Prospective randomized control trial measuring posterior capsular opacification rates and visual outcomes following insertion of two monofocal intraocular lenses: the hydrophobic RayOne 800C and the hydrophilic RayOne 600C: 12-month results

Cataract surgery is the most common elective operative procedure in the European Union.¹ Posterior capsular opacification (PCO) is the most common complication post-cataract surgery, with 9-year rates of 47%.² PCO occurrence is associated with surgical technique, axial length, age, and intraocular lens (IOL) properties (IOL material, haptic and optic edge design, and optic size).^3–8 Past studies have reported that hydrophobic (HPB) acrylic IOLs are less likely to develop PCO compared with hydrophilic (HPL) IOLs.^3,7,8 However, the HPB/HPL IOLs in these studies were from different manufacturers with variations in manufacturing processes and haptic, optic, and edge designs, which would have introduced confounding factors regarding PCO development in addition to the HPB/HPL material itself.

By contrast, this study compared the PCO rates with 2 aspheric monofocal IOLs from the same manufacturer which, except for their material properties, had similar edge, optic, and haptic designs and dimensions. We report preliminary 12-month rates of visually significant PCO requiring Nd:YAG laser capsulotomy and percentage areas of PCO within the central 4.00 mm of the IOL.

This was a single-center, prospective, open-label, observer-masked, randomized case–control study (randomized control trial [RCT]) (REC reference number 19/WA/0273, ClinicalTrials.gov reference number NCT04122664). Inclusion criteria were adult patients with full capacity and symptomatic cataract. Exclusion criteria were previous ocular surgery, amblyopia, glaucoma, corneal scarring, significant retinal pathology, and any ocular/neurological condition affecting vision.

After consent, patients were randomized to receive either a HPB or HPL IOL during cataract surgery. Patients were blinded to the randomization process and were implanted with either the aspheric RayOne 600C single-piece, HPL, acrylic IOL (Rayner Intraocular Lenses Ltd.) or the aspheric RayOne 800C single-piece, HPB acrylic IOL (Rayner Intraocular Lenses Ltd.). The standard care postoperative drop regimen was 0.1% dexamethasone QDS for 1 month and 0.5% chloramphenicol QDS for 2 weeks. Patients were seen at 1 month, 6 months, 12 months, and 24 months after cataract surgery.

Primary endpoints were development of visually significant PCO requiring Nd:YAG laser capsulotomy and mean percentage area of PCO within the central 4.00 mm of the IOL measured from retroilluminated, digital photographs of the lens capsules taken with a slitlamp-mounted, 5-megapixel, digital camera lamp (Topcon SL-701, Topcon Corp.) after mydriasis. The anonymized retroillumination images were viewed on Microsoft Paint (Microsoft Corp.), and a 700 pixel diameter fluorescent circle (equating to approximately 4.00 mm) was placed in the center of the IOL image. Areas of PCO within the circle were shaded by 3 clinicians independently. The percentage of shaded area within the circle was calculated by encoding a calculation function using Python v. 3.10 (Python Software Foundation).

The first operated eye for each patient was analyzed. Shapiro-Wilk testing was used to check for normality. For parametric data, the independent sample t test was used to analyze differences between groups, and the paired t test was used for dependent samples. Patient demographic data were compared using the Fisher exact test. Statistical significance was set at P < .05.

One hundred patients were enrolled. Eight withdrew pre-cataract surgery, and 7 were withdrawn post-cataract surgery (including 3 cases of intraoperative complications where a single-piece IOL was not placed, and 3 requiring early Nd:YAG laser posterior capsulotomy due to retained ophthalmic viscosurgical device [OVD]). Eighty-five eyes were included in final analysis.

