Intracorneal rings to correct corneal ectasia after laser in situ keratomileusis

Safety and efficacy of Intacs in Indian eyes with keratoconus: an initial report

Context

In contact lens-intolerant keratoconus patients, intrastromal placement of Intacs is becoming a promising new modality of treatment.

Aims

To study the safety and efficacy of implantation of microthin corneal inserts (Intacs) in Asian-Indian keratoconus patients.

Settings and Design

Retrospective interventional case series, in the cornea and refractive surgery service, at a tertiary care eye hospital in South India, between May 2006 and July 2007.

Materials and Methods

Intacs (Addition Technology, USA) were successfully implanted by mechanically creating tunnels, in 12 eyes of 12 keratoconus patients, who were contact lens-intolerant. The patients (mean age 25.58 years, nine male and three female) had a minimum follow-up of six months. Five patients had severe keratoconus (mean K > 53 D) and nine had central cones.

Results

All patients improved or retained visual acuity. The uncorrected visual acuity (UCVA) improved from a mean value of 0.06, (SD ± 0.08) to 0.19 postoperatively (SD± 0.15) (P= 0.01). The change in mean best corrected visual acuity (BCVA) was from 0.51, (SD ± 0.24), to 0.69, (SD ±0.00) (P = 0.01) postoperatively. The average central keratometry reading was 52.55 D. The change in mean K from 52.84 to 49.16 and 49.15 at one and six months respectively, was statistically significant. We did not have any major intra- or early postoperative complications. Eight of 12 eyes became contact lens-tolerant post-surgery.

Conclusion

The procedure of Intacs implantation appears to be safe and effective in a small group of Indian population at an intermediate follow-up.

Management of slipped laser in situ keratomileusis flap following intrastromal corneal ring implantation in post-LASIK ectasia

Two cases of intrastromal corneal ring (Intacs, Addition Technology) implantation to treat post-laser in situ keratomileusis (LASIK) ectasia developed progressive slippage of the flap over the stromal bed, resulting in progressive flattening of the affected meridian. The flattening was thought to have occurred because the poorly healed flap edge could not withstand the change in corneal shape induced by the ring segments. The flap was lifted, debris was removed, and the flap was sutured to the residual stromal bed using interrupted 10-0 nylon sutures passed through two thirds of the cornea. The sutures induced a localized area of scarring that acted as "welding spots" and prevented further flap slippage. Refractive stability after suture removal supports the hypothesis that a sutured flap restores (at least partially) the biomechanical strength of post-LASIK corneas.

Advances in technologies for laser-assisted in situ keratomileusis (LASIK) surgery

Laser-assisted in situ keratomileusis (LASIK) has become the most widely used form of refractive surgery today. The objective of this surgical technique is to modify the anterior corneal shape by ablating tissue from the stroma by means of the excimer laser after creating a hinged corneal flap. This way, we are able to change the refractive status of the patient, providing better unaided vision. Continuous improvements in the original technique have made the surgical procedure safer, more accurate and repeatable. These progressions are due to the development of novel technologies that are the responsible for new surgical instrumentation, which makes the surgical procedure easier for the surgeon, and better excimer laser ablation algorithms, which increase the optical quality of the ablation and thus the safety of the vision correction procedure. This article aims to describe the more relevant advances in LASIK that have played an important role in the spread and popularity of this technique.

Alterations of extracellular matrix components and proteinases in human corneal buttons with INTACS for post-laser in situ keratomileusis keratectasia and keratoconus

PURPOSE

To perform an immunohistochemical evaluation of corneas with INTACS for post-laser in situ keratomileusis (LASIK) keratectasia and keratoconus, obtained after corneal transplantation.

METHODS

Corneas from 1 patient with INTACS for post-LASIK keratectasia and 2 patients with INTACS for keratoconus were obtained within 3 hours after penetrating keratoplasty, and cryostat sections were analyzed by immunostaining for 35 extracellular matrix (ECM) components and proteinases.

RESULTS

In the stroma of all corneas next to an INTACS implant, ECM components typically associated with fibrosis were observed. These included tenascin-C, fibrillin-1, and types III, IV (alpha1/alpha2 chains), and XIV collagen. Also, significant deposition of perlecan, nidogen-2, and cellular fibronectin was revealed in the same locations. The keratoconus cases displayed typical Bowman layer breaks and subepithelial fibrosis with deposition of various ECM components. In all cases, some keratocytes around INTACS were positive for specific proteinases associated with stromal remodeling, including cathepsins F and H, matrix metalloproteinase (MMP)-1, MMP-3, and MMP-10. Staining for MMP-7 was variable; MMP-2 and MMP-9 were mostly negative. Patterns of type IV collagen alpha 3, alpha 4, and alpha 6 chains; types VI and VIII collagen; laminin-332, alpha 4, alpha 5, beta1, beta2, and gamma 1 laminin chains; vitronectin; thrombospondin-1; urokinase; EMMPRIN; and cathepsins B and L were unchanged around INTACS in all 3 cases compared with normal.

CONCLUSIONS

Abnormal accumulation of fibrotic ECM components and proteinases near INTACS suggests ongoing lysis and remodeling of corneal stroma. Specific changes observed in each case may be related to underlying pathology.

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.

