CORRECTION SCREENING

Adding tear osmolarity testing to the routine dry eye screening protocol will allow refractive surgeons to minimise dry eyeassociated problems following refractive laser surgery, Richard Corkin MD told a session of the XXXI ESCRS Congress in Amsterdam. “Our analyses demonstrate that the results of a Schirmer’s I test, which is widely used as a standard screening test for refractive surgery, correlate poorly with the presence of dry eye. Tear film Osmolarity when used as a screening test, has higher sensitivity and specificity in identifying patients with this condition,” said Dr Corkin, consultant ophthalmic surgeon, UPMC Beacon Hospital and co-director at the Wellington Eye Clinic, Dublin.

The study included 111eyes of 58 consecutive patients presenting for laser refractive surgery in January 2012, of which 91 went on to surgery with either LASIK (39 eyes) or LASEK (52 eyes). The preoperative assessments included a Schirmer’s I test, tear osmolarity (TearLab) and examination for superficial punctate keratitis (SPK). Preoperative evaluations demonstrated dry eye symptoms were absent in 58 per cent of all screened eyes, 73 per cent had no evidence of SPK. Despite this, a very low Schirmer’s I result ≤5.0mm was present in 34 per cent of the 111 screened eyes. According to eligibility criteria in use at the time at the Wellington Clinic, these patients would have been considered unsuitable for surgery, Dr Corkin explained.

Tear osmolarity was >308 mOsm/L in 38 per cent of the 111 eyes and >318 mOsm/L in 22.5 per cent (>318 mOsm/L would be considered dry). There was no correlation demonstrated between the preoperative Schirmer’s I result and tear osmolarity, Dr Corkin reported. Twenty-six (68 per cent) eyes with a low Schirmer’s I ≤5mm went on to have LASEK (20 eyes) or LASIK (six eyes). Eight (31 per cent) of those 26 eyes (with Schirmer’s<5) had tear osmolarity <308 mOsm/L and 21 eyes (81 per cent) had a tear osmolarity <318 mOsm/L.

Dr Corkin said that all 26 eyes had uncomplicated surgery with excellent visual outcomes. None developed significant dry eye symptoms postoperatively, and while two-thirds of the LASEK eyes had some SPK after surgery, it was mostly grade 1. In the 91 operated eyes, there was a trend for higher preoperative tear osmolarity to correlate with presence of postoperative SPK. He also observed that an increasing number of older patients are now seeking laser refractive surgery. Of the 58 patients included in the study, nearly 25 per cent were older than age 50. “This shift in population demographics of patients seeking laser surgery is adding to concern since older patients are more likely to have dry eye problems and also have higher expectations for outcomes.”

He said that no single modality can be used as a de facto standard to identify dry eye, however, routine Tear Osmolarity testing is standard on all refractive patients at the Wellington Eye Clinic. Decisions to accept candidates for laser vision correction must still be based on a combination of tests along with patient history and clinical findings.

Richard Corkin: r.corkin@wellingtoneyeclinic.com