Postoperative Residual Refractive Error Research Articles

Relationship Between Postoperative Residual Refractive Error and Preoperative Corneal Stiffness in Small Incision Lenticule Extraction.

To explore the relationship between postoperative residual refractive error and preoperative corneal stiffness after small incision lenticule extraction (SMILE). Hospital clinic. Retrospective cohort study. Corneal stiffness was evaluated using the stress-strain index (SSI). Associations between postoperative spherical equivalent (SE) and corneal stiffness were determined using longitudinal regression analysis after adjustment for sex, age, preoperative SE, and other variables. The cohort was divided into halves to compare risk ratios for residual refraction in corneas with different SSI values. Low SSI values were defined as having "less-stiff corneas" and others as having "stiffer corneas." 287 patients (287 eyes) were included. Greater undercorrection was found in less-stiff corneas across all follow-up time points (less-stiff corneas: 1 day: -0.36±0.45 D, 1 month: -0.22±0.36 D, 3 months: -0.13±0.15 D; stiffer corneas: -0.22±0.37 D, -0.14±0.35 D, -0.05±0.11 D, respectively). Postoperative refraction exhibited an average 0.05-D undercorrection for every 0.1-unit decrease in SSI after adjustment for variables. SSI accounted for nearly 10% of the variance in retractive outcomes. Less-stiff corneas increased the risk ratio of postoperative absolute SE >0 D and ≥0.25 D by 2.242 (95% confidence interval [CI]: 1.334, 3.768) and 3.023 (95% CI: 1.466, 6.233), respectively, compared to stiffer corneas. Postoperative residual refractive error was associated with preoperative corneal stiffness. Patients with less-stiff corneas had a 2-3-fold increased risk of residual refractive error post-SMILE. Preoperative analysis of corneal stiffness can help modify nomogram algorithms of surgery and improve the predictability of refractive outcomes.

Impact of Global Optimization of Lens Constants on Absolute Prediction Error for Final IOL Power Selection When Using Intraoperative Aberrometry.

PurposeTo evaluate absolute prediction errors following phacoemulsification with implantation of a multifocal toric intraocular lens (IOL) using intraoperative aberrometry for IOL power selection and to compare findings with the globally optimized and manufacturer’s recommended lens constants and regression coefficients.MethodsData from the Optiwave Refractive Analysis (ORA SYSTEM) were analyzed retrospectively. Absolute prediction errors from surgeries performed before and after the first optimization of the manufacturer’s recommended lens constant and non-optimized regression coefficients for the multifocal toric IOL (SND1T3-6) were compared. Optimization was based on outcomes of procedures performed using the ORA SYSTEM and archived in its database (AnalyzOR). Outcome measures included the proportion of eyes with absolute ORA SYSTEM prediction errors ≤0.25 D and ≤0.5 D and the mean and median absolute prediction errors.ResultsThe pre-optimization group included 1027 eyes operated on by 184 surgeons, and the optimized group included 419 eyes operated on by 143 surgeons. The proportions of eyes achieving absolute ORA SYSTEM prediction errors ≤0.25 D (52.5% vs 35.0%, p < 0.0001) and ≤0.50 D (83.1% vs 66.2%, p < 0.0001) were significantly higher in the optimized than in the pre-optimization group. The mean ± standard deviation (0.30 ± 0.25 D vs 0.43 ± 0.32 D, p < 0.0001) and median (0.24 D vs 0.36 D, p < 0.0001) absolute ORA SYSTEM prediction errors were significantly lower after than before optimization. Prediction errors following optimization were reduced more in eyes of average than of long and short axial lengths.ConclusionGlobal optimization of the manufacturer’s IOL lens constants and regression coefficients resulted in lower absolute prediction errors when compared with the initial manufacturer labeled lens constants and non-optimized regression coefficients. Reductions in absolute prediction error can result in lower postoperative residual refractive error, which can improve post-operative uncorrected visual acuity and provide the potential for greater patient satisfaction following cataract surgery.

