Intrastromal correction of presbyopia using a femtosecond laser system

Advances in Corneal Surgical and Pharmacological Approaches to the Treatment of Presbyopia

The purpose of this article is to review the current status of presbyopia amelioration with surgical and pharmacologic procedures that partially compensate for loss of accommodation in advance of cataract surgery and lens replacement. Over the last few years, several corneal surgical and topical pharmacological approaches for the treatment of presbyopia have been introduced to the marketplace or are in the developmental pipeline. The approaches vary in invasiveness, duration of effect, reversibility, risk/benefit ratio, and clinical results. The advantages and disadvantages for each are discussed. Corneal surgical interventions aim to provide improved near and intermediate vision in patients with presbyopia through refractive means that extend ocular depth of focus through shape modification. The use of miotic drops or corneal lamellar implants extend depth of focus with the "pinhole" aperture size reduction effect. Unlike in adults younger than 40 years, the refractive status of the patient with presbyopia is not stable. Hence, procedures that provide a permanent refractive change may not provide long-term full correction; eye drops or other treatments that are self-reversing in time or are easily reversible may be used as needed. On the horizon, procedures are being explored that may add years of functional lens accommodation by preserving the deformable gel properties of the lens. [J Refract Surg. 2021;37(6 Suppl):S20-S27.].

Femtosecond Lasers in Cornea & Refractive Surgery

Since the introduction of femtosecond laser (FS) systems for corneal flap creation in laser-assisted in-situ keratomileusis there have been numerous applications for FS laser in corneal surgery. This manuscript details the utility of FS lasers in corneal surgical procedures including refractive laser surgeries, intracorneal ring segment tunnels, presbyopic treatments, and FS-assisted keratoplasty. We also review the role of FS lasers in diagnostic procedures such as two photon excitation fluorescence and second harmonic generation.

Presbyopic Excimer Laser Ablation: A Review

PURPOSE

To provide an overview of the efficacy and safety of available presbyopic excimer laser ablation profiles.

METHODS

Literature review.

RESULTS

Monovision with excimer laser traditionally applies near correction to the non-dominant eye. Different excimer laser presbyopic approaches include the increase in depth of focus, through the controlled change of spherical aberration or asphericity, or multifocal ablation patterns with central or peripheral near vision zones. The studies investigating different excimer laser ablation patterns applied in previously myopic eyes revealed high levels of efficacy with all ablation profiles (between 68% and 99% achieving binocular uncorrected distance visual acuity [UDVA] of 20/25 or better, and between 70% and 100% achieving uncorrected near visual acuity [UNVA] presenting J3 or better). In hypermetropic eyes, most of the studies revealed high levels of efficacy with different platforms (between 78% and 100% achieving binocular UDVA of 20/25 or better and between 70% and 100% achieving UNVA presenting J3 or better). Loss of two or more lines of corrected distance visual acuity varied between 0% and 10% in the myopic eyes and between 0% and 14% in the hyperopic eyes.

CONCLUSIONS

There is evidence that excimer laser presbyopic strategies accomplish spectacle independence at reasonable levels. There are reliable and safe options for both myopic and hyperopic eyes with satisfactory outcomes regarding near and distance vision. [J Refract Surg. 2018;34(10):698-710.].

An Italian Translation and Validation of the near Activity Visual Questionnaire (NAVQ)

Purpose

To validate the Near Activity Vision Questionnaire (NAVQ) in Italian to allow the assessment of presbyopia corrections in Italian-speaking patients.

Methods

An Italian version of the NAVQ was arranged through several steps: an initial forward translation (from English to Italian), a backward translation (from Italian to English), and finally a consensual version to check against the original NAVQ. This prospective study enrolled native Italian-speaking presbyopic patients with corrected distance visual acuity of 0.20 logMAR or better in each eye and free of ocular anomalies. Six different groups of patients were asked to complete the questionnaire: emerging presbyopic patients, reading spectacle users, multifocal spectacle users, multifocal contact lens (CL) wearers, monovision CL wearers, and monofocal intraocular lens patients. Subjects were asked to answer the questionnaire again 2 weeks after the first completion.

Results

A total of 207 subjects completed the questionnaire. Data analysis showed good internal consistency (Cronbach α = 0.93) and factorial validity with only one factor explaining 62.0% of the variance. Test-retest reliability was extremely good (ICC = 0.92) as well as discriminatory power of the questionnaire's ability to discriminate between subjects with different forms of presbyopic correction.

