Angular aberration has no effect on reading performance

By Prof. Dr. Dr. R. Werth

When looking at a distant object, the axes of both eyes are directed toward this object so that the image of the object is projected onto corresponding points on the retina in both eyes. The brain can then merge (fuse) the images from both eyes into a single image. However, even if one eye is not focused precisely on the object to be viewed and one eye axis is aligned as if the object to be viewed were slightly in front of or behind the object actually being viewed (i.e., in the Panum area) and the image of the actual object to be fixed is not projected exactly onto corresponding areas of the retina, the images on the retinas of both eyes can still be merged into one object by the brain. However, this only applies to minor deviations of both eye axes.

Deviation from ideal eye position

If the eyes tend to deviate slightly from the ideal eye position, this slight deviation can also be compensated for spontaneously by the deviating eye correcting its position. For example, if a prism is held in front of the eye of a person with normal vision so that the fixed object is no longer projected onto a point on the retina that corresponds to the point on the retina of the other eye (non-corresponding retinal point), the eye in front of which the prism is held automatically performs a compensatory movement. This causes the fixed object to reappear at a corresponding retinal point.

Experiment with prisms

Even when normal readers were artificially induced to deviate their eye axis inward or outward by placing prisms of up to 6 prism diopters in front of their eyes, this had no effect on their reading performance. (Dysli and Vogel 2014). Double vision only occurs when the deviation of one eye is so great that no compensatory eye movement can correct it and the brain can no longer merge the two retinal images.

Angular vision aberration

“Angular vision aberration” is a term that is not used in scientific medical optics. Angular aberration refers to a slight misalignment of the eyes that only appears in the measurement procedure proposed by H.-J. Haase and has been interpreted as a form of heterophoria, i.e., latent strabismus. The aim is to determine the weighting (prevalence) of one eye in vision.

Valence test for heterophoria according to Haase

In the Haase valence test, a mark must be fixed at a distance of 5-6 m. Above or below the mark to be fixed, a triangle is presented approximately 1.5 m in front of or behind this mark. If neither eye is dominant in this directional perception, i.e., if both eyes are equivalent, both triangles are seen in the center of the fixation mark. However, if the triangles are perceived as being offset to the side of the center of the fixation mark, this is interpreted as greater weighting (prevalence) of one eye. If there is prevalence of one eye, according to Haase, this should be converted to equivalence by placing prisms in front of the eye. If there are different degrees of prevalence for triangles in front of and behind the fixation mark, this is interpreted as a sign of a slight misalignment of the eyes and a fixed image is not projected onto exactly the same areas of the retina in both eyes (Schroth V, ldschinski 2001; IVBS 2912).

This slight difference in the prevalence of both eyes should be corrected using prisms so that the prevalence of one eye disappears. However, studies have shown that the prevalence of one eye is the norm in people with normal vision and can be detected in 70 to 80% of the population without affecting visual performance in every case (Kommerell and Kromeier 2002; Kříž and Skorkovská 2017). Studies have also shown that the prevalence of one eye measured by Haase’s test is not a reliable measurement and that the prevalence of one eye can only be corrected by prisms in exceptional cases (Schroth, Jaschinski 2007).

Dependence on body posture

The heterophoria detected by the measurement method proposed by Haase and its correction using prisms, as advocated by Haase, had no influence on reading performance (Jainta and Joss 2019). A comparison of children with dyslexia and normal readers showed no causal relationship between mild vertical heterophoria and reading performance. Heterophoria appeared to occur depending on the children’s posture (Quercia et al. 2015).
Our studies on children with dyslexia (Werth 2006; 2018; 2019, 2021; Klische 2017) clearly show that dyslexia is not a consequence of heterophoria. All studies involving more than 350 children show that a dramatic improvement in reading performance occurred immediately when the following sub-skills important for reading were controlled by software in such a way that they were appropriate for reading:

Simultaneous recognition

• Fixation times
• The time from the presentation of the material to be read to the correct pronunciation
• Eye movements

Literature

Dysli M, Vogel N, Abegg M. Reading performance is not affected by a prism induced increase of horizontal and vertical vergence demand. Front Hum Neurosci. 2014; 8; 431. doi:10.3389/fnhum.2014.00431.

Schroth V, ldschinski W Beeinflussen Prismen nach H.-J. Haase die Augenprävalenz?
Klein Monatsbl Augenheilk 224, 2001, 32-39.

IVBS, Internationale Vereinigung für Binokulares Sehen. Richtlinien zur Anwendung der MKH. 2012

Kommerell, G., Kromeier, M. Prismenkorrektion bei Heterophorie. Ophthalmologe 99, 3–9 (2002). https://doi.org/10.1007/PL00007112.

Kříž P, Skorkovská Š. Distance associated heterophoria measured with polarized Cross test of MKH method and its relationship to refractive error and age. Clin Optom (Auckl). 2017 Mar 31;9:55-65. doi: 10.2147/OPTO.S123436. PMID: 30214361; PMCID: PMC6095580.

Schroth V, Jaschinski W. Beeinflussen Prismen nach H.-J. Haase die Augenprävalenz? [Do prism corrections according to H.-J. Haase affect ocular prevalence?]. Klin Monbl Augenheilkd. 2007 Jan;224(1):32-9. German. doi: 10.1055/s-2006-927268. PMID: 17260317.

Jainta S, Joss J. Binocular advantages in reading revisited: attenuating effects of individual horizontal heterophoria. J Eye Mov Res. 2019 Dec 9;12(4):10.16910/jemr.12.4.10. doi: 10.16910/jemr.12.4.10. PMID: 33828742; PMCID: PMC7880141).

