Non-diffractive lenses offer alternative in challenging post-corneal refractive surgery cases.
Patients are increasingly expressing their desire for spectacle independence after cataract surgery, especially those who have previously received corneal refractive laser procedures for vision correction. Even with adequate preparation using tools such as the Barrett True-K formula, Haigis-L calculator, Shammas-PL formula or the Masket Method to calculate post-refractive surgery IOL power, residual refractive errors continue to be common.
A history of LASIK and other corneal refractive surgery (CRS) procedures means that the patient will often present with an altered corneal curvature that may include complications such as dry eye and other ocular surface issues, making diffractive multifocal IOLs designed for spectacle independence an unsatisfactory option in most cases. Also, most trifocal IOL options are diffractive, which will result in a loss of contrast sensitivity that will likely fail to meet the patient’s expectation.
Attempting a trifocal IOL implantation in such patients, with their corneal and tear film changes, may increase dysphotopic problems and worsen existing distance visual acuity. In addition, this patient group is more likely to have postoperative refractive errors, and the satisfaction with their visual results is likely to be seriously reduced, if emmetropia is not achieved.
In my efforts to find a solution for these patients, I have discovered that non-diffractive extended depth-of-focus (EDOF) lenses, including the RayOne EMV (Rayner), may offer an alternative in challenging post-CRS cases, especially for patients who desire greater spectacle independence without impacting a high degree of baseline distance vision.
In my experience, the RayOne EMV is a good option in such cases because of its higher tolerance to residual refractive errors and ocular surface disorders. With this lens, it is possible to slightly increase the patient’s central positive spherical aberration in a controlled way that neutralises at the periphery of the optic. This reduces the possibility of outcomes such as poor night vision resulting from dysphotopsia and, additionally, makes the lens tolerant to small degrees of decentration.
For these and other reasons, I now consider this IOL the best option in my patients with a history of corneal refractive surgery. In fact, I find myself using non-diffractive EDOF lenses in most of my standard cases that require a monofocal option
When reviewing IOL options with these patients, I first explain the nature of their ocular challenges, and then communicate as to why a trifocal IOL is not a satisfactory option.
I am especially careful to address their desire for spectacle independence. I explain that their outcomes with a trifocal IOL may involve the need for spectacles due to refractive surprises and the increased risk of dry eye which may make them vulnerable to dysphotopic problems which are common with diffractive lenses.
I aim for a goal of mini or modest monovision with RayOne EMV with -0.75 D to -1.0 D offset, and my patients achieve excellent functional vision, remaining independent from spectacles for most of their daily activities, depending on their habits such as reading on screens or small print books.
I will now describe two patients in a case series of those who have received the RayOne EMV, reviewing baseline ocular health and corneal refractive procedure history, patient expectations with IOL implantation, important considerations and initial outcomes.
A 55-year-old male dentist previously received bilateral Supracor treatment to address presbyopia. He stated that he travels 60 km on a motorcycle between his workplace and home every day.
The patient’s preoperative vision level was 0.3–0.4 D (30–40%), and he had nuclear cataracts in both eyes. The goal for this patient was to avoid creating night-time visual disturbances, while enabling clear near/intermediate vision needed for his daily work.
His postoperative vision increased to 1.0 D in the dominant eye (OS) and to 0.8 D in the non-dominant eye (OD), which was planned with a target refraction of -0.75 D (see Figure). Our patient stated that he did not need glasses in his day-to-day life, and he did not request glasses for near vision.
A 60-year-old female who had LASIK surgery for astigmatism in both eyes presented with posterior subcapsular cataracts. Our patient, who has type 2 diabetes, stated that she had been receiving cyclosporine treatment for dry eyes for 6 years.
Considering the dry eye, corneal refractive laser history, and her metabolic state, which is likely to result in diabetic retinopathy in the future, IOL implantation with mini-monovision was planned.
The visual acuity of the right eye, which had a preoperative vision of 0.2 D, increased to 0.8 D after the operation, and the left eye, with a planned target refraction of -0.75 D and a preoperative vision of 0.3 D, increased to 0.6. Bilateral visual acuity was 0.9 D. Reading glasses with +1.50/+1.00 D power were prescribed for reading small print.