Visual rehabilitation and outcomes for ectasia after corneal refractive surgery

PURPOSE

To analyze the visual outcomes and method of final visual correction in eyes with corneal ectasia after laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK).

SETTING

Emory University Department of Ophthalmology and Emory Vision, Atlanta, Georgia, USA.

METHODS

This retrospective review comprised 74 eyes of 45 patients with corneal ectasia after LASIK (72 eyes) or PRK (2 eyes). Outcomes included postoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), best corrected visual acuity (BCVA), and refraction; method of final visual correction; and time to rigid gas-permeable (RGP) contact lens failure.

RESULTS

Corneal ectasia developed a mean of 19.2 months after surgery. Postoperatively, the mean UCVA was 20/400 and the mean BSCVA before ectasia management was 20/108. After ectasia management, the mean BCVA was 20/37 and the final BCVA was 20/40 or better in 78% of eyes. Final visual correction was achieved with RGP lenses in 77% of eyes, spectacles in 9%, collagen crosslinking in 3%, intracorneal ring segments in 1%, and penetrating keratoplasty (PKP) in 8%. Two eyes with intracorneal ring segments required segment explantation and subsequent PKP. One eye that had PKP had a graft-rejection episode; there were no graft failures. Two eyes (3%) did not require a visual device to improve visual acuity. The mean time for successful RGP lens wear was 24.8 months; 80% of cases initially managed with RGP lenses were successful with this form of treatment.

CONCLUSIONS

The majority of eyes developing postoperative corneal ectasia achieved functional visual acuity with RGP lens wear and did not require further intervention. Penetrating keratoplasty can usually be postponed or avoided by alternative methods of visual rehabilitation; however, PKP, when necessary, can provide good visual outcomes.

Risk Assessment for Ectasia after Corneal Refractive Surgery

PURPOSE

To analyze the epidemiologic features of ectasia after excimer laser corneal refractive surgery, to identify risk factors for its development, and to devise a screening strategy to minimize its occurrence.

DESIGN

Retrospective comparative and case-control study.

PARTICIPANTS

All cases of ectasia after excimer laser corneal refractive surgery published in the English language with adequate information available through December 2005, unpublished cases seeking treatment at the authors' institution from 1998 through 2005, and a contemporaneous control group who underwent uneventful LASIK and experienced a normal postoperative course.

METHODS

Evaluation of preoperative characteristics, including patient age, gender, spherical equivalent refraction, pachymetry, and topographic patterns; perioperative characteristics, including type of surgery performed, flap thickness, ablation depth, and residual stromal bed (RSB) thickness; and postoperative characteristics including time to onset of ectasia.

MAIN OUTCOME MEASURES

Development of postoperative corneal ectasia.

RESULTS

There were 171 ectasia cases, including 158 published cases and 13 unpublished cases evaluated at the authors' institution. Ectasia occurred after LASIK in 164 cases (95.9%) and after photorefractive keratectomy (PRK) in 7 cases (4.1%). Compared with controls, more ectasia cases had abnormal preoperative topographies (35.7% vs. 0%; P<1.0x10(-15)), were significantly younger (34.4 vs. 40.0 years; P<1.0x10(-7)), were more myopic (-8.53 vs. -5.09 diopters; P<1.0x10(-7)), had thinner corneas before surgery (521.0 vs. 546.5 microm; P<1.0x10(-7)), and had less RSB thickness (256.3 vs. 317.3 microm; P<1.0x10(-10)). Based on subgroup logistic regression analysis, abnormal topography was the most significant factor that discriminated cases from controls, followed by RSB thickness, age, and preoperative corneal thickness, in that order. A risk factor stratification scale was created, taking all recognized risk factors into account in a weighted fashion. This model had a specificity of 91% and a sensitivity of 96% in this series.

CONCLUSIONS

A quantitative method can be used to identify eyes at risk for developing ectasia after LASIK that, if validated, represents a significant improvement over current screening strategies.

Intracorneal rings for keratoconus and keratectasia

Intrastromal corneal ring segments were designed to achieve refractive adjustment by flattening the cornea. Recently, they have been used to reshape keratoconic corneas to improve uncorrected visual acuity, best corrected visual acuity, and contact lens tolerance and to delay or prevent the need for keratoplasty. Intracorneal ring segments have several distinct and important advantages. New thicknesses and different ring sizes and the use of femtosecond lasers to dissect channels inside the cornea will likely improve the surgical outcomes. This article reviews the latest data published or presented at meetings on the correction of keratoconus and keratectasia by intracorneal ring segments.

Intacs for keratoconus

PURPOSE OF REVIEW

The use of Intacs as a therapeutic modality in contact lens intolerant patients with mild to moderate keratoconus is increasingly gaining acceptance in the ophthalmic community.

RECENT FINDINGS

During the past year we have gleaned significant new information about patients who are appropriate candidates, the location and relative placement of segment sizes and long-term safety and stability after Intacs placement. Another new and exciting development which will make this procedure safer and more commonly acceptable is the use of the femtosecond laser to create the channels to insert the Intacs, which has been described for the first time this year. This technology allows for accurate depth of inserting, improved outcomes and less complications due to superficial placement. New reports about Intacs revision surgery also allows us to retreat many patients who would otherwise have been considered surgical failures.

