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.

Short-term clinic observation of misalignment and rotational stability after implantable collamer lens implantation

PURPOSE

We aimed to investigate misalignment (tilt and decentration) and rotational stability of the implantable collamer lens V4c 6 months after implantation and to explore the potential risk factors associated with postoperative misalignment and rotation.

METHODS

A total of 36 eyes of 36 patients with high myopia and myopic astigmatism who underwent implantable collamer lens V4c implantation were included in this study. Tilt, decentration, and rotation of the implantable collamer lens were assessed postoperatively at l week, 1 month, 3 months, and 6 months. Correlation analysis was used to identify the potential risk factors for implantable collamer lens tilt, decentration, and rotation at 6 months postoperatively. Higher-order aberration was measured to evaluate the effect of implantable collamer lens misalignment on visual quality at pupil diameters of 4.0 mm and 6.0 mm.

RESULTS

The tilt and decentration at the last follow-up were 2.43 ± 1.35° and 0.278 ± 0.160 mm, respectively. There was a significant positive correlation between tilt and decentration (r = 0.31, P = 0.046). No significant correlation was detected between implantable collamer lens decentration and internal higher-order aberrations (P > 0.05). The degree of implantable collamer lens rotation (3.11 ± 2.00°) was significantly associated with the vault (r =  - 0.422, P = 0.01), while it was positively associated with the preoperative anterior chamber depth (r = 0.36, P = 0.034). No significant correlation was found between postoperative astigmatism and rotation (r =  - 0.07, P = 0.351).

CONCLUSIONS

The implantable collamer lens V4c provides relatively stable misalignment and rotation after implantation. The ICL lens vault is a potential risk factor for postoperative implantable collamer lens rotation. The absolute value of decentration and tilt was relatively small, which showed no correlation with internal higher-order aberration in short-term observation.

Linear optics of the eye and optical systems: a review of methods and applications

The purpose of this paper is to review the basic principles of linear optics. A paraxial optical system is represented by a symplectic matrix called the transference, with entries that represent the fundamental properties of a paraxial optical system. Such an optical system may have elements that are astigmatic and decentred or tilted. Nearly all the familiar optical properties of an optical system can be derived from the transference. The transference is readily obtainable, as shown, for Gaussian and astigmatic optical systems, including systems with elements that are decentred or tilted. Four special systems are described and used to obtain the commonly used optical properties including power, refractive compensation, vertex powers, neutralising powers, the generalised Prentice equation and change in vergence across an optical system. The use of linear optics in quantitative analysis and the consequences of symplecticity are discussed. A systematic review produced 84 relevant papers for inclusion in this review on optical properties of linear systems. Topics reviewed include various magnifications (transverse, angular, spectacle, instrument, aniseikonia, retinal blur), cardinal points and axes of the eye, chromatic aberrations, positioning and design of intraocular lenses, flipped, reversed and catadioptric systems and gradient indices. The optical properties are discussed briefly, with emphasis placed on results and their implications. Many of these optical properties have applications for vision science and eye surgery and some examples of using linear optics for quantitative analyses are mentioned.

Calculation of equivalent and toric power in AddOn lenses based on a Monte Carlo simulation

BACKGROUND

Additional lenses implanted in the ciliary sulcus (AddOn) are one option for permanent correction of refractive error or generate pseudoaccommodation in the pseudophakic eye. The purpose of this paper was to model the power and magnification behaviour of toric AddOn and to show the effect sizes with a Monte-Carlo simulation.

METHODS

Anonymized data of a cataractous population uploaded for formula constant optimization were extracted from the IOLCon platform. After filtering out data with refractive spherical equivalent (RSEQ) between -0.75 to 0.25 dpt and refractive cylinder (RCYL) lower than 0.75, for each of the N=6588 redcords a toric AddOn was calculated which transfers the refraction error from spectacle plane to AddOn plane using a matrix-based calculation strategy based on linear Gaussian optics. The equivalent (AddOnEQ) and toric (AddOnCYL) power of the AddOn and the overall lateral magnification change and meridional magnification was derived for the situations before and after AddOn implantation, and a linear modelling was fitted for all 4 parameters.

