Correction of Astigmatism by a Single-Focus Toric Intraocular Lens during Cataract Surgery: Refractive State and Visual Acuity

Purpose: the main purpose of study is to obtain a better visual outcome after implantation of a monofocal toric IOLs by accurate measurement, calculations and visual assessment.Methods. Fifty eyes with astigmatism of more than 2.5 D were included in a hospital-based prospective study. A biometric evaluation is done by Lenstar. Barette's toric calculation method is used to measure toric IOLs power. In a vertical position, preoperative axis marking was done by both bubble marker and direct slit beam. On table, in a horizontal position, axis marking was reassessed. After phacoemulsification, a monofocal Supra Phob toric IOL was implanted and rotated to match corneal axis marking. Best-corrected visual acuity was measured postoperatively at 1 and 3 months.Results. Reduction of mean of refractive astigmatism was reported postoperatively from 4.0 ± 0.79 preoperatively to 0.7 ± 0.28 at 1 month and 0.6 ± 0.27 at 3 months postoperatively. In whole, 96 % has residual astigmatism less than 1 D at 3 months postoperatively, while 8 % eyes had residual astigmatism more than 1 D. In whole, 76 % patients had IOLs rotation of less than or equal to 5°, 20 % patients had it between 6° and 10° and 4 % eyes had more than 10° at day 7 postoperatively, in which repositioning of IOLs was required.Conclusion. To reduce postoperative residual astigmatism after toric IOLs and to get better results, accurate measurement of parameters and proper calculation are essential.

The Effect of Toric Intraocular Lens Implantation in Irregular Corneal Steep and Flat Meridian

Purpose. To evaluate the effect of toric intraocular lens implantation in cataract patients with irregular corneal steep and flat meridian. Methods. Data of 112 eyes of 78 patients who underwent toric intraocular lens implantation were analyzed retrospectively. Steep meridian deviations (not 180°) and steep and flat meridian deviations (not 90°) were classified as 0, 1–9, 10–19, 20–29, 30–39, and over 30°. Meridian deviation was measured with a sagittal map of a rotating Scheimpflug camera (Pentacam®: Oculus, Wetzlar, Germany) using PicPickTools (NGWIN, Seoul, Korea). Results. Residual astigmatism (D) of 0 (0.51 ± 0.13, 0.55 ± 0.15) and 1–9 (0.61 ± 0.16, 0.66 ± 0.19) groups were significantly lower than that of 10–19 (0.92 ± 0.24, 0.90 ± 0.28), 20–29 (0.10 ± 0.32, 1.01 ± 0.35), and over 30° groups (1.12 ± 0.37, 1.14 ± 0.40) both in steep meridian deviations and horizontal and vertical meridian deviations at 6 months ( P < 0.05 ). Postoperative mean UCVA (logMAR) of 0 (0.09 ± 0.04, 0.09 ± 0.05) (logMAR) and 1–9 (0.10 ± 0.04, 0.11 ± 0.08) groups was significantly improved compared to that of 10–19 (0.14 ± 0.05, 0.17 ± 0.10), 20–29 (0.18 ± 0.08, 0.21 ± 0.10), and over 30° groups (0.20 ± 0.09, 0.22 ± 0.11) both in steep meridian deviations and horizontal and vertical meridian deviations at 6 months ( P < 0.05 ). Conclusions. Correction of astigmatism with toric intraocular lens implantation is not accurate in corneas with steep meridian deviations and steep and flat meridian deviations of more than 10°. Therefore, care should be taken when we perform toric intraocular lens implantation in patients with irregular corneal meridian.