Conclusions

The Italian version of the NAVQ matches the properties of the original English version. It is a valid instrument to evaluate near activity visual quality of presbyopic Italian speakers.

Corneal Refractive Procedures for the Treatment of Presbyopia

Purpose:

Refractive surgery has been in use for a long time and is evolving at a fast pace with several new corneal procedures being used for the correction of presbyopia. The purpose of this article is to give a comprehensive review of the literature to evaluate the outcome and success of different corneal refractive surgical procedures in presbyopic patients.

Methods:

We performed a comprehensive search on PubMed to identify published reports of the various procedures utilized in the past and present to correct presbyopia. The outcomes of these procedures were recorded.

Results and conclusion:

We found that varying rates of success have been reported with these procedures. The results of our exhaustive search are presented in this report for review.

Changes in Keratometric Values and Corneal High Order Aberrations After Hydrogel Inlay Implantation

PURPOSE

We sought to analyze surgically induced refractive change (SIRC) and change in high-order aberration after Raindrop corneal inlay insertion (ReVision Optics, Lake Forest, CA), and assess the extent to which Raindrop corneal inlay insertion could correct presbyopia.

DESIGN

Interventional case series.

METHODS

Seventeen patients were included if they had a corneal thickness ≥500 μm and a stable manifest spherical equivalent refraction between 0.50 and +1.00 diopters (D). The Raindrop corneal inlay was implanted on the stromal bed of a femtosecond laser-assisted generated flap of nondominant eyes. Manifest refraction, corneal powers, and corneal high-order aberrations were measured preoperatively and at 3 and 12 months postoperatively.

RESULTS

The SIRC by manifest refraction was 0.99 ± 0.26 D. The changes derived from simulated keratometry (K), true net power, and equivalent K reading (EKR) at 1.0-4.0 mm were greater than the SIRC (all P < .01) while the change in EKR at 6.0 mm was less than the SIRC (P < .01). The changes in EKR 5.0 mm, automated K, and EKR 4.5 mm did not differ significantly from the SIRC (P = .81, .29, and .09, respectively), and the difference was the least for EKR 5.0 mm. In analysis of high-order aberrations, only spherical aberration showed statistically significant difference between preoperative and postoperative on both anterior cornea and total cornea (all P < .01).

CONCLUSION

Raindrop corneal inlay corrects presbyopia via increasing negative spherical aberration. The equivalent K reading at 5.0 mm accurately reflected the SIRC, and would be applicable for intraocular power prediction before cataract surgery.

Assessment of contrast sensitivity loss after intrastromal femtosecond laser and LASIK procedure

AIM

To assess the loss of contrast sensitivity (CS) function for INTRACOR or intrastromal femtosecond laser presbyopia procedure to conventional LASIK procedures.

METHODS

Patients were recruited from a refractive surgery center for either INTRACOR or conventional LASIK. INTRACOR was performed on 8 eyes and LASIK was performed for 40 eyes in an overlapping period. Pre-operative evaluation and post-operative follow up for up to three months was done. Drops of CS in 4 spatial frequency (3 cpd, 6 cpd, 12 cpd and 18 cpd) right before and 3mo after the surgery were compared by Wilcoxon signed ranks test.

RESULTS

For INTRACOR, CS threshold showed significant drop at both glare and non-glare condition, the drop was seen in all 4 spatial frequency. The averaged loss over the 4 spatial frequencies 3mo after surgery was 1.18 for non-glare and 0.71 for glare. For LASIK the CS threshold drop was most significant in 12 cpd for glare.

CONCLUSION

INTRACOR procedure produces a gain of near vision for presbyopia patients but also introduces a high lost of contrast sensitivity plus worsen of vision quality. Pre-surgical patient selection and advise should be given with specific regards to night driving and glare conditions.

Keratectasia After Presbyopia Treatment With INTRACOR

PURPOSE

To report a case of keratectasis of a patient underwent INTRACOR presbyopic treatment 5 years ago.

METHODS

Case Report.

RESULTS

Fifty-eight-year-old gentleman had presented with deteriorating vision in his left eye. He reported undergoing INTRACOR presbyopic treatment in that eye 5 years ago. At presentation, his best-corrected visual acuity was 20/40. Slit-lamp examination of the left eye showed an ectatic cornea with concentric corneal scars. Corneal topography revealed marked keratectasia, with significant anterior and posterior elevations. The area of maximal corneal thinning coincided with the site of maximal elevation. Patient was fitted with hybrid contact lenses as a temporary treatment option and his best-corrected visual acuity improved to 20/30.