There were no statistically significant differences in the baseline demographics between the 2 groups except for a slightly lower age range in the HPB group (Table 1). Table 2 presents the 12-month postoperative outcomes between the patients of the HPB and HPL IOL groups. No cases required a Nd:YAG laser posterior capsulotomy within the first 12 months for PCO. The mean percentage area of PCO within the central 4 mm diameter at 12 months was 3.64% in the HPL group and 3.83% in the HPB group (P = .86). The intraclass correlation coefficient to assess the level of agreeability between the 3 clinicians grading the level of IOL PCO was 0.852 (P < .001), showing a high level of agreeability. There were 5 cases of postoperative cystoid macula oedema (2 HPL, 3 in HPB), 3 cases of postoperative iritis (2 in HPL, 1 in HPB), and 2 cases of intraoperative posterior capsular rupture requiring a sulcus 3-piece IOL in the HPB group. There were 2 cases of zonular dialysis in the HPL group, with 1 case requiring a secondary sutured IOL due to a lack zonular support. Three eyes required YAG laser posterior capsulotomy laser due to retained OVD.

Table 1.

Baseline demographics

Parameter	Hydrophilic (n = 40) Mean ± SD	Hydrophobic (n = 45) Mean ± SD	P value
Age (y)	72.35 ± 7.13	68.71 ± 9.37	.049
Sex (M:F)	17:23	22:23	.66
UDVA (logMAR)	0.86 ± 0.41	0.65 ± 0.35	.06
CDVA (logMAR)	0.48 ± 0.38	0.57 ± 0.39	.33
IOP (mm Hg)	14.33 ± 3.56	13.80 ± 3.55	.50
ECC	2513 ± 246.1	2562 ± 281.9	.40
AL (mm)	23.78 ± 1.22	23.89 ± 0.89	.66
CatPROM-5a	−0.50 ± 1.74	0.08 ± 2.31	.20
EQ5D3La	0.85 ± 0.20	0.89 ± 0.18	.37
EQ5D3L raw score	85.03 ± 14.60	83.78 ± 16.24	.71

AL = axial length; ECC = endothelial cell count

^aCalibrated score

Table 2.

Postoperative data at 12-month follow-up

Parameter	Hydrophilic Mean ± SD	Hydrophobic Mean ± SD	P value
UDVA at 12 mo (logMAR)	0.09 ± 0.14	0.16 ± 0.19	.06
CDVA at 12 mo (logMAR)	−0.03 ± 0.10	−0.02 ± 0.11	.53
SE at 12 mo	−0.32 ± 0.43	−0.36 ± 0.57	.73
SE within 0.50 D of target SE at 12 mo (%)	84.21	77.78	.58
SE within 1.00 D of target SE at 12 mo (%)	97.37	100	.46
ECC (preop vs 1 mo)	−360.10 ± 384	−225.40 ± 285.70	.11
Change in CatPROM-5a (preop vs 12 mo)	−4.27 ± 2.74	−5.32 ± 2.81	.13
Change in EQ5D3La (preop vs 12 mo)	+0.06 ± 0.23	+0.03 ± 0.22	.66
Change in EQ5D3L raw score (preop vs 12 mo)	+7.53 ± 16.70	+4.60 ± 17.67	.48
Nd:YAG capsulotomy for PCO by 12 mo (n)	0	0	1.00
PCO grading at 1 mo	2.05 ± 1.30	2.53 ± 1.59	.18
PCO grading at 6 mo	1.92 ± 1.02	2.49 ± 2.43	.22
PCO grading at 12 mo	3.64 ± 4.33	3.83 ± 4.51	.86

ECC = endothelial cell count; PCO = posterior capsular opacification

^aCalibrated score

PCO remains the most common post-cataract surgery complication.² Previous studies have suggested that the HPB/HPL nature of IOL material is an important factor in PCO development.^2,3,7–14 However, in this RCT, we found no statistically significant differences in measured percentage areas of PCO or Nd:YAG laser posterior capsulotomy rates for PCO at 12-month follow-up.

