Crepey under eye skin, fine lines when squinting, fine skin. What can be done? Under eye inner corner botox? Dermapen? (photo)

A combination approach will give the most improvement. Fillers, lasers, and microneedling/PRP can improve under the eyes. My patients try to get non surgical treatments to avoid surgery. We use PRP and stem cells there often. I suggest consulting with an expert to develop a treatment plan best suited for your short and long term goals. Best, Dr. Emer

Fractional CO2 laser is an excellent tool for skin rejuvenation in our center in Santa Monica. We use the fractional multi-depth ablative approach to help resurface the skin, recontour acne scars, improve incisional plastic surgery scars, and reduce surface irregularities from skin tone to dark pigmentation. Our approach utilizes a multi-depth approach that targets melanocytes in the epidermis and collagen fibroblasts in the dermis. This approach can be combined with a TCA Peel in a process known as a sapphire peel. Fractional laser is excellent for acne scars and contour scars in the skin. Patients are advised to undergo skin protocols with Melarase creams before and after treatment to help reduce pigmentation. Melarase AM, Melarase PM, and Melapads can seriously improve surface sun damage and UV related pigmentation. After the laser, we expect redness for a few weeks as the skin improves. PRP and Hydrafacial enzyme facials can further improve skin quality after fractional co2.

Best,
Dr. Karamanoukian
Realself100 Surgeon

You will probably get the best results from a combination of treatments.  Based on your explanation of your concerns you may enjoy the ALMI procedure which uses your own tissues to improve volume, tone and texture of the skin.  It is done in the office with no downtime.  You may also consider microneedling or lasers to treat the texture of the skin.  I recommend using sunscreen daily.

Eye bags and crepey skin can be due to many factors including: genetics, aging and lifestyle. Under eye bags can be permanently corrected with surgery or temporarily camouflaged with fillers.There are great non-surgical options to fill in under eye depressions and hollowness. Using dermal fillers, a liquid eyelift can be performed. A dermal filler such as Restylane would be placed in the cheek and tear trough to hide the depression or bag underneath your eye.
Surgery would require a fat-repositioning lower lid blepharoplasty. In this surgical procedure, fat from the eye area is moved into the tear trough depression filling the actual depression. Cost will vary and can be discussed at your consultation.
I hope this helps!

If you are most bothered by the crepey skin under your eyelids that gets worse when you squint then a tiny amount of Botox can be helpful in this area with light laser resurfacing for the skin. 
You certainly do not want to put Retin A so close to your eyes and if you suffer from dry eyes you want to be cautious about how much Botox is injected in your lower eyelids as it could cause a temporary ectropion and significantly worsen your dry eye problems. 
I really do not think filler is your answer if what bothers you if the crepey skin that gets worse when you squint, but an exam would clarify this for me and allow me to give you the best advice. 
All the best!
Dr Tamboli