Ординатура / Офтальмология / Английские материалы / Hyperopia and Presbyopia_Tsubota, Boxer Wachler, Azar_2003
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taking care not to damage the tip. Perform intraoperative keratometry after completing the 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 an ophthalmic nonsteroidal anti-inflammatory drug, continued for up to 3 days, according to product labeling, is recommended. Administration of topical corticosteroids is not recommended. A bandage contact lens may be used for comfort for 24 to 48 h postoperatively but 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 to evaluate the safety, efficacy, and stability of conductive keratoplasty when performed on eyes with 0.75 to 3.00 D of hyperopia and less than 0.75 D of cylinder. Each procedure was 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 retreatments were performed.
A total of 231 patients were treated; 361 eyes were treated with the current nomogram for 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 data from 390 eyes were evaluated for stability and safety only. At 12 months, a total of 96 eyes were available for stability and safety analyses and 127 were available for stability, safety, and efficacy analyses. Uncorrected distance visual acuity (UCVA) preoperatively was 20/40 or worse in 81% of the eyes, and uncorrected near visual acuity was J5 or worse in 95%. Postoperative care and examinations followed the methods described above.
Table 2 Clinical Study Eyes
Eyes |
Attribute |
|
|
Evaluated for safety and stability variables only |
N 390 |
Evaluated for all variables (Efficacy, safety, stability) |
N 361 |
Available at 12 months for stability and safety analyses |
N 96 |
Available at 12 months for safety, efficacy, and stability |
N 127 |
analyses |
|
|
Age |
55 |
5.4 years (40 to 74) |
Mean Preoperative MRSE |
1.82 |
0.60 D (0.75 to 3.00 D) |
Mean Preoperative CRSE |
1.76 |
0.60 D (0.75 to 3.25 D) |
|
|
|
MRSE—Manifest refractive spherical equivalent
CRSE—Cycloplegic refractive spherical equivalent
Conductive Keratoplasty |
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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 or better in 73/96 (76%), and 20/40 or better in 87/96 (91%) of the eyes (Fig. 4). Near UCVA increased an average of six Jaeger lines. Mean MRSE values showed 53/96 (55%) within0.50 D of intended correction, 87/96 (91%) within 1.00 D, and 94/96 (98%) within2.00 D (Fig. 5). A summary of the efficacy results with conductive keratoplasty is shown in Table 3.
Table 3 Summary of Efficacy Results with Conductive Keratoplasty Compared with FDA Guidelines for Refractive Procedures
|
FDA |
6 Months |
9 Months |
12 Months |
|
guideline |
(N 348) |
(N 276) |
(N 96) |
|
|
|
|
|
UCVA 20/20 |
50% |
46% |
48% |
55% |
UCVA 20/25 |
Not stipulated |
65% |
72% |
76% |
UCVA 20/40 |
85% |
90% |
92% |
91% |
MRSE 0.50 D |
50% |
60% |
66% |
55% |
MRSE 1.00 D |
75% |
88% |
88% |
91% |
MRSE 2.00 D |
Not stipulated |
99% |
99% |
98% |
FDA Food and Drug Administration
UCVA Uncorrected Visual Acuity
MRSE Manifest Refractive Spherical Equivalent
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Figure 5 Accuracy of achieved MRSE.
b. Corneal Topography
Corneal topography of a typical eye with an MRSE of 3.25 D and UCVA of 20/125 preoperatively shows central steepening postoperatively surrounded by a midperipheral flattening (Fig. 6). Twelve months postoperatively, this eye had an MRSE of 0.25 D and UCVA of 20/20.
Figure 6 Conductive keratoplasty case study. Corneal topography of a typical eye with an MRSE of 3.25 preoperatively D and UCVA of 20/125 preoperatively shows post-CK central steepening surrounded by a midperipheral flattening. Twelve months postoperatively, this eye had an MRSE of 0.25 D and UCVA of 20/20.
