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

Fig. 5.7 a Tonometric calibration curve in the eye of a newborn. b. Tonometric calibration curve in the eye of a child of three and a half months. The solid lines correspond to the calibration made by Schiötz in the adult; the circles, to the weight

of 5.5 g; the crosses, to a weight of 7.5 g, and the triangles to a weight of 10 g [7]. As can be seen, the ocular rigidity is completely different from that of the adult. This is why it is advisable not to use the Schiötz tonometer in children

vented the Bell phenomenon, according to the blepharostat opening, by waiting for 1 min after placing it. They instilled up to two topical anesthetic eyedrops, to achieve complete relaxation. In some babies, they failed to achieve complete relaxation and repeated their attempt some hours later or on another day.

With this method, they were the first ones in the world after us to present a group of 60 normal newborns with a mean intraocular pressure of 11.4 ± 2.4 mmHg. They presented a table (Table 5.5) listing all the authors who had measured intraocular pressure in children up to the moment of their publication.

This table, as well as Radtke’s paper, shows that the first six authors, out of a total of nine, used only

the Schiötz indentation tonometer (with the abovementioned consequent errors), and the other authors, including Radtke, were the first to use applanation tonometry.

The importance of Borrone’s paper [22] should also be stressed, in which the intraocular pressure of 50 normal children between 5 and 15 years of age was studied, finding the following values: between 5 and 8 years, 8–11 mmHg; 9–11 years, 12–14 mmHg; and 12–15 years, 15–17 mmHg. If the values of the entire group are taken into account (population mean), an intraocular pressure mean ranging from 11.65 to 12.02 mmHg was obtained.

Draeger’s Home Tonometry

Draeger [23] proposed performing a home tonometry in children operated for congenital glaucoma between 5 and 8 years of age, as well as the measurement made by the ophthalmologist, especially when the children live far from the clinic. This tonometry measurement was taken by members of the patient’s family. They learned “under close supervision the correct handling of the applanation tonometer. If marked variations in IOP were found, more frequent checks were made in order to enable early intervention by the doctor. In several cases of congenital glaucoma, it was the parents who carried out the IOP measurement in their schoolage children. In one of the cases, this was done by the wife and in another by the step-mother who was the patient’s doctor.”

Draeger goes on to relate a “particularly striking case: an 8 year-old patient with refractory congenital glaucoma. Extreme oscillations of the IOP were detected early that necessitated a fresh surgical intervention” (Fig. 5.8a,b). Similarly, six more operations were

indicated until finally the IOP was regulated and the progression of the eye disease was stopped.

In the case of children over 8, Dr. Draeger provides them with the Self Tonometer: Ocutome, that he had designed, so that they can check the state of their IOP personally (Fig. 5.9).

Finally, in those operated for congenital glaucoma between 10 and 40 years of age, we have always checked the IOP by means of a daily pressure curve with its own algorithm [5]. We make the curve taking the pressure in bed at 0600 hours with the patient lying in the supine position with a hand applanation tonometer, and then with the patient mobile, with the slit-lamp at 0900, 1200, 1500, 1800, and 2100 hours. The arithmetic mean and the standard deviation (variability) are calculated, which must not pass the limits of 19.1 and 2.1, respectively, the highest normal values (see Vol. 2, Chap. 15). A very interesting example of the IOP value in late congenital glaucomas in a child that I operated in both eyes at the age of 6 years can be found in Chap. 17 (Fig. 17.34–17.37).

