Conservative Treatment of Early and Moderate Pellucid Marginal DegenerationA new refractive approach with intracorneal rings

Simultaneous Implantation of Refractive Lenticule and Intracorneal Ring Segment in the Management of Pellucid Marginal Degeneration

PURPOSE

To describe a patient with pellucid macular degeneration suffering from visual deterioration due to high irregular astigmatism and intolerant to contact lenses, who underwent a new surgical procedure that combined intrastromal lamellar keratoplasty and a 359° intracorneal ring segment implantation, enabling both ametropia and corneal thinning correction.

METHODS

Case report.

RESULTS

Refractive lenticule obtained during a myopic small incision lenticule extraction procedure was used as the donor lamellar graft. The technique described allowed for partial cylinder reduction and reinforcement of the thinned cornea. Uncorrected distance visual acuity improved from 0.02 to 0.5 (decimal) and corrected distance visual acuity improved from 0.4 to 0.7 with a decrease of 4.50 diopters in corneal astigmatism.

CONCLUSIONS

Despite the lack of long-term observation, the new technique described in this case report was successful for this specific patient and therefore might be effective and safe in severe stages of disease. [J Refract Surg. 2019;35(9):606-609.].

Intracorneal Ring Segment Implantation in the Management of Keratoconus: An Evidence-Based Approach

Intracorneal ring segment (ICRS) implantation represents a modern, minimally invasive, surgical option for visual improvement in patients with keratoconus. ICRS modify the corneal geometry in a manner that enhances its refractive properties and thereby, they improve visual acuity. It is well-documented that implantation of ICRS decreases the keratometric readings, spherical equivalent and cylinder, reduces high-order aberrations and improves uncorrected distance visual acuity (UDVA) and best-corrected distance visual acuity (BCDVA) in patients with keratoconus. Success rate after ICRS implantation is high, depending on appropriate patient selection and adherence to suitable implantation nomograms, and most important, the overall complication rate is very low. This review is summarizing current indications/contra-indications for ICRS implantation, implantation techniques, clinical outcomes and potential complications, shedding light on myths and realities related to this innovative surgical option.

Surgical management of peripheral corneal thinning disorders

The peripheral corneal thinning disorders are associated with degenerative, autoimmune, or infective causes. Corneal thinning can subsequently affect the visual acuity either by inducing severe astigmatism or by progressive involvement of the central cornea. In addition to this, the integrity of the eye is at risk. Medical management is necessary to address the underlying inflammatory or infectious causes; however, most of the cases require surgical intervention for tectonic support or for visual rehabilitation in patients with severe astigmatism. Preoperative investigations help in mapping the corneal curvature and thickness, thereby facilitating planning of treatment. Routine corneal transplantation techniques do not yield good results in peripheral corneal thinning disorders. Various surgical modifications have been described to manage these challenging cases. We review the available literature on causes and management of peripheral corneal thinning disorders.

Fitting Tips and Visual Rehabilitation of Irregular Cornea with a New Design of Corneoscleral Contact Lens: Objective and Subjective Evaluation

OBJECTIVES

To study the fitting and the visual rehabilitation obtained with a corneoscleral contact lens, namely, Rose K2 XL in patients with irregular cornea.

METHODS

This prospective study included 36 eyes of 36 patients with irregular cornea fitted with Rose K2 XL. Refractive and visual outcomes and mesopic and aberrometric parameters of fitted eyes were assessed at 2 weeks, 3 months, and 6 months after the initial lens use. Objective and subjective parameters of patient satisfaction and lens comfort were noted. Causes of lens discontinuation and complications were also recorded.

RESULTS

Average logMAR VA improved significantly from 0.95 ± 0.09 without correction to 0.04 ± 0.05 six months after lens wear. Similarly, mesopic and aberrometric measures were significantly improved. Statistical analysis of the subjective patients' responses showed a significant acceptance of the lens by most of them. At the end of follow-up, the mean wearing time was 9.9 ± 2.9 hours per day. The most common cause of wearing discontinuation was persistent discomfort (16.7%) and high lens expenses(16.7%). Self-assessed questionnaire showed statistically significant improvement in nearly all measured subjective parameters.

CONCLUSION

Rose K2 XL lenses provide patients with irregular cornea with both quantitative and qualitative optimal visual function with high degree of patient comfort and satisfaction.

