Correction Of Corneal Astigmatism Research Articles

Comparative evaluation of aspheric toric intraocular lens implantation and limbal relaxing incisions in eyes with cataracts and ≤3 dioptres of astigmatism

PurposeTo compare the visual outcomes of aspheric toric intraocular lens (IOL) implantation and limbal relaxing incisions (LRI) for management of coexisting age-related cataracts and astigmatism.MethodsIn this prospective study, sixty eyes...

Optical quality of toric intraocular lens implantation in cataract surgery.

To analyze the optical quality after implantation of toric intraocular lens with optical quality analysis system. Fifty-two eyes of forty-four patients with regular corneal astigmatism of at least 1.00 D underwent implantation of AcrySof toric intraocular lens, including T3 group 19 eyes, T4 group 18 eyes, T5 group 10 eyes, T6 group 5 eyes. Main outcomes evaluated at 3mo of follow-up, included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), residual refractive cylinder and intraocular lens (IOL) axis rotation. Objective optical quality were measured using optical quality analysis system (OQAS II(®), Visiometrics, Spain), included the cutoff frequency of modulation transfer function (MTFcutoff), objective scattering index (OSI), Strehl ratio, optical quality analysis system value (OV) 100%, OV 20% and OV 9% [the optical quality analysis system (OQAS) values at contrasts of 100%, 20%, and 9%]. At 3mo postoperative, the mean UDVA and CDVA was 0.18±0.11 and 0.07±0.08 logMAR; the mean residual refractive cylinder was 0.50±0.29 D; the mean toric IOL axis rotation was 3.62±1.76 degrees, the mean MTFcutoff, OSI, Strehl ratio, OV 100%, OV 20% and OV 9% were 22.862±5.584, 1.80±0.84, 0.155±0.038, 0.76±0.18, 0.77±0.19 and 0.78±0.21. The values of UDVA, CDVA, IOL axis rotation, MTFcutoff, OSI, Strehl ratio, OV100%, OV20% and OV9% depending on the power of the cylinder of the implantation were not significantly different (P>0.05), except the residual refractive cylinder (P<0.05). The optical quality analysis system was useful for characterizing the optical quality of AcrySof toric IOL implantation. Implantation of an AcrySof toric IOL is an effective and safe method to correct corneal astigmatism during cataract surgery.

Refractive meridional corneal collagen cross-linking: a new modified technique for treatment of astigmatism

Purpose The aim of the study was to evaluate the efficacy and safety of using corneal collagen cross-linking as a refractive procedure to correct corneal astigmatism. Setting This study was conducted in Sohag University Hospital (Egypt). Design This is a prospective, nonrandomized, clinical trial study. Patients and methods Fifteen eyes of 11 patients complaining of astigmatism were treated with refractive meridional cross-linking (RMCXL). Group A included eight eyes that had undergone previous cross-linking and implantation of intracorneal rings that failed to correct the astigmatic component of keratoconus. Group B included seven eyes with astigmatism without corneal ectasia. All eyes were subjected to examination of the preoperative and postoperative uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and manifest refraction, as well as slit lamp examination of the anterior segment, keratometry, and pachymetry by corneal topographies at 1 week and at 1, 3, and 6 months' follow-up. Results In group A, the preoperative mean UDVA was 0.90 ± 0.33 (log MAR ± SD), whereas the postoperative mean UDVA was 0.78 ± 0.27. The preoperative mean CDVA was 0.60 ± 0.38, whereas the postoperative mean CDVA was 0.48 ± 0.26. The mean postoperative astigmatic correction was 1.8 ± 0.36. In group B, the preoperative mean UDVA was 0.78 ± 0.53, whereas the postoperative mean UDVA was 0.52 ± 0.23. The preoperative mean CDVA was 0.52 ± 0.26, whereas the postoperative mean CDVA was 0.30 ± 0.15. The mean postoperative astigmatic correction was 0.90 ± 0.29. Conclusion RMCXL showed good refractive correction for astigmatism in both ectatic and nonectatic corneas. RMCXL proved to be a promising new simple, effective, and safe procedure for the treatment of corneal astigmatism with reasonable patient satisfaction.

