Impact of Ocular Residual Astigmatism On Anterior Corneal Astigmatism In Children With Low And Moderate Myopia

Background: To assess the influence of ocular residual astigmatism to anterior corneal astigmatism in children with low and moderate myopia.Methods: Refractive astigmatism was obtained by subjective manifest refraction. Anterior corneal astigmatism was obtained by IOL Master. Using Thibos vector analysis to calculate ocular residual astigmatism. Correlation analysis was used to assess the relationship between the magnitude of ocular residual astigmatism and anterior corneal astigmatism. The influence of ocular residual astigmatism to anterior corneal astigmatism was evaluated by Physical method.Results: The study analyzed 241 right eyes of 241 children aged 8 to 18 years old. In this study, the median magnitude of ocular residual astigmatism was 1.02 D, with interquartile range was 0.58 D. Against-the-rule ocular residual astigmatism was seen in 232 eyes (96.3%). There was a significant and moderate correlation between ocular residual astigmatism and anterior corneal astigmatism (r = 0.50, P < 0.001). The ocular residual astigmatism in 240 eyes (99.6%) had a compensatory effects on anterior corneal astigmatism. The mean compensation value was 1.00 ± 0.41 D (rang 0.02 D to 2.34 D). Based on this effect, 37 eyes had different axial classification of anterior corneal astigmatism and refractive astigmatism. By contrast, one eye (0.4%) had oblique ocular residual astigmatism and superimposed with-the-rule anterior corneal astigmatism.Conclusions: The magnitude of ocular residual astigmatism was relatively huge in myopia children and predominantly compensated anterior corneal astigmatism. The ocular residual astigmatism should be assessed first before fitting orthokeratology.

Long-term changes in the refractive effect of a toric intraocular lens on astigmatism correction

Purpose To examine the long-term changes in the astigmatism-correcting effect of a toric intraocular lens (IOL) after stabilization of surgically induced astigmatic changes due to cataract surgery. Methods Unilateral eyes of 120 patients that received a toric IOL for against-the-rule (ATR) or with-the-rule (WTR) astigmatism were enrolled. Manifest refractive and anterior corneal astigmatism, and ocular residual astigmatism which is mainly derived from internal optics were examined preoperatively, at approximately 2 months postoperatively (baseline) and at 5 ~ 10 years postbaseline. The astigmatism was decomposed to vertical/horizontal (Rx) and oblique components (Ry), which was compared between baseline and 5 ~ 10 years postbaseline. Results In the eyes having ATR astigmatism, the mean Rx and Ry of the manifest refractive and corneal astigmatism significantly changed toward ATR astigmatism between the baseline and 5 ~ 10 years postbaseline (p ≤ 0.0304), but those of ocular residual astigmatism did not change significantly between the 2 time points. In the eyes having WTR astigmatism, the Rx and Ry of refractive, corneal, and ocular residual astigmatism did not change significantly between the 2 time points. Double-angle plots revealed an ATR shift in refractive and corneal astigmatism and no marked change in the ocular residual astigmatism in the eyes with ATR astigmatism, and there is no change in this astigmatism in the eyes with WTR astigmatism. Conclusion The long-term changes with age in the effect of a toric IOL significantly deteriorated due to an ATR shift of corneal astigmatism in the eyes having ATR astigmatism, while it was maintained in eyes having WTR astigmatism, suggesting that ATR astigmatism should be overcorrected.