In a meta-analysis, Zhao et al. concluded that PCO development and Nd:YAG capsulotomy rates were higher for HPL IOLs, while in a retrospective cohort study in more than 900 eyes, Johansson et al. reported doubled Nd:YAG laser rates with HPL IOLs at 5 years.^11,12 RCTs by Heatley et al. and Chang et al. showed higher PCO rates with HPL IOLs.^3,7 However, in both studies, lenses from 2 different manufacturers, featuring distinct platform designs and material compositions, were used. Heatley et al. used the Centerflex HPL IOL (Rayner Intraocular Lenses Ltd.) with a 12.00 mm overall diameter and 5.75 mm optic diameter, with a square-edge profile, and the AcrySof HPB IOL (Alcon Laboratories, Inc.) with a 13.0 mm overall diameter, an optic diameter of 6.0 mm, and a square edge profile.³ In the study by Chang et al., the AcrySof SA60AT HPB IOL (Alcon Laboratories, Inc.) and the BL27 HPL IOL (Bausch & Lomb, Inc.) which had a length of 10.75 mm and optic diameter of 6.0 mm were used.⁷

Not all studies document increased PCO rates with HPL IOLs. Kang et al. in a RCT of 100 eyes receiving either the HPL BioVue3 IOL (BioVue, OII) or the HPB Sensar IOL (AR40e, Abbott Medical Optics, Inc.) found no differences at 12 months.¹⁰ Koshy et al. reported no differences between eyes implanted with the HPL Superflex IOL (Rayner Intraocular Lenses Ltd.) and the HPB AcrySof SA60AT (Alcon Laboratories, Inc.) at 2 years.¹² The IOLs investigated in these studies had square-edged designs. Bellucci et al. conducted a retrospective contralateral study comparing the HPB 877 ABY IOL (Medicontur) and the HPL 677 ABY IOLs (Medicontur), both featuring similar optic shapes and square-edge designs and found no differences at 5 years.¹³ This suggests that categorizing IOLs solely as HPL or HPB regarding PCO development, overlooks inherent variations among lenses, distorting perspective of what is a complex, multifaceted issue, and underscoring the need for more case-by-case examination of the safety profiles of each IOL platform and material.

A strength of our study is that we have used IOLs from the same manufacturer with both aspheric single-piece IOLs having the same length (12.50 mm), optic diameter (6.0 mm), and a 360-degree square edge, albeit with a slight variation in design of the square edge. This goes some way to limit other confounding factors, as seen in past studies. We measured PCO by considering Nd:YAG laser posterior capsulotomy rates and directly measuring the percentage area of PCO within the central 4 mm diameter of the IOL. To optimize the accuracy of our measurements, we used 3 clinicians to independently measure PCO area for each IOL and found a high level of reliability between the 3 raters (intraclass correlation coefficient of 0.852).

We found no significant differences in intraoperative or postoperative complication rates between the HPL group and the HPB group. Three required Nd:YAG laser posterior capsulotomy for retained OVD in the HPB group. There was 1 adverse event where an IOL was noted to be damaged in the HPB group. Removal of the IOL from the capsular bag led to zonular dialysis, and the patient underwent a sutured secondary intraocular lens implantation.

We appreciate the limitations of our study. The study was commenced at the start of the COVID-19 pandemic; restrictions in clinical and surgical activity and national lockdowns had a significant impact on patient recruitment into the study. Nevertheless, we enrolled 100 patients, and our number of patients are comparable with other published prospective RCTs.^4,7,10 We appreciate that 12 months is an early stage for postoperative PCO development and will continue follow-up to 24 months. We note that the cataract surgery eye was performed by a range of surgeons, including senior residents, and that variations in surgical technique may affect PCO development.^2,3 However, this surgeon range is more reflective of day-to-day practice within the public health sector.

This RCT demonstrated no statistically significant differences in PCO rates between the aspheric, acrylic, single-piece hydrophobic RayOne 800C IOL and the aspheric, acrylic, single-piece hydrophilic RayOne 600C. PCO rates remained very low, reinforcing the similar performance of these 2 IOL models in posterior capsule opacification prevention. It suggests that both IOL platforms offer comparable efficacy, highlighting the importance of individualized selection based on patient needs rather than material classification alone.