Tactics of Two-Stage IOL Implantation in Difficult Refractive Cases

In a number of complex refractive cases, the achievement of an accurate refractive result cannot be guaranteed. Simultaneous implantation of a toric or multifocal IOL for the correction of complex ametropias may be accompanied by a significant deviation from the target refraction. The tactics of two-stage implantation with the usage of an additional Sulcoflex IOL for the final correction of astigmatism and possible residual spherical ametropia allows achieving emmetropia. In our study, this method was used in 15 patients with difficult refractive cases. Toric, multifocal, and multifocal toric Sulcoflex IOL were used. Implantation of all Sulcoflex modifications was performed through a 2.4 mm temporal incision using wound assisted technology. In cases of high degree hypermetropia, preventive iridectomy was performed using a 23G vitrectome. The target refraction was achieved in the entire observation group. In the postoperative period, no significant level of ophthalmic hypertension was registered. No cases of introlens opacification, iridocyclitis, or rotational instability were registered either.The method of two-stage IOL implantation allows achieving the target refraction in difficult refractive situations with almost guaranteed accuracy. The calculation method provides good predictability of the refractive result. This technology significantly expands the indications for intraocular correction using toric and multifocal IOL, as well as the limits of correction of high degree astigmatism. Our Sulcoflex IOL implantation experience has shown their high efficiency and safety.

Comparison of penetrating femtosecond laser-assisted astigmatic keratotomy and toric intraocular lens implantation for correction of astigmatism in cataract surgery

This study tried to compare the clinical outcomes of femtosecond laser-assisted astigmatic keratotomy (FSAK) and toric intraocular lens (IOL) implantation for astigmatism correction and identify factors affecting the efficacy of FSAK and toric IOL implantation in astigmatism correction. This retrospective case series comprised patients with corneal astigmatism ranging between 0.5 D and 4.5 D. Patients underwent FSAK or toric IOL implantation for cataract treatment and correction of astigmatism at the Samsung Medical Center, a tertiary surgical center, between April 2016 and December 2018. All patients underwent examination before and at three months after the surgery for comparative evaluation of refractive astigmatism, corneal high order aberrations and irregularity index. The astigmatism correction was analyzed by the Alpins method. Subgroup analysis of preoperative factors was based on the extent of target-induced astigmatism (TIA), the degree of astigmatism, and astigmatism classification based on topography. Thirty-one eyes underwent toric IOL implantation and 35 eyes underwent FSAK. The refractive astigmatism was significantly decreased in both toric IOL (P = 0.000) and FSAK group (P = 0.003). The correction index (CI) of refractive astigmatism was 0.84 ± 0.39 in the toric IOL and 0.71 ± 0.60 in the FSAK group. There was no difference between the two groups (P = 0.337). The CI of the FSAK group was significantly lower than in the toric IOL group when TIA was more than 1.5 D (P = 0.006), when correcting against-the-rule (P = 0.017), and limbus-to-limbus astigmatism (P = 0.008). In conclusion, toric IOL implantation is an effective and safe procedure for correcting preoperative astigmatism in cataract surgery in the short-term observation.

Corneal incision on steepest meridian in phacoemulsification, could it correct the corneal astigmatism?

Introduction: Cataract surgery is regarded as refractive surgery when we are aiming at eliminating corneal astigmatism. So when planning a surgery both spherical and astigmatic components should be taken into account to achieve emmetropia postoperativelyPurpose: Measuring the changes of keratometric reading (K1, K2) after phacoemulsification surgery with planned incision on the steepest meridian in 50 eyes presenting as well with corneal astigmatism checking if this planned incision on steepest meridian could be an effective method or not to decrease the corneal astigmatism.Patients and Methods: A prospective study included 50 eyes of 35 patients that had immature senile cataract with corneal astigmatism more than 1 Diopter. Patients had been recruited and followed up in private eye center in Cairo. Phacoemulsification was done in all cases with placing the main clear corneal incision (0.5 mm from anatomical limbus, 2 mm tunnel length, 3 mm widths) on the steepest meridian. Follow up of patients included UCVA and BCVA at recorded 3 visits; 1 week, 1 month and 3months postoperatively, K-reading changes after 3 months postoperatively detected with pentacam, also, slit-lamp to assess both anterior and posterior segments.Results: this study showed a statistically significant change of front corneal astigmatism of 0.70 D and of 0.07 D of back corneal astigmatism.Conclusion: This method is effective in mild degree corneal astigmatism (up to 1D), while higher degree of astigmatism may need different method of intervention to be more effective in correction of astigmatism. We recommended measuring the IOL power depending on expected postoperative keratometric reading.