Simple technique to measure toric intraocular lens alignment and stability using a smartphone

Toric intraocular lenses (IOLs) are commonly implanted to correct corneal astigmatism at the time of cataract surgery. Their use requires preoperative calculation of the axis of implantation and postoperative measurement to determine whether the IOL has been implanted with the proper orientation. Moreover, toric IOL alignment stability over time is important for the patient and for the longitudinal evaluation of toric IOLs. We present a simple, inexpensive, and precise method to measure the toric IOL axis using a camera-enabled cellular phone (iPhone 5S) and computer software (ImageJ).

Use of a T-flex toric intraocular lens to correct clinically significant astigmatism

PurposeTo investigate the stability and effectiveness of T-flex toric intraocular lenses (IOLs) for the correction of regular corneal astigmatism during cataract surgery. MethodsFrom October 2009 to January 2014 we enrolled patients receiving phacoemulsification and T-flex toric IOL implantation in the capsular bag at the Far Eastern Memorial Hospital. The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), corneal astigmatism, refractive astigmatism, and the degree to which the IOL axis deviated from the demanded axis were recorded both before the operation and 6 months postoperatively. ResultsWe enrolled 24 eyes of 24 consecutive patients in this study. The mean spherical power of the implanted toric IOLs was 17.13 ± 4.21 D (range 6.0–24.0 D) and the mean cylindrical power of the IOLs was 3.0 ± 0.86 D (range 2.0–5.0 D). At the 6-month follow up examination, the refractive astigmatism had improved from 3.21 ± 1.50 D to 0.77 ± 0.47 D (p < 0.001) and the spherical equivalence had improved from 4.47 ± 5.43 D to 0.63 ± 0.49 D (p = 0.007). The CDVA improved from 0.81 ± 0.45 logMAR to 0.09 ± 0.11 logMAR (p < 0.001). The mean improvement from the preoperative CDVA to the postoperative UDVA was 5.3 lines on the Snellen chart. Ninety-two percent of our patients achieved a postoperative UDVA ≥20/40 and 67% achieved a postoperative UDVA ≥20/25. ConclusionThe T-flex toric IOL can effectively reduce visually significant corneal astigmatism and improve uncorrected distance visual acuity during cataract surgery.

Évaluation des performances visuelles après implantation d’une lentille intraoculaire torique à double anse en C

This study aims to demonstrate the safety and the efficacy of the Ankoris posterior chamber intraocular lens to correct corneal astigmatism at the time of cataract surgery. In this retrospective study, 52 eyes among the first 64 consecutive ones implanted with the Ankoris met the inclusion criteria. The retrospective analysis of these cases consisted mainly of the determination of the improvement in visual acuity and postoperative refraction. The analysis of the astigmatism correction itself was carried out by the Alpins method. The rotational stability of the implant was analyzed by the difference between the IOL orientation after one day and 3 months. The safety index, defined as the postoperative divided by preoperative best visual acuity, was greater than one in all cases, with a mean of 1.96. The ratio of the postoperative uncorrected visual acuity with the preoperative best-corrected acuity was 1.72. The final postoperative astigmatism was -0.40 ± 0.28 D. The percentage of astigmatism corrected was 99.3%. The error vector amplitude was 0.1 D with a nearly null orientation. The mean rotation was 2.16 ± 1.95°. The Ankoris IOL demonstrates, in this relatively large cohort, all necessary elements to establish that the IOL was able to correct corneal astigmatism at the same time as cataract surgery.