[Results of corneal crosslinking for pellucid marginal corneal degeneration]

AIM

to evaluate the clinical effectiveness of crosslinking in patients with progressive pellucid marginal corneal degeneration (PMCD).

MATERIAL AND METHODS

A total of 9 patients (16 eyes) with progressive PMCD were treated by standard crosslinking. The cornea was saturated with Dextralink solution and UV-A irradiated at 3 mW/cm2 for 30 minutes. The follow-up period was 12 months.

RESULTS

One month after treatment, there was a slight decrease in uncorrected and best corrected visual acuity (UCVA and BCVA) - from 0.08±0.03 and 0.4±0.15 preoperatively down to 0.06±0.02 and 0.3±0.07, respectively, caused by pseudohaze of the cornea. Keratometric parameters (the average refractive power of the cornea, corneal astigmatism, and corneal thickness) did not change significantly. The demarcation line was identified in 56% of cases. By the 3-month follow-up, UCVA and BCVA improved up to 0.1±0.07 and 0.52±0.1, respectively. The refractive power of the cornea decreased by 2.0 diopters and corneal astigmatism - by 0.7 diopters reaching 46.8±2.7 and 5.1±1.3 diopters, respectively (p≤0.04). Central corneal thickness decreased by an average of 29 microns. The demarcation line remained visible in 25% of cases. At 6 months, BCVA averaged 0.58±0.13, at that, 56% of eyes gained 1 line and 31% - 2 lines. The refractive power of the cornea decreased down to 45.7±1.6 diopters, corneal astigmatism - down to 4.8±1.5 diopters. The demarcation line was not detected. At 1 year, there were no significant changes in the average values of optometric indices as compared to the 6-month period. Сonclusion. Pellucid marginal corneal degeneration should be regarded as a kind of primary ectasia, often bilateral and notable for its characteristic clinical picture and late onset. In progressive disease, photochemical crosslinking of the cornea contributes to the improvement of optometric parameters and stabilization of the process.

Full-Ring Intracorneal Implantation in Corneas With Pellucid Marginal Degeneration

BACKGROUND

Keratoconus (KCN) is a progressive, non-inflammatory ectacic disorder characterized by bilateral and asymmetrical conical protrusion of the cornea. MyoRing implantation and Collagen Crosslink (CXL) are two separate effective treatments for all stages of keratoconous. This study wants to show the effect of these treatments combination in patients with moderate and severe keratoconus.

OBJECTIVES

The aim of this study was to report on the visual and refractive outcomes of corneas with pellucid marginal degeneration following MyoRing implantation (DIOPTEX GmbH).

PATIENTS AND METHODS

This study included 15 eyes of 15 patients, with an age range from 22 to 49 years old, and pellucid marginal degeneration. An intrastromal corneal ring (MyoRing) was inserted by the means of mechanical dissection using a PocketMaker microkeratome. The main outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, and keratometry readings. The mean postoperative follow-up was ten months (range 6 - 12 months).

RESULTS

The mean UDVA (LogMAR) improved significantly from 1.13 ± 0.21 preoperatively to 0.24 ± 0.13 postoperatively (P < 0.001), and the mean CDVA (LogMAR) improved significantly from 0.39 ± 0.12 to 0.19 ± 0.09 (P < 0.001). The mean cylinder of manifest refraction decreased significantly by 4.00 diopter (D) (P < 0.001). The mean spherical equivalent error (SE) decreased significantly from -6.00 ± 3.60 D to -0.70 ± 1.90 D, at the end of the follow-up period. Furthermore, with regards to corneal topography, a significant reduction was observed in keratometric values. The Kmax, Kmin and Kaverage decreased significantly by 5.00, 1.10 and 4.00 D, respectively (P < 0.001).

CONCLUSIONS

MyoRing implantation using the PocketMaker microkeratome appears to provide an effective method for treating pellucid marginal degeneration. Both UDVA and CDVA improved significantly. The corneal steepening and astigmatism were reduced in all subjects after MyoRing implantation.

