at the7-mm optical zone, beginning treatment at the 12 o’clock position and continuing in thesequence shown in Figure 3 When treating higher levels of hyperopia, follow the nomo-

Table 1 Conductive Keratoplasty Nomogram

to 2.25 D, apply treatment at the 6-, 7-, and 8-mm optical zones for a total of 24 spots.For treating 2.375 D to 3.00 D, apply treatment to the 6-, 7-, and 8-mm optical zones andthen to each of the eight sectors between the previously treated spots at the 7-mm opticalzone for a total of 32 spots

To treat each spot, place the tip of the delivery probe at the treatment mark on thecornea, perpendicular to the corneal surface Apply light pressure until the tip penetratesthe cornea down to the insulator stop Depress the foot pedal to apply the radio frequencyenergy A tone will sound as the energy is applied At each treatment spot, keep the tip

in place until the preprogrammed treatment time has been completed (the tone stops).Clean the tip with a fiber-free sponge after each treatment spot to remove any tissue debris,

Figure 3 Number, location, and sequence of treatment spots (Courtesy of Refractec, Inc., Irvine,CA.)

taking care not to damage the tip Perform intraoperative keratometry after completingthe full circle of treatments to check for any induced cylinder.

5 Postoperative Care

The surgeon may follow his or her usual refractive surgery postoperative care regimen.Administration of one drop of a topical ophthalmic antibiotic solution and one drop of anophthalmic nonsteroidal anti-inflammatory drug, continued for up to 3 days, according toproduct labeling, is recommended Administration of topical corticosteroids is not recom-mended A bandage contact lens may be used for comfort for 24 to 48 h postoperativelybut is usually not necessary

C UNITED STATES MULTICENTER CLINICAL TRIAL

1 Patients and Methods

A 2-year, multicenter, prospective clinical trial is being conducted in the United States toevaluate the safety, efficacy, and stability of conductive keratoplasty when performed oneyes with 0.75 to 3.00 D of hyperopia and less than 0.75 D of cylinder Each procedurewas performed by one of 14 surgeons at 20 centers according to methods described above.All eyes were treated at the default setting of 350 kHz, 60% power for 0.6 s No retreatmentswere performed

A total of 231 patients were treated; 361 eyes were treated with the current nomogramfor CK and an additional 29 were treated with an earlier nomogram that had a tendency

to undercorrect (Table 2) These 29 eyes were excluded from analysis of efficacy variables.Thus, data from 361 eyes were evaluated for efficacy, stability, and safety, while datafrom 390 eyes were evaluated for stability and safety only At 12 months, a total of 96eyes were available for stability and safety analyses and 127 were available for stability,safety, and efficacy analyses Uncorrected distance visual acuity (UCVA) preoperativelywas 20/40 or worse in 81% of the eyes, and uncorrected near visual acuity was J5 orworse in 95% Postoperative care and examinations followed the methods described above

Table 2 Clinical Study Eyes

MRSE—Manifest refractive spherical equivalent

CRSE—Cycloplegic refractive spherical equivalent

Evaluated for safety and stability variables only

Evaluated for all variables (Efficacy, safety, stability)

Available at 12 months for stability and safety analyses

Available at 12 months for safety, efficacy, and stability

analyses

Age

Mean Preoperative MRSE

Mean Preoperative CRSE

Figure 4 Postoperative UCVA over time.

2 Results

a Efficacy

Twelve months postoperatively, UCVA was 20/20 or better in 53/96 (55%), 20/25 orbetter in 73/96 (76%), and 20/40 or better in 87/96 (91%) of the eyes (Fig 4) Near UCVAincreased an average of six Jaeger lines Mean MRSE values showed 53/96 (55%) withinⳲ0.50 D of intended correction, 87/96 (91%) within Ⳳ1.00 D, and 94/96 (98%) withinⳲ2.00 D (Fig 5) A summary of the efficacy results with conductive keratoplasty isshown in Table 3

Table 3 Summary of Efficacy Results with Conductive Keratoplasty Compared with FDAGuidelines for Refractive Procedures

FDA ⫽ Food and Drug Administration

UCVA ⫽ Uncorrected Visual Acuity

MRSE ⫽ Manifest Refractive Spherical Equivalent

Figure 5 Accuracy of achieved MRSE.

b Corneal Topography

Corneal topography of a typical eye with an MRSE ofⳭ3.25 D and UCVA of 20/125preoperatively shows central steepening postoperatively surrounded by a midperipheralflattening (Fig 6) Twelve months postoperatively, this eye had an MRSE ofⳭ0.25 Dand UCVA of 20/20