Rotational performance and corneal astigmatism correction during cataract surgery: Aspheric toric intraocular lens versus aspheric nontoric intraocular lens with opposite clear corneal incision

To compare the astigmatism-reducing effect of an aspheric toric intraocular lens (IOL) and an aspheric nontoric IOL with an opposite clear corneal incision (OCCI) in cataract surgery. Vienna Institute for Research in Ocular Surgery, Hanusch Hospital, Vienna, Austria. Prospective randomized clinical study. Patients with low to moderate corneal astigmatism scheduled for cataract surgery received an aspheric toric IOL (Lentis L-312T) or an aspheric nontoric IOL (Lentis L-312) combined with an OCCI. Keratometry and corneal tomography were performed 1 hour, 1 week, 3 months and 9 months postoperatively. Postoperative residual astigmatism was measured using an autorefractor. Rotational toric IOL stability was analyzed using retroillumination photography. Fifty-five patients were included. Three months postoperatively, the mean reduction in corneal astigmatism was 0.67 diopter (D) ± 0.58 (SD) in the toric group and 0.18 ± 0.52 D in the nontoric-OCCI group. The mean uncorrected distance visual acuity was 0.29 ± 0.30 logMAR and 0.09 ± 0.18 logMAR, respectively (P=.02). The mean refractive astigmatism was 1.02 ± 0.54 D and 0.68 ± 0.52 D, respectively (P=.05). One hour, 3 months, and 9 months postoperatively, the mean absolute IOL misalignment of toric IOLs was 4.99 ± 4.66 degrees, 13.59 ± 11.29 degrees, and 19.90 ± 14.48 degrees, respectively. The toric IOL tended to rotate significantly postoperatively. Visual acuity was good in both groups. Residual refractive cylinder was significantly lower in the toric IOL group. No author has a financial or proprietary interest in any material or method mentioned.

Correction of moderate corneal astigmatism during cataract surgery: Toric intraocular lens versus peripheral corneal relaxing incisions

To compare the astigmatism-reducing effect of a toric intraocular lens (IOL) and peripheral corneal relaxing incisions (PCRIs). Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom. Prospective masked bilateral randomized study. Cataract patients with a preoperative corneal astigmatism of 1.0 to 2.5 diopters (D) were included. All patients received a toric IOL in 1 eye and a nontoric IOL plus a PCRI in the other eye. Postoperative follow-up was at 1 hour, 1 month, and 6 months. The uncorrected distance visual acuity, corrected distance visual acuity, autorefraction (Topcon RM-8800), and subjective refraction were recorded. The IOL axis was assessed using retroillumination photographs. The study enrolled 60 eyes of 30 patients. The mean astigmatism vector reduction was 1.74 D ± 0.64 (SD) in the toric IOL group and 1.27 ± 0.76 D in the PCRI group; the difference was statistically significant (P=.042). The mean absolute rotation of the toric IOL was 2.5 ± 1.8 degrees (maximum 6.3 degrees) in the first 6 postoperative months. Astigmatism increased in the PCRI group between the 1-month and 6-month follow-up (mean 0.38 ± 0.27 D; maximum 1.00 D) (P<.001). Toric IOLs and PCRIs both reduced astigmatism; however, toric IOLs reduced astigmatism to a higher extent and they were more predictable.

Surgical management of astigmatism with toric intraocular lenses.

Correction of corneal astigmatism is a key element of cataract surgery, since post-surgical residual astigmatism can compromise the patient's uncorrected visual acuity. Toric intraocular lenses (IOLs) compensate for corneal astigmatism at the time of surgery, correcting ocular astigmatism. They are a predictable treatment. However, accurate measurement of corneal astigmatism is mandatory for choosing the correct toric IOL power and for planning optimal alignment. When calculating the power of toric IOLs, it is important to consider anterior and posterior corneal astigmatism, along with the surgically induced astigmatism. Accurate toric lens alignment along the calculated meridian is also crucial to achieve effective astigmatism correction. There are several techniques to guide IOL alignment, including the traditional manual marking technique and automated systems based on anatomic and topographic landmarks. The aim of this review is to provide an overview on astigmatism management with toric IOLs, including relevant patient selection criteria, corneal astigmatism measurement, toric IOL power calculation, toric IOL alignment, clinical outcomes and complications.

