Changes in astigmatism and corneal higher-order aberrations after phacoemulsification with toric intraocular lens implantation for mild keratoconus with cataract

Functional Approach to IOL Selection in Eyes With Combined Cataract and Keratoconus With an Option for Refractive Lens Exchange

PURPOSE

To evaluate spherical intraocular lens (IOL) implantation for cataracts in keratoconic eyes followed by optional refractive toric lens exchange to improve uncorrected visual acuity.

METHODS

This retrospective study evaluated cataract surgery outcomes in keratoconic eyes. Eyes treated with a spherical IOL targeted for -2.00 diopters (D) either achieved acceptable manifest refraction and desired exchange with a toric IOL (Group 1); achieved satisfactory manifest refraction and chose to use spectacles or contact lenses (Group 2); or did not achieve acceptable refraction and used contact lenses (Group 3). Group 4 had single-stage toric IOL implantation with plano target. Corrected and uncorrected distance visual acuity (CDVA and UDVA) and keratometry were analyzed.

RESULTS

Groups 1 to 4 had 18, 23, 18, and 26 eyes, respectively. A staged toric exchange resulted in significantly better (P = .02) UDVA (mean: 0.15 logMAR; 20/25 Snellen) than initial toric IOL implantation (0.24 logMAR; 20/30 Snellen). All toric IOL exchange eyes achieved 20/30 or better CDVA and 94% had 20/40 or better UDVA. Mean manifest cylinder significantly decreased from 3.39 D before lens exchange to 1.10 D postoperatively.

CONCLUSIONS

Initial implantation of a spherical IOL in keratoconic eyes allows basing toric calculations on the manifest refraction, which may be more reliable than keratometry measurements in keratoconic eyes. UDVA after staged toric IOL exchange was significantly better than after initial toric IOL implantation. Importantly, by staging use of toric lenses, the authors avoided cases where patients required a rigid contact lens after a toric IOL was implanted. [J Refract Surg. 2024;40(4):e207-e217.].

Current concepts in the management of cataract with keratoconus

This review analyzed all pertinent articles on keratoconus (KCN) and cataract surgery. It covers preoperative planning, intraoperative considerations, and postoperative management, with the aim of providing a simplified overview of treating such patients. Preoperatively, the use of corneal cross-linking, intrastromal corneal ring segments, and topo-guided corneal treatments can help stabilize the cornea and improve the accuracy of biometric measurements. It is important to consider the advantages and disadvantages of traditional techniques such as penetrating keratoplasty and deep anterior lamellar keratoplasty, as well as newer stromal augmentation techniques, to choose the most appropriate surgical approach. Obtaining reliable measurements can be difficult, especially in the advanced stages of the disease. The choice between toric and monofocal intraocular lenses (IOLs) should be carefully evaluated. Monofocal IOLs are a better choice in patients with advanced disease, and toric lenses can be used in mild and stable KCN. Intraoperatively, the use of a rigid gas permeable (RGP) lens can overcome the challenge of image distortion and loss of visual perspective. Postoperatively, patients may need updated RGP or scleral lenses to correct the corneal irregular astigmatism. A thorough preoperative planning is crucial for good surgical outcomes, and patients need to be informed regarding potential postoperative surprises. In conclusion, managing cataracts in KCN patients presents a range of challenges, and a comprehensive approach is essential to achieve favorable surgical outcomes.

Development of a Web-Based Algorithm for Understanding the Intraocular Lens-Based Surgery in Stable and Progressing Keratoconus for Non-Specialist Ophthalmologists

PURPOSE

To propose an algorithm to facilitate lens-based surgery in keratoconus.

METHODS

A literature review was performed to prepare a software algorithm based on cone location, stability, best spectacle-corrected distance visual acuity (BSCVA) level and whether there is a clear or cataractous lens. The software usability was assessed through a 10-question questionnaire and two hypothetical keratoconus case histories (moderately simple and moderately complex) given to 15 trainees. The usability questionnaires were graded on a Likert scale (1 = strongly disagree to 5 = strongly agree) and two case histories (1 = very difficult to 7 = very easy).

RESULTS

The algorithm can be found at https://www.sussexeyelaserclinic.co.uk/keratoconus/. Thirteen trainees completed the questionnaire. 91.9% would frequently use it; for 100%, it was easy to use independently without technical support; for 63.7%, it was strongly integrated; for 100%, it was consistent; 100% thought that most people would learn to use it quickly, 91.9% found the system not cumbersome to use, felt very confident to use it and need not learn a lot to use it. The first case was found easy by 63.7% and the second by 45%.

CONCLUSION

We present an algorithm as a guide for lens-based surgery in stable and progressing keratoconus, which is classified based on cone location. This algorithm will help trainee and "non-specialist" ophthalmic surgeons understand the pre-operative planning for the surgery and referral to the "specialist" corneal surgeon, considering factors such as progression, BSCVA, keratometry, topography and apex location of the cone in keratoconus patients.