Partial Coherence Laser Interferometry Versus Conventional A-Scan Acoustic Biometry in Intraocular Lens Power Calculation – Comparison of Postoperative Refractive Error

Purpose: To compare the post-operative residual refractive error in patients undergoing cataract surgery using partial coherence laser interferometry (PCLI) versus A-scan Applanation acoustic biometry. Study Design: Quantitative experimental research. Place and Duration of Study: Shifa International Hospital (SIH), Islamabad from November 2018 to August 2019. Methods: Total 254 patients were selected. Group A included patients whose biometry was done using PCLI method and group B included patients who had A-Scan acoustic biometry. Intraocular lens power calculation was done using SRK/T formula. Phacoemulsification surgery with foldable Intraocular lens was performed. Patients were called for follow-up visit the next day and then one month after surgery. Postoperative refractive error was checked after one month. All data were entered and analyzed using SPSS version 21.0. Descriptive statistics were used for qualitative as well as quantitative variables. We applied independent samples t-test to compare the mean postoperative refractive error in both groups. A p-value of less than 0.05 was considered significant. Results: The mean age of patients was 65 ± 9.37 years. The preoperative mean axial length was 20.35 ± 1.1 mm in the PCLI group and 21.54 ± 1.2 mm in the ultrasound group. Mean Absolute Error (MAE) of postoperative residual refractive error in the PCLI group was 0.12 ± 0.13 mm (P = 0.003). The MAE in the ultrasound group was 0.18 ± 0.12 mm (P = 0.02). Conclusion: The non-contact optical biometry improves the mean absolute error for postoperative refraction and is a reliable tool for biometry in phakic eyes before surgery. Key Words: Partial coherence laser interferometry; Ultrasound A scan; Biometry; A-constant; Intraocular lens.

Comparison of ocular biometry and refractive outcome between ANTERION and IOL Master 700.

Purpose:To assess the comparability of ocular biometry measurements and refractive outcomes between ANTERION and IOL Master 700.Methods:This comparative prospective study was conducted from December 2020 to February 2021. A total of 225 patients who had cataracts were enrolled for the study and different parameters such as anterior keratometry (Steep K, Flat K) with axis, Sim K, central corneal thickness (CCT), aqueous depth (AQD), lens thickness (LT), and axial length (AL), white-to-white (WTW) were evaluated in IOL master 700 first and then with ANTERION. Finally, 203 patients completed the 6-week follow-up and the postoperative refraction was done at the 6th week. To assess the agreement between the devices, intraclass coefficient (ICC) and Bland–Altman analysis with 95% limits of agreement (LoA) were used. To analyze the agreement for postoperative residual refractive error between the two devices, Kappa statistics were used.Results:The mean difference for steep K, flat K, and Sim K between ANTERION and IOL Master 700 were − 0.18 +/−0.26 D, −0.13+/− 0.28D, −0.15 +/−0.23, respectively. The CCT, ACD, and LT also showed excellent agreement (ICC > 0.9) but the similarity for the keratometry axis was not up to the mark (ICC = 0.794). For postoperative refractive outcomes, the Kappa value was 0.437, indicating moderate agreement.Conclusion:ANTERION showed a good agreement for the majority of parameters with IOLMaster 700 in measuring ocular biometry, except for the keratometry. The accuracy of the intraocular lens power calculations was clinically acceptable with both biometers though the IOL power given by ANTERION remained slightly on the hypermetropic side.

Extended depth-of-focus toric intraocular lens targeted for binocular emmetropia or slight myopia in the nondominant eye: Visual and refractive clinical outcomes

To compare the visual and refractive outcomes with a diffractive toric extended depth-of-focus (EDOF) intraocular lens (IOL) when both eyes are targeted for emmetropia and the nondominant eye is targeted for slight myopia. Three clinical practices, United States. Prospective case series. Patients having routine cataract surgery with bilateral Tecnis Symfony toric EDOF IOL implantation were assigned to 1 of 2 groups. In 1 group, the nondominant eye was targeted for -0.50 diopter (D) (mini-monovision). Assessments included uncorrected monocular and binocular visual acuities (logarithm of the minimum angle of resolution) at distance (4m), intermediate (66cm), and near (40cm) and the postoperative residual refractive error. Forty patients were enrolled in each group, with 1 dropout. The mean postoperative residual refractive astigmatism was 0.25 D in both groups, with no statistically significant difference. The mean residual refractive astigmatism was 0.50 D or lower in 92% of eyes (72/78) in the mini-monovision group and 95% of eyes (74/78) in the emmetropia group 3months postoperatively. The mini-monovision group had slightly worse uncorrected visual acuity at 4m than the emmetropia group (0.16 versus 0.09; P=.002) but better uncorrected acuity at 40cm (0.25 versus 0.34; P<.001). Binocular uncorrected acuity was not statistically significantly different between groups at 4m (-0.03 versus -0.01; P=.33) or 66cm (0.06 versus 0.04; P=.34) but was statistically significant at 40cm (0.25 versus 0.19; P=.03). The EDOF toric IOL provided functional distance, intermediate, and near vision. A slight monovision approach appears to improve near visual acuity.