CONCLUSIONS

INTRACOR is one of the newer modalilities to correct presbyopia. One must be aware of the complication such as corneal ectasia after this presbyopic treatment.

Apparent Corneal Ectasia After Bilateral Intrastromal Femtosecond Laser Treatment for Presbyopia

PURPOSE

To report a case of apparent corneal ectasia after intrastromal femtosecond laser treatment for presbyopia (INTRACOR).

METHODS

A healthy 56-year-old male with low hyperopia underwent an unremarkable bilateral INTRACOR procedure in March/April 2011. The patient was discharged after follow-up and returned 5 years later.

RESULTS

Before discharge, the monocular logarithm of the minimal angle of resolution uncorrected distance visual acuity (UDVA) values were R, 0.0 and L, 0.10. In both eyes near (UNVA) visual acuities were 0.0. There were signs of slight posterior central corneal steepening without loss of corneal stability. Five years postop, monocular UDVA and UNVA values were 0.4 and 0.0, respectively. Ectasia was observed in both eyes, and the centrally placed 5 concentric rings after the INTRACOR procedure were visible under slit-lamp biomicroscopy.

CONCLUSIONS

There is no clear reason to explain why the patient developed bilateral corneal steepening. It could be that the patient's corneal stromal fibers gradually weakened over this 5-year period.

Advances in femtosecond laser technology

Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures.

Early-onset methicillin-resistant Staphylococcus aureus keratitis and late-onset infectious keratitis in astigmatic keratotomy incision following femtosecond laser-assisted cataract surgery

A 79-year-old woman had uneventful femtosecond laser-assisted cataract surgery including paired laser astigmatic keratotomies (AKs) in the right eye. Three weeks postoperatively, a corneal infiltrate developed in the superotemporal AK incision. Cultures grew methicillin-resistant Staphylococcus aureus. The infection was treated with topical fortified vancomycin and tobramycin; full resolution required several months of therapy. Five months after cataract surgery, the patient presented with a second stromal infiltrate, also in the superotemporal AK incision. Despite negative cultures, the infiltrate resolved quickly on a short course of broad-spectrum fortified antibiotics. At 6 months, the corrected distance visual acuity was 20/30. This case demonstrates that infectious keratitis can occur following uneventful femtosecond laser-assisted AK performed concurrently with cataract surgery. We reviewed the literature on infectious keratitis following refractive keratotomy and femtosecond laser-assisted procedures. Several recommendations to prevent these infections are proposed.

FINANCIAL DISCLOSURE

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

The evolution of corneal and refractive surgery with the femtosecond laser

The use of femtosecond lasers has created an evolution in modern corneal and refractive surgery. With accuracy, safety, and repeatability, eye surgeons can utilize the femtosecond laser in almost all anterior refractive procedures; laser in situ keratomileusis (LASIK), small incision lenticule extraction (SMILE), penetrating keratoplasty (PKP), insertion of intracorneal ring segments, anterior and posterior lamellar keratoplasty (Deep anterior lamellar keratoplasty (DALK) and Descemet's stripping endothelial keratoplasty (DSEK)), insertion of corneal inlays and cataract surgery. As the technology matures, it will push surgical limits and open new avenues for ophthalmic intervention in areas not yet explored. As we witness the transition from femto-LASIK to femto-cataract surgery it becomes obvious that this innovation is here to stay. This article presents some of the most relevant advances of femtosecond lasers to modern corneal and refractive surgery.

Femtosecond laser in refractive and cataract surgeries

In the past few years, 9 unique laser platforms have been brought to the market. As femtosecond (FS) laser-assisted ophthalmic surgery potentially improves patient safety and visual outcomes, this new technology indeed provides ophthalmologists a reliable new option. But this new technology also poses a range of new clinical and financial challenges for surgeons. We provide an overview of the evolution of FS laser technology for use in refractive and cataract surgeries. This review describes the available laser platforms and mainly focuses on discussing the development of ophthalmic surgery technologies.