Diffractive Trifocal Intraocular Lens Implantation in Stable Subclinical and Forme Fruste Keratoconus: A Case Series

In this retrospective case series, we examine the outcomes of diffractive trifocal intraocular lens implantation after cataract surgery, in patients with subclinical and forme fruste keratoconus. Eight eyes of four patients (aged between 47 and 64) were included in the study and underwent phacoemulsification with implantation of AT LISA tri 839MP or AT LISA tri-toric 939MP intraocular lenses (Carl Zeiss Meditec AG, Jena, Germany). Post-operative evaluation included a visual acuity test at three distances (6m, 80cm, and 40cm), a visual acuity test at three low contrast levels (25%, 12.5%, and 6%), and a questionnaire about the patients' experience with photic phenomena and overall satisfaction with the achieved quality of vision. Our results show that spectacle freedom was achieved in all cases with a high satisfaction rate among participants. We hope our results would encourage surgeons to offer this technology to carefully selected candidates with stable subclinical and forme fruste keratoconus undergoing cataract surgery, giving them the possibility of achieving spectacle independence.

Quantifying Corneal Topographic Astigmatism (CorT Total) in Keratoconic Eyes

PURPOSE

To determine optimal corneal regions from which to derive corneal topographic astigmatism (CorT) in kerato-conic eyes.

METHODS

In this retrospective study, potential measures of corneal astigmatism are calculated from raw total corneal power data (179 eyes from 124 patients) from a corneal tomographer. The measures are derived from annular corneal regions varying in both extent and center position, and evaluated according to the variability of the ocular residual astigmatism (ORA) in the cohort. This variability is quantified by the ORArms, which is the root-mean-squared distance of the ORAs from their summated vector mean in double angle space. The lower the ORArms, the better the corneal astigmatism measure corresponds to manifest refractive cylinder.

RESULTS

Corneal astigmatism measures derived from regions centered on corneal vertex had ORArms values (mild: 1.07 diopters [D], moderate: 1.61 D, severe: 2.65 D) as low or lower than other measures derived from regions centered on thinnest point, corneal apex (front or back), or pupil center. Corneal astigmatism measures derived from a region centered 30% of the way toward thinnest point from corneal vertex appeared to have even lower ORArms values (mild: 1.05 D, moderate: 1.45 D, severe: 2.56 D). None of the corneal astigmatism measures corresponded closely with manifest refractive cylinder for severe keratoconus (ORArms > 2.50 D).

CONCLUSIONS

For keratoconic eyes, the CorT should be derived from an annular region centered 30% of the way toward thinnest point from corneal vertex, although when the keratoconus is mild, a standard corneal-vertex-centered CorT performs just as well. [J Refract Surg. 2023;39(3):206-213.].

Cataract surgery in Keratoconus revisited - An update on preoperative and intraoperative considerations and postoperative outcomes

PURPOSE

This review aims to evaluate and simplify the recent literature on preoperative surgical planning, intraoperative considerations, postoperative surprises, and their management in patients with keratoconus undergoing cataract surgery.

METHODS

A review of the literature was done to analyze all the pertinent articles on Keratoconus and cataract surgery.

RESULTS

The surgical planning of cataracts in eyes with keratoconus needs a multifaceted approach. Preoperatively, techniques such as cross-linking or the use of intra-corneal rings help stabilize the progression. Unreliable biometric measurements are a significant problem in keratoconus patients, especially in an advanced stage of the disease. It is better to consider actual K readings if the K value is less than 55D but for a K value, more than 55D using standard K values will prevent postoperative refractive surprises. For calculation of K values, an elevation-based device like pentacam gives better repeatability in mild to moderate cases whereas for advanced keratoconus none of the keratometers is reliable. Recently, the Kane keratoconus formula performed better in all stages of disease whereas previous studies showed good results with SRK/T formula is a mild and moderate disease. Monofocal intraocular lenses are a better choice in these patients. Toric lenses can be used in mild and stable keratoconus. Intraoperatively, the use of a customized RGP lens can overcome the challenge of image distortion and loss of visual perspective. Despite taking necessary measures, postoperative refractive surprise can occur and can be managed with IOL exchange or Secondary IOLs.

CONCLUSION

There is a spectrum of challenges in managing cataracts in keratoconus which makes thorough preoperative planning important for good surgical outcomes. Despite the measures, there might be post-operative surprises and the patients need to be informed regarding the same.

Comparison of anterior corneal aberrations measured by Scheimpflug and Placido Disc System for myopes

BACKGROUND

To ascertain the agreement of corneal aberrations obtained from the Pentacam and the KR-1W in myopic populations and to investigate the influence of the level of myopia as well as the laterality on the agreement.

METHODS

In this observational study, a rotating Scheimpflug camera (Pentacam AXL) and a Hartmann-Shack wavefront analyzer with Placido-disc topographer (KR-1W) were used to measure the aberrations of myopes in the anterior corneal surface by one experienced operator. All examinations were computed across a 6 mm diameter. Six subgroups were generated according to the degree of myopia (mild, moderate, and severe myopia) and the laterality of eyes (right and left eyes).

RESULTS

The study included 245 eyes of 170 participants. For certain anterior corneal aberrations, statistically significant differences existed between the Pentacam and the KR-1W (all P < .05). The values of Zernike (Z)(2,0), Z(2,2), Z(3,1), and Z(4,0) varied in all levels of myopia regardless of the laterality, with the values of the Pentacam constantly larger than the KR-1W in the measurement of Z(2,0), Z(2,2), and Z(4,0). For 2nd to 6th aberrations, both instruments correlated poorly to moderately. The width of limits of agreement between the two instruments was clinically too wide (> 0.1 μm) for aberrations closely correlated with visual quality, including Z(3, ± 3), Z(3, ± 1), and Z(4,0), and almost all aberrations, indicating poor agreement.