Quercia P, Quercia M, Feiss LJ, Allaert F. The distinctive vertical heterophoria of dyslexics. Clin Ophthalmol. 2015;9:1785-1797. Published 2015 Sep 25. doi:10.2147/OPTH.S88497.

Werth R: Therapie von Lesestörungen durch Erkennen und Beheben der Ursachen
Ergotherapie und Rehabilitation 9 (2006b) 6-10.

Werth R: Rapid improvement of reading performance in children with dyslexia by altering the reading strategy: a novel approach to diagnoses and therapy of reading deficiencies. Restor Neurol Neurosci 36, 2018, 679-691 2018.

Werth R: Dyslexic readers improve without training when using a computer-guided reading strategy. Brain Sci. 2021, 11(5), 526

Werth R: What causes dyslexia? Identifying the causes of dyslexia and effective compensatory therapy
Restorative Neurology and Neuroscience , 37, 2019, 2019, 1-18.

Klische A , Leseschwächen gezielt beheben. Tectum, Baden-Baden, 2007.

Causes:

If word endings are omitted when reading, this has the following possible causes:

The reader tries to read the word at once. If the word is too long for this, the ends of the words are typically not physically seen.

Example:

The reader wants to read the word “master”. However, it can only read a maximum of 5 letters at a glance and is highly unlikely to recognise the last letter. So he reads “maste“.

Remedy:

This reader must divide the word werden into two segments and read mast-er in order to recognise all the letters with certainty.

Can incorrect eye movements lead to dyslexia?

Absolutely. Controlled, regular eye movements are essential for error-free reading.

Typical errors are:

• Too wide gaze jumps.
  Letters are omitted.
• Too short gaze jumps.
  The word segments overlap, the reader could actually read faster.
• The eyes jump back and forth irregularly.
  The reader tries to read the text in an unsystematic way, it is hardly possible to read in an organised way. The content of the text often cannot be understood.

Eye movements are unsystematic

Often the eyes are not moved systematically over the text, making fluent reading impossible.

List of the most important causes

If the eyes are moved regularly, the most common causes of reading disorders are:

• The text segments are not grasped as a whole The reader spells out the word (segment), often even from visual memory
• Fixation phases are too short: The reader does not look long enough As a result, the individual letters are not fully grasped
• The reader tries to grasp segments that are too large As a result, parts of the word are not perceived
• The eyes jump too far There are gaps
• The reader speaks too early.  The processing of what has been seen is not yet complete. 

Seeing correctly is crucial

In order to be able to read correctly, it must always be ensured that the pupil can see properly. Therefore, always have your child’s vision checked by an ophthalmologist. Even in families without a single person who wears glasses, your child may have problems with their vision.

Causes of gaps in reading:

If gaps are left when reading, this has the following possible causes:

The reader is strongly attracted to the future text. As a result, the reader’s gaze jumps too far. This creates gaps in the sequence of letters.

Example:

The reader can recognise 4 letters at a glance. He wants to read the word “Masterpiece” and correctly fixates the a in Masterpiece. He can now recognise the sequence of letters “Mast”. As the text on the right (i.e. the future text) has a strong distracting effect on him and he cannot control this completely, his gase jump goese too far when he now moves his eyes and lands on the i in Masterpiece. He simply omits the sequence of letters er in Masterpiece and ends up reading e.g. “Mastpiece”.

Remedy:

The future text must be completely faded out or made paler in order to weaken the distracting stimulus. By successively moving in the faded text, the pupil trains himself to ignore it.

Causes of reading disorders

In addition to the causes of reading disorders mentioned above, there are other performance deficits that can be the cause of reading disorders or reading weaknesses. In addition to severe visual disorders, hearing disorders and speech disorders, the following 14 disorders caused reading disorders in our controlled studies (Werth 2007, 2018, Klische 2007):

List of all known causes

1. The word or word segment to be read is not fixed in the correct place.
2.  The word or word segment to be read is fixed too short.
3. The individual letters of the word or word segment to be read are recognised. However, the child takes too long or is unable to recall the sound sequence associated with the letter sequence.
4. Only small word segments can be recognised because the field of attention cannot be extended any further. However, the child tries to read larger word segments.
5. Only small word segments can be read because the ability to recognise several letters simultaneously is too weak. However, the field of attention can be extended sufficiently.
6. Too large jumps in gaze are made when reading. As a result, letters, word segments or whole words are often overlooked. The child often guesses the word to be read because it has only partially recognised the word or has not recognised it at all.
7. The visual performance inhibited during the gaze jump recovers too slowly after the gaze jump to read the now fixated word or word segment.
8. The child cannot concentrate its attention sufficiently on reading a word or word segment. They are too distracted by the text around the word or word segment they are reading.
9. The child compulsively keeps looking at words or word segments that have already been read correctly to check whether they have read correctly. This prevents fluent reading.
10. The child can read, but cannot grasp the content of what they have read. They have to focus all their attention on the reading process and can therefore no longer pay attention to the content.
11. The child can read, but cannot memorise the meaning of the words read for long enough. As a result, they are unable to grasp the content of a text. This performance weakness is caused by a reduced memory for the words read.
12. Words read cannot be linked to a meaning or the meaning cannot be recalled quickly enough from memory. This almost exclusively affects children who read a text that is not written in their native language.
13. Pronounceable pseudo-words can be read correctly. However, words in an existing language are often read incorrectly because the child cannot recall the pronunciation rules quickly enough from memory and/or apply them to the pronunciation of the word seen. This almost exclusively affects children who read a text that is not written in their native language.
14. Although words are correctly analysed by the visual system, the sounds of the individual letters are correctly recalled from memory and the word can be pronounced correctly, the sound sequence of the entire word cannot be formed correctly when the word is presented visually.