RESULTS

RSEQ is the dominant effect size in the prediction of AddOnEQ and overall change in magnification (ΔM) , whereas the lens position (LP), corneal thickness (CCT) and mean corneal radius (CPa) play a minor role. In a simplified model AddOnEQ can be estimated by 0.0179 + 1.4104 · RSEQ. RCYL and corneal radius difference (CPad) are the dominant effect sizes in the prediction of AddOnCYL and the change in meridional magnification (ΔMmer) , whereas LP, CCT, CPa and RSEQ play a minor role. In a simplified model AddOnCYL can be predicted by -0.0005+ 0.0328 · CPad + 1.4087 · RCYL. Myopic eyes gain in overall magnification whereas in hyperopic eyes we observe a loss. Meridional distortion could be in general reduced to 35% on average with a toric AddOn.

CONCLUSION

Our simulation shows that with a linear model the equivalent and toric AddOn power as well as overall change in magnification, meridional distortion before and after AddOn implantation as well as the reduction in meridional distortion can be easily predicted from the biometric data in pseudophakic eyes with moderate refractive error.

The Castrop formula for calculation of toric intraocular lenses

Purpose

To explain the concept behind the Castrop toric lens (tIOL) power calculation formula and demonstrate its application in clinical examples.

Methods

The Castrop vergence formula is based on a pseudophakic model eye with four refractive surfaces and three formula constants. All four surfaces (spectacle correction, corneal front and back surface, and toric lens implant) are expressed as spherocylindrical vergences. With tomographic data for the corneal front and back surface, these data are considered to define the thick lens model for the cornea exactly. With front surface data only, the back surface is defined from the front surface and a fixed ratio of radii and corneal thickness as preset. Spectacle correction can be predicted with an inverse calculation.

Results

Three clinical examples are presented to show the applicability of this calculation concept. In the 1st example, we derived the tIOL power for a spherocylindrical target refraction and corneal tomography data of corneal front and back surface. In the 2nd example, we calculated the tIOL power with keratometric data from corneal front surface measurements, and considered a surgically induced astigmatism and a correction for the corneal back surface astigmatism. In the 3rd example, we predicted the spherocylindrical power of spectacle refraction after implantation of any toric lens with an inverse calculation.

Conclusions

The Castrop formula for toric lenses is a generalization of the Castrop formula based on spherocylindrical vergences. The application in clinical studies is needed to prove the potential of this new concept.

Clinical Effect and Rotational Stability of TICL in the Treatment of Myopic Astigmatism

Purpose

To investigate the clinical outcomes and possible risk factors associated with rotational stability after the implantation of a V4c toric implantable Collamer lens (TICL) for the correction of moderate to high myopic astigmatism.

Methods

A total of 112 eyes of 66 patients with moderate to high myopic astigmatism underwent TICL implantation. All patients were followed up for more than 1 year. The uncorrected and best-corrected visual acuity (UCVA and BCVA), astigmatism and spherical equivalent, intraocular pressure, vault, endothelial cell morphometry, and rotation of the TICL axis were assessed at l day, 1 week, 1 month, 3 months, 6 months, and 12 months postoperatively. Postoperative rotation was defined as the angle between the intended axis and the achieved axis. Regression analysis was used to investigate the possible risk factors for TICL rotation postoperatively.

Results

The mean efficacy index and safety index 12 months postoperatively were 1.03 ± 0.09 and 1.05 ± 0.10, respectively. All patients had the same or better visual acuity than preoperatively. The mean astigmatism value decreased from -1.86 ± 0.79 D preoperatively to -0.37 ± 0.35 D. The mean absolute axis deviation of the TICL at the last follow-up was 2.75 ± 2.04° (range, 0°∼11°). The mean manifest refraction spherical equivalent (MRSE) changed from -9.04 ± 2.67 D preoperatively to -0.67 ± 0.51 D postoperatively. The logistic regression demonstrated that the absolute degree of TICL rotation had a significant association with the fixation angle of the TICL and the size of the lens (P=0.003, P=0.026, resp.).

Conclusion

The results of our study support that TICL implantation is safe, effective, and predictable in the treatment of moderate to high myopic astigmatism, with relatively good postoperative rotational stability.

Comparison of the Orientation of the Corneal Steep Meridian Determined by Image-Guided System and Manual Method in the Same Eye

Purpose

To evaluate the difference between the preoperative marking methods for toric intraocular lens (IOL) implantations using an image-guided system (IGS) and the manual marking method in the same eye.

