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The FLEXI.ENS 55 (methafilcon A) HARRISON Post Refractive Surgery Contact Tens is indicated for daily wear use for the correction of refractive ametropia and specialized use such as atypical ametropia following corneal refractive surgery.

The FIFXLENS 55 (methafilcon A) Harrison Post Refractive Surgery Contact Tens for daily wear is a soft (hydrophilic) contact lens with a spherical or toric hase curve and a spherical front surface. The lens is lathe cut from methafilcon A. a random copolymer of 2-hydroxyethy) methacrylate and methacrylic acid crosslinked with ethylene glycol dimethacrylate. It consists of 45% methafilcon A and 55% water by weight when immersed in normal saline solution buffered with sodium bicarbonate.

The physical properties of the lens are as follows:
Refractive Index: 1.4153
Light Transmittance: greater than 95%T
Water Content: 55%
Oxygen Permeability: Dk=18 X 10-11 at 35 °C (measured by the standard Fatt method)
Specific Gravity: 1.090 g/cc

The FT.FXLENS 55 (methafilcon A) Harrison Post Refractive Surgery Contact Tens for daily wear was developed to improve the visual acuity of those patients who require improved vision after photorefractive keratectomy, radial keratotomy, and other corneal refractive procedures. Other factors taken into consideration were the following:

1. The topographical profile is such that it is difficult to achieve a satisfactory posterior lems surface to cornea alignment with rigid gas permeable contact l enses .
2. Conventional soft (hydrophilic) contact lens designs do not readily align with the visual axis of the PRS or RK eye or supply sufficient masking of the corneal astigmatism.
3. Conventional toric soft (hydrophilic) contact lenses are limited in their ability to provide a stable level of visual acuity on cases of extreme central flattening in conjunction with irregular astigmatism.

The Harrison Post Refractive Surgery Lens differs from the standard spherical FLEXIENS Custom Sphere in that it incorporates a flat central optical zone with a thickness which varies with power (-1.00n will be approximately 0.30mm thick at the center). The size of the optical zone is generally 8.0mm. The peripheral carrier is thinner than most standard soft (hydrophilic) contact lenses, approximately 0.08mm to 0.10mm, to ensure limbal draping which will exhibit the characteristics (on the eye) of a peripheral aspheric design. In some cases the periphery is manufactured with a steeper curvature than the base curve.

The provided text describes a contact lens (FLEXLENS 55 (methafilcon A) HARRISON Post Refractive Surgery Lens) and a clinical study associated with it. However, the document does not explicitly state "acceptance criteria" in a quantitative, measurable format with corresponding "reported device performance." The study described is more of a re-fitting study to compare two versions of the same lens (different water content) on patients who had already been wearing one version.

Based on the information provided, here's an attempt to answer your questions, highlighting where information is not explicitly available:

Acceptance Criteria and Study Details for FLEXLENS 55 (methafilcon A) HARRISON Post Refractive Surgery Lens

1. Table of Acceptance Criteria and Reported Device Performance:

The document does not explicitly define quantitative acceptance criteria for device performance (e.g., minimum visual acuity improvement, maximum complication rate). The clinical study aims to show "no substantial change from one polymer to the other," implying an equivalence or non-inferiority goal rather than specific performance thresholds.

2. Sample Size Used for the Test Set and Data Provenance:

• Sample Size (Clinical Study): 10 patients with 12 eyes.
• Data Provenance: Conducted in Canada. The study was a "refitting" study, meaning patients were already using a previous version of the lens and were then switched to the new version. This suggests a retrospective component (initial fitting data for comparison) and a prospective component (follow-up after refitting with the new lens), though the document describes it as a single "small clinical study."

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications:

• The principal investigator was Keith W. Harrison, FCSSA. His qualifications are listed as FCSSA (Fellow of the Contact Lens Society of America, or similar professional designation, though not explicitly spelled out in the document).
• The document does not specify additional "experts" involved in establishing ground truth for the clinical study beyond the principal investigator who conducted the refitting and follow-up.

4. Adjudication Method for the Test Set:

• The document does not describe an explicit adjudication method (e.g., 2+1, 3+1). The "ground truth" or assessment of "no substantial change" appears to have been determined by the principal investigator, potentially through clinical examination and subjective patient feedback, but specific methods are not detailed.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done:

• No, an MRMC comparative effectiveness study was not done. This was a small clinical study focused on refitting patients with a slightly modified version of an existing product. It did not involve multiple readers assessing cases to determine improvement with AI assistance.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) was done:

• Not applicable. This device is a contact lens, not an AI algorithm. Therefore, a "standalone algorithm performance" study is not relevant.

7. The Type of Ground Truth Used:

• The ground truth for the clinical study appears to be based on clinical assessment by the principal investigator and implied patient experience/outcomes (e.g., "no substantial change from one polymer to the other" in terms of performance). The document does not specify objective metrics like visual acuity charts or detailed patient-reported outcomes, but these would likely have been part of the clinical assessment.

8. The Sample Size for the Training Set:

• Not applicable. This is a contact lens, not a machine learning model. There is no concept of a "training set" in this context. The manufacturing and design process relies on established material science and contact lens design principles.

9. How the Ground Truth for the Training Set Was Established:

• Not applicable, as there is no "training set" for this device. The physical properties (Refractive Index, Light Transmittance, Water Content, Oxygen Permeability, Specific Gravity) are inherent material and design specifications, established through laboratory testing and manufacturing processes for methafilcon A, as referenced in prior 510(k) clearances.

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