Case Reports

IOL power calculation: going beyond the available evidence

Case Report Details

First Author: M.Raimundo PORTUGAL

Co Author(s):    M. Quadrado   J. Murta                 

Abstract Details

Purpose:

Complex refractive cases require ophthalmologists to go beyond available evidence, since the literature does not currently cover intraocular lens (IOL) power calculations in scenarios where multiple surgeries and complications (such as ectasia) are compounded in the same eye.

Setting:

Private ophthalmology practice.

Report of Case:

We describe the case of a 57-year-old man referred to our practice for decreasing visual acuity in the right eye (RE) following bilateral LASIK in another institution one year before. Corneal tomography was remarkable for ectasia RE; despite some suspect features (small inferior steepening and thinning) there was no clear ectasia in the left eye (LE). Best-corrected visual acuity on the RE was 20/70 with plano (-5.50 x 70º). Due to progression on close serial examination we proposed corneal crosslinking (Dresden protocol) RE. After 6 months BCVA was 20/30 with -1.75 (-4.50 70º). One intrastromal corneal ring segment was then implanted for refractive purposes and, 6 months after, UCVA was 20/25. Five years after, the patient presented with decreased visual acuity RE, BCVA RE 20/50 -4.50 (-3.00 20º), LE 20/25 (+0.75 20º). Slit lamp examination demonstrated a visually significant nuclear and posterior subcapsular cataract in the RE. Corneal tomography showed no signs of progression in the RE; there was neither clear ectasia nor progression in serial examinations of the LE. We proposed RE cataract surgery. For IOL power calculation we assumed a dominant phenotype of corneal ectasia and chose a neutral asphericity lens (Alcon SA60AT). Barrett Universal II using Pentacam derived equivalent K-readings (4.5 mm) suggested a +12.50 IOL power for a predicted -1.44 SE. Raytracing assisted IOL power calculation (PhacoOptics®) suggested a +12.50 IOL power for a predicted -1.36 SE. While a final intra-operative aberrometry reading was not obtainable, some discrete measurements suggested a +12.50 IOL power for a -0.25 target. An Alcon SA60AT +13.00D IOL was ultimately implanted. One-month postoperatively RE UCVA was 20/40, BCVA 20/25 with -2.00 30º (SE -1.00D) and the patient was very satisfied.

Conclusion/Take Home Message:

Raytracing assisted IOL calculation, total cornea evaluation combined with modern formulas and intraoperative aberrometry are modern strategies that may be helpful in cases of compound corneal refractive surgeries and ectasia. Combination of different methods is advisable, with a myopic target in mind and adequate patient expectation management.

Financial Disclosure:

None