Cataract Solutions in Patients with Glaucoma

Cataract and glaucoma commonly coexist with cataract surgery frequently forming an important part of glaucoma management.¹ Significant falls in intraocular pressure (IOP) have been demonstrated, not only in angle closure glaucoma, but also in primary and secondary open angle glaucoma following cataract surgery.^1,2 The advent of simultaneous trans-trabecular bypass, further supports the importance of cataract surgery in glaucoma management.³ 

Many surgeons would offer multifocal intraocular lenses (IOL) to their patients, but very few would opt for these themselves…

Cataract surgery can also be central to improving visual performance for the patient and improving the fidelity of glaucoma testing.⁴ Optical coherence tomography (OCT) metrics and visual field will become affected by cataract at some point in the journey, and subjective blur due to cataract can be difficult for patients to discern from blur due to glaucoma.⁵ Cataract surgery is also an opportunity to address current refractive failings, although here the question is more vexed for patient and surgeon.

CHOOSING AN IOL

In a recent survey of ophthalmologists performing cataract surgery in the United Kingdom, it was interesting to note the significant disparity between what the surgeon offered the patient and what they would want for themselves. Many surgeons would offer multifocal intraocular lenses (IOL) to their patients, but very few would opt for these themselves, instead choosing some form of monofocal IOL in both eyes set for distance.⁶

Subtle loss of central contrast and sensitivity can occur even relatively early on in glaucoma and more advanced glaucoma may be associated with substantial loss of central sensitivity.^7,8 Increasing lifespan and some expected worsening over time suggests that the choice of IOL should take into account macular capacity in the future, not just at the time of surgery.⁹ If you add to this the dynamic changes in macular function that occur with age, and perhaps some age-related macular degeneration, preserving as much contrast and magnification as possible seems prudent.

Other notable considerations in IOL selection include:¹⁰ 

• Choice of material,
• One-piece or three-piece,
• In-bag stability for astigmatism correction, and
• Any pigmentation (i.e., blue light filtering with a yellow chromophore).

IOL PREFERENCES

Material considerations in IOLs are predominantly related to long-term calcification issues.⁹ A number of IOLs have developed significant calcific opacification, usually following a second procedure.^9,11 In particular, hydrophilic acrylic material is a known risk factor for IOL calcification.^9,11 Thus, because there is increased risk of a second procedure in the glaucomatous eye,^12,13 it is now policy at Melbourne Eye Specialists to avoid hydrophilic acrylic IOLs in these patients with a wholesale move to hydrophobic material. This is the case, except in patients who require very high or low power IOLs (such as in nanophthalmos and pathologic myopia), whereby there is a lack of capsular stability or coexisting anterior segment trauma.

Single piece IOLs are generally preferred, but if a sulcus supported IOL position is required, then a three-piece IOL should be used.¹⁴ These IOLs can be sown in if required.

IN-BAG STABILITY FOR ASTIGMATISM CORRECTION

Correction of astigmatism in glaucoma is valuable and should be attended to, unless it is caused by low pressure or some distortion of a filtration bleb onto the cornea. Full corneal mapping should be undertaken as this type of astigmatism will be eccentric and nearer the bleb. Cataract surgery in low pressure is more difficult and pre-operative calculation for IOLs needs to be performed with significant care and with comparison to the fellow eye, assuming it does not also have hypotony.

If cataract surgery is being performed with glaucoma surgery, then it is important to choose an IOL that has a decreased chance of de-rotation, which usually occurs due to adherence to the capsule. Based on clinical experience, the IOL will shift forwards if the eye decompresses and may de-rotate. Hydrophobic acrylic single piece lenses often adhere to the capsule well and will resist hypotony-induced rotation.¹⁵

IOL ROTATION: CLINICAL TRIALS UPDATE

In recent studies, both Hoya’s Vivinex IOL and Alcon’s Acrysof toric IOL demonstrated good post-operative stability.^16,17 Schartmüller et al (2019) assessed rotation of Hoya’s Vivinex IOLs at the end of surgery and one hour, one week, one month, and six months after implantation in 122 eyes of 66 patients.¹⁶ Results showed that 100% of the implanted lenses (n=103) had ≤5° rotation from the initial axis at all timepoints following surgery to six months postoperatively.¹⁶ 

In a separate retrospective cohort study performed by Lee & Chang (2018), the rotational stability of Alcon’s Acrysof toric IOL and Johnson & Johnson Vision’s Tecnis toric IOL was assessed in 1,273 consecutive eyes, at least one hour postoperatively on the day of surgery or the next morning.¹⁷ At the first postoperative check, 91.9% of the Acrysof toric IOLs rotated ≤5° versus 81.8% of Tecnis toric IOLs (p<0.0001).¹⁷ The mean rotation was 2.72° for Acrysof and 3.79° for Tecnis toric IOLs (p<0.05).¹⁷ Unlike the Acrysof IOL, the Tecnis toric IOL showed a strong predisposition to rotate counter-clockwise.¹⁷ In addition, 3.1% of Tecnis toric IOL patients required repositioning versus 1.6% with Acrysof (p=0.10, not significant).¹⁷

IOL PIGMENTATION

While glare is difficult to measure objectively, one of the significant advantages of a low level of yellow pigmentation in the IOL is decreased glare. Characteristically, glare increases with age and so, for patients with glaucoma, a low glare IOL would seem a sensible choice.^18,19 

MONOFOCAL VERSUS MULTIFOCAL IOLS

So, we come to the question of symmetric post-operative refraction with monofocal IOLs, some degree of myopia in the nondominant eye, or the use of a bilateral multifocal intraocular lens. To put this question into context, it really only applies to patients with early disease that is likely to be well-managed, with little or no glaucoma progression over the rest of their lives. Patients with a significant risk of macular degeneration, or any other ocular condition, are probably inappropriate for multifocal IOLs and therefore more suited to monovision IOLs.^† We know that risk of falling is one of the big threats to healthy ageing and that the risk of falls is increased with cataract and glaucoma.²⁰ Risk of falls can also be increased by wearing multifocal glasses, so discussions between the patient and their optometrist/ophthalmologist on fall prevention are important. Furthermore, slowed dark adaptation can increase the risk of falls and this can potentially be avoided if explained to the patient.²²

CONCLUSION

Modern glaucoma management can be considered as a form of risk analysis and mitigation – there are risks of under and over-treatment. Matching treatment to risk is one of the key clinical considerations. The more complex the IOL choice, particularly if involving multifocality, the greater the risk that the patient will be less well off, a risk that is very difficult to predict ahead of time. The simplest solution may be for the patient to support their vision with glasses and sunglasses to provide safe and adequate ambulatory and night-time vision in both eyes, rather than a multifocal lens.

Associate Professor Michael Coote is a Senior Glaucoma Consultant at the Royal Victorian Eye and Ear Hospital Melbourne. He is the Managing Partner of Melbourne Eye Specialists. 

For a full list of indications, contraindications and medical conditions relating to the implantation of Hoya IOLs, please refer to the instructions for use. 

† There are no known contraindications for the implantation of Hoya Vivinex monofocal aspheric IOLs into the capsular bag after extracapsular cataract removal. However, for patients suffering from certain medical conditions or combinations of conditions, such as macular degeneration and glaucoma, the surgeon should carefully evaluate the pre-operative situation and make sound clinical judgement on the risk benefit of implantation. 

This article was sponsored by an educational grant from Hoya Surgical Optics. The views and opinions expressed in this article by the clinical expert do not necessarily reflect the views and opinions of Hoya Surgical Optics. 

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