CONCLUSIONS

In clinical practice, the Pentacam based on Scheimpflug technology and the KR-1W based on Placido Disc System are not interchangeable in measuring anterior corneal aberration for myopes regardless of myopia degree and the laterality, suggesting that a consistent instrument should be selected for surgical design as well as follow-up.

Refractive Outcomes of Non-Toric and Toric Intraocular Lenses in Mild, Moderate and Advanced Keratoconus: A Systematic Review and Meta-Analysis

Background: To perform a systematic review and meta-analysis of the refractive outcomes of non-toric and toric intraocular lenses (IOLs) in keratoconus (KC) using different IOL power calculation formulas. Methods: A systematic search was conducted to identify studies that report on refractive outcomes of different IOL power calculation formulas in KC patients undergoing cataract surgery. Inclusion criteria were primary posterior chamber non-toric and toric monofocal intraocular lens implantation, data on the degree of KC, explicit mention of the formula used for each stage of KC, and the number of eyes in each category. We calculated and compared the absolute and mean prediction errors, percentage of eyes within 0.5 D and 1 D from target, and the weighted absolute prediction errors of IOL formulas, all were given for KC degrees I–III. Results: The bibliographic search yielded 582 studies published between 1996 and 2020, 14 of which (in total 456 eyes) met the criteria: three studies on non-toric IOL (98 eyes), eight studies on toric IOLs (98 eyes) and three studies of unknown separation between non-toric and toric IOLs (260 eyes). The lowest absolute prediction error (APE) for mild, moderate, and advanced KC was seen with Kane’s IOL power formula with keratoconus adjustment. The APE for the top five IOL power formulas ranged 0.49–0.73 diopters (D) for mild (83–94%) of eyes within 1 D from the target), 1.08–1.21 D for moderate (51–57% within 1 D), and 1.44–2.86 D for advanced KC (12–48% within 1 D). Conclusions: Cataract surgery in eyes with mild-to-moderate KC generally achieves satisfactory postoperative refractive results. In patients with advanced KC, a minority of the eyes achieved spherical equivalent refraction within 1 D from the target. The Kane’s formula with keratoconus adjustment showed the best results in all KC stages.

Two-stage treatment of ametropia in patients with keratoconus and cataracts

Keratoconus (KC) is a progressive degenerative corneal disease, leads to the aberration of biomechanical and optical properties and thinning of the cornea, causes astigmatism and decreases visual acuity.Materials and methods. 33 patients (35 eyes) with stages II–III of non-progressive keratoconus and concomitant cataracts of various stages of maturity were operated on. The average age of the patients was 46.5 ± 2.7 (41–63) years old. The operations were performed according to our proposed two-stage method of treating ametropia in patients with KC and cataracts (Patent of the Russian Federation No. 2748634 of 28.05.2021). The first stage was the implantation of FERRARA intrastromal corneal ring segments (ICRS) with thickness from 150 to 350 μm. To correct residual refractive error in 5–7 months after stage 1, patients underwent stage 2: cloudy lens was removed and replaced with toric posterior chamber intraocular lens (TIOL) – AcrySof IQ Toric (Alcon, USA), T-fl ex Toric RayOne (Rayner, UK).Results and discussion. After stage 1 of the operation (ICRS implantation), the uncorrected visual acuity (NCVA) was 0.2 ± 0.03, the best corrected visual acuity (BCVA) was 0.4 ± 0.02. In 1 month after stage 2 (phacoemulsifi cation + TIOL) NCVA was 0.64 ± 0.11 and BCVA was 0.74 ± 0.12. During the entire follow-up period after the surgery visual functions, refraction, and rotational stability of TIOL were stable.Conclusions. Conducting a two-stage surgical intervention in patients with keratoconus and cataracts allows to stop the progression of the disease and effectively correct the ametropia concomitant with keratoconus.

Toric intraocular lens power calculation in cataract patients with keratoconus

Purpose

Intra-ocular lens (IOL) power calculation in eyes with keratoconus typically results in hyperopic postoperative refractive error. We investigated the visual and refractive outcomes in keratoconus patients having cataract surgery with a toric IOL and compared IOL power calculation accuracy of conventional formulae and keratoconus specific formulae.

Setting

Ein-Tal Eye Center, Tel-Aviv, Israel.

Design

Retrospective case-series study.

Methods

Post-operative visual acuity and manifest refraction were examined. The error in predicted refraction and IOL power calculation accuracy within a range of 0.5 to 2.0 diopters were compared between different IOL calculating formulae.

Results

Thirty-two eyes with keratoconus were included. Visual acuity improved in all cases and subjective astigmatism decreased from -2.95+/-2.10 D to -0.95+/-0.80 D (p<0.001). Mean absolute errors were: Barrett True-K for keratoconus with measured or predicted posterior corneal power, 0.34 D; Barrett Universal II, 0.64 D; Kane Formula, 0.69 D; Kane Formula for keratoconus, 0.49 D; SRK/T, 0.56 D; Haigis, 0.72 D; Holladay 1, 0.71 D and Hoffer Q, 0.87 D. Barrett True-K formula with measured posterior corneal power, SRK/T and Kane Formula for keratoconus resulted in a prediction error within 0.5 D of 87.5%, 59.4% and 53.1%, respectively.

