Safety and efficacy of a small-aperture capsular bag–fixated intraocular lens in eyes with severe corneal irregularities

Criteria for premium intraocular lens patient selection

PURPOSE OF REVIEW

To discuss available premium intraocular lenses (IOLs), patient selection, and important considerations for each premium IOL.

RECENT FINDINGS

We review important topics and considerations for premium IOL selection: specifically, toric, extended depth of focus (EDOF), multifocal/trifocal, light adjustable lenses (LALs), and small aperture IOLs. Toric lenses are an excellent option for patients with astigmatism. However, to achieve optimal patient satisfaction, it is critical to account for the ATR astigmatism contribution from the posterior cornea and high angle alphas. Additionally, examining the ocular surface prior to placement of EDOF/multifocal IOLs is important, yet the significance of HOAs on outcomes after implantation still must be elucidated more. Finally, recent studies reveal that the small aperture lens is a good alternative for those with corneal irregularities, and second generation LALs are a great option to achieve target refractions in those with less predictable refractive outcomes, such as in Fuchs' dystrophy or in eyes with previous refractive surgery.

Incorrectly Focused Neodymium:Yttrium-Aluminum-Garnet (Nd:YAG) Laser Beam Leads to Massive Destructive Effects in Small-Aperture (Pinhole) Intraocular Lenses

INTRODUCTION

Pinhole intraocular lenses (IOLs) were developed to improve reading by compensating for loss of accommodative function. The IC-8® Apthera™ is a small-aperture presbyopia-correcting IOL that combines the proven principle of small-aperture optics with an aspheric monofocal lens to deliver a continuous range of vision for patients with cataracts from distance to near vision. Posterior capsule opacification is the most common sequela after cataract surgery. It is effectively treated by laser capsulotomy. However, if the laser beam is incorrectly focused, the IOL can be permanently damaged (pits/shots).

METHODS

In this experimental study, yttrium-aluminum-garnet (YAG) pits were purposefully created. Defects were analyzed and compared between the periphery of the ring in the clear area of the hydrophobic acrylic lens and at the carbon black (CB)-polyvinylidene fluoride (PVDF) filtering component (FilterRing™) of the pinhole lens. All defects were made using identical settings/energy levels (2.6 mJ). The damage induced to the IC-8® Apthera™ IOL was examined by low-magnification images, light microscopy, scanning electron microscopy, and micro-computed tomography (micro-CT).

RESULTS

YAG defects in the carbon black filter ring were much more severe than those in the clear zone due to the high absorption of the carbon black. Massive defects and destruction of the lens with tearing out of fragments and particles were observed. The missing volume calculated from the micro-CT reconstruction was 0.266 mm3, which is 1.6% of the entire IOL volume, or more than 1000 times the volume damaged in the largest shot in the periphery.

CONCLUSION

Based on the results, we highly recommend using the lowest possible energy levels, posterior offset setting, and circular pattern for maximum safety when performing laser capsulotomy with pinhole implants. Care should be taken to avoid creating irreversible iatrogenic defects that may affect overall quality. The safest area for performing capsulotomy seems to be the periphery of the ring segment. Video available for this article.

Effect of capsule treatment on visual acuity and quality after phacoemulsification lens implantation in myopic patients with cataract

BACKGROUND

Cataracts pose a significant clinical burden due to their complex pathogenesis. In recent years, an increase in cataracts coexisting with myopia has heightened the incidence of retinopathy and posterior vitreous detachment. Additionally, symptoms of ocular axis elongation, lens nucleus hardening, and vitreous liquefaction have become more prevalent. While conventional extracapsular cataract extraction is commonly employed, it often yields suboptimal visual outcomes. Subsequent advancements in cataract phacoemulsification and lens implantation surgeries have gained widespread acceptance for their ability to improve refraction and significantly improve uncorrected visual acuity.

AIM

To investigate the effect of capsular treatment after phacoemulsification lens implantation in myopic patients with cataract.

METHODS

We selected 110 patients (with 134 eyes) with myopia and cataracts treated. These patients were categorized into two groups: an observation group (57 patients with 70 eyes) and a control group (53 patients with 64 eyes). The control group underwent cataract phacoemulsification and lens implantation, while the observation group received a refined capsular treatment based on the control group's procedure. We assessed the differences in visual acuity and quality between the two groups before and after surgery.

RESULTS

At six months post-operation, the observation group exhibited significantly improved far vision, intermediate vision, near vision, lower objective scattering index, higher Modulation transfer function cut-off frequency, and overall vision metrics at different contrast levels (100%, 20% and 9%) compared to the control group (P < 0.05). The total score of the National Eye Institute Visual Function Questionnaire in the observation group at 6 months after operation was significantly higher than that in the control group (P < 0.05). No significant difference in the incidence of adverse reactions was observed between the observation group and control group (P > 0.05).

