Measurement of the Refractive Index of Soft Contact Lenses During Wear
Bibliographic record
Abstract
PURPOSE: To determine whether the refractive index (RI) of a soft contact lens can be evaluated using refractometry while the lens remains on the eye and to compare this with more traditional ex vivo RI measurements. METHODS: A slitlamp apparatus was modified to incorporate a customized Atago hand refractometer. With a double-masked study design, nine adapted symptomatic soft contact lens wearers wore a contact lens in each eye (lotrafilcon B and etafilcon A) in a randomized order. In vivo RI was determined from the relative Brix scale measurements immediately after lens insertion and after 1 and 10 hr of lens wear. Ex vivo refractometry was performed after 10 hr of lens wear for comparison. Means +/- standard errors of the means are reported. RESULTS: In vivo RI values at baseline were 1.422 +/- 0.0004 (lotrafilcon B) and 1.405 +/- 0.0021 (etafilcon A); after 1 hr of lens wear, values were 1.423 +/- 0.0006 and 1.408 +/- 0.0007, respectively; and after 10 hr of lens wear, values were 1.424 +/- 0.0004 and 1.411 +/- 0.0010, respectively. Ex vivo RI values at the end of the 10 hr wearing period were 1.424 +/- 0.0003 (lotrafilcon B) and 1.412 +/- 0.0017 (etafilcon A). The change in in vivo RI across the day was statistically significant for the etafilcon A lens (repeated-measures analysis of variance, P<0.01) but not for the lotrafilcon B lens (P>0.05). CONCLUSIONS: This novel adaptation of refractometry was able to measure the RI of soft contact lenses during wear (without lens removal). End of day RI measurements using in vivo and ex vivo refractometry were comparable with each other. Future work is required to determine whether this in vivo method can improve our understanding of the relationships between soft contact lens RI, hydration, on-eye lens performance, and symptomology.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".