Conclusions

Cataract removal with a toric IOL significantly improves visual acuity and decreases astigmatism in keratoconic eyes with a topographic central relatively regular astigmatic component. Keratoconus specific formulae resulted in lower mean error in predicted refraction compared with conventional calculating formulae. Utilizing the posterior corneal power within the Barrett True K formula for keratoconus improved IOL power prediction accuracy.

[Intraocular correction of ametropia in patients with keratoconus]

This review was conducted due to the growing number of patients with keratoconus requiring cataract surgery and the complexity of surgical planning. The article reviews preoperative planning, intraoperative options, and postoperative management, which can help obtain high functional results. Treatment of cataracts in keratoconic eyes requires a multifaceted approach. In some cases, in the preoperative period, interventions such as crosslinking and implantation of intrastromal segments or corneal ring may be required to ensure stable keratometry values for accurate intraocular lens (IOL) calculations. The use of stabilizing procedures prior to optical biometrics can assist in preoperative lens selection and provide predictable surgical outcomes. To achieve targeted refraction and reduce unwanted optical effects, it is necessary to take a critical approach when choosing the type of lens (toric, monofocal). This is due to the appearance of aberrations of different order after preliminary surgical interventions on the cornea. The intraoperative decision plays important role in choosing the position of the corneal incisions, how to use sutures for wound adaptation, choosing scleral approaches to minimize possible postoperative complications. In the postoperative period, the degree of irregular astigmatism and the need for rigid gas-permeable or scleral lenses should be assessed.

Long-term refractive outcomes in patients with cataracts and keratoconus after phacoemulsification with toric intraocular lens implant

PURPOSE

To determine the refractive stability of patients with keratoconus and cataracts after the implantation of a toric intraocular lens.

METHODS

This is a cross-sectional, retrospectivestudy. Clinical records from patients with non-progressive keratoconus and cataracts that underwent non-complicated phacoemulsification with toric IOL implantation were reviewed. Mean keratometry (Km), refractive cylinder (RC), spherical equivalent (SE), steeper keratometry (K), and axis were evaluated at the 1-month, 6-month, 12-month, and 24-month follow-up visits.

RESULTS

Fifty-four eyes from 41 patients were included. Thirty-seven (68.5%) female and 17 (31.5%) male patients, with a mean age of 67.52 ± 8.22. Refractive cylinder at postoperative 30 days was -1.61 ± 1.23, 6-month -1.22 ± 0.80, 12-month -1.10 ± 0.83 and 24-month visit after surgery was -1.37 ± 0.77(p = 0.290). SE at the 30-day visit was -0.82 ± 1.90, 6-month -0.64 ± 1.23, 12-month -0.78 ± 1.91 and at 24-month postoperative visit -1.02 ± 1.87 (p = 0.210). Km value at the 1-month visit was 47.23 ± 1.95, 6-month 47.87 ± 1.61, 12-month 46.39 ± 2.52 and 24-month postoperative visit 46.92 ± 1.26 (p = 0.877). The steeper K axis in the 30-day control was 78.53 ± 30.12, 6-month 77.29± 37.68, 1-year 93.13 ± 62.42, 24-month 67.31 ± 38.49 (p = 0.632).

CONCLUSIONS

Our findings suggest a low variation in the refractive outcome for patients with mild and moderate keratoconus and cataracts, without evident progression signals, a demonstrated keratoconus clinical stability. No statistically significant postoperative changes in the refractive cylinder, SE, mean K, and steeper K axis were observed, which suggests good predictability for toric IOL implant.

Refractive approaches to visual rehabilitation in patients with keratoconus

PURPOSE OF REVIEW

As keratoconus is a chronic disease affecting young people, vision-related quality of life is often significantly impaired in patients with this disease. However, successful management of keratoconus, including visual rehabilitation strategies, can improve quality of life in these patients. This review will describe clinical approaches that improve vision-related quality of life in patients with stable keratoconus.

RECENT FINDINGS

Several types of contact lenses including scleral lenses have been used successfully to manage keratoconus. Eyes with severe keratoconus, even those in which fitting with other types of lenses is challenging, can be successfully fitted with scleral lenses. Although laser ablative procedures, such as photorefractive keratectomy (PRK) have been traditionally contraindicated in patients diagnosed with or suspected of having keratoconus, PRK has been attempted to partially correct refractive errors in keratoconus. Although phototherapeutic keratectomy and radial keratotomy have been reported to be used in eyes with keratoconus, effectiveness and safety results have varied. Implantation of phakic intraocular lenses and intraocular lenses, including toric intraocular lenses, which primarily correct regular astigmatism, with cataract extraction or refractive lens exchange can improve vision-related quality of life in patients with keratoconus by significantly reducing cylinder while improving uncorrected visual acuity.

SUMMARY

Appropriate selection and application of treatment options based on consideration of multiple factors will help patients with keratoconus, improving their vision-related quality of life and delaying or avoiding keratoplasty.

Accuracy of Intraocular Lens Formulas in Eyes With Keratoconus

PURPOSE

To evaluate the refractive accuracy of current intraocular lens (IOL) formulas in eyes with keratoconus.

