Hyperosmolarity of ocular surface may impact cataract surgery planning

Take-home:

A recent study demonstrates the importance of evaluating osmolarity during cataract surgical planning in order to ensure that presurgical keratometry readings are not compromised by hyperosmolarity of the ocular surface.

By Nancy Groves; Reviewed by Eric D. Donnenfeld, MD

Rockville Centre, NY-New study findings underscore the importance of evaluating osmolarity during surgical planning.

The study demonstrated that hyperosmolar patients had a wider variation in keratometry calculations between visits relative to the normal osmolar group. In the hyperosmolar group, 16% of hyperosmolar eyes had more than 1 D of change in K cylinder values between the first and second visit.

The purpose of the study, sponsored by TearLab, was to investigate the link between dry eye and variance in presurgical calculations in cataract and refractive surgery patients.

Doyle Stulting, MD, of the Woolfson Eye Institute, Atlanta, presented preliminary findings from the cataract surgery arm of the study, at the 2014 meeting of the European Society of Cataract and Refractive Surgeons. Discussing the latest results, Eric D. Donnenfeld, MD, an investigator on the refractive arm of the study, explained that investigators obtained keratometry cylinder and osmolarity data on patients planning routine cataract surgery at two preoperative visits. The study enrolled 67 patients between the two arms.

The change between visits in keratometry cylinder among hyperosmolar and normal osmolar subjects was analyzed, along with the correlation between change in osmolarity versus the change in keratometry cylinder. The difference between eyes in osmolarity between the hyperosmolar and normal osmolar subjects was also evaluated, said Dr. Donnenfeld, founding partner of Ophthalmic Consultants of Long Island and Connecticut and clinical professor of ophthalmology, New York University Medical Center, New York.

The results showed that the hyperosmolar group demonstrated wider variation in keratometry cylinder between visits (p < 0.001) relative to normal eyes. In normal osmolar subjects (n = 21), the change in keratometry cylinder between visits was 0.38 ± 0.26 D (OD) and 0.39 ± 0.23 D (OS); in hyperosmolar subjects (n = 46), the change was 0.58 ± 0.46 D (OD) and 0.61 ± 0.65 D (OS).

In the normal osmolar patients, 29% of eyes had a difference between the first and second visits in keratometry cylinder values between 0.5 and 1 D and none had a reading ≥1 D. In contrast, 21% of the eyes of hyperosmolar patients had a measurement between 0.5 and 1.0 D but 16% had more than 1 D of change.

The change in osmolarity between visits was 15.16±9.64 (OD) and 14.02±11.93 (OS) in the hyperosmolar eyes while only 6.27±4.45 (OD) and 6.77±6.96 (OS) in normal osmolar eyes. The change in osmolarity was not significantly correlated to change in keratometry cylinder.

“The take-home message was that by optimizing the ocular surface, you get more a reliable keratometry for IOL selection, and with a reliable keratometry it’s more likely that you’ll achieve a better refractive outcome,” Dr. Donnenfeld said.

He emphasized that pre-treatment of dry eye improves surgical results.

“The ocular surface is the most important refracting surface of the eye, and with an abnormal ocular surface, which is predicted by osmolarity, you can expect to have suboptimal results because the surface of the cornea creates higher-order aberrations and loss of quality of vision in patients who have irregular corneas,” Dr. Donnenfeld said. “It makes it more difficult to predict the correct IOL power and to effectively treat cylinder with toric IOLs or limbal relaxing incisions.”

Eric D. Donnenfeld, MD

E: ericdonnenfeld@gmail.com

This article was adapted from Dr. Donnenfeld’s review of findings from both arms at the 2014 meeting of the American Academy of Ophthalmology. The study results will be submitted for publication to the Journal of Cataract and Refractive Surgery.