A review of the surgical options for the correction of presbyopia

Presbyopia is an age-related eye condition where one of the signs is the reduction in the amplitude of accommodation, resulting in the loss of ability to change the eye's focus from far to near. It is the most common age-related ailments affecting everyone around their mid-40s. Methods for the correction of presbyopia include contact lens and spectacle options but the surgical correction of presbyopia still remains a significant challenge for refractive surgeons. Surgical strategies for dealing with presbyopia may be extraocular (corneal or scleral) or intraocular (removal and replacement of the crystalline lens or some type of treatment on the crystalline lens itself). There are however a number of limitations and considerations that have limited the widespread acceptance of surgical correction of presbyopia. Each surgical strategy presents its own unique set of advantages and disadvantages. For example, lens removal and replacement with an intraocular lens may not be preferable in a young patient with presbyopia without a refractive error. Similarly treatment on the crystalline lens may not be a suitable choice for a patient with early signs of cataract. This article is a review of the options available and those that are in development stages and are likely to be available in the near future for the surgical correction of presbyopia.

Current management of presbyopia

Presbyopia is a physiologic inevitability that causes gradual loss of accommodation during the fifth decade of life. The correction of presbyopia and the restoration of accommodation are considered the final frontier of refractive surgery. Different approaches on the cornea, the crystalline lens and the sclera are being pursued to achieve surgical correction of this disability. There are however, a number of limitations and considerations that have prevented widespread acceptance of surgical correction for presbyopia. The quality of vision, optical and visual distortions, regression of effect, complications such as corneal ectasia and haze, anisometropia after monovision correction, impaired distance vision and the invasive nature of the currently techniques have limited the utilization of presbyopia surgery. The purpose of this paper is to provide an update of current procedures available for presbyopia correction and their limitations.

Developments in the correction of presbyopia II: surgical approaches

PURPOSE

To discuss the various static and dynamic surgical approaches which attempt to give presbyopes good vision at far, intermediate and near viewing distances.

CONTENT

Static methods broadly adopt the same optical techniques as those used in presbyopic contact lens correction and aim to satisfy the needs of the presbyope by increasing binocular depth-of-focus, often using monovision as well as simultaneous-imagery. Dynamic methods generally attempt to make use of at least some of the still-active elements of the accommodation system. They include procedures which are supposed to modify the relative geometry of the ciliary muscle and lens, or which reduce the stiffness of the presbyopic lens either by replacing it with other natural or man-made material or by subjecting it to femtosecond laser treatment. Alternatively the natural lens may be replaced by some form of intraocular lens which changes power as a result of forces derived from the still-active ciliary muscle, zonule and capsule, or other sources.

CONCLUSIONS

At present, multifocal intraocular lenses appear to offer the most consistent and reliable surgical approach to surgical presbyopic correction. They have obvious advantages in convenience and stability over optically-similar, simultaneous-image presbyopic contact lenses but this must be balanced against their relative inflexibility in cases of patient dissatisfaction. Dynamic methods remain largely experimental. Although some approaches show promise, as yet no method has demonstrated a reliable, long-term ability to correct distance refractive error and to appropriately change ocular power in response to changes in viewing distance over the normal range of interest.

Effectiveness and safety of femtosecond laser-assisted lens fragmentation and anterior capsulotomy versus the manual technique in cataract surgery

PURPOSE

To evaluate the effectiveness and safety of cataract surgery using femtosecond laser-assisted lens fragmentation and anterior capsulotomy versus manual cataract surgery.

SETTING

MaxiVision Eye Hospital, Begumpet, Hyderabad, India.

DESIGN

Randomized controlled open-label multisurgeon prospective trial.

METHODS

Patients (at least 18 years old) were randomized to femtosecond laser-assisted lens prefragmentation and capsulotomy or manual capsulorhexis and standard phacoemulsification. Measured outcomes were effective phacoemulsification time (EPT), surgeon-assessed ease of phacoemulsification, mean phaco energy, mean phaco time, balanced salt solution volume, capsulotomy precision, and adverse event rates.

RESULTS

Fifty-six eyes had the femtosecond laser procedure, and 63 had manual cataract surgery. The mean EPT was significantly lower in the laser group (5.2 seconds ± 5.7 [SD]) than in the manual group (7.7 ± 6.0 seconds) (P=.025). There was a significant difference in the mean phaco energy between the 2 groups (13.8% ± 10.3% in laser group; 20.3% ± 8.1% in manual group) (P<.001). There were no significant between-group differences in the ease of phacoemulsification, mean phaco time, or balanced salt solution volume. Laser-assisted capsulotomies were significantly more accurate and precise (intended diameter, circularity, centration) (P<.01). The safety profiles of the procedures were equivalent, with no adverse events at the 1-day follow-up.

