Biometry: What You Need To Know

Biometry: What You Need To Know
Leigh Spielberg
Leigh Spielberg
Published: Sunday, September 6, 2015
“I often hear surgeons say, ‘apart from the very short and long eyes, I have no biometry problems’,” said Nino Hirnschall MD, of the Vienna Institute for Research in Ocular Surgery, Austria, speaking at the ESCRS Young Ophthalmologists Programme. “But I think there’s always room to improve,” he added. The main source of error in intraocular lens (IOL) power calculation is the postoperative anterior chamber depth, which largely determines the effective IOL position. “This is responsible for about 35 per cent of errors,” Dr Hirnschall told the delegates in attendance. He added that the selection of which modern IOL formula gives the best result has been hotly debated. “Optimising the IOL constants for each IOL model for the method of axial length measurement, for example optical or acoustic, has a much greater impact on the predictability of the refractive outcome than choosing between modern IOL formulae,” he said. Dr Hirnschall reported that the percentage of eyes within +/-1D of the target refraction can improve by up to 20 per cent with optimisation. Operating the second eye offers a chance to “learn” from the first eye regarding IOL power selection. However, he cautioned against the temptation to correct for the full refractive error of the first eye. “The two eyes are not twins,” said Dr Hirnschall. “Studies have shown that we should only correct for 40 per cent of the first eye’s refractive error.” “With-the-rule astigmatism is often overstated, and against-the-rule understated, by preoperative measurements, so it’s important to use different devices to measure the cornea,” he said, regarding toric IOLs. “Post-refractive surgery eyes remain the ultimate challenge,” added Dr Hirnschall.
Latest Articles
Simulators Benefit Surgeons and Patients

Helping young surgeons build confidence and expertise.

Read more...

How Many Surgeries Equal Surgical Proficiency?

Internet, labs, simulators, and assisting surgery all contribute.

Read more...

Improving Clinical Management for nAMD and DME

Global survey data identify barriers and opportunities.

Read more...

Are Postoperative Topical Antibiotic Drops Still Needed?

Cataract surgeons debate the benefits of intracameral cefuroxime prophylaxis.

Read more...

Emerging Technology for Detecting Subclinical Keratoconus

Brillouin microscopy shows promise in clinical studies.

Read more...

Knowing Iris Repair: Modified Trifold Technique

Part eight of our series covers the modified trifold technique for large iris defects.

Read more...

It’s All About Biomechanics!

Increasing the pool of patients eligible for refractive surgery.

Read more...

Uncovering More Safe and Quick Options

Different strategies, such as PresbyLASIK, can offer presbyopes good outcomes.

Read more...

Topography-Guided PRK for Keratoconus

Improving visual acuity in patients with keratoconus.

Read more...

Defining AMD Treatment Protocol

Treatments trending to fewer injections for better results.

Read more...