First, the definition, classification, clinical manifestations and diagnostic points of myopia
(1) definition
When the human eye is in a relaxed state, parallel light passes through the refractive system of the eyeball and focuses on the retina, which is called myopia.
(2) Classification
1. Classification according to refractive components:
(1) Refractive myopia: the refractive power is beyond the normal range, but the axial length is basically within the normal range, mainly because the curvature of cornea or lens is too large or the refractive composition is abnormal.
(2) Axial myopia: Due to the elongated axial length, the axial length is beyond the normal range, and other refractive components such as cornea and lens are basically within the normal range.
2. According to the course progress and pathological changes:
(1) Simple myopia: Most patients have no fundus lesions and progress slowly. Vision can be corrected to normal with appropriate lenses, and other visual function indicators are normal.
(2) Pathological myopia: visual function is obviously impaired, far vision correction is not ideal, near vision can be abnormal, and fundus lesions of different degrees can appear, such as myopic arc spots, leopard-print fundus, macular hemorrhage or neovascularization, irregular white atrophy spots or round black spots (Fuchs spots) with pigmentation can appear; Lattice degeneration and cystic degeneration in the peripheral part of retina; Vitreous liquefaction, opacity and posterior vitreous detachment occur at a younger age. Compared with normal people, the risk of retinal detachment, tear, hole, macular hemorrhage, neovascularization and open angle glaucoma is much greater. Often the anterior and posterior diameter of eyeball becomes longer, the eyeball becomes more prominent, and the posterior pole of eyeball expands to form posterior scleral staphyloma. Those with the above clinical manifestations are pathological myopia.
3. according to the degree of myopia: low myopia:-0.50 d ~ 3.00 d; Moderate myopia:-3.25 d ~ 6.00 d; High myopia: >-6.00d.
(3) Clinical manifestations and diagnostic points
It is necessary to comprehensively consider visual symptoms, diopter and refractive components, as well as binocular visual function, myopia nature, myopia progression speed and myopia complications, as follows:
1. Hyperopia is blurred, myopia is good, hyperopia often fluctuates at first, and squinting when staring at distant objects.
2. Determine myopia and degree through objective optometry and subjective optometry.
3. In addition to poor far vision, people with high myopia are often accompanied by night parallax, floaters, flashes and other symptoms, and may have different degrees of fundus changes.
Second, the influencing factors and prevention of myopia
environmental factor
1. Close work: Close work is recognized as a risk factor affecting the occurrence and development of myopia, which is positively related to the development of myopia. In addition to the total amount of close work, the duration of close work (> 45 minutes) and short reading distance (< 33 cm) are also important risk factors for myopia.
2. Outdoor activities: Outdoor activities are negatively correlated with the occurrence and progress of myopia, which is a protective factor for myopia. Therefore, it is advocated to increase the time of outdoor activities from preschool, such as kindergartens. Where conditions permit, it is encouraged to increase outdoor activities 1 hour every day.
3. Reading and writing habits: Bad reading and writing habits are risk factors for myopia. Teenagers who tilt their heads when writing and hold the pen with their fingertips close to the tip (< 2 cm) have a higher prevalence of myopia. Good reading and writing habits should be cultivated. The fingertips of the pen should be one inch (3.3 cm) away from the tip of the pen, the chest should be 6-7 cm away from the table, and the book should be one foot (33 cm) away from the eyes. Keep the correct posture to read and write, and don't read when walking, riding or lying down.
4. Lighting: Reading and writing should be carried out in an environment with good lighting and sufficient light. The average illumination value of the desktop should not be less than 300 lux, and should be adjusted according to the job category and reading font size to avoid glare and visual fatigue.
5. Eye exercises: Eye exercises can relax your eyes. Clinical research shows that doing eye exercises can reduce the lag of adjustment and improve subjective asthenopia compared with not doing eye exercises, thus helping to control myopia.
6. Others: Other environmental factors for the occurrence and development of myopia may include nutrition, sleep time, trace elements and the use of electronic products.
(2) Genetic factors
For simple low and moderate myopia, the interaction between genes and environment leads to the progress of myopia. Teenagers whose parents are nearsighted have a significantly increased risk of myopia, which is positively related to the degree of myopia of their parents. At present, there are many family studies, twin studies and population genetics studies on myopia-related genes. For high myopia, especially pathological myopia, the role of genetic factors is more obvious. Therefore, parents with myopia should pay more attention to let their children avoid the environmental factors that are easy to be nearsighted.
