The purpose of this study is to gain a better understanding of the retinal vascular changes that occur in response to the optical effect of a myopic defocus daily disposable soft contact lens (MDSL) in a group of healthy young myopic adults (18-35 years; myopia -1.00D to -4.00D; all genders). It will also learn about the acceptance of this visual correction modality compared to regular contact lenses.

The main questions to be answered are:

• To evaluate changes in retinal blood flow by visualizing retinal vascular density in the superficial and deep plexus after one week of MDSL wear.
• To evaluate changes in choroidal thickness at the macular level after one week of MDSL wear.
• To evaluate the visual comfort provided by this MDSL design using a questionnaire.

Researchers will compare the MDSL to a daily disposable single vision soft lens (SVSL) used to correct myopia to determine if the addition of a defocus area makes a difference in the retinal response to the visual signal.

Participants will be required to

• Wear both MDSL and SVSL for one week each, in a random order.
• Read letters to measure visual acuity
• Have a deep scan of their retina with an optical coherence tomography (OCT) device
• Rate the comfort and vision provided by both devices using a questionnaire.

Objective:

The aim of this study is to gain a better understanding of the retinal vascular changes that occur in response to the optical effect of a myopic defocus daily disposable contact lens used in another (ongoing) research project (NCT05191134).

The primary objective of the study is to evaluate changes in retinal blood flow by visualizing retinal vascular density in the superficial and deep plexus following one week's wear of a high peripheral add soft contact lens in a population of young myopic adults.

The second objective is to assess changes in choroidal thickness at the macular level after one week's wear of the high peripheral add soft contact lens.

A third objective is to evaluate, through questionnaire, the visual comfort provided by this lens design.

Materials and methods:

25 myopic participants aged between 18 and 35 will be enrolled. Each participant will be randomly fitted with two lenses: a monofocal spherical soft lens (nesofilcon A) for one week and a high-add bifocal soft lens (anti-myopia) for the same duration of time. Participants will be asked to attend three different visits, one week apart.

At visit #1, initial measurements of deep and superficial plexus blood vessel density and choroidal thickness will be taken with an angiographic optical coherence tomograph (OCT-A Triton, Topcon USA).

These measurements will be repeated with other lenses at visit 2 and 3.

The results will be compared. Participants will be asked to evaluate the visual performance of each lens after 1 week of wear through a questionnaire.

Hypothesis: It is expected that one week's wear of the peripheral myopic defocus contact lens will cause an increase in blood vessel density and a thickening of the choroid compared with initial measurements. A decrease in blood vessel density and choroidal thinning is expected after one week's wear of the spherical soft lens (hyperopic defocus), compared with baseline. Both lenses will be well tolerated during daily activities.

Inclusion Criteria:

• · Astigmatism ≤ 1.00 D

  • Myopia between -0.50 and -4.00D
  • Aged between 18 and 35
  • Binocular acuity of 6/6 or better

Exclusion Criteria:

• · Recent intake (< 3 months) of medication affecting blood pressure (e.g. hypotensive, anovulant, CNS stimulant, etc.).

  • Corneal dystrophy or irregularity
  • Use of topical ocular medications
  • Smoking (tobacco or marijuana)
  • Have contraindications to wearing soft contact lenses
  • Being currently under myopia control treatment or had been under control in the last 3 months
  • Being pregnant or breast-feeding
  • History of refractive surgery
  • Addiction to drugs or alcohol

The lenses used in this study are daily disposable. This means that for each type of lens worn, participants will receive 7 lenses of each type. Lenses will be delivered one type at a time for the next week. The lenses will be packaged with a neutral label with a lot number. It is impossible for the participant to know which type this lot number corresponds to. Therefore, they do not know what type of lens they will receive.