Laser in situ keratomileusis and intrastromal corneal ring segments for high myopia. Three-step procedure

We describe a surgical procedure to correct relatively high myopia in patients with thin corneas. The technique combines laser in situ keratomileusis (LASIK) and intrastromal corneal ring segment (ICRS) implantation. The 3-step procedure comprises ICRS channel formation, LASIK, and segment insertion. The technique was used in 2 eyes of 2 patients with low pachymetry values and high myopia. One patient achieved an uncorrected visual acuity (UCVA) of 20/30 and a best spectacle-corrected visual acuity (BSCVA) of 20/25 with +0.50 -1.75 x 101. The other patient achieved a UCVA of 20/30 and a BSCVA of 20/20 with +0.75 -1.50 x 80.     

Intacs after laser in situ keratomileusis and photorefractive keratectomy

PURPOSE: To evaluate the efficacy of intrastromal corneal ring segments (Intacs, Addition Technology) for the correction of residual myopia after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). METHODS: In this prospective noncomparative case series, Intacs were implanted in 5 eyes (4 patients) that developed myopic regression after LASIK or PRK. Intacs were implanted a minimum of 11 months after the laser procedure. The technique was identical to the standard procedure for myopic unoperated eyes. The Intacs thickness was based on the amount of residual myopia. RESULTS: Postoperative results revealed a reduction in the residual myopia and the mean K-reading. No eye lost best corrected Snellen visual acuity. No intraoperative or postoperative complications occurred. CONCLUSIONS: Implantation of Intacs in eyes with myopic regression after LASIK and PRK resulted in a good refractive outcome and an improvement in uncorrected visual acuity.     

Management of corneal ectasia after laser in situ keratomileusis with INTACS

PURPOSE: To evaluate the safety and efficacy of intrastromal corneal ring segments (ICRS, INTACS, Keravision) for the correction of corneal ectasia after laser in situ keratomileusis (LASIK). METHODS: In this prospective, noncomparative case series, INTACS were implanted in three eyes (two patients) that were ectatic after LASIK. Mean follow-up was 8.7 months (range, 8 to 10 mo). RESULTS: No intraoperative complications occurred. After INTACS implantation, uncorrected visual acuity ranged from 20/20 to 20/25 at 6 months and remained stable until 9 months. Mean postoperative spherical equivalent refraction was 0.50 D at 1 month and no significant changes appeared up to 9 months after INTACS implantation. After INTACS implantation, no eye lost any lines of Snellen spectacle-corrected visual acuity and two eyes gained from one to two lines. There was an increase in topographical regularity in all three eyes. CONCLUSION: Implantation of INTACS in eyes with corneal ectasia after LASIK resulted in good refractive outcome, absence of complications, and improvement in visual acuity.     

Intracorneal rings to correct corneal ectasia after laser in situ keratomileusis

PURPOSE: To evaluate the potential of using intrastromal corneal ring technology (Intacs, KeraVision) to correct posterior ectasia after laser in situ keratomileusis (LASIK) for myopia. SETTING: Department of Cornea and Refractive Surgery, Instituto Oftalmológico de Alicante, and Miguel Hernández University School of Medicine, Alicante, Spain. METHODS: In this prospective noncomparative intervention case series, Intacs segments were implanted in 3 eyes that developed posterior ectasia after myopic LASIK with clear central corneas. Posterior ectasia and corneal thickness were tested using the Orbscan II Slit Scanning Corneal Topography/Pachymetry System (Orbtek Inc.). Segment thickness varied based on corneal topography analysis and refraction. The mean follow-up was 8.3 months (range 7 to 11 months). RESULTS: The cases showed marked improvement after Intacs segment implantation. Postoperatively, there was a reduction in the magnitude of the posterior and anterior corneal surface steepening or ectasia and an increase in the topographical regularity index. In addition, the significantly enlarged optical zones resulted in a favorable visual outcome. In 2 eyes, the uncorrected visual acuity (UCVA) was 20/40 postoperatively. In the third eye, there was a residual refractive error; the UCVA was 20/50 and the best spectacle-corrected visual acuity, 20/40. CONCLUSIONS:Intacs intrastromal corneal rings used as a mechanical device may alter the biomechanical properties of the cornea for the correction of iatrogenic keratectasia and the associated residual myopia.     