DESIGN

Retrospective case series.

METHODS

Preoperative optical biometry, Pentacam topography, and postoperative outcomes were collected from eyes with keratoconus that had uncomplicated cataract surgery between 2014 and 2018 at a single institution. Exclusion criteria include postoperative best-corrected spectacle visual acuity worse than 20/40, multifocal lens, prior ophthalmic surgeries, and prior ocular trauma. The Hoffer Q, SRK/T, Holladay I, Holladay II, Haigis, and Barrett Universal II formulas were analyzed in each eye stratified by keratoconus severity.

RESULTS

A total of 73 eyes were included. All formulas had a positive mean predicted error ranging from 0.10 to 4.38 diopters (D). The Barrett Universal II formula had the lowest median absolute error for stage I (n = 46, 0.445 D) and II (n = 22, 0.445 D) eyes, and the highest percentage of eyes with predicted error within ±0.50 D for both stage I (52%) and II (50%) eyes. In stage III eyes (n = 5), the Haigis formula had the lowest median predicated error (1.90 D) and the highest percentage of eyes with predicted error within ±0.50 D (40%). Corneal power measured by optical biometers was higher than measurements by Pentacam keratometry.

CONCLUSIONS

All formulas tend to have a hyperopic surprise. The Barrett Universal II formula was the most accurate for mild to moderate disease. Pentacam keratometry may help avoid hyperopic outcomes.

Refractive and Visual Outcomes and Rotational Stability of Toric Intraocular Lenses in Eyes With and Without Previous Ocular Surgeries: A Longitudinal Study

PURPOSE

To evaluate visual and refractive outcomes and rotational stability of toric intraocular lens (IOL) implantation in eyes with previous ocular surgeries.

METHODS

This controlled, longitudinal cohort study included a total of 133 eyes (59 study cases with a history of corneal, vitreoretinal, and/or glaucoma surgery and 74 randomly selected controls without a history of ocular surgery) that had cataract and corneal astigmatism treated with toric IOL implantation. Postoperative outcomes were recorded at postoperative 1 month and 3 to 12 months.

RESULTS

Refractive prediction errors were within ±1.00 diopter (D) of target in 93.5% and 88.4% of the study cases at postoperative 1 month and 3 to 12 months, respectively. They were within ±0.50 D of target in 56.5% and 60.5% of the cases during the same follow-up intervals, respectively. Study cases showed statistically significantly inferior uncorrected distance visual acuity (UDVA) compared to controls at 1 month postoperatively (0.27 ± 0.24 and 0.17 ± 0.21 logMAR, respectively, P = .027) but not during the later follow-up (0.19 ± 0.19 and 0.16 ± 0.19 logMAR, respectively, P = .431). Corrected distance visual acuity (CDVA) was slightly lower in the study cases than in controls at 1 month postoperatively (0.13 ± 0.16 and 0.07 ± 0.14, respectively, P = .005) and subsequent follow-up months (0.10 ± 0.13 and 0.03 ± 0.10, respectively, P < .001). Of the examined study cases, 93.9% and 88.4% had IOL axes within 5° of intended axis at postoperative 1 month and 3 to 12 months, respectively.

CONCLUSIONS

Toric IOLs provided significant and sustained improvement in visual acuity and refraction in eyes with a history of prior ophthalmic surgery. Refractive outcomes achieved postoperatively were comparable to those in eyes without a prior history of ophthalmic surgery, although the rate of visual recovery may be different. [J Refract Surg. 2019;35(12):781-788.].

Management of cataract in keratoconus: early visual outcomes of different treatment modalities

A review of 31 eyes with keratoconus who developed cataract and underwent phacoemulsification. Visual acuities were measured 1mo postoperatively. Six eyes with a history of good corrected distance visual acuity (CDVA) and a similar refractive and topographic astigmatic axis were implanted with toric intraocular lenses (IOLs). The mean postoperative uncorrected distance visual acuity (UDVA) was 0.2 logMAR with a spherical equivalent (SE): 0.75D. Eleven eyes with a history of good CDVA and different refractive and topographic axis were implanted with monofocal IOL+/-Toric implantable collamer lenses to treat anisometropia and ametropia; mean UDVA was 0.25 logMAR with a mean SE: -0.51 D postoperatively. Six eyes with poor CDVA were first treated with intra-corneal ring segments, followed by phacoemulsification, the mean postoperative UDVA was 0.82 logMAR with an SE: 0.22 D. Eight eyes had advanced ectesia and received combined phacoemulsification and penetrating keratoplasty. Our approach is efficient in addressing ametropia after cataract surgery in keratoconic eyes.

Current Trends in Modern Visual Intraocular Lens Enhancement Surgery in Stable Keratoconus: A Synopsis of Do's, Don'ts and Pitfalls

Keratoconus is a relatively common ectatic, non-inflammatory corneal disorder that involves gradual visual deterioration through progressive alteration of the shape of the cornea. The corneal thinning, irregular astigmatism and higher order aberrations that occur as the disease progresses pose major challenges in the visual rehabilitation of such patients. This paper summarizes the current literature regarding the results of visual enhancement procedures in patients with stable keratoconus treated with standalone anterior or posterior chamber phakic intraocular lens implantation and monofocal, toric or multifocal toric intraocular lens implantation following phacoemulsification for age-related cataract extraction or refractive lens exchange.