Reshaping procedures for the surgical management of corneal ectasia

Corneal ectasia is a progressive, degenerative, and noninflammatory thinning disorder of the cornea. Recently developed corneal reshaping techniques have expanded the treatment armamentarium available to the corneal specialist by offering effective nontransplant options. This review summarizes the current evidence base for corneal collagen crosslinking, topography-guided photorefractive keratectomy, and intrastromal corneal ring segment implantation for the treatment of corneal ectasia by analyzing the data published between the years 2000 and 2014.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Corneal Collagen Cross-Linking in Pellucid Marginal Degeneration: 2 Patients, 4 Eyes

Purpose. To report the long-term results of corneal collagen cross-linking (CXL) with riboflavin and ultraviolet-A irradiation in 4 eyes of 2 patients affected by pellucid marginal degeneration (PMD). Methods. This study involved the retrospective analysis of 4 eyes of 2 patients with PMD that underwent CXL treatment. Of the eyes, three had only CXL treatment and one had CXL treatment after an intrastromal corneal ring segment implantation. We have pre- and postoperatively evaluated uncorrected distance visual acuity (UDVA), best corrected distance visual acuity (BCDVA), corneal topography (Pentacam), specular microscopy, and pachymetry. Results. Patient 1 was a woman, aged 35, and Patient 2 was a man, aged 33. The right eye of Patient 1 showed an improvement in her BCDVA, from 16/40 to 18/20 in 15 months, and her left eye improved from 12/20 to 18/20 in 20 months. Patient 2's right eye showed an improvement in his BCDVA, from 18/20 to 20/20 in 43 months, and his left eye improved from 16/20 to 18/20 in 22 months. No complications were recorded during or after the treatment. Conclusion. CXL is a safe tool for the management of PMD, and it can help to stop the progression of this disease.

Outcome of complete intrastromal ring implantation using femtosecond laser in pellucid marginal degeneration

PURPOSE

To evaluate the effect of complete intrastromal corneal ring implantations on patients with pellucid marginal degeneration (PMD).

DESIGN

Prospective interventional case series.

PATIENTS AND METHODS

Thirty-three eyes with PMD were included into the study. After pocket creation with femtosecond laser (Femtec; 20/10 PerfectVision), MyoRing implantation was performed. Uncorrected and corrected distance visual acuity (UDVA, CDVA), subjective refraction, keratometry, central corneal thickness, corneal biomechanical profile (Ocular Response Analysis), and whole-eye wavefront aberrometry (iTrace) were evaluated preoperatively and also postoperatively, 1 month, 3 months, 6 months, and 1 year after the operation.

RESULTS

One month after surgery, significant improvements were observed in UDVA (ANOVA; P=0.02), mean keratometry, sphere (ANOVA; P <0.001), and cylinder (ANOVA; P=0.04) with no significant changes afterwards. No significant change occurred in the corneal biomechanical profile. Primary coma and trefoil reduced after 1 year (ANOVA; P values were 0.02 and 0.06, respectively). Primary spherical aberration significantly increased according to the 1-year follow-up (ANOVA; P<0.001). No significant complication was observed.

CONCLUSION

MyoRing is considered as a treatment modality for spherocylindrical correction in patients with PMD, with an acceptable safety and efficacy profile.

[Intacsintracorneal ring segments in keratoconus]

INTRODUCTION

The spectrum of stage-related therapy of keratoconus has been broadened through surgical implantation of intracorneal ring segments (INTACS) as a possible method of reducing irregular astigmatism, leading to a reduction of corneal grafts especially in young, working-aged patients with keratoconus. The purpose of the present study was to evaluate the preoperative and postoperative results of femtosecond laser-assisted implantation of INTACS in ectatic corneal diseases.

PATIENTS AND METHODS

From August 2011 to January 2013, 20 eyes from 16 patients with a clear cornea in the visual axis suffering from hard contact lens intolerance underwent surgery in the Homburg/Saar Keratoconus Center (HKC) by the same surgeon (MEH). Among these were 16 keratoconus eyes, 1 eye with pellucid marginal degeneration und 3 eyes with post-LASIK iatrogenic keratectasia. The insertion of the INTACS ring segments was achieved by a femtosecond laser-assisted procedure that created a precise 360° tunnel at a depth of 80% of the corneal thickness (395.8 ± 38.5 μm) in the 6–7 mm zone.Results. At 6 months follow-up mean uncorrected distance visual acuity improved from 0.07 ± 0.07 preoperatively to 0.6 ± 0.26 postoperatively. Mean best-corrected distance visual acuity changed from 0.4 ± 0.15 preoperatively to 0.9 ± 0.29 postoperatively. Mean sphere decreased from −7.6 ± 6.1 dpt to −1.4 ± 2.8 dpt. Astigmatism decreased from −6.0 ± 2.8 dpt preoperatively to −4.3 ± 2.0 dpt postoperatively. There was also a reduction in the mean flat K from 47.8 ± 4.7 dpt preoperatively to 44.2 ± 5.0 dpt postoperatively and in mean steep K from 51.9 ± 5.0 dpt to 48.4 ± 6.6 dpt. The central eccentricity index in the Pentacam was reduced to around 50%. Neither intraoperative nor postoperative complications (including non-responders) were observed.