Femtosecond Laser-Assisted Cataract Surgery After Corneal Refractive Surgery

Cataract is the leading cause of blindness worldwide, and advanced cataract techniques such as femtosecond laser-assisted cataract surgery (FLACS) have been commercially available. Corneal refractive surgery (CRS) is one of the most popular surgeries for the correction of refractive errors. CRS changes the cornea not only anatomically but also pathophysiologically. However, there has been no clinical research analyzing the refractive and safety outcomes of FLACS after CRS. The aim of this study is to evaluate whether FLACS after CRS is more effective and safe than conventional PCS. Participants with a previous CRS history who underwent FLACS or conventional PCS were included in this study. The visual outcomes and the refractive outcomes including refractive, corneal, and ocular residual astigmatism were compared. The safety outcomes were then studied intraoperatively and postoperatively. A total of 102 patients with age-related cataract were enrolled. At 3 months postoperatively, UCVA, BCVA, and predictive error were not significantly different between the FLACS and conventional PCS groups. Reduction of refractive astigmatism was higher in FLACS. Postoperative ORA was significant lower in FLACS. Reduction of ORA was higher in FLACS. The intraoperative and postoperative complications were also not significantly different between the two groups. FLACS was found to be effective in patients with a previous history of CRS in terms of vision and refractive outcomes and was free from adverse effects. The competitive edge of FLACS in postoperative ORA, with the reduction of refractive astigmatism and ORA, may provide better visual quality than conventional PCS.

Changes in ocular astigmatism after superotemporal versus temporal clear corneal incision cataract surgery

Background The incision site to choose to manage postoperative astigmatism during cataract surgery is still debated. This study investigated corneal and internal astigmatism changes after superotemporal versus temporal clear corneal incision cataract surgery. Methods Patients included were diagnosed between December 2019 and January 2020 with age-related cataract with corneal astigmatism < 1.5 diopters (D) and were divided into two groups: Right Eye Group (R Group, superotemporal incision) and Left Eye Group (L Group, temporal incision). Uncorrected visual acuity, manifest refraction, corneal topography, anterior segment optical coherence tomography were performed pre- and 6 months postoperatively. Total ocular astigmatism, corneal astigmatism, surgically induced corneal astigmatism (SICA), non-corneal ocular residual astigmatism (N-CORA), postoperative intraocular lens (IOL) decentration, and tilt were analysed. Results Thirty-eight subjects were included: 21, R Group; 17, L Group. After surgery, the N-CORA decreased significantly from 1.17 ± 0.72D to 0.73 ± 0.47D in all patients (P = 0.001), 1.03 ± 0.52D to 0.70 ± 0.40D in the R Group (P = 0.005), and 1.35 ± 0.90D to 0.78 ± 0.55D in the L Group (P = 0.033). Significant differences between the R and L groups were found in the postoperative meridian of anterior corneal astigmatism (75.95 ± 52.50 vs 116.79 ± 47.29; P = 0.017), total corneal astigmatism (51.65 ± 42.75 vs 95.20 ± 57.32; P = 0.011), J45 change vector of SICA in the anterior cornea (-0.10 ± 0.18 vs 0.00 ± 0.11; P = 0.048), and total cornea surface (-0.14 ± 0.17 vs 0.03 ± 0.12; P = 0.001). IOL decentration, tilt, and the meridian of IOL tilt were not significantly correlated with N-CORA. Conclusions The N-CORA significantly decreased after cataract surgery. Superotemporal and temporal incisions can cause differences in the meridian components of oblique astigmatism but will not have a significant effect on the magnitude of corneal astigmatism.

Contribution of Ocular Residual Astigmatism to Anterior Corneal Astigmatism in Children with Low and Moderate Myopia

To assess the contribution of ocular residual astigmatism (ORA) to anterior corneal astigmatism (ACA) in children with low and moderate myopia. Refractive astigmatism (RA) were received by subjective manifest refraction. ACA were obtained by IOL Master. Using Thibos vector analysis to calculate ORA. Correlation analysis was used to assess the relationship between the magnitude of ORA and ACA. The contribution of ORA to ACA was evaluated by Physical method. The study analyzed 241 right eyes of 241 children aged 8 to 18 years old. In this study, the median magnitude of ORA was 1.02 D, with interquartile range was 0.58 D. Against-the-rule ORA was seen in 232 eyes (96.3%). There was a significant and moderate correlation between ORA and ACA (r = 0.50, P < 0.001). The ORA in 240 eyes (99.6%) had a compensatory effects on ACA. The mean compensation value was 1.00 ± 0.41 D. Based on this effect, 37 eyes had different axial classification of ACA and RA. By contrast, one eye (0.4%) had oblique ORA and superimposed with-the-rule ACA. The magnitude of ORA was relatively huge in myopia children and predominantly compensated ACA. The ORA should be assessed first before fitting orthokeratology.