Intraocular lens power calculation in keratoconus; A review of literature

Purpose

To review the published literature regarding cataract surgery in keratoconus (KCN) patients with emphasis on challenges encountered during intraocular lens (IOL) power calculation and their solutions.

Methods

A literature review was performed to investigate all the relevant articles on the advancements of IOL calculations in KCN patients.

Results

Cataract surgery in keratoconic eyes can improve patients' refraction, and proper patient selection and IOL calculation methods are necessary to get the best results. The main problem in KCN patients is unreliable biometric measurements. It is more difficult to make conclusions in more advanced keratoconic corneas, as the steep keratometric values in these eyes will result in the selection of a low-power IOL. Presence of a low-power IOL will yield in extreme postoperative hyperopia, and IOL exchange might be mandatory. In cases in which keratoplasty may be needed in the future, contact lens fitting can help surgeons make a better decision preoperatively. Axial length (AL) measurements may have better repeatability and reproducibility than keratometry (K) readings in keratoconic eyes. SRK II formula may provide the most accurate IOL power in mild KCN. There is still not a comprehensive consensus of which formula is the best one in moderate and severe KCN, as the literature is limited in this subject.

Conclusions

Various methods of IOL power calculation optimization and recommendations may hold the key to improve surgical outcomes in keratoconic eyes. There are multiple sources of biometric error in KCN patients, hence IOL calculation methods may not be as efficient as expected in these eyes.

Two-stage procedure in the management of selected cases of keratoconus: clear lens extraction with aspherical IOL implantation followed by WFG-PRK

AIM

To assess the objective and subjective results of a two-stage procedure for management of keratoconus: clear lensectomy with aspherical intraocular lens (IOL) implantation followed by wave front-guided photorefractive keratotomy (WFG-PRK).

METHODS

This prospective interventional non-randomized study included patients aged 35 years old or more with grade I and II stable keratoconus, a clear visual axis, minimal corneal thickness (MCT) 420 µm or more and average keratometric reading (K) less than 54 diopter (D). Refraction of all selected eyes should be -8.00 D sphere or more with less than -6.00 D cylinder and could be corrected two lines or more with spectacles or contact lenses. All studied eyes underwent a two-stage approach treatment: first refractive lens exchange and aspherical IOL implantation followed, after at least 3mo, by WFG-PRK. Pre and postoperative complete ophthalmological examination were performed. Topographical, visual and aberrometric results were recorded and evaluated during 6mo follow up period. Moreover, patient satisfaction and other subjective outcomes were also analyzed.

RESULTS

The 13 eyes of 11 patients diagnosed with stable keratoconus and aged from 39 to 49y (42.4±6.2y) were enrolled in the study. At baseline, 8 eyes had grade I and 5 eyes had grade II keratoconus. The manifest sphere was -10.3±4.2 D (ranged from -8.0 to -14.0 D) and the manifest cylinder was -4.2±1.2 D (ranged from -1.75 to -5.50 D). After the two-stage procedure, sphere and cylinder reduced significantly to -0.43±0.22 D and -1.3±0.72 D respectively (P<0.001). There was also a highly significant improvement in the mean uncorrected distance visual acuity (UDVA) from logMAR 1.41±0.49 preoperatively to 0.51±0.16 postoperatively (P<0.001) and the mean corrected distance visual acuity (CDVA) from 0.76±0.24 preoperatively to 0.49±0.13 after the operation (P<0.001). All aberrometric and mesopic vision parameters and most of the topographical indices demonstrated highly significant improvement that remains stable until the end of follow up. All recorded subjective data revealed a high degree of patient satisfaction.

CONCLUSION

Two-stage approach (clear lens exchange with monofocal IOL followed by WFG-PRK) in selected cases of keratoconus is a safe, effective and highly predictable procedure with satisfactory visual and refractive results.

Implantation of toric intraocular lenses in patients with cataract and keratoconus: a case series

Purpose

To describe the results of phacoemulsification and implantation of toric intraocular lenses (IOLs) in patients with cataract and keratoconus.

Patients and methods

Prospective study of 4 patients (4 eyes) with cataract and keratoconus who underwent phacoemulsification with implantation of a toric IOL. Two different toric IOLs were used: AcrySof IQ SN6AT9 and AT Torbi 709M(P). Corneal tomography was performed preoperatively using Scheimpflug technique with Pentacam. Astigmatism was regular or slightly irregular in all patients. Postoperatively, best-corrected visual acuity (BCVA), astigmatism, spherical equivalent, and complications were recorded for all patients. Follow-up time was between 4 weeks and 7 months.

Results

BCVA increased and astigmatism decreased in all patients. BCVA increased from 20/50 to 20/40 in patient 1, from 20/63 to 20/20 in patient 2, from 20/40 to 20/32 in patient 3, and from hand motion to 20/40 in patient 4. Astigmatism decreased from −6.12 to −3.75 D in patient 1, from −4.62 to −1.75 D in patient 2, from −9.0 to −3.0 D in patient 3, and from −8.0 to −2.75 D in patient 4. One patient developed pseudophakic cystoid macular edema, but at last follow-up after 6 months the edema had resolved. Another patient developed posterior capsular opacification after 2 months. No misalignment of the axis of the IOL was observed.

