Comparison of Early Postoperative Visual Acuity Between Intracapsular and Supracapsular Phacoemulsification: A Randomized Controlled Clinical Trial

Overview

Cataracts are the leading cause of blindness worldwide, and phacoemulsification combined with intraocular lens implantation has become the most mainstream surgical approach. With advancements in surgical techniques and equipment, this procedure has evolved from a simple vision-restoring surgery into the era of refractive surgery. Patients now have higher expectations for postoperative visual quality, particularly the recovery of early vision, which directly impacts their satisfaction. Intraoperative surgical details have a direct influence on postoperative visual acuity. Thanks to intraoperative optical coherence tomography (iOCT) technology, surgeons have gradually recognized that factors such as surgical incisions and intraoperative anterior chamber collapse can affect the survival of corneal endothelial cells after surgery, which is directly related to early postoperative vision and patient satisfaction. Swept-source intraoperative OCT (SS-iOCT) has further improved imaging range and clarity, helping us discover that the depth of intraoperative ultrasound energy use (such as cumulative dissipated energy) correlates with postoperative corneal endothelial cell loss. This suggests that compared to performing phacoemulsification at the capsular opening plane or in the anterior chamber, intracapsular phacoemulsification may reduce postoperative corneal endothelial cell loss, potentially leading to better early postoperative vision, which is crucial for patient satisfaction. However, evidence is still lacking. Therefore, this study aims to compare the effects of intracapsular versus extracapsular phacoemulsification on early postoperative vision, as well as long-term visual acuity, corneal endothelial cells, corneal changes, and the incidence of intraoperative and postoperative complications.

Interventions

• Procedure Supracapsular Phacoemulsification
  During phacoemulsification, real-time imaging of the anterior segment was performed using SS-iOCT (Tupai, China), but the surgeon was not able to view the images. The surgeon was instructed to proceed with phacoemulsification as per routine, using phaco energy (i.e., level 3). All other surgical steps were identical to conventional surgery.
• Procedure Intracapsular Phacoemulsification
  During phacoemulsification, real-time imaging of the anterior segment was performed using SS-iOCT (Tupai, China). The surgeon was required to confirm under SS-iOCT guidance that the phaco tip was located within the capsular bag (as judged by two observers not involved in the surgery) before applying phaco energy (i.e., level 3). All other surgical steps were identical to conventional surgery.

Primary outcome measures

• The best-corrected distance visual acuity at 1 day postoperatively. [Time frame: 1 day postoperatively]

Secondary outcome measures (6)

• Coefficient of variation of corneal endothelial cell size [Time frame: Post-operative day 1, week 1, month 1, month 3, month 6]
• The percentage loss of central corneal endothelial cell density compared to the preoperative baseline at post-operative day 1 and post-operative [Time frame: 1 day and 1 month postoperatively]
• Percentage of hexagonal cells [Time frame: Post-operative day 1, week 1, month 1, month 3, month 6]
• Central corneal thickness [Time frame: Post-operative day 1, week 1, month 1, month 3, month 6]
• Corneal endothelial cell density [Time frame: Post-operative day 1, week 1, month 1, month 3, month 6]
• The best-corrected distance visual acuity at other time frame [Time frame: Post-operative week 1, month 1, month 3, month 6]

Eligibility criteria

Inclusion criteria

• Age ≥ 50 years and ≤ 90 years
• Able to cooperate with preoperative examinations
• At least one eye meets the study eye criteria
• Has the capacity and willingness to provide informed consent
• Age-related cataract
• Nuclear opacity (N) graded ≥4 according to the Lens Opacities Classification System III (LOCS III)
• Scheduled for phacoemulsification with intraocular lens implantation
• Pupil size ≥6 mm after dilation
• Corneal endothelial cell density ≥1500 cells/mm²

Exclusion criteria

• Considered unsuitable by the investigator for participation in this clinical trial for other reasons (e.g., unstable systemic condition, uncontrolled blood pressure/blood glucose, severe cardiovascular disease, renal disease, etc.)
• Blood pressure > 180/110 mmHg (systolic >180 mmHg or diastolic >110 mmHg). Patients may be considered for inclusion if blood pressure can be controlled below these thresholds with medication.
• History of myocardial infarction or other cardiac disease requiring hospitalization, cerebral infarction, transient ischemic attack, or acute heart failure within 4 months prior to enrollment.
• Women with childbearing potential (i.e., currently pregnant, breastfeeding, or planning to become pregnant within the next 2 years). Women of childbearing potential should be asked about the possibility of pregnancy, and the investigator will determine when a pregnancy test is necessary.
• Currently participating in another clinical trial
• History of ocular trauma or surgery
• Presence of other ocular diseases (e.g., glaucoma, diabetic retinopathy)
• Other ocular factors that may complicate surgery (e.g., small pupil, shallow anterior chamber)

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation

Randomized

Model

Parallel assignment

Masking

Double blind

Primary purpose

Treatment

Study locations

China · 1 center

• Zhongshan Ophthalmic Center, Sun Yat-sen University — Guangzhou

Identifiers

NCT: NCT07407049 · 2025KYPJ174

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