SUMMARY

The new advances described this past year will improve outcomes and ultimately contribute to an increase in the amount of physicians performing this procedure and the number of patients requesting it.

Deep anterior lamellar keratoplasty in post-laser in situ keratomileusis keratectasia

We describe a technique using deep anterior lamellar keratoplasty (DALK) in 5 eyes that developed keratectasia after LASIK. The technique is based on surgical manipulation that allows visualization of the lamellar dissection depth using a posterior approach to reach the predescemetic space. The mirror effect, indentation effect, and folding effect were used to determine proximity to Descemet's membrane. The same diameter donor and recipient buttons were used to correct myopia. The donor button without Descemet's membrane was placed using 10-0 nylon sutures. No intraoperative or postoperative complications occurred. The mean best spectacle-corrected visual acuity changed from 0.16 diopter (D) +/- 0.05 (SD) (range 0.10 to 0.25 D) before DALK to 0.68 +/- 0.19 D (range 0.5 to 1.0 D) after DALK. Deep anterior lamellar keratoplasty may be a better alternative than penetrating keratoplasty for any pathology with healthy endothelium.

Penetrating keratoplasty versus intrastromal corneal ring segments to correct bilateral corneal ectasia: Preliminary study

PURPOSE

To describe the outcomes over time in patients with corneal ectasia pathology treated with intrastromal corneal ring segments (Intacs, Addition Technology, Inc.) in 1 eye and penetrating keratoplasty (PKP) in the other eye.

SETTING

Clinica de Cornea, Centro Medico Docente La Trinidad, Caracas, Venezuela.

METHODS

A nonrandomized comparative study and analysis of retrospective data comprised 17 patients who had PKP in 1 eye and Intacs implantation in the other eye. Patients were classified into 2 groups: asymmetric (different grade of keratoconus in each eye) and symmetric (same grade of keratoconus in both eyes). Parameters analyzed included uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and keratometry (flat and steep values and astigmatism readings). Follow-up after PKP was at 24 hours and 6 and 24 months and after Intacs implantation, at 24 hours and 3 and 10 months.

RESULTS

In both groups, UCVA improved and the corneal shape was normal. No patient lost a line of acuity, and BCVA improved in both groups.

CONCLUSIONS

Eyes with Intacs had a shorter recovery time than eyes having PKP. The eyes with Intacs had no complications. Complications in eyes with PKP included cataract, graft rejection, and elevated intraocular pressure. Thus, Intacs segments may delay or prevent the need for a corneal graft, although longer follow-up is needed.

Long-term follow-up of Intacs in keratoconus

PURPOSE

To evaluate long-term follow-up of Intacs microthin prescription inserts (Addition Technology, Inc, Fremont, California, USA) for the management of keratoconus.

DESIGN

A long-term (five years) retrospective, follow-up study.

METHODS

Seventeen eyes of 15 patients with keratoconus ages 24 to 52 years (mean age +/- standard deviation [SD], 34.0 +/- 10.5 years) who had completed five years of follow-up (mean follow-up +/- SD, 67.2 +/- 7.5 months; range, 58 to 78 months) were included. Two Intacs segments of 0.45-mm thickness were inserted in the cornea of each eye, aiming at embracing the keratoconus area to try to achieve maximal flattening.

RESULTS

No late postoperative complications occurred in this series of patients. At five years, the spherical equivalent error was statistically significantly reduced (pre-Intacs, mean +/- SD -5.54 +/- 5.02 diopters [D]; range, -12.50 to 3.63 D; -3.02 +/- 2.65 D; range, -8.25 to 1.88 D) (P = .01). Pre-Intacs uncorrected visual acuity (UCVA) was 20/50 or worse in all eyes (range, counting fingers to 20/50), whereas, at the last follow-up examination, 10 (59%) of 17 eyes had UCVA of 20/50 or better (range, counting fingers to 20/32). Six eyes (35%) maintained the pre-Intacs best spectacle-corrected visual acuity (BSCVA) and one eye lost 3 lines of BSCVA, whereas the rest of the 10 eyes (59%) experienced a gain of one up to 8 lines.

CONCLUSIONS

After five years, intracorneal ring segments implantation improved UCVA, BSCVA, and refraction in the majority of the keratoconus patients. There was no evidence of progressive sight-threatening complications in this study.

Ten-year Follow-up of 360° Intrastromal Corneal Rings for Myopia

PURPOSE

To determine the safety, efficacy, and stability of intrastromal corneal rings 10 years after placement for myopia.

METHODS

Ten eyes with myopia treated with the placement of 360 degrees complete intrastromal corneal rings with the ends sutured together were evaluated at 10-year follow-up for the following: uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction spherical equivalent (MRSE), induced manifest refractive cylinder, keratometry readings, slit-lamp findings, and ultrasound central pachymetry. Ten-year data were compared to 1-year results to assess visual stability over time.

RESULTS

No statistically significant difference was noted between UCVA at 1 year and 10 years. At the 10-year examination, 90% of patients had BSCVA > or = 20/25 and 100% had BSCVA > or = 20/30. There was no statistically significant difference between MRSE at 1 year and 10 years. At the 10-year examination, induced manifest refractive cylinder was >1.00 diopter (D) in 0% of eyes and < or = 0.25 D in 60% of eyes. There was no statistically significant difference between mean central keratometric power at 1-year follow-up compared with 10-year follow-up. No statistically significant difference was noted in central corneal thickness between 1 and 10 years in the eyes studied.