Patients and Methods

In this retrospective case series, 82 patients (101 eyes) who underwent cataract surgery using both manual and IGS (VERION, Alcon  Laboratories) marking were enrolled. First, preoperative reference marks were placed at 6 o’clock and 3 or 9 o’clock position under slit-lamp biomicroscope in the outpatient department using the manual method. Using the reference unit of IGS, the ocular surface data were captured and overlaid. The difference was then measured (preoperative axis misalignment). In the operating room, the orientation of the steep meridian of the manual method was determined based on this reference mark under the surgical microscope. Just before surgery, the digital degree gauge of IGS was overlaid on the ocular surface, and the difference was then measured (total axis misalignment). We calculated the intraoperative axis misalignment by subtracting preoperative axis misalignment from the total axis misalignment.

Results

Mean absolute preoperative, intraoperative, and total axis misalignment values were 3.87±3.95 degrees, 5.46±4.42 degrees, and 4.98±4.49 degrees, respectively. In preoperative, intraoperative, and total misalignment, the ratios of 10 degrees or greater were 10 (14.7%), 12 (17.6%), and 20 (19.8%) eyes, respectively.

Conclusion

The manual method that determines the fixed position of the toric intraocular lens (IOL) may cause large misalignment compared with the IGS, suggesting that using manual method could sometimes result in a large misalignment of toric IOL implantation.

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Quality of images with toric intraocular lenses

PURPOSE

To objectively evaluate the image quality obtained with toric intraocular lenses (IOLs) when misaligned from the intended axis.

SETTING

University Eye Clinic and the Department of Industrial and Information Engineering, University of Trieste, Trieste, Italy.

DESIGN

Experimental study.

METHODS

An experimental optoelectronic test bench was created. It consisted of a high-resolution monitor to project target images and an artificial eye. The system simulates the optical and geometric characteristics of the human eye with an implanted toric IOL. A 3.00 diopters corneal astigmatism was simulated. Images reproduced by the optical system were captured according to different IOL axis positions. The quality of each image was analyzed using the visual information fidelity (VIF) criterion. The VIF reduction was calculated at each IOL rotational step.

RESULTS

A 5-degree IOL axis rotation from the intended position determined a decay in the image quality of 7.03%. Ten degrees of IOL rotation caused an 11.09% decay of relative VIF value. For a 30-degree rotation, the VIF decay value was 45.85%. Finally, the image decay with no toric correction was 56.70%.

CONCLUSIONS

The more the objective quality of the image decays progressively, the further the axis of the IOL is rotated from its intended position. The reduction in image quality obtained after 30 degrees of toric IOL rotation was less than 50% and after 45 degrees, the image quality was the same as that of no toric correction.

Comparison of clinical outcomes among 3 marking methods for toric intraocular lens implantation

PURPOSE

To compare the clinical outcomes of 3 marking methods for toric intraocular lens (IOL) implantation in cataract patients.

METHODS

This study included 48 eyes of 48 cataract patients who underwent cataract surgery with toric IOL implantation. The rotational errors of 3 marking methods-the iris pattern marking method (iris pattern group), the pendulum marking method (pendulum group), and the 3-point marking method (3-point group)-were assessed.

RESULTS

The respective rotational errors were 4.0° ± 3.1° (mean ± SD), 5.3° ± 4.1°, and 7.3° ± 6.0°. The iris pattern group had significantly (P = 0.048) smaller rotational errors than did the 3-point group; no significant difference was found between the iris pattern and pendulum groups. However, the differences in postoperative uncorrected distance visual acuity and astigmatism did not reach significance among the 3 groups.

CONCLUSION

The refractive and visual results of toric IOL implantation using the 3-point marking method were comparable to the other methods evaluated in this study, although the accuracy of the axis alignment of the toric IOLs was significantly lower than that obtained with the iris pattern method.

Comparison of 3 marking techniques in preoperative assessment of toric intraocular lenses using a wavefront aberrometer

PURPOSE

To assess the accuracy of 3 corneal horizontal meridian marking techniques using the iTrace Surgical Workstation in preoperative assessment for toric intraocular lens (IOL) implantation.

SETTING

Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea.

