Normal (emmetropic eye – when parallel rays coming from infinity are focused light sensitive layer of retina with the accommodation being at rest , this state is called emmetropia and eye is called emmetropic eye ) eye parallel rays focused on the retina . Eyes have been provided with a mechanism to see clearly from a near object and this mechanism is called accommodation.
Anomalies of accommodation include the following :-
- Deficient Accommodation
2) Increased accommodation
a) Excessive of accommodation
b) Spasm of accommodation
Presbyopia means eyesight of old age. It is not an error of refraction but it is a physiological aging process due to insufficiency of accommodation in which near point gradually recedes beyond the normal reading or working distance . Presbyopia normally begin 40 years of age .
Causes :- Presbyopia occurs due to the following –
- Decrease in the elasticity of lens capsule with increasing age leading to presbyopia
- Progressive increase in size and hardness of the lens capsule with increasing age
- Causes of premature presbyopia include
Premature sclerosis of the crystalline lens ,
Presenile weakness of ciliary muscle,
Chronic simple glaucoma which may lead to premature prebyopia
- Patients usually complaint of difficulty in reading in small prints. Another Difficulty in near vision – Patients complaint of the patient is difficulty to threading a needle.
- Asthenopic symptoms such as headache, eyeache ,pain, browache ,tiredness of eye due to fatigue of the ciliary muscle
- Sometimes diplopia may be seen
Optical treatement :-
Spectacle correction – unifocal, bifocal,progressive lens should be used.
Contact lens- Multifocal soft contact lens should be used. It may be used daily disposable or monthly disposable basis.
Surgical treatement :-
Various surgical method have been proposed to treate to method prebyopia , which include the following
- Cornea based procedure –
- monovision conductive keratoplasty
- monovision LASIK
- Presbyopic bifocal LASIK or LASIK- PARM
- Presbyopic multifocal LASIK
- Presbyond laser blended vision , it is a micro-monovion LASIK with added laser correction
- Lens based procedures-
a)multifocal IOL implantation
b)Monovision – In this procedure one eye correct with distant power and other eye is correct with near power .
3) Sclera based procedures-
a) Anterior ciliary sclerotomy
b) Scleral spacing procedures
and scleral ablation
c Scleral expansion
Insufficiency of Accommodation :-
When the accommodative power is persistently below the normal physiological limits for patient’s age.
Anaemia, malnutrition, diabetics, pregnancy, other physiological illness,open angle glaucoma causes weakness of ciliary muscles
Premature cataract which leads to presbyopia at early age than normal age.
Headache , eyeache, browache , fatigue, inability to near work, diplopia
Spectacles correction- unifocal, bifocal or progressive multifocal lens should be used.
Contact lens correction – Multifocal soft contact lens should be used. It may be used daily disposable or monthly disposable basis.
Accommodation exercise usually help in recovery the conditions but exercise are not useful in cases with general debility.
Paralysis of accommodation :-
Paralysis of accommodation refers to complete absence of accommodation . It is also known as cyclopegia.
Cause of paralysis of accommodation :-
In unilateral cases Atropine , homatropine etc parasympathetic drugs are lead to cause paralysis of accommodation. In otherside third nerve palsy is the main cause of paralysis of accommodation . It may be due to trauma of eye, inflammation of eye .
In bilateral cases diphtheria, syphilis,diabetes, alcoholism,celebral or meningal diseases are lead to cause paralysis of ciliary muscles
Enability to do the near work
Photobia ( due to dilated of pupil is usually associated enability to do the work)
Dark glasses are required in reducing the photophobia
Convex lenses are prescribed while doing near work
Treatement of systemic diseases
Excessive of accommodation :-
It is used to describe a situation in which an individual exerts more than than the normal required accommodation for performing a certain near work.
Causes :- hypermetropes, myopes, astimatic young patient frequently use excessive of accommodation, Ill fitting spectacles are also laed to cause excessive of accommodation
Symptoms :- blurred vision, headache, micropsia
For optical treatement refractive error should be corrected after performing cyclopegic refraction.
Spasm of accommodation :-
It refers to continuous exertion of abnormally excessive accommodation.
Causes :- Found mainly in children who attempt to compensate his refractive error
Iridocyclitis is the another cause of spasm of accommodation
Strong mydriatic drugs such as echothiophate and diisopropyl flurophosphate are main cause of spasm of accommodation
Spectacles glasses are should be used when eye are used
Production of the ciliary muscles paralysis with atropine should be kept for a long time.