When indoors I have no frown lines but outside in sunlight they are so strong & deep, it doesn’t make sense?

I don’t recommend fillers to correct frown lines. With regular Botox treatments your frown lines(even outdoors) should gradually improve over time.

The phenomenon you're experiencing is quite common and can be attributed to how sunlight affects the visibility of lines and wrinkles on the skin. Here are some insights and considerations:

Lighting Effects: Sunlight is much harsher and more direct than indoor lighting, which can cast shadows and emphasize even minor lines and wrinkles that are not as visible under softer, diffused indoor light.

Squinting in Sunlight: When you're outdoors, especially in bright sunlight, you may unconsciously squint or furrow your brow to shield your eyes from the light, which can temporarily accentuate frown lines. Wearing sunglasses can help reduce squinting and prevent further deepening of these lines.

Botox Effects: Botox works by temporarily paralyzing the muscles responsible for frowning, which reduces the appearance of lines. However, if the lines are still noticeable in sunlight, it might indicate that the Botox effect is wearing off or that deeper, static lines (lines that are present even without muscle movement) are present.

Consider Fillers: If the lines are static and persist despite Botox treatment, dermal fillers might be a suitable option to smooth out these deeper lines. Fillers add volume and can help to diminish the appearance of deep-set wrinkles.

Consult with Your Dermatologist: Before deciding on additional treatments, it’s important to consult with your dermatologist or cosmetic professional. They can assess your skin and recommend the best course of action based on your specific needs.

In summary, while Botox is effective for dynamic lines, fillers might be considered for deeper static lines. A professional evaluation will help determine the most appropriate treatment for achieving your desired results.

If you still are able to animate and make frown lines you may benefit from a Botox touch up. As far as the difference between indoors and outdoors, the lines may appear more noticeable in bright light. Return to your injector for an evaluation and possible touch up.