The proportion of soldiers who have undergone corneal refractive surgery has increased significantly. According to the 2018 national survey of myopia in children and adolescents in China, the overall myopia rate in adolescents is 53.6%; 81% of those affected are high school students, and 21.9% of senior high school students have hypermyopia (SE ≤ -6.0D), indicating that myopia has become a critical issue affecting eye health. To meet the vision requirements in the Physical Examination Standards for Citizens Eligible for Enlistment, many young people choose to undergo corneal refractive surgery before joining the army. In 2008, a re-examination of eye diseases in 20320 recruits in the field forces found that 3.24% of recruits underwent refractive surgery before enlistment . A survey of 4579 recruits who enlisted in the army in 2013 found that 12.3% underwent refractive surgery . In 2015, the proportion of recruits who had undergone corneal refractive surgery was 15.32% . Another survey of 526 recruits in 2015 found that 13.1% of them underwent corneal refractive surgery before enlistment, and those with low- and moderate-grade myopia accounted for 61.6% . This study found that among the soldiers who had an average time since enlistment of 3.20 years and had undergone corneal refractive surgery, 34.40% were male, and 34.75% were female. The shortest postoperative time was 1 year, and the longest was 6 years, with an average of 2.76 years. An analysis of recruits’ physical examinations over the years showed that the proportion of soldiers who had undergone corneal refractive surgery increased gradually (Fig. 1). With the development of refractive surgery, the proportion of soldiers undergoing corneal refractive surgery could become even higher in the future. Compared with the no surgery group, the soldiers who had undergone refractive surgery showed differences in corneal thickness, corneal curvature, and biomechanics. At present, there is still a lack of large sample size studies on the impact of corneal refractive surgery on military officers and soldiers. Regarding physical examinations, the available eye examination items and indicators can no longer fully reflect the visual functioning of officers and soldiers. Regarding military training, daily management, and health education, it is necessary to further clarify whether differentiated management is needed for soldiers who have undergone corneal refractive surgery. In particular, the safety of corneal refractive surgery and the impact of its complications on the functions of military officers and soldiers should be emphasized.
Although corneal refractive surgery can significantly improve the UCVA, it is also associated with visual regression and other complications. This study found that among the 862 eyes that underwent corneal refractive surgery, 34 (3.94%) showed visual deterioration, with UCVA < 5.0; furthermore, among these 34 eyes, 82.35% had moderate and high diopters preoperatively. The increased proportion of people undergoing corneal refractive surgery has led to an increase in common complications, such as xerophthalmia, glare, poor contrast sensitivity, and night vision disorders [3, 5, 6]. Among soldiers who have undergone corneal refractive surgery, 28% have experienced xerophthalmia compared to 6% of soldiers who have not undergone refractive surgery, indicating that the surgery group has more than 4 times the rate of xeropthalmia that the non-surgery group . Soldiers often work in special environments for long periods, and their irregular rest times both during the day and at night can easily worsen xerophthalmia and asthenopia. The medical team should strengthen health education, pay attention to the healthy use of eyes, and arrange for reasonable tasks. Artificial tears medicine and other reserved drugs can be appropriately used if there is a high incidence of such complications.
