Ординатура / Офтальмология / Английские материалы / Textbook of Visual Science and Clinical Optometry_Bhattacharya_2009

Paediatric Eye Examination 283

•The infant is held at arm’s length and rotated to elicit vestibuloocular nystagmus. Slow phase of nystagmus occurs towards the direction of the rotation. Normally on stopping the rotation/ spinning, the nystagmus should stop quickly due to presence and action of fixation reflex.

Optokinetic Nystagmus (OKN)

•Nystagmus is a physiological reflex elicited by the attempt to maintain fixation on a moving set of alternate, vertical, uniform black and white stripes (optokinetic drum).

•It is demonstrable in infants just a few hours after birth.

•It is simple and may be used as a rapid screening test for assessing gross integrity of the visual system.

•Presence of optokinetic nystagmus (OKN) provides evidence of vision.

Forced Choice Preferential Looking (FCPL)

•It is based on the natural tendency of an infant to look preferentially at a patterned target than a plain one.

•It is a psychophysical test and depends on child’s motor response.

•The infant is presented with Teller Test Cards containing two targets, a patterned one and a homogeneous one at a distance of 55 cm. The examiner observes the eye movement of the infant through a central peephole. Teller Test Cards set consists of 16 rectangular grey cards (26 cm × 56 cm). 15 of the cards contain a high contrast square-wave grating (12 cm × 12 cm), each of a given spatial frequency (from 0.3 to 38 cpd), either on the left or right side of the central peephole. The procedure starts with presenting the card with the lowest spatial frequency, i.e. coarser grating and proceeding to cards with finer gratings. The examiner makes an assessment, based on the infant’s head and eye movements and the finest grating card the child is able to resolve. The spatial frequency of that particular card represents the visual acuity of the infant.

•FPCL is particularly useful in infants between 3 to 12 months of age, although it can be tested on children upto 3 years of age.

284 Textbook of Visual Science and Clinical Optometry

Stycar (Screening Test for Young Children and Retards) Rolling Ball

•Ten white spheres from 3.5 mm to 6 cm in diameter are rolled across in a well-lit room across a contrasting floor 3 metre from the child.

•Presence of pursuit eye movement implies presence of reasonable good vision.

Visual Evoked Potential (VEP)

•In normal infants, pattern–evoked visual potential testing (discussed in detail in chapter–5) demonstrated that equivalent of 6/6 (or 20/20) vision is achieved during six months and one year of life.

•However, FPCL suggests this 6/6 (or 20/20) visual acuity is achieved between one and three years of life.

SUBJECTIVE TESTS

•A variety of methods/charts/cards are available for different age groups for subjective assessment of distance visual acuity using optotypes, i.e. a symbol whose identification implies certain level of visual acuity. The suggested distant visual acuity test in different age groups are (Table 18-1):

Table 18-1: Subjective tests in different paediatric age group

•Cardiff Acuity Test Cards and Kay’s Picture Test consist of a series of cards, each with different pictures of a dog, a duck, a fish, a car, a house, etc. The viewing distance is 3 metre. The children are required to match the optotype letter/picture on a card shown by the examiner.

Paediatric Eye Examination 285

•STYCAR letter test is based on the letters first recognised by children (H, O, T, V and X).

•Sheridan Gardiner Test is similar in principle, adding two letters U and A, i.e. H, O, T, V, X, U and A.

•Visual acuity should be tested at distance and at near, using tests with the same optotypes. Recommended distance is 6 metres (or 20 feet). However, in children the test distance is 3 metres (or 10 feet) for distance acuity and 40 cm (or 16 inches) for near acuity.

•If amblyopia is suspected, Snellen’s visual acuity chart or Cambridge Crowding Cards should be used to assess visual acuity. Because isolated optotypes will overestimate the visual acuity in amblyopic eyes.

VISUAL FIELD TESTING

•Humphrey visual field automated perimeter is used for older children.

•Confrontation method is used in younger children. One toy is used for central fixation attention, while other toy is introduced into their visual field periphery.

COLOUR VISION TESTING

•Colour vision test often helps in the diagnosis of diminished visual acuity in children.

•It also helps in monitoring progressive macular disease and optic neuropathy.

•Usually, red-green colour defects are caused by optic nerve diseases and acquired blue-yellow colour defects are caused by retinal diseases (see chapter–5 for colour vision testing in details).

OCULAR MOVEMENTS

It is easily done in infants and young children by the following tests:

Paediatric Eye Examination 287

BINOCULAR VISION TESTING

•Presence of simultaneous macular perception, fusion and stereopsis indicates good visual acuity in each eye.