Analysis of Miscorrection after Implantation of the Toric Intraocular Lens

Purpose: To evaluate the efficacy and stability of AcrySof Toric intraocular lens (IOL) implants and to analyze the miscorrection that resulted after implantation. Methods: This retrospective study included 422 eyes of 348 patients who underwent cataract surgery with implantation of the AcrySof toric IOL between December 2011 and June 2013. We evaluated uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), keratometry and refraction preoperatively and 3 months postoperatively. The axis of implanted AcrySof Toric IOL was measured using the KR-1W aberrometer before mydriasis. At 3 months postoperatively, patients with a residual cylindrical power of 0.50 diopters (D) or more, and having an IOL rotation of 10 degrees (°) or more were considered having miscorrection. Results: UCVA (log MAR) improved from 0.58 ± 0.35 to 0.18 ± 0.26. Preoperative corneal astigmatism was 1.46 ± 0.72 D and postoperative refractive cylindrical power was 0.45 ± 0.30 D. The postoperative miscorrection was 50.5% in the T3 group, 35.7% in the T4 group, and 27.2% in the T5 group. The incidence of overcorrection was significantly higher in the T3 group than in the T4 and T5 group. In eyes with with-the-rule (WTR) astigmatism, overcorrection was found in 36.4% (32/88 eyes), while in eyes with against-the-rule (ATR) astigmatism, undercorrection was found in 37.6% of cases (44/117 eyes). There were five cases of IOL rotation at 3 months postoperatively. Conclusions: AcrySof Toric IOL was effective in correcting corneal astigmatism and had good rotational stability. However, the incidence of miscorrection, especially for overcorrection, was higher with lower power toric IOL. Patients with WTR astigmatism tend to have overcorrection, while those with ATR show a tendency toward undercorrection, suggesting that these changes considered at the time of cataract surgery. J Korean Ophthalmol Soc 2014;55(11):1636-1641

Cataract Surgery with Toric Intraocular Lens for Correction of High Corneal Astigmatism

ObjectiveTo analyze the outcomes of cataract surgery with high-power toric intraocular lens (IOL) implantation in patients with high corneal astigmatism. DesignRetrospective case series. ParticipantsTwelve eyes of 9 patients. MethodsPatients with idiopathic, pathologic, or postsurgical corneal astigmatism and a visually significant cataract were included in the study. Cataract extraction with implantation of a custom-made high-power toric IOL was performed on all patients. Outcomes included uncorrected and best corrected distance visual acuity (UDVA and BCDVA), manifest refraction, and mean and steepest keratometry. Analysis of astigmatic vectors was also performed. ResultsThe mean follow-up time was 3.75 months. At the last follow-up visit, there was a significant improvement of UDVA (1 ± 0.64 vs 0.39 ± 0.21 logMAR; p < 0.05), cylindrical refraction (–4.72 ± 1.13 vs –1.81 ± 1.10 D; p < 0.01), and refractive spherical equivalent (–4.56 ± 5.58 vs –0.36 ± 1.19 D; p < 0.05). The BCDVA improvement did not reach statistical significance. Astigmatism on the target axis was reduced by an average of 5 D (p < 0.01). ConclusionsCataract surgery with implantation of a high-power toric IOL was safe and effective in correcting high values of corneal astigmatism.

