The proportion of eyes achieving postoperative spherical equivalent SE within ±0.5 D and ±1.0 D of intended refraction is a core quality metric for biometry and refractive services. Our baseline audit for 01/09/2022–30/08/2023 using contact applanation A-scan and manufacturer A-constants reported 79.1% within ±1.0 D and MAE 0.65 D. To address systematic bias and measurement variability we implemented a pragmatic quality improvement cycle consisting of calculation and prospective application of locally optimised A-constants derived from baseline outcomes and adoption of immersion A-scan biometry to improve axial length measurement accuracy. This subsequent audit reports refractive outcomes for 01/09/2023–31/08/2024 and compares them with the prior year.

Study design and setting Retrospective consecutive case series of routine phacoemulsification operations performed at Narinder Mohan Hospital Mohan Nagar Ghaziabad between 1 September 2023 and 31 August 2024. Data extraction and analysis were performed in September 2024. Participants and eligibility Consecutive eyes of patients aged 40 years or older undergoing uncomplicated small-incision phacoemulsification with in-the-bag foldable acrylic IOL implantation who attended for six-week postoperative subjective manifest refraction and achieved corrected distance visual acuity of 6/12 or better were included. Exclusion criteria matched the baseline audit and included preoperative corneal or retinal pathology expected to affect refraction intraoperative complications combined procedures and loss to follow-up before six weeks. Interventions between audits • A-constant optimisation From the baseline audit dataset a mean signed prediction error was calculated and a scalar correction applied prospectively to manufacturer A-constants for all IOL models during the subsequent year. • Adoption of immersion A-scan biometry All axial length measurements were performed using immersion A-scan technique to minimise corneal compression and improve repeatability. A standard operating procedure SOP for immersion measurement was introduced. • Operator training and standardisation Biometry operators received refresher training emphasising probe alignment immersion technique repeatability criteria and keratometry recording. • Prospective data capture Axial length keratometry IOL model A-constant used and six-week manifest refraction were recorded in the departmental biometry register. Biometry IOL calculation and surgery Preoperative axial length measured exclusively by immersion A-scan Sonomed or equivalent; keratometry and anterior chamber depth recorded per routine. IOL power calculations used the Regression 2 formula with locally optimised A-constants. Routine small-incision phacoemulsification was performed under topical or local anaesthesia with in-the-bag implantation of foldable acrylic IOLs. Principal IOL models implanted were Biotech EyeAcryl ASHFY 600 Biotech Genesis and Bausch & Lomb Envista. Surgical technique postoperative regimen and follow-up schedule were consistent with the baseline period. Outcome measures and statistical analysis Primary outcome proportion of eyes with postoperative SE within ±1.0 D of predicted refraction at six weeks. Secondary outcomes proportion within ±0.5 D MAE SD and 95% CIs. Proportions presented with 95% CIs computed by standard normal approximation SE = (\sqrt{p(1-p)/n}) 95% CI = (p \pm 1.96\cdot SE). MAE reported with SD and 95% CI 95% CI for mean = mean ± (1.96\cdot SD/\sqrt{n}). Subgroup descriptive analyses by axial length categories and IOL model were performed where numbers permitted. No formal hypothesis testing was prespecified. Audit governance Conducted as a clinical audit under local institutional governance at Narinder Mohan Hospital. Anonymised data retained per institutional policy.

Sample and baseline characteristics A total of 147 eyes met inclusion criteria. Baseline demographics and ocular parameters are summarised in Table 1. Table 1 Baseline demographics and ocular parameters n = 147 Variable Value Age mean ± SD 67.9 ± 9.2 years Gender Male Female 82 56% 65 44% Laterality Right Left 77 52% 70 48% Axial length mean ± SD 23.48 ± 1.11 mm Anterior chamber depth mean ± SD 3.13 ± 0.44 mm Average keratometry mean ± SD 43.22 ± 1.72 D Refractive outcomes after A-constant optimisation and immersion A-scan Table 2 Refractive outcome summary n = 147 Outcome Value Within ±1.0 D n 129 147 87.76% 95% CI 82.6–92.9 Within ±0.5 D n 96 147 65.31% 95% CI 57.7–72.9 MAE mean ± SD 0.44 ± 0.21 D 95% CI 0.40–0.48 Mean signed error mean ± SD −0.02 ± 0.28 D 95% CI −0.06–0.02 The mean signed error after applying the scalar correction was effectively neutralised indicating elimination of prior systematic bias. Subgroup descriptive findings • Axial length strata Performance was consistent across axial length categories: <22.0 mm n = 18 within ±1.0 D 15 83.3% 22.0–24.5 mm n = 102 within ±1.0 D 90 88.2% >24.5 mm n = 27 within ±1.0 D 24 88.9%. IOL models No clinically important differences were observed between the three principal IOL models implanted see Table 3 supplementary.

Key findings When immersion A-scan biometry replaced contact applanation A-scan and locally optimised A-constants were applied prospectively refractive precision improved to 87.8% within ±1.0 D and MAE decreased to 0.44 D. These results exceed the institutional benchmark of ≥85% within ±1.0 D and represent a meaningful improvement from the baseline audit which reported 79.1% within ±1.0 D and MAE 0.65 D. Interpretation and mechanisms The principal mechanism for improvement was elimination of systematic prediction error by applying a locally derived scalar correction to manufacturer A-constants. Adoption of immersion A-scan reduced corneal compression artefact and improved axial length repeatability compared with contact applanation measurements. Operator training and SOP adherence likely reduced measurement variability contributing to the reduction in MAE. Practical implications • Apply locally optimised A-constants for routine IOL calculations and document the A-constant used for each case to enable ongoing monitoring. • Maintain immersion A-scan technique and operator training to preserve measurement quality. • Continue prospective outcome collection and perform annual re-audit to detect drift and update A-constants as needed. • When resources permit consider future acquisition of optical biometry to further reduce random error and enable use of contemporary formulae though meaningful improvement is achievable without it. Strengths and limitations Strengths include consecutive case inclusion prespecified outcomes and direct before after comparison within the same service. Limitations include single-centre retrospective design modest sample size and absence of optical biometry which limits direct comparison with benchmarks derived from optical devices. The audit was not powered for formal statistical testing of subgroup differences.

A low-cost pragmatic quality improvement cycle combining immersion A-scan biometry locally optimised A-constants and operator standardisation improved refractive outcomes after routine phacoemulsification to 87.8% within ±1.0 D and reduced MAE to 0.44 D without use of optical biometry. Continued prospective outcome monitoring and annual re-audit are recommended to sustain and refine these gains. Tables supplementary Table 3 IOL model distribution and within ±1.0 D proportions one-line cells IOL model Cases n Within ±1.0 D n Biotech EyeAcryl ASHFY 600 62 55 Biotech Genesis 48 43 Bausch and Lomb Envista 37 31 Figure Figure 1 Histogram of achieved minus predicted spherical equivalent SE at six weeks bin width 0.25 D with overlaid cumulative distribution curve showing proportions within ±0.25 D ±0.5 D and ±1.0 D.

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