Fig. 5.9 Child operated for congenital glaucoma personally checking his IOP using the Self Tonometer: Ocutome (courtesy of J. Draeger)

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 camérulaire chez l’enfant normal et dans le glaucome congénital aux dessous de l’âge de 5 ans. Doc Ophthalmol 26:497–515

3.Sampaolesi R, Reca R, Carro A, Armando E (1975) Estado actual del estudio continuado de la presión ocular de los 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 (1974) Normaler Intraokularer Druck bei Kindern bis zu 5 Jahren mit und ohne Allgemeinnarkose. Seine Wichtigkeit fur die

Fruhdiagnose des angeborenen Glaukoms. In: Glaukom Symposium Wuerzburg 1974, Enke, Stuttgart, pp 278–289

5.Sampaolesi R, Calixto N, de Carvalho CA, Reca R (1968) Diurnal variation of intraocular pressure in healthy, suspected and glaucomatous eyes. First South American Symposium on Glaucoma, Bariloche 1966. Mod Probl Ophthalmol 6:1–23

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

7.Ytterborg J (1960) On scleral rigidity. Oslo University Press, Oslo

8.Friedenwald JS (1955) Tonometer calibration: an attempt to remove discrepancies found in the 1954 calibration scale for Schiotz tonometers. Trans Am Acad Ophthalmol Otolaryngol 61:108–122

9.McBain EH (1957) Tonometer calibration: determination of Pt formula by use of strain gauge and recording potentiometer on enucleated normal human eyes. AMA Arch Ophthalmol Chicago 57:520–531

10.McBain EH (1958) Tonometer calibration II. Ocular rigidity. Arch Ophthalmol Chicago 60:1080

11.Prijot E (1958) La rigidité de l’oeil humain. Acta Ophthalmol 36:865

12.Kornblueth W, Aladjemoff L, Magora F, Gabray A (1959) Influence of general anesthesia on intraocular pressure in man. Arch Ophthalmol Chicago 61:84–87

13.Kornblueth W, Abrahanamow V, Aldjemoff L, Magora F, Gomgos (1962) Intraocular pressure in the newborn measurable under general anesthesia. Arch Ophthalmol Chicago 67:750–752

14.Horven I (1961) Tonometry in infants. Acta Ophthalmol 39:911–918

15.Manzitti E (1963) Técnica de examen en el glaucoma infantil. Arch Oftal B Aires 38:345–347

16.Manzitti E, Damel A (1964) Valores de la tonometría aplanática en el lactante normal. Arch Oftal B Aires 39:360–362

17.Degenne S, Benck P, Gerhard JP, Payeur G, Roth A (1967) Les modifications de la Po chez l’enfant sous anesthésie générale. Bull Soc Ophtal France 67:1118–1121

18.Hetherington JJ, Shaffer RN (1968) Tonometry and tonography in congenital glaucoma. Invest Ophthalmol Vis Sci 7:134–137

19.Grote P (1975) Augeninnendruckmessungen bei Kleinkindern ohne Glaukom in Halothanmaskennarkose. Ophthalmologica 171:202

20.Goethals M, Missotten L (1983) Intraocular pressure in children up to five years of age. J Pediatr Ophthalmol Strabismus 20:49

21.Radtke ND, Cohan BE (1974) Intraocular pressure measurement in the newborn. Am J Ophthalmol 78:501

22.Borrone RN (1984) Presión ocular en niños de 5 a 15 años. Arch Oftal B Aires 59:219–234

23.Draeger J (1992) Neue Wege zur Fruhdiagnose und Verlaufkontrolle des Glaukoms, Spektrum Augenheilkd 6:267–272

Introduction

It is well known that the diagnosis and surgical indications for congenital glaucoma depend on three elements: (1) clinical symptoms, (2) intraocular pressure measurement with applanation tonometry [1, 2], and

(3) chamber angle examination.

In 1970, since I was concerned about intraocular pressure readings for children under general anesthesia, because of the deviations produced by different anesthetic agents, and given that Penthrane, one of the only anesthetics that did not modify intraocular pressure, was about to be discontinued, I decided to test a Siemens echograph for measuring the axial length in the eyes of children with congenital glaucoma symptoms, and I found it useful. The first echograms I obtained are shown in Fig. 6.1.