CONCLUSION

The femtosecond laser platform was effective and safe in cataract surgery, reducing EPT and the mean phaco energy during lens fragmentation and providing precise and reproducible capsulotomies.

Past and present of corneal refractive surgery: a retrospective study of long-term results after photorefractive keratectomy and a prospective study of refractive lenticule extraction

Surgical correction of refractive errors is becoming increasingly popular. In the 1990s, the excimer laser revolutionized the field of corneal refractive surgery with PRK and LASIK, and lately refractive lenticule extraction (ReLEx) of intracorneal tissue, using only a femtosecond laser, has become possible. Two new procedures were developed, ReLEx flex (FLEX) and ReLEx smile (SMILE). Until this thesis, only a few long-term studies of PRK with a relatively limited number of patients had been published; therefore, this thesis intended to retrospectively evaluate long-term outcomes after PRK for all degrees of myopia for a large number of patients. Furthermore, a prospective contralateral eye study comparing FLEX and SMILE, when treating high to moderate degrees of myopia, had not been performed prior to this study. This was the second aim of this thesis. In the first study, results from 160 PRK patients (289 eyes) were presented. Preoperative spherical equivalent ranged from -1.25 to -20.25 D, with 78% having low myopia (<-6 D). Average follow-up time was 16 years (range 13-19 years), making this the longest published follow-up study on PRK patients. Outcomes from eyes with low myopia were generally superior to outcomes from eyes with high myopia, at final follow-up. Seventy-two percent were within ± 1.00 D of target refraction, as compared to 47% of eyes with high myopia. However, results from a subgroup of unilateral treated PRK patients indicated that refraction at final follow-up was affected by myopic progression. Fifty percent of eyes with low myopia had uncorrected 20/20 distance visual acuity or better, as compared to 22% of eyes with high myopia. Haze did not occur if attempted corrections were <-4 D, and only eyes with high myopia lost two lines or more of CDVA (corrected distance visual acuity). Eighty-one per cent were satisfied or very satisfied with their surgery.

CONCLUSION

The results support the continued use of the excimer laser for corneal surface ablation as a treatment option for correction of low degrees of myopia, and as the treatment of choice for subgroups of refractive patients (thin corneas, etc.). The results also highlight that treatment of higher degrees of myopia with standard PRK should only be done today under special circumstances, due to low refractive predictability, and high risk of corneal haze. Technological advances since then should be taken into account when comparing these results with contemporary techniques. In the second study, 35 patients were randomized to receive FLEX in one eye and SMILE in the other. Preoperative spherical equivalent refraction ranged from -6 to -10 D with low degrees of astigmatism. A total of 34 patients completed the 6 month follow-up period. Refractive and visual outcomes were very similar for the two methods, as well as tear film measurements and changes in corneal biomechanics. Ninety-seven percent were within ± 1.00 D of target refraction, no eyes lost two lines or more of CDVA, and contrast sensitivity was unaffected after both procedures. The changes in higher-order aberrations were also very similar. There were also no differences in tear film parameters 6 months after surgery, although less postoperative foreign body sensation was reported within the first week after surgery in SMILE eyes. Corneal sublayer pachymetry measurements demonstrated equally increased epithelial thickness 6 months after surgery. Contrary to expectations, it was not possible to measure the theoretical biomechanical advantages of a small corneal incision in SMILE as compared to a corneal flap in FLEX. The main differences between FLEX and SMILE were found when the corneal nerves and intraoperative complications were evaluated. Thus, corneal sensitivity was better preserved and corneal nerve morphology was less affected after SMILE, but intraoperative complications occurred more frequently, although without visual sequela. Finally, 97% were satisfied or very satisfied with both their surgeries.

CONCLUSION

The results support the continued use of both FLEX and SMILE for treatment of up to high degrees of myopia. Overall, refractive and visual results for both procedures were good and similar, but from a biological point of view, the less invasive SMILE technique is more attractive, as demonstrated in this study, despite being slightly more surgically demanding than FLEX.

Corneal ectasia after intrastromal presbyopic surgery

PURPOSE

To report histopathologic findings in a case of bilateral corneal ectasia following intrastromal femtosecond laser presbyopia surgery.

METHODS

Case report.

