UNIT 3: Epidemiology

Question 1

Epidemiology

Answer 1

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.

Question 2

When refracting a hyperope,

Answer 2

We must FOG or use cycloplegics.

Otherwise, the habitual use of accommodation causes spasmadic action of the ciliary body. (Could cause pseudo-myopia)

Question 3

Classification of Hyperopia (Total)

Answer 3

Manifest +Latent Hyperopia

Question 4

Classification of Hyperopia (Latent)

Answer 4

(Patient in accommodation Spasm) —> Not revelaed by normal refraction

This spasm could be fixed or temporary

Question 5

Classification of Hyperopia (Manifest)

Answer 5

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

Question 6

Correction By Age (Hyperopia) Up to 6

Answer 6

-Correct if strabismus
-Lower VA or Asthenopia

Question 7

Correction By Age (Hyperopia) 6 to teens

Answer 7

-Correct is asthenopic
-Find more latency at this age
-Under correct slightly
(SUBS. They cant take what they need OBJ.)

Question 8

Correction By Age (Hyperopia) Adult

Answer 8

-Full error revealed and corrected
-Caution in full new RX –> must re-adjust
conv, acc systems - may need VT

Question 9

Correction By Age (Hyperopia) Presbyopia

Answer 9

-May up distance due to the change of index of lens nucleus
-Will also find latents at this time

Question 10

Correction By Age (Hyperopia) Old Age

Answer 10

-May up myopia (due to lens change)

Question 11

Classification (Astigmatism) Total

Answer 11

1) Anterior Corneal
2) Residual
a)Posterior corneal
b)Lenticular Surface

Question 12

Classification (Astigmatism) Corneal

Answer 12

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

Question 13

Classification (Astigmatism) Lenticular

Answer 13

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

Question 14

Lowest incidence of Myopia

Answer 14

-Spain (Portugal, P.R,. Filipino)
-Hawaii
-Africa

Question 15

Highest incidence of Myopia

Answer 15

-China
-Parts of the U.S.

Question 16

Classification of myopia

Answer 16

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

Question 17

Objective indications for Myopia

Answer 17

-Squinting (“Crow-feet horizontal wrinkles)
-Dilated pupils
-Exophthalmos

Question 18

Pseudomyopia

Answer 18

-Condition of an on-going spasm of accommodation
-Hyperope or emmetrope becomes falsely myopic
-Other names:
-School myopia
-Functional myopia
-False myopia
-Refractive Myopia

Question 19

Corrections for Pseudomyopia

Answer 19

-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

Question 20

Attempts to control myopia

Answer 20

• 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)

Question 21

Congenital myopia

Answer 21

present at birth

Question 22

Acquired myopia

Answer 22

A result of prolonged stress on the eyes during close work

Question 23

Classification of hyperopia by degree

Answer 23

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

Question 24

TRUE OR FALSE
People with a certain amount of astigmatism in a specific location tend to remain stable.

Answer 24

TRUE
- Astigmatism rarely changes

Question 25

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.

Answer 25

FALSE
- There is a standard INCREASE in add power.
- Add power have a definite pattern in
increasing amounts.

Question 26

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 _____________.

Answer 26

1) LATENT HYPEROPIA
2) MANIFEST

• Hyperopia is usually stable and predictable.

Question 27

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.

Answer 27

1) MYOPIA
2) DEFINITE ENVIRONMENTAL

• Myopia can be altered due to behavioral/
  Environmental factors, therefore is studied &
  analyzed a great deal.