Benchmark standards for refractive outcomes after NHS cataract surgery

Abstract

Purpose To establish benchmark standards for refractive outcome after cataract surgery in the National Health Service when implementing the 2004 biometry guidelines of the Royal College of Ophthalmologists and customising A constants. Methods Three cycles of prospective data were collected throughout the cataract care pathway on all patients using an electronic medical record system (Medisoft Ophthalmology), between January 2003 and February 2006. The electronic medical record automatically recommends the formula to be used according to the College guidelines and allows A constants to be customised separately for either ultrasound or partial coherence interferometry methods of axial length measurement and for different intraocular lens models. Consultants and trainees performed routine phacoemulsification cataract surgery and new intraocular lens models were introduced during the cycles. Uncomplicated cases with'in-the-bag fixation', achieving 6/12 Snellen acuity or better were included. Community ophthalmic opticians performed refraction at 4 weeks. Results The postoperative subjective refraction was within 1 D of the predicted value in 79.7% of the 952 cases in cycle 1, 83.4% of 2406 cases in cycle 2, and 87.0% of 1448 cases in cycle 3. Conclusions On the basis of our data, using College formula, optimising A constants and partial coherence interferometry, a benchmark standard of 85% of patients achieving a final spherical equivalent within 1 D of the predicted figure and 55% of patients within 0.5 D should be adopted.

Estimation of effective lens position using a method independent of preoperative keratometry readings

“…In our study, the approximate mean and maximum discrepancies in the 41% to 100% of cases were < 1.0 D. [12][13][14][15][16][17][18][19][20][21] In our study, the calculated discrepancies in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 …”

Optimising biometry for best outcomes in cataract surgery

“…11 More recent studies than those available at the time the guidelines were written suggest that this target is easily achievable, and that more than 90% within ± 1 D and 60% within ± 0.5 D would not be unreasonable expectations. 10,16,31 Many departments and surgeons would be very satisfied with such results.…”

“…15 In general, however, immersion ultrasound produces more accurate predictions than contact ultrasound, 8 approaching or matching those of the optical methods. 16,17 If immersion ultrasound was adopted as the second-line investigation for eyes in which optical biometry fails, then outcomes could be improved from 82.5% within ± 1 D of target 10 to between 85.7 and 94.3%. 18,19 The impact of such improvement on the patient population as a whole is dependent upon the proportion requiring ultrasound biometry; assuming a rate of 10% then between 0.3 and 1.2% more eyes overall could achieve within ± 1 D of target as a result of this change in practice.…”

“…29 The process of constant optimisation has little effect on the dispersion of outcomes around the mean (ie, the standard deviation, SD), 29 but maximises the proportion of eyes within a particular target range and minimises the MAE (see Appendix for a discussion of the relationship between ME, MAE, and SD). IOL constant optimisation has been shown to improve substantially prediction accuracy for contact ultrasound (from 79.7 to 82.5% within ± 1 D), 10 immersion ultrasound (from 60% to 65% within ± 0.5 D), 16 and with optical biometry (from 76-89% to 92-94% within ±1 D, dependent upon IOL model and formula). 31 The latter study used constants intended for contact ultrasound as the baseline, 31 and in practice, the magnitude of the improvement to be gained from IOL constant optimisation depends on how close the optimised and baseline constants are found to be.…”

“…9 Gale et al found that with appropriate formula selection, optical axial length measurement, and optimisation of IOL constants 87% of patients achieved an outcome within ± 1 D of target. 10 The Royal College of Ophthalmologists, in its most recent Cataract Surgery Guidelines, 11 has adopted a standard of 85% within ± 1 D of target and 55% within ± 0.5 D of target.…”