The contribution of ocular residual astigmatism to anterior corneal astigmatism in refractive astigmatism eyes

To determine the distribution of ocular residual astigmatism (ORA) in astigmatic eyes and the influence on the anterior corneal (ACA) and refractive astigmatism (RA). A total of 165 children met the inclusion criteria. Right eyes’ data were analyzed. Using Thibos vector analysis to calculate ORA. Spearman correlation analysis was used to obtain the correlation between the magnitude of ORA, ACA and RA. The median magnitude of ORA in astigmatic eyes was 0.57 D, with interquartile range was 0.42 D. And they were main against-the-rule (57.6–75.8%) and oblique astigmatism (13.9–34.5%) ORA. The ORA in 140 eyes (84.8%) acted as an offset to ACA, meanwhile, 25 eyes (15.2%) superimposed it. About 98% (97.9–98.4%) against-the-rule and 75% (73.9–82.5%) oblique ORA counteracted ACA, nevertheless, all with-the-rule ORA had a superimposed effect on ACA. For with-the-rule ACA, about 86% (85.4–85.9%) ORA worked to offset it. There was statistically correlations between ORA and ACA (r = 0.17, P = 0.03), ORA and RA (r = − 0.27, P = 0.001). The magnitude of ocular residual astigmatism was relatively small in children’s astigmatic eyes. Both against-the-rule and oblique ORA can counteract with-the-rule ACA.

The Impact of Changes in Corneal Back Surface Astigmatism on the Residual Astigmatic Refractive Error following Routine Uncomplicated Phacoemulsification

Purpose. To determine the significance of any association between intersessional changes in ocular residual astigmatism (RA) and astigmatism at corneal front (FSA) and back (BSA) surfaces following uneventful routine phacoemulsification. Methods. Astigmatism was evaluated by autorefractometry and subjective refraction and at both the corneal surfaces with Orbscan II™ (Bausch & Lomb) over central 3 mm and 5 mm optical zones at 1, 2, and 3 months after routine phacoemulsification in 103 patients implanted with monofocal nontoric intraocular lenses (IOLs, one eye/patient). Data were subjected to vector analysis to determine the actual change (Δ) in astigmatism (power and axis) for the refractive and Orbscan II findings. Results. The number of cases that attended where ΔRA was ≥0.50 DC between 1 and 2 months was 52 by autorefractometry and 36 by subjective refraction and between 2 and 3 months was 24 by autorefractometry and 19 by subjective refraction. Vector analysis revealed significant correlations between ΔFSA and ΔRA for data obtained by autorefractometry but not by subjective refraction. At all times, ΔBSA was greater than ΔFSA (p<0.01). Key findings for ΔBSA values over the central 3 mm zone were between (A) the sine of the axis of ΔRA (y) and sine of the axis of ΔBSA (x) for the data obtained by autorefractometry (between 1 and 2 months, y = 0.749 − 0.303x, r = 0.299, n = 52, p=0.031) and subjective refraction (between 2 and 3 months, y = 0.6614 − 0.4755x, r = 0.474, n = 19, p=0.040) and (B) ΔRA (y) and ΔBSA (x) powers between 2 and 3 months postoperatively for the data obtained by autorefractometry (ΔRA = 0.118 ΔBSA + 0.681 r = 0.467, n = 24, p=0.021) and subjective refraction (ΔRA = 0.072 ΔBSA + 0.545 r = 0.510, n = 19, p=0.026). Conclusion. Changes in the ocular residual refractive astigmatic error after implanting a monofocal nontoric IOL are associated with changes in astigmatism at the back surface of the cornea within the central optical zone.