CASE PRESENTATION
An 80-year-old man with advanced keratoconus presents for a cataract surgery evaluation. The patient has a long history of scleral contact lens wear, which currently correct the distance visual acuity in each eye. He wears over-the-counter readers when performing near tasks.
The patient’s medical history is significant for type 2 diabetes and hypertension. He is allergic to povidone-iodine, iodine, shellfish, and several antibiotics. He reports increasing difficulty with glare while driving at night. His BCVA with scleral lenses is 20/60-2 OD and 20/40 OS. With glare testing, the patient’s vision is light perception OU. His BSCVA is 20/200 OU with a manifest refraction of -9.75 -1.75 x 015º OD and -6.25 -1.75 x 015º OS.
Biometry (Argos, Alcon) is unreliable despite multiple attempts. Manual keratometry proves to be impossible because the extreme readings exceed the machine’s limits. IOL calculations using keratometry (K) readings obtained with the Argos and the Pentacam (Oculus Optikgeräte) and processed through the Veracity Surgery Planner (Carl Zeiss Meditec) recommend a wide range of lenses (Figures 1 and 2). According to the calculations, the lowest-powered IC-8 Apthera lens (Bausch + Lomb) available would leave him highly myopic.
Figure 1. Calculations with the Veracity Surgery Planner.
Figure 2. Topography using the relative scale.
The patient’s hobbies include playing music (using both sheet music and a tablet computer), working at a computer, and driving. He is comfortable with the prospect of continued scleral lens wear postoperatively but would like to maximize his unaided visual potential when he is not wearing scleral lenses, even if contact lenses and glasses remain necessary. He is willing to pay out of pocket for advanced lens technology to achieve the best possible outcome. He has never tried monovision and is strongly motivated to be less dependent on glasses and contact lenses.
When biometry is unreliable, which K values do you trust the most? Should the wearing of scleral lenses, like rigid gas permeable contact lenses, be discontinued before keratometry? Which IOL formula do you recommend for patients with highly irregular corneas? If you would perform intraoperative aberrometry (ORA System, Alcon), which K values would you enter? Which IOL would you suggest? Would you recommend piggyback IOLs? If so, would you plan to implant them in a single procedure, or would you use a staged approach? If the latter, which lens would you implant first, and what would the refractive target be?
— Case prepared by Neda Nikpoor, MD
BEERAN MEGHPARA, MD
Tomography shows a cone localized near the central cornea instead of the inferior steepening pattern more typically observed in keratoconus. The patient therefore has less astigmatism than is usual with keratoconus.
The Argos was unable to acquire K values, so I would rely on the Pentacam K readings. Even when there is a central cone, central corneal power tends to be overestimated in keratoconic eyes. I would therefore target a substantial amount of postoperative myopia. I would perform the IOL power calculations with the Kane keratoconus formula, which accounts for the overestimated central corneal power and selects a higher-powered IOL than conventional formulas.
Given their inherently high negative spherical aberration, my preferred IOLs for patients with keratoconic corneas are the enVista (model MX60, Bausch + Lomb) and the Sensar (model AR40, Johnson & Johnson Vision). The former induces zero spherical aberration, whereas the latter induces a small amount of positive spherical aberration.
Due to the high K values, even the lowest-powered (0.00 D) MX60 lens would result in significant postoperative myopia. Because the patient desires some spectacle independence, I would use the Kane keratoconus formula to target approximately -2.00 D of residual myopia. To achieve this aim, a negative-powered IOL would be necessary. Fortunately, the AR40M is available in powers as low as -10.00 D. With mild residual myopia, the patient might experience functional uncorrected near and intermediate visual acuity. Additionally, the corneal spherical aberration might enhance his depth of focus, potentially allowing him to read a computer screen and sheet music without additional correction.
It would be essential to counsel the patient that IOL power calculations for individuals with keratoconus, particularly advanced disease, are less predictable than for healthy eyes. In the event of a refractive surprise, the patient would not be a candidate for corneal refractive surgery, but an IOL exchange would be an option. Alternatively, if his postoperative BSCVA is satisfactory, a Light Adjustable Lens (LAL; RxSight) could be implanted as a piggyback, which might also address any residual astigmatism. The LAL+ model, which is available in negative powers, might be required, but it is designed primarily for use in eyes with regular corneas. The use of an LAL+ in a patient with keratoconus might therefore diminish their quality of vision.
WILLIAM B. TRATTLER, MD
Planning cataract surgery on an 80-year-old patient with advanced keratoconus is a challenge. It would be helpful to know whether his keratoconus is stable or progressive.1 Even if there is evidence of keratoconic progression, the rate of progression among patients in their 70s and 80s typically is not rapid. A paper presented at the ASCRS Annual Meeting this year reported that 40 of 105 eyes (38.1%) of patients who were 40 years of age and older experienced progression but that the average rate of progression was lower than in patients who were less than 40 years of age.1 I would therefore focus on cataract removal, educate the patient on the importance of avoiding eye rubbing, and schedule him for a postoperative visit in 2 to 3 months to discuss CXL.
