OVERVIEW: What every practitioner needs to know

Are you sure your patient has refractive errors? What are the typical findings for this disease?

Some of the most common vision problems presenting in childhood are related to refractive errors. Patients typically present in a clinic setting having failed a school screening exam or due to commonly reported symptoms including:

1. Blurry vision

2. Sitting too close to nearby objects

3. Squinting

4. Difficulty reading or performing in school

Cause of refractive errors

Refractive errors are commonly caused by the failure of normal emmetropization of the eye. Subsequently, the axial length of the eye can become either too long or too short for the image to focus correctly on the fovea, or corneal or lenticular growth may be asymmetric or inappropriate for the optical system to work properly.

Results of failed emmetropization

1. Hyperopia- Images focused behind the retina due to a short eye or insufficient convergence of light through the cornea or lens. Results in increased accommodative effort on the eyes, potentially blurring objects at near, contributing to esotropia, or asthenopia.

2. Myopia- Images focused in front of the retina due to a longer eye or excessive convergence of light through the cornea or lens. Results in blurred objects at distance that cannot be brought into focus without spectacle correction.

3. Astigmatism- Asymmetric refraction at different meridians caused by an irregular curvature of the refracting surfaces of the eye. Images are subsequently focused in two or more separate points, resulting in a blurred image on the retina.

4. Anisometropia- Disparate refractive error between the two eyes. If significant, can lead not only to blurred vision, but poor stereopsis and amblyopia.

What other disease/condition shares some of these symptoms?

Many other ocular diseases can lead to visual impairment. It is imperative that any child suspected of having inappropriate visual acuity be referred for a full examination by an ophthalmologist to rule out underlying causes. Examples include: Retinopathy of Prematurity, Congenital Cataracts, Congenital Glaucoma, Retinoblastoma, Optic Atrophy, or other congenital syndromes resulting in obstruction or inappropriate visual development

What caused this disease to develop at this time?

• As noted above, failure of emmetropization is the primary cause of refractive errors.

• Genetics- Refractive errors do not follow typical Mendelian inheritance. They are complex multifactorial interactions with significant variability.

• Environmental- Increasing near work and schooling is known to contribute to the development of myopia. Eye rubbing may cause astigmatism. Myopia and Astigmatism may both be caused by forces causing asymmetric pressure on the anterior surface of the eye (eyelid ptosis, lid lesions, limbal dermoids, etc.)

• Multiple childhood syndromes and diseases have known refractive error associations. Presentation with solely ocular complaints does not preclude the need for a thorough evaluation of the overall health of a pediatric patient.

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

• Unless findings on examination suggest an underlying disease or syndrome, lab studies for refractive error are unnecessary.

Would imaging studies be helpful? If so, which ones?

• Imaging studies are of no value in managing true refractive errors

Confirming the diagnosis

• Clinical decision algorithms are unnecessary for refractive errors in a primary care setting.

• It is known that eye and vision screening is an effective tool to identify abnormalities in visual development, and are most effective when performed periodically. Guidelines on the optimal timing and methods for such screens have not been definitively established. Concern for any visual impairment, at any age, by the provider should prompt referral to an ophthalmologist for a comprehensive eye exam.

If you are able to confirm that the patient has refractive errors, what treatment should be initiated?

• Refer to an ophthalmologist for a comprehensive eye exam.

What are the adverse effects associated with each treatment option?

N/A

What are the possible outcomes of refractive errors?

Failure to properly treat significant refractive errors during emmetropization may lead to amblyopia and permanent visual impairment.

The long-term need for spectacle correction is highly variable. Final visual outcomes are best discussed between the patient and ophthalmologist.

What causes this disease and how frequent is it?

• It is estimated that 5% to 7% of preschool aged children have visually important refractive errors.

• The prevalence of myopia is 9%, hyperopia 13%, and astigmatism 28% in children between the ages of 5 to 17.

• It is felt that 25% of school age children have a refractive error that would benefit from correction.

How do these pathogens/genes/exposures cause the disease?

N/A

Other clinical manifestations that might help with diagnosis and management

N/A

What complications might you expect from the disease or treatment of the disease?

N/A

Are additional laboratory studies available; even some that are not widely available?

N/A

How can refractive errors be prevented?

Several therapeutic regimens to reduce the progression of myopia have been postulated, but to date are unproven and controversial.Because of the dynamic process of emmetropization, some refractive errors are temporary in nature, and may resolve with time.

What is the evidence?

"Preferred Practice Pattern® Guidelines. Pediatric Eye Evaluations. Tables 2 and 3". American Academy of Ophthalmology. 2007. http://www.aao.org/ppp.

Ongoing controversies regarding etiology, diagnosis, treatment

N/A