Fuchs’ Dystrophy and Cataract

Treating endothelial disease and cataract: Phaco, graft, or triple procedure? Roibeárd O’hÉineacháin reports

Patients with Fuchs’ endothelial corneal dystrophy (FECD) and cataract can present a dilemma when deciding whether to perform cataract surgery alone, a triple procedure, or sequential endothelial grafting and cataract surgery, Prof Jod S Mehta PhD, FRCOphth, told the conference.

“If an FECD patient has cataract but few guttata and a good endothelial cell count, cataract surgery alone is indicated. If a patient has cataract and a lot of corneal oedema, a triple procedure is likely indicated, but between these two extremes, there is a large grey zone, and the treatment choice will depend on a detailed assessment of patient phenotype,” Prof Mehta said.

He noted mild FECD corneal guttae cause forward light to scatter, and the area of guttae correlates with visual acuity, contrast sensitivity, and intraocular straylight. He added anterior corneal changes associated with backscatter can occur in the initial stages of corneal guttae development and may precede clinically detectable oedema. In some cases, subclinical oedema may warrant endothelial keratoplasty even with the presence of fewer than five guttae and a pachymetry below 630 µm.

CATARACT SURGERY ALONE Performing cataract surgery alone improves vision in patients with early and subclinical FECD, but the visual outcomes are not as good as in patients without the corneal condition. Data from Swedish National Cataract Surgery Register showed that cataract surgery improved corrected distance visual acuity, whether or not patients had guttata. The presence of corneal guttata was significantly associated with a poorer visual acuity and worse self-assessed visual function.

In addition, cataract surgery can aggravate FECD. In the Swedish registry study, those with corneal guttata had a greater reduction in daylight and nightlight contrast sensitivity after cataract surgery compared to those without guttata, particularly in the first three postoperative weeks, but persisting for at least three months.

Furthermore, the relative risk for corneal transplant after surgery is nearly 70-fold higher in patients with guttata than patients without guttata. Besides which, the risk for transplant after cataract surgery increases three-fold when there is dense cataract posterior capsule rupture, whether a patient has guttata or not.

“This suggests that in the presence of guttata, we should perform cataract surgery earlier—otherwise, the risk of needing a transplant increases dramatically,” Prof Mehta said.

He added that among eyes with cataract and guttata but without morning blur and a central corneal thickness less than 630 µm, around 80% will achieve a good visual outcome from cataract surgery without endothelial keratoplasty and around 20% will eventually require an endothelial graft. Anterior layer corneal backscatter and relative increase in central corneal thickness following phacoemulsification are indicators of the need for endothelial graft later. THE TRIPLE OPTION Performing a triple procedure with Descemet-stripping Automated Endothelial Keratoplasty (DSAEK) or Descemet Membrane Endothelial Keratoplasty (DMEK) has poorer refractive predictability than cataract surgery alone, as the graft procedure changes the optical properties of the cornea.

He noted DSAEK induces a moderate mean hyperopic shift of around 1.0 D. But there can be a wide variability related to graft profile, the meniscal edge profile, and the difference in thickness between the periphery and the centre of the graft. DSAEK grafts made with a femtosecond laser tend to be more planar with a better centre-to-periphery thickness profile.

DMEK induces a smaller hyperopic shift of approximately 0.5 D, even though grafts are thin and planar. That is because following the graft procedure, the central oedema thins more than the peripheral oedema, and the central posterior corneal curvature steepens. In addition, the transient rise in intraocular pressure resulting from the inflation of air or gas during graft attachment may have a hyperopia-inducing effect.

Some have hypothesised that guttae alone distort the cornea’s refraction and may affect axial measurements used in IOL formulae. Moreover, small areas of epithelial oedema or preoedema can affect keratometry. As a result, triple procedures with DMEK are still not as predictable as cataract surgery alone, with around -47% within -0.5 D of target refraction and 60% within 1.0 D.

DMEK THEN CATARACT In some patients with cataract, it may be more advisable to perform DMEK first and then perform the cataract procedure based on the postoperative refraction. This could include cases with localised bullae, which can complicate biometry, or younger patients (those below the age of 50 with minimal cataract).

Oedema in the paracentral cornea can lead to apparent central cornea flattening preoperatively. So when the oedema clears after endothelial keratoplasty, the cornea steepens, causing a myopic shift. In some cases of FECD, corneal tomography has shown that after DMEK, there will be “hot spots” on the posterior corneal surface in the area where the oedema was. That can be an indication of subclinical keratoconus or stromal loss.

This presentation was made at the 39th Congress of the ESCRS in Amsterdam.

Prof Jod S Mehta BSc (Hons), MBBS, PhD, FRCOphth, FRCS(Ed), FAMS is Distinguished Professor of Clinical Innovation, Head of the Corneal and External Eye Disease Service, and Senior Consultant Refractive Service, Singapore National Eye Centre. Jodmehta@gmail.com