Treatment at hypermetropia

At Hm of weak degree in young age in the absence of complaints there is no need in eyeglasses If there are complaints to visual disturbances it is necessary to prescribe an optical correction. At young age only manifest hypermetropia is corrected. After 45 years when the manifest Hm merges with latent they correct entire Hm, and for reading also add presbyopic correction.

At children, at tendency to a squint, glasses should be prescribed after complete cycloplegia (with Sol. Atropini sulfatis 1%). As a rule, at good tolerance one should appoint full correction or a little decreased (by 0,5-1,0D). Correcting glasses must be worn at a condition of accommodation paralysis, for constant weary.

For all Hm of any age glasses for a distance are prescribed only when the Visus without correction is below normal limits.

At myopia whether it is axial or refractive, parallel beam that go from infinitive point, gather before a retina. The remote point (Рr) of clear vision is on limiting distance before an eye.

Myopia, as well as Hm is also divided in 3 degrees: weak - under 3,0 D; average - under 6,0 D; high - more than 6,0D. The highest degree myopia described in the literature is 43,0 D.

Clinics of myopia.

Visual acuity in all myopes is always lower than normal (without correction) as parallel rays of light gather before a retina, on a retina diffuse circles are formed. For the reduction of these circles myopes narrow their eyelids, that is the name myopia origins (“to screw up one's eyes”) to reduce a light stream. The higher degree of myopia, the biger circles of diffusion. But there is no strict dependence between the degree myopia and visual acuity.

For visual acuity correction it is necessary to wear correcting glasses concave (-). To see accurately myopes approach objects to the eye (e.g., at M in 10,0 D Рp=10 cm) that conducts to the excessive convergence - overfatigue of medial rectus muscles and occurrence of so-called muscular astenopia. It is revealed by troublesome sensations around the eyes, forehead, and headaches. These symptoms disappear if close one eye (eyes do not convert). Owing to weariness of medial rectus muscles it is possible to develop a divergent squint (exotropia).

Congenital myopia occurs rare. As a rule it is shown after a birth.

The eye stops to grow at about 12 years when a formation of so-called primary refraction of an eye is finished. At the same age primary or stationary myopia is formed which is a biological variant and depends on discrepancy of refraction power and the eye axis lengths (it usually of a weak degree). In the refraction formation environment conditions are of a great importance. Under adverse conditions of an environment, weakening of an organism and other reasons there comes pathological lengthening of anterior-posterior axis of an eye, or even all eye sizes and then secondary myopia develops which is tend to progress and represents not a biological variant, but a disease.

At this progressing, or malignant, myopia the axis lengthening usually is due to a stretching of a posterior pole of the eye and this represents a number of characteristic changes on the fundus.

Even at small degrees myopia one can see light (white or yellowish) crescent near the optic nerve disk from the temporal part (so-called myopic cone). The cone is a sickleshaped and when it surrounds a disk of an optic nerve it is accepted to name it a posterior scleral staphiloma.

Even more serious retinal changes at M are in a site of a yellow spot (macula lutea) - central chorioretinitis or maculitis which conduct to decrease in the central vision. It is not quiet correct name as we don’t mean inflammational changes but rather degenerative processes in the posterior part of an eye.

The stretching of a posterior eye pole effects on blood vessels as well that leads to the occurrence of haemorrhages of different size. Those haemorrhages agglutinate, resolve partially and leave so-called Fuchs pigment spots.

One of the most difficult complications of a progressing myopia is retinal detachment which often leads to blindness. At myopia above 10,0 D it is observed in 5 % of patients, but sometimes it occurs at lower degrees of myopia.

Astigmatism – is a different refracting ability of an eye in two main meridians.

Types:

1. Regular and irregular

2. By-the-rule and against-the-rule

3. Simple, complex, mixed.

Astigmatism is corrected with 1) cylindrical lenses that have one inactive meridian (axis of a cylinder) and one active meridian perpendicular to the axis of certain convex (+) or concave(-) power; 2) spherocylindrical lenses.

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