Figure 6 Conductive keratoplasty case study Corneal topography of a typical eye with an MRSE

ofⳭ3.25 preoperatively D and UCVA of 20/125 preoperatively shows post-CK central steepeningsurrounded by a midperipheral flattening Twelve months postoperatively, this eye had an MRSE

ofⳭ0.25 D and UCVA of 20/20

Table 4 Stability of Manifest Refraction through 12 Months (Cohort of Patients with AllPostoperative Visits, N ⫽ 115)

Change in MRSE 3–6 Months 6–9 Months 9–12 Months

Mean Change (SD) 0.27 D (0.43) 0.09 D (0.40) 0.15 D (0.39)(paired differences)

95% Confidence Interval 0.19,0.35 0.01,0.17 D 0.07,0.23

MRSE—Manifest Refractive Spherical Equivalent

c Stability

Refractive stability after the procedure was demonstrated by the mean change in residual

SE refraction for all treated eyes at three intervals during the study (Table 4) During thelast two intervals (6 to 9 months, 9 to 12 months), the mean MRSE changed 0.09 D(confidence interval 0.01, 0.17) and 0.16 D (confidence intervals 0.07 and 0.22), respec-tively The mean change in MRSE between postoperative visits from 0.50 D or less in73% of the eyes between the 3- and 6-month visits, in 85% of the eyes between the 6-and 9-month visits, and in 83% of the eyes between the 9- and 12-month visits and in

83% of the eyes between the 9- and 12- month visits (Fig 7) The refraction appeared tostabilize at approximately 6 months

Figure 7 Change in MRSE between postoperative visits N⳱ 115 (patients present for all

follow-up visits)

Figure 8 Slit-lamp view of treatment spot 1 h after CK showing bands of striae between spots.The surface leukomas are small because all of the energy is delivered within the stroma (Courtesy

of Refractec, Inc., Irvine, CA.)

d Slit Lamp

One hour after treatment, the opacities at each treatment spot were visible by slit lamp assmall surface leukomas, with a band of striae connecting the treatment spots (Fig 8).These leukomas are small because CK delivers energy deep into the stroma rather than

on the surface The striae between treatment zones remain visible at 3, 6, and 12 months,

as reported by the United States CK clinical trial investigators, and suggest that the effect

of treatment on the stroma is long-lasting

e Safety

No eye had lost two or more lines of BSCVA and no eye had BSCVA worse than 20/40

at 12 months (Table 5) A total of 1/127 (1%) of eyes had an increase of ⬎2.00 D of

Table 5 Summary of Safety Results with Conductive Keratoplasty

Postoperative visit

1 Month 3 Months 6 Months 9 Months 12 Months(N⫽390) (N⫽390) (N⫽384) (N⫽218) (N⫽79)

cylinder at 12 months and 0/127 had an increase of 2.00 D Seventy five percent had nochange (withinⳲ 0.50 D) in cylinder No eye with BSCVA of 20/20 or better preopera-tively was worse than 20/25 postoperatively No intraoperative complications or adverseevents occurred during the surgeries, and there were no treatment-related adverse events.

D CONCLUSION

The 12-month results in the ongoing 2-year prospective clinical study of the CK techniquefor correcting low to moderate spherical hyperopia are encouraging Postoperative visualacuity and predictability of refraction were excellent and are comparable to or better thanresults obtained with PRK or LASIK for low hyperopia (17–34) The CK refractive effectappears to stabilize by 6 months, surpassing the early studies of refractive stability resultsseen following the noncontact LTK method (11–16) However, recent LTK postmarketingapproval data from phase 3 FDA clinical trials shows that LTK is stable after 3 months.Availability of the 2-year results will confirm the efficacy, predictability, and safety

of results seen with CK at 1 year and provide validation of this nonlaser option for thetreatment of low to moderate hyperopia

5 McDonnell PJ Radial thermokeratoplasty for hyperopia: I The need for prompt investigation.Refract Corneal Surg 1989; 5:50–52

6 Durrie DS, Schumer JD, Cavanaugh TB Holmium:YAG laser thermokeratoplasty for opia J Refract Corneal Surg 1994; 10:S277–S280

hyper-7 Eggink CA, Bardak Y, Cuypers MHM, Deutman AF Treatment of hyperopia with contactHo:YAG laser thermal keratoplasty J Refract Surg 1999; 15:16–22

8 Eggink CA, Meurs P, Bardak Y, Deutman AF Holmium laser thermal keratoplasty for opia and astigmatism after photorefractive keratectomy J Refract Surg 2000; 16:317–322

hyper-9 Koch DD, Kohnen T, McDonnell PJ, Menefee RF, Berry MJ Hyperopia correction by contact holmium:YAG laser thermokeratoplasty; United States phase IIA clinical study with

non-a 1-yenon-ar follow-up Ophthnon-almology 1996; 103:1525–1536

10 Koch DD, Kohnen T, Anderson JA, Binder PS, Moore MN, Menefee RF, Valderamma GL,Berry MJ Histologic changes and wound healing response following 10-pulse noncontactholium: YAG laser thermal keratoplasty J Refract Surg 1996; 12:623–634