CONCLUSIONS

Intrastromal corneal rings are an effective and stable method of correcting mild myopia based on optic parameters.

Long-term Follow-up of Intacs for Post-LASIK Corneal Ectasia

OBJECTIVE

To report long-term follow-up of Intacs microthin prescription inserts for the management of post-LASIK corneal ectasia.

DESIGN

Long-term (5 years), retrospective, nonrandomized study.

PARTICIPANTS

Eight eyes of 5 patients with post-LASIK corneal ectasia (3 men and 2 women) ages 31 to 54 years (mean age+/-standard deviation [SD], 41.60+/-9.24 years) who had completed 5 years of follow-up (mean follow-up +/- SD, 60.1+/-4.9 months; range, 57-68 months).

INTERVENTION

Two Intacs segments, inserted in the usual fashion, were used for low myopia correction (1 each nasally and temporally), with thickness based on the residual refraction of the patients.

MAIN OUTCOME MEASURES

Manifest refraction, uncorrected and best spectacle-corrected visual acuity, patient satisfaction, topography, and confocal microscopy analysis.

RESULTS

No intraoperative or late postoperative complications occurred in this series of patients. At 5 years, the SE error was statistically significantly reduced (pre-Intacs mean+/-SD, -5.47+/-2.66 diopters [D]; range, -11.50 to -3.00 D) to -2.56+/-3.44 D (range, -9.50 to 1.5 D; P = 0.01). At the end of the first postoperative year, refractive stability was obtained and remained stable during the follow-up period with no significant changes between the interval meantime (P>0.05). Pre-Intacs uncorrected visual acuity was 20/100 or worse in all eyes (range, counting fingers-20/100), whereas at the last follow-up examination, 6 (75%) of 8 eyes had uncorrected visual acuity of 20/40 or better (range, counting fingers-20/25). Two eyes (25%) maintained the pre-Intacs best spectacle-corrected visual acuity, whereas the rest of the eyes (6 eyes; 75%) experienced a gain of 1 or 2 lines. At the end of the first postoperative year, uncorrected and best-spectacle corrected visual acuity and topographic stability were obtained and were shown to have remained stable during the follow-up period with no significant changes between the interval meantime. Lamellar channel deposits were observed in confocal microscopy at or adjacent to the intrastromal ring segment.

CONCLUSIONS

Refractive stability was maintained for up to 5 years in the treatment of post-LASIK corneal ectasia after Intacs implantation. There was no evidence of progressive time-dependent corneal ectasia, late regression, or sight-threatening complications in this study.

Post-laser in-situ keratomileusis ectasia: current understanding and future directions

PURPOSE OF REVIEW

The aim of this article is to review the causes, risk factors, management, and future research directions for corneal ectasia after laser in situ keratomileusis.

RECENT FINDINGS

Complex corneal biomechanical processes influence the integrity of the normal and postoperative cornea, and developing an understanding of these processes facilitates recognition of risk factors for ectasia after laser in-situ keratomileusis. Currently identified risk factors include keratoconus, high myopia, low residual stromal bed thickness from excessive ablation or thick flap creation, and defined topographic abnormalities such as forme fruste keratoconus and pellucid marginal corneal degeneration. Ectasia can also rarely occur in patients without currently identifiable risk factors, and future identification of at-risk patients may be facilitated by corneal interferometry and corneal hysteresis measurements. Utilization of intraoperative pachymetry measurements at the time of surgery and confocal microscopy prior to enhancement to measure residual stromal bed thickness should avoid unanticipated low residual stromal bed thickness. Management options for ectasia after laser in situ keratomileusis include intraocular pressure reduction, rigid gas permeable contact lenses, and intracorneal ring segments, in addition to corneal transplantation. In the future, collagen cross-linking may reduce corneal steepening and improve refractive error.

SUMMARY

When ectasia develops, early recognition and proper management are essential to prevent progression, to promote visual rehabilitation, and to reduce the need for corneal transplantation for these patients.

Chronic pain after Intacs implantation

A 39-year-old woman developed corneal ectasia after laser in situ keratomileusis. Intracorneal ring segments (Intacs, Addition Technology, Inc.) were placed in the left eye in November 2004. Postoperatively, inferior topographic steepening decreased significantly and a rigid gas-permeable lens yielded 20/25 visual acuity. However, the patient reported persistent discomfort that did not improve with topical medications or a bandage contact lens. In May 2005, confocal microscopy demonstrated a corneal nerve in direct contact with the inferior segment. Both segments were removed, and after removal, the patient reported complete resolution of the pain.

INTACS for keratoconus

BACKGROUND

INTACS are two, arc like, PMMA segments which were designed to be surgically inserted into the deep corneal stroma to flatten the central cornea. Their original application was for the refractive correction of mild myopia (−1 to −3D). However, because of the superior accuracy and familiarity with the excimer laser by refractive surgeons, they are rarely used for this indication, except in patients with forme fruste keratoconus or extremely thin corneas with less than 3D of Myopia (1,2).

