Tuberculous keratopathy

Introduction to tuberculous keratopathy Tuberculosis is an ancient chronic infectious disease that remains one of the most important infectious diseases. Tuberculosis mainly causes pulmonary infection, eyelids, eyelids, tears, conjunctiva, cornea, sclera, uvea, retina and optic nerve and other ocular tissues can be directly or indirectly infected. A variety of tuberculous lesions can occur in the cornea. basic knowledge The proportion of illness: 0.002% Susceptible people: no specific population Mode of infection: contact spread Complications: corneal ulcer

Causes of tuberculous keratopathy

Cause:

Mycobacterium tuberculosis (MTB) is a pathogen causing tuberculosis. It is mainly divided into human, bovine, bird, and mouse. The human pathogens are mainly human bacteria, with fewer bovine types and fewer birds.

Pathogenesis

Tuberculous keratopathy occurs on the basis of tuberculosis in other parts of the eye, so it is mostly secondary and can occur in the following situations:

1. Spread from tuberculosis lesions around the conjunctiva or sclera.

2. From the iris, the tuberculous nodules of the ciliary body are infected along the Schlemm tube.

3. Mycobacterium tuberculosis disseminated by uveal tuberculosis, directly invading the posterior tissue of the cornea.

Tuberculous keratopathy prevention

In order to control the epidemic of tuberculosis, we should start from controlling the source of infection, cutting off the route of transmission and enhancing immunity, and reducing susceptibility.

1. Establish a prevention system

Establish and improve flood prevention agencies at all levels, be responsible for organizing and implementing governance, management, prevention, and investigation work, formulate prevention and control plans, carry out flood prevention publicity, educate the masses to develop good civilized hygiene habits, train flood prevention business technicians, and evaluate implementation countries. Prevention and treatment of tuberculosis prevention and treatment work plan (NTP).

2. Early detection and effective treatment of patients

Regular health checkups for factories, mines, service industries, school nursery staff and children's toy producers. Patients who are found in census or outpatient clinics should be treated promptly and thoroughly to improve the early diagnosis of comprehensive medical institutions and avoid missed diagnosis and misdiagnosis. Check the family members of the strong positive tuberculin test or the close contacts of the bacteria in the tuberculosis, and find out that it must be completely controlled to reduce the source of infection and prevent the formation and accumulation of chronic drug-resistant cases.

3. Vaccination with BCG

Bacillus Calmette-Guérin (BCG) is a non-toxic bovine tuberculosis live vaccine. After inoculation, the body reaction is the same as the primary infection of low-toxic tuberculosis, producing DTH and obtaining specific immunity, although not enough to prevent tuberculosis. , but can significantly reduce the incidence of children or reduce the disease, especially the incidence of serious tuberculosis such as tuberculous meningitis. China stipulates that newborns are vaccinated with BCG, and every 5 years, the tuberculin is replanted until 15 years old. BCG, which is negative for newborns and recruits who enter high-incidence areas in remotely-developed areas, must also be vaccinated with BCG. It is contraindicated for children who have already suffered from tuberculosis, acute infectious diseases less than one month or have chronic diseases. The study concluded that it is meaningless to inoculate BCG in countries with low infection rates and low prevalence rates. In high-incidence countries, especially in China, newborns still need to be vaccinated with BCG and included in the planned immunization range, but the intensive vaccination has stopped execution, nearly 10 Over the years, research and development of new vaccines has become a new trend, in order to improve the immune protection of BCG, such as BCG recombinant DNA, tuberculosis DNA vaccine.

4. Chemoprevention

China has prescribed chemoprevention of new infections of children and adolescents and tuberculin-positive people with high risk factors, INH 300mg / d, oral, for 1 year, regular liver function monitoring.

Tuberculous keratopathy complications Complications corneal ulcer

Extensive corneal scarring and corneal perforation.