RESULTS

A 56-year-old patient was referred for bilateral corneal ectasia. He was treated for hyperopia using LASIK twice in both eyes. A bilateral femtosecond laser intrastromal presbyopia correction was secondarily performed. The patient complained of progressive loss of distance visual acuity shortly after. Corneal topography showed a bilateral central corneal protrusion. Rigid contact lenses were successfully fitted on the right eye and, because the patient still complained, a deep anterior lamellar keratoplasty was performed in the left eye. Light and electronic microscopy of the corneal button revealed that the inner intrastromal incision crossed the LASIK interface and led to stromal bed dehiscence.

CONCLUSION

This case illustrates that intrastromal refractive surgery should not be recommended in eyes previously treated by lamellar refractive surgery.

Presbyopic correction on the cornea

Purpose

The aim of this systematic review was to synthesize and appraise the evidence of the benefits of presbyopic correction on the cornea for visual function.

Summary

Comprehensive search was conducted in MEDLINE using keywords like “presbylasik”, “presbyopic refractive surgery”, “corneal pseudoaccommodation” and “corneal multifocality”. We reviewed corrected and uncorrected visual acuities for distance and near (uncorrected distance visual acuity (UDVA), uncorrected near visual acuity (UNVA), corrected distance visual acuity (CDVA), distance corrected near visual acuity (DCNVA), corrected near visual acuity (CNVA)), along with the refractive outcomes in spherical equivalent (SE) and astigmatism comparing the differences observed between preoperative myopic and hyperopic patients, as well as among techniques.

Thirty-one studies met the inclusion and quality criteria. Monovision provides excellent distance and near uncorrected acuities, but with a 17% retreatment and a 5% reversal rate. Initial multifocal ablations result in 12% loss of 2 or more lines of CDVA, and a 21% retreatment rate. Laser Blended Vision provides excellent UDVA, but with a 19% retreatment rate. Initial experiences with Supracor show moderate predictability and a 22% retreatment rate. Intracor results in 9% loss of 2 or more lines of CDVA. KAMRA provides excellent UDVA, with only a 1% retreatment rate, but a 6% reversal rate. Initial experiences with PresbyMAX provided excellent UNVA and DCNVA, showing excellent predictability and a 1% reversal rate.

Conclusions

The findings have implications for clinicians and policymakers in the health-care industry and emphasize the need for additional trials examining this important and widely performed clinical procedure.

Advances in Refractive Surgery

PURPOSE

The objective of this study was to review advances in the field of refractive surgery as reported in the peer-reviewed literature over the previous year.

DESIGN

This was a literature review.

METHODS

We conducted a PubMed search for terms related to refractive surgery and reviewed prominent international ophthalmic journals published from May 2012 through April 2013. All pertinent articles were reviewed, and selected articles with the greatest relevance were included.

RESULTS

Many studies over the previous year have highlighted progress in the field of refractive surgery; topics included keratoconus screening, photorefractive keratectomy and laser in situ keratomileusis, corneal cross-linking, small-incision lenticule extraction, phakic intraocular lenses, corneal inlays, presbyopic corneal treatments, and femtosecond laser-assisted astigmatic keratotomy.

CONCLUSIONS

The field of refractive surgery continues to provide exciting developments. Improvements in established procedures and promising new surgical options make the current climate an appealing one for refractive surgeons and patients.

Keratectasia after treating presbyopia with INTRACOR followed by SUPRACOR enhancement

PURPOSE

To report a case of unilateral keratectasia after INTRACOR, which was followed by an additional excimer LASIK enhancement with a new presbyopia-correcting ablation profile.

METHODS

The non-dominant eye of a 49-year-old man with emmetropia was treated with the INTRACOR procedure using the Technolas femtosecond laser (Technolas Perfect Vision GmbH, Munich, Germany) for presbyopia. Neither eye had risk factors for keratectasia. Two years later, a presbyopia-correcting LASIK (SUPRACOR LASIK; Technolas Perfect Vision GmbH) enhancement was performed in the same eye because of deteriorated distance and near visual acuity.

RESULTS

The eye treated with INTRACOR followed by SUPRACOR LASIK developed marked keratectasia topographically limited to the area altered by INTRACOR, whereas the fellow eye remained stable and still has no signs of keratoconus.

CONCLUSIONS

This case emphasizes the incomplete knowledge of the risk factors for keratectasia following INTRACOR alone and in combination with a SUPRACOR LASIK enhancement. It also suggests that the combined weakening effect of both procedures on corneal mechanical stability may be too strong even in the absence of established risk factors for LASIK surgery.

