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Eyesight issues 眼疾

 

Myopia (also known as Shortsightedness) is a refractive defect of the eye in which collimated light produces image focus in front of the retina when accommodation is relaxed. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in front of it. This causes the image that one sees when looking at a distant object to be out of focus but in focus when looking at a close object.

Eye care professionals most commonly correct myopia through the use of corrective lenses, such as glasses or contact lenses. It may also be corrected by refractive surgery, though there are cases of associated side effects. The corrective lenses have a negative optical power (i.e. are concave) which compensates for the excessive positive diopters of the myopic eye.

  
Environmental Factors - Development of myopia has close relationship with extensive usage of eyes for near objects such as reading books, looking at computer screen, doing homework, etc. Human eye is at growth stage until about age of 18 year old, thus the expansion of eyes wall (sclera) is significantly larger especially with intense pressure built up due to extensive near object vision. After extended period of time, such effect causes longer eye axial and resulted the image focus in front of retina and causing blur vision. Incremental of eye axial length of 1mm is equivalent to 300 degree of myopia.
 
 
近视 - 眼睛看不清远物、却看清近物的症状。在屈光静止的前提下,远处的物体不能在视网膜汇聚,而在视网膜之前形成焦点,因而造成视觉变形,导致远方的物体模糊不清。一般用凹透镜矫正近视。
 
环境因素- 近视眼的发生和发展与近距离用眼的关系非常密切。青少年的眼球正处在生长发育阶段,调节能力很强,眼球壁的伸展性也比较大,阅读、书写等近距离工作时,不仅需要眼的调节作用的发挥,双眼球还要内聚,这样眼外肌对眼球施加一定的压力,久而久之,眼球的前后轴就可能变长。每增长1毫米就达300度,当然这种近视绝大多数为单纯性近视,一般度数都比较低,都在600度以下,发病多在青春期前后,进展也比较缓慢。
   
  
 
Amblyopia (also known as Lazy Eye) – It is a disorder of the vision system which is characterized as vision deficiency in an eye that is otherwise physically normal. Children from born to 10 year old is the critical period for vision development. During eye development, if there is genetic or environmental effect resulted poor vision and eye test indicated vision capability below 0.9 level and confirmed without other eye disease. If vision capability cannot be corrected to meet 1.0 level with glasses, then it is characterized as amblyopia.
 
弱视 -弱视引起的视力下降,是眼功能性疾病,没有眼组织的病变,属于视功能发育不良。婴儿出生到10岁间,是儿童视功能发育成熟期。在发育期,如果因遗传或后天环境的影响,使视功能发育不良,远视力低于0.9,经检查,既没有其他眼病。也不能用眼镜提高视力到1.0,这种视力缺陷被称为弱视。
  
 
Astigmatism -it is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. The refractive error of the astigmatic eye stems from a difference in degree of curvature refraction of the two different meridians (i.e., the eye has different focal points in different planes.) For example, the image may be clearly focused on the retina in the horizontal (sagittal) plane, but not in the vertical (tangential) plane. Astigmatism causes difficulties in seeing fine detail, and in some cases vertical lines (e.g., walls) may appear to the patient to be tilted.
 
散光 - 眼球在不同经线上的屈光力不一致,或同一经线的屈光度不等,以致进入眼内的平行光线不能在视网膜上结成焦点,而形成焦线,从而对视力造成影响。一般情况下,散光度数是比较稳定的,且一般不会随年龄增长而增加度数。因此轻度散光(50度以内),一般人是不需要矫正。
   
   
  
 
Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely affect depth perception. Strabismus can be either a disorder of the brain in coordinating the eyes, or of one or more of the relevant muscles' power or direction of motion. Difficult strabismus problems are usually co-managed between orthoptists and ophthalmologists.
 
斜视 - 俗稱”斗鸡眼”。两眼不能同时注视目标,属眼外肌疾病。斜视病因复杂,现代西医学除针对病因及手术治疗,对病因不明者,尚无理想方法。
 

 

Hyperopia (also known as Farsightedness), longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or the lens cannot become round enough), causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance. As an object moves toward the eye, the eye must increase its optical power to keep the image in focus on the retina. If the power of the cornea and lens is insufficient, as in hyperopia, the image will appear blurred. Minor amounts of hyperometropia are sometimes left uncorrected. However, larger amounts may be corrected with convex lenses in eyeglasses or contact lenses. Convex lenses have a positive dioptric value, which causes the light to focus closer than its normal range.

 
远视 - 平行光线进入眼内后在视网膜之后形成焦点,外界物体在视网膜不能形成清晰的影象。病人主观感觉看远模糊,看近更模糊。用凸透镜矫正远视。轻度的远视,通过晶体的调节,主观感觉不明显。随着年龄的增大,调节力下降,视疲劳,视物模糊等症状慢慢表现出来。