|Year : 2021 | Volume
| Issue : 1 | Page : 30
Contact lens fitting in nonamblyopigenic anisometropia secondary to monocular aphakia caused by ocular trauma
Gustavo Lustosa Neves, Marcelo Vicente de Andrade Sobrinho
Department of Ophthalmology, Pontifical Catholic University of Campinas, Campinas, Brazil
|Date of Submission||07-Jun-2021|
|Date of Acceptance||20-Jul-2021|
|Date of Web Publication||24-Aug-2021|
Dr. Gustavo Lustosa Neves
Jose Pancetti Avenue, Number 1164, Apartment 94, Rome Block. Postal code: 13033740, Campinas – SP
Source of Support: None, Conflict of Interest: None
Anisometropia is characterized by difference between the refractive errors of the eyes and can be classified into refractive and axial. Aniseikonia is one of the possible consequences of anisometropias. As a general rule, aniseikonia tends to be less significant when we correct axial anisometropias with spectacles and refractive anisometropias with contact lens. One of the possible causes of refractive anisometropias is aphakia, which can be a result of ocular trauma. Amblyopia is a visual neurological disorder characterized by inadequate consolidation of visual acuity, due to insufficient visual stimulation. We present a case of contact lens fitting in a patient with significant difference in axial length between the eyes, but without the corresponding anisometropia, since the patient became aphakic after blunt trauma during childhood affecting the eye with the longest axial length, and probably as a consequence of the aphakia, she did not become amblyopic.
Keywords: Aniseikonia, anisometropia, aphakia, contact lens, ocular trauma
|How to cite this article:|
Neves GL, Sobrinho MV. Contact lens fitting in nonamblyopigenic anisometropia secondary to monocular aphakia caused by ocular trauma. Pan Am J Ophthalmol 2021;3:30
|How to cite this URL:|
Neves GL, Sobrinho MV. Contact lens fitting in nonamblyopigenic anisometropia secondary to monocular aphakia caused by ocular trauma. Pan Am J Ophthalmol [serial online] 2021 [cited 2021 Oct 20];3:30. Available from: https://www.thepajo.org/text.asp?2021/3/1/30/324525
| Introduction|| |
Anisometropia is a clinical condition characterized by the existence of difference between the refractive errors of the eyes. It is a very common condition in clinical practice. The prevalence is around 20% of the population for anisometropias up to 0.50 diopters (D) or more and 2%–3% for 3.00 D or more.
It tends to become clinically significant when it reaches 1 D or more. When it reaches values of 2.00 D or more for myopia, 1.00 D or more for hyperopia, and 1.50 D or more for astigmatism, if not corrected in the period of greatest sensory plasticity of the optical pathways (from birth to consolidation of visual functions) can lead to amblyopia and problems in binocularity.,
The anisometropias can be classified into refractive and axial. The clinical management follows the Knapp's rule. It determines that the difference between the sized of the retinal image that results from the axial anisometropia is reduced when the corrective lens is put in the anterior focal plane of the eye. That's why, following the Knapp's rule, spectacles should be prescribed for axial anisometropia correction and contact lenses for refractive anisometropia correction.
When it exceeds 6 D, the patient generally does not experience symptoms, due to a mechanism of suppression of the cerebral cortex in relation to the eye affected by greater ametropia. For this reason, anisometropia is considered, together with strabismus, a major cause of amblyopia.,
Amblyopia, in turn, is a visual neurological disorder characterized by inadequate consolidation of visual acuity, due to insufficient visual stimulation during the most important period of development of the optical pathways.,
These changes in visual stimuli may be a consequence of the interaction between the various ocular components, and axial length is the main contributing factor.
We present a case with significant difference in axial length between the eyes, but without the corresponding anisometropia, since the patient became aphakic after blunt trauma during childhood affecting the eye with the longest axial length, and probably as a consequence of the aphakia, she did not become amblyopic.
| Case Report|| |
A 42 years old female patient referred to the Contact Lens Department of the Pontifical Catholic University Hospital, for contact lens fitting due to aphakia. The patient reported a history of ocular trauma in her right eye, at the age of 6. Despite referring perforating trauma, she was not able to explain details about the trauma mechanism but does not show signs of previous ocular open globe injury in this eye. The biomicroscopy shows an aphakic eye [Figure 1]. In addition, she has a personal history of two strabismus surgeries with satisfactory result.
Upon examination, the patient presented the clinical features shown in [Table 1] and [Table 2].
|Table 3: We proceeded with the adaptation of a spherical monocurve rigid gas permeable contact lens for each eye|
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The biometry evidenced an important axial difference between the eyes. Ultrasonography of the right eye was also performed, showing the lens dislocated to the vitreous chamber, as shown in [Figure 2].
Subsequently, the patient was referred to the retina and vitreous department, to evaluate the possibility of surgical removal of the lens. According to the patient's wishes, we maintain clinical follow-up of the case, with no surgical procedure performed so far.
| Discussion|| |
There are several ways to classify anisometropia. One of them is the difference between the magnitude of the refractive errors.
In this case, according to Gettes, it can be classified as: 
- Low (difference in refractive errors from 0 to 2.00 D): Patient is usually able to tolerate the total correction of the refractive errors
- High (from 2.01 to 6.00): patients tend to have problems with binocularity
- Very high (when >6.01): patients are usually asymptomatic due to the suppression of the image formed by one of the eyes.
The correction of potentially amblyopigenic refractometric errors should be performed as early as possible, to avoid the establishment of amblyopia. If amblyopia is present, the treatment should be instituted the same way, since there is a reduction in its effectiveness with increasing age, especially above 7 years.,
Patients with axial anisometropia should be supposedly corrected with spectacles, which would lead to smaller amounts of aniseikonia. However, sometimes, it is possible to try to correct these patients with contact lenses. In refractive anisometropias (e.g., monocular aphakia), the aniseikonia yield by the correction with spectacles is about 30%, and when corrected with contact lenses, 7%.
We present a case of axial anisometropia, with axial length difference of 3.82 mm. The relationship between the axial length and the ocular refractive power is approximately 0.3 mm of axial length for each 1.00 D, when based in the “reduced eye” of Gullstrand-Emsley. Thus, it is possible to estimate a refractometric difference between our patient's eyes of about 12.75 D, which can be classified as very high anisometropia.
Interestingly enough, due to the right eye's axial length (29.02 mm), we concluded that this eye was high myopic previously to the trauma and became low hyperopic afterward (+1.25, +1.25; 90), while her left remained myopic (−3.25, −2.50; 180). Even with axial length difference of 3.82 mm, the patient did not become amblyope, due to the trauma (and subsequent aphakia) in her right eye, and prompt correction with spectacles during her childhood.
The correction of the anisometropia prevented the suppression of the image by the cerebral cortex and consequently avoided amblyopia, which would be the most likely outcome for the patient.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]