RU2765438C1 - Method for differential diagnosis of keratoconus and congenital myopia with high refractive power of the cornea and astigmatism - Google Patents

Abstract

FIELD: medicine.SUBSTANCE: invention relates to medicine, namely to ophthalmology. The depth of the vitreous body (VBD) is determined - the distance from the posterior pole of the lens to the posterior pole of the eye and the acoustic density of the sclera (SAD) in the region of the posterior pole and in the upper-outer quadrant of the equatorial zone. If the VBD value is less than 17 mm, the SAD in the region of the posterior pole is more than 240 c.u., and in the upper outer quadrant of the equatorial zone, more than 230 c.u. diagnose keratoconus.EFFECT: method allows providing an adequate choice of treatment tactics, depending on the diagnosis of keratoconus or congenital myopia with high refractive power of the cornea and astigmatism.1 cl, 2 ex, 1 tbl

Description

The present invention relates to ophthalmology and is intended for the differential diagnosis of keratoconus and congenital myopia with high refractive power of the cornea and astigmatism.

Keratoconus is a progressive non-inflammatory bilateral disease of the cornea, which is characterized by paraxial thinning of the stroma, while the surface of the cornea is distorted, its shape, optical properties, and biomechanical parameters change. The incidence of the disease varies according to various authors from 1:10000 to 1:100000 (Hashemi Η, Heydarian S, Hooshmand Ε, Saatchi Μ, Yekta A, Aghamirsalim M, Valadkhan M, Mortazavi M, Hashemi A, Khabazkhoob M. The Prevalence and Risk Factors for Keratoconus: A Systematic Review and Meta-Analysis Cornea 2020;39(2):263-270).

It is well known that keratoconus is often characterized by reduced corrected visual acuity, high refraction, and high astigmatism, the same features found in congenital myopia. The pathological basis of keratoconus is the altered collagen of the cornea. As the disease progresses, the amount of collagen produced by keratocytes and its organization decrease, which leads to a decrease in the average diameter of fibrils and the space between them (Vellara, HR; Patel, DV Biomechanical properties of the keratoconic cornea: A review. Clin. Exp. Optom. 2015 , 98, 31-38).

The pathogenetic mechanism of congenital myopia is associated with violations of the biomechanical properties of the scleral capsule (sclera collagen) due to changes in its metabolism and microstructure (Markosyan G.A., Tarutta E.P., Iomdina E.N. et al. Clinical, functional and biomechanical aspects of pathogenesis , Diagnosis and Treatment of Congenital Myopia: A Review of the Literature and Analysis of Own Data, Russian Pediatric Ophthalmology, 2016; 11 (3): 149-57. At the same time, congenital myopia is also characterized by high refraction of the cornea (above 43.0-44.0 diopters) and high astigmatism (up to 6 diopters). The latter circumstance makes congenital myopia similar to keratoconus and, in some cases, in the absence of documented data on the onset of the disease and its course from childhood, makes it difficult to differentiate the two mentioned conditions. It is known that in keratoconus corneal changes progress over time, while in congenital myopia, the parameters of the cornea remain unchanged. It is obvious that dynamic observation contributes to differential diagnosis, which, however, requires from one to several years. Therefore, the development of additional criteria for the differential diagnosis of congenital myopia and keratoconus is relevant.

The main method for diagnosing keratoconus in clinical practice is videokeratotopography of the cornea. In some cases, keratotopographic examination of the cornea does not allow accurate differentiation of keratoconus from congenital myopia and gives a conclusion based on a mathematical analysis of the anterior surface of the cornea on suspicion of keratoconus or subclinical keratoconus.

A known method for diagnosing keratoconus using a Scheimpflug camera (Shi Y. Strategies for improving the early diagnosis of keratoconus. Clin Optom (Auckl). 2016; 8: 13-21). In this method, the approach to the diagnosis of keratoconus is based on the analysis of pachymetry and topography of the anterior and posterior surfaces of the cornea. The disadvantage of this diagnostic method is the inability to differentiate initial and subclinical keratoconus from congenital myopia with high corneal refraction (often 45.0-48.0 diopters) and corneal astigmatism (often up to 6.0 diopters and above).

The objective of the invention is the differential diagnosis of keratoconus and congenital myopia with high refractive power of the cornea and high astigmatism.

The technical result of the proposed method is an adequate choice of treatment tactics depending on the diagnosis of keratoconus or congenital myopia with high refractive power of the cornea and astigmatism.

The technical result is achieved by measuring the depth of the vitreous body (VST), as well as APS in the areas of the equator and the posterior pole of the eye.