11 Koch DD, Abarca A, Villarreal R, Menefee R, Kohnen T, Vassiliadis A, Berry M Hyperopiacorrection by non-contact holmium: YAG laser thermokeratoplasty: clinical study with two-year follow-up Ophthalmology 1996; 103:731–740

12 Koch D, Kohnen T, McDonnell P, Menefee R, Berry M Hyperopia correction by noncontactholmium: YAG laser thermal keratoplasty Ophthalmology 1997; 104:1938–1947

13 Nano HD, Muzzin S Noncontact holmium:YAG laser thermal keratoplasty for hyperopia JCataract Refract Surg 1998; 24:751–757

14 Koch DD, Kohnen T, McDonnell PJ, Menefee R, Berry M Hyperopia correction by noncontactholmium:YAG laser thermal keratoplasty: United States phase IIA clinical study with a 2-year follow-up Ophthalmology 1997; 104:1938–1947.

15 Alio JL, Ismail MM, Sanchez Pego JL Correction of hyperopia with non-contact Ho:YAGlaser thermal keratoplasty J Refract Surg 1997; 13:17–22

16 Alio JL, Ismail MM, Artola A, Perez-Santonja JJ Correction of hyperopia induced by fractive keratectomy using non-contact Ho:YAG laser thermal keratoplasty J Refract Surg1997; 13:13–16

photore-17 Pop M Laser thermal keratoplasty for the treatment of photorefractive keratectomy tions: A 1-year follow-up Ophthalmology 1998; 105:926–931

overcorrec-18 Ismail MM, Alio JL, Perez-Santonja JJ Noncontact thermokeratoplasty to correct hyperopiainduced by laser in situ keratomileusis J Cataract Refract Surg 1998; 24:1191–1194

19 Bende T, Jean B, Oltrup T Laser thermal keratoplasty using a continuous wave diode laser

27 Dausch D, Klein R, Schroder E Excimer laser photorefractive keratectomy for hyperopia JRefract Surg 1993; 9:20–28

28 Davidorf DM, Eghbali F, Onclinx T, Maloney RF Effect of varying the optical zone diameter

on the results of hyperopic laser in situ keratomileusis Ophthalmology 2001; 108:1266–1268

29 Argento CJ, Cosentino MJ Laser in situ keratomileusis for hyperopia J Cataract Refract Surg1998; 24:1050–1058

30 Ditzen K, Huschka H, Pieger S Laser in situ keratomileusis for hyperopia J Cataract RefractSurg 1998; 24:42–47

31 Esquenazi S, Mendoza A Two-year follow-up of laser in situ keratomileusis for hyperopia

hyper-35 Goth P, Stern R Conductive Keratoplasty, Principles and Technology, presented at the can Society for Cataract and Refractive Surgery, Boston, April, 2000

Ameri-36 Data on File, Refractec, Inc

Intracorneal Segments for Hyperopia

LAURA GOMEZ and ARTURO S CHAYET

Codet Aris Vision Institute, Tijuana, B.C., Mexico

proce-The ICS for hyperopia are designed to be permanent; however, they can be removed

if desired The ICS were conceptualized and developed by Steven M.Verity and DavidSchanzlin They initiated these studies in cadaver eyes using wires as the implantableintracorneal devices

The ICS for hyperopia were manufactured by Kera Vision, a vision correction pany, founded in 1986 with the purpose of giving people clear vision without using correc-tive lenses or undergoing surgeries that cut or remove tissue from the central optical zone

com-of the cornea The company filed for bankruptcy in 2001, and these segments are currentlynot produced However, the segments have been licensed to another entity, which mayproduce them in the future

The ICS are inserted radially between the layers of the corneal stroma through six

or eight small incisions made in the periphery of the cornea When surgically placed atapproximately two-thirds depth into the corneal stroma, these segments reshape the anteriorcorneal curvature, steepening the central cornea and thereby correcting for hyperopia (Fig

107

Figure 1 Diagram showing how the intrecorneal segments (ICS) work The six radially placedsegments create a flattening of the peripheral cornea by shortening the chord length between eachsegment in the direction of the arrows This peripheral flattening causes the central cornea to steepen,correcting for hyperopia

2) The degree of corneal steepening achieved using the ICS is directly related to thethickness of the ICS product implanted

The segments are made of polymethylmethacrylate (PMMA) and vary in lengthfrom 1.5 to 2.0 mm Each segment has a hexagonal cross section and is tapered along theinternal side to facilitate implantation The ICS thicknesses that we tested were 0.35, 0.40,and 0.45 mm The width of the segments was 0.5 or 0.8 mm The 1.8 mm length with0.8 mm width has been the most used

Figure 2 A 42-year-old woman with six ICS in place 18 months postoperatively