Delivering Uncompromising Cataract Care

Cataract surgery in patients with compromised corneas presents many complexities. A recent ESCRS eConnect webinar hosted by Iva Dekaris MD, PhD and Massimo Busin MD gathered a panel of experts to discuss the challenges and innovative solutions available.

Elisabeth Patsoura MD began the discussion by noting cataract surgery always carries some risk to the cornea, especially in eyes with corneal disease. However, a careful, standardised approach can minimise these risks.

She pointed out a significant percentage of cataract patients also have dry eye disease, which can be aggravated by cataract surgery. Factors include preoperative and postoperative medications, the surgical microscope’s phototoxic effects, the corneal incision, and the speculum or docking station.

Fortunately, ophthalmologists can adopt several measures to mitigate the impact of cataract surgery on the ocular surface. These include the use of intracameral mydriatics, the topical application of dispersive ophthalmic viscosurgical devices (OVDs), and reducing the intensity of the microscope illumination during stages where such bright light is unnecessary. They should also consider postoperative administration of preservative-free topical antibiotics, steroids, and dry eye medications, Dr Patsoura said.

Eyes susceptible to endothelial loss from cataract surgery include those with concurrent corneal pathologies such as Fuchs’ endothelial dystrophy syndrome or even keratoconus. Additionally, eyes with inflammatory ocular diseases, previous angle-closure glaucoma, pseudoexfoliation, shallow anterior chambers, hard nuclei, or systemic conditions such as diabetes are also at risk.

Dr Patsoura observed research has shown a soft-shell OVD technique reduces endothelial cell loss. She added nuclear fragmentation with phaco-chop is better than stop-and-chop and divide-and-conquer techniques because it requires less phaco time and energy. Using torsional phaco is safer than longitudinal phaco for the same reason, and burst mode is also safer than continuous linear mode, especially for corneas with a low endothelial cell count.

IOL calculation in eyes with corneal ectasia

Recent IOL power calculation formulas tailored for keratoconus-affected eyes demonstrate reduced prediction errors compared to traditional formulas. The ESCRS IOL power calculator has supported surgeons in performing calculations using these advanced formulas, said Joaquín Fernández MD, PhD.

He noted conventional formulas often lead to a hyperopic shift in keratoconus that increases with each disease stage. The older formulas assume a normal anterior-posterior corneal ratio, which is disrupted in keratoconic eyes. The irregularity of the cornea in such eyes can lead to unreliable keratometry readings. Furthermore, irregular corneas affect vision quality, making refraction measures unreliable and repeatability poor.

Studies comparing the accuracy of older IOL calculation formulas in eyes with keratoconus have consistently shown the SRK/T formula has the lowest prediction errors. However, a recent meta-analysis shows the newer formulas optimised for keratoconus provide results comparable to those achieved in normal eyes. The best performance was reported by the Barrett True-K formula using a measured posterior (BTK-MPC), followed by the Barrett True-K using predicted posterior cornea (BTK-PPC) and the Kane formula.¹

Surgeons can access the new formulas with measured posterior cornea through the online ESCRS IOL power calculator. In the case of the BTK formula, surgeons specify the history of keratoconus, whether the posterior cornea is measured or predicted, the biometer used, and whether they will be implanting a toric IOL. In the case of the Kane formula, surgeons simply specify the eye has keratoconus, Professor Fernández said.

Improving visualisation

Moving the conversation to the surgical stage, Björn Bachmann MD said there are several strategies to enhance visualisation during cataract surgery in patients with opacified corneas.

The primary incision should be opposite the clearest part of the cornea. To achieve a good red reflex, the pupil should be maximally dilated using either pharmaceutical or mechanical methods. Coaxial lighting is preferable over full-field illumination to minimise glare.

When the cataract procedure is combined with vitrectomy, an intravitreal endolight or chandelier is another option. It has the advantage of reduced stray light with little reflection and high contrast. However, it is important to keep the light at a safe distance from the posterior capsule to prevent capsular tears. An anterior light source at a lower intensity will enhance the three-dimensional perception of the intraocular structures.

In triple Descemet membrane endothelial keratoplasty (DMEK) procedures, removing the oedematous corneal epithelium enhances visualisation during cataract surgery. Alternatively, or additionally, glycerine eye drops can be applied. Techniques to avoid staining diseased endothelium with trypan blue include filling the anterior chamber with air before injecting the dye or using OVD and manipulating the cannula near the anterior lens capsule.

Combined keratoplasty procedures in complex cases

In recent years, surgeons have transitioned predominantly to lamellar keratoplasty. At Moorfields Eye Hospital, DMEK accounts for half of the keratoplasty procedures, with one-third involving combined surgery with phacoemulsification, said Alfonso Vasquez-Perez MD.

Combined cataract and DMEK procedures are recommended for Fuchs’ dystrophy patients aged 55 or older with adequate cornea visualisation for safe phacoemulsification, a corneal thickness greater than 640 microns, and diurnal vision fluctuations. It is important to use hydrophobic acrylic IOLs because air tamponade can cause opacifications in hydrophilic lenses. The difference in biometric readings, specifically keratometry, before and after DMEK is minimal.

For cataract patients needing deep anterior lamellar keratoplasty (DALK), sequential surgeries generally provide optimal refractive outcomes. However, for patients without useful vision in the other eye, a combined procedure might be more suitable. In such cases, the combined procedures typically begin with a partial keratectomy to enhance visualisation during the cataract surgery. Manual dissection of the stroma during the DALK procedure may be preferred over the big-bubble technique to avoid the need for conversion to penetrating keratoplasty.

In rare cases, such as a corneal perforation, an open-sky triple procedure may be necessary. General anaesthesia is recommended. After trephination, performing the capsulorhexis in dry conditions with vision blue improves visualisation. Following cataract extraction, it is best to insert the IOL vertically into the bag and finish by suturing the graft.

The webinar can be seen in its entirety on the ESCRS website.

Massimo Busin MD is based at University of Ferrara, Ferrara, Italy. mbusin@yahoo.com

Iva Dekaris MD, PhD is based at Eye Hospital Svjetlost, University of Rijeka, Zagreb, Croatia. Iiva.dekaris@gmail.com

Elisabeth Patsoura MD, MRCOphth is based at Ophthalmos Research &Therapeutic Institute, Athens, Greece. ophthalmos@ophthalmos.gr

Joaquín Fernández Pérez MD, PhD is based at Qvision, Department of Ophthalmology of Vithas Almería Hospital, Almería, Spain. joaquinfernandezoft@qvision.es

Björn Bachmann MD, FEBO is based at University Eye Clinic, Cologne, Germany. bjoern.bachmann@uk-koeln.de

Alfonso Vasquez-Perez MD, FRCOphth, CertLRS, FEBOS-CR is based at Moorfields Eye Hospital, London, UK. alfonsoperez.1@nhs.net

1. O Reitblat, et al. “Intraocular lens power calculation accuracy in patients with keratoconus: Network meta-analysis and systematic review,” Clinical & Experimental Ophthalmology, 2024 Dec 3. doi:https://doi.org/10.1111/ceo.14470