Scanning laser polarimetry in corneal haze after excimer laser refractive surgery

We evaluate the technique of retinal nerve fiber layer thickness measurement using scanning laser polarimetry in cases of central corneal haze due to photorefractive keratectomy.

Nerve fiber layer thickness was measured using a Nerve Fiber Analyzer II (Laser Diagnostic Technologies, Inc., San Diego, CA, U.S.A.) in eight eyes of eight individuals with mild to pronounced corneal haze owing to earlier excimer laser refractive surgery, and in nine eyes of nine control volunteers.

Neither total and sectorial nerve fiber layer thickness values, nor superior/ inferior quadrant thickness ratio differed in a statistically significant manner between the two groups (unpaired t test, p > 0.05). Reproducibility in the "haze" and control groups was 4.3% and 3.4%, respectively, for mean nerve fiber layer thickness calculated from all quadrants around the disc. The figures were 4.9% and 5.2%, respectively, for the superior quadrant thickness; 8.2% and 8.8%, respectively, for the temporal thickness values; 5.4% and 4.6%, respectively, for the inferior thickness values; and 4.1% and 5.0%, respectively, for the nasal quadrant thickness values. For the superior/inferior quadrant thickness ratio the reproducibility was 4.4% and 6.8%, respectively. None of the corresponding values for reproducibility differed significantly between the two groups (F-test, p > 0.05).

Corneal haze did not cause an artificial increase of the thickness values measured with scanning laser polarimetry and did not diminish the reproducibility of the measurement. The results suggest that scanning laser polarimetry may be a suitable method for the precise measurement of the nerve fiber layer thickness even in eyes with persistent corneal haze after excimer laser refractive surgery.