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Hydrophobic vs hydrophilic IOLs: what is the difference and what does the evidence show
Agaaz Ophthalmics, clinical and technical article · 12 October 2026
In brief: hydrophobic acrylic IOLs contain less than 1% water, hydrophilic ones roughly 18–38%. In randomised trials, hydrophobic acrylic is associated with less posterior capsule opacification and a lower need for YAG capsulotomy. Hydrophilic acrylic is easier to handle and does not develop glistenings, but late calcification has been reported, primarily after gas or air is introduced into the eye. Rigid PMMA lenses remain a practical option for surgery with a 5.5–6.0 mm incision.
The three main intraocular lens materials
PMMA (polymethyl methacrylate) was the first IOL material and has the longest clinical track record. The lens is rigid, cannot be folded and requires an incision equal to the optic diameter — 5.5–6.0 mm. PMMA is therefore used in extracapsular extraction and manual small-incision cataract surgery (MSICS), including in high-volume programmes.
Hydrophilic acrylic — copolymers based on hydroxyethyl methacrylate (HEMA). The material is hydrated (around 18–38% water), is supplied in liquid, folds easily and unfolds gently in the capsular bag.
Hydrophobic acrylic — copolymers of phenylethyl acrylate and phenylethyl methacrylate and related formulations with a water content below 1%. It usually has a higher refractive index, allowing a thinner optic; it unfolds more slowly, and the unfolding speed depends on the glass transition temperature of the material.
| Property | PMMA | Hydrophilic acrylic | Hydrophobic acrylic |
|---|---|---|---|
| Water content | 0% | ~18–38% | <1% |
| Foldable | No | Yes | Yes |
| Incision | 5.5–6.0 mm | 2.2–2.8 mm | 2.2–2.8 mm |
| PCO and YAG capsulotomy | Depends on edge design | More frequent than with hydrophobic | Less frequent |
| Typical late change | “Snowflake” degeneration of older PMMA lenses (rare) | Calcification | Glistenings, subsurface nanoglistenings |
Posterior capsule opacification: the main argument for hydrophobic acrylic
The meta-analysis by Li et al. (2013) pooled 9 randomised trials (861 eyes) with at least one year of follow-up. PCO was less pronounced with hydrophobic acrylic IOLs at 1 and 2 years, and the relative risk of YAG capsulotomy at 2 years for hydrophilic versus hydrophobic lenses was 6.96 (95% CI 3.69–13.11) [1].
Long-term data are consistent with this. In a randomised trial by Chang and Kugelberg (Karolinska Institutet), 9 years after phacoemulsification the hydrophilic lens showed more and denser PCO, and the proportion of eyes without YAG capsulotomy was significantly higher with the hydrophobic IOL, even though both lenses had a sharp posterior edge [2].
Practical takeaway: a 360° sharp edge remains an essential design feature of any foldable IOL, but on its own it does not make the materials equivalent. If YAG capsulotomy rates matter in a clinic's protocol, the material is an independent factor.
Glistenings: a feature of hydrophobic acrylic
Glistenings are fluid-filled microvacuoles within the optic, ranging from 1 to more than 25 µm in size; subsurface nanoglistenings are smaller than 200 nm [3]. They develop predominantly in hydrophobic acrylic lenses and are associated with ingress of aqueous humour into the polymer matrix. In most cases glistenings do not reduce visual acuity and do not require IOL exchange, but they can increase light scatter and affect quality of vision [4, 5]. Susceptibility to glistenings varies widely between materials and models, so it makes sense to ask the manufacturer for data on the specific polymer.
Calcification: a feature of hydrophilic acrylic
Calcification is the deposition of hydroxyapatite or other calcium phosphates on or beneath the surface of the optic. It is the most common type of late opacification of hydrophilic IOLs; it usually impairs visual function and, as a rule, requires lens explantation [4].
