Hyperopia

Physiological refraction and core pathology

Normally, the refractive power of an adult eye ranges from 52 to 71 D (averaging about 60 D). In an ideal state — emmetropia — the main focus of the optical system coincides with the retina.

Ametropia (disproportionate refraction) occurs when this balance is disrupted. Unlike myopia (nearsightedness), where the refractive power is too high and light rays converge in front of the retina, hyperopia is a weak type of refraction. The refractive power of the optical system is insufficient for the specific size of the eyeball, so the focus forms behind the retina.

Anatomical features of the eye in hyperopia

External examination and measurement of eyeball parameters reveal characteristic anatomical signs. The size of the eye directly depends on the type of clinical refraction.

While in high myopia the eye is enlarged, in hyperopia the eyeball is small in size. The internal ocular axis (the distance from the posterior surface of the cornea to the retina) in hyperopia is shorter than the physiological norm, which is 21.3 mm in a standard eye. It is this shortened anteroposterior axis that is the main reason the focus misses the light-sensitive membrane.

Pathogenesis and age-related dynamics

To compensate for weak refractive power and see clearly at a distance, the patient requires constant accommodative effort. Because of this, the ciliary muscle is in continuous tone and does not relax completely even at rest.

• At a young age: muscular tension successfully compensates for the optical defect. In mild and moderate degrees, visual acuity is usually not impaired, with reduction noted only at high values.
• With weakening accommodation: clinical symptoms begin to manifest at any degree of pathology. This may be due to poor muscle development or adverse factors.
• By age 45: age-related physiological weakening of the accommodation apparatus occurs. The latent part of hyperopia turns into a manifest form, accompanied by a marked decrease in distance vision.

Classification by tone and degree

When assessing accommodation tone, ophthalmologists distinguish the following types of hyperopia:

1. Manifest: easily detected during a standard refraction examination (especially in young people).
2. Latent: discovered exclusively during pharmacological paralysis of accommodation (against the background of parasympathetic nerve cycloplegia).
3. Total: calculated as the sum of the manifest and latent parts.

According to the severity (in diopters), the pathology is divided into three groups:

• Mild — up to +3.0 D.
• Moderate — from +3.25 to +6.0 D.
• High — +6.25 D and above.

Symptoms, complications, and correction principles

Prolonged near-vision work causes overload of the ciliary muscle. This leads to headaches, accommodative asthenopia, and accommodation spasm. Patients with any degree of impairment are often diagnosed with chronic blepharitis and conjunctivitis, which are extremely difficult to treat.

Of particular danger is the lack of correction in children with moderate and high values. Severe complications develop: amblyopia (functional underdevelopment of the visual analyzer), concomitant strabismus, formation of monocular vision, and pseudoneuritis of the optic nerve (ophthalmoscopically manifested by hyperemia and blurred margins of the optic disc).

Principles of correction:

• Not required for young patients with mild degrees and normal visual acuity.
• Glasses are prescribed when vision in at least one eye decreases or asthenopic complaints are present.
• Optics selection is performed strictly at the peak of cycloplegia (pharmacological paralysis of the accommodation muscle). Permanent full optical correction is prescribed.

Class and exam questions

What else to study on this topic

• Anatomical axes and landmarks of the eyeball (optical, internal, visual)
• Structure of the fibrous tunic of the eye: sclera and cornea
• Astigmatism: etiology, pathogenesis, and optical properties
• Method of performing exophthalmometry and assessing eye position
• Study of lacrimal gland function (Schirmer's test and nasolacrimal tests)

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.