Dr. Joseph Colin in France first conceived of the concept of using INTACS to treat patients with keratoconus and published his first report on the safety and efficacy for this indication in 2001(3). At 1 year, all 10 patients he operated became contact lens tolerant and demonstrated an improvement in both uncorrected and best-corrected acuity (4).

Since his pioneering work, corneal surgeons throughout the word have adopted this technology to treat patients with mild to moderate keratoconus who are contact lens intolerant and/or who desire a modest improvement in uncorrected and best-corrected visual acuity (5-14).

In the United States 0.25mm, 0.275mm, 0.30mm, 0.325mm and 0.35mm segments are available for use. They are approved in the United States by the FDA under an Human Devise Exemption for compassionate therapeutic use. Outside of the United States .40mm and 0.45mm sized segments are also available. Competitive devices the Ferrara ring and the Keraring are also sold and marketed outside of the United States since they do not have FDA approval in the USA. The main difference between these two devices is that with INTACS the optical zone is approximately 7mm while the Ferrara and Kerarings have an optical zone of the order of 4.5 to 5mm.

Recently Intacs SK was introduced outside of the United States. They have an optical zone of 6 mm and have a round design to minimize glare. They may be used to correct larger myopic and astigmatic refractive errors than INTACS because of their design and closer proximity to the visual axis(15)

Modified Intracorneal Ring Segment Implantations (INTACS) for the Management of Moderate to Advanced Keratoconus

PURPOSE

To evaluate the safety and efficacy of modified intracorneal ring segment implantation (INTACS) in the management of moderate and advanced keratoconus (KCN).

METHODS

A modified procedure of intracorneal ring segment (INTACS) implantation was performed in eyes with moderate to advanced keratoconus that were intolerant to contact lens or spectacle correction. The main outcome measures were uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), refraction, and keratometry. The preoperative values were compared with the values 6 and 12 months postoperatively.

RESULTS

Implantation was performed on 20 eyes of 15 patients; 9 were female and 6 were male. The mean age was 30.2 years (SD +/- 5.44; range, 23-40). At the 6-month follow-up, UCVA improved from 20/154 (SD +/- 0.11) preoperatively to 20/28 (SD +/- 0.21) postoperatively (P < 0.05); BCSVA improved from 20/37 (SD +/- 0.21) preoperatively to 20/22 (SD +/- 0.13) postoperatively (P < 0.05). Spherical refractive error improved from -3.38 D (SD +/- 3.12) to -1.15 D (SD +/- 1.84); cylindrical refractive error improved from -3.75 (SD +/- 2.04) preoperatively to -1.21 (SD +/- 0.84) postoperatively (P < 0.05); average keratometry decreased from 49.50 D (SD +/- 1.64) preoperatively to 46.35 D (SD +/- 1.50) postoperatively. The changes remained stable to the 12-month follow-up. There was 1 case of anterior chamber perforation. There were 6 eyes that had ring exposure secondary to corneal thinning over the implants 3-6 months postoperatively, and a dense corneal infiltrate developed in 1 patient at 7 months postoperatively.

CONCLUSIONS

The procedure appears to be effective in improving UCVA and BSCVA of patients with clinical keratoconus. In our small study group, however, there were significant (6/20) postoperative problems with regards to thinning and ring exposure.

Comparison of Topographic Corneal Irregularity After LASIK and Intrastromal Corneal Ring Segments in the Same Patients

PURPOSE

To retrospectively compare the irregularity of the corneal surfaces of 14 patients after LASIK in 1 eye and placement of intrastromal corneal ring segments (ICRS) in the other eye.

METHODS

In a within-patient comparison, Orbscan corneal topography was used to retrospectively compare the corneal surface irregularity of LASIK-treated and ICRS-treated eyes at an outpatient tertiary-care ophthalmology clinic in Sao Paulo, Brazil. For the anterior corneal surface, irregularity measurements were compared for both the central and peripheral areas of the cornea. The differences between each group were analyzed for statistical significance.

RESULTS

The corneal surfaces of eyes treated with ICRS were found to be more irregular than the corneal surfaces of eyes treated with LASIK, the mean irregularity being 1.91 for LASIK-treated eyes and 3.12 for ICRS-treated eyes in the anterior corneal surface and 0.51 for LASIK-treated eyes and 0.87 for ICRS-treated eyes in the posterior corneal surface. A statistically significant difference was noted only in the posterior surfaces.

CONCLUSIONS

When measured with Orbscan topography, ICRS-treated eyes show more corneal surface irregularity than LASIK-treated eyes. The difference in outcome for the two types of treatment may be due to the mechanical effect of the ICRS on the shape of the cornea.

Are intracorneal rings still useful in refractive surgery?

PURPOSE OF REVIEW

This article reviews the latest data published and presented at international meetings about the use of intracorneal ring segments in corneal and refractive surgery.

RECENT FINDINGS

The long-term data on intracorneal ring segments in the correction of low to moderate myopia indicate that they seem clearly comparable with laser in-situ keratomileusis, the most common refractive procedure worldwide. There is increasing interest in the use of intracorneal ring segments for the treatment of some complications after laser in-situ keratomileusis and for the control of some degrees of primary corneal ectatic disorders such as keratoconus and pellucid marginal degeneration.

