Characteristics of peripheral refractive errors of myopic and non-myopic Chinese eyes

Interest in peripheral refractive errors has increased as it was hypothesized that peripheral hypermetropia might provide a stimulus for axial elongation (Smith et al., 2005), this study was to determine relative peripheral refractive errors (RPRE) of the eyes of a group of Chinese children and adults. Central and peripheral (20°, 30°, 40° at nasal, temporal, superior and inferior meridians of retina) refractive errors were obtained from cyclopleged eyes of 40 children and 42 adults with a Shin-Nippon auto-refractor. Only right eyes were considered. Central spherical equivalent (M) was used to classify the eyes as Moderate Myopia (MM, −3.00 < M ? −6.00 D), Low Myopia (LM, −0.50 ? M ? −3.00 D), Emmetropia (E, −0.50 < M < +0.50 D) and Low Hypermetropia (LH, +0.50 < M ? +2.00 D). RPRE was calculated as the difference in M between the central and peripheral positions. The results showed that in both children and adults, horizontally, the RPRE profile for the MM group had a relative hypermetropic shift and in contrast, the profile for LH demonstrated a relative myopic shift. The difference in the profile between the MM and LH group was significant (p < 0.05). Also, the RPRE profile for MM group was different between adults and children with adult eyes showing greater amount of hypermetropic shift. Vertically, the RPRE profile of all the refractive error groups showed a myopic shift. Off-axis astigmatism increased and horizontally a shift from ‘with the rule’ to ‘against the rule’ astigmatism was observed for all groups. Our observations demonstrated that in Chinese eyes, the myopic group present a hyperopic shift in the periphery, the hypermetropic eye present a myopic shift and the emmetropic eyes present no differences to the fovea, which are similar to those reports in Caucasian eyes. The variations in the RPRE between various refractive error groups can be explained on the basis of eye shape.     

配戴角膜塑形镜和框架眼镜对近视儿童周边屈光度影响的随机对照临床试验

背景 临床实践发现角膜塑形镜具有延缓近视及眼轴长度进展的效果,但对于角膜塑形镜配戴的相关作用机制,特别是角膜塑型术对视网膜中心和周边的离焦作用机制尚不完全清楚. 目的 观察低中度近视儿童配戴角膜塑形镜和框架眼镜6个月后周边屈光度以及相对周边屈光度(RPR)的变化.方法 采用随机对照临床试验方法,于2014年6月至2015年1月在北京同仁眼科中心招募屈光度为-0.50～-6.00 D的低中度近视儿童100例,平均年龄(11.0±1.9)岁,均纳入右眼进行研究.受试者按入组顺序编号后由SAS统计软件PROC PLAN过程语句随机均分为角膜塑形镜组和框架眼镜组,每组50例50眼,戴镜时间均为6个月.采用开放视野红外自动验光仪分别测量戴镜前后中央0°、颞侧15°和30°、鼻侧15°和30°径线的屈光度,观察并比较各组受试眼戴镜前后周边屈光度和RPR(周边屈光度与中央屈光度差值)变化趋势. 结果 角膜塑形镜组和框架眼镜组受试者戴镜前屈光度分别为(-3.35±1.31)D和(-3.01±1.15)D,差异无统计学意义(P=0.201).角膜塑形镜组受试眼戴镜前鼻侧30°、鼻侧15°、中央0°、颞侧15°和颞侧30°径线周边屈光度分别为(-2.28±1.60)、(-3.28±1.41)、(-3.40±1.23)、(-3.38±1.12)和(-2.09±1.29)D,受试眼除颞侧30°外戴镜后6个月近视度数均下降,戴镜前后鼻侧30°、鼻侧15°、中央0°、颞侧15°屈光度变化值分别为(0.29±1.67)、(0.85±1.66)、(0.92±1.76)和(0.66±1.66)D,其中鼻侧15°、中央0°、颞侧15°与戴镜前相比差异均有统计学意义(均P＜0.05).框架眼镜组受试者戴镜前鼻侧30°、鼻侧15°、颞侧15°和颞侧30°径线周边屈光度分别为(-1.88±1.30)、(-2.66±1.18)、(-2.89±1.27)和(-1.94±1.31)D,戴镜后6个月上述各径线近视度数均增加,戴镜前后变化值分别为(-0.25±0.80)、(-0.43±0.67)、(-0.32±0.64)和(-0.22±0.75)D,与戴镜前比较差异均有统计学意义(均P＜0.05).角膜塑形镜组受试者戴镜前各径线RPR均为远视性离焦状态,戴镜后6个月颞侧15°和颞侧30°RPR变为近视性离焦状态.框架眼镜组受试者戴镜前各径线RPR均为远视性离焦状态,戴镜后各径线RPR均呈远视性离焦加深状态.结论 长期配戴角膜塑形镜能够使近视儿童的周边屈光度发生远视性漂移,视网膜周边呈现相对近视性离焦,而长期配戴框架眼镜则使周边屈光度发生近视漂移,视网膜周边远视性离焦加深.角膜塑形镜配戴可能通过改变周边屈光度而达到减缓近视进展的目的.     