Known risk factors are a hydrophilic material and the introduction of gas or air into the eye. In the series by Darcy et al. (15 cases), calcification developed after endothelial keratoplasty with gas, vitrectomy with gas tamponade, trabeculectomy and implantation of a supplementary sulcus IOL; the opacification had a characteristic central location on the anterior optic surface [6]. The review by Grzybowski et al. (2020) specifically highlights the risk with DSAEK, DMEK and vitrectomy, procedures whose frequency is increasing [5].
Practical takeaway: in patients who are likely to need keratoplasty with gas or vitrectomy, this risk is worth considering when choosing the material.
Lens handling and economics
Hydrophilic lenses unfold gently, pass easily through small cartridges and are generally less expensive. Hydrophobic lenses require attention to temperature and unfolding time; materials with a low glass transition temperature are easier to fold and unfold. For high-volume programmes and manual techniques, PMMA retains advantages in cost and material stability.
Factors usually considered when choosing the material
- Surgical technique: phacoemulsification with a 2.2–2.8 mm incision — foldable lens; MSICS or ECCE — PMMA.
- PCO and access to YAG laser: where YAG capsulotomy is hard to access or undesirable, PCO data favour hydrophobic acrylic [1, 2].
- Future procedures involving gas or air: consider the risk of calcification with hydrophilic lenses [5, 6].
- Optical requirements: asphericity, blue-light filtering and extended depth of focus are properties of the design, not just the material.
- Programme budget and logistics: lens cost, injectors and cartridges, storage conditions.
These factors are general in nature; the final choice of IOL for a patient is the surgeon's decision, taking into account the manufacturer's instructions for use.
Agaaz IOLs by material
Hydrophobic acrylic
OP-VIEW AS — aspheric, n = 1.557, 360° sharp edge, UV and blue-light filter, glass transition temperature 11.4 °C.
TRICENTRA — three-piece, 6.0 mm optic, PMMA haptics.
Hydrophilic acrylic
OP-FOLD AS — aspheric, sharp edge.
i-Nera — aspheric, 6.0 mm optic, C-loop haptics, injector delivery.
PMMA
OP-LENS — n = 1.42, optic 5.5 / 6.0 mm, clear and yellow versions.
All models and parameters are on the page “Agaaz intraocular lenses”. For a comparison of EDOF and trifocal optics, see the article “EDOF IOLs: how they work”.
References
- Li Y, Wang J, Chen Z, Tang X. Effect of hydrophobic acrylic versus hydrophilic acrylic intraocular lens on posterior capsule opacification: meta-analysis. PLoS One. 2013;8(11):e77864. doi:10.1371/journal.pone.0077864
- Chang A, Kugelberg M. Posterior capsule opacification 9 years after phacoemulsification with a hydrophobic and a hydrophilic intraocular lens. Eur J Ophthalmol. 2017;27(2):164–168. doi:10.5301/ejo.5000831
- Kanclerz P, Yildirim TM, Khoramnia R. Microscopic characteristics of late intraocular lens opacifications. Arch Pathol Lab Med. 2021;145(6):759–767. doi:10.5858/arpa.2019-0626-RA
- Kanclerz P, Yildirim TM, Khoramnia R. A review of late intraocular lens opacifications. Curr Opin Ophthalmol. 2021;32(1):31–44. doi:10.1097/ICU.0000000000000719
- Grzybowski A, Markeviciute A, Zemaitiene R. A narrative review of intraocular lens opacifications: update 2020. Ann Transl Med. 2020;8(22):1547. doi:10.21037/atm-20-4207
- Darcy K, Apel A, Donaldson M, et al. Calcification of hydrophilic acrylic intraocular lenses following secondary surgical procedures in the anterior and posterior segments. Br J Ophthalmol. 2019;103(12):1700–1703. doi:10.1136/bjophthalmol-2018-313385
This article is intended for healthcare professionals and does not replace the instructions for use of a specific IOL. The publications in the reference list concern material classes and are not studies of Agaaz products. See also: Agaaz intraocular lenses.
