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.

Vector Analysis of Anticipated Residual Astigmatism and Actual Residual Astigmatism in Toric IOL Implantation using Callisto-Eye

Purpose: The aim of this study is to investigate the differences of actual residual astigmatism and anticipated residual astigmatism using Alpin’s Vector Analysis from toric IOL implantation using Image Guided System (Callisto EyeTM) and other method. Method: This was a retrospective case series study done in Jakarta Eyte Center. Data was taken consecutively from medical records of Toric IOL implantation from January 2016 to November 2017. Primary data taken were demographic data, anticipated residual astigmatism, refractive examination both subyectively and objectively. Secondary data was analized using Alpin’s Vector Analysis to substract anticipated residual astigmatism from actrual residual astigmatism. Spherical equivalent and axis shifting also taken from refractive ecamination results. Data was divided into subgrup of Toric IOL implantation using Image Guided System and subgrup of Toric IOL implantation using other method. Results: There was a statically significant difference of subjective refraction vector analysis result between subgroups with differnce of 0.312 dioptri (p value 0.004). Objective refraction vector analysis shows no statistically difference between two subgrups (p value 0.286). Spherical equivalent both subjectively and objectively not differ (p value 0.721 and 0,689). Axis shifting from refractive examination also not statistically significant differ between two subgrups (p value 0.432 and 0.358) Conclusion: Difference between actual residual astigmatism from subjective refraction and anticipated residual astigmatism is lower whrn usingCallisto EyeTM.