CONCLUSIONS

The femtosecond laser-assisted INTACS implantation provides a valid alternative to early keratoplasty for keratoconus patients with a clear central cornea and contact lens intolerance. It is a minimally invasive and reliable method for stage-related surgical management of keratoconus.

Efficacy of intacs intrastromal corneal ring segment relative to depth of insertion evaluated with anterior segment optical coherence tomography

AIM

To evaluate the effect of implantation depth of Intacs microthin prescription inserts (Addition Technology Inc, Fremont, California) on visual and topographic outcomes in patients with post- laser-assisted in situ keratomileusis (LASIK) ectasias.

SETTINGS AND DESIGN

Retrospective, observational case series.

MATERIALS AND METHODS

In this case series, 16 eyes of 12 patients were evaluated. All cases were post-LASIK ectasia that had undergone intrastromal corneal ring segment (ICRS) implantation. The planned insertion depth was 70% of stromal thickness using a manual dissector. At least 12 months postoperatively, all eyes underwent Visante (Carl Zeiss Meditec) AS-OCT to determine insertion depth. Cases were categorized into 3 groups based on the measured implantation depth: 40-59% thickness; 60-79% thickness; and ≥80% thickness. Visual, refractive and topographic outcomes were evaluated relative to implantation depth.

RESULTS

The lowest improvement in the study parameters ocurred when the implantation depth was ≥80%. In this group, uncorrected visual acuity (UCVA) and best spectacle corrected VA (BSCVA) improved less than 0.5 lines. Manifest refractive spherical equivalent (MRSE) and mean keratometry (Km) change was less than 0.5 diopters (D). The greatest improvements were observed with implantation depth of 60-79% where UCVA and BSCVA increased by 4.5 and 2.5 lines respectively, and MRSE and Km changed by approximately 2.00 D. Less improvement was found when ICRS were implanted between 40-59% of stromal thickness.

CONCLUSION

Implantation of ICRS greater than 80% of stromal thickness may have no effect on visual and topographic status.

Deep anterior lamellar keratoplasty for pellucid marginal degeneration

PURPOSE

To present the surgical outcomes of deep anterior lamellar keratoplasty (DALK) for pellucid marginal degeneration (PMD).

METHODS

A retrospective review was performed in 16 eyes of 16 patients who underwent DALK at the King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia between January 1, 2006 and December 30, 2009. Baring of Descemet's membrane (DM) during DALK was achieved in 8 (50%) eyes; residual stroma was left intraoperatively in the remaining 8 (50%) eyes. The big bubble technique was performed in 10 (62.5%) eyes and manual dissection was performed in the remaining 6 (37.5%) eyes. Visual acuity (LogMAR notation), intraocular pressure, intraoperative complications and postoperative graft status were assessed.

RESULTS

The mean follow up was 14.6 ± 8.2 months (range 6-35 months). The mean overall age was 31.4 ± 9.6 years (range, 19-50 years). Visual acuity increased statistically significantly from 0.9 ± 0.3 (range 0.5-1.6) preoperatively to 0.4 ± 0.2 (range 0.0-0.7) at last follow-up (p < 0.0001). There was a statistically significant improvement in postoperative sphere, cylinder, and spherical equivalent (p < 0.035, p < 0.001, and p < 0.02, respectively) compared to preoperative. Postoperative visual acuity was not statistically significantly related to gender, type of surgical technique, and baring or perforation of DM. The main graft-related complication was graft-host vascularization (2/16 eyes).

CONCLUSION

DALK reduces severe corneal astigmatism and results in good visual and refractive outcomes and is an effective alternative for patients with PMD.

What's in a name: keratoconus, pellucid marginal degeneration, and related thinning disorders

PURPOSE

To discuss the implications of the current nomenclature and use of current diagnostic modalities on the classification and treatment of pellucid marginal degeneration and keratoconus.

DESIGN

Perspective analysis of the literature.