Intracorneal ring segments after laser in situ keratomileusis

PURPOSE: To evaluate the safety and efficacy of intracorneal ring segments (ICRS) for correction of residual refractive error in patients previously operated with laser in situ keratomileusis (LASIK). METHODS: Thirteen postoperative LASIK eyes (eight patients) with residual myopic refractive error underwent implantation with INTACS (Keravision) intracorneal ring segments. Correction of the residual error was the first goal, but also improved best spectacle-corrected visual acuity was obtained by correcting residual irregular astigmatism. RESULTS: Mean spherical equivalent refraction improved from -3.25 to +0.75 D and mean uncorrected visual acuity improved from 0.2 to 0.6 after ICRS insertion. Best spectacle-corrected visual acuity remained stable or improved; no eyes lost lines of corrected visual acuity. In one of the 13 eyes, the intracorneal ring segments were removed because of progressive stromal melting. CONCLUSIONS: The use of corneal ring segments in selected eyes with residual myopic refractive errors after LASIK was safe and effective.     

Combined ICRS insertion and LASIK to maximize postoperative residual bed thickness in high myopia

PURPOSE: To describe a new technique and early outcomes of combined intrastromal corneal ring segment (ICRS) insertion and laser in situ keratomileusis (LASIK) to treat patients with moderate to high myopia and thin corneas. SETTING: University-based academic practice, Boston, Massachusetts, USA. METHODS: Combined ICRS insertion and LASIK was performed in 2 stages: ICRS channel formation (stage I) followed by LASIK and ICRS insertion (stage II). RESULTS: Fifteen eyes of 11 patients with a mean preoperative spherical equivalent of -9.98 diopters (D) +/- 2.60 (SD) (range -7.13 to -16.25 D) and mean preoperative astigmatism of 1.11 +/- 0.75 D (range 0.00 to -3.00 D) were treated with combined ICRS insertion and LASIK. The mean central pachymetry was 526.13 +/- 35.69 microm (472 to 579 microm). The uncorrected visual acuity was 20/40 or better in 7 of 15 eyes (46.67%) at 1 month, 6 of 12 eyes (50.00%) at 3 months, 5 of 12 eyes (41.67%) at 6 months, and 6 of 12 eyes (50.00%) at 12 months. The best spectacle-corrected visual acuity was 20/40 or better at all times. Postoperative maps confirmed the absence of ectasia. The postoperative spherical equivalent was within +/-1.00 D of the intended refraction in 11 of 15 eyes (73.33%) at 1 month, 9 of 12 eyes at 3 and 6 months, and 8 of 12 eyes (66.67%) at 12 months. CONCLUSIONS: Results of combined ICRS insertion and LASIK in moderately to highly myopic patients with relatively thin corneas were good. Long-term studies are needed to determine whether this procedure will decrease the risk of LASIK-induced keratectasia in these patients.     

Intrastromal corneal ring implantation for the correction of myopia: 12-month follow-up

PURPOSE: To evaluate the efficacy, predictability, and stability of refraction obtained after intrastromal corneal ring segment (ICRS) implantation for low to moderate myopia. SETTING: Single-center clinical practice. METHODS: In this prospective 2-surgeon study, 9 patients (15 eyes) with low to moderate myopia were recruited to receive ICRS implants. RESULTS: At 1 day, 10 of the 15 eyes had an uncorrected visual acuity (UCVA) of 20/40 or better. At 12 months, all eyes had this UCVA and 66.6% had 20/25 or better. The mean manifest refraction stabilized after the first week at <-0.5 diopter (D). At 12 months, all eyes were within +/-1.0 D of the intended manifest refraction; 67% were within +/-0.5 D. Sixty percent of eyes had no change from the preoperative best corrected visual acuity; 13.3% improved by 1 line, and 26.6% lost 1 line. The postoperative complications included lamellar channel deposits (n = 12), ICRS dislocation (n = 2), corneal infiltrates (n = 2), bleeding in the positioning ring hole (n = 1), 0.3 mm segment decentration (n = 1), and prolonged wound healing (n = 1). CONCLUSIONS: Intrastromal corneal ring segment implantation for the correction of low to moderate myopia afforded good visual recovery and efficacy similar to that with laser in situ keratomileusis and superior to that with photorefractive keratectomy. However, light or blunt trauma and insufficient hygiene can have serious consequences and there is the potential for induced astigmatism. Corneal infiltrates can occur and must be treated immediately. The ring implantation technique is demanding. Advantages of ICRS implantation include rapid and stable visual recovery as well as reversibility.     

