2013 Congress of the European Society of Cataract and Refractive Surgeons
Noted by Dr. Ken Hoffer some 30 years ago, short eyes with high hyperopia continue to present a special challenge with regard to biometry and IOL calculation, said Wolfgang Haigis, MS, PhD, at the 2013 Congress of the European Society of Cataract and Refractive Surgeons. “The short eye is a very unforgiving eye,” Dr. Haigis said.
Measurement errors, IOL manufacturing tolerances and uncertainties regarding effective lens position all affect short eyes much more than medium or long eyes. But Dr. Haigis has a few recommendations to help.
Ultrasound axial length determination is frequently more difficult compared to normal eyes because these eyes have distorted geometries which make it difficult to get a good-quality A-scan. As a result, Dr. Haigis recommends optical biometry.
Another way short eyes are penalized is that they are much more sensitive to minor displacements. While a change of 1 mm in a long eye will cause a change of only 0.6 D in refraction, a 1 mm shift will translate into 1.9 D of refraction in a short eye.
Selection of a suitable IOL calculation formula is critical in these eyes. Dr. Haigis recommends the following formulae: Haigis, HofferQ and Holladay-2 with optimized IOL constants.
In cases of extreme hyperopia, a custom-made IOL may be the best option, Dr. Haigis said. The typical upper limits of available IOL powers end typically around 30 to 35 D. While creating a higher power can be achieved through piggy back lenses, Dr. Haigis notes that some German manufacturers will custom-make lenses with refractive powers as high as 75 D (Morcher, Carl Zeiss, HumanOptics).
Lastly, when performing refractive surgery in short eyes with high hyperopia, Dr. Haigis recommends use of large optical zones, don’t correct more than 4 D of refractive error and avoid creating too much change in corneal asphericity.
Graham Barrett, clinical professor, Lions Eye Institute and Sir Charles Gardner Hospital, Perth, Australia, adds that refractive lens exchange is a good option in high hyperopes aged 40 and older, while LASIK may be better for patients in their 20s.
Dr. Barrett says the risk of retinal detachment from refractive lens exchange in these patients is lower compared with high myopes undergoing the same procedure. Additionally, lens exchange can also lower the risk of angle closure, and it’s a relatively predictable procedure compared with LASIK.
He offers a few surgical tips in these challenging eyes: Use Healon 5 to maintain the chamber, a needle rhexis, and maintain perfect fluidics to avoid leakage. He also uses a coaxial I/A.
For two weeks postop, he prescribes oral steroids and cyclopligia to reduce the risk of choroidal infusion or possibly malignant glaucoma.
Stressing again the importance of proper IOL calculations, he said that 85 percent of his patients are within .5 D of expected outcome after surgery and had deeper anterior chambers with IOP under control.
“If you are aware of complications, you can achieve excellent outcomes with refractive lens exchange in high hyperopes,” Dr. Barrett said.