This is a lecture on Refractive Errors, discussing the etiology, clinical features, the different types, diagnosis, treatment and management options. This was presented to undergraduate medical students at University Teaching Hospital (UTH), Lusaka, Zambia, department of Opthalmology by Nghitukuhamba Tangi Elikana Kalipi (6th year medical student) at Cavendish University Zambia, School of Medicine.

1. Name: Nghitukuhamba Tangi Elikana Kalipi
6TH year MBChB
Cavendish University zambia: School of medicine
Moderator: Dr kunda

2. BRIEF ANATOMY The retina (nervous layer) is made up of 10 layers
(histologically) which includes the photoreceptors
RODS & CONES.
LAYERS OF RETINA
1. Pigment Epithelium
2. Layer of rods and cones
(Photoreceptors)
3. External limiting membrane
4. Outer nuclear layer
5. Outer plexiform layer
6. Inner nuclear layer
7. Inner plexiform layer
8. Ganglion cell layer
9. Layer of optic nerve fibres
10. Internal limiting membrane

3. DEFINITION
This is a physiological condition where the refracting system
of the eyes fails to focus objects sharply on the retina.It is
usually corrected with glasses.A useful rapid test to
distinguishbetween refractive error and disease of the eye
is the use of a pin-hole.
In a normal human eye light rays are focused on retina.
If not focused on retina this is called refractive errors. Due to an abnormality in the
shape of the cornea or lens.
Normal eye is called emmetrophic eye. Light rays focused on retina.
Abnormal focusing is called ametrophiceye.

6. AMETROPIA
What leads to ametropia?
1. Abnormality in curvature of cornea
2.Abnormality in curvature of lens
3.Abnormal Refractive Indices
4.Abnormal length of eye ball

7. DIFFERENT TYPES OF AMETROPIA
1. Myopia
2. Hypermetropia
3. Presbyopia
4. Astigmatism
5. Anisometropia
6. Aphakia

8. MYOPIA
Light rays focused in front of retina.
Due to long eye ball or increased curvature of cornea or lens.
Corrected by Biconcave lens.(-D)
Signs and symptoms

9. HYPERMETROPIA
Light rays focused behind retina.
Due to short eye ball or decreased curvature of cornea or lens.
Corrected by Biconvex lens.(+D)
Signs and symptoms

10. PRESBYOPIA
Lens elasticity lost in elderly people due to denaturation of lens protein.
Power of accommodation lost.
So near vision not possible.
Called hypermetropia of old age.
Corrected by Bifocal lens.

11. ASTIGMATISM
Due to faultycurvature of cornea or lens light rays are not focused at one point.
Types
1) Regular:Greatest & least Curvatures right angle to each other.
2) Irregular:Greatest & least Curvatures not right angle to each other.

13. ANISOMETRIA
Difference in the refractive power between the two eyes
One eye becomes dominant
Image of other eye being suppressed.
Each eye should be corrected separately

14. APHAKIA
This condition is described by absence of lens
May be unilateral or bilateral
Corrected by Spectacles with R.P of +11D
If IOL used power should be +19.5D

20. REFERENCES
A K Khurana (2007).Comprehensive Opthalmology. 4th Edition.
Thank you for your time 😊