Third, the relevant examination of myopia
From kindergarten, it is necessary to check children's eyesight, diopter, axial length, corneal curvature and fundus regularly, and establish children's refractive development files, which will help to find children's poor eyesight, myopia tendency and myopia degree at an early stage, so as to manage them in different grades and formulate corresponding intervention measures. For children with a family history of high myopia, we should strengthen regular follow-up and focus on prevention and control.
(1) General inspection
1. Vision check: Vision check is the first step to find myopia. Through visual inspection, it is convenient and quick to distinguish suspected myopia from normal people. Vision examination should be carried out under medium brightness, and the indoor light should be dim. If the backlight mode is adopted (eye chart light box, projection or video eye chart), it is suggested that the brightness of standard eye chart is 80 ~ 320 cd/m2. At present, the brightness of the eye chart is 160cd/m2, which is a widely used standard. Because it is difficult to get a certain brightness in different projectors, light boxes and video display systems, it may be reasonable and practical to use 80 ~ 320 CD/m2 as the brightness of the eye chart in clinic. If the direct illumination method (printed visual chart) is used, it is recommended that the illumination be 200 ~ 700 lux. Set the inspection distance according to the selected eye chart. Cover the opposite eye when measuring, and be careful not to squint or press the covered eye. Generally, the right eye is examined first, and then the left eye is examined. When checking, let the candidates see the maximum line of the visual target first. If it can be identified, from top to bottom, from big to small, gradually point smaller visual targets at the examinee until the smallest line of visual targets that can be clearly identified is found, and at least three visual targets in 1 line can be identified as accurate results. Candidates should not read each target for more than 5 seconds. If it is estimated that the candidate's eyesight is still good, it is not necessary to start from the largest line of sight, but may start from a smaller line as appropriate. When recording and expressing vision, the type of eye chart should be indicated.
The threshold of preschool children's vision examination must consider the age factor. The strabismus and amblyopia group of Ophthalmology Branch of Chinese Medical Association proposed that the reference value of normal vision for children of different ages should be 0.5 for 3-5 years old and 0.7 for children over 6 years old. For school-age children over 6 years old, if the naked eye vision is lower than the decimal vision of 0.5 (that is, LogMAR vision of 0.3), it is the standard for suspecting refractive abnormality. In short, if the naked eye vision is lower than the lower limit of normal children of the same age, it is necessary to suspect ametropia (myopia, hyperopia, astigmatism) or even amblyopia.
2. slit lamp examination: understand eyelids, conjunctiva, cornea, iris, anterior chamber, pupil and lens.
3. Fundus examination: Fundus examination includes color fundus photography, direct ophthalmoscope examination and indirect ophthalmoscope examination. Color fundus photography shooting standard: the center should be the midpoint between the optic disc and the macula, with moderate exposure and clear focus. If the diopter is greater than -3.00DS or the retina has myopic lesions (such as paraoptic atrophy arc, leopard-print fundus, macular fuchs spot, posterior scleral staphyloma, and periretinal fundus lesions), the patients should be followed up regularly.
For myopia patients with floating or flashing sensation, direct and indirect ophthalmoscope examination should be performed after mydriasis, and pressing the sclera can check whether there are degeneration and holes in the peripheral retina. In particular, we should pay attention to the following situations:
(1) Poor eyesight, and vision correction can't reach normal.
(2) People with high myopia.
(3) A sudden sense of fine dust or flash.
(4) Patients with poor refractive stroma, such as vitreous pigmentation or vitreous opacity, and patients with high myopia complicated with retinal detachment. The examination of the contralateral eye is very important for finding new lesions and their prevention and treatment.
4. Examination of cycloplegia optometry: cycloplegia optometry, commonly known as mydriasis optometry, is an internationally recognized gold standard for diagnosing myopia. It is suggested that/kloc-children under 0/2 years old, especially those who have undergone optometry for the first time, or those who have hyperopia, oblique amblyopia and large astigmatism, must undergo optometry for cycloplegia, and those who need glasses for myopia need to review optometry regularly.
Commonly used drugs for cycloplegia are 1% atropine eye ointment or gel, 1% cyproterone hydrochloride eye drops and compound tropicamide eye drops.
