Ординатура / Офтальмология / Английские материалы / The Glaucomas Volume 1 Pediatric Glaucomas_Sampaolesi, Zarate_2009

References

1.Sampaolesi R, Reca R, Carro A (1967) Presión ocular en el niño hasta los 5 años bajo anestesia con Pentrane (Metoxifluorane). Arch Oftal B Aires XLII:180–185

2.Sampaolesi R (1969) La pression oculaire et le sinus camerulaire chez l’enfant normal et dans le glaucome congénital aux dessous de l’âge de 5 ans. Docum Ophthal 26:497–515

3. Sampaolesi R, Reca R, Carro A, Armando E (1975) Estado actual del estudio continuado de la presión ocular de los

Fig. 4.19 Examination of the chamber angle with SL-OCT. (see Chap. 13)

niños desde el nacimiento hasta los 5 años de edad. Arch Oftal B Aires 50:321–333

4. Sampaolesi R, Reca R, Carro A, Armando A (1976) Normaler Intraokularer Druck bei Kindern bis zu 5 Jahren mit und ohne Allgemeinnarkose. Seine Wichtigkeit fur die Fruhdiagnose des anegborennen Glaukoms. In: Glaukom Symposium Wuerzburg 1974, Enke, Stuttgart, pp 278–289

5. Ferreira AA, Lobo De Morais L (1965) Emprego do Metoxifluorano en anestesia para otorrinolaringologia e oftalmologia. Rev Brasil Anest 1:143–146

Contents

Tonometers Used for Measuring Intraocular Pressure

in Children . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Tonometers Used for Measuring

Intraocular Pressure in Children

The examination is generally carried out with the child supported at the slit lamp by the anesthesiologist (see Chap. 4). Goldmann’s applanation tonometer is generally used (Fig. 5.1a). Today we also use Pascal’s tonometer, which gives us the pressure corrected for corneal thickness (Fig. 5.1b). After operating, only the ocular pressure and the axial length need to be checked. This can be done on a stretcher while the child is under anesthesia in a supine position. In this case, Draeger’s hand applanation tonometer is very useful (Fig. 5.1c). We sometimes also use the Goldmann hand applanation tonometer (Fig. 5.1d), which is very precise, but there are very few units manufactured by Haag-Streit. The Perkins tonometer can also be used.

Before discussing this subject, the following should -be taken into consideration:

Intraocular pressure measurement is technically - difficult in children up to 5 years of age.

Statistical reports of normal intraocular pressure in - children are scarce worldwide.

The different types of anesthetics available influence intraocular pressure values (see Chap. 4).

Normal Intraocular Pressure

in Children from Birth to 5 Years of Age Under General Anesthesia

In 1967, we established that the normal intraocular pressure in children under general anesthesia with Methoxyflurane (Penthrane) has a mean value (X) below the normal X found in adults [1]: X = 10.56, S = 1.01.

The study involved 48 eyes of 24 healthy children. In 1969, we continued the study with the inclusion of 85 eyes of 48 children, thus extending the statistics, and obtained a mean intraocular pressure for children under general anesthesia of X = 10, S = 2.9. We therefore concluded that intraocular pressure in children is 5 mmHg lower than in adults [2] (Tables 5.1–5.4).

In the study conducted in 1975 [3–5], I extended the statistics to 93 normal children (139 eyes), who had consulted for other disorders not influencing intraocular pressure values. These eyes were divided into six age groups: 63 eyes of children under 1 year; 36 eyes of children within the 1st year; nine eyes of children within the 2nd year; eight eyes of children within the 3rd year, 11 eyes of children within the 4th year, and 12 eyes of children within the 5th year.

The normal intraocular pressure was measured with either the Goldmann-Schmidt, Draeger, or Perkins hand applanation tonometers, with the child in the supine position. In some children, it is sometimes necessary to open the palpebral slit slightly with a lid speculum, which can be easily prepared with a paper clip.

We do not use Halothane. Halothane induces strong blood pressure reductions [6], and therefore a large drop in intraocular pressure.

Normality Criteria

The following normality criteria were taken into account: corneal diameter under 12 mm, normal chamber angle, normal eye fundus, echometry with values within the normal range normal intraocular pressure in normal children until 5 years of age.