Predicting Refractive Outcome of Small Incision Lenticule Extraction for Myopia Using Corneal Properties.

PurposeTo investigate whether preoperative corneal topographic and biomechanical parameters (CTBPs) predict postoperative residual refractive error (RRE).MethodsWe retrospectively included 151 eyes from 151 patients of small-incision lenticule extraction (SMILE) with target RRE of plano and 3-month measurements of refractive error from Tianjin Eye Hospital. Multivariate linear/logistic regressions were performed to associate age, gender, preoperative refractive error, lenticule thickness, and CTBPs with postoperative RRE/the occurrence of myopic RRE ≤ −0.25 diopter (D). Stepwise regression was used for feature selection. Leave-one-cross-validation was used for model evaluation by the area under the receiver operating characteristic curve (AUC).ResultsFrom linear regression, more myopic RRE was associated with higher preoperative myopia, intraocular pressure (IOP), flattest curvature of anterior cornea (AC), and highest concavity deformation (HCD), and was associated with lower anterior elevation, anterior asphericity, steepest curvature of AC, and second applanation velocity. The occurrence of ≤ −0.25 D RRE was associated with higher myopia, IOP, posterior elevation and asphericity, flattest curvature of AC, first applanation velocity and HCD, and was associated with lower first applanation stiffness parameter, central corneal thickness, anterior elevation and asphericity, steepest curvature of AC, and second applanation velocity as well as thinner lenticule thickness. Compared to the baseline model using age, gender, and preoperative refractive error, adding CTBPs significantly (P < 0.001) improved the AUC performance to 0.771 from 0.615.ConclusionsPostoperative outcomes of SMILE can be predicted by individual CTBPs.Translational RelevanceOur findings could be used to customize a refractive nomogram based on individual corneal properties improving outcomes and patient satisfaction.

The analysis of influencing factors associated with night vision disturbances after implantable contact lens implantation

Objective To investigate the influencing factors of night vision disturbances after implantable contact lens implantation. Methods Fifty eyes of 25 patients who underwent implantable contact lens implantation in both eyes were retrospectively reviewed. The incidence and severity of night vision disturbances were evaluated using questionnaires 6 months after surgery. Univariate sample and multiple logistic regression analyses were used to detect influencing factors associated with postoperative night vision disturbances. Potential influencing factors included in the analysis were keratometric value, anterior chamber depth, postoperative residual refractive error, higher-order aberrations, preoperative and postoperative mesopic pupil size, the difference between preoperative and postoperative mesopic pupil size, the difference between mesopic pupil size and implantable contact lens optic zone diameter, corneal transverse diameter, sulcus-to-sulcus diameter, and postoperative implantable contact lens vaulting. The power, size, optic zone diameter, and toridity of the implantable contact lens were also included as variables. Results The incidence of night vision disturbances was 34.00% for halos and 26.00% for glare. Halos were found to be significantly related to: (1)The difference between mesopic pupil size and implantable contact lens optic zone diameter (P=0.013); (2)The corneal transverse diameter (P=0.028); (3)The implantable contact lens optic zone diameter (P=0.030). For glare, toricity of the implantable contact lens was revealed as a significant influencing factor (P=0.047). Conclusion Conclusions Possible influencing factors for night vision disturbances include implantable contact lens optic zone diameter, the difference between mesopic pupil size and implantable contact lens optic zone diameter, and the corneal transverse diameter which can cause halos, and the toricity of the implantable contact lens which can cause glare. Key words: Lens, contact, implantable; Vision, night; Eye, phakic

Patient satisfaction and clinical outcomes with laser refractive surgery performed by surgeons in training