1% atropine eye gel has the strongest effect on ciliary muscle paralysis and lasts for a long time. It is suitable for myopia children under 7 years old, especially for hyperopia and oblique amblyopia patients. The application method of 1% atropine eye gel is 2 ~ 3 times a day for 3 days; Patients with esotropia, 1 ~ 2 times a day for 5 days. The second reinspection time is 2 1 day to 28 days.
1% Cyclopentoxide Hydrochloride Eye Drops has the effect of mydriasis second only to atropine eye gel, and its action time is shorter. When atropine eye gel cannot be accepted, it can be considered as a substitute for mydriasis optometry of myopia children aged 7 ~ 12. 1% cyproterone hydrochloride eye drops are used twice every 20 minutes before and after optometry. The second reinspection time is from the third day to 1 week.
Compound tropicamide eye drops have a short duration and the weakest action intensity among the three, which is suitable for people aged 12 ~ 40 years, and can also be used for mydriasis optometry of myopia children aged 7 ~ 12 years in clinic. The application method of compound tropicamide eye drops is to drop it three times at the interval before optometry 10 ~ 20 minutes, and optometry is performed after 30 ~ 40 minutes. The second reinspection time is from the second day to 1 week.
It should be noted that the optometry results after ciliary muscle paralysis can give doctors a preliminary understanding of the ametropia of the eyes in the unadjusted state, but it is not the best prescription for correction. The final correction prescription must be determined after weighing the refraction of both eyes, subjective optometry, binocular balance and the specific visual requirements of patients.
(2) Special inspection
1. corneal curvature examination: the average curvature radius of normal adults is 7.77mm, the horizontal curvature radius of the anterior surface of cornea is 7.80mm, the vertical curvature radius is 7.70mm, and the posterior surface curvature radius is 6.22 ~ 6.80 mm.3 ~15-year-old children's normal corneal curvature radius is 7.79 mm, with the growth of children's age, the corneal curvature radius shows a downward trend. Too steep curvature of cornea or lens surface will lead to refractive myopia or curvature myopia and bending myopia. Therefore, the refractive power and thickness of the lens are also parameters that need to be observed regularly.
2. Examination of axial length: at birth, the axial length is 16mm, and it can reach the emmetropic eye level of about 23mm at the age of 3, and then it grows at the rate of about 0. 1 ~ 0.2 mm every year, and it can reach the adult level of 24mm at the age of 13 ~ 14. The rapid growth of axial length in developing children may be a trend factor of myopia, but the normal growth of axial length should be considered.
3. Binocular visual function examination: For myopic patients with strabismus or anisometropia, binocular monocular function should be examined and evaluated. Voss four lights can be used to evaluate the perceptual fusion function, while stereogram can be used to measure the sharpness of stereoscopic vision.
4. Examination of accommodation and convergence function: After ametropia is corrected and eye diseases are excluded, if there are still symptoms such as asthenopia, blurred vision, acid eye, eye pain and diplopia related to close work, the accommodation and convergence function should be examined. The main inspection methods include adjustment amplitude (near/far method, negative lens method), adjustment response (when the adjustment response of the near visual target is lower than the adjustment stimulus, it is adjustment lag, and vice versa), relative adjustment (negative relative adjustment, positive relative adjustment), adjustment flexibility (backhand method), setting amplitude (setting near point method), positive and negative fusion convergence and divergence, AC/A ratio (AC/A ratio).
5. Examination of intraocular pressure and visual field: Because pathological myopia with glaucoma is more common, intraocular pressure and visual field should be examined to determine whether there is glaucoma.
6.A/B ultrasound examination: Patients with high myopia should have A/B ultrasound examination to know the axial length, vitreous body and retina, and whether there is posterior scleral staphyloma.
7. Optical coherence tomography (OCT): OCT can observe the subtle changes of retina in macular area. For patients with high myopia or pathological myopia, OCT is helpful for early detection of myopia-related diseases in macular area, such as posterior scleral staphyloma, macular splitting, retinal choroidal atrophy in macular area and so on. OCT examination of the thickness of retinal nerve fiber layer, retinal pigment epithelium and choroid can guide the staging and treatment of myopia macular degeneration.