Laser in situ keratomileusis results after intrastromal corneal ring segments (Intacs)

OBJECTIVE: To evaluate the safety and efficacy of laser in situ keratomileusis (LASIK) after removal of intrastromal corneal ring segments (Intacs, KeraVision, Fremont, CA) from the cornea. DESIGN: Single-center, noncomparative, interventional, consecutive case series. PARTICIPANTS: Nine eyes of nine consecutive patients who had undergone LASIK after Intacs of experimental design removal were analyzed for this study. INTERVENTION: A standard LASIK procedure was performed with the Nidek EC 5000 excimer laser (Nidek, Gamagori, Japan) at intervals between 4 and 10 months after Intacs explantation. A Nidek MK 2000 microkeratome (Nidek, Gamagori, Japan) or a Chiron Automated Corneal Shaper (Bausch & Lomb, Claremont, CA) with a 130- to 180-microm thickness plate was used to create a nasal hinged flap in a plane superficial to the previous Intacs channel. MAIN OUTCOME MEASURES: Uncorrected visual acuity, manifest refraction, best spectacle-corrected visual acuity, and topography were measured preoperatively and at months 1, 3, 6, and 12 after LASIK. RESULTS: Faint residual scarring in the channels after Intacs removal was seen in all patients. No difficulties were encountered during the ablation or flap replacement. Eight of nine patients had 20/20 or better uncorrected visual acuity after a single LASIK procedure. Mean spherical equivalent at 12 months was -0.6, ranging from -1.25 to +0.25 diopter. One patient had glare develop secondary to superior corneal thinning and scarring after implantation of a nonstandard Intacs. No patient lost lines of best spectacle-corrected vision after LASIK. CONCLUSION: Reversibility of the myopic Intacs is demonstrated. Removal of Intacs may be followed by a safe and effective LASIK for low to moderate myopia.     

Correction of spherical myopia with a single 150-degree intrastromal corneal ring segment

A 47-year-old woman with an uncorrected visual acuity (UCVA) of 20/70 and a refraction of -1.50 +0.75 x 75 in the right eye had 2 0.25 mm intrastromal corneal ring segments (Intacs) inserted uneventfully through a superior incision. The patient was hyperopic 2 years later with a refraction of +0.50 +0.75 x 25 and was intolerant of spectacles. She also complained of temporal glare. Twenty-seven months after insertion, the temporal ring segment was removed. Four months later, the UCVA was 20/20; with a refraction of plano +0.50 x 35, the visual acuity was 20/15. Topography showed corresponding regular astigmatism, and the patient's glare had resolved. Removal of 1 Intacs segment may be an option in cases of overcorrection after ring insertion for myopia.     

Correction of astigmatism with short arc-length intrastromal corneal ring segments: preliminary results

OBJECTIVE: To evaluate the refractive effect of 130 degrees short arc length intrastromal corneal ring segments (ICRS) designed to correct myopia concurrent with astigmatism. DESIGN: Prospective, nonrandomized, comparative (self-controlled) trial. PARTICIPANTS: Ten eyes of 6 patients from one surgical center with manifest refraction spherical equivalent between -1.00 and -6.00 diopters (D), manifest cylinder correction between 1.00 and 6.00 D, and best spectacle-corrected visual acuity of 20/20 or better. INTERVENTION: The patients were assigned to receive 1 of 6 ICRS thicknesses, ranging from 0.25 to 0.50 mm by 0.05 mm increments, with an arc length of 130 degrees. MAIN OUTCOME MEASURES: Vector analysis of astigmatic correction. Efficacy was assessed by uncorrected visual acuity and by deviation of postoperative spherical and cylindrical refractive error from predicted correction. Safety was assessed by maintenance or loss of preoperative best spectacle-corrected visual acuity. Measurements were made before surgery and after surgery at days 1 and 7 and months 1, 2, 3, and 6. RESULTS: At 6 months, uncorrected visual acuity was 20/20 or better in 80% of eyes (8/10) and 20/40 or better in all eyes. Eight of 10 eyes (80%) were within +/-0.25 D of plano spherical equivalent manifest refraction. There was no loss of best spectacle-corrected visual acuity, and 6 of 10 eyes (60%) gained a line. Reduction of keratometric cylinder by ICRS thickness was statistically significant (P = 0.039). CONCLUSIONS: Preliminary results of visual and refractive performance after correction of compound myopic astigmatism using short arc length ICRS are promising.     