CONCLUSION

Capsular treatment demonstrates efficacy in improving visual acuity and quality after phacoemulsification lens implantation in myopic patients with cataracts, warranting its clinical application.

Applications of the pinhole effect in clinical vision science

The pinhole effect is commonly used to discriminate uncorrected refractive error from ocular diseases. A small aperture limits the width of light beams entering the eye, thus increasing the depth of focus. The pinhole effect has also been used in spectacles, contact lenses, corneal inlays, and intraocular lenses (IOLs) to improve reading by compensating for loss of accommodative function. Pinhole spectacles improve near visual acuity, but reduce reading speed, increase interblink interval, and decrease tear break-up time. For contact lenses and IOLs, pinhole devices are usually used in the nondominant eye, which allow compensation of various refractive errors and decrease spectacle dependence. Pinhole corneal inlays are implanted during laser in situ keratomileusis or as a separate procedure. Pinhole IOLs are gaining popularity, particularly as they do not bring a risk of a local inflammatory reaction as corneal inlays do. Disadvantages of using the pinhole effect include high susceptibility to decentration, decrease in retinal luminance levels, and difficulties in performing fundus examinations or surgery in eyes with implanted devices. There are also concerns regarding perceptive issues with different retinal illuminances in the 2 eyes (the Pulfrich effect).

Refractive surgical correction and treatment of keratoconus

Keratoconus is an ectatic corneal disorder that causes severe vision loss. Surgical options allow us to correct, partially or totally, the induced refractive error. Intracorneal ring segments (ICRS) implantation represents a minimally invasive surgical option that improves visual acuity, with a high success rate and a low overall complication rate. Corneal allogenic ICRS consists of ring segments derived from allogenic eye bank-processed donor corneas. Selective topography-guided transepithelial photorefractive or phototherapeutic keratectomy combined with CXL is another way in selected cases to improve spectacles corrected distance visual acuity. The microphotoablative remodeling of the central corneal profile is generally planned by optimizing the optical zones and minimizing tissue consumption. Phakic intraocular lens (PIOL) implant is considered in patients with stable disease and acceptable anatomical requirements. The two types of pIOLs, depending on their implantation inside the eye, are anterior chamber-pIOLs, which fixate to the anterior surface of the iris by using a polymethomethacrolate claw at the two haptics, and posterior chamber-pIOLs. In patients with both cataracts and keratoconus, the correct IOL power is difficult to obtain due to the irregular corneal shape and K values. Toric IOL is recommended, but carefully judging the topography and the possible need of subsequent keratoplasties.

Radial keratotomy and cataract surgery: A quest for emmetropia

A 75-year-old man with an ocular history of 8-cut radial keratotomy (RK) in both eyes presented for cataract surgery evaluation. He was previously correctable in spectacles in years prior despite his irregular corneas to 20/25 in the right eye and 20/30 in the left eye. He recently noticed a change in his overall visual function with significant nighttime glare and difficulty reading despite spectacle correction. Of note, he was unable to tolerate contact lenses and was resistant to refitting despite additional encouragement. Cataract surgery was delayed for many years, given he was correctable in spectacles and the concern of uncovering a highly aberrated cornea after removing his cataracts (Figures 1 and 2JOURNAL/jcrs/04.03/02158034-202308000-00021/figure1/v/2023-07-21T030437Z/r/image-tiffJOURNAL/jcrs/04.03/02158034-202308000-00021/figure2/v/2023-07-21T030437Z/r/image-tiff). Of note, the patient was interested in returning to the spectacle independence he enjoyed in the past. Ocular examination revealed a corrected distance visual acuity (CDVA) of 20/30 in the right eye and 20/60 in the left eye, with a manifest refraction of +4.50 -0.50 × 177 in the right eye and +5.75 -1.75 × 14 in the left eye. Glare testing was 20/50 in the right eye and 20/100 in the left eye, with retinal acuity meter testing of 20/25 in each eye. Pupils, confrontation visual fields, and intraocular pressures were normal. Pertinent slitlamp examination revealed corneal findings of 8-cut RK with nasal-gaping arcuate incisions in both eyes and lens findings of 2+ nuclear sclerosis with 2+ cortical changes in the right eye and 3+ nuclear sclerosis with 3+ cortical changes in the left eye. Cup-to-disc ratios of the optic nerves measured 0.5 with temporal sloping in the right eye and 0.6 with temporal sloping in the left eye. The dilated fundus examination was unremarkable. What intraocular lens (IOL) options would you offer this patient and how would you counsel regarding realistic expectations? What additional diagnostic testing would be helpful in your assessment? How would you calculate the IOLs?