METHODS

Analysis of published reports on the various treatment methods for pellucid marginal degeneration and keratoconus, and the technologies used in these studies to support the diagnosis and classification of these ectatic disorders.

RESULTS

Many studies exploring the different treatment modalities for pellucid marginal degeneration and keratoconus rely mainly on anterior curvature maps to establish the diagnosis of these ectatic disorders, and either do not utilize or disregard information provided by pachymetric maps and posterior elevation maps. In addition, the interchangeability of the nomenclature used to describe these disorders in the literature makes it even more difficult for the clinician to determine the applicability of the results to their patient population.

CONCLUSIONS

We propose that future studies minimally include anterior and posterior elevation maps, anterior curvature topography, and full pachymetric maps. This will allow practitioners a better understanding of the study population, and allow them to ascertain when and in whom the treatment modality being explored may be applicable.

Clinical outcomes after complete ring implantation in corneal ectasia using the femtosecond technology: a pilot study

PURPOSE

To evaluate the clinical outcomes after implantation of the MyoRing (DIOPTEX GmBH, Linz, Austria) by means of femtosecond laser technology in eyes with corneal ectasia.

DESIGN

Retrospective, consecutive, nonrandomized, case series.

PARTICIPANTS

A total of 12 eyes of 11 patients with ages ranging from 17 to 50 years were included. All cases were diagnosed with corneal ectasia according to the standard criteria: 1 case of post-LASIK ectasia and 11 cases of keratoconus. All cases presented with reduced best spectacle-corrected visual acuity, contact lens intolerance or discomfort, and central corneal thickness of more than 350 μm.

METHODS

MyoRing inserts of 280 μm in thickness and 5 mm in diameter were implanted in all cases into an intrastromal corneal pocket created by means of femtosecond technology. Visual, refractive, corneal topography, and pachymetric changes were evaluated during a 6-month follow-up. In addition, corneal biomechanical changes were evaluated by means of the Ocular Response Analyzer (Reichert, Buffalo, NY).

MAIN OUTCOME MEASURES

Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, keratometry, corneal asphericity, corneal higher-order aberrations, pachymetry, corneal hysteresis (CH), and corneal resistance factor (CRF).

RESULTS

A significant improvement in UDVA was observed 1 week after surgery (P=0.001), which was consistent with the significant reduction in sphere (P=0.002) and cylinder (P=0.004). No significant changes were detected in these parameters afterward (P ≥ 0.263). Furthermore, a significant corneal flattening of a mean value of 8.03 diopters (D) was found (P=0.005). This keratometric change was correlated with the magnitude of corneal coma-like aberrations (r=0.830, P=0.003) and the CRF (r=-0.782, P=0.008). In regard to aberrometry, a statistically significant increase in primary spherical aberration was found 1 month after surgery (P=0.001). In addition, a significant reduction in higher-order corneal aberrations was found 3 to 6 months after surgery (P=0.027). Significant corneal thickening was also observed postoperatively in the central, nasal, and temporal areas (P ≤ 0.013). No statistically significant changes were detected (P ≥ 0.176) in corneal biomechanics. Explantation was performed in a very advanced keratoconus because of the extremely poor visual outcome.

CONCLUSIONS

MyoRing implantation using femtosecond technology in keratoconus allows successful corneal modeling, although the use of large diameters is advisable.

A single 210-degree arc length intrastromal corneal ring implantation for the management of pellucid marginal corneal degeneration

PURPOSE

To determine the visual and refractive outcomes of 210-degree arc length intrastromal corneal ring segment (ICRS) implantation in eyes with pellucid marginal corneal degeneration (PMCD).

DESIGN

Retrospective, consecutive case series.

METHODS

Sixteen consecutive eyes of 10 patients who underwent a single 210-degree ICRS implantation by femtosecond laser for the management of PMCD and completed at least 1 year follow-up were included. A complete ophthalmic examination was performed preoperatively and postoperatively, including uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest spherical and cylindrical refractions, spherical equivalent, and keratometric readings.