DESIGN

Prospective comparative observational study.

METHODS

Patients were allocated into 3 groups. Three techniques-marking with a nonpendular marker with a surgeon's direct visualization, slitlamp-assisted marking with a pendulum-attached marker, and slitlamp-assisted marking with a horizontal slit beam-were used to perform the horizontal meridian marking. The marks were immediately documented and aligned with the Zaldivar toric caliper transparent topographic map. Using a horizontal reference meridian determined by the toric caliper, the accuracy of corneal horizontal marking techniques was quantitatively evaluated by determining the rotational deviation and vertical misalignment.

RESULTS

For rotational deviation, the pendular marking showed the fewest errors to the horizontal reference meridian (mean error -0.66 degrees; mean absolute error [MAE] 3.77 degrees). There was a significant difference between the pendular marking and the surgeon's direct visual marking. For the MAE, the pendular marking showed less deviation than the surgeon's direct visual marking and the horizontal slit-beam marking. With vertical misalignment, there was no significant difference between the 3 different corneal horizontal meridian marking techniques.

CONCLUSION

The slitlamp-assisted technique with the pendulum-attached marker was more precise than marking with a nonpendular marker with a surgeon's direct visualization and marking with a horizontal slit beam in preoperative assessment for toric IOLs.

FINANCIAL DISCLOSURE

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

Technology and Intraocular Lenses to Enhance Cataract Surgery Outcomes-Annual Review (January 2013 to January 2014)

PURPOSE

This article is aimed to provide a clinical update on recent developments in cataract surgical techniques, with specific focus on femtosecond laser technology. The article also focuses on recent improvements in the technology used in implanting intraocular lenses (IOLs).

DESIGN

Literature review.

METHODS

The authors conducted a review of literature available in the last 12 months in the English language using PubMed. The period used to conduct the literature search was from January 1, 2013, to December 31, 2013. The following search terms were used during the PubMed search: phacoemulsification, femtosecond laser, toric IOLs, multifocal IOLs, multifocal toric IOLs, manual small-incision cataract surgery, outcomes, surgically induced astigmatism, rotational stability, trifocal IOLs, laser cataract surgery, safety, and efficacy.

RESULTS

This review incorporates selected original articles that provide fresh insights and updates on the fields of toric and multifocal IOLs, femtosecond laser cataract surgery, and manual small-incision cataract surgery. Particular attention has been paid to observational, randomized controlled clinical trials, experimental trials, and analyses of larger cohorts with prospective and retrospective study designs. Letters to the editor, unpublished works, and abstracts do not fall under the purview of this review.

CONCLUSIONS

This review is not designed to be all-inclusive. It highlights and provides insights on literature that is most useful and applicable to practicing ophthalmologists.

Evaluating the effect of splitting cylindrical power on improving patient tolerance to toric lens misalignment

PURPOSE

Evaluating the impact of splitting toric power on patient tolerance to misorientation such as with intraocular lens rotation.

SETTING

University vision clinic.

METHODS

Healthy, non astigmats had +1.50D astigmatism induced with spectacle lenses at 90°, 135°, 180° and +3.00D at 90°. Two correcting cylindrical lenses of the opposite sign and half the power each were subsequently added to the trial frame misaligned by 0°, 5° or 10° in a random order and misorientated from the initial axis in a clockwise direction by up to 15° in 5° steps. A second group of adapted astigmats with between 1.00 and 3.00DC had their astigmatism corrected with two toric spectacle lenses of half the power separated by 0°, 5° or 10° and misorientated from the initial axis in both directions by up to 15° in 5° steps. Distance, high contrast visual acuity was measured using a computerised test chart at each lens misalignment and misorientation.

RESULTS

Misorientation of the split toric lenses caused a statistically significant drop in visual acuity (F=70.341; p<0.001). Comparatively better acuities were observed around 180°, as anticipated (F=3.775; p=0.035). Misaligning the split toric power produced no benefit in visual acuity retention with axis misorientation when subjects had astigmatism induced with a low (F=2.190, p=0.129) or high cylinder (F=0.491, p=0.617) or in the adapted astigmats (F=0.120, p=0.887).

CONCLUSION

Misalignment of toric lens power split across the front and back lens surfaces had no beneficial effect on distance visual acuity, but also no negative effect.

