A recent study published in Scientific Reports evaluated changes in the demographic and ocular biometric characteristics of cataract patients over the past decade to identify trends that may impact cataract surgery and design / selection of intraocular lenses (IOLs).
Give me some background.
As the leading cause of blindness, cataracts are a major public health concern worldwide—particularly because the number of individuals with cataracts is expected to rise as the global population ages.
- In tandem: The incidence of myopia and refractive surgeries to correct it are also increasing.
Meaning: A growing proportion of individuals undergoing cataract surgery have a history of high myopia and refractive surgery.
- And: Refractive surgery can alter ocular morphology, requiring changes in power calculations for selecting an IOL.
Any previous studies on this?
The same research team of this clinical study performed a similar study in a cohort of patients aged 50+ who underwent cataract surgery at the same institution (listed below) between November 2011 and August 2014.
- Note: This initial study was the first hospital-based population study of ocular biometric characteristics of cataract patients aged 50+ from western China.
The key finding: A high prevalence of severe axial myopia (13.66% of patients with axial length [AL] > 26.5 mm), which the authors noted required further investigation.
Now, talk about this new research.
In this retrospective study, investigators analyzed clinicodemographic and ocular biometric data from swept-source optical coherence tomography (SS-OCT) for 25,192 eyes of 25,192 patients aged 40+ who underwent cataract surgery.
When and where: Between 2020 and 2023 at West China Hospital of Sichuan University in Chengdu, China.
Findings?
As patient age increased, the following characteristics tended to decrease:
- AL
- Anterior chamber depth (ACD)
- Aqueous depth (AQD)
- White-to-white (WTW)
Conversely: With age, corneal refractive power and lens thickness tended to increase.
In addition: Investigators reported trends in eyes that had undergone refractive surgery, such as:
- Deeper ACD
- Deeper AQD
- Thinner lenses
- Longer WTW
Tell me more.
In the study sample, 19.66% of patients had axial lengths > 26 mm and 1.72% had a history of refractive surgery—with the incidence of refractive surgery increasing significantly from 2020 to 2023 (1.31% to 1.99%, respectively).
For patients who had undergone refractive surgery, most underwent laser-assisted in situ keratomileusis (LASIK, 46.23%) or photorefractive keratectomy (PRK, 31.60%).
Compared to patients without a history of refractive surgery, those with such a history were on average 12 years younger.
- Further: A larger proportion of individuals had axial lengths > 26 mm or corneal refractive power below 38 diopters (D).
Expert opinion?
“Our analysis of anterior / posterior (A / P) ratio in this cohort was consistent with the fact that PRK and LASIK increase the curvature radio of the anterior corneal surface much more than the curvature radius of the posterior surface,” the study authors explained.
Meaning: Clinicians must take into account these effects of previous refractive surgery because they may render IOL calculations inaccurate.
Limitations?
These included:
- The patient population came from a large geographic area in southwest China, which may not be entirely representative of populations elsewhere in China or in the world
- The age inclusion criteria differed between the cohorts of the two studies led by this research team (≥ 40 years in the 2020s cohort vs. ≥ 50 years in the 2010s cohort), so comparisons should be performed and interpreted with caution
Tie it all together for me.
These findings suggest that the frequencies of high myopia and of previous refractive surgery among cataract patients increased between the 2010s and the 2020s.
- At the same time: The age of cataract patients at the time of surgery decreased during this time period.
The study authors noted that these changes in ocular and demographic characteristics may require updates in:
- Preparations prior to cataract surgery
- Procedures during surgery
- Management after surgery
- Design and selection of IOLs