Fluctuations in uncorrected visual acuity after refractive surgery using intra-stromal corneal rings]

PURPOSE: Refractive surgery is meant to provide early stable and good uncorrected visual acuity. Our main concern in this study was to take special interest in fluctuation in uncorrected acuity within the first three months after implantation of Schanzlin intracorneal ring segments (ICRS) produced by Keravision. PATIENTS AND METHODS: Ten eyes in 6 patients underwent implantation of 2 intrastromal corneal segments for myopias ranging from -1.00 to -3.50 Dipoters. Visual acuity was measured with cytoplegy on day one, on day 8, two weeks, 1 month, and 2 months after surgery. The fluctuations of visual acuity were noted between observations. RESULTS: Uncorrected visual acuity varied up to 4 lines without an obvious pattern of progression over time. Fifty percent of the eyes had a variation of 2 lines. The best spectacle corrected visual acuity was preserved in all patients. DISCUSSION: Corneal topography with measurement of keratometry, intraocular pressure, and examination of the anterior chamber must be studied to identify the parameter that could condition these fluctuations of visual acuity. No parameter was found to predict these variations that may result from individual corneal healing factors peculiar to each patient. The fluctuations of uncorrected visual acuity were relatively important during the 3 first postoperative months. In all patients, final uncorrected visual acuity was always at least 10/10.     

Adjustability of refractive effect for corneal ring segments

PURPOSE: To evaluate the safety and efficacy of adjustability of the refractive effect of intrastromal corneal ring segments (ICRS, Intacs). METHODS: Data from four patients who had their initial Intacs removed and exchanged for new Intacs of different thickness sizes during a United States Food and Drug Adminstration Phase II clinical trial were evaluated with regard to segment size, reasons for exchange, duration within the cornea before exchange procedure, loss or change of spectacle-corrected visual acuity, change of uncorrected visual acuity, manifest refraction, cycloplegic refraction, topography after exchange, and stability of refraction. RESULTS: The exchange procedure was performed in two patients due to undercorrection and in two for overcorrection. The length of time the segments remained in the cornea after initial surgery varied from 6 to 15 months (mean, 10.25 +/- 4.03 mo). The most recent examination occurred between 4 to 18 months (mean, 10.0 +/- 6.32 mo) following the exchange procedure and showed improved uncorrected visual acuity with a range from 20/16 to 20/20 and a gain of 2 to 7 lines of uncorrected visual acuity compared to baseline. No eyes lost any lines of spectacle-corrected visual acuity following the exchange procedure and all preserved their preoperative spectacle-corrected visual acuity of 20/16. The intended refractive correction was achieved in the first few days of the exchange procedure and remained stable. CONCLUSION: In these four eyes that were over- or undercorrected after initial Intacs placement, segment thickness sizes were exchanged after 6, 8, 12, and 15 months without complication and with final uncorrected visual acuities of 20/16 to 20/20.     

