Role of percent peripheral tissue ablated on refractive outcomes following hyperopic LASIK.
OBJECTIVE
To determine the effect of hyperopic laser in situ keratomileusis (H-LASIK) on corneal integrity, by investigating relationships between proportionate corneal tissue ablated and refractive outcomes at 3 months.


METHODS
18 eyes of 18 subjects treated with H-LASIK by Technolas 217c Excimer Laser were included in the study. Orbscan II Topography System was used to determine corneal volume and pachymetry 3mm temporally (3T). The volume of corneal tissue ablated was determined from the laser nomogram. Univariate associations between age, treatment, corneal volume, overall proportion of tissue removed, proportion of tissue removed at 3T, residual bed thickness at 3T and refractive outcomes 3 months post-LASIK were examined and independent factors associated with refractive outcomes determined using linear regression models.


RESULTS
At 3 months post-LASIK, the mean difference to expected refractive outcome was -0.20 ± 0.64 (Range -2.00 to +1.00). In univariate analysis, difference to expected refractive outcome was associated with proportion of tissue removed at 3T (P<0.01, r = -0.605) and total number of pulses (P< 0.05, r = -0.574). In multivariable analysis, difference to expected refractive outcome was associated with the proportion of tissue removed at 3T only.


CONCLUSIONS
Subjects undergoing H-LASIK, may present as either over or under-corrected at 3 months. The proportion of tissue removed at 3T was the single significant determinant of this outcome, suggesting unexpected biomechanical alterations resulting in corneal steepening. Future hyperopic LASIK procedures could consider proportionate volume of corneal tissue removed at 3T in addition to laser nomograms to achieve improved refractive outcomes.
School of Optometry and Vision Science, Faculty of Science, UNSW Australia, Kensington, New South Wales, Australia.
George
http://orcid.org/0000-0002-6743-3850
G
Fatseas
School of Optometry and Vision Science, Faculty of Science, UNSW Australia, Kensington, New South Wales, Australia.
Fiona
F
Stapleton
Vision Eye Institute, Bondi Junction, New South Wales, Australia.
Patrick
P
Versace
D000328:Adult; D003315:Cornea / Q000502:physiology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000601:surgery*; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D011446:Prospective Studies; D012029:Refraction, Ocular; D016896:Treatment Outcome; D014787:Vision Tests; D014792:Visual Acuity