SUMMARY

Intracorneal ring segments are and will be useful in several corneal and refractive abnormalities. Concern still exists about their predictability and the long-term effects of their use in primary and secondary ectasia.

LASIK With an Inferior Hinge

PURPOSE

To investigate the refractive results and corneal pachymetric changes after laser in situ keratomileusis (LASIK) with an inferior hinge.

METHODS

Forty-six eyes of 23 patients who underwent LASIK with an inferior hinge were involved in this prospective study. All patients had a complete ophthalmic examination including uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, computerized corneal topography (Orbscan II Corneal Topography System; Orbscan Inc, Salt Lake City, Utah), air-puff tonometry, slit-lamp examination of the anterior segment, and fundus examination.

RESULTS

Preoperatively, mean sphere was -4.09+/-0.27 diopters (D) (range: -8.00 to -0.25 D), mean cylinder was -0.60+/-0.11 D (range: -3.25 to 0.00 D), and mean spherical equivalent refraction was -4.39+/-0.27 D (range: -8.63 to -1.50 D). At 1 month postoperatively, mean sphere was -0.04+/-0.01 D (range: -0.25 to 0.00 D), mean cylinder was -0.01+/-0.01 D (range: -0.50 to 0.00 D), and mean spherical equivalent refraction was -0.04+/-0.02 D (range: -0.00 to -0.50 D). At 1 month postoperatively, no eyes lost any lines of BSCVA.

CONCLUSIONS

Laser in situ keratomileusis with an inferior hinge is an alternative technique, which was safe and effective in our series. Further studies with long-term follow-up comparing the incidence of corneal ectasia in eyes with a superior hinge to that in eyes with an inferior hinge are recommended.

Keratectasia after bilateral laser in situ keratomileusis in a patient with previous radial and astigmatic keratotomy

We describe a case of bilateral keratectasia after laser in situ keratomileusis (LASIK) in a patient with previous radial keratotomy and astigmatic keratotomy. The best spectacle-corrected visual acuity (BSCVA) was 20/25 in both eyes. After uneventful LASIK was performed in both eyes for low myopic astigmatism, the patient presented with progressive myopia and astigmatism and a BSCVA of 20/50 in both eyes. Videokeratography showed progressive deformation of the cornea, increasing K-values over 50.0 diopters, and irregular astigmatism. The best corrected visual acuity in both eyes improved to 20/25 with rigid poly(methyl methacrylate) contact lenses.

Photoablative inlay laser in situ keratomileusis (PAI-LASIK) in the rabbit model

PURPOSE

To evaluate the suitability, biocompatibility, and efficacy of a proprietary hydrogel photoablative inlay (PAI) for use during laser in situ keratomileusis (LASIK).

SETTING

Laboratory study, Tulane University Health Sciences Center, New Orleans, Louisiana, USA.

METHODS

Eight rabbits (1 eye each) underwent the PAI-LASIK procedure; 4 eyes had a disk-shaped inlay and 4, a donut-shaped inlay. Preoperatively, the hydrogel material was ablated with a programmed correction of 5.0 diopters of hyperopia or myopia.

RESULTS

The eyes were followed for 1 to 16 months. No eye showed signs of rejection or extrusion of the PAI. There was no significant difference in corneal clarity or the healing rate between eyes with donut-shaped PAIs and those with disk-shaped PAIs. One eye with a donut-shaped PAI had minimal corneal haze. The remaining inlays did not opacify or fracture during ablation.

CONCLUSION

The hydrogel material can be used for the proposed PAI-LASIK procedure.

Le kératocône : options chirurgicales actuelles

The treatment of keratoconus is in part dependant on the severity of the disease process. When contact lenses fail because of patient intolerance or insufficient acuity to meet the patient's needs, penetrating keratoplasty is the usual surgical modality considered for satisfactory visual rehabilitation. Keratoconus is considered to be a contraindication for incisional refractive surgery such as radial keratotomies or LASIK because of the corneal instability conferred by these procedures. When the cornea is transparent, INTACS implantation is a refractive modality that may improve visual function and in some instances prevent the need for corneal transplantation in select patients with keratoconus.

Orbscan computerized topography: Attributes, applications, and limitations

An extensive electronic search was undertaken in January 2004 to identify all relevant peer-reviewed publications on Orbscan slit-scanning/Placido computerized topography. Ninety-one publications were identified. These address elevation topography and best-fit sphere, accuracy and repeatability of anterior and posterior corneal elevation and keratometric maps, comparison of Orbscan-acquired data and Placido-based computerized videokeratography instruments, pachymetry measurement and correlation with ultrasound, screening eye-bank corneas, detection of keratoconus, identifying corneal ectasia after refractive surgery, and miscellaneous applications. Studies were analyzed and critically compared in relation to attributes, applications, and limitations of Orbscan corneal topography. The review highlights advantages of this technique in assessing the cornea in health and disease and after surgery and identifies specific aspects that require further investigation and clarification.

INTACS Before or After Laser in situ Keratomileusis: Correction of Thin Corneas With Moderately High Myopia

PURPOSE

Intrastromal corneal ring segments (INTACS Micro-Thin Prescription Inserts by Addition Technologies, Fremont, Calif) were inserted as a combined surgery with laser in situ keratomileusis (LASIK) in six eyes with thin corneas to correct moderately high myopia.