In Fig. 5.2, the ordinates show intraocular pressure values in millimeters of mercury and the abscissas, the age in years. This chart should be kept hanging on the wall of the operating room so that, when measuring intraocular pressure under general anesthesia, the ophthalmologist can check whether the readings fall within the normal range. For instance, when measur-

ing intraocular pressure in a child aged 6 months, the mean intraocular pressure should be 8 mmHg, the maximum 14 mmHg, and the minimum 4 mmHg. Values above 14 mmHg or below 4 mmHg are strongly suggestive of hypertension or hypotension, respectively (Figs. 5.2, 5.3).

Table 5.3 Statistical test

F 5.33, 95% = 2.29

F 5.133 = 9.63; p<0.001

Regression of intraocular pressure in relation to age up to 5 years (Fig. 5.2)

Table 5.4 Maximum and minimum intraocular pressures at different ages

y = 8.5 + 0.85 x

y = intraocular pressure

Regression coefficient = 0.85

x = years of age

Mean deviation s y.x = 2.4

Student t test = 6.83; p<0.001

95% confidence interval for normal IOP values until the age of 5 years (mmHg)

Fig. 5.2 The regression line (thick line) shows the annual IOP rise from birth to 5 years of age. On the ordinates, IOP in mmHg. On the abscissas, years of age. This graph is very useful

for physicians, who should have it visible whenever they measure IOP under general anesthesia in children. For example, at 6 months of age, the maximum possible IOP is 14 mmHg

The thick line, the regression line, in the chart, shows the annual intraocular pressure increase which occurs from birth up to 5 years of age (Fig. 5.2). It is very important for the ophthalmologist to understand this concept clearly: intraocular pressure is a variable that steadily increases throughout life, from birth to old age.

We have calculated the normal intraocular pressure values according to age, up to 5 years. The analysis of variation shows that intraocular pressure varies according to age. This is consistent with the significant intraocular pressure increase showed by the regression line at this stage of growth (from 1 to 5 years of age). The regression coefficient shows that intraocular pressure increases by 1 mmHg per year, starting from 8.5 mmHg (actual increase: 0.85 mmHg per year). The intraocular pressure reading should, therefore, be related to the child’s age, in order to set a diagnostic criterion of normal intraocular pressure, which, in children under 2 years of age is 5 mmHg lower than in adults.

Intraocular pressure in children from birth to the 5th year of age shows a slow increase, and Fig. 5.3 shows that intraocular pressure in babies under 1 year of age is 8.9 mmHg. During the 1st year, it is 9.8 mmHg, during the 2nd year, 10.4 mmHg, during the 3rd year, 11.5 mmHg, during the 4th year, 13.3 mmHg, and during the 5th year, 12.5 mmHg. These are the mean values for the different age groups. Intraocular pressure in children is thus seen to be lower than in adults.

Normal Intraocular Pressure in Newborns

Between 12 h and 15 Days of Age

Under Local Anesthesia

and Without General Anesthesia

We have taken many intraocular pressure measurements in newborns without general anesthesia in order to avoid the influence of general anesthetic agents on intraocular pressure. Thus, we have proven that the intraocular pressure values measured in children, which are 5 mmHg lower than in adults, are not caused by the anesthetic agent. The measurement of intraocular pressure in newborns up to 15 days of age can be performed without general anesthesia, using Dr. A. Armando’s method, which is a method for calming down and relaxing the baby in such a way that tonometry can be performed [3].

Material

Fifteen normal babies were studied in the maternity ward (six boys and nine girls), ranging in age from 12 h to 15 days.

Method

Using positions that remind the baby of the fetal position, the baby becomes calm and relaxed, and neither sedatives nor general anesthetic agents are required for intraocular pressure measurement.

There are three positions that make it easier to measure intraocular pressure:

1.The baby is placed in fetal position (Fig. 5.4), with the head upward and the body half flexed, the legs flexed and crossed over the belly, and the arms over the chest. In this position, the baby is held in the arms of the physician or the nurse, who must have one hand on the baby’s head and one under the buttocks while making flexion movements.

2.Then the baby is placed in a supine position, and, holding the baby’s crossed arms with one hand, flexion movements of the crossed and flexed legs are made with the other hand toward the belly (Fig. 5.5a).

