CASE PRESENTATION
A 67-year-old man presents with nuclear sclerotic and posterior subcapsular cataracts in both eyes, secondary to prolonged topical steroid use and age. The patient underwent bilateral corneal transplantation for keratoconus in 1984. Astigmatic keratotomies failed to reduce his astigmatism and instead increased its irregularity (Figure).
Figure. Imaging with the Pentacam (Oculus Optikgeräte) shows irregular astigmatism in both eyes after corneal transplantation. An astigmatic keratotomy in each eye failed to reduce the astigmatism and instead increased its irregularity.
Despite aggressive treatment, dry eye disease has made wearing scleral contact lenses increasingly problematic, so the patient typically depends on glasses. His BCVA is 20/70 OD with a manifest refraction of +2.25 +6.25 x 160º and 20/150 OS with a manifest refraction of +2.00 +4.00 x 78º.
A slit-lamp examination finds a clear corneal graft and early nuclear sclerosis in each eye. Retinal examination findings and OCT scans of the macula and optic nerve head nerve are normal.
How would you proceed?
—Case prepared by Karl G. Stonecipher, MD
KENDALL E. DONALDSON, MD, MS
In situations like this, successful cataract surgery generally requires significant patient engagement. Fortunately, these individuals typically have been active participants in their eye care since their keratoconus diagnosis, and many of them have a reasonable understanding of astigmatism.
During the preoperative consultation, it is essential to differentiate corneal from lenticular pathology to decrease the frustration patients may experience after surgery if they struggle to adjust to a new refractive error. They should also be informed that their postoperative course and visual outcomes may differ from those of their friends and family members without keratoconus who have undergone cataract surgery.
In addition to standard topography and tomography, measurements with an iTrace (Tracey Technologies) would be obtained to help differentiate corneal from lenticular pathology. This instrument can also simulate the pinhole effect of a small-aperture IOL such as the IC-8 Apthera (Bausch + Lomb) and the effect of correcting regular astigmatism with a toric IOL. In my experience, such simulations can be immensely helpful when choosing a lens and setting realistic patient expectations.
The patient’s right eye has both regular and irregular astigmatism as well as the appearance of pellucid marginal degeneration, with a 15.00 D difference between the lowest and highest points within the central 3 mm of the cornea. The multifocality of the cornea could compromise the accuracy and predictability of IOL calculations. In my experience, an Apthera lens typically cannot compensate for the degree of irregular astigmatism present in the right eye. Although a Light Adjustable Lens (LAL; RxSight) might be able to compensate for the unpredictable central corneal power, the patient must understand in advance that the postoperative process of refractive stabilization and light adjustment procedures might require several months and is unlikely to deliver a perfect visual result—although the outcome might be better than with any other alternative. A toric IOL could be considered if the axis of astigmatism is consistent across topography/tomography, biometry, and refraction and the patient does not plan to wear contact lenses in the future. Another option would be a standard monofocal lens targeted for -1.00 to -2.00 D of myopia.
Compared to the right eye, the astigmatism in the left eye is more regular with a consistent with-the-rule axis. If the axis of astigmatism is consistent across topography/tomography, biometry, and refraction, a toric IOL could be considered, with the understanding that the lens would greatly debulk but not eliminate the cylinder. Another option would be to implant a standard monofocal lens with a slightly myopic refractive target (approximately -1.00 to -2.00 D).
CRISTOS IFANTIDES, MD, MBA
Both corneas are highly aberrated with a significant amount of astigmatism and a possible recurrence of keratoconus. If the patient is no longer able to tolerate scleral contact lenses, incisional surgery is probably the best option, especially because his BCVA is insufficient for the typical activities of daily living. The pachymetry readings obtained after corneal transplantation appear to be acceptable for surgery.
No currently available IOL is capable of resolving all the problems in either eye, so I would employ a staged approach. An Apthera lens would be implanted bilaterally (off-label use). Once the refraction stabilizes—typically 1 to 2 months after surgery—if the patient is unhappy with the quality of vision in either or both eyes, an aspheric toric IOL could be implanted in the bag. Alternatively, an LAL could be placed in the sulcus. I am cautious about the use of an LAL in situations like this because subsequent light treatments of the lens can induce higher-order aberrations (HOAs) that cause “waxy” vision.
ROGER ZALDIVAR, MD, MBA
Several details in the case presentation make me leery of implanting a toric IOL without first trying to improve the patient’s BCVA by decreasing the magnitude of astigmatism and HOAs.
One strategy would be the femtosecond laser–assisted placement of an intrastromal corneal ring segment in each eye. I have performed this procedure for the past 10 years with great success.1 Six months postoperatively, cataract surgery would be performed with the implantation of either a small-aperture IOL or an LAL. I do not have experience with the latter but appreciate the technology’s postoperative adjustability.
Alternatively, primary implantation of a small-aperture IOL could be performed to neutralize HOAs. An advantage of this approach is it could improve his quality of vision, especially at night, by neutralizing the optical effects of the corneal transplant. A drawback is the patient’s high cylinder would require correction postoperatively.
I generally decide between a toric monofocal lens and a small-aperture IOL based on the potential aberrometry measurements. In healthy eyes, my cutoff for the former lens type is around 0.5 µm of corneal HOAs. If both of a patient’s eyes have a high magnitude of corneal HOAs, I consider bilateral implantation of a small-aperture lens.
WHAT I DID: KARL G. STONECIPHER, MD
After a detailed discussion of his options, the patient elected to receive a small-aperture lens in both eyes. The procedures were performed 1 week apart.
Once his refraction stabilized after surgery, the patient’s uncorrected distance visual acuity was 20/40 OU, 20/60 OD, and 20/50 OS. His uncorrected near visual acuity was 20/40 OU. Manifest refraction did not improve his vision.
Although we have discussed his possible use of scleral contact lenses, the patient is currently satisfied with his functional UCVA.
1. Lisa C, Zaldivar R, Fernández-Vega Cueto A, Sanchez-Avila RM, Madrid-Costa D, Alfonso JF. Clinical outcomes of sequential intrastromal corneal ring segments and an extended range of vision intraocular lens implantation in patients with keratoconus and cataract. J Ophthalmol. 2018;2018:8328134.
