Capsular Tension Ring With Hydrophilic Versus Hydrophobic Intraocular Lenses

Background and rationale: Phacoemulsification with intraocular lens (IOL) implantation is the standard treatment for age-related cataract. IOL material (hydrophilic versus hydrophobic acrylic) is a recognized determinant of long-term capsular biocompatibility, with hydrophobic acrylic lenses generally associated with lower rates of posterior capsule opacification (PCO) and reduced need for neodymium-doped yttrium aluminum garnet (Nd:YAG) laser capsulotomy compared with hydrophilic acrylic lenses. Capsular tension rings (CTRs) are polymethyl methacrylate devices that stabilize the capsular bag equator and have been proposed to mitigate capsular contraction, lens decentration, and PCO, independent of IOL material. Prior comparative work has generally examined either IOL material effects or CTR effects in isolation, or has compared a composite intervention (hydrophilic IOL plus CTR) against a hydrophobic IOL alone, without a design capable of isolating the CTR's independent contribution.

Objectives: To compare visual, refractive, anatomical (IOL position and posterior capsule opacification), and safety outcomes among three approaches to routine cataract surgery: (1) hydrophilic acrylic IOL implantation combined with a CTR (Group A); (2) hydrophobic acrylic IOL implantation alone (Group B); and (3) hydrophilic acrylic IOL implantation alone, without a CTR (Group C). The inclusion of Group C, using the same hydrophilic IOL model as Group A but without CTR insertion, was designed specifically to allow assessment of the CTR's independent contribution when compared against Group A, in addition to the material-based comparisons of Groups A and C against Group B.

Design: Prospective, randomized, parallel-group, three-arm controlled trial conducted at three tertiary ophthalmology centers in Egypt (Zagazig University Hospital, Benha University Hospital, and Al-Azhar University Hospital). Eligible adults aged 50-80 years with visually significant age-related cataract (LOCS III grade >=3) were randomized 1:1:1 using a computer-generated allocation sequence, with allocation concealment via sealed opaque envelopes opened intraoperatively. Outcome assessors and data analysts were blinded to treatment allocation; operating surgeons were not blinded due to the nature of the intervention.

Interventions: All participants underwent standardized phacoemulsification via a 2.2 mm clear corneal incision with a ~5.5 mm continuous curvilinear capsulorhexis. Group A received a hydrophilic acrylic IOL (Eyecryl, Biotech Healthcare, India) plus a polymethyl methacrylate CTR (Auroring CTR 11, Aurolab, India). Group B received a hydrophobic acrylic IOL (AcrySof IQ, Alcon Laboratories, USA) without a CTR. Group C received the same hydrophilic acrylic IOL as Group A, without CTR insertion.

Outcomes: Primary outcomes were best-corrected visual acuity (logMAR) and manifest spherical equivalent refractive error at 24 months, with longitudinal assessment at 1, 3, 6, 12, 18, and 24 months. Secondary outcomes included posterior capsule opacification grade (slit-lamp retroillumination, graded per Aslam et al.), Nd:YAG capsulotomy rate, IOL centration and tilt (anterior segment optical coherence tomography), and intraoperative and postoperative complications (posterior capsule rupture, zonular dialysis, vitreous loss, iris trauma, cystoid macular edema, intraocular pressure elevation, corneal edema, and endophthalmitis).

Follow-up: Scheduled visits at day 1, week 1, and months 1, 3, 6, 12, 18, and 24 postoperatively, with the 24-month visit representing the final prespecified assessment.

Statistical analysis: Continuous variables were compared across groups using one-way ANOVA or Kruskal-Wallis testing as appropriate, with post-hoc pairwise comparisons for Group A vs. Group B and Group C vs. Group B. Categorical variables were compared using chi-square or Fisher's exact test. Repeated-measures ANOVA assessed longitudinal group x time interactions for visual and refractive outcomes.

Inclusion criteria

• Age 50-80 years
• Visually significant age-related cataract, defined as nuclear opacity grade >=3 according to the Lens Opacities Classification System III (LOCS III), graded preoperatively under standardized mydriasis via slit-lamp biomicroscopy
• Clear cornea
• Adequate pupillary dilation
• Anatomically normal capsular bag with no evidence of zonular weakness
• No ocular comorbidities expected to affect visual or refractive outcomes

Exclusion criteria

• Previous intraocular surgery
• Ocular trauma
• Pseudoexfoliation syndrome
• Posterior polar cataract
• Zonular instability
• Complicated cataract
• Active intraocular inflammation
• Retinal or optic nerve pathology
• Anticipated need for additional capsular support devices beyond the study protocol