How do we know what kind of medical requirements for a waiver are okay with a PRK or a LASIK corrective surgery?

Apparently, like so many things, it depends on the result of an individual exam. An article out of Belvoir that gives some indications and a direction to go for answers:

https://www.fbch.capmed.mil/healthcare/refractivesurgery/army.aspx

You can google the US Army Aeromedical Policy Letters and within those documents you will find information pertaining to PRK. Remember there are always waivers which you can apply for. This coupled with talking to your unit's Flight Surgeon and PRK clinic should give you your clear left and rights and what your next COAs are.
If you have any additional questions please let me know as I have just gone through this process and recently submitted my packet for 153A.

So folks i contacted the aero medical office at FT Rucker, they gave me the list of policy documents which give guidance about the vision requirements. It clearly states that the initial flight physical one should have uncorrected at 20/70.


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AEROMEDICAL CONCERNS: Decreased visual acuity degrades look-out and target acquisition, two important factors in successful outcomes of aviation combat operations.
WAIVERS:
Initial Flight Applicants: Failure to meet Class 1 visual standards will be considered for exception to policy on a case-by-case basis in the age of Refractive Surgery and considering the needs of the Army. Applicants must correct to 20/20, both near and distant Uncorrected distant visual acuity must be 20/70 or better. Uncorrected near visual acuity must be better than 20/40. Cycloplegic refraction within 3/4 diopter of standards will be considered.
Rated and Non-rated Ai rcrew (to include Class 2/3/4 applicants): Waivers are required for anyone with uncorrected distant or near visual acuity of greater than 20/400 in any eye, provided correction to
20/20. Restrictions require flight with spectacles or contact lenses that correct to 20/20 and must have in possession a backup pair of spectacles. Waiver for visual acuity outside standards will be considered on a case-by-case basis in designated individuals provided the central and peripheral retina is normal, no other ocular conditions exist, and all other visual standards are met.
INFORMATION REQUIRED:
Optometry/ophthalmology evaluation must include dilated fundus examination for cases of decreased visual acuity not due to simple myopia, hypermetropia {hyperopia), astigmatism or presbyopia.
Retinal evaluation must be obtained refractive errors corrections greater than ±5.5 diopters.Patients with progressive astigmatism should be evaluated to exclude keratoconus.
Class 1 applicants shall submit three cycloplegic refractions completed IAW ATB-5 {Cycloplegic Refraction)
TREATMENT: Refraction by spectacles is allowed within the limits set by HHTAR 40-501THH, Chapter 4. See APL Corneal Refractive Surgery.
FOLLOW-UP: Depending on the findings, annual follow-up requirements may range fr9rn annual vision screening with FDHS/FDME to annual optometric/ophthalmologic evaluation.
DISCUSSION: Myopes {persons with elongated globes) have a risk of further myopic progression, which rises with the degree of myopia regardless of age. High myopes have considerable visual distortion at the periphery of their spectacle lenses. In addition, they may see halos or flares around bright lights at night and are at increased risk of night blindness. Whereas myopes have an increased risk of retinal detachment and lattice degeneration of the retina, exposure to routine G-forces in flying has not been shown to increase these risks. Myopia is usually a progressive condition, stabilizing for individuals around the age of 30. Whenever a prescription is changed, aircrew should be warned about transient visual distortion and counseled on the period of adjustment necessary. Evidence suggests that there is no difference in civil accident rates or in naval carrier landing accidents in pilots who require visual correction. Severe myopia tends to be a problem pertaining to Class 2 personnel since the entry requirements for other aircrew tend to be sufficiently stringent to exclude those whose vision would deteriorate that much.
Hyperopes with +3.00 or more of correction may experience problems with vision after treatment with anticholinergic agents. Hyperopes also have more problems with visual aids such as night vision goggles when they develop presbyopia. The interposition of another layer of transparency {spectacle lenses)
US Army Aeromedical Policy Letters and Technical Bulleti


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I dont know how to upload the pdf in here.
So pasted the polocy document here.