van den Berg A, Dodhia M, Shahid M, Jammal AA, de Freitas D, Rocha KM. Scheimpflug-Derived Corneal Lower and Higher Order Aberrations Post Intrastromal Corneal Ring Segments for Keratoconus

Intrastromal corneal ring segments (ICRS) improve corneal topographic symmetry and reduce corneal aberrations through regularization of the corneal surface, thereby functioning as a viable surgical intervention for patients with keratoconus. This study aims to evaluate changes in lower- (LOAs) and higher-order aberrations (HOAs) amongst varying pupil sizes pre- and post- ICRS implantation in keratoconus patients. We specifically investigate the impact of pupil size on total corneal HOAs up to the 6th order. Twenty-one eyes that underwent ICRS implantation were included in this prospective interventional study. LOAs and HOAs measurements at the 6 mm, 4 mm, and 2 mm pupil diameters were collected preoperatively and at 6 months postoperatively using the Zernicke analysis function on a Scheimpflug device. ICRS implantation demonstrated a statistically significant effect in vertical coma with a −0.23 reduction (p = 0.015) for a 4 mm pupil size and a −1.384 reduction (p < 0.001) for 6 mm, with no significant effect at 2 mm. Horizontal coma, astigmatism 0°, astigmatism 45°, trefoil 5th order 30°, and RMS HOA demonstrated significant reductions at 4 mm or 6 mm pupil sizes but not at 2 mm. Our analysis demonstrates a favorable effect of ICRS implantation on larger pupil sizes, suggesting the importance of pupil size as it correlates with HOAs reduction.

Small Aperture IC-8 Extended-Depth-of-Focus Intraocular Lens in Cataract Surgery: A Systematic Review

The aim of this paper is to evaluate the visual outcomes and patient satisfaction of small aperture IC-8 IOLs in cataract patients with or without prior ocular events. A systematic review of full-length original English studies reporting the visual results of small aperture IC-8 IOL implantation after cataract surgery in three databases, PubMed, Web of Science and Scopus, was performed according to the PRISMA statement. The Quality Assessment Tool for case series studies from the National Heart, Lung, and Blood Institute was used to analyze the quality of the studies selected. The search provided 543 articles, of which 22 were included in this systematic review. Significant improvements in uncorrected distance visual acuity (UDVA); uncorrected intermediate visual acuity (UIVA); uncorrected near visual acuity (UNVA); perception of photic phenomena; and patient satisfaction have been reported. Unilateral and bilateral small aperture IC-8 IOL implantation reduces photic phenomena and provides good vision for all distances with high patient satisfaction and minimal postoperative complications. Therefore, the implantation of this IOL may be recommended for patients with cataracts, corneal irregularities and ocular trauma with partial aniridia.

Intraocular lens power calculations in eyes with previous corneal refractive surgery: Challenges, approaches, and outcomes

In eyes with previous corneal refractive surgery, difficulties in accurately determining corneal refractive power and in predicting the effective lens position create challenges in intraocular lens (IOL) power calculations. There are three categories of methods proposed based on the use of historical data acquired prior to the corneal refractive surgery. The American Society of Cataract and Refractive Surgery postrefractive IOL calculator incorporates many commonly used methods. Accuracy of refractive prediction errors within ± 0.5 D is achieved in 0% to 85% of eyes with previous myopic LASIK/photorefractive keratectomy (PRK), 38.1% to 71.9% of eyes with prior hyperopic LASIK/PRK, and 29% to 87.5% of eyes with previous radial keratotomy. IOLs with negative spherical aberration (SA) may reduce the positive corneal SA induced by myopic correction, and IOLs with zero SA best match corneal SA in eyes with prior hyperopic correction. Toric, extended-depth-of-focus, and multifocal IOLs may provide excellent outcomes in selected cases that meet certain corneal topographic criteria. Further advances are needed to improve the accuracy of IOL power calculation in eyes with previous corneal refractive surgery.