In vivo biocompatibility of two PEG/PAA interpenetrating polymer networks as corneal inlays following deep stromal pocket implantation

This study compared the effects of implanting two interpenetrating polymer networks (IPNs) into rabbit corneas. The first (Implant 1) was based on PEG-diacrylate, the second (Implant 2) was based on PEG-diacrylamide. There were inserted into deep stromal pockets created using a manual surgical technique for either 3 or 6 months. The implanted corneas were compared with normal and sham-operated corneas through slit lamp observation, anterior segment optical coherence tomography, in vivo confocal scanning and histological examination. Corneas with Implant 1 (based on PEG-diacrylate) developed diffuse haze, ulcers and opacities within 3 months, while corneas with Implant 2 (based on PEG-diacrylamide) remained clear at 6 months. They also exhibited normal numbers of epithelial cell layers, without any immune cell infiltration, inflammation, oedema or neovascularisation at post-operative 6 month. Morphological studies showed transient epithelial layer thinning over the hydrogel inserted area and elevated keratocyte activity at 3 months; however, the epithelium thickness and keratocyte morphology were improved at 6 months. Implant 2 exhibited superior in vivo biocompatibility and higher optical clarity than Implant 1. PEG-diacrylamide-based IPN hydrogel is therefore a potential candidate for corneal inlays to correct refractive error.

Femtosecond laser technology in corneal refractive surgery: a review

PURPOSE

To discuss current applications and advantages of femtosecond laser technology over traditional manual techniques and related unique complications in corneal refractive surgical procedures, including LASIK flap creation, intracorneal ring segment implantation, astigmatic keratotomy, presbyopic treatments, and intrastromal lenticule procedures.

METHODS

Literature review.

RESULTS

From its first clinical use in 2001 for LASIK flap creation, femtosecond lasers have steadily made a place as the dominant flap-making technology worldwide. Newer applications are being evaluated and are increasing in their frequency of use.

CONCLUSIONS

Femtosecond laser technology is rapidly becoming a heavily utilized tool in corneal refractive surgical procedures due to its reproducibility, safety, precision, and versatility.

[Intrastromal femtosecond laser-based presbyopia correction]

The surgical correction of presbyopia is gaining more and more popularity in the field of refractive surgery. Besides intraocular treatment with multifocal or accommodative intraocular lenses more and more corneal laser approaches are being established. These are performed either with the Excimer laser as laser in situ keratomileusis (LASIK) or the femtosecond laser. The femtosecond laser treatment is done purely intrastromally without dissection of the epithelium and is characterized by an extremely low risk of infection and inflammation. The procedure leads to a central corneal steepening with more prolate shape and increase in depth of field. This leads to a better uncorrected near visual acuity, however, corrected distance visual acuity might be reduced due to these changes.

Corneal stromal ablation with femtosecond ultraviolet pulses in rabbits

PURPOSE

To determine the effectiveness of femtosecond ultraviolet (UV) pulses in ablating corneal stroma in a rabbit model and to compare the healing response between eyes treated with femtosecond UV pulses and eyes treated with standard excimer photorefractive keratectomy.

SETTING

Laser Research Center, Vilnius University, Vilnius, Lithuania.

DESIGN

Experimental study.

METHODS

Myopic photoablation using a femtosecond UV solid-state laser system was applied to corneas of pigmented rabbits. Experiments in 16 eyes were performed for optimization of the laser system parameters (fluence, spot size, pulse repetition rate) and calibration of ablation rate. In 7 rabbits, deep femtosecond UV ablation (∼130 μm) in 1 eye and shallow ablation (∼30 μm) in the contralateral eye were performed. Nine rabbits received an approximately 30 μm ablation with femtosecond UV pulses in 1 eye and with a conventional excimer system in the contralateral eye. Two eyes were used as controls. The ablation process and surface-temperature dynamics were monitored and recorded. Surface quality and haze development were evaluated. Rabbits were humanely killed 0 to 6 months after surgery, and eyes were enucleated for histological examination.

RESULTS

Rabbit corneas ablated with femtosecond UV pulses or excimer laser radiation were similar in terms of the corneal wound-healing process, surface quality, and histology.

CONCLUSIONS

The experiments indicate the feasibility of clinical application of femtosecond UV lasers for stromal ablation. The ability to switch between laser harmonics allows fast changeover from infrared to the UV mode, implying that a wide range of ophthalmic procedures can be performed using a single solid-state laser device.

FINANCIAL DISCLOSURE

Ms. Gabryte and Mr. Danielius are paid employees of Light Conversion Ltd. Mr. Danielius is a shareholder of Light Conversion Ltd. No other author has a financial or proprietary interest in any material or method mentioned.