METHODS

INTACS were implanted before LASIK (INTACS-LASIK) in three eyes and after LASIK (LASIK-INTACS) in three eyes. Mean preoperative manifest spherical equivalent refraction was -7.88 diopters. Mean follow-up was 306 days.

RESULTS

No intraoperative complications occurred. The LASIK-INTACS eyes were slightly more overcorrected than the INTACS-LASIK eyes because of the enhanced performance of INTACS in the thinned corneal tissue. Induced astigmatism by INTACS per se was less in the LASIK-INTACS eyes than in the INTACS-LASIK eyes. At last examination, uncorrected visual acuity was better than 20/25 in all eyes. Best spectacle-corrected visual acuity was within 1 line of the preoperative value in all eyes.

CONCLUSION

Both methods resulted in significant improvement in visual acuity and refraction. Based on our limited experience, however, LASIK followed by INTACS is preferred for reasons of safety, convenience, and lower induced cylinder.

Progressive Keratectasia After Laser in situ Keratomileusis

PURPOSE

We describe ten patients who developed progressive keratectasia following laser in situ keratomileusis (LASIK) and identify possible factors that may lead to ectasia.

METHODS

In this retrospective study, we reviewed the files of 3,634 patients (6941 eyes) who had LASIK between March 2000 and April 2003. Ten patients (14 eyes, 0.2%) developed progressive keratectasia. We also evaluated consequent therapeutic measures and final visual status of these patients.

RESULTS

Patients were examined at a mean 24.9 +/- 8.1 months after LASIK. Ectasia developed within a mean 14 +/- 0.3 months after surgery. At baseline, mean keratometric power was 44.7 +/- 2.30 D, mean corneal thickness was 516 +/- 18.9 microm, and mean attempted correction was -10.85 +/- 3.20 D. We found a statistically significant correlation between residual stromal thickness, attempted correction, and occurrence of progressive keratectasia. We also found that preexisting abnormal corneal topography was a risk factor for progressive keratectasia. Ultimately, most patients had reasonable visual acuity after penetrating keratoplasty.

CONCLUSION

Progressive keratectasia is a vision threatening complication of LASIK that may occur in previously healthy or diseased eyes. The most important risk factors are residual stromal thickness and preexisting abnormal corneal topography. Penetrating keratoplasty may be a reasonable therapeutic measure for severe cases of progressive keratectasia.

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.

Keratitis after implantation of intrastromal corneal ring segments

A 53-year-old man had implantation of 2 intrastromal corneal ring segments (Intacs, Addition Technology Inc.) in the left eye. Several days after the lower segment was exchanged, an infiltrate was present at the corneal incision site. This progressed to a lower channel infection followed by diffuse keratitis. Culture from the conjunctiva was positive for Staphylococcus epidermidis, but cultures from the cornea were negative for microorganisms. Later, 2 gas bubbles appeared at the interface. The patient was treated with topical and subconjunctival antibiotics and channel irrigation. The keratitis resolved, leaving a neovascularized opacity at the nasal part of the lower channel.

Single Intacs segment for post-laser in situ keratomileusis keratectasia

PURPOSE

To describe the visual outcome of implantation of a single Intacs segment (Addition Technology Inc.) in eyes with keratectasia after myopic laser in situ keratomileusis (LASIK).

SETTING

Private refractive surgery center, Jerusalem, Israel.

METHODS

This retrospective, noncomparative, interventional, consecutive, small case series studied 5 eyes of 5 patients with post-LASIK keratectasia from 3 refractive laser centers treated by Intacs implantation. Before and 9 months after Intacs implantation, the uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, keratometry, videokeratography, inferior-superior asymmetry, and patient questionnaires about visual function were assessed.

RESULTS

Intacs implantation was performed 17 to 32 months post LASIK with no intraoperative complications and no loss of visual acuity. After implantation, the UCVA improved 8, 4, 3, 0.5, and 5 lines and the BSCVA, 2, 2.5, 1, 0.5, and 2 lines. The mean manifest refraction spherical equivalent improved from -1.60 diopters (D) +/- 1.67 (SD) to -0.80 +/- 1.05 D. The mean manifest astigmatic correction decreased from -3.9 +/- 2.96 to -2.46 +/- 2.77 D. Corneal topography showed improved inferior steepening and less irregular astigmatism. The mean inferior-superior asymmetry improved from 7.88 +/- 4.59 to 2.46 +/- 2.77 D. Self-reported visual symptoms improved significantly in Cases 1, 2, and 5 and slightly in Cases 3 and 4.

CONCLUSIONS

Implantation of a single Intacs segment inferiorly appeared to improve progressive myopia and regular and irregular astigmatism in eyes with corneal ectasia after LASIK. With further study, this technique may prove to be an effective, relatively noninvasive approach.

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.

Optimization of contact lens fitting in keratectasia patients after laser in situ keratomileusis

PURPOSE

To evaluate the clinical outcomes of contact lens fitting in eyes with keratectasia after laser in situ keratomileusis (LASIK) to optimize the performance of the contact lenses.

SETTING

Contact Lens Clinic, Seoul National University Hospital, Seoul, Korea.

