Demographics, co-morbidities, medication use, eye symptoms and surgical information, grouped by the presence or absence of pain 1 day postsurgery (defined as NRS≥3 at its worst since surgery)
| No pain (NRS<3) (n=83) | Pain (NRS ≥3) (n=168) | P value | |
| Demographics and exposures | |||
| Age, mean years±SD | 36.3±7.9 | 33.7±8.0 | 0.02 |
| Gender, % female (n) | 60% (50) | 60% (100) | 0.91 |
| Race, % White (n) | 82% (68) | 80% (135) | 0.97 |
| % Black (n) | 2% (2) | 4% (6) | |
| % Asian (n) | 12% (10) | 9% (15) | |
| % Other (n) | 4% (3) | 7% (12) | |
| Ethnicity, % Hispanic (n) | 17% (14) | 45% (75) | <0.001 |
| Smoker, % current (n) | 13% (11) | 10% (17) | 0.47 |
| Smoker, % former (n) | 24% (20) | 23% (38) | 0.81 |
| Secondhand smoke exposure, % (n) | 11% (9) | 4% (7) | 0.04 |
| Systemic co-morbidities | |||
| Diabetes, % (n) | 2% (2) | 1% (2) | 0.60 |
| Hypertension, % (n) | 8% (7) | 5% (9) | 0.35 |
| Sleep apnoea, % (n) | 8% (7) | 2% (4) | 0.045 |
| CPAP use, % (n) | 5% (4) | 2% (3) | 0.22 |
| Migraine or headache, % (n) | 11% (9) | 15% (25) | 0.38 |
| Rosacea, % (n) | 5% (4) | 4% (6) | 0.73 |
| Fibromyalgia, % (n) | 4% (3) | 0% (0) | 0.04 |
| Non-ocular pain condition, % (n) | 16% (13) | 10% (16) | 0.15 |
| Depression, PHQ-9, mean±SD | 2.7±3.5 | 2.4±3.3 | 0.48 |
| Depression (PHQ-9≥5), % (n) | 23% (19) | 18% (30) | 0.34 |
| Non-ocular allergies, % (n) | 43% (36) | 35% (59) | 0.21 |
| Ocular co-morbidities | |||
| Ocular allergies, % (n) | 19% (16) | 13% (21) | 0.15 |
| Contact lens wear, % (n) | 75% (62) | 74% (124) | 0.88 |
| Artificial tear use, % (n) | 13% (11) | 19% (31) | 0.30 |
| Oral medications | |||
| Antidepressant, % (n) | 13% (11) | 12% (20) | 0.76 |
| Anxiolytic, % (n) | 17% (14) | 13% (21) | 0.35 |
| Anti-allergy medication, % (n) | 16% (13) | 8% (14) | 0.08 |
| ADHD medication, % (n) | 12% (10) | 8% (13) | 0.27 |
| Pre-surgery ocular symptoms | |||
| DEQ5, mean±SD | 3.3±3.0 | 3.5±3.2 | 0.59 |
| OSDI, mean±SD | 5.8±8.0 | 7.1±10.2 | 0.30 |
| Worst pain over past week, mean±SD, range 0–10 | 0.4±1.0 | 0.5±1.1 | 0.54 |
| Worst pain over past week≥3, % (n) | 5% (4) | 5% (9) | 1.00 |
| Pain immediately before anaesthesia, mean±SD, range 0–10 | 0.06±0.3 | 0.2±0.7 | 0.006 |
| Pain 30 s after anaesthesia, mean±SD, range 0–10 | 0.04±0.2 | 0.1±0.4 | 0.03 |
| NPSI-Eye, mean±SD, range 0–100 | 0.9±1.6 | 1.0±2.5 | 0.58 |
| Pre-surgery tear production | |||
| Schirmer, mean mm at 5 min, mean±SD | 16.7±10.4 | 17.2±11.1 | 0.71 |
| Schirmer<5 mm at 5 min, % (n) | 12% (10) | 15% (25) | 0.54 |
| Pre-surgery refractive corrections | |||
| Best corrected-visual acuity 20/20 or better, % (n) | 84% (68) | 87% (146) | 0.53 |
| Manifest refraction spherical equivalent, mean±SD | −3.6±2.2 | −3.4±2.1 | 0.39 |
| Manifest refraction cylinder, mean±SD | 0.71±0.63 | 0.81±0.80 | 0.30 |
| Surgical considerations | |||
| LASIK, % (n) | 88% (73) | 89% (149) | 0.86 |
| PRK, % (n) | 12% (10) | 11% (19) | 0.86 |
| Flap depth, mean µm±SD (range), LASIK only | 113.7±7.05 (110-130) | 120.6±8.96 (105-130) | <0.001 |
| Surgical location, Miami, % (n) | 27% (22) | 64% (107) | <0.001 |
| Hyperopic correction | 4% (3) | 3% (5) | 0.72 |
CPAP, continuous positive airway pressure; DEQ5, 5 item Dry Eye Questionnaires; LASIK, laser assisted in situ keratomileusis; NPSI-Eye, Neuropathic Pain Symptoms Inventory-Modified for the Eye; NRS, numerical rating scale; OSDI, Ocular Surface Disease Index; PHQ-9, Patient Health Questionnaire.