Visual performance of 2 aspheric toric intraocular lenses: comparative study

PURPOSE

To compare the visual and aberrometric outcomes of 2 aspheric toric intraocular lenses (IOLs).

SETTING

Fatebenefratelli e Oftalmico Hospital, Milan, Italy.

DESIGN

Prospective randomized comparative study.

METHODS

Astigmatic patients had cataract surgery with implantation of an Acrysof SN6AT IOL (Group A) or an AT Torbi 709M IOL (Group B). The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, net refractive astigmatism, spherical equivalent (SE), IOL misalignment, and optical quality were evaluated 3 months postoperatively.

RESULTS

The study included 72 eyes. No statistically significant difference was found in UDVA, CDVA, residual refractive astigmatism, intraocular or total higher-order aberrations (Z(n,i) (order of aberrations calculated: 3≤n≤8), coma Z(3,±1), or trefoil Z(3,±2). The UDVA was 0.3 logMAR or better in all eyes and 0.1 logMAR or better in 55.5% of eyes in Group A and in 61.1% of eyes in Group B. Considering polar value analysis, 94.4% of eyes in both groups had a refractive astigmatism value within ±0.50 diopter at KP90 (polar value along 90-degree meridian). The SE was closer to emmetropia in Group A (P=.01). Intraocular lens misalignment of less than 5 degrees was present in 61.1% of cases in Group A (maximum 9 degrees) and in 66.6% in Group B (maximum 11 degrees). Spherical aberration Z(4,0) was significantly lower in Group B.

CONCLUSIONS

Both IOLs had similar clinical effectiveness in term of astigmatism correction, rotational stability, and optical quality. Eyes in Group A appeared significantly nearer to emmetropia, while the IOL in Group B induced significantly less spherical aberration.

FINANCIAL DISCLOSURE

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

Toric intraocular lenses: historical overview, patient selection, IOL calculation, surgical techniques, clinical outcomes, and complications

We present an overview of currently available toric intraocular lenses (IOLs) and multifocal toric IOLs. Relevant patient selection criteria, IOL calculation issues, and surgical techniques for IOL implantation are discussed. Clinical outcomes including uncorrected visual acuity, residual refractive astigmatism, and spectacle independency, which have been reported for both toric IOLs and multifocal toric IOLs, are reviewed. The incidence of misalignment, the most important complication of toric IOLs, is determined. Finally, future developments in the field of toric IOLs are discussed.

Evaluation of 4 corneal astigmatic marking methods

PURPOSE

To compare 4 devices used to mark the cornea before astigmatism-reducing surgery.

SETTING

Hanusch Krankenhaus, Vienna, Austria.

DESIGN

Randomized examiner-masked clinical trial.

METHODS

Patients were randomly allocated to 1 of 4 groups for preoperative corneal marking in the sitting position. The 4 methods used were marking at the slitlamp with an insulin needle, a pendular marker, a bubble marker, and a tonometer marker. The marks were then documented with a standardized photographic technique, and the rotational deviation and vertical misalignment were assessed.

RESULTS

The study enrolled 60 patients. The pendular-marking device showed the least rotational deviation to the reference meridian (mean 1.8 degrees). There was no statistically significant difference between slitlamp marking and pendular marking (P = .05); however, there was a significant difference between the pendular marker and the bubble marker and between the pendular marker and the tonometer marker (P = .01 and P < .01, respectively). The least vertical misalignment was observed with the slitlamp-marking device (mean 0.28 mm). There was no statistically significant difference in vertical misalignment between the 4 groups.

CONCLUSIONS

All marking devices showed a slight deviation to the horizontal reference meridian. Because small deviations of the meridian can result in a relevant reduction in the astigmatism-reducing effect with toric intraocular lenses, accurate marking of the cornea before surgery is critical due to the variable cyclotorsion caused by a change from the upright to the supine position.

FINANCIAL DISCLOSURE

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

Simple and accurate alignment of toric intraocular lenses and evaluation of their rotation errors using anterior segment optical coherence tomography

PURPOSE

To describe a new method of alignment of toric intraocular lenses (IOLs) and evaluation of their rotation errors using anterior segment optical coherence tomography (AS-OCT).