Conductive Keratoplasty |
103 |
Table 4 Stability of Manifest Refraction through 12 Months (Cohort of Patients with All Postoperative Visits, N 115)
Change in MRSE |
3–6 Months |
6–9 Months |
9–12 Months |
|
|
|
|
0.50 D |
73% |
85% |
83% |
0.75 D |
90% |
94% |
97% |
1.00 D |
96% |
97% |
97% |
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 the last 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), respectively. The mean change in MRSE between postoperative visits from 0.50 D or less in 73% 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 12month visits (Fig. 7). The refraction appeared to stabilize at approximately 6 months.
Figure 7 Change in MRSE between postoperative visits. N 115 (patients present for all followup visits).
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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 as small 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) |
|
|
|
|
|
|
|
2 Lines loss of BSCVA |
6% |
5% |
4% |
2% |
0% |
2 Lines loss of BSCVA |
2% |
1% |
1% |
1% |
0% |
BSCVA Worse than 20/40 |
0% |
0% |
0% |
0% |
0% |
Increase 2.00 D Cylinder |
3% |
2% |
1% |
0% |
0% |
Increase 2.00 D Cylinder |
3% |
2% |
1% |
1% |
1% |
BSCVA 20/25 if better |
4% |
2% |
1% |
1% |
0% |
than 20/20 Pre-op |
|
|
|
|
|
|
|
|
|
|
|
BSCVA—Best Spectacle-Corrected Visual Acuity
Conductive Keratoplasty |
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cylinder at 12 months and 0/127 had an increase of 2.00 D. Seventy five percent had no change (within 0.50 D) in cylinder. No eye with BSCVA of 20/20 or better preoperatively was worse than 20/25 postoperatively. No intraoperative complications or adverse events 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 technique for correcting low to moderate spherical hyperopia are encouraging. Postoperative visual acuity and predictability of refraction were excellent and are comparable to or better than results obtained with PRK or LASIK for low hyperopia (17–34). The CK refractive effect appears to stabilize by 6 months, surpassing the early studies of refractive stability results seen following the noncontact LTK method (11–16). However, recent LTK postmarketing approval 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 the treatment of low to moderate hyperopia.
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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 noncontact holium: 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. Hyperopia correction by non-contact holmium: YAG laser thermokeratoplasty: clinical study with twoyear follow-up. Ophthalmology 1996; 103:731–740.
12.Koch D, Kohnen T, McDonnell P, Menefee R, Berry M. Hyperopia correction by noncontact holmium: YAG laser thermal keratoplasty. Ophthalmology 1997; 104:1938–1947.
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14.Koch DD, Kohnen T, McDonnell PJ, Menefee R, Berry M. Hyperopia correction by noncontact holmium: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:YAG laser thermal keratoplasty. J Refract Surg 1997; 13:17–22.
16.Alio JL, Ismail MM, Artola A, Perez-Santonja JJ. Correction of hyperopia induced by photorefractive keratectomy using non-contact Ho:YAG laser thermal keratoplasty. J Refract Surg 1997; 13:13–16.
17.Pop M. Laser thermal keratoplasty for the treatment of photorefractive keratectomy overcorrections: A 1-year follow-up. Ophthalmology 1998; 105:926–931.
18.Ismail MM, Alio JL, Perez-Santonja JJ. Noncontact thermokeratoplasty to correct hyperopia induced 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. J Refract Surg 1999; 15:154–158.
20.Geerling G, Koop N, Brinkmann R, Tungler A, Wirbelauer C, Birngruber R, Laqua H. Continu- ous-wave diode laser thermokeratoplasty in blind human eyes. J Refract Surg 1999; 25:32–40.
21.Mendez A, Mendez Noble A. Conductive keratoplasty for the correction of hyperopia. In: Sher NA, ed. Surgery for Hyperopia and Presbyopia. Williams & Wilkins; 1997:163–171.
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10
Intracorneal Segments for Hyperopia
LAURA GOMEZ and ARTURO S. CHAYET
Codet Aris Vision Institute, Tijuana, B.C., Mexico
A. BACKGROUND
The intracorneal segments (ICS) for hyperopia reshape the anterior surface of the cornea without permanently changing the structure or function of the natural eye and are intended to be an alternative to eyeglasses, contact lenses, or irreversible refractive surgery procedures for hyperopic patients. The radially placed segments create a flattening of the peripheral cornea by shortening the chord length tangential to the limbus. This peripheral flattening causes the central cornea to steepen and the corneal radius to decrease, thus correcting for hyperopia (Fig. 1). Implantation of the segments does not involve the central cornea and no tissue is removed. In addition, the cornea maintains its asphericity and normal prolate shape when the segments are implanted—an advantage also reported for the intrastromal corneal ring segments for myopia (Intacs) (1,2).