Conclusion

Correction of both astigmatism and cataract with phacoemulsification and implantation of a toric IOL can be an effective and safe choice for patients with cataract and keratoconus. However, predicting the refractive outcome in cataract surgery is difficult in patients with keratoconus, and the surgeon should be aware of different sources of biometric errors and the possible consequences.

Clinical Outcomes of Sequential Intrastromal Corneal Ring Segments and an Extended Range of Vision Intraocular Lens Implantation in Patients with Keratoconus and Cataract

Purpose

To evaluate efficacy, safety, and predictability of sequential Ferrara-type intrastromal corneal ring segments (ICRS) and an extended range of vision intraocular lens (IOL) implantation in patients with keratoconus and cataract.

Methods

This study comprised patients with keratoconus and cataract that had ICRS implantation followed 6 months later by extended range of vision IOL implantation. The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and residual refractive errors, analysed using vector analysis, were recorded preoperatively, 6 months after ICRS implantation, and 6 months after IOL implantation, respectively.

Results

The study enrolled 17 eyes (11 patients). The mean UDVA (logMAR scale) was 1.15 ± 0.67 preoperatively, 0.88 ± 0.69 six months after ICRS implantation (P = 0.005), and 0.27 ± 0.18 six months after IOL implantation (P < 0.0001). The CDVA changed from 0.26 ± 0.15 (logMAR) before surgery to 0.17 ± 0.08 six months after Ferrara-type ICRS implantation (P = 0.002) and to 0.07 ± 0.06 six months after IOL implantation (P < 0.0001). The spherical equivalent and the refractive cylinder declined steeply after IOL implantation (P < 0.001). The magnitude of depth of focus was 2.60 ± 1.02 D. There were no statistically significant differences in visual acuity for a defocus range from +0.50 D to −0.50 D (P > 0.1).

Conclusion

Sequential Ferrara-type ICRS and an extended range of vision IOL implantation provided good visual and refractive outcomes, being an effective, safe, and predictable procedure for the treatment of selected cases of patients with keratoconus and cataract. In addition, this approach provides an increase of tolerance to defocus.

Topography-Guided Photorefractive Keratectomy in the Treatment of Corneal Scarring

PURPOSE

To report the outcome of topography-guided photorefractive keratectomy (TG-PRK) in the treatment of patients with corneal scarring.

METHODS

A retrospective, interventional case series including 6 eyes of 6 patients with corneal scarring and irregular astigmatism who underwent TG-PRK. The etiologies for scarring were: infectious corneal ulcers, foreign body trauma, LASIK flap buttonhole, and lamellar keratoplasties performed to correct corneal perforation secondary to corneal melting. Main outcome measures were corrected distance visual acuity, uncorrected distance visual acuity, manifest refraction, and corneal regularity on topography maps.

RESULTS

Average age was 56.5 ± 19.6 years and average follow-up time was 14.8 ± 6.1 months. Three patients had corneal scarring with cataract and underwent TG-PRK to achieve sufficient regularization of corneal astigmatism to enable the implantation of a toric intraocular lens (IOL). The three remaining patients had TG-PRK performed to improve visual acuity, and all had improvement in uncorrected (improvement between one and three Snellen lines) and corrected (improvement between two and three Snellen lines) distance visual acuity. There were no intraoperative or postoperative complications and no loss of visual acuity.

CONCLUSIONS

The use of TG-PRK for corneal scarring may improve visual acuity in selected cases, obviate the need for keratoplasty in some cases, and facilitate toric IOL implantation in some cases. [J Refract Surg. 2017;33(9):639-644.].

Predictability of Intraocular Lens Power Calculation for Cataract with Keratoconus: A Multicenter Study

This study was aimed to assess the predictability of intraocular lens (IOL) power calculation after cataract surgery for keratoconus. We retrospectively reviewed the clinical charts of 102 eyes of 71 consecutive keratoconic patients who developed cataract. We determined manifest spherical equivalent, prediction errors, and absolute errors, 1 month postoperatively. The achieved refraction was significantly more hyperopic than the targeted refraction, when keratometric readings were used (p = 0.001). At 1 month, 36% and 63% of the eyes were within ±0.5 and ±1.0 D, respectively, of the targeted correction. We found a significant correlation between the prediction error and the mean keratometry (Pearson correlation coefficient r =−0.545, p < 0.001). No vision-threatening complications occurred in any case. The achieved refraction was significantly more myopic than the targeted refraction, when total corneal refractive power was used (p = 0.013). Phacoemulsification with IOL implantation appeared to be safe and effective, and the accuracy was also good in mild keratoconus, but not in severe keratoconus. It should be noted that that a large amount of hyperopic shift occurred especially in advanced keratoconic patients, when keratometric readings were used for IOL power calculation, and that a slight, but significant, myopic shift occurred, when total corneal refractive power was used.

