Refrective error

MYOPIA & HYPERMETROPIA

• EMMETROPIA• It is the normal optical condition of the eye. • The eye is considered to be emmetropic when

incident parallel rays of light from infinity come to a focus on the retina (fovea centralis)

From: Basic opthalmology 4th edition, page 48

MYOPIA [Short Sight]

MYOPIA [Short Sight]• It is that dioptric

condition of the eye in which with the accommodation at rest, incident parallel rays of light come to a focus anterior to the light sensitive layer of retina.

symptom• Indistinct distant vision is the most common

symptom. Usually the young children are unable to see the blackboard clearly.

• Black spots are seen floating before the eyes.• There is discomfort after near work.• Flashes of light may be seen.

Signs

• May come with Prominent eyes, large pupil and deep anterior chamber

• Apparant divergent squint may be present.• Fundus examination (cont.)

Macula• Foster Fuch’s flecks—These are dark pigmented circular

areas of intrachoroidal haemorrhages.Peripheral Fundus• Cystoid degeneration of or a serrata and tesselated (tigroid)

fundus may be present.• Weiss reflex streak is seen due to detachment of vitreous at

the posterior pole.• Holes and tears in the retina may be present peripherally

From: Basic opthalmology 4th edition, page 49

TYPE OF MYOPIA [Short Sight] Congenital [developmental] myopia• • It is present at birth.• • It is stationary usually.• • It may be unilateral or bilateral.• • Bilateral myopia may be associated with convergent squint.Simple myopia• • It is the most common type of myopia.• • There are no degenerative changes in the fundus.• • It does not progress after adolescence when a• degree of –5 or –6 D is attained.Pathological myopia• • It is a type of degenerative and progressive myopia.• • It begins at the age of 5-10 years and increases steadily

Treatment

• Spectacles—Myopia is treated by prescribing suitable correcting spherical concave lenses for constant use

Cont.care of eyes- Proper position, correct distance from the book (about 25 cm) while reading.

Operative• i. Radial keratotomy/ Excimer laser/LASIK

HYPERMETROPIA [Far Sight]

• HYPERMETROPIA [Far Sight]

• It is that dioptric condition of the eye in which with the accommodation at rest the incident parallel rays of light come to a focus posterior to the light sensitive layer of the retina.

Symptoms

These are noticed specially in the evenings after close work.• There is blurring of vision for near work.• There may be frontal headache and eye strain.• Burning and dryness in the eyes are usually

present.

From: Basic opthalmology 4th edition, page 51

Signs• Presented with small eye as a whole. • Accommodative convergent squint may

be present.• Fundus examination:I. It may show no abnormality.II. A bright reflex, i.e. watered silk

appearance may be seen.III. Pseudopapillitis, i.e. hyperaemic disc

with blurred margin may be present which is similar to papillitis

From: Basic opthalmology 4th edition, page 51