With the emergence of new surgical techniques, such as SMILE and Trans-PRK, the methods of corneal refractive surgery have become diversified in recent years. This study found that among 435 surgeries, LASIK was the main surgical method for low-, moderate-, and high-grade myopia, accounting for 66.67%; SMILE was a widely used method for low- and moderate-grade myopia, accounting for 23.44%; PRK accounted for only 9.9%, and although it was mainly used for low- and moderate-grade myopia, a small number of soldiers with high-grade myopia did use it. Different surgical methods have different complications and postoperative risk factors. Studies have found that the proportion of glare and night vision disorders after corneal refractive surgery is 23%; LASIK results in the highest rate of these disorders, at 33% . Dennis et al.  found that after PRK, slight haze can cause decreased visual acuity under complex light interference and can decrease contrast sensitivity under normal conditions and complex light interference, which directly influences performance capacity. This study did not find haze (above grade 3), which can negatively impact vision, in the soldiers; however, haze (grade 1–2) was common among the soldiers on slit-lamp examination. Soldiers who have undergone corneal refractive surgery often have a high risk for potential ocular trauma, especially those who have undergone LASIK. An investigation of 1131 hospitalized soldiers with ocular trauma at 27 military hospitals from January 2006 to December 2010 found that among 3 soldiers who had undergone radial keratotomy (RK), 2 soldiers had eyeball ruptures; among 72 eyes that had undergone LASIK, 69 eyes had mechanical ocular trauma, and 29 eyes had corneal flap dislocation . LASIK is a surgical method that uses excimer lasers to perform refractive cutting of the stromal layer of the corneal flap to correct refractive errors. It has advantages of safety, reliability, predictable vision, and strong stability . However, this surgery affects the corneal stroma flap. Even after many years, the tissue healing of the corneal flap and corneal stroma might not achieve a normal state since the postoperative healing reaction of the two is negligible; therefore, corneal flap displacement and wrinkles are more likely to occur . Soldiers are often involved in vigorous exercises and fights, so the eye injury rate in soldiers is significantly higher than that normal people, making a weakly healed corneal flap more vulnerable to injury . Corneal flap displacement and wrinkles are more likely to occur after trauma and impacts and can result in impaired vision due to complications such as keratitis and epithelial implantation. In addition, the treatment effect is poor because the lack of obvious early symptoms means these complications cannot be diagnosed and treated in a timely manner . This study found that a soldier had accidentally injured his eyes during training 1 year after undergoing LASIK and had suffered corneal epithelial implantation (Fig. 2). Because of the negligible impact on the UCVA in the early stage, the patient did not seek medical care until 1 year after the onset, which caused great difficulty in treatment. SMILE can avoid the complication of corneal flap displacement, has faster postoperative vision recovery and less incidence of xerophthalmia than LASIK, and has become very popular in recent years [14, 15]. The complications are different for different surgical methods, and their influences on performance capacity are different due to different surgical mechanisms. Therefore, hierarchical management should be considered for different corneal refractive surgeries to effectively reduce the influence of such surgeries on military operations and complications related to corneal refractive surgery, thereby avoiding military training injuries.
For patients with hypermyopia, corneal refractive surgery cannot improve fundus lesions. At present, there are no clear requirements regarding the degree of myopia required in soldiers before corneal refractive surgery during military physical examination. In this study, preoperative high-grade myopia (SE ≤ -6.0D) was present in 14.71% of the soldiers who had undergone refractive surgery. Some studies pointed out that there was a high probability of retinal degeneration, lattice degeneration, and retinal detachment after surgery . A study reported that 658 soldiers who had undergone refractive surgery experienced a significant increase in visual deterioration, retinal detachment, and retinal tears after 2 years of enlistment . Therefore, hierarchical management should be performed in response to the different corneal refractive surgery methods and the collected information regarding the preoperative diopter and eye disease history. Especially for those with a high degree of myopia before surgery, special attention should be paid to the fundus; regular dilatation examinations should be performed for the early detection and intervention of retinopathy so that serious complications, such as retinal tear and retinal detachment, can be avoided.
Although implantable contact lenses (ICLs) can significantly improve vision and have obvious advantages in the treatment of high-grade myopia, there are relatively high risks of postoperative cataracts, glaucoma, corneal endothelial decompensation, lens dislocation, and decreased visual quality . Therefore, applicants who have undergone ICL implantation are considered “unqualified” in the physical examination for citizens eligible for enlistment, and aspiring soldiers should think twice before choosing this refractive surgery method. This study found that 5 soldiers had hypochromatopsia with normal single-color recognition ability, and they all had a history of corneal refractive surgery. Li et al. reported that intraocular scattering can be changed after LASIK, causing symptoms such as halo, starburst, decreased contrast sensitivity and impaired color vision recognition ability . Whether corneal refractive surgery can impair color vision and cause other changes in binocular visual function must be clarified in further systematic studies.