Surgical Options for the Refractive Correction of Keratoconus: Myth or Reality

Keratoconus provides a decrease of quality of life to the patients who suffer from it. The treatment used as well as the method to correct the refractive error of these patients may influence on the impact of the disease on their quality of life. The purpose of this review is to describe the evidence about the conservative surgical treatment for keratoconus aiming to therapeutic and refractive effect. The visual rehabilitation for keratoconic corneas requires addressing three concerns: halting the ectatic process, improving corneal shape, and minimizing the residual refractive error. Cross-linking can halt the disease progression, intrastromal corneal ring segments can improve the corneal shape and hence the visual quality and reduce the refractive error, PRK can correct mild-moderate refractive error, and intraocular lenses can correct from low to high refractive error associated with keratoconus. Any of these surgical options can be performed alone or combined with the other techniques depending on what the case requires. Although it could be considered that the surgical option for the refracto-therapeutic treatment of the keratoconus is a reality, controlled, randomized studies with larger cohorts and longer follow-up periods are needed to determine which refractive procedure and/or sequence are most suitable for each case.

Measurement centration and zone diameter in anterior, posterior and total corneal astigmatism in keratoconus

PURPOSE

To investigate the central and paracentral astigmatism and the significance of centration and measurement zone diameter compared to a 3-mm pupil-centred measurement zone in keratoconus and in healthy eyes.

METHODS

Twenty-eight right eyes from 28 KC patients with an inferotemporal cone were selected according to specified criteria based on Oculus Pentacam HR^® measurements and were matched with healthy control eyes. The flat (K1) and steep (K2) keratometry readings were registered from the 'Total Corneal Refractive Power' (TCRP) display as well as the anterior and posterior corneal astigmatism displays (ACA and PCA, respectively). Astigmatic power vectors KP0 and KP45 were calculated and analysed for a 6-mm and two 3-mm zones centred on the corneal apex and the pupil, and for 8 paracentral 3-mm zones.

RESULTS

The astigmatism was generally higher in KC. Many astigmatic values in KC differed between the 3-mm pupil-centred and the 3- and 6-mm apex-centred zones in KC. In the controls, no corresponding differences between measurement zones were seen, apart from PCA, which differed. The magnitude and direction of KP0 and KP45 varied greatly between the paracentral measurements in KC.

CONCLUSION

Centration and measurement zone diameter have great impacts on the astigmatic values in KC. A small pupil-centred measurement zone should be considered when evaluating the astigmatism in KC.

In vitro optical quality of monofocal aspheric toric intraocular lenses: effect of cylindrical power

PURPOSE

To assess the in vitro optical quality of monofocal aspheric toric intraocular lenses (IOLs) as a function of the cylindrical power.

METHODS

The in vitro optical quality of the AcrySof IQ Toric IOLs SN6AT2, SN6AT3, SN6AT4, SN6AT5 and SN6AT6 (Alcon Laboratories Inc., Forth Worth, TX, USA) was assessed with an instrument conceived for measuring Zernike's coefficients at 3.0- and 5.0-mm apertures. As a reference, the aspheric monofocal lens AcrySof IQ Aspheric SN60WF (Alcon Laboratories Inc., Forth Worth, TX, USA) was also measured. The area of visibility and cut-off frequency were used to describe the modulation transfer function (MTF) of each lens; meanwhile, the light in the bucket and the diameter of a circular area centred on the point-spread function (PSF) peak that captures 50% of the light energy were used to describe the PSF of each lens. Finally, an image simulation was computed from the Zernike values with reference purposes.

RESULTS

Small differences were found on the metrics used for describing the MTF and PSF of the lenses at both tested apertures, but these were not statistically significant (p > 0.05). Furthermore, the image simulation showed that these differences would not have clinical relevance at all.

CONCLUSIONS

The optical performance of the AcrySof IQ toric IOLs in terms of MTF and PSF is good and seems to be independent of the cylindrical power and similar to a non-toric aspheric lens.

Clinical outcomes of new toric trifocal diffractive intraocular lens in patients with cataract and stable keratoconus: Six months follow-up

PURPOSE

To evaluate the clinical results of toric trifocal diffractive intraocular lens in eyes with cataract and mild keratoconus.

METHODS

Five keratoconus patients (10 eyes) that had bilateral AT LISA 939 implantation were selected and had followed in 3-time horizons of 1, 3, and 6 months. Patients were 46 to 65 years old age, corneal astigmatism of (2.00 D at 6.75 D) and cataract that all of them needed cataract surgery. The distance, intermediate and near visual acuities, defocus curve, ocular aberrations, contrast sensitivity, were measured as effectiveness criteria.

RESULTS

Average of binocular uncorrected distance visual acuity (UDVA) improved from 0.72 log MAR ± 0.11 (SD) to 0.04 ± 0.04 (P < 0.05) log MAR, average of uncorrected binocular intermediate visual acuity (UIVA) (80 cm) improved from 0.52 ± 0.07 log MAR to 0.14 ± 0.04 (P < 0.05) log MAR, and average of binocular uncorrected near visual acuity (UNVA) improved from 0.48 ± 0.09 log MAR to 0.02 ± 0.07 (P < 0.05) log MAR at 6 months, respectively. Contrast sensitivity testing showed acceptable results, the binocular defocus curve corroborate were in appropriate good visual acuity even at the intermediate distances, by a gentle slope less than log MAR 0.2 at -1.5 D, with regard to the best distance visual acuity at the 0 D defocus.

CONCLUSIONS

Trifocal AT LISA 939MP IOLs provided appropriate distances, near and intermediate of the visual results. Prediction of the refractive results and optical performances were good.