Surgical management of presbyopia

Presbyopia, the gradual loss of accommodation that becomes clinically significant during the fifth decade of life, is a physiologic inevitability. Different technologies are being pursued to achieve surgical correction of this disability; however, a number of limitations have prevented widespread acceptance of surgical presbyopia correction, such as optical and visual distortion, induced corneal ectasia, haze, anisometropy with monovision, regression of effect, decline in uncorrected distance vision, and the inherent risks with invasive techniques, limiting the development of an ideal solution. The correction of the presbyopia and the restoration of accommodation are considered the final frontier of refractive surgery. The purpose of this paper is to provide an update about current procedures available for presbyopia correction, their advantages, and disadvantages.

LASIK for presbyopia correction in emmetropic patients using aspheric ablation profiles and a micro-monovision protocol with the Carl Zeiss Meditec MEL 80 and VisuMax

PURPOSE

To evaluate the monocular and binocular visual outcomes of LASIK with an aspheric micro-mono-vision protocol in emmetropic patients with presbyopia.

METHODS

A retrospective, noncomparative case series included 296 eyes from 148 consecutive emmetropic patients with presbyopia who were treated with LASIK-induced micro-monovision. The CRS-Master software was used to generate ablation profiles for the MEL 80 excimer laser (Carl Zeiss Meditec) and flaps were created using the VisuMax femtosecond laser (Carl Zeiss Meditec). The target refraction was plano for distance eyes (dominant eye) and between -1.00 and -1.88 diopters (D) for near eyes. Patients were followed for 1 year. Emmetropia was defined for inclusion as spherical equivalent refraction ⩾- 0.88 D, sphere ⩽+1.00 D, and cylinder ⩽1.25 D. Median patient age was 55 years (range: 44 to 65 years). Median follow-up was 12.9 months.

RESULTS

Mean deviation from intended correction was +0.02±0.35 D, with 91% within ±0.50 D and 100% within ±1.00 D. Of distance eyes, 95% achieved uncorrected distance visual acuity (UDVA) of 20/20 or better and 100% achieved 20/32 or better. Binocularly, 98% of patients achieved UDVA of 20/20 or better and 100% achieved 20/32 or better; 96% achieved uncorrected near visual acuity of J2 and 99% could read J3 or better. No eyes lost 2 or more lines of corrected distance visual acuity. An average increase of 0.05 logMAR was noted in distance-corrected near visual acuity. A small increase occurred in mesopic contrast sensitivity (CSV-1000, VectorVision Inc) at 3 cycles per degree (cpd) (P=.016) and no change at 6, 12, or 18 cpd.

CONCLUSIONS

This aspheric micro-monovision protocol was a well-tolerated and effective procedure for treating emmetropic patients with presbyopia.

One-year visual outcomes and patient satisfaction after surgical correction of presbyopia with an intracorneal inlay of a new design

PURPOSE

To evaluate the safety and efficacy of the third-generation Kamra corneal inlay (ACI 7000PDT) implanted monocularly in corneal pockets of emmetropic presbyopic patients to improve near and intermediate vision.

SETTING

University Eye Clinic, Paracelsus Medical University, Salzburg, Austria.

DESIGN

Cohort study.

METHODS

The corneal inlay was implanted in the nondominant eye over the line of sight by creating a corneal pocket with a femtosecond laser. The minimum postoperative follow-up was 12 months. Distance, intermediate, and near visual acuities were assessed over the follow-up. Other examinations included slitlamp evaluation, central keratometry, computerized corneal topography, endothelial cell count, and central corneal thickness. Patients completed satisfaction questionnaires preoperatively and 3, 6, and 12 months postoperatively.

RESULTS

The study evaluated 24 patients. After a mean follow-up of 12 months, 92% of patients read Jaeger (J) 3 or better with the surgical eye, the mean binocular uncorrected near visual acuity improved from J5 preoperatively to J2, and the mean binocular uncorrected intermediate visual acuity was 20/20 (67% ≥ 20/20). At 12 months, the mean uncorrected distance visual acuity was 20/20 in the surgical eye and 20/16 binocularly. Patients reported no change in distance vision, and their need for reading glasses decreased significantly (P<.001). No inlay was explanted and or recentered during the reported follow-up.

CONCLUSION

The new corneal inlay was a safe and effective treatment for presbyopia over a 1-year follow-up.