In addition, OCT can show many different morphological features of choroidal neovascularization (CNV), clearly show its anatomical level and histological relationship, and further describe its pathological changes and morphology in different periods. In OCT, CNV can be clearly displayed even in the case of massive subretinal hemorrhage, and its shape and size, relationship with surrounding tissues and anatomical position can be accurately described.
8. Fluorescein angiography (FFA): FFA is a standardized examination method to evaluate CNV caused by pathological myopia, which can be used to differentiate CNV caused by recent myopia. Some studies show that FFA is superior to other methods in detecting CNV in active myopia, so it is suggested that FFA should be performed in any case suspected of CNV in myopia. Typical myopia CNV is a small and flat gray subretinal lesion, usually located in or near the fovea of macula, with or without bleeding. The myopia CNV of FFA is characterized by high fluorescence with clear boundaries in the early stage and fluorescein leakage in the late stage.
Fourth, corrective measures for simple myopia
(1) frame glasses. Frame glasses are the simplest and safest corrective equipment. They should be rechecked at least once a year and adjusted in time. Children with myopia should be reviewed at least once every six months. At present, it is recognized that over-correction will lead to over-adjustment and aggravate the development of myopia, which should be avoided. Monofocal lens is a kind of common frame glasses in clinic. There are bifocal lenses, trifocal lenses and progressive lenses for patients with adjustment problems. The focal length of the upper half of a bifocal lens is a distant object, and the focal length of the lower half is the reading distance. Progressive lenses can increase the visual range of objects and are suitable for early presbyopia people who do not require a large field of vision when they are nearsighted. Teenagers with obvious exotropia or exotropia in myopia can wear progressive lenses, which may aggravate symptoms and affect binocular visual function.
(2) contact lens.
1. Soft contact lens: it can be used to correct myopia, and some children can be used to restore binocular vision and promote visual development. Children or the elderly who are unable to take care of themselves must use them under the close supervision of doctors and guardians if necessary. Do not use it with caution if you have any active acute inflammation of the eyes, systemic diseases that affect wearing, excessive tension, poor personal hygiene, poor compliance and inability to check regularly, allergic to nursing solution or poor hygiene in living and working environment.
2. Rigid contact lens (RGP): suitable for wearers of any age who need it and have no contraindications. For those who are too young or too old, safety monitoring should be increased due to their sensitivity to problems or operational compliance. Myopia, hyperopia, astigmatism and anisometropia, especially irregular astigmatism caused by keratoconus and corneal scar, can be given priority. Ocular surface active diseases or systemic diseases that affect the wearing of contact lenses should be banned. Use with caution those who have been in dusty and highly polluted environment for a long time, and those who often engage in strenuous exercise.
3. Orthokeratology lens (OK lens): It is a kind of rigid breathable contact lens with reverse geometric design. By wearing it, the curvature of the central area of the cornea is flattened in a certain range, thus temporarily alleviating myopia to a certain extent. It is a reversible non-surgical physical orthopedic method. Clinical trials have found that wearing orthokeratology lens for a long time can delay the development of adolescent eye axis by about 0. 1.9mm/ year. Based on the indications and non-indications of general contact lenses, it is emphasized that underage children need parental supervision and treatment. For the fitting of difficult cases such as high diopter, doctors with rich clinical experience need to consider it as appropriate.
(3) surgical correction. The surgical correction of myopia is to change the diopter of the eye through surgery. The main methods are laser corneal refractive surgery and intraocular lens implantation in phakic eyes. Myopia correction surgery needs to be screened and implemented in strict accordance with the contraindications and indications of various operations, and is mainly suitable for myopia patients with stable degrees over 18 years old.
1. Laser corneal refractive surgery: For those who are over 18 years old, have stable refractive power for more than 2 years, are mentally and psychologically healthy, have a reasonable desire to take off their lenses, and have appropriate expectations after surgery, laser corneal refractive surgery can be considered, but relevant preoperative examination is required before surgery, and the corneal thickness, refractive power, preset cutting depth and other conditions can be met before surgery. Different surgical methods have different preoperative requirements. Laser corneal refractive surgery is mainly divided into two types: laser lamellar corneal refractive surgery and laser shallow corneal refractive surgery. Laser lamellar keratorefractive surgery usually refers to mechanical knife or femtosecond laser-assisted laser in situ keratomileusis to make corneal flap. Femtosecond laser-assisted LASIK) also includes a small-incision microlens Smile that only uses femtosecond laser to take out corneal stromal lenses.
