What is the difference between emmetrope and presbyopia eyes

Presbyopia

Symptoms of failure of accommodation Small print becomes indistinct. Near point recedes and the patient tends to hold his head backward and his book forwards until the distance in between is reached when clear vision in any circumstances is difficult. Troubles are experienced at first in the evening when the light is dim and the pupils are dilated, permitting diffusion circles to develop. Difficulties arise easily after along day of fatigue. Presbyopia likes, to read in a brilliant illumination and he tries to get the light between his eyes and the book or to read in sunlight to make the pupils to constrict. In senility when the pupils become small and old person without accommodation may see near objects with fair degree of detail. Failure of accommodation leads to eye strain with effort. The eye strain will result in:- Headaches Tiredness of eyes Redness and burning of eye with excessive tearing on efforts. Un ability to do more useful near work.

Increase accommodation Decrease accommodation Excessive accommodation Spasm accommodation Insufficiency accommodation Paralysed accommodation

Excessive accommodation Causes Certain degree of sustained increased accommodation is frequently in:- Young hyperopes which considered as a physiological adaptation of CM in interest of clear vision. In myopes especially in young subjects doing much near work. In astigmatic errors doing much work. In excessive convergence. In all patients trying to gain clear near vision in spite of refractive errors. A large a mount of near work is an important factor in the causation of accommodative strain especially when:- Work is habitually undertaken in deficient or excessive illumination. The presence of uncorrected refractive error. Or the wearing of improper or ill-fitting spectacles are other causes of excessive accommodation. Other causes are general debility and ill health either physical or mental.

Symptoms and signs of excessive accommodation The condition involves production artificial myopia which varies from time to time according to the amount of near work, at rest the refraction is hypermetropia but after strain it’s myopia and more and more myope with more effort. Both far point (F.P.) and near point (N.P.) become closer to the eye. Distant vision becomes blurry. Distant vision is therefore can be improved by concave lens. In more marked degree the near work also becomes blurry with confusion of printed pages which is relieved by temporary rest. There are typical symptoms of accommodative asthenopia including headache, feeling of fatigue and discomfort in the eyes themselves. Normally after the instillation of atropine drops in the patient’s eyes to abolish the action of the ciliary muscle the refraction becomes hypermetropic by 1D, the diagnosis is proved by finding a great difference between the precycloplegic and postcycloplegic refraction. The prognosis of such cases is good and the treatment is effective after prescription of postcycloplgic correction.

Spasm of accommodation Causes:- Continuous sever near work in presence of refractive error. Miotics such as pilocarpine eye drop may bring spasm of CM. Precipitating factors:- Marked degree of muscular imbalance (phoria or tropia). Trigeminal neuralgia. Dental lesion. Cases of iridocyclitis. The ciliary spasm usually out of the patient’s control (involuntary) and its amount may reach 10Ds or more that leads to marked artificial myopia. Symptoms:- A blurring of near and distant vision. The patient is neurotic and drowzy. All symptoms of accommodative strain in excess. In some patients pilocarpine drops that used in treatment of glaucoma may produce ciliary spasm.