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 David Schanzlin. They initiated these studies in cadaver eyes using wires as the implantable intracorneal devices.
The ICS for hyperopia were manufactured by Kera Vision, a vision correction company, founded in 1986 with the purpose of giving people clear vision without using corrective lenses or undergoing surgeries that cut or remove tissue from the central optical zone of the cornea. The company filed for bankruptcy in 2001, and these segments are currently not produced. However, the segments have been licensed to another entity, which may produce 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 at approximately two-thirds depth into the corneal stroma, these segments reshape the anterior corneal curvature, steepening the central cornea and thereby correcting for hyperopia (Fig.
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Figure 1 Diagram showing how the intrecorneal segments (ICS) work. The six radially placed segments create a flattening of the peripheral cornea by shortening the chord length between each segment 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 the thickness of the ICS product implanted.
The segments are made of polymethylmethacrylate (PMMA) and vary in length from 1.5 to 2.0 mm. Each segment has a hexagonal cross section and is tapered along the internal 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 with 0.8 mm width has been the most used.
Figure 2 A 42-year-old woman with six ICS in place 18 months postoperatively.
Intracorneal Segments for Hyperopia |
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Most of the initial ICS surgeries worldwide in human eyes were performed by the authors (AC and LG) in Tijuana, Mexico. A small European trial was started. In the United States, there is no experience with this technique in human eyes.
B. INDICATIONS/CONTRAINDICATIONS
The intracorneal segments for hyperopia are intended for the correction of low hyperopia with a cylinder less than or equal to 0.75 D. Our experience included patients with a cycloplegic spherical equivalent refraction between 1.00 to 5.00 D; however, we found that this technique did not correct hyperopias greater than 2.0 D. Patients should have a documented stability of their refraction as demonstrated by a change of less than or equal to 0.50 D in spherical and cylindrical components of the manifest refraction for the prior 6 months.
The ICS are contraindicated in
Pregnant or nursing women Patients with signs of keratoconus
Patients with clinically significant corneal dystrophy or scarring in the 6- or 7-mm central zone
Patients with a history of herpetic keratitis
Patients with an autoimmune disease, collagen vascular disease, clinically significant atopic syndrome, insulin-dependent diabetes or an immunocompromised state
C. PREOPERATIVE PREPARATION
A complete ocular exam of both eyes should be performed. This includes visual acuity testing with and without correction using standardized ETDRS (Early Treatment Diabetic Retinopathy Study) visual acuity charts, slit-lamp examination, corneal topography, keratometry, manifest and cycloplegic refractions, tonometry, and ultrasound pachymetry of the central and peripheral cornea and funduscopy.
D. SURGICAL TECHNIQUE
The operative eye was prepared with povidone-iodine 10% solution and the eyelid margins and cilia were draped to fully isolate the surgical field. Topical anesthesia was achieved using two drops of 0.5% tetracaine hydrochloride. A Barraquer wire speculum was placed to hold the lids apart. One eye was treated at a time.
The surgical procedure started with the identification of the geometric center of the cornea using a blunt Sinskey hook. A preinked marker was centered on the cornea to provide a visual guide for the placement of the six circumferential incisions and the placement of each segment at a 6.0-mm optical zone. Corneal pachymetry (DHG Technology, Exton, PA) was performed over the site of each incision. A 15-degree diamond knife (KMI, Philadelphia, PA) was used to make a 1.0-mm incision at a depth of 67% of the pachymetry reading along the peripheral corneal marks. A modified Suarez spreader was used to begin a lamellar corneal dissection at the base of each incision. Specially designed instruments (KeraVision, Fremont, CA) were used to create an intrastromal pocket toward the previously marked 6-mm optical zone. It is very important to make sure that the tunnels