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Reading difficulty and glaucoma

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Tommy Cleary
BS(Anatomy) BOptom MA(Research)
PhD Student, University of Notre Dame Australia
Honorary Fellow, Australian Health Research Institute, University of Wollongong

 

CASE REPORT

When people have difficulty reading, it is common for them to attend their primary care optometrist for assistance. DC, an 85-year-old woman who describes herself as an avid reader, had noticed that she was not reading as easily as in the past and requested a review of her vision.

Clinical findings

Her BCVA was 6/9 R and 6/9- L with her current bifocal spectacles, which she preferred to use for reading rather than her single vision near spectacles of the same prescription.

She had a mild cataract in the RE and the LE was seeing better following a successful cataract operation and intraocular lens insertion three years previously. Despite this her RE was dominant and her LE had mild exotropic amblyopia and ptosis, which reduced her BCVA slightly in that eye, with no diplopia reported for distance or near fixation.

She had known glaucoma in both eyes with marked glaucomatous notching inferiorly RE > LE (Figure 1).

Ph -165 Figures 1A And 1B_OL
Figure 1. Right optic disc with marked glaucomatous damage (L) and left optic disc, also with significant glaucoma (R)

Her macular area was relatively stable (Figures 2A and 2B) but there was an Amsler grid defect reported in the RE, to the upper right of fixation.

Intraocular pressures were 16 mmHg RE and 12 mmHg LE, which was controlled by timolol 0.5% BID OU.

Ph -165-Figure -2A_OL Ph -165-Figure -2B_OL

Figure 2A. Right eye was her preferred eye despite vision reduction from cataract and glaucomatous damage

Figure 2B. Left eye was weaker due to longstanding binocular vision issues

Visual field showed relatively central glaucomatous defect of the RE and some glaucomatous nasal step defect in the LE (Figures 3A and 3B).

Ph -165-Figure -3A_OL
Figure 3A. Right eye visual field with fixation intact but with marked altitudinal parafoveal impairment particularly to the right of fixation

Ph -165-Figure -3B_OL
Figure 3B. Left eye visual field with some glaucomatous change and an overall reduction in threshold sensitivity

Conclusions

Although DC was relieved that she did not have signs of macular degeneration and that to a certain extent, her glaucoma management could be improved, without a significant reduction in visual acuity her reading difficulties were difficult to explain. DC found benefit in reading large print in good light and was happy to follow up with her regular ophthalmologist for further surgical and pharmaceutical options for glaucoma control.

Reading is a complicated but rewarding task and recently-identified aspects of vision can help explain some of DC’s difficulties. Glaucoma has been associated with ‘slower reading and increased reading impairment with advanced bilateral field loss’.1

There is experimental evidence of an age-related decline in extra foveal letter perception with age.2 With DC, both the effects of age and glaucoma are important to consider as skilled reading in particular is understood to involve the processing of upcoming words in the parafovea.3

DC’s paracentral glaucomatous scotoma may explain some of her reading difficulties because even though vision at fixation is relatively intact, her scotoma masks surrounding words and thus interferes with the oculomotor and perceptual processes4 that are active before a word is fixated.

Further research in this field will help people with both foveal and parafoveal impairment understand the reduction in their reading ability and regain their reading fluency.

 

  1. Cerella J. Age-related decline in extrafoveal letter perception. J Gerontol 1985; 40: 6: 727-736.
  2. Ramulu PY, West SK, Munoz B, Jampel HD, Friedman DS. Glaucoma and reading speed: The Salisbury Eye Evaluation Project. Arch Ophthalmol 2009; 127: 1: 82-87.
  3. Schotter ER, Angele B, Rayner K. Parafoveal processing in reading. Atten Percept Psychophys 2012; 74: 1: 5-35.
  4. Veldre A, Andrews S. Parafoveal preview benefit is modulated by the precision of skilled readers’ lexical representations. J Exp Psychol Hum Percept Perform 2015; 41: 1: 219-232.


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