Astigmatism correction with toric implantable collamer lens in low and high astigmatism groups

Purpose: To analyze the target induced astigmatism (TIA), surgically induced astigmatism (SIA), difference vector (DV), and correction index (CI) in the correction of astigmatism with phakic lenses, and its influence on visual acuity, and to analyze the safety and efficacy indexes of the correction of high and low power astigmatism with toric phakic lenses. Design: Retrospective comparative study. Methods: The medical records of patients that were operated on at the research center during the period were analyzed. Results were divided into Low Astigmatism Group – LAG (33 eyes) and High Astigmatism Group – HAG (93 eyes) according to the implanted toric ICL lens power. Preoperative refraction and resultant postoperative refraction were analyzed by vector analysis. Visual acuity pre and postop, with and without optical correction, were compared. Results: A total of 126 eyes were studied. The average preop refraction was −5.02 D sphere with −2.61 D cylinder. The average ICL lens power implanted was −8.31 D sphere +2.77 D cylinder. Refractive remaining was −0.01 ± 0.11 D sphere −0.15 ± 0.28 D cylinder. The arithmetic average angle of error in the astigmatism correction was 1.08°. The resultant cylinder was −0.03 ± 0.12 D and −0.19 ± 0.30 D in the low and high astigmatism groups, respectively, with a mean UDVA −0.01 ± 0.10 and 0.01 ± 0.16 and CDVA −0.03 ± 0.08 and −0.01 ± 0.17 for each group. The safety and efficacy indexes for the low astigmatism group were 1.09 ± 0.16 and 1.05 ± 0.17, respectively, with 1.11 ± 0.17 and 1.06 ± 0.16 for the high astigmatism group. Conclusions: The correction of astigmatism by the implantation of toric phakic lenses of the posterior chamber is safe and effective, independently of the amount of cylinder corrected.

Clinical examples of the effective correction of low astigmatism for improving vision

In today’s world, the extensive visual load increases the demands on the quality of optical correction. Inadequate optical correction results in additional load on the accommodation system of the eye, increased fatigue, and complaints of asthenopia. Full optical correction is an essential requirement for the correct functioning of a visual analyzer. However, if baseline impairments of accommodation response (fusion) are not considered, full optical correction (eyeglasses or contact lenses) provokes visual discomfort. Daily disposable contact lenses (CL) with power change for each additional month is helpful in these cases, thereby allowing for a stepwise transition to the complete correction of ametropias and recovery of physiological accommodation, convergence, and better central and binocular vision quality. Prescription of spherical (not toric) CL, whose optical power was calculated by the spherical equivalent of sphero-cylindrical correction, is a typical error when correcting low astigmatism. This error negatively affects accommodative response and visual working capacity. A complete correction of astigmatism (even a low one) is required for visual recovery to reduce visual fatigue and improve working capacity and academic performance. When prescribing optical correction, binocular vision patterns and a dominant eye should be considered. Keywords: astigmatism, accommodation, binocular vision, visual discomfort, asthenopia, toric soft contact lenses. For citation: Lobanova I.V., Rybakova E.G., Romanova T.B. Clinical examples of the effective correction of low astigmatism for improving vision. Russian Journal of Clinical Ophthalmology. 2021;21(4):249–252 (in Russ.). DOI: 10.32364/2311-7729-2021-21-4-249-252.

The Effect of Toric Intraocular Lens Implantation in Irregular Corneal Steep and Flat Meridian.