Review of surgical devices using small aperture optics

Small aperture optics work by blocking unfocused peripheral light rays while allowing central light rays to focus on the retina. This pinhole effect creates an extended depth of focus and has been used in presbyopia correction, improving intermediate and near vision without markedly affecting distance vision. Another beneficial effect of small aperture optics is reducing aberrations caused by irregular corneas or irregular pupils. The first small aperture surgical device was the Kamra corneal inlay used on the nondominant eyes of presbyopic emmetropes. The pinhole concept was also adapted into the IC-8 intraocular lens (IOL) for presbyopia correction during cataract surgery and by the XtraFocus piggyback device to lessen unwanted aberrations in eyes with irregular corneas or pupils. The IC-8 IOL can be placed monocularly or binocularly with mini-monovision for further near vision improvement. The XtraFocus piggyback device can be placed either in the sulcus or capsular bag. The aim of this literature review is to synthesize evidence on the efficacy, safety, and patient-reported outcomes on surgical devices utilizing small aperture optics. A comprehensive search on PubMed was conducted with the keywords “small aperture optics,” “small aperture corneal inlay,” “small aperture IOL,” “Kamra corneal inlay,” “IC-8 IOL,” and “XtraFocus.” In this review, we describe the progression of small aperture surgical devices, patient criteria, visual outcomes, complications, satisfaction, and recommendations for surgical success.

New treatment algorithm for keratoconus and cataract: small-aperture IOL insertion with sequential topography-guided photorefractive keratectomy and simultaneous accelerated corneal crosslinking

PURPOSE

To describe a new treatment algorithm aimed at optimizing refractive outcomes for patients with keratoconus and cataract.

SETTING

Private practice in Sydney, Australia.

DESIGN

Retrospective case series.

METHODS

This procedural approach involves cataract extraction with small-aperture intraocular lens (IOL) insertion, IC-8 IOL (AcuFocus, Inc.), followed by topography-guided photorefractive keratectomy (T-PRK) with simultaneous corneal crosslinking (CXL). Cataract surgery was performed with an initial 2.4 mm clear corneal incision enlarged to 3.5 mm to accommodate IC-8 IOL insertion. Once eyes demonstrated stable corneal tomography and refraction, T-PRK was performed using Schwind excimer laser (500 Hz) with the Vancouver custom topographical neutralization technique, aiming to achieve low myopia. CXL was performed immediately after T-PRK using Optolink hypotonic riboflavin with LIGHTLink-CXL (Lightmed) with 5.4 J total energy delivered at an 18 mw/cm2 irradiance.

RESULTS

Outcomes of 4 eyes are reported with all achieving rigid gas-permeable (RGP) contact lens independence, improved corrected distance visual acuity (CDVA) and uncorrected distance visual acuity (UDVA), and regularization of corneal curvature with cone reduction. The mean CDVA improved from 0.43 preoperatively to 0.07 postoperatively (P = .00), and the mean UDVA improved from 0.81 preoperatively to 0.29 postoperatively (P = .04). Postoperative UNVA ranged from N.8 to N.12.

CONCLUSIONS

This treatment algorithm demonstrates unique combination of existing corneal and cataract surgical procedures to achieve satisfactory refractive outcomes and RGP contact lens independence in patients with keratoconus and cataract.

Bilateral implantation of a supplementary intraocular pinhole

PURPOSE

To evaluate the safety and efficacy of bilateral implantation of a supplementary small-aperture device to treat irregular corneal astigmatism.

SETTING

Private practice.

DESIGN

Retrospective consecutive case series.

METHODS

Patients with bilateral irregular corneal astigmatism secondary to multiple causes and consented for implantation of the XtraFocus intraocular pinhole (IOPH) were enrolled. The mean follow-up was 27 months (range 5 to 66 months). Patients were assessed in their scheduled follow-up visits and monocular and binocular uncorrected and corrected distance and near visual acuities were recorded. Assessment of darkening vision complaints was also performed after implantation in the first eye and repeated after second-eye surgery.

RESULTS

Thirty-two eyes of 16 patients were analyzed. The mean monocular and binocular uncorrected distance visual acuities improved from logMAR 1.091 ± 0.208 and 1.078 ± 0.259 preoperatively to 0.342 ± 0.091 (P < .001) and 0.342 ± 0.147 (P = .001) 1 year postoperatively. Three patients were excluded because of darkening vision complaints after surgery in the first eye. No major complications were noted after implantation of the IOPH.

CONCLUSIONS

Bilateral implantation of the XtraFocus IOPH is a safe technique in a selected group of patients. There was improvement in visual acuity sustained over the analyzed period. Postoperative darkening vision complaints vary between individuals and can limit the application of this approach in certain patients.

Predictability of Refractive Outcome of a Small-Aperture Intraocular Lens in Eyes With Irregular Corneal Astigmatism

PURPOSE

To compare different new-generation biometric formulas and ray-tracing for small-aperture intraocular lens (IOL) (IC-8; Acufocus, Inc) implantation in patients undergoing cataract and refractive lens exchange surgery with highly irregular corneas.