Photorefractive keratectomy after intrastromal corneal ring segment explantation

PURPOSE: To describe a case of photorefractive keratectomy after removal of intrastromal corneal ring segments from the cornea. METHODS: During United States Food and Drug Administration Phase III Trials for intrastromal corneal ring segments (ICRS), the implanted segments were removed from the cornea of the right eye of a patient because of dissatisfaction with glare, halos, and fluctuating vision. Ten months after ICRS explantation, the-patient underwent a photorefractive keratectomy procedure to the same eye. RESULTS: One month after removal of the ICRS, the patient's manifest refraction was within +/- 0.50 diopters of his original manifest refraction. Photorefractive keratectomy was planned to the same eye 6 months later. At the first attempt, the epithelium could not be removed with the laser and scrape technique, and residual epithelium was noted at the vertical meridian (12 o'clock) corneal incision site, which had been used for ICRS surgery and explant; therefore, the procedure was aborted. At the second attempt, with a mechanical epithelial brush (AMOILS Epithelial Scrubber; Innova, Inc, Toronto, Canada), the epithelium was removed with ease. After this, photorefractive keratectomy was done without difficulty or complication. At his most recent 8-month postphotorefractive keratectomy examination, the patient had an uncorrected visual acuity of RE: 20/16, with a manifest refraction of -0.75 to 0.75 x 170 degrees, a faint haze at the site of the stromal channel, and a small scar at the incision site on slit-lamp examination. CONCLUSIONS: Intrastromal corneal ring segments can be readily removed from the cornea, if required. In this case, the refraction returned to its preoperative state soon after the explant procedure and remained stable over time. Photorefractive keratectomy was performed as a secondary refractive surgical procedure after the removal of ICRS without difficulty or complication. However, removal of the epithelium is probably best accomplished with the use of an epithelial brush, considering the changes in the epithelial adherence in a postsurgical cornea. Further studies are required to establish the safety and efficacy of secondary refractive surgical procedures after ICRS explantation.     

Intrastomal corneal ring segments: reversibility of refractive effect

PURPOSE: To evaluate the reversibility of refractive effect following removal of the ICRS (intrastromal corneal ring segments; Intacs). METHODS: Data from 34 eyes from which ICRS were removed during United States FDA Phase II and III clinical trials were evaluated with regard to segment size, loss or change of best spectacle-corrected visual acuity (BSCVA), any change of uncorrected visual acuity (UCVA), manifest spherical equivalent refraction, manifest cylinder refraction, stability of manifest cylinder refraction, and subjective visual symptoms. RESULTS: Out of 725 initial or contralateral eyes placed with the ICRS during Phase II and III clinical trials, segments were removed from 34 eyes (4.7%). Other than one (1/725, 0.1%) safety related ICRS removal, 30/725 (4.1%) were due to visual symptoms. ICRS removal was accomplished under topical anesthesia without complications in all eyes. The mean length of time the segments remained in the cornea after initial surgery was 10.3 +/- 5.4 months. At 3 months after ICRS removal, 21 eyes had monitored data available and were within +/-1 line or 10 letters of their preoperative BSCVA. Twenty eyes (20/21, 95%) returned to within +/-1.00 D of their preoperative manifest spherical equivalent refraction. All eyes had a stable refraction at the 3-month examination after removal, and a manifest spherical equivalent refraction within +/-1.00 D of their 1-month examination after removal. Nineteen eyes (19/21, 90%) returned to within +/-2 lines and 16 eyes (16/21, 76%) returned to within +/-1 line of preoperative UCVA. CONCLUSION: The ICRS (Intacs) was easily and safely removed, and eyes returned to preoperative refractive status within 3 months.     

Topographic predicted corneal acuity with intrastromal corneal ring segments.

PURPOSE: To evaluate predicted optical quality of the central anterior corneal surface before and after the intrastromal corneal ring segment (ICRS) refractive procedure using a clinical videokeratoscope and software index developed for that purpose. METHODS: Predicted corneal acuity, a topographically derived index provided with the EyeSys System 2000 videokeratscope, representing potential optical quality of the cornea, was assessed preoperatively and at postoperative month 3 in 94 eyes that received an ICRS to treat -1.00 to -6.00 D of myopia. Predicted corneal acuity was calculated by determining the difference between a measured cornea and its best-fit ellipses for reflected ring circumferences within the central 3 mm diameter zone. RESULTS: Preoperative predicted corneal acuity was 20/10 in 92 of 94 eyes (98%). At month 3 after the ICRS procedure, 48 (51%) of moderately myopic eyes were corrected to 20/20 or better, 96% (90 eyes) were corrected to 20/40 or better, and 98% of eyes (92 eyes) had a predicted corneal acuity of 20/10. For the eyes with a predicted corneal acuity of 20/10, spectacle-corrected visual acuity was normally distributed between 20/10 and 20/25. CONCLUSION: Predicted corneal acuity did not change significantly from baseline in eyes with an ICRS. This suggests that topographic irregularities in the central 3 mm of the cornea detectable by predicted corneal acuity software were not induced in the central cornea with the ICRS.     