•They may be assessed using Worth 4 dot test, Titmus fly test and synoptophore.

•The Lang and Frisby tests are conducted for testing young children.

CLINICAL EXAMINATION OF THE EYE PROPER

•Examination of ocular adnexa.

•Examination of pupil–Normal pupillary reactions are present by the age of 3 (three) months.

•Refraction–Children of age group from birth to 7 years of age are at risk of developing squint and or amblyopia due to refractive error. Hence, cycloplegic refraction is very important for accurate estimation of refraction in them.

In children cycloplegic refraction should be done after application of atropine sulphate 1% eye ointment in a schedule of twice daily for 3 consecutive days, prior to the day of retinoscopy. However, parents should be advised to discontinue the ointment if side effects, e.g. fever, flushes and irritability occur. Atropine drops should not be applied in children topically to avoid atropine poisoning by absorption from stomach through nasolacrimal passage. Atropine allergy may also develop which is treated with systemic antihistaminic and topical steroid ointment.

Full refractive correction should be prescribed if hypermetropia is accompanied by esophoria or esotropia. Hypermetropia should be corrected with appropriate glasses to prevent amblyopia. The parents of hypermetropic child may be warned beforehand that the child may complain of blurred vision with the glasses, initially. This occurs because uncorrected hypermetropic child is used to extra accommodative effort to neutralise a portion of his hypermetropia. Usually, after a few days on continuous wearing of the glasses, the accommodation relaxes. However, if the accommodation fails

288 Textbook of Visual Science and Clinical Optometry

to relax, cycloplegic eyedrops are advised temporarily for few days as remedial measure.

However, conventionally myopia should be corrected with weakest concave lens to achieve 6/6 (or 20/20) vision of even if accompanied by exophoria or exotropia. The idea is to stimulate accommodation, convergence and prevent squint.

Amblyopia is more common in hypermetropia than in myopia. However, unilateral myopes are also at significant risk to develop amblyopia. In case of anisometropia of more than 4.00D, contact lenses should be advised in place of spectacles to maintain binocular vision. In children with refractive errors, refraction should be repeated every year.

•Ophthalmoscopy—It is performed using both indirect ophthalmoscope and direct ophthalmoscope.

•Intraocular pressure measurement—Conventionally, IOP measurement in children is done with the Perkins handheld tonometer under topical anaesthesia (0.5% proparacaine HCl) or general anaesthesia. Some examiners prefer Tonopen/Noncontact tonometers over Perkins tonometer (discussed in detail in chapter–16). Goldmann applanation tonometry is usually possible after the age of 6 years.

•Examination under anaesthesia (EUA)—Examination under anaesthesia is often needed for IOP measurement, in uncooperative children, removal of foreign body, ophthalmoscopy, gonioscopy, etc.

MILESTONES—NORMAL VISUAL MATURATION AND REFLEXES

Development of normal visual function is extremely critical in the first 6-8 weeks after birth. This critical period extends upto seven

(7) years of age (Table 18-2). Any deprivation of stimulation during this period in the form of cataract or refractive error may lead to nystagmus and amblyopia. The visual development remains unstable during this period and any stimulation deprivation acquired during this critical period may interrupt visual maturation process. Normal visual development is shown in tabular form (Table 18-2).

Paediatric Eye Examination 289

Table 18-2: Milestones–Normal visual maturation

NORMAL VISUAL ACUITY MATURATION (AGE-RELATED)

Normal age-related visual acuity estimate varies depending upon the test method employed. By the age of 30 months (Table 18-3) it should reach 6/6 (or 20/20). However, pattern visual evoked potential (PVEP) estimates 6/6 vision is achieved between 6-12 months after birth.

Table 18-3: Progression of normal visual acuity

290 Textbook of Visual Science and Clinical Optometry

If a child is amblyopic and is under 7 years of age, the amblyopia can be cured by patching, i.e. occlusion of the eye with better vision. It is observed that at 1 year of age, patching may be successful to cure amblyopia within 1 week. However, it may take a year to achieve the same result if it is started at 6 years of age. Occasionally, after the age of 7 years pleoptics can help restore normal visual acuity in combination with occlusion upto the age of maximum 14 years.

Stimulus deprivation in both eyes results in development of a pendular nystagmus on attempted fixation by the age of 6 months. Hence, it is very important and critical to examine a child with visual complaints and treat as early as possible.