METHODS

Six eyes of 4 patients with keratectasia were examined. Keratectasia was diagnosed based on abnormal topographic findings, progressive myopic changes, and uncorrected visual acuity with glasses. A multicurve lens or reverse-geometry lens (RGL) was selected based on the anterior elevation map. The base curve radius and peripheral parameters were determined based on the axial map and the evaluation of the fluorescein pattern of the lens. The contact lens fitting characteristics and visual acuity were evaluated. Patients were interviewed about their level of comfort, daily contact lens wear time, and glare.

RESULTS

Multicurve lenses and RGLs were fitted in 4 eyes and 2 eyes, respectively. The base curve radius of the multicurve lenses ranged from 7.2 to 7.5 mm; the alignment curve radius of RGLs was 7.6 mm in both cases. The radii of peripheral curves were customized to enhance tear interchange. Visual acuity improved to 20/30 or better in all eyes. All patients were completely satisfied with the comfort of the fitting. The mean daily wearing time was 12.7 hours. One patient reported tolerable glare in the eye after being fitted with an RGL.

CONCLUSION

Proper contact lens fitting based on topographic data and slitlamp evaluation allowed good visual rehabilitation and comfortable extended daily wear in patients with keratectasia after LASIK.

Morphologic Characteristics of Lamellar Channel Deposits in the Human Eye

OBJECTIVE

To report the histologic characteristics of lamellar channel deposits after polymethyl methacrylate intrastromal corneal ring segments in a human eye.

METHODS

A 34-year-old man previously diagnosed with keratoconus received photorefractive keratectomy in his left eye that exacerbated his corneal ectasia. To delay or possibly prevent corneal transplant, the patient elected to have intrastromal corneal segments implanted in the left eye. One year later the patient underwent corneal transplant. Before transplant, lamellar channel deposits were noted on clinical microscopic examination of the left eye. We performed histologic evaluation to assess changes to the patient's excised corneal tissue and to further characterize the observed lamellar channel deposits.

RESULTS

Lamellar channel deposits in humans are histologically similar to our previous descriptions of deposits in rabbits. These deposits primarily consist of intracellular lipid accumulations that stain positively with oil red O and filipin but not periodic acid Schiff reaction. Immunohistochemistry of cells located in the deposit region stained positively with vimentin, suggesting that these cells were keratocytes. Stains for cytokeratins 3 and 12 and for CD68 were both negative, indicating that epithelial cells and macrophages were not present in the deposit region.

CONCLUSION

Lamellar channel deposits are a common clinical finding after intrastromal corneal implants. This case provides further evidence to support our hypothesis that lamellar channel deposits in humans are a tissue response to corneal implants that consist of intracellular lipid accumulations. We use this case to propose a theoretical construct for the observation of stromal lipid accumulation in response to corneal injury.

Comparison of Four Corneal Pachymetry Techniques in Corneal Refractive Surgery

PURPOSE

To assess the effectiveness of optical and ultrasonic pachymetry when examining corneas of patients before and after laser in situ keratomileusis (LASIK).

METHODS

We conducted a prospective study of 25 patients (50 eyes) who had LASIK for myopia or myopic astigmatism (mean spherical equivalent refraction -4.80 +/- 3.60 D; range -1.75 to -12.00 D). Corneal thickness was measured using 1) conventional ultrasonic pachymetry (20 MHz probe) in the central cornea, 2) ASL confocal microscopy (CMTF analysis), 3) Orbscan II Analyzer, and 4) ultrasound biomicroscopy (UBM) (50 MHz probe) preoperatively and 3 months postoperatively.

RESULTS

Preoperative pachymetry values measured with the Orbscan II Analyzer (551.3 +/- 27.3 microm) were almost identical to those measured with the 20 MHz ultrasonic probe (553.7 +/- 25.7 microm; t-test P = .652). The mean preoperative pachymetry for UBM was 566.7 +/- 38.8 microm and for CMTF was 553.2 +/- 15.5 microm. The optic and ultrasonic system measurements differed in operated eyes; 20 MHz ultrasonic pachymetry yielded an average 478.7 +/- 23.5 microm and the UBM, 482.4 +/- 40.3 microm. These measurements differed from the Orbscan II (Tukey test; P = .023) measurement of 461.1 +/- 37.5 microm but not from the confocal microscopy measurement of 475.2 +/- 41.8 microm. UBM registered greater values that were more variable than those obtained with ultrasonic pachymetry.

CONCLUSIONS

In non-operated eyes, corneal thickness was similar using conventional ultrasound, Orbscan II, or confocal techniques, with ultrasound biomicroscopy giving thicker readings.

Ectasia after laser in situ keratomileusis

Eighty-five cases of post laser in situ keratomileusis ectasia were reviewed and analyzed. Cases of keratoconus or forme fruste keratoconus were eliminated; many remaining case reports lacked key information. The current literature is unable to define a specific residual corneal thickness or a range of preoperative corneal thickness that would put an eye at risk for developing ectasia. The most logical cause for eyes without preexisting pathology to develop ectasia is a postablation stromal thickness that is mechanically unstable; this "minimal" thickness is probably specific to each eye. The preoperative and postoperative corneal thickness, measured flap thickness, and microkeratome and laser parameters used in a given case are required to determine the range of residual corneal thickness that puts the eye at risk for developing ectasia. Other as yet undetermined factors may play a role in the development of this complication.