UNIT 3: Epidemiology Flashcards
Epidemiology
The study of the distribution and determinants of health-related states and events in populations, and the application of this study to the control of health problems.
When refracting a hyperope,
We must FOG or use cycloplegics.
Otherwise, the habitual use of accommodation causes spasmadic action of the ciliary body. (Could cause pseudo-myopia)
Classification of Hyperopia (Total)
Manifest +Latent Hyperopia
Classification of Hyperopia (Latent)
(Patient in accommodation Spasm) —> Not revelaed by normal refraction
This spasm could be fixed or temporary
Classification of Hyperopia (Manifest)
Revealed by routine refraction (what actually turns up in phoropter)
-Symptoms: Asthenopia
-HA’s, Tearing, photophobia, nausea, general fatigue, avoids N.V. Tasks
-Objective Symptoms:
-Vertical brow wrinkles
-Convergent strabismus
-ESO
Correction By Age (Hyperopia) Up to 6
-Correct if strabismus
-Lower VA or Asthenopia
Correction By Age (Hyperopia) 6 to teens
-Correct is asthenopic
-Find more latency at this age
-Under correct slightly
(SUBS. They cant take what they need OBJ.)
Correction By Age (Hyperopia) Adult
-Full error revealed and corrected
-Caution in full new RX –> must re-adjust
conv, acc systems - may need VT
Correction By Age (Hyperopia) Presbyopia
-May up distance due to the change of index of lens nucleus
-Will also find latents at this time
Correction By Age (Hyperopia) Old Age
-May up myopia (due to lens change)
Classification (Astigmatism) Total
1) Anterior Corneal
2) Residual
a)Posterior corneal
b)Lenticular Surface
Classification (Astigmatism) Corneal
1) Regular: 2 principal meridians 90 degrees apart each meridian uniform
a) Referred to Each Cornea
1. WTR (direct)
-Curvature of greatest power –> Vertical
-Curvature of least power –> Horizontal
2. ATR (inverse)
-Curvature of greatest power
3.Oblique
2) Irregular: 2 principal meridians NOT 90 degree apart or curvature in any meridian not uniform
Classification (Astigmatism) Lenticular
1) Regular or irregular
2) Unequal curvature of surfaces or layers
Prevalence: Most widely spread refractive error –> approx. 80% of population
For low Astig: Spherical equivalent –> SPH + 1/2 cyl
Lowest incidence of Myopia
-Spain (Portugal, P.R,. Filipino)
-Hawaii
-Africa
Highest incidence of Myopia
-China
-Parts of the U.S.
Classification of myopia
a) Very low 0.00 to -1.99D
b) Low -1.00 to -3.00D
c) Medium -3.00 to -6.00D
d) High -6.00 to -10.00D
e) Very High > -10.00D
Objective indications for Myopia
-Squinting (“Crow-feet horizontal wrinkles)
-Dilated pupils
-Exophthalmos
Pseudomyopia
-Condition of an on-going spasm of accommodation
-Hyperope or emmetrope becomes falsely myopic
-Other names:
-School myopia
-Functional myopia
-False myopia
-Refractive Myopia
Corrections for Pseudomyopia
-Requires a PLUS lens
a) Fogging lenses = Strong plus for constant
wear for relaxing acc. Dist & Near.
b) Near Point Correction ( Plus for near )
c) Prism Base In = to relieve convergence from
the work of overcoming excessive exophoria & relieve acc/conv. Function
d) Visual Training
Attempts to control myopia
- Prism BI (often used during VT)
- Visual Training = to relax accommodation
- Hormones and diet (no good studies)
- Contact lenses ( PMMA fit flatter than flattest
K) (Orthokerotology) - Bifocals = relaxes acc/conv.
-RK (radial keratotomy), PRK (photorefractive keratectomy)
Congenital myopia
present at birth
Acquired myopia
A result of prolonged stress on the eyes during close work
Classification of hyperopia by degree
1) Low 0 - +3.00D = Normal vision
2) Medium +3.00 - 5.00D = Subnormal vision
3) High > 5.00D (subnormal at early age, then ->
Pathological)
- Micro ophthalmus
- Optic edemas
- Tumors
TRUE OR FALSE
People with a certain amount of astigmatism in a specific location tend to remain stable.
TRUE
- Astigmatism rarely changes
TRUE OR FALSE
Once people become presbyopic, they tend to have a standard decrease in add power dependent upon their age and near-visual requirements.
FALSE
- There is a standard INCREASE in add power.
- Add power have a definite pattern in
increasing amounts.
FILL IN THE BLANK
Once people are declared Hyperopic, their degree of hyperopia doesn’t change greatly over the years. The only time they fall “ outside the norm” is when __________ ____________becomes _____________.
1) LATENT HYPEROPIA
2) MANIFEST
- Hyperopia is usually stable and predictable.
FILL IN THE BLANK
Of all the refractive errors, ________ is the only one to show ___________ _____________ factors on the incidence, distribution, degree and changes in Myopia.
1) MYOPIA
2) DEFINITE ENVIRONMENTAL
- Myopia can be altered due to behavioral/
Environmental factors, therefore is studied &
analyzed a great deal.
