其他眼科問題
眼科問題在早產嬰兒中十分常見。在母腹中，胎兒眼睛的發育過程會持續到足月的時候。因此，早產的嬰兒有機會出現眼部發育不全。 [1] [[2] 雖然早產兒視網膜病變（ROP）是早產嬰兒中最常見的眼部疾病，但其他眼部問題，如屈光不正、斜視、色覺缺陷、視力下降、大腦視覺功能受損等也有機會出現。[3]
屈光不正包括近視、遠視和散光，這些眼部問題即使在普羅大眾中也很常見。然而，一項研究顯示，早產嬰兒患上以上問題的風險是足月嬰兒的四倍，而近視則是最常見的問題。[4] 這可能與早產兒眼球的弧度和長度發育不完全有關。家長可能會發現子女看不清一定距離內的物體，例如，近視的兒童會把書本或玩具放近他們的臉部，並抱怨眼睛疲勞或頭痛。對於只有屈光不正的兒童，只要配戴合適的眼鏡便可改善視力。
斜視（斜眼）是一種因眼部肌肉缺陷而導致眼球錯位的疾病，是另一種早產嬰兒比足月嬰兒更常見的眼科問題。[5] 早產兒視網膜病變（ROP）和較嚴重的屈光不正也可能導致斜視出現。家長或會留意到患者的眼睛「不在中央」或「偏向一側」，這種情況可以在嬰兒數個月至幾歲之間才出現。在作出診斷之前，嬰兒需接受醫生詳細的評估。治療方面，嬰兒可透過使用眼罩、眼藥水、配戴合適的眼鏡和接受眼部肌肉手術來改善斜視問題。[6]
除了眼睛，大腦在視覺功能上也扮演著不可或缺的角色。大腦幫助我們分析及處理眼部接收到的信息。由於早產兒的腦部較容易受到損傷（如出血、缺氧等），早產兒視力受損的風險亦會因而增加。[7] 即使眼睛結構正常，但整體的視力也可能因腦部受損而有所限制。
與早產兒視網膜病變（ROP）相比，這些眼科問題可能於嬰兒數個月到幾歲之間才出現。因此，家長對子女的觀察尤其重要。如有任何疑慮，我們鼓勵家長帶同子女約見視光師或眼科醫生進行評估。作為發展監測的一部分，衛生署轄下的母嬰健康院（MCHC）也會定期為兒童進行眼部檢查。
-撰寫自劉凱盈醫生
威爾斯親王醫院兒科
駐院醫生
Other ophthalmological problems
Babies born preterm are prone to ophthalmological (eye-related) problems. This is due to an interruption to the usual developmental pattern of the baby’s eyes which normally continues till term before the baby is born.[1],[2] While retinopathy of prematurity (ROP) is the commonest eye problem seen in preterm babies, other problems like refractive errors, strabismus, colour vision deficits, decreased visual acuity, impaired cerebral visual function[3] are also possible.
Refractive errors include short-sightedness, long-sightedness and astigmatism, and are commonly seen even among normal individuals. However, one study showed that the risk is four times higher in children born preterm than term, with short-sightedness being the commonest type.[4] This could be related to the incomplete development of eyeballs of preterm infants in terms of curvature and length due to shortened fetal life. Parents may find their children having difficulty in seeing objects at certain distances, e.g., short-sighted children would hold books or toys close to their face, complain of tired eyes or headache. For children with refractive error alone, visual function can be optimized with prescription glasses.
Strabismus (squint) describes an eye muscle deficit that caused misalignment of the eye. It is another condition that is seen more commonly in children born preterm than term.[5] It may be attributed partly to the presence of ROP and an increase in refractive errors.5 Parents often describe the affected eye as “not at the centre” or “deviated to one side”. This can happen from a few months to a few years of age. A detailed assessment by a doctor is essential before a diagnosis can be made. The treatment of strabismus includes use of eye patches, eye drops, eyeglasses and eye muscle surgeries in some cases.[6]
Apart from the eyes, the brain also plays an important part in visual function. It determines how well one is able to process the signals received from the eyes. As preterm babies are more prone to having injuries to the brain e.g., bleeding, hypoxia; they also have an increased risk of visual impairment.[7] This limits the overall visual function even though the eyes may be structurally normal.
In contrast to ROP, many of these eye-related problems present at a few months to a few years of age. Thus, parental observation is crucially important. Parents are always encouraged to bring their child to an optometrist or ophthalmologist for assessment if there are any concerns. Regular ophthalmological screening is also performed at the Department of Health’s Maternal Child Health Centres (MCHCs) as part of the Hong Kong government’s developmental surveillance.
Written by Dr. Sharon Lau
Resident, Department of Paediatrics
Prince of Wales Hospital
Reference:
[1] Achiron R, Kreiser D, Achiron A. Axial growth of the fetal eye and evaluation of the hyaloid artery: in utero ultrasonographic study. Prenat Diagn 2000; 20(11): 894–899.
[2] De Silva DJ, Cocker KD, Lau G, Clay ST, Fielder AR, Moseley MJ. Optic disk size and optic disk-to-fovea distance in preterm and full-term infants. Invest Ophthalmol Vis Sci 2006; 47(11): 4683–4686.
[3] O’Connor AR, Wilson CM, Fielder AR. Ophthalmological problems associated with preterm birth. Eye. (2007) 21:1254–60.
[4] Larsson EK, Rydberg AC, Holmstrom GE. A population-based study of the refractive outcome in 10-year-old preterm and full-term children. Arch Ophthalmol 2005; 123: 825–832.
[5] Holmstrom G, Rydberg A, Larsson E. Prevalence and development of strabismus in 10-year-old premature children: a population-based study. J Pediatr Ophthalmol Strabismus 2006; 43(6): 346–352.
[6] Donahue SP. Clinical practice. Pediatric strabismus. N Engl J Med 2007; 356:1040.
[7] Ramenghi LA, Ricci D, Mercuri E, Groppo M, De Carli A, Ometto A, et al. Visual performance and brain structures in the developing brain of pre-term infants. Early Hum Dev. 2010;86(1):73–75.