I used Gernet and Hollwich’s curves [3] and the first papers of Buschmann and Bluth [4] for normality patterns. Then I bought the first echograph used in Argentina. I went to Spitz, where the company that manufactured the echograph designed by Ossoinig was located, and Dr. Till standardized my echograph.

Since 1966, after the first Glaucoma Symposium was held in Bariloche, the Glaucoma Club has continued working on a multicenter basis (Nassim Calixto in Belo Horizonte, Celso Carvalho in Sao Paulo, and myself in Buenos Aires). I purchased two Draeger hand applanation tonometers and took them to my two Brazilian colleagues, and I persuaded each of them to buy a Kretz echograph so that we would be able to conduct a joint study on intraocular pressure and echometry in the diagnosis and follow-up of congenital glaucoma.

Since 1971, I have been using echometry in congenital glaucoma eyes and I have found that, in cases where intraocular pressure readings were suspect because they did not deviate much from normal values, echometry seemed to be a useful new tool. This encouraged us to conduct a systematic study of ocular echometry in normal children in order to establish the mean values and their deviation according to age. We also studied a group of congenital glaucoma patients who were given echometry in addition to the routine examination under general anesthesia. This allowed us to compare the diagnostic value of echometry with that of tonometry.

The proceedings of the Glaucoma Symposium held in Würzburg in 1973 were published in 1974. This book includes one of my papers on the early diagnosis of congenital glaucoma, and on p. 287 [2], for the first time, the usefulness of echography in the early diagnosis of congenital glaucoma is discussed (“Beispiel

Fig. 6.1 Echogram of the glaucomatous right eye (top) and of the normal left eye (bottom) arranged as mirror images

für die Nützlichkeit der Echographie”: Examples of the usefulness of echography). In this paper, I reported a case in which intraocular pressure values are repeatedly suspect in a child with symptoms of congenital glaucoma and transparent corneas. Figure 6.1, which is a reproduction of Fig. 9 of that paper, is the echogram of this case showing that the eye with symptoms had an axial length of 14.5 mm, whereas its fellow eye measured 12.56 mm.

In 1980, at the 8th SIDUO Meeting, I presented a paper that was published in the book Documenta Ophthalmologica Proceedings Series 29, titled “Ocular echometry in the diagnosis of congenital glaucoma” [5].

In 1982, in cooperation with Dr. Caruso, I had the continuation of this paper published in the journal

Archives of Ophthalmology [6]. In 1982, at the International Glaucoma Society Meeting, I presented a paper that was later published in the book Glaucoma Update II, titled: “Ocular echometry and the diagnosis of congenital glaucoma and its evolution” [7]. A. Tarkkanen (Helsinki University Central Hospital, Finland) and G.L. Spaeth (Wills Eye Institute, Philadelphia, PA, USA), respectively, made the following comments on the paper:

I congratulate the author on this excellent paper. Our experience is in agreement with the findings presented. The problem in borderline cases of infantile glaucoma is that the estimates of the intraocular pressure are inaccurate. Applanation tonometry has never been calibrated against infantile corneas in glaucomatous eyes. Our experience of echometry in 20 cases aged from 4 to 48 months shows that the axial lengths in eyes with infantile glaucoma are greater than those of normal controls. Some of the borderline cases show an increase in axial length not attributable to normal growth. After surgery, an early decrease in the axial length down to 0.8 mm has also been noted. The anterior measurements, however, remained unchanged while only the post-equatorial readings showed alterations.

We are impressed with the value of performing ultrasound examinations on children with congenital glaucoma. The test is a very important addition to the other tests that are used in the diagnosis and treatment of children with, or suspected of having, congenital glaucoma. The author is to be congratulated for this important advance.

Reibaldi [8], Tarkkanen et al. [9], Calixto and Cronemberg Sobrinho [10], and Carvalho and Betinjane [11] confirmed the reliability of this method.