Rotational stability and visual outcome after implantation of a new toric intraocular lens for the correction of corneal astigmatism during cataract surgery

To evaluate rotational stability and the refractive and visual outcomes of a new aspheric toric intraocular lens (IOL) for correction of preexisting corneal astigmatism during routine cataract surgery. Department of Ophthalmology, Paracelsus Medical University Salzburg, Salzburg, Austria. Case series. Aspheric Bi-Flex T toric IOLs were monolaterally or bilaterally implanted after phacoemulsification in patients with topographic corneal astigmatism between 1.5 diopters (D) and 4.0 D. Preoperative IOL calculations were performed by laser interference biometry (Haigis formula). Appropriate IOL-torus alignment was facilitated by combined imaging and eye-tracking technology. Refraction and uncorrected distance (UDVA) and corrected distance visual acuities were measured 1 day, 1 week, and 1 and 3 months postoperatively. At each visit, photodocumentation in retroillumination was performed to evaluate torus position and potential toric IOL rotation. The mean refractive astigmatism decreased from 1.93 D ± 0.90 (SD) (range 0.5 to 4.0 D) to 0.30 ± 0.54 D (range 0.0 to 1.5 D) at 3 months. Patients achieved a mean UDVA of 0.05 ± 0.12 logMAR (range -0.18 to 0.30 logMAR [∼20/20]). Intraoperative to 3-month postoperative comparison of IOL axis alignment showed low levels of rotation (mean 2.12 ± 3.45 degrees; range -2 to +5 degrees). Implantation of the new aspheric toric IOL was effective, safe, and stable in correcting preexisting regular corneal astigmatism during cataract surgery. Combined imaging and eye tracking seems to be a promising technology to evaluate the correct axis for IOL torus alignment.

Astigmatism Correction With Toric IOL: Analysis of Visual Performance, Position, and Wavefront Error

To evaluate astigmatism correction, visual performance, intraocular lens (IOL) position, and wavefront error after implantation of toric IOLs in patients with cataract. This prospective study comprised 30 eyes of 30 patients with cataract who were candidates for phacoemulsification and implantation of the AcrySof toric IOL (Alcon Laboratories, Inc., Fort Worth, TX). Mean preoperative corneal keratometric and subjective refractive cylinder were 2.10 ± 0.47 and 2.17 ± 0.41 diopters (D), respectively. The refractive cylinder decreased significantly from 2.17 ± 0.41 to 0.73 ± 0.45 D (P = .001) at 180 days postoperatively. The difference between preoperative corneal astigmatism and postoperative refractive astigmatism was statistically significant (P < .05). At 180 days postoperatively, the uncorrected distance visual acuity was 0.20 logMAR (Snellen 20/32) in 100% of patients and 0.0 logMAR (Snellen 20/20) in 64% of patients. The root mean square of internal coma and trefoil aberrations showed a trend toward reduction; internal spherical aberration significantly decreased, whereas corneal trefoil aberration significantly increased (P < .05). A low amount of IOL decentration and tilt were detected at 30 and 180 days postoperatively, respectively. Toric IOL implantation is an effective procedure for correction of preexisting corneal astigmatism, improving visual performance, and inducing a low amount of higher-order aberrations. Moreover, the toric IOLs is well positioned early after surgery and stable over time.

A New Slant on Toric Intraocular Lens Power Calculation

The AcrySof Toric intraocular lens (IOL) (Alcon Laboratories, Inc., Fort Worth, TX) is designed to correct corneal astigmatism ranging from 0.67 to 4.11 diopters (D). The authors reviewed the clinical outcomes of this IOL and investigated possible improvements of the online calculator provided by the manufacturer. Review of published studies. The AcrySof Toric IOL can provide good results, although a mean overcorrection or undercorrection relative to the intended correction has been found by some authors. Stability over time has been reported to be excellent. Rotation occurs mainly in the first postoperative month and is greater in eyes with a longer axial length due to the larger capsule size. The online calculator of this IOL may be improved by considering the posterior corneal astigmatism and better calculating the conversion of the IOL cylinder from the IOL plane to the corneal plane, which may be inaccurate for two reasons. First, given the variable distance between the IOL and the cornea in short and long eyes, the fixed ratio (1.46) provided by the manufacturer cannot be used to calculate this conversion. Second, the online calculator does not take into account the effect of varying IOL sphere power. The AcrySof Toric IOL is a reliable choice to correct corneal astigmatism at the time of cataract surgery. Results will be improved once the online calculator by the manufacturer considers the posterior corneal astigmatism and the variable ratio between the toricity at the IOL and corneal plane.