Correction of severe ectasia after LASIK with intracorneal ring segments

PURPOSE: To report a case of severe bilateral ectasia after LASIK that was treated with implantation of small-diameter Keraring intrastromal corneal ring segments (Mediphacos Ltd). METHODS: A 31-year-old woman underwent LASIK in 2001 at a different institution. One year after LASIK, the patient complained of decreased vision in the left eye and underwent LASIK retreatment. Three months after retreatment, uncorrected visual acuity (UCVA) was counting fingers and best spectacle-corrected visual acuity (BSVCA) was 0.4 in the left eye; UCVA was 0.1 and BSCVA was 0.3 in the right eye. Corneal topography showed inferior steepening bilaterally, consistent with ectasia, and the patient was fitted with rigid gas permeable contact lenses. The patient presented to our clinic 4 years after bilateral LASIK with severe loss of BSCVA in both eyes. Examination confirmed the diagnosis of severe bilateral ectasia. The patient underwent implantation of small-diameter Keraring segments assisted by femtosecond laser in June 2005 (left eye) and March 2006 (right eye). RESULTS: Best spectacle-corrected visual acuity improved by four lines in both eyes. Postoperative keratometry showed a decrease of seven diopters in the right eye and nine diopters in the left eye. Postoperative refraction and keratometry have remained stable for 18 and 10 months in the left and right eyes, respectively. CONCLUSIONS: Implantation of intracorneal ring segments can be considered as a treatment option in patients with severe ectasia after LASIK.     

One year results of European Multicenter Study of intrastromal corneal ring segments. Part 1: refractive outcomes

PURPOSE: To assess the efficacy, predictability, stability, and safety of correcting myopia with intrastromal corneal ring segments (ICRS, KeraVision, Inc.). SETTING: Twelve European investigational sites. METHODS: Patients with myopia of -1.0 to -6.0 diopters (D) and best spectacle-corrected visual acuity (BSCVA) of 20/20 or better (except in 3 eyes) were assigned to receive 1 of 5 ICRS thicknesses (0.25, 0.30, 0.35, 0.40, or 0.45 mm). Efficacy was assessed by postoperative uncorrected visual acuity (UCVA), predictability of refractive outcome (deviation from predicted cycloplegic refraction spherical equivalent), and stability of refractive effect (manifest refraction spherical equivalent [MRSE]). Safety was assessed by maintenance or loss of preoperative BSCVA and induced manifest refraction cylinder. Measurements were made preoperatively and 1 and 7 days and 1, 2, 3, 6, and 12 months postoperatively. RESULTS: One hundred fifty-nine ICRSs were implanted in the eyes of 107 patients (52 patients had bilateral implantation). Preoperatively, UCVA was worse than 20/40 in 98% of eyes (155/159); 12 months postoperatively, it was 20/20 or better in 63% of eyes (83/132) and 20/40 or better in 96% (127/132). Predicted refractive corrections for each ICRS thickness generally correlated with achieved corrections. At 12 months postoperatively, 90% of eyes (124/138) were within +/-1.00 D of plano (MRSE). Two or more lines of BSCVA were lost in 6% of eyes (8/135); all 8 eyes had BSCVAs of 20/25 or better. CONCLUSION: The ICRS safely, effectively, and predictably reduced or eliminated low to moderate myopia. Refractive correction was stable through the 12 month follow-up.     

Characterization of the aspheric corneal surface with intrastromal corneal ring segments.