One of the differential signs in the diagnosis of keratoconus and congenital myopia, we consider the acoustic density of the sclera (ASD). The possibility of measuring the attenuation of ultrasound in tissues is provided in most modern V3-scanning devices and has found application in V3-differentiation of tissues. The magnitude of the reflected signal and the amplitude of its attenuation are directly dependent on the physical properties of the tissue - its density or stiffness.

It is known that with myopia, including congenital, the biomechanical characteristics of the sclera decrease (Iomdina E.N. Biomechanics of the sclera in myopia: diagnosis of disorders and their experimental correction: Abstract of the thesis ... Doctor of Biological Sciences. Μ 2000; 48. ). Revealed a significant decrease in APS in myopia, correlating with its degree, the rate of progression, the condition of the fundus. (Tarutta E.P. Sclero-strengthening treatment and prevention of complications of progressive myopia in children and adolescents: Abstract of thesis ... Doctor of Medical Sciences. Μ 1993; 51., Khodzhabekyan N.V. Intravital studies of the biophysical properties of the sclera in myopia and their prognostic value: Abstract of the thesis ... Candidate of Medical Sciences Μ 1997., Kvaratskhelia N.G. Comparative study of the anatomical and functional features of the eyes with hypermetropia and myopia in children: Abstract of the thesis ... Candidate of Medical Sciences M, 2010.) The measurement of APS makes it possible to quantify the biophysical properties of the sclera. The APS measurement technique is non-invasive. The information obtained about the biomechanical properties of the sclera is vital and can be performed in patients of any age.

One of the main characteristics of the scleral capsule in patients with congenital and acquired myopia is the anteroposterior axis of the eye (AVE) (Avetisov E.S. Myopia. M: Medicine 1999; 288.). Taking into account the characteristic changes in the anterior segment of the eye in keratoconus, leading to an increase in the AOS due to an increase in the depth of the anterior chamber (Kovács I, Miháltz K, Németh J, Nagy ZZ. Anterior chamber characteristics of keratoconus assessed by rotating Scheimpflug imaging. J Cataract Refract Surg. 2010; 36(7):1101-6), for a more accurate differential diagnosis based on the results of our study, one should use the GST index, that is, the segment of the eye from the posterior pole of the lens to the posterior pole of the eye. It is this value that is associated with the state of the sclera.

A study was made of the biophysical properties of the scleral capsule (APS, PZO, and GST) in patients with keratoconus (67 eyes), high-grade congenital myopia (30 eyes), and emmetropic refraction (30 eyes). (Table. Average values of PZO, HST and acoustic density of the sclera (in c.u.) in eyes with keratoconus, high congenital myopia and emmetropic refraction (Μ±σ)).

The value of APS and HST in patients with keratoconus approaches that of healthy eyes with emmetropic refraction and is significantly higher than that of eyes with congenital high myopia. Comparing the parameters of eyes with emmetropia, keratoconus and congenital myopia, borderline values of APS and HST were obtained, which allow differentiating keratoconus and congenital myopia with high astigmatism. Further observations of patients confirmed the correctness of the diagnosis based on the HST and APS indicators.

The method is carried out as follows.

For differential diagnosis of keratoconus and congenital myopia with high refractive power of the cornea and astigmatism, the vitreous depth (VST) is determined - the distance from the posterior pole of the lens to the posterior pole of the eye and the acoustic density of the sclera (APS) in the region of the posterior pole and in the upper outer quadrant of the equatorial zone. When the HST value is less than 17 mm, the APS in the region of the posterior pole is more than 240 a.u., and in the upper outer quadrant of the equatorial zone it is more than 230 a.u. diagnosed with keratoconus.

To calculate the GST, optical biometry (Ziemer Galilei G6, Switzerland) is performed to obtain data on the anteroposterior axis of the eye (APA), central corneal thickness (CTR), anterior chamber depth (CPC) and lens thickness (TL). GST is calculated based on simple logic based on the anatomy of the eye, by subtracting the CTR, GPC and TX data from the PZO value (using the well-known formula GST=PZO-TsTR-GPK-TX).

APS is measured in arbitrary units (c.u.) based on the analysis of two-dimensional histograms in B-mode using an ultrasonic multifunctional diagnostic device Voluson E8 GE Healthcare with a linear transducer with a frequency of 10 to 16 MHz. APS is determined in the posterior pole of the eye and in the upper outer quadrant of the equatorial zone.

Example 1. Patient K 25 years old. For the first time he complained of a decrease in visual acuity in the distance. From the anamnesis it is known that she had high myopia since childhood, she does not know the magnitude of astigmatism. Uses glasses OU sph -5.0 cyl -2.0 ax 180°. There are no data from an earlier objective examination.

Vis in glasses OD=0.4, OS=0.3

Autorefractometry:

OD sph -6.75 cyl -4.5 ax 176°

OS sph -7.75 cyl -5.25 ax 172°.

