April 2019


Progressive improvements in NHS refractive outcomes over 15 years

by Stefanie Petrou Binder, MD EyeWorld Contributing Writer

A new report describes encouraging trends in achieving predicted refractive outcomes in public cataract surgery in the U.K., with improvements that are having a real-world effect on patient outcomes. While the current National Health Service (NHS) benchmarks that were established in 20091 stipulate that 85% of patients should be within ±1.0 D and 55% should be within ±0.5 D of their predicted refractive outcome, significantly improved results seen in this study suggest it may be time to revise the national targets.
“We should propose that 90% are within ±1.0 D and 65% within ±0.5 D as our new guideline,” said Kieren Darcy, FRCOphth, in a presentation at the 36th Congress of the European Society of Cataract and Refractive Surgeons. “There have been significant changes in the delivery of ophthalmic care over recent years, with improvements across the board in: biometry equipment, staff training, IOL design and models, formulae, and A-constants. But there’s been a lack of direct comparative data, particularly in public healthcare systems in the U.K. Our record system allows us to do a longitudinal assessment of the refractive performance across healthcare services.”

Retrospective study of two hospital databases over 15 years

The retrospective deidentified report incorporates all cataract patient outcome data from the electronic surgical database of Bristol Eye Hospital and Cheltenham General Hospital between 2003 and 2017, excluding complicated surgeries and those with corrected visual outcomes below 6/12. The data was analyzed in 5-year periods and statistical analysis between the groups was performed. The study included 51,534 cases (60.1% of the database’s total surgical events) for analysis.
In terms of the spherical equivalent, a refractive accuracy of 61.9% within ±0.5 D was noted in patients across the entire study period, and 89.3% were within ±1 D. The mean absolute predictive error (MAE) was 0.498 D (SD: 0.502).
The refractive cylinder by itself, across more than 51,000 eyes, was within ±0.5 D in 32.9% of patients and within ±1 D in 61.8% of patients. “That left 38.2% of patients with greater than 1 D refractive cylinder remaining, 19.4% with more than 1.5 D remaining, and 10% with a relatively disabling, greater than 2 D refractive cylinder, and that’s just representative of practices in the U.K.,” Dr. Darcy said.

Change in SE outcomes over time

“This is the most promising part of the analysis. Over the study’s time period, when you look at the time frame in 5-year blocks, there has been a statistical improvement in refractive outcome,” Dr. Darcy said. “If we look at ±1 in 5-year blocks, 2003–2007, 2008–2012, and 2013–2017, the percentage of eyes that were within 1 D of their planned refraction was 85.8% at the start to 92.7% by 2017. Then if we look at eyes achieving ±0.5 D, the same trend is seen, with an improvement from 55.3% of patients being ±0.5 to 68.8% of patients ±0.5. And there is a significant number of eyes in this dataset.”
While the current report gives an encouraging picture of the improvements in service delivery and in predictive postoperative refractive outcomes from the past 15 years, there are, nonetheless, areas that merit some concern. “To date, we think this is the largest reported series of refractive outcomes from cataract surgery in the United Kingdom. But the study has highlighted areas that need improvement as well,” Dr. Darcy said. “Only 85% of patients had their postoperative visual acuity recorded and only 57% of these were refracted. There are many potential explanations for this. Looking back through the reasons we found for the incomplete datasets were patients not attending routine follow-ups and the reliance on other hospitals and external optometrists to collect data, the requirement to physically post data or send it with the patient, or the entrance of collected data into the hospital electronic record, for instance, but much of this has now been changed and improved.
“What we can say, as seen in this dataset over the study period, is that our data recording has improved over the last 15 years, and in particular over the last 5 years, thanks to the digitalization of all of our data recording,” he said.
Despite limitations pertaining to the disadvantages associated with retrospective studies that lack randomization, incomplete refractive data, incomplete recording of toric data limiting the interpretation of refractive cylinder outcomes, and a multitude of IOL variations over the years, this report described positive trends in the accuracy of obtaining predicted postoperative refraction in public cataract surgery in the U.K.
According to Dr. Darcy, “This report shows that perceived improvement in service delivery are in fact true and they represent real-world improvements. We suggest that the current NHS benchmarks established in 2009 that stipulate that 85% of patients should be within ±1 D and 55% of patients should be within ±0.5 D should now be increased to 90% and 65%, respectively. The last concern is about toric IOLs. There is obviously public health and rationing to consider here, but in the patients in particular who have been left with greater than 2 D of refractive cylinder, there is a strong argument that we should be dealing with that as 2 D of cylinder is potentially disabling,” Dr. Darcy said.

About the doctor
Kieren Darcy, FRCOphth
Head of corneal and refractive surgery
Bristol Eye Hospital
Bristol, U.K.

1. Gale RP, et al. Benchmark standards for refractive outcomes after NHS cataract surgery. Eye (Lond). 2009;23:149–52.

Financial interests
: None

Contact information
: kierendarcy@me.com

More information from the study

• Total surgical events included: 108,854
•Percentage with visual acuity data: 85.6%
• Percentage with postop refraction recorded: 57.8%
• Number of uncomplicated surgeries achieving 6/12 or better: 85,784
• Percentage of patients achieving 6/6 CDVA: 50%
• Percentage of patients achieving 6/6 UDVA: 27.4%

Progressive improvements in NHS refractive outcomes over 15 years Progressive improvements in NHS refractive outcomes over 15 years
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