METHODS

Twenty-nine eyes of 22 patients who had cataract extraction and implantation of an acrylic toric IOL were included. The new AS-OCT method was used for the alignment of toric IOLs and evaluation of their rotation errors. These rotation errors were evaluated and compared with those measured using the internal map of a wavefront aberrometer.

RESULTS

The mean rotation error ± standard deviation (SD) of the toric IOLs evaluated by AS-OCT was 3.2 ± 2.2° and 3.2 ± 2.4° at 1 week and 1 month after surgery, respectively. The mean difference in the reference axis between the visits was 1.8 ± 2.1°. The mean difference between the rotation errors of the alignment axes measured by AS-OCT and the internal map was 2.5 ± 1.9° (P = 0.037).

CONCLUSION

The current method is clinically useful not only for the accurate alignment of toric IOLs but also for evaluating their rotation errors.

Refractive lens exchange with toric intraocular lenses in keratoconus

PURPOSE

To report the clinical characteristics and surgical outcomes of patients with nonprogressive keratoconus treated with in-the-bag toric intraocular lens (IOL) implantation.

METHODS

A retrospective review was conducted of the medical records of patients diagnosed with keratoconus treated with refractive lens exchange (RLE) and in-the-bag toric IOL implantation (models T3 to T9, AcrySof SN60TT; Alcon Laboratories Inc). Age, pre- and postoperative uncorrected (UDVA) and corrected distance visual acuity (CDVA), objective and subjective refraction, spherical equivalent refraction, total keratometric power, total astigmatism, axis, and toric IOL model and power were analyzed. All cases had topographic and/or refractive stability for at least 1 year prior to undergoing IOL implantation.

RESULTS

Nineteen eyes of 13 patients (mean age 48.15 ± 6.6 years), including 12 patients with a topographic diagnosis of keratoconus and 1 with pellucid marginal degeneration, were evaluated. Mean follow-up after RLE was 7.89 ± 6.61 months. Mean preoperative sphere was -5.25 ± 6.40 diopters (D), and mean postoperative sphere was 0.22 ± 1.01 D (P<.001). Mean preoperative cylinder was 3.95 ± 1.30 D, which decreased to 1.36 ± 1.17 D postoperatively (P<.001). Mean pre- and postoperative spherical equivalent refractions were -7.10 ± 6.41 D and -0.46 ± 1.12 D, respectively (P<.001). Preoperative mean UDVA was 1.35 ± 0.36 D (20/447 Snellen) and postoperative mean UDVA was 0.29 ± 0.23 D (20/39 Snellen) (P<.001).

CONCLUSIONS

Toric IOL implantation may be an effective therapeutic option in the optical rehabilitation of patients with stable and nonprogressive keratoconus.

Spontaneous Rotation of a Toric Implantable Collamer Lens

We present a case of toric implantable collamer lens (TICL) spontaneous rotation in a patient with myopic astigmatism. A 23-year-old female underwent TICL implantation. Preoperative uncorrected visual acuity (UCVA) was 20/800 and 20/1200, respectively, with -7.75 -4.25 × 0° and -8.25 -5.25 × 180°. The left eye achieved an UCVA of 20/30. After 3 months of successful implantation of TICL in the left eye, the patient presented with a sudden decrease in visual acuity in the left eye. UCVA was 20/100 with a refraction of +2.50 -4.50 × 165°. We observed the toric marks with a 30° rotation from the original position and decided to reposition the TICL, obtaining a final UCVA of 20/25, which remained stable at 6 months' follow-up. TICL can present a considerable rotation that compromises visual acuity. The relocation of TICL is a safe and effective procedure to recover visual acuity due to significant spontaneous TICL rotation.

[Correction of corneal astigmatism with toric lenses : Theory and clinical aspects]

In the last decades, the implantation of pseudophakic and phakic toric lenses has become widespread for correcting corneal astigmatism: in cataract surgery cases with implantation of a posterior chamber lens and in refractive surgery cases with implantation of phakic lenses. The purpose of this educational and training article is to familiarize the reader with the application of pseudophakic and phakic toric lenses, to show which parameters are necessary for calculating toric lenses, to present a matrix-based calculation scheme for pseudophakic and phakic toric lenses, to explicitly demonstrate the step-by-step calculations with clinical examples, and to show the impact of lens dislocation (especially rotation) on refractive outcome.