Laser shallow corneal refractive surgery refers to laser cutting on the surface of corneal anterior elastic layer and its underlying corneal stroma after mechanical corneal epithelial flap, including excimer laser photorefractive keratectomy (PRK), laser subepithelial keratomileusis (LASEK), epi-LASIK(epi-LASIK) and epithelial excimer laser keratectomy (TPR)
2. Phakic intraocular lens implantation: generally suitable for patients with high myopia who are unwilling to wear glasses but are not suitable for laser corneal refractive surgery. The phakic intraocular lens (PIOL) is used to correct myopia, that is, an intraocular lens with negative diopter is implanted in the anterior or posterior chamber, while the natural lens is preserved.
Five, pathological myopia and related complications of treatment measures
Pathological myopia patients' axial elongation and posterior scleral staphyloma progress continuously, and patients often have corresponding fundus changes, resulting in thinning of retina and choroid, and retinal diseases such as lacquered, choroidal neovascularization, macular atrophy, macular hole, subretinal hemorrhage, retinal degeneration and rhegmatogenous retinal detachment, which cause serious and irreversible visual damage. The treatment is mainly aimed at fundus changes and complications.
(1) laser photocoagulation therapy
In order to avoid retinal detachment, preventive retinal laser therapy can be used for middle and high myopia patients with peripheral retinal holes, degeneration and/or vitreous traction, or retinal detachment in the opposite eye.
(2) Photodynamic therapy
It has a very definite therapeutic effect on CNV caused by age-related macular degeneration (AMD). Pathological myopia can also cause macular CNV, and photodynamic therapy has a certain effect on pathological myopia macular CNV.
(3) Vascular endothelial growth factor
The occurrence of choroidal neovascularization is the main cause of vision loss in pathological myopia. Anti-VEGF drugs reduce the concentration of VEGF in vitreous cavity, which leads to the decrease of CNV. At present, large-scale clinical studies have preliminarily confirmed that intravitreal injection of anti-VEGF drugs is safe and effective in the treatment of subretinal CNV secondary to pathological myopia, which can obviously improve the best corrected vision of the affected eyes.
(4) Surgical treatment
1. Posterior scleral reinforcement (PSR): It is mainly suitable for early myopia > -3.00 d, with annual progress >-1.00 d, and predicts that people may develop progressive myopia; Progressive myopia in children or adolescents with rapid development is > -6.00 d, and the annual progress is >-65438 0.00 d, accompanied by anterior and posterior dilation of eyeball, posterior scleral uveitis formation, with or without visual loss; Age over 20 years, diopter >-10.00 d, progressive vision decline, obvious posterior scleral uveitis, fundus degeneration by fluorescein angiography; The age is over 55 ~ 60 years old, although the refractive power does not increase, it is complicated with obvious retinal and choroidal degeneration; High myopia complicated with retinal detachment, scleral reinforcement was performed at the same time as retinal reduction surgery. This operation can stabilize the axial length, effectively control the degree of pathological myopia and improve or treat the fundus complications of pathological myopia. The application of reinforcement materials is close to the extremely thin sclera wall behind the eyeball, which increases the thickness and toughness of the sclera wall in this area and controls the expansion of the eyeball.
2. Reduction scleral buckling surgery for rhegmatogenous retinal detachment: it is suitable for retinal detachment without severe proliferative vitreoretinopathy (1); (2) retinal detachment without posterior pole retinal hole; (3) Retinal detachment without choroidal detachment.
3. Vitrectomy: Vitrectomy (combined with internal limiting membrane peeling) is widely used. Most studies have proved that it has a higher retinal reattachment rate and hole closure rate than other surgical methods in the past, and intraocular silicone oil filling has also proved to have a better prognosis than gas filling, especially for elderly patients with severe retinal atrophy after pathological myopia who have not received fundus laser treatment. Macular hole is a common disease in high myopia. Macular breaks can lead to retinal detachment. Surgical treatment includes scleral buckling with or without coagulation, laser photocoagulation, simple gas injection into vitreous cavity, vitrectomy with or without internal limiting membrane peeling, combined gas injection into vitreous cavity or silicone oil filling.