RESULTS

The mean follow-up period was 30.7 months (range 12 to 36 months). No intraoperative complication was observed. White deposits around the segments were noted in 2 of 16 eyes (12.5%) at the first postoperative year. The mean UCVA showed significant improvement, from 1.69 +/- 1.02 logarithm of the minimal angle of resolution (logMAR) preoperatively to 0.64 +/- 0.43 logMAR at the 36th month (n = 11, P < .001). The mean preoperative BSCVA was 0.88 +/- 0.68 logMAR; after 36 months, this improved to 0.35 +/- 0.34 (P < .001). At the 36th month, UCVA was improved in all eyes (n = 11, range: gain of 1 to 6 lines), whereas BSCVA was improved in 9 eyes (81.8%, range: gain of 2 to 7 lines) and remained unchanged in 2 eyes (18.1%); UCVA was 20/40 or better in 3 eyes (27%) and BSCVA was 20/40 or better in 8 eyes (72.7%). There was a significant reduction in the spherical equivalent refractive error, from -4.40 +/- 1.85 diopters (D) preoperatively to -1.86 +/- 0.60 D (P < .001), and the mean maximum keratometric power decreased from 49.70 +/- 4.32 D to 46.08 +/- 2.84 D (P < .001) after 36 months. The mean cylindrical refraction decreased from -4.39 +/- 1.86 D preoperatively to -2.38 +/- 1.35 D at 36 months (P < .001).

CONCLUSION

A single 210-degree arc length ICRS implantation using a femtosecond laser for patients with PMCD provides good visual and refractive outcomes.

Traumatic shattering of intrastromal corneal ring segments

Long-term stability of intrastromal corneal ring segments is important in maintaining patients' corrected distance visual acuity and avoiding injury to the local tissues. We report a case of traumatic shattering of intrastromal segments due to blunt trauma, with successful removal of the fragments.

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.

Management of Superior Pellucid Marginal Degeneration With a Single Intracorneal Ring Segment Using Femtosecond Laser

PURPOSE

A 26-year-old man with superior pellucid marginal corneal degeneration associated with poor visual acuity due to irregular astigmatism was treated with single-segment intracorneal ring insertion.

METHODS

Preoperatively the patient's uncorrected visual acuity (UCVA) was 0.05, best spectacle-corrected visual acuity (BSCVA) was 0.15, and manifest refraction was -4.50 x 85 in the left eye. The flattest meridian (K1) measured was 38.50 x 90 and the steepest meridian (K2) was 51.10 x 30.

RESULTS

Three months postoperatively, UCVA was 0.15, BSCVA was 0.4, and manifest refraction was -2.50 x 90.

CONCLUSIONS

The use of single Intacs with femtosecond laser to treat superior pellucid marginal corneal degeneration improved visual acuity.

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.

Dégénérescence marginale pellucide compliquée d’un hydrops cornéen aigu spontané

Pellucid marginal corneal degeneration (PMCD) is an ectatic corneal disorder characterized by a peripheral, noninflammatory band of thinning of the inferior cornea. This condition often is misdiagnosed with keratoconus, with which it shares several clinical, videotopographic, and histologic aspects. Furthermore, as with keratoconus, hydrops and spontaneous corneal perforation can occur. We report the case of a 56-year-old man with confirmed PMCD, emphasizing the diagnostic approach, the disease follow-up, and its complication in spontaneous acute corneal hydrops. Finally, regarding this case, authors collect the clinical and videotopographic characteristics of PMCD and discuss the different therapeutic options.

Pellucid marginal corneal degeneration: evaluation of the corneal surface and contact lens fitting

AIM

To quantify corneal irregularities, to describe the fitting with contact lenses, and to answer the question whether or not contact lenses with a special back surface design could improve visual acuity in patients with pellucid marginal corneal degeneration (PMCD).

METHODS

13 eyes were fitted with contact lenses with a special back surface. Videokeratographic data were assessed. The patients were followed up for an average period of 22.2 months. Lens tolerance and corrected visual acuity were evaluated.

RESULTS

The mean eccentricity did not exceed 0.7 in all patients. Either the superior or the inferior eccentricity, or both, were negative in all patients. Using Fourier analysis all PMCD subjects showed an increased irregular astigmatism of the anterior cornea. Using Zernike coefficients seven eyes (53.8%) had a higher order aberration root mean square error (HOA RMS error) out of the normal range. The visual acuity with contact lenses improved in all eyes with an average increase of 2.7 lines (maximum eight lines). No serious complications were observed.

CONCLUSIONS

Quantitative evaluation of videokeratographic data may help to diagnose PMCD and to distinguish PMCD from other ectatic corneal diseases. Contact lenses with a special back surface design can improve visual acuity and lens tolerance.

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)