METHODS

This monocenter study included 17 eyes of 17 patients with highly irregular corneas of different genesis. Biometric and topographic corneal data were assessed using the IOLMaster 700 (Carl Zeiss Meditec) and Pentacam (Oculus Optkigeräte GmbH). Prediction and absolute error were compared after 3 months based on manifest refraction. Furthermore, change of total corneal refractive power in different corneal pathologies was also evaluated. For IOL power calculation, three fourth-generation IOL formulas were compared (Haigis, SRK-T, and Barrett Universal II). The dataset was then checked against ray-tracing and analyzed to improve prediction error in these highly irregular corneas.

RESULTS

All patients showed an improvement in visual acuity postoperatively with a mean spherical equivalent of -1.22 ± 0.49 diopters (D). Overall comparison of the three formulas showed the Haigis formula to be superior in terms of the smallest deviation of predictive and absolute error. IOL calculations with ray-tracing were possible in all eyes, but showed inaccurate results with keratometric values of 48.00 D and greater.

CONCLUSIONS

The IC-8 IOL is well suited for patients with lens exchange in highly irregular corneas. The Haigis formula seemed to be the most accurate in the patient group. Ray-tracing confirmed the results of biometric formulas up to a keratometric value of 48.00 D and should be compared with standard biometric formulas to address corneal irregularities and to minimize refractive surprises after surgery. A comparison with ray-tracing in eyes with a keratometric value of greater than 48.00 D should not be considered due to the inaccurate results. [J Refract Surg. 2021;37(5):312-317.].

Use of presbyopia-correcting intraocular lenses in patients with prior corneal refractive surgery

PURPOSE OF REVIEW

Corneal refractive surgery has achieved spectacle-free vision for millions of patients, but this aging population is now developing cataracts. Many of these patients may wish to avoid reliance on glasses after cataract surgery. Presbyopia-correcting intraocular lenses (IOLs) offer a solution, but corneal changes after refractive surgery may compound higher order aberrations and dysphotopic symptoms associated with these IOLs. This review aims to discuss potential factors that could aid in determining suitable postkeratorefractive candidates for presbyopia-correcting IOLs.

RECENT FINDINGS

Studies investigating which preoperative measures influence outcomes are lacking. The few studies that have examined presbyopia-correcting IOLs in postkeratorefractive patients report that satisfactory outcomes are possible. However, recommendations for preoperative thresholds appear limited to expert opinion and studies involving virgin corneas.

SUMMARY

As the number of presbyopia-correcting IOLs and postkeratorefractive patients grows, continued investigation into relevant preoperative factors and appropriate IOLs is required to make evidence-based decisions. The current literature shows that with rigorous counseling and appropriate patient selection, presbyopia-correcting IOLs can provide postkeratorefractive patients with satisfactory results and spectacle independence. In addition, the development of postoperative modifiable IOLs may prove to be the preferred option.

Lens-based surgical correction of presbyopia. Where are we in 2020?

INTRODUCTION

Presbyopia is the progressive and irreversible loss of accommodation due to aging. It is one of the main causes of loss of quality of life in people from 45 years of age, due to the, often novel, dependence on spectacles. The eagerness to correct it by ophthalmologists impulsed by the desire of millions of people who suffer from it, has become one of the main drivers for the development of intraocular lens (IOL) technology over the last twenty years.

MATERIAL AND METHODS

This review briefly presents the different alternatives that have allowed us to improve the crystalline lens surgical approach of presbyopia; from monofocal lenses and monovision technique, accommodative, refractive, and diffractive multifocal lenses, and finally the most recent extended depth of focus/field lenses known as EDOFs.

RESULTS

Each IOL has its advantages, limitations and disadvantages. Furthermore, there is no single lens that suits the needs of all patients.

CONCLUSIONS

It is necessary to know the variety of lenses available, and to have an in-depth understanding of their optical properties, as well as the impact that these will have later on their clinical performance and on the visual quality of the patients. This should help us to select the best alternative for each of them.

Toric intraocular lens combined with a supplementary pinhole implant to treat irregular corneal astigmatism

A case of refractive lens exchange with the implantation of a supplementary intraocular pinhole (IOPH) to treat a challenging case of keratoconus is presented. Four months after the initial procedure, an intraocular lens (IOL) exchange (under the IOPH) was performed to a toric implant to correct the residual manifest astigmatism. This significantly improved both distance and near acuities and demonstrates how a toric IOL and astigmatism correction in combination with a pinhole device could be used to treat selected cases of keratoconus.