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Usually esophoria is associated with an uncorrected hypermetropia, caused by excessive stimulations of the inner straight eye muscles that cause an excess of accomodation. In hypermetropia, to observe at a certain distance, the convergence should be less than the accomodation but because they are connected to each other, one finds that to observe an object at a distance of one meter the convergence will be a metric angle. With an uncorrected hypermetropia of 1.00 D, the accomodation effort has to be 2.00 D to see sharp at that distance; therefore either the system adapts the convergence with the accomodation or also the convergence must be of 2 metric angles. In this way however one should have dyplopia and therefore the psychomotoric system will try to balance by either compromising blurring with a doubled image or suppressing the image of one eye.
Certainly the muscular inconvenience can be severe and the pain may be hard to stand.

With the use of lenses that correct the hypermetropiatheis unbalance is virtually eliminated and there will be a tendency to return to the original conditions. This process may be accellerated using lenses too powerful for the ametropia which, inhibiting more the accomodation than the convergence, invert the process that started the esophoria.

From Optometria e Oftalmologia by Prof. Sergio Villani (Volume One).

Related article: How to correct hypermetropia (3/3)

Ophtalmic prescription lenses: Types and characteristics.

The use of cycloplegics to measure the hypermetropia is less used today because of the improved knowledge of the refractive conditions of the eye and its intimate connections with the eye muscles.

The hypercorrection that is thus found will be tolerated when the medicine works off, therefore a correction will be found for nearsightedness and one for farsightedness, coming to a prescription of bifocal lenses even for children of 3-5 years.

Sometimes, wanting to force the correction for farsightedness, especially for children, causes a rejection of the glasses and when the small patients are forced to wear the glasses, they will simply look above the lenses, also because, being small, they have to look upwards to most objects. Putting on glasses that correct an ametropy the patient will find an immediate visual improvement and will have no other inconveniences, after the first moment and especially when the patient is asked to walk, the inconveniences encountered can be various, among which the apparant movement of the images.

When the correction results to be more than necessary, the inconveniences will become less with time but it is better to prescribe the right correction from the beginning (i.e., not trying to correct for the latent hypermetropia) and increase the power of the lenses over time when the manifest hypermetropia manifests itself.

From Optometria e Oftalmologia by Prof. Sergio Villani (Volume One).

Related article: How to correct hypermetropia (2/3)

Various types of graduated prescription lenses

In the case of a slight hypermetropia with a slight exophoria, if the patient doesn’t like to wear the correction all day, he will start to use them at least for nearby work.

Constant use of the correction will cause a reduction of the excess accomodation and close up to the degree of convergence.

The general rule for the correction of hypermetropia is to prescribe the most powerful positive lenses that represent the manifest hypermetropia and to augment in time the correction when the hypermetropia increases with the reduction of accomodation caused by age.

Considering this, age is an important factor. Therefore, a hypermetropia that does not causes problems while young, can become a serious problem. One cannot say when a hypermetropia becomes problematic and also not at which level it creates disturbances but it is certain that a mild hypermetropia often creates more inconvenience to women than men, nervous more than in calm types of people.

From Optometria e Oftalmologia by Prof. Sergio Villani (Volume One).

Articoli Correlati: How to correct hypermetropia (1/3)

Varous types of graduated prescription lenses

The general rule for the correction of hypermetropia is to use the most powerful lenses that do not blur the eyesight. These lenses measure and correct the manifest hypermetropia. A more powerful correction is prescribed only in special cases.
In correcting the hypermetropia, besides that it ensures that the radiations from infinite are focused on the retina, should also ensure that the level of accomodation coincides with the convergence; therefore when correcting the hypermetropia, when there is a accomodation discompensation, it is necessary to balance the eye muscles.

When the eysight is normal and there are no discompensations, no symptoms ofastenopia, it is not necessary to correct the eyesight.

If instead there are symptoms of astenopia, but the eyesight is 10/10 and does not improve with additional lenses, only reading glasses are prescribed. When the astenopia is reduced within 10 days, the correction should be worn constantly.

Normally it is not difficult to decide whether the correction should be worn all day, but in case of doubt, it is important to measure the amplitude of accomodation with the convergence at infinite.

When the eyesight is less than 10/10, the correction must be worn all day and even if the eyesight does not improve initially, one has to wait that this occurs with the complete correction. The correction should be worn all day also in the case of exphoria or exotropia.
From Optometria e Oftalmologia by Prof. Sergio Villani (Volume One).

Various types of graduated prescription lenses

The test is performed on both eyes with a skiascopy stick, made of two sticks containing spheric lenses ranging from +.50 to +4.00 dyopters at .50 intervals.

The double row of lenses is passed in front of the eyes of the observer. If our observer has been corrected of his long-sighted ametropies, he is asked to fix on a point on the skiascopy at 33 cm. With the appropriate stick spheric lenses are added in front of both eyes, starting with +.50 till a neutral point (inferior) is reached which is usually at +.50 D. This is continued till the movement becomes discordant (superior neutral point). If we have added +2.50 D we calculate the difference (in this case +2.50 - +0.50 = +2.00 D) which gives the level of relative negative accomodation, that is the measure of how much accomodation can be released maintaining the convergence for a specific distance.

Because the observer has been corrected for farsightedness, at 33 cm he can accomodate up to 3.00 D. For this reason his relative negative accomodation should not be higher. If it is, we are in the presence of of a latent hypermetropie for far away objects that minifests itself close by.

With this method, within certain limits and ability of the operator , we can avoid the cycloplegy.

From Optometria e Oftalmologia by Prof. Sergio Villani (Volume One)

Related article: Measurement of Hypermetropia with the recession method

Various types of graduated prescription lenses