During the 12th SIDUO Meeting, Fledelius [12] said that, in the pediatric service he headed in Copen-

hagen, he had always obtained unreliable false values when measuring intraocular pressure in congenital glaucomas under general anesthesia. He had been very pleased when he read our Nijmegen paper and since then he has been performing only echometries instead of measuring intraocular pressure.

In order to apply echometry to the diagnosis and follow-up of congenital glaucoma, we carried out the following study with normal children with the aim of finding out the values of axial lengths in developing normal eyes and in congenital glaucomas.

Echometry

Material

The first group comprised normal eyes (without ophthalmic symptoms and showing normal applanation tonometry values): 33 eyes of children ranging between 2 and 72 months of age.

The second group was made up of glaucomatous eyes (with characteristic symptoms and pathological intraocular pressure values): 36 eyes in patients ranging from 2 to 24 months of age. This group underwent preoperative as well as immediate postoperative echometry.

The case history plays an important role in the clinical study of a child suspected of having congenital glaucoma. The main factor in this study is the time span between the appearance of symptoms and surgery.

Method

The horizontal corneal diameter was measured. The anterior segment was examined with a biomicroscope, paying particular attention to the chamber angle. The intraocular pressure was measured with applanation tonometry; funduscopy was used to examine the optic nerve, peripheral retina, and macula. The last step involved echometry under cycloplegics.

Echometry Equipment

We used a Kretz 7200 MA echograph (Fig. 6.2a) with a 10-Mhz probe, Ocuscan (SonoMetric Health, Inc., Salt Lake City, UT, USA) (Fig. 6.2b), B Scan S (Quantel Medical, Clermont Ferrand, France) (Fig. 6.2c), or Ocuscan RXP (Alcon Laboratories, Fort Worth, TX, USA) (Fig. 6.2d). We are currently developing a special module for congenital glaucomas for this device. This new module will not only provide information on axial

length, but will also place this information on the normal eye growth chart in order to determine whether the value is normal or pathological.

An immersion device consisting of a plastic cylinder (Ossoinig Scleral Shell No. 20 manufactured by Hensen Ophthalmic Development Laboratory, Iowa City, IA, USA) (Fig. 6.3a) is fitted to the sclera and four drops of 4,000-centipoise viscosity methylcellulose 2.5% are first instilled in it to seal off the scleral contact area.

The cylinder is then filled with isotonic saline solution. Under general anesthesia (Fig. 6.3b), with the child in the dorsal position, our method enables the eye to be accurately centered, an absolute prerequisite to correct measurement. The probe is then inserted into the cylinder without touching the cornea, up to approximately 0.5 cm from it, thus obtaining echograms at tissue sensitivity and measuring sensitivity.

We take four echograms for each eye.

Figure 6.4 shows a characteristic echogram in which measurements are taken with dividers with the points placed on the base line of the echogram, precisely on

the point where each echo arises. Thus the chamber angle, lens, and vitreous body are measured.

Only in cases with corneal edema is the pertinent value taken into consideration, as measured from the two echograms corresponding to the anterior and posterior corneal surfaces; otherwise, a mean value of 0.5 mm is assigned.

With the Ocukretz, the axial length is calculated by the echograph itself, according to the mean sound velocity, and the values appear on the monitor. The peaks representing the cornea, the anterior and posterior surface of the lens, and the posterior ocular wall should be the same height in order to obtain a good measurement. The posterior peak representing the ocular wall should be perfect. It should be perpendicular and start directly at the baseline, with no minor peaks in front of it. The measurement should be performed at measurement sensitivity, i.e., 17 dB.