Purpose: To evaluate the effect of toric intraocular lens implantation in cataract patients with irregular corneal steep and flat meridian. Methods: Data of 112 eyes of 78 patients who underwent toric intraocular lens implantation were analyzed retrospectively. Steep meridian deviations (not 180 degrees) and steep and flat meridian deviations (not 90 degrees) were classified as 0, 1~9, 10~19, 20~29, 30~39, and over 30 degrees. Meridian deviation was measured with Sagittal map of rotating Scheimpflug camera (Pentacam®: Oculus, Wetzlar, Germany) using PicPickTools (NGWIN, Seoul, Korea). Results: Residual astigmatism (D) of the 0 (0.48±0.12, 0.53±0.12) and the 1~9 (0.59±0.15, 0.63±0.17) were significantly lower than those of 10~19 (0.85±0.21, 0.85±0.26), 20~29 (0.96±0.31, 0.99±0.34), and over 30 degrees groups (1.06±0.36, 1.02±0.38) both in steep meridian deviations and horizontal and vertical meridian deviations at 2 months (P< 0.05). Postoperative mean UCVA (logMAR) of 0 (0.08±0.03, 0.08±0.03) (logMAR) and 1~9 (0.09 ± 0.04, 0.08 ± 0.04) were significantly improved compared to those of 10~19 (0.13±0.04, 0.15±0.05), 20~29 (0.16±0.05, 0.17±0.05), and over 30 degrees groups (0.19±0.07, 0.18±0.06) both in steep meridian deviations and horizontal and vertical meridian deviations (P< 0.05).Conclusions: Correction of astigmatism with toric intraocular lens implantation is not accurate in cornea with steep meridian deviations and steep and flat meridian deviations of more than 10 degrees. Therefore, care should be taken when we perform toric intraocular lens implantation in patients with irregular corneal meridian.

Consequences of Mismatch, Misalignment and Rotation of Toric Intraocular Lenses in Refractive Cataract Surgery Part 1. It Ain’t 30. The True Angle of Doom

PurposeTo demonstrate that the total loss of astigmatism as a consequence of misalignment or rotation of a toric intraocular lens (tIOL) can occur much earlier than the widely believed and taught 30 degrees. To give a precise surgically useful estimate of that value. To clarify the role of mismatch and misalignment of toric intraocular lenses in cataract surgery beyond what is commonly recognized in the literature and make corresponding surgical recommendations.SettingPrivate Practice and Research Center. The EYE Center. Champaign, IL, USA.DesignFormal Analytical StudyMethodsThe astigmatism addition approach is used in its simplest form along with analytical tools to derive new results concerning mismatch, misalignment and rotation of toric intraocular lenses.ResultsThe often stated results of total loss of astigmatic correction by 30-degree rotation and 3.3 % loss per degree represent a usually poor approximation to realistic surgical cases. We show how they constitute a very special case in the context of a more general framework relevant to procedures performed by refractive cataract surgeons dealing with the surgical correction of astigmatism with tIOLs. Total loss of astigmatic correction can occur with as little as 20 degrees of misalignment and less than 10 degrees of tIOL rotation. A practical approximation for that angle of doom, Δ, in the surgically relevant range can be expressed by Δ ≈ 30 − 15 ω degrees, where is the fractional overcorrection of L, the cylinder of the tIOL, and A, the astigmatism to be corrected. Similarly for undercorrection we show that Δ ≈ 30 + 15 u degrees where represents the corresponding fractional undercorrection. That is to say the angle of doom is extended beyond the 30 degrees for cases of undercorrection of the astigmatism. We also demonstrate that overcorrection of astigmatism results in a significantly faster decline in astigmatism correction per degree of misalignment/rotation. The significant clinical implications and surgical recommendations, including for optimal degree of overcorrection, are a natural consequence of these novel results.ConclusionsTotal loss of astigmatism correction can occur at a significantly smaller angle than commonly believed and overcorrected astigmatism residual rises with tIOL misalignment or rotation significantly faster than undercorrected astigmatism. We provide the methodology and explicit solution for determining this behavior.