3.When the baby is relaxed after these two maneuvers, this condition can be maintained by movements joining and separating the knees, as shown in Fig. 5.5b. Newborns are generally hypotonic, with transient hypertonia of the limbs. This means that newborns tend to have their four limbs flexed. When the baby stops crying and becomes quiet with these maneuvers, two Castroviejo lid speculums are placed, with nylon threads to pull from so that the fingers do not rest on the lids, which may cause the intraocular pressure to rise. This allows a 5- to 7-mm palpebral opening. Local anesthetics and fluorescein are administered and the intraocular pressure is measured with a Draeger hand tonometer (Fig. 5.6a). In our study, we also used a Mackay–Marg tonometer with inscription (Fig. 5.6b).

Without general anesthesia, intraocular pressure in newborns is not significantly different from that of normal children within their 1st year without general anesthesia.

Ocular rigidity. Ytterborg’s studies accounting for children’s intraocular pressure being 5 mmHg lower than in adults

Schiötz´s tonometer should not be used to measure intraocular pressure in children. Although the classical literature already considered that the use of Schiötz´s tonometer in children led to countless mistakes regarding corneal curvature, corneal diameter, etc., the paper giving the reasons why it should not be used in children was written by Ytterborg in 1960 [7]. He explained that:

1.The conversion tables for Schiötz tonometry, like those made by Friedenwald [8], McBain [9, 10], Prijot [11], etc., were based on adults’ eyes, with normal corneal diameters, and so they are not applicable to children.

2.The newborn’s eye has approximately one-third of the adult’s eye volume, the cornea has a more definite curvature, and the ocular walls have a different structure.

3.To prove this, Ytterborg examined 50 eyes enucleated from adults and 16 enucleated from children of different ages. He took tonometric measurements and scleral rigidity measurements with an electromanometer. He found that the scleral rigidity coefficient of children’s eyes is much higher than that of adults’ eyes. This is shown in Figs. 5.7 and 5.8.

The measurement of clinical ocular rigidity in 109 eyes of children between 5 months and 10 years of age under general anesthesia yielded a rigidity coefficient of 0.024. This means that with Schiötz tonometry there is a risk of diagnosing glaucoma when this is not the case. Ytterborg proved that children’s ocular rigidity is double that of adults. In his paper, Ytterborg states, “the lines on the chart represent Friedenwald’s normal calibration curves with 5.5, 7.5 and 10-g weights respectively, according to the 1955 tables (Fig. 5.7). The

values I found deviate significantly from the ones represented by these curves. For instance, a scale reading of 4 using a 5.5-g weight, corresponds to an intraocular pressure of 20.5 mmHg according to the 1955 conversion tables, but, in fact, corresponds to an intraocular pressure value of 11.5 mmHg. The mean pressure for adults is slightly over 15 mmHg. If the intraocular pressure values are the same for newborns, the scale reading, according to these tables, should normally be slightly lower than 3. This scale reading is a strong indication of glaucoma in adults. The difference is even greater if the comparison is made with Schiötz’s pressure curves, whose values are approximately 5 mmHg higher than Friedenwald’s.”

In 1960, Ytterborg studied the ocular rigidity of newborns, without applanation tonometry. He concluded that children’s intraocular pressure, as measured using a Schiötz tonometer, is 5 mmHg lower than the mean for adults. These experimental results were proven later in our clinical papers [1–5].

We highly recommend the papers by Kornblueth et al. [12, 13], Horven [14], Manzitti [15], Manzitti and Damel [16], Degenne et al. [17], Hetherington and Shaffer [18], Grote [19], and Goethals [20] which studied the influence of anesthetic agents on intraocular pressure.

In my opinion, the fundamental work is the study co-authored by Radtke and Cohan [21] because they are the only authors who compared intraocular pressure values of children under general anesthesia and with a new method of their own design in which the child is awake in order to ensure the consistency of these values, thereby ruling out the influence of general anesthesia on intraocular pressure. This paper was the first one to confirm our results in the United States. Their study investigated babies between 19 and 173 h of age, i.e., up to the 7th or 8th day, and they reached the relaxed condition with the baby in its cradle and covered with a blanket to keep it warm. They used a Sauer retractor manufactured by Storz and they pre-