To evaluate the refractive error quality of life (RQL) improvement, patient satisfaction, and clinical results of laser refractive surgery performed by residents or fellows. Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, USA. Case series. This study reviewed the clinical results of consecutive refractive surgery cases performed between March 2010 and February 2012 by ophthalmology residents or fellows. One-year postoperative analysis of the RQL and patient satisfaction in a subgroup of patients was completed using the National Eye Institute Refractive Error Correction Quality of Life-42 instrument (NEI RQL-42), and a comparison with NEI published normative data and post-refractive data was performed. Data were obtained from 138 eyes that had laser in situ keratomileusis and 4 eyes that had photorefractive keratectomy. The 1-year postoperative analysis of the RQL and patient satisfaction was completed in 34 patients. After 6 months postoperatively, the mean uncorrected distance visual acuity was 0.01 logMAR (95% confidence interval [CI], -0.012 to 0.023). The mean postoperative residual refractive error spherical equivalent was -0.20 diopter (D) (95% CI, -0.26 to -0.13). No eye lost corrected distance visual acuity. Equivalent or better satisfaction in the RQL was found in all but 1 of the 13 scale scores of the NEI RQL-42 compared with previously published NEI data. Laser refractive surgery performed by residents and fellows showed high patient satisfaction and an improved RQL 1-year postoperatively. Clinical outcomes validated the safety and efficacy of refractive surgery performed by surgeons in training. No author has a financial or proprietary interest in any material or method mentioned.

Risk Factors Associated With Night Vision Disturbances After Phakic Intraocular Lens Implantation

To investigate the incidence and severity of night vision disturbances after implantable collamer lens surgery and to analyze the risk factors. Retrospective, noncomparative study. Medical charts from 50 eyes of 25 patients who underwent implantable collamer lens implantation were retrospectively reviewed. The incidence and severity of night vision disturbances were evaluated using questionnaires administered 6 months after surgery. Univariate simple and multiple logistic regression analyses were used to detect risk factors associated with postoperative night vision disturbances. Potential risk factors included in the analysis were keratometric value, anterior chamber depth, postoperative residual refractive error, higher-order aberrations, preoperative and postoperative mesopic pupil size, the difference between preoperative and postoperative mesopic pupil size, the difference between mesopic pupil size and implantable collamer lens optic zone diameter, white-to-white diameter, sulcus-to-sulcus diameter, and postoperative implantable collamer lens vaulting. The power, size, optic zone diameter, and toricity of the implantable collamer lens were also included as variables. The incidence of night vision disturbances was 34.0% for halos and 26.0% for glare. Halos were found to be significantly related to the difference between mesopic pupil size and implantable collamer lens optic zone diameter (P = .013), white-to-white diameter of the cornea (P = .028), and implantable collamer lens optic zone diameter (P = .030). For glare, toricity of the implantable collamer lens was revealed as a significant risk factor (P = .047). Although not severe, the incidence of night vision disturbances after implantable collamer lens implantation was not negligible. Possible risk factors for night vision disturbances include implantable collamer lens optic zone diameter, the difference between mesopic pupil size and implantable collamer lens optic zone diameter, and white-to-white diameter of the cornea for causing halos, and the toricity of the implantable collamer lens for causing glare.

Corneal Collagen Cross-Linking Before Ferrara Intrastromal Corneal Ring Implantation for the Treatment of Progressive Keratoconus

To evaluate the safety, efficacy, and stability of sequential corneal collagen cross-linking (CXL) and Ferrara intrastromal corneal ring segment (FR) implantation in selected patients with progressive keratoconus. This prospective study involved 9 eyes with progressive keratoconus and a preoperative cylinder value equal to or greater than 5 diopters (D) diagnosed between June 2007 and October 2008. Preoperative and postoperative (6 months after the CXL procedure and 6 months after the FR implantation) biomicroscopy examinations, distance uncorrected and best-corrected visual acuities, refractive error, and topographic maps were evaluated and compared. Mean uncorrected visual acuity was 1.11 logarithm of the minimal angle of resolution (logMAR) preoperatively and 0.75 logMAR at 6 months after CXL (P = 0.03) and 0.23 logMAR at 6 months after FR implantation (P < 0.001). Mean best-corrected visual acuity was 0.26 logMAR preoperatively and 0.24 logMAR at 6 months after CXL (P = 0.87) and 0.12 logMAR at 6 months after FR (P = 0.05). Statistically significant reductions in the mean spherical equivalent (4.38 D; P < 0.001) and mean maximum (5.58 D; P < 0.001) and minimum (4.17 D; P < 0.001) keratometry values were present at 6 months after FR. FR implantation after CXL is a safe and efficacious treatment option for managing selected patients with progressive keratoconus. Good results in terms of visual acuity, postoperative residual refractive error, and keratometry values were obtained. Longer follow-up would be valuable to confirm the stability of these results.

