To achieve the desired refraction after cataract surgery, the required power of the IOL implant can be calculated from optical biometry measurements.¹ These measurements primarily include axial length, corneal refractive power (keratometry) and media type,¹ but current biometry devices can also measure anterior chamber depth; white-to-white distance; thickness of the central cornea, retina and lens; and pupil diameter, among others.² Wavefront aberrometry is an objective method of measuring refractive power, based on the way a light beam moves through the eye.³ It can be used in the diagnosis of both higher-order errors, such as complex visual defects that can cause halos, ghost images and other visual symptoms, as well as lower-order errors, such as nearsightedness, farsightedness and astigmatism, which conventional methods of eye examination are unable to detect.³

Abbreviation

IOL, intraocular lens.

References

1. Shahzad HSF. 2024. Available at: https://eyewiki.org/Biometry_for_Intra-Ocular_Lens_(IOL)_Power_Calculation (accessed 12 November 2024).
2. Pathak M, et al. Clin Ophthalmol. 2024;18:1191–206.
3. Vessel M. 2019. Available at: www.allaboutvision.com/eye-exam/wavefront.htm (accessed 7 November 2024).

Cataract surgery in patients with AMD can improve visual function and quality of life across all severity grades of AMD, at least in the short-term.^1,2 The same principles of IOL measurement used for patients undergoing routine cataract surgery apply to those with retinal pathology.³ However, certain ocular conditions, such as macular degeneration, strabismus and opaque media, can cause poor fixation,⁴ and one disadvantage of optical biometry, compared with ultrasound biometry, is that measurements are not possible in patients who are unable to fixate eyes.⁵

Abbreviations

AMD, age-related macular degeneration; IOL, intraocular lens.

References

1. Miller KM, et al. Ophthalmology. 2022;129:P1–126.
2. ESCRS. 2024. Available at: www.escrs.org/escrs-guideline-for-cataract-surgery/ (accessed 13 November 2024).
3. Weng CY, Weikert MP. CSRT. 2020. Available at: https://crstoday.com/articles/2020-nov-dec/iol-selection-for-retina-patients (accessed 13 November 2024).
4. Chen SH, Luo ZK. eye Insights 16. Available at: https://eye.hms.harvard.edu/book/preoperative-preparation-optical-biometry (accessed 13 November 2024).
5. Pathak M, et al. Clin Ophthalmol. 2024;18:1191–206.

Even new-generation IOL power calculators, with effective lens position determination and increased input parameters, remain limited because the parameters are fixed in terms of quantity and type.sup>1Modern formulas that leverage machine learning (AI formulas) are theoretically more accurate because they are created using large datasets that take into account multiple variables, they use advanced machine learning algorithms for creating predictive models, and can be cloud-based and updated in perpetuity as postoperative refractive data become available.¹This continuous improvement allows AI-based calculators to evolve dynamically over time.^1,2

Abbreviations

AI, artificial intelligence; IOL, intraocular lens.

References

1. de Rojas J, Ladas J. CRST. June 2023. Available at: https://crstoday.com/articles/june-2023/ai-models-for-iol-calculation(accessed 12 November 2024).
2. Siddiqui AA, Ladas JG. Ophthalmol Manag. April 2019. Available at: https://ophthalmologymanagement.com/issues/2018/april/using-ai-in-iol-calculations/ (accessed 14 November 2024).

Data for the TECNIS Odyssey IOL were presented at ASCRS 2024.^1,2An ambispective clinical trial showed that, in the four bilaterally implanted patients with 1- and 3-month postoperative data, mean manifest refraction spherical equivalent was 0.12 D with mean binocular logMAR (Snellen) uncorrected distant VA of -0.12 (20/15), mean distance corrected intermediate VA at 66 cm was 0.08 (20/24) and depth of focus was 0.18 (20/30) or better between +0.5 D to -3.0 D; three patients demonstrated complete spectacle independence.¹ In a real-world study of 96 patients bilaterally implanted with the TECNIS Odyssey IOL, mean binocular logMAR (Snellen) uncorrected distant VA was 0.01 (20/20), best corrected distance VA was -0.03 (20/20), and uncorrected near VA at 40 cm was 0.10 (J1 equivalent).² No subjects reported experiencing starbursts, 85% of patients reported no or mild halo, and 89% reported no or mild night glare; 96.4% (80/83) did not require spectacle correction for distance, intermediate or near vision at the 1-month visit.²

Abbreviations

ASCRS, American Society of Cataract and Refractive Surgery; IOL, intraocular lens; logMAR, logarithm of the minimum angle of resolution; VA, visual acuity.

References

1. Waring GO, et al. Presented at: ASCRS, Boston, MA, USA. 5–8 April 2024. Abstr 50686.
2. Mathews PM, et al. Presented at: ASCRS, Boston, MA, USA. 5–8 April 2024. Abstr 50685.

Patients with a history of laser refractive surgery have an altered anterior and posterior corneal surface relationship, which can make preoperative biometry, IOL calculations and postoperative refractive error challenging, mainly through altered predictability of effective lens position following cataract surgery. The light adjustable lens is designed such that the power can be adjusted to correct both residual spherical and cylindrical refractive errors postoperatively through a noninvasive procedure using a spatially profiled ultraviolet light beam in the weeks following IOL implantation and refractive stabilization. Given that the light adjustable lens can be fine-tuned to neutralize refractive error following cataract surgery, it provides a refractive advantage in the post-refractive surgery patient population by mitigating the effects of refractive surprise.

Abbreviation

IOL, intraocular lens.

Reference

Wong JR, et al. Clin Ophthalmol. 2023;17:3379–87.