Symptoms of tuberculous keratopathy common symptoms keratitis corneal ulcer calcification uveitis hardening ciliary congestion congestion pseudo anterior chamber empyema yellow nodules

1. Tuberculous sclerokeratosis and sclerosing keratitis

From the spread of adjacent scleral tuberculosis, ciliary congestion begins at the limbus, followed by deep infiltration (marginal keratitis) in the corresponding corneal periphery, and then merged into a triangular or tongue-shaped deep infiltration, which is porcelain white when severe ( Sclerosing keratitis), the progression of the disease is slow, good or bad, scars and neovascularization are left in each episode, and eventually extensive corneal scar or corneal uveitis is formed, leading to blindness.

2. Tuberculous keratitis (tubercular parenchymatous keratitis)

Occurred in young women, single eye involvement, can be caused by infection of adjacent lesions or allergic to tuberculin, occurs under the cornea, infiltration in the middle and deep layers of the matrix, often limited to a certain area, showing grayish yellow nodules Infiltrating, due to turbidity enlargement, fusion, and sometimes diffuse infiltration, neovascularization is different, surface blood vessels have a certain degree of morphology, few brush-like vasospasm is formed, and the posterior wall of the cornea often has yellow The formation of oil-like deposits or pseudo-anterior chamber empyema, the course of the disease is slow, and the time is longer, it can last for several years, and finally the scar (or calcification) remains turbid, and the visual acuity is seriously impaired.

3. Tuberculosis central keratitis

The clinical manifestations are very similar to those of monospora-like discoid keratitis, but no history of superficial keratitis, normal corneal sensation, mild or no ciliary congestion, new blood vessels first appear in the deep, and only surface neovascularization occurs in the late stage. After the recovery, the central area has white spots and is calcified.

4. Tubercular corneal ulcer

Very rare, often occurs in the peripheral part of the cornea adjacent to the bulbar conjunctiva, but also due to corneal stroma inflammation invading the epithelium to form ulcers, shallow cornea, deep layers of new blood vessels invade, the disease is stubborn, long-term cure, often can cause mixed infection and Corneal perforation occurs with serious consequences.

5. vesicular keratitis (phlyctenular keratitis)

Most of them are caused by allergic to tuberculosis proteins. Adolescents are more common. There are often active tuberculosis in other parts of the body. There are 1mm diameter round or oval gray-yellow infiltrates in the cornea, often accompanied by blood vessels. It is called bundle keratitis, repeated attacks, and the lesions appear to disappear. The left and right eyes alternately occur, stretching for many years, leaving corneal scars and affecting vision.

Examination of tuberculous keratopathy

1. MTB detection

It is the main basis for confirming tuberculosis. Direct thick smear acid-fast staining microscopy is fast, simple, and has fewer false positives. The standard for microscopic examination results is: (-) for every 300 fields of view, and 1 for every 300 fields of view. 2 of the number of reported bacteria; 3 to 9 for every 100 fields of view (+); 3 to 9 for every 10 fields (++); 1 to 9 for each field of view ( +++); 10 per field of view is (++++).

2. Tuberculin test (referred to as the knot test)

Old knot (OT) is a crude extract, MTB metabolite extracted from the dead liquid medium of MTB. The main component is tuberculosis protein. OT also contains other antigens. It can also cause non-specificity after injection. Reaction, PPD is a pure protein derivative of lignin, which is superior to OT. It is made into PPD-S by ammonium sulfate precipitation. It is pure, high-efficiency and non-specific allergic reaction is rare. It has been designated as the international standard for mammals by WHO. The WHO commissioned the Danish production name PPD-RT23, which has been widely used internationally. In the 1980s and 1990s, PPD-C and BCG-PPD produced in China, the protein content of both PPDs is similar to PPD-S, higher than PPD-RT23 is currently used in China. The former is used for screening of BCG vaccines, quality monitoring and clinical auxiliary diagnosis; the latter is used for epidemiological investigation.