The most difficult part of cataract surgery on an individual with advanced keratoconus is choosing the IOL power. Research suggests that patients should discontinue wearing scleral lenses for 3 to 7 days to maximize the accuracy of preoperative corneal measurements.2 Of course, when the K readings are this steep (Kmax around 65.00 D OU), a slightly different K value is unlikely to make a significant difference in the final IOL power selection.
In situations like this, I typically perform calculations with both the Kane keratoconus and the Barrett True-K keratoconus formulas. Because the patient wears scleral lenses, I would favor a neutral aspheric monofocal IOL such as the enVista (model MX60E). Entering the K readings obtained with the Pentacam into the Kane keratoconus formula indicates that implanting an enVista monofocal IOL with a plano power should achieve a postoperative refraction of -4.72 D OD and -4.84 D OS. Although the implantation of a negative-powered IOL might achieve an outcome closer to plano, it also might leave the eye hyperopic.
Delayed sequential bilateral cataract surgery would be my approach. The patient would continue to wear a scleral contact lens on the unoperated eye. One month after surgery on the first eye, his refraction and level of satisfaction would be assessed. If he is unhappy with his result, the postoperative refraction would be used to determine whether an IOL exchange or piggyback IOL procedure is appropriate. If he is satisfied with the results of the cataract procedure, a scleral contact lens fitting would be completed for the pseudophakic eye, and then the second eye would undergo surgery.
WHAT I DID: NEDA NIKPOOR, MD
As the panelists note, the primary challenge of this case is the IOL calculation. Owing to the wide range of recommended powers with different devices and formulas, an LAL was initially chosen to allow fine-tuning of the postoperative refraction in each eye.
The Pentacam K readings and Veracity Surgery Planner were used for the IOL calculation. Unfortunately, even the lowest-powered LAL available would have left the patient with moderate myopia. For this reason, an LAL+, which is available in powers as low as -2.00 D, was selected. I generally reserve the LAL+ for individuals with healthy virgin corneas, but my desire to correct the patient’s sphere and cylinder outweighed my concern about the higher amount of negative spherical aberration with this lens. Furthermore, I reasoned that the patient could expect to achieve good visual acuity with scleral contact lenses.
The small chance of a poor postoperative quality of vision and possible need for an IOL exchange were discussed with the patient. We also had a long conversation about his visual potential and he understood that it would be greatest with bitoric scleral contact lenses. He requested a distance target, and delayed sequential bilateral cataract surgery was planned.
A -2.00 D LAL+ was implanted in the right eye. One week after surgery, the patient’s UCVA was 20/100-1 OD, and his manifest refraction was +1.75 -2.00 x 120º = 20/60 OD. His subjective quality of vision had improved dramatically, and he underwent surgery with the same IOL power and distance target in the second eye.
Before the postoperative light treatments were performed, the patient’s UCVA was 20/100-1 and J7 OD, 20/100-2 and J7 OS, and 20/80+2 and J5 OU. Refraction was extremely difficult due to the LAL’s inherent range of vision and the complex corneas. After multiple attempts, the most accurate refraction seemed to be -5.00 -1.00 x 180º = 20/40-2 OD and -3.00 -2.75 = 20/50+1 OS. A refraction of -5.00 D and a target of -2.00 D were programmed into the light delivery device for the right eye.
One week after the light treatment of the right eye, the patient’s UCVA had increased by 1 line, and he reported a subjective improvement in vision. I explained that an emmetropic outcome was unlikely, and he chose a refractive target of -2.00 D OU. Because it was clear that he would need to wear scleral contact lenses when driving, the light treatments corrected sphere but not cylinder to make the postoperative lens fitting less complicated.
After the light treatments were complete, the patient’s manifest refraction was -1.00 -1.50 x 085º = 20/60-2 OD and -1.00 D sphere = 20/50+2 OS. At the final visit, his UCVA was 20/70-2 and J5 OD, 20/70-1 and J7 OS, and 20/40-2 and J5 OU. The patient was happy with his outcome and able to perform many activities of daily living other than driving without wearing spectacles or contact lenses.
1. Gil A, Kantor N, Trattler W, Yazji A, Allee L, Shiwlochan D, Spies D. Progressive keratoconus in older patients who delayed corneal cross-linking treatment. Paper presented at: ASCRS Annual Meeting 2025; April 27, 2025; Los Angeles, CA.
2. Soeters N, Visser ES, Imhof SM, Tahzib NG. Scleral lens influence on corneal curvature and pachymetry in keratoconus patients. Cont Lens Anterior Eye. 2015;38(4):294-297.
