Ophthalmology: Standards and Random Flashcards
Service Group 1
Aviators qualified for unlimited or unrestricted flight duties
Service Group 2
Aviators restricted from shipboard aircrew duties (include V/ STOL) except helicopter
i.e., fixed wing carrier landings
Service Group 3
Aviators restricted to operating aircraft equipped with dual controls and accompanied on all flights by a pilot or copilot of Medical Service Group 1 or 2, qualified in the model of aircraft operated.
Light passes through the 1 , 2 , 3 , 4 , and 5 before hitting the retina
- Tear film
- Cornea
- Anterior Chamber
- Lens
- Vitreous humor
Total refractive power of the eye
Approx 60 D
Note: roughly 44 D come from cornea and 16 D come from lens
Standard eye length
24 mm
standard focal length = 16.7 mm (see below)
- Remember: lens power = 1/f*
- f = 1 / lens power (1/60D*) = 0.01666 m*
- *Standard refractive power*
How thick is the cornea compared to the lens?
Cornea = 0.55mm
Lens = 4.5 - 5.5mm
BUT, the cornea still contributes more to refractive power
Why does the Navy use minus cyl
…because Optometry “won”
Ophthalmologists will use (+) when documenting cyl (why some of the waiver guidelines fluctuate between -1 and +1)
3 components of spectacle prescriptions
Sphere, Cyl, Axis*
*Axis from 001 - 180 (never negative or greater than 180)
Steepest meridian
aka the “most minus” meridian
Transposition
Converting (+) cyl to (-) cyl Rx
- Add Sph and Cyl powers = new Sph value*
- Flip the sign of the cyl value*
- Change the axis by 90 deg*
Calculate Spherical Equivalence
Sph + 1/2 Cyl
Used on the refractive surgery AMS, and to “spot check” VA (-0.25 D of SE is approx 1 line of VA)
Prism ____ to the deviation
points to the deviation
- Note: light bends towards the BASE*
- Ex. BI (Base In) = exo (aka prism pointing out)*
- BO (Base Out) = eso*
- BD (Base Down) = hyper*
- BU (Base Up) = hypo*
DVA for SNA
Better than 20/40-0 and correctable to 20/20-0 on GoodLite
DVA for all applicants except SNA
NO LIMIT for Uncorrected*
20/20-0 on Snellen OR 20/20-3 on AFVT or GoodLite
*Exception = Aircrew Applicant for rotary wing (must be better than 20<100, aka SG1 standards) and correct to 20/20-0 on Snellen or 20/20-3