PURPOSE: Anterior corneal surface asphericity was examined in eyes of Phase II clinical trial participants, before and after intrastromal corneal ring segments (ICRS, Intacs) refractive surgery, and surveyed for relationship to clinical visual performance. METHODS: Aspheric test objects with surface asphericity (Q) ranging from -0.01 Q to -1.44 Q and base radius of curvatures ranging from 7.5 mm to 9.0 mm were measured topographically using videokeratography. Radius of curvature asphericity profile plots were produced for test objects and compared to similar plots created for trial participant eyes (n=25) to quantify corneal asphericity. The potential effects of different amounts of corneal asphericity were assessed using measurement of uncorrected and spectacle-corrected visual acuity and photopic contrast sensitivity. RESULTS: Preoperative corneal asphericity ranged from -0.01 Q to -0.81 Q and postoperative from -0.01 Q to -1.44 Q. Preoperative uncorrected visual acuity was significantly related to corneal asphericity; more myopic eyes tended to have more prolate corneal asphericity. Corneal asphericity was not significantly related to spectacle-corrected visual acuity or photopic contrast sensitivity, before or after surgery. CONCLUSION: Postoperative corneal asphericity values demonstrated that intrastromal corneal ring segments (Intacs) produced a prolate aspheric surface for myopic correction from -1.00 D to -6.00 D. This study indicated that the range of corneal asphericity measured in these 25 eyes, before and after surgery, provided good visual acuity and normal contrast sensitivity.     

First clinical results with the femtosecond neodynium-glass laser in refractive surgery

PURPOSE: We evaluated four femtosecond laser intrastromal cutting procedures: creation of a corneal flap for laser in situ keratomileusis (LASIK), tunnel and entry cut for intracorneal ring, corneal flap and removable lens for keratomileusis, and intrastromal ablation for myopia and hyperopia. METHODS: A clinical trial using a femtosecond surgical laser (IntraLase Corporation) was performed in partially sighted eyes. Femto-LASIK treatment was performed on 46 eyes up to -14.00 D; 16 patients received intracorneal ring segments (Femto-ICRS); 5 patients each with one highly myopic eye had femtosecond laser keratomileusis (FLK), and 13 patients each with one myopic or hyperopic eye had intrastromal ablation (ISPRK). In Femto-LASIK, excimer laser ablation was done under the flap. In Femto-ICRS, ring segments were introduced into the laser-created channels. In femtosecond laser keratomileusis, a lens-shaped block of stroma was removed manually from under the flap. RESULTS: No difference was found between the results obtained with Femto-LASIK and a standard microkeratome. No refractive effects occurred when the created flap was not elevated. In cases of Femto-ICRS and conventional ICRS produced the same refractive results. With Femto-ICRS, no intraoperative complications occurred and visual acuity improved immediately after surgery. In femtosecond laser keratomileusis, high myopia was corrected without using excimer laser ablation; centralization of the treatment area was excellent. In intrastromal ablation, 1 to 2 hours after surgery the corneas were highly transparent; refractive results were stable. CONCLUSIONS: Femtosecond lasers can produce precise intrastromal cutting, offering significant safety and other advantages (no razor blades, corneal trauma, partial resections, or sterilization issues) over current techniques.     

Effect of intrastromal corneal ring segment shift on clinical outcome: one year results for low myopia

PURPOSE: To evaluate the effect of intrastromal corneal ring segment (ICRS) shift on clinical outcome. SETTING: Chu Morvan Ophthalmology Service, Brest, France. METHODS: Forty-seven eyes with myopia from -1.0 to -5.0 diopters (D) had ICRS surgery according to United States Food and Drug Administration protocol using a 2-segment implant design. Visual acuity, refractive, videotopographic, and biomicroscopic results in eyes that did not have contact between segments (Group A, n = 26) and in eyes that did have contact (Group B, n = 21) were compared. RESULTS: Soon after surgery, migration of and subsequent contact between the implant segments occurred in 21 eyes (45%). Contact between the inferior ends was most common, occurring in 19 eyes; in the remaining 2 eyes, the superior ends of the implant touched. Superior contact was associated with superficial channels, wound-healing problems, and ICRS explantation. No segment shift was observed after the first postoperative week. No significant differences in visual acuity, qualitative vision, or density of intrastromal deposits were noted between the 2 groups. However, at 6 months there was more induced with-the-rule cylinder in Group B (mean +1.3 D +/- 0.7 [SD]) than in Group A (mean +0.7 +/- 0.5 D). Astigmatism was clinically significant in only 3 cases at 3 months. CONCLUSIONS: Induced cylinder remains a limitation of the ICRS procedure, and segment contact appears to influence the rate of induced cylinder. Overall, however, the ICRS procedure produces promising results. Research efforts are underway to address induced cylinder and channel deposits associated with ICRS surgery.