Since the values are obtained in microseconds, they are converted into millimeters on the basis of the sound velocity in the different transparent media [13]. With

Fig. 6.3 a Plastic cylinder for echometry (Ossoinig Shell). b To perform echometry, the plastic cylinder is placed on the sclera with some drops of methylcellulose in order to fix it to the sclera. The cylinder is filled with saline solution and when measuring, the proximal edge of the probe should be separated from the corneal vertex by at least 0.5 cm. c This sketch correlates the measurement method with the echogram obtained; s probe; c plastic reservoir; h saline solution in the reservoir.

these data, we have built a program for a small Hewlett Packard computer used to calculate the following echometric parameters:

I.Corneal thickness

II.Anterior chamber depth

III.Lens thickness

IV. Vitreous body length

V.Axial length

The echogram obtained has been reproduced below; co cornea, i iris, cr1 anterior surface of the lens, cr2 posterior face of the lens, e posterior wall of the eyeball, d echogram obtained. To obtain good results, it is critical for the peaks representing the anterior and posterior corneal surface, anterior and posterior lens surface, retina, choroid, and sclera, to be at the same level, when the measurement sensitivity is 17 dB

Anterior chamber

VI. Axial length

VII. VitreousAnterior segment (cornea + anterior chamber + lens)

Cornea + anterior chamber VIII. Vitreous

Fig. 6.4 The echogram measures the distances between the posterior corneal surface and the anterior lens surface, between the anterior and posterior lens surface and between the posterior surface of the lens and the retina, in microseconds. Sometimes, in the presence of corneal edema, the distance between anterior and posterior corneal surface is also measured. The use of callipers is very helpful in these measurements

Parameters VI, VII, and VIII are three different indices. It should be taken into account that the axial length is made up by adding I + II + III + IV + the retinal thickness, which is considered a constant, equivalent to 0.35 mm [14].

Statistical Methods Used

The minimum square method was used for the growth curves of normal and pathological eyes according to age. The statistical significance of the echometric differences between groups was calculated by means of the Student t test.

Results

Correlation Between Axial Length

and Age in Normal Eyes

A logarithmic growth curve of the population of 36 eyes studied was made according to: y = a + b (log x), using the following formula:

y = 18.7 + 1.245 (log x)

where y is the axial length in mm, and x the age in months.

The correlation coefficient r is 0.9044 (p < 0.001) and the significance of the regression coefficient b is t = 11.82 (p < 0.001). The confidence intervals of the line have also been calculated (for each normal eye studied), as well as the prediction confidence interval for the population of normal children (Table 6.1).

Value of the Prediction Confidence Interval for Normal Eyes in the Differential Diagnosis Between Normal and Glaucomatous Eyes

Figure 6.5 was constructed using the values in Table 6.1. The ordinates show the axial length of the eye in millimeters, and the abscissas, the child’s age in months, in logarithmic scale. This is why a straight line, rather than a curve, is obtained.

The dotted band represents the normal range: the values between the mean and standard deviations, upward and downward. The value of this method can be observed in the first statistical analysis presented (Fig. 6.6), where we have included the axial lengths of the 79 eyes with congenital glaucoma. This demonstrates the usefulness of the prediction confidence interval for normal and glaucomatous eyes.

Comparison Between the Echometric Values

of the Normal and Congenital Glaucoma Groups

The axial length in normal and in glaucomatous eyes belonging to children up to 2 years of age was presented in the previous section. We will now compare the echometric values of the two groups. First, we will analyze the length or thickness of each of the transparent media independently and then the three indices which can relate these transparent media to each other.

Table 6.2 shows that the measurements of the anterior chamber, vitreous length, and axial length are significantly higher in the population of glaucomatous children. This was previously shown by Gernet and Hollwich [3] and Espildora Couso [15] and explains the influence of elevated IOP on a distensible eye.

The most interesting finding, in our opinion, is the behavior of the lens, which is significantly thinned in the population of glaucomatous eyes. This is an important issue, which contributes to the emmetropization of the glaucomatous eye, whose axial length, if considered in isolation, would justify lower myopia values than those found clinically (the rest of the emmetropization factors are corneal flattening and posterior displacement of the lens via the deep chamber).