Prematurity and Vision
Friday 3 March 2006
The optical complications of Retinopathy of Prematurity
Jeff Mason, Optician
Princess Alexandra Eye Pavilion, Edinburgh
There are 3 main optical complications with ROP
- Impact on field of view
- Myopia (shortsightedness)
- Glare
Visual fields (field of view)
- Full visual fields cover an arc of approx 180 degrees.
- This is achieved using both eyes.
- The fields overlap and interrelate.
Further complications!
The receptors in the retina pick up:
- Contrast and movement
Rods – mainly but not exclusively in the periphery - Colour and detail
Cones – mainly but not exclusively in the macula
ROP’s effect on fields
ROP affects the retina in 3 ‘zones’ which are affected depending on the level of ROP
- Zone 3 is in the peripheral retina
- Zone 2 is in the mid retinal area
- Zone 1 is in the macular area
Consequences
- 'Bits' of the field of view don’t work;
- Some other 'bits' do;
- A child may miss the obvious ;
- But will see the difficult ;
- Tracking is difficult;
- These anomalies are very hard to measure;
- They are different for different individuals;
- Different individuals use/interpret the information differently.
Peripheral field loss
Tracking
The loss of field continuity makes it difficult for the individual to track text across a page.
This can be helped with:
- Bar magnifiers
- CCTV
- Typoscopes
Bar magnifiers aid tracking
CCTV
Typoscopes
Angled workboard
- Many children with ROP have a lower field defect;
- They can trip over things;
- Have difficulty placing objects on surfaces;
- An angled workboard can help.
General optical help
Other than the specific aids mentioned there are many types of magnifiers which can help boost the image size – even with very young children.
- Hand magnifiers
- Stand magnifiers
- Illuminated magnifiers
- Computer systems
Hand magnifiers are
- Small and inconspicuous
- Reasonably cosmetically acceptable
- Easy to use
- (Relatively) cheap to replace
Stand magnifiers
- Provide a static image
- Are reasonably robust
- Can sometimes be written under
- Are reasonably economical
Illuminated magnifiers
- Have their own light source for poor illumination scenarios
- Compact
- Cosmetic
- Reasonably economical
- Are usually available in stronger powers
Myopia (Short-sightedness)
ROP changes in the retina can make the eye myopic.
This means distant objects are blurry.
The myopia can be different in each eye.
- If the myopia is different in each eye different image sizes will be formed in each eye.
- This can upset perception.
- Could be helped with a contact lens.
- Not usually very viable due to other ocular factors.
Glare
The physiological changes in the retina caused by ROP.
- Cause an unevenness of the retina.
- Cause a haziness in the ocular media.
This means incoming light is scattered around the inside of the eye causing dazzle and glare.
Glare solutions
- Sunglasses/tinted lenses
- Peaked hat
Conclusions
Optical effects of ROP vary greatly between individuals.
The impact of ROP on field of view is very variable and very hard to evaluate.
If individuals are myopic spectacles should be worn.
Glare protection helps.
A multi-disciplinary, pragmatic approach is best.
Children are flexible and adaptive, they often do better than expected.
Contact
Jeff Mason - Optician
c/o LVA Clinic
Princess Alexandra Eye Pavilion
Chalmers St.
Edinburgh
Email: J.L.Mason@Bradford.ac.uk