Limbal relaxing incision for correcting corneal astigmatism during phacoemulsification

Objective To evaluate the efficacy of limbal relaxing incisions (LRIs) for the correction of corneal astigmatism during phacoemulsification.Methods 66 eyes of 60 patients with senile cataract and coexisting keratometric astigmatism were included in the study.Phacoemulsification with concomitant relaxing incisions was performed in 40 eyes of 35 patients in LRIs group.26 eyes of 25 patients only underwent phacoemulsification with intraocular lens implantation were in control group.All patients underwent ophthalmic examination that included uncorrected visual acuity (UCVA),best-corrected visual acuity (BCVA)and corneal topography preoperatively,1 month and 3 months postoperatively.Results Respectively comparing UCVA of two groups 1 and 3 months postoperatively,the P values were considered statistically significant(P ＜ 0.05).At preoperative and postoperative time points,the average corneal astigmatism changes were also significantly different between the two groups.(P ＜ 0.05).Conclusion LRIs performed during phacoemulsification surgery appear to be an effective procedure to reduce pre-existing corneal astigmatism and improve UCVA as well as the visual quality. Key words: Limbal relaxing incisions; Phacoemulsification; Cataract; Corneal astigmatism; Topography

Traumatic aniridia through opposite clear corneal incision in a pseudophakic eye

A 56-year-old man complaining of decreased visual acuity in his left eye visited the emergency room 1 hour after blunt trauma. Slitlamp examination showed no visible iris tissue. The corneal wound at 5 o'clock was sharp, and Seidel was negative. In the right eye, there was a main clear corneal incision (CCI) at 11 o'clock and an opposite CCI (OCCI) to correct corneal astigmatism at 5 o'clock in the left eye. Anterior chamber inflammation and hyphema resolved 4 weeks after the trauma. The intraocular lens and capsular bag were intact, and the corrected distance visual acuity returned to 20/25. To our knowledge, this is the first report of traumatic iris expulsion through a 3.0 mm OCCI. An OCCI may seal better than a main CCI, which is used in cataract surgery, because the OCCI is not used during the cataract procedure. However, surgeons should be aware of the risk for postoperative wound dehiscence associated with the OCCI.

Two-year results of AcrySof toric intraocular lens implantation in patients with combined microincision vitrectomy surgery and phacoemulsification

AimTo evaluate the effects and stability of AcrySof toric intraocular lens (IOL) implantation in patients who had combined microincision vitrectomy surgery (MIVS) and phacoemulsification for vitreoretinal diseases and cataract with...

Toric IOL for Cataract Astigmatism Eye Surgery

Objective To evaluate the effectiveness and rotational stability of Toric IOL to correct preexisting corneal astigmatism in cataract patients.Methods This Study included 37 eyes of 32 patients who underwent phacoemulsification and foldable Acrysoftoric IOL implantation from July 2008 to December 2009.As a comparison,30 eyes of 26 patients meeting the same preoperative criteria for degree of corneal cylinder were enrolled to have a Spherical (nontoric) IOL implanted.The uncorrected visual acuity (UCVA),best corrected visual acuity (BCVA),preoperative corneal astigmatism,anticipated residual astigmatism,postoperative residual astigmatism and Toric IOL axis for both study and control groups were analyzed respectively.Results In the study group,94.53％ of eyes were 0.5 or better in UCVA in 3 months after the surgery,81.07％ of eyes were 0.8 or better in UCVA and 96.92％ of eyes were 0.8 or better in BCVA.In the study group,the mean preoperative corneal astigmatism was ( 1.82 ± 0.87 ) D and the postoperative refractive cylinder was (0.63 ± 0.30) D.As a comparison,the mean postoperative refractive cylinder of the control group was (1.14 ± 0.36) D.The difference between these two groups provides a sample base for statistics analysis.The mean deviation between the actual axis and anticipated axis of study group was (3.95±3.69) degrees 1 day after operation,and (2.52 ± 1.95 ) degrees 3 months after operation.94.60％ ＜ 5degree.Conclusion Toric IOL provides cataract patients better UCVA,good rotational stability and reduce the residual astigmatism.Toric IOL implantation is an effective,safe and predictable method to correct the preexisting corneal astigmatism in cataract surgery. Key words: Cataract; Astigmatism; Lens, intraocular, toric