Toric Iris Claw Lens Implantation for Keratoconic Eyes

Keratoconus and other ectatic disorders can be an unexpected finding in patients seeking refractive surgery. In this group of patients, refractive laser corneal procedures are in many cases contraindicated as they may worsen the disease. Implantation of toric phakic iris claw lenses is a safe and effective treatment in patients with stable keratoconus. Good results in terms of visual acuity, post-operative residual refractive error and patient satisfaction can be achieved.

Artiflex Phakic Intraocular Lens Implantation After Corneal Collagen Cross-linking in Keratoconic Eyes

To evaluate the safety, efficacy, and stability of the Artiflex (Ophtec BV) foldable anterior iris-claw phakic intraocular lens (PIOL) following corneal collagen cross-linking (CXL) in select cases of progressive keratoconus. This prospective, comparative study, conducted between March 2007 and June 2008, involved 11 eyes with progressive keratoconus. Inclusion criteria were progressive keratoconus (Amsler-Krumeich classification grades I and II) with no corneal opacities, corneal thickness >450 μm, endothelial cell count >2500 cells/mm(2), anterior chamber depth >3.2 mm, spherical equivalent refraction >4.50 diopters (D) (with a cylinder component <2.00 D), and no other treatment for keratoconus other than contact lens. Each patient underwent CXL in the keratoconic eye with implantation of the Artiflex IOL 6 months thereafter. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and refraction and topographic profiles were examined at 1, 6, and 12 months after the CXL procedure. All eyes achieved UDVA of 0.3 logMAR or better. Final spherical and cylindrical error ranged from 0 to -1.50 D and 0 to -1.75 D, respectively. No eyes lost lines of preoperative CDVA. Statistically significant reductions in mean maximum (2.14 D, P<.001) and minimum (1.17 D, P=.02) keratometry values were present 12 months after the CXL procedure. No complications were observed. Combined CXL and Artiflex implantation was a safe and effective treatment in this subset of eyes with progressive keratoconus. Good results in terms of visual acuity, postoperative residual refractive error, and keratometry values were identified.

Evaluation of Hoffer Q formula in Short and long axial lengths

Purpose: Evaluation of The accuracy of Hoffer Q formula for intraocular lens (IOL) power calculation in short and long axial lengths of the eye. Methods: 100 eyes divided equally into 2 groups: group I (50 eyes) with axial length more than 24.5 and group II( 50 eyes) with axial length more less than 22. Comparison between both groups was done as regards post operative residual refractive error after IOL implantation using Hoffer Q formula. Results: Insignificant difference between the 2 groups as regard post operative residual refractive error. In short length eyes, the mean postoperative refractive error with Hoffer Q formula was 0.80 +0.33D. In long eyes, the mean postoperative refractive error was 1.23 +0.70D. The results show that the best performing formula was in short eyes (P = 0.012). Conclusion: Insignificant difference as regards postoperative residual refractive error between both groups but Hoffer Q formula best performed in short eyes.

Effects of Laser Plume Evacuation on Laser in situ Keratomileusis Outcomes

To study the effects laser plume evacuation on LASIK outcomes using a surgical vacuum and the Nidek EC-5000 excimer laser. Three-month LASIK postoperative data were evaluated retrospectively for 117 eyes treated with a laser plume evacuator and 82 eyes treated without a laser plume evacuator. All eyes were treated with the same Moria CB microkeratome and the same Nidek-EC 5000 excimer laser using the same nomogram. No statistically significant difference was noted in the frequency of corneal abrasions, flap slippage, or the level of postoperative interface debris. A statistically significant difference (P < .001) was noted in postoperative residual refractive error and uncorrected visual acuity. In the group treated without a plume evacuator, 65% (n = 53) were within +/- 0.50 D of the intended correction, 59% (n = 48) had an uncorrected visual acuity of 20/20 or better, 68% (n = 56) had an uncorrected visual acuity of 20/25 or better, and 90% (n = 73) had an uncorrected visual acuity of 20/40 or better. In the group treated with a plume evacuator, 92% (n = 108) were within +/- 0.50 D of the intended correction, 74% (n = 87) had an uncorrected visual acuity of 20/20 or better, 89% (n = 104) had an uncorrected visual acuity of 20/25 or better, and 96% (n = 112) had an uncorrected visual acuity of 20/40 or better. Laser plume evacuation using surgical tubing and a surgical vacuum improved refractive and uncorrected visual acuity outcomes following LASIK.