**9. Pediatric eye examination**

There is no consensus on when the initial eye examination in a healthy child should be performed and how often the examinations should be repeated in the presence of normal eyes. Premature infants at risk of retinopathy of prematurity must be screened by an ophthalmologist. Many congenital ocular abnormalities may be diagnosed by simple observation by a pediatrician, if they are aware of the possible congenital ocular diseases.

In developed countries, the initial eye examination by an ophthalmologist is commonly performed at 6 months of age. At this age, the alignment of the eyes and the near focussing

Pediatric Ophthalmology / Eye and Disorders 13

The total refractive power of the human eye is approximately 60 diopters (D). The cornea provides two thirds of this total power and the lens provides the remaining 20 D. The normal eye creates clear images by focusing the images on the retina. If the unaccommodated eye focuses the images behind the retina, hperopia (farsightedness) develops. On the other hand myopia (nearsightedness) is the state in which the unaccommodated eye focuses the images in front of the retina. The hyperopia and myopia may be due to altered total refractive power of the eye, but the axial length changes instead of that is the most common reason in most of the cases. Reduced axial length results in

The parental history of myopia, genetic predisposition and various environmental factors are associated with the development of myopia in a child. Familial predisposition also exists in hyperopia, which is much less common in the pediatric population. The children can tolerate low amounts of hyperopia by accommodation, so most of the low amounts of hyperopia are unrecognized in this population. However, higher degrees may result in

A healthy eye is able to focus all the light rays from a point source to a single point. In the presence of astigmatism, this focusing process to a single point is disrupted due to variations in the curvature of the cornea or lens at different meridians. Most of the astigmatisms are the consequences of alterations in corneal curvatures. In other words, the refractive power of some part of the cornea is higher or lower than the rest of the cornea, so the astigmatism results. If these regions of the cornea with different refractive power capacity are 90 degrees apart, the astigmatism is regular. If these regions are not 90 degrees apart, it is called irregular. Keratoconus is an important reason for irregular

Spectacles, contact lenses, refractive surgery, intraocular lenses and clear lens extraction are the current methods of refractive correction. Refractive disorders place a significant economic and social burden on society. In USA, \$4.6 billion was spent for treatment of myopia in 1990. Spectacles continue to be the safest method of correction, whereas the interventional procedures are very rarely preferred in the pediatric population. Anisometropia refers to a difference in the refractive status of the 2 eyes. If the difference is 2 diopters or more, either spherical or astigmatic, it is clinically significant. Anisometropia should be managed with caution, since it is the most important risk factor

A physician must be aware of the definition of amblyopia properly to understand the importance of early diagnosis and management of amblyopia. Amblyopia is the combination of two Greek words; amblyos – blunt and opia –vision. The parents commonly

hyerpopia and the reverse in myopia (Riordan-Eva, 2004).

amblyopia and should be corrected promptly.

**10.2 Etiology** 

astigmatism.

**10.3 Management** 

for amblyopia.

**11. Amblyopia 11.1 Definition** 

of the infant can be checked. An infant should be able to fix and follow faces within 2-3 weeks of age (Allen, 2000). The ability of the young children to fixate and follow a small target is an important gross evaluation of vision. Consistent objection from the child to having one eye occluded suggests that the un-occluded eye is amblyopic. Refraction examination and the red reflex test should be performed. The red reflex test is a screening test for retinal abnormalities and opacities in the visual axis such as congenital cataract and corneal opacities. It is performed by focusing an ophthalmoscope light from 30 cm away from the child's eyes. If the red reflex of the 2 eyes is symmetrical, the test is normal. Dark spots in the red reflex or leukocoria (white reflex instead of red reflex) are indications for referral to an ophthalmologist.

Special tests to confirm that, an infant sees, may be performed. Optokinetic drum test and the spinning test are the most popular simple methods to confirm visual response in an infant. Forced choice preferential looking is a popular way of quantifying infant vision. Portable cards; namely Teller or Keeler cards are used to quantify infant vision. Optotype tests to quantify visual acuity may be used in children between 1-3 years of age. Cardiff acuity cards at 1-2 years of age and Sheridan Gardner optotypes at 2-3 years of age are the most commonly preferred ones. In children over 3 years of age, Snellen acuity charts may be used. Eye movements and the position of the eyes should be simply observed. Hirschberg test, which is a light reflex test, is used to exclude manifest eye deviations. If an infant with manifest deviation fixates the penlight, the corneal reflex will be eccentric in the deviating eye. The reflex will be displaced nasally in the exotropia, and temporally in the esotropia.

Pupils are smaller and poorly reacting in the newborns. Normal pupillary reactions should be documented by 3 months of age. Iris colour is permanent at 1 year of age. Colour vision assessment can be performed by the Hardy-Rand- Rittler plates in children as young as 3 years of age (Mollon et al., 1991). If the child cannot tolerate ophthalmic examination and detailed examination is indicated, sedation can be required. Routine intraocular pressure measurement in cases with congenital glaucoma is an example for such conditions.

Eye examinations after 3 years of age are more informative and more easily performed. Visual acuity assessment and the fundamental parts of eye examinations are similar with the adult patients. However, the physicians should keep in mind that, refractive status of the eye is very dynamic in preschool and school children, and preschool vision screening is recommended for all children.