Effects of the toric intraocular lens on correction of preexisting corneal astigmatism

To examine the effects of a toric intraocular lens (IOL) on the correction of preexisting corneal astigmatism after cataract surgery. Fifty eyes that underwent phacoemulsification were enrolled in three group: (1) eyes with corneal astigmatism ≥1.0 diopter (D) that received a toric IOL (Alcon SN6AT) (toric), (2) eyes with astigmatism ≥1.0 D that received a nontoric IOL (high-astigmatism group), and (3) eyes with astigmatism <1.0 D that received the nontoric IOL (low-astigmatism group). Refractive and corneal astigmatism, astigmatic change, and uncorrected visual acuity (UCVA) were examined. The postoperative refractive astigmatism in the toric and low-astigmatism groups was significantly lower than that of the high-astigmatism group (P ≤ 0.0040), and the reduction in the refractive astigmatism was greater in the toric than in the high- and low-astigmatism groups (P < 0.0001), although the corneal astigmatism was greatest in the toric group, followed by the high- and low-astigmatism groups (P < 0.0001). The mean UCVA in the toric and low-astigmatism groups was better than that in the high-astigmatism group (P < 0.0001). The toric IOL proved effective in astigmatism correction, and both the residual astigmatism and UCVA in the eyes with the the toric IOL were better than those in the eyes with high astigmatism and were comparable to those in the eyes with low astigmatism.

ZERNIKE ASTIGMATISM AND VISUAL PERFORMANCE IN MYOPIC EYES BY RIGID GAS PERMEABLE CONTACT LENSES WEAR

Purpose: To investigate the effects of rigid-gas-permeable contact lens (RGP-CL) wear on Zernike astigmatism and visual performance in myopic eyes. Methods: A wavefront sensor was used to evaluate Zernike astigmatism for 21 eyes with minimum astigmatism and 18 eyes with moderate astigmatism under three different modes of refractive correction: the RGP-CL, spectacle lens correcting spherical equivalent (SL) and spectacle lens fully correcting spherical error and astigmatism (fSL). Contrast visual acuity was assessed with a VA tester at four contrast levels and two luminance backgrounds. Results: Compared to the SL wear, RGP-CL wear changed the main axis astigmatism [Formula: see text] from -0.09 ± 0.34 to 0.34 ± 0.22 for the minimum astigmatism group, while the contrast VA was improved about 0.05 LogMAR (F = 8.06, p &lt; 0.01). For the group with moderate astigmatism, significant reduction in [Formula: see text] was found for both fSL wear (t = 4.78, p &lt; 0.001) and RGP-CL wear (t = 6.29, p &lt; 0.0001). The changes in astigmatism were significantly correlated between the fSL and RGP-CL wears (r = 0.897, p &lt; 0.0001 for [Formula: see text]; and r = 0.643, p = 0.004 for [Formula: see text]. Contrast VA was significantly improved for both fSL and RGP-CL wears and the improvements were significantly correlated between each other for all four contrast levels and two backgrounds. Conclusion: RGP-CL wear induces astigmatism for the eyes with minor astigmatism probably due to a correction of corneal astigmatism and thus a manifesting of the lens astigmatism. For the astigmatic eyes, RGP-CL wear has similar effect on correcting astigmatism as the spectacle lens wear with spherical-cylinder correction and also produces similar visual improvement.