1：Experimental Design and Method Selection:

A cross-sectional study design was used to compare IOP measurements with red-free light without fluorescein versus cobalt blue light with fluorescein using the same Goldmann applanation tonometer. The rationale was to assess if red-free light could provide accurate IOP measurements without the need for fluorescein, potentially simplifying the procedure and avoiding issues related to fluorescein concentration.

2：Sample Selection and Data Sources:

The study involved 500 eyes from 250 consecutive patients at the Ophthalmology Outpatient Clinic, Suez Canal University Hospital. Patients with dry eyes (Schirmer test <10 mm), corneal opacities, scarring, edema, previous corneal surgery, or astigmatism above 3 D were excluded to ensure sample integrity.

3：List of Experimental Equipment and Materials:

Goldmann applanation tonometer mounted on a Haag-Streit slit-lamp (Nidek, Tokyo, Japan), red-free light filter, cobalt blue light filter, topical benoxinate hydrochloride eyedrops (Eipico, Tenth of Ramadan City, Egypt), sodium fluorescein strips (Glo Strips, Eye Care and Cure, Tucson, Arizona, USA), Schirmer test strips, and statistical software (Microsoft Excel and SPSS version 16.0).

4：0). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: After applying topical anesthetic, IOP was measured first with red-free light without fluorescein, averaging three measurements. Then, after applying a fluorescein strip, IOP was measured with cobalt blue light, again averaging three measurements. Two observers performed measurements in a masked and alternated manner to avoid bias, with intraobserver agreement tested beforehand (kappa=0.92).

5：92). Data Analysis Methods:

5. Data Analysis Methods: Data were analyzed using student t-test to compare mean IOP values, with p<0.05 considered significant. Agreement between methods was assessed using Bland-Altman analysis to determine limits of agreement and bias.