Maximum corrected visual acuity (BCVA):

Vis OD 0.05 with sph -6.75 cyl -3.5 176°=0.7

Vis OS 0.05 with sph -7.75 cyl -3.25 ax 172°=0.5-0.6.

In order to exclude keratoconus, the patient underwent keratotopography. Corneal keratometry: OD Sim K 47.5 diopters, cyl 4.75 x 88° OS Sim K 48.4 diopters, cyl 5.68 x 89°. Keratotopographic indices of the anterior surface of the cornea KPI and Kprop were high, OD 21.9% and 36.2% and OS 35.4% and 80.9%, respectively. Based on keratometry data and high topographic indices of the anterior surface, subclinical keratoconus was diagnosed. For the purpose of differential diagnosis of congenital myopia and keratoconus, an additional study was carried out: PZO, CTR, GPC and TC with the calculation of HST, as well as the measurement of APS in the upper outer quadrant of the equatorial zone and the posterior pole.

Data received:

OD - PZO 26.1 mm, TsTR 0.51 mm, GPC 3.6 mm, TX 3.5 mm

OS - PZO 26.45 mm, TsTR 0.5 mm, GPC 3.65, TX 3.45

We calculate the GTS: PZO-TsTR-GPK-TX

OD: 26.1-0.51-3.6-3.5=18.49mm

OS: 26.45-0.5-3.65-3.5=18.8mm

APS:

Rear pole: OD 220.e. OS 218 c.u.

Equator: OD 209 c.u. OS 203 c.u.

Taking into account GTS OU>17 mm and APS less than 240 c.u. in the posterior pole and less than 230 c.u. in the upper outer quadrant of the equatorial zone, a diagnosis of congenital myopia was made.

Examination after 1 year: BCVA and all keratometry parameters remained the same. The absence of negative dynamics in the parameters of curvature and astigmatism of the cornea excludes the diagnosis of keratoconus and confirms the diagnosis of congenital myopia.

Example 2. Patient M. 19 years old. She complained of decreased distance vision.

Autorefractometry:

OD sph -5.0 cyl -3.5 ah 20°

OS sph -6.5 cyl -4.75 ax 156°.

BCVA:

Vis OD 0.05 with sph -5.0 cyl -3.5 20°=0.6 Vis OS 0.05 with sph -6.5 cyl -4 ax 159°=0.5.

In order to exclude or confirm keratoconus, the patient underwent keratotopography. Corneal keratometry: OD Sim K 47.03 diopters, cyl 3.75 ax 110° OS Sim K 47.75 diopters, cyl 5.0 ax 66°. Keratotopographic indices of the anterior surface of the cornea KPI and Kprop were high, OD 19.7% and 28.9% and OS 26.5% and 52.8%, respectively. Based on keratometry data and high topographic indices of the anterior surface, subclinical keratoconus was diagnosed. For the purpose of differential diagnosis of congenital myopia and keratoconus, an additional study of the PZO, CTR, GPC and TC was carried out with the calculation of HST, as well as APS in the upper outer quadrant of the equatorial zone and the posterior pole.

Data received:

OD - PZO 23.8 mm, TsTR 0.5 mm, GPC 4.0 mm, TX 3.5 mm

OS - PZO 23.9 mm, TsTR 0.5 mm, GPC 4.1 mm, TX 3.5

We calculate the GST:

OD: 23.8-0.5-4.0-3.5=15.8mm

OS: 23.9-0.5-4.1-3.5=15.8mm

APS was determined in the posterior pole of the eye and in the upper outer quadrant of the equatorial zone:

Rear pole OD 244 c.u. OS 246 c.u. Equator OD 234 c.u. OS 232 c.u.

Taking into account GTS OU<17 mm and APS more than 240 c.u. in the posterior pole and more than 230 c.u. in the equatorial zone, diagnosed with keratoconus.

Examination after 1 year: BCVA decreased by 0.1. The parameters of keratometry and astigmatism increased by more than 1 diopter, CTR decreased by 5% of the initial thickness, which indicates the progression of keratoconus and excludes congenital myopia.

Thus, the proposed method allows to differentiate keratoconus from congenital myopia with high corneal refractive power and astigmatism and to choose the appropriate subsequent treatment tactics.

Claims (1)

A method for differential diagnosis of keratoconus and congenital myopia with high refractive power of the cornea and astigmatism, characterized in that the vitreous depth (VST) is determined - the distance from the posterior pole of the lens to the posterior pole of the eye and the acoustic density of the sclera (APS) in the region of the posterior pole and in in the upper outer quadrant of the equatorial zone and when the HST value is less than 17 mm, the APS in the region of the posterior pole is more than 240 a.u., and in the upper outer quadrant of the equatorial zone it is more than 230 a.u. diagnosed with keratoconus.