The tuberculin test is mainly used for epidemiological investigation of tuberculosis infection. BCG can be weakly positive after vaccination. Moderate positive means that tuberculosis has been infected. The infection rate of urban residents in China is as high as 80%. There is no diagnosis of adult tuberculin test positive reaction. Significance, the positive reaction of tuberculin test in infants under 3 years old according to active tuberculosis theory, strong positive reaction in adults suggests active tuberculosis may be further examination, such as using 1U high dilution liquid for skin test showed strong positive reaction, It is suggested that there are active tuberculosis in the body. The current use of the nodules is not highly specific. It has a common cell wall antigen with other mycobacteria, such as Nocardia and Corynebacterium, and can also cause a weak positive reaction in the OT test. (Measles, mumps, chickenpox), HIV infection, immunosuppressive drugs such as glucocorticoids, sarcoidosis, tumor, kidney failure, malnutrition, and elderly DTH reaction can be positive, there are still A small number of very severe tuberculosis patients with negative reaction, the mechanism is still unclear, when the factors affecting the above diseases are excluded, especially A high concentration of tuberculin test (10 ~ 100U) negative reaction can rule out tuberculosis.

3. New diagnostic technology

(1) The new generation of BACTEC MGIT960 is a fully automatic mycobacterial culture instrument that combines rapid growth culture, detection and drug sensitivity technology of mycobacteria. MGIT relies on an oxygen-sensitive fluorescent compound to detect the growth of mycobacteria, using Middlebrook. 7H9 medium is supplemented with a silicon inlaid fluorescent compound, which is dissolved in the fluorescence of the oxygen quenching compound in the medium. After inoculation, the bacteria consume oxygen and generate fluorescence. The technique is observed at 365 nm with a long-wave UV lamp or a UV transilluminator. Time, reportedly reduced by 65 days, is conducive to the diagnosis and treatment of tuberculosis.

(2) Tuberculosis bacteriology genetic diagnosis system: a labeled nucleic acid fragment or a DNA probe for determining the homology sequence of MTB nucleic acid, a polymerase chain reaction technique capable of expanding MTB DNA in vitro, and direct observation of bacteria The restriction endonuclease characteristic of the chromosome identifies the nucleic acid fingerprint technology of the isolate, and the laboratory research on the nucleic acid fingerprint technology and the nucleic acid probe technology needs to be further strengthened.

(3) Serological diagnosis: The diagnostic techniques that have been applied in clinical practice include enzyme-linked immunosorbent assay (ELISA), dot immunobinding assay (DIBA), Western blotting, and solid-phase antibody competition assay. (solid-phase antibody competition test, SACT), etc., but there are still many problems to be studied.

3. X-ray inspection

Including perspective, X-ray film, CT, etc., it helps early diagnosis and judges the location, extent, nature, evolution and treatment effect.

4. Endoscopy

Including fiberoptic bronchoscopy, thoracoscopy, fiberoptic colonoscopy, sigmoidoscopy, laparoscopy, cystoscopy, etc., can provide pathogenic and pathological diagnosis for some tuberculosis.

5. Biopsy

For tuberculosis that does not sterilize tuberculosis and organs that do not communicate with the outside world, pathological and pathological diagnosis such as lung, pleura, peritoneum, liver, and lymph nodes can be performed by tissue biopsy.

Diagnosis and diagnosis of tuberculous keratopathy

According to the patient's history of tuberculosis, chest X-ray examination results and OT test positive, monocular disease and characteristic corneal signs, the diagnosis is not difficult.

Identification:

1. Tuberculosis is mostly monocular; syphilis is mostly in both eyes.

2. Tuberculosis occurs well under the cornea; syphilis often invades the entire cornea.

3. Tuberculous opacity is different in depth and unevenness; plum toxicity is diffuse and uniform gray-white turbidity.

4. The stage of tuberculosis is not clear; the stage of syphilis is obvious.

5. Tuberculosis has a long course of disease, repeated attacks, good and bad times; there is very little recurrence of syphilis.

6. Tuberculin for intradermal test has certain value for tuberculosis; and Kang-Hua reaction has certain value for the diagnosis of syphilis.

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