Relative peripheral hyperopic defocus alters central refractive development in infant monkeys

Understanding the role of peripheral defocus on central refractive development is critical because refractive errors can vary significantly with eccentricity and peripheral refractions have been implicated in the genesis of central refractive errors in humans. Two rearing strategies were used to determine whether peripheral hyperopia alters central refractive development in rhesus monkeys. In intact eyes, lens-induced relative peripheral hyperopia produced central axial myopia. Moreover, eliminating the fovea by laser photoablation did not prevent compensating myopic changes in response to optically imposed hyperopia. These results show that peripheral refractive errors can have a substantial impact on central refractive development in primates.     

中国青少年近视患者水平视网膜相对周边屈光度和散光分量曲线类型研究

背景 视网膜相对周边屈光度(RPR)状态与近视进展的关系近年来成为研究的热点,目前尚缺乏对中国近视人群中视网膜RPR状态及散光分量的研究.因此,有必要针对中国青少年近视患者的视网膜RPR类型及散光分量进行分型研究. 目的 研究中国青少年近视患者视网膜RPR和散光分量的曲线类型.方法 选取2014年6月至2015年10月在北京大学人民医院眼科就诊的青少年近视患者301例301眼.以5°作为间隔,采用WAM-5500型开放视野红外验光仪采集从水平视野鼻侧30°至颞侧30°的周边屈光度数据.仅选取右眼数据进行分析.计算各个角度的等效球镜度(SER),用中央SER减去水平周边SER即为视网膜RPR(以离焦表示).依据视网膜RPR曲线的不同形态及鼻侧与颞侧的相对关系将视网膜RPR整理分型.采用傅里叶分解法将各个角度的散光分解为J0和J45分量,分析散光分量的曲线类型.结果 视网膜RPR曲线可分为7种类型,分别为负离焦型、颞侧正离焦鼻侧平坦型、颞侧正离焦鼻侧负离焦型、颞侧平坦鼻侧负离焦型、平坦型、颞侧负离焦鼻侧平坦型和正离焦型.散光分量Jo和J45可分为9型.中高度近视在Ⅰ型RPR(负离焦型)中的分布明显高于低度近视,差异有统计学意义(X2=26.770,P＜0.05);低度近视在Ⅲ型RPR(颞侧正离焦鼻侧负离焦型)中的分布明显高于中高度近视(X2=12.500,P＜0.05). 结论 低度近视与中高度近视的RPR曲线类型分布存在明显差异.散光绝对值在水平方向周边区域呈现鼻侧、颞侧不对称性.在视网膜鼻侧,随着注视角度的增加,其所对应的散光绝对值呈现逐渐增加的趋势(鼻侧10°除外).     

不同矫正方法对儿童眼周边屈光度的影响

目的研究不同屈光矫正方法对儿童眼周边屈光度的影响。方法自身对照横断面研究。15名儿童先后在裸眼、框架眼镜全矫和硬性透气性角膜接触镜（RGPCL）全矫三种状态下,从左侧30°到右侧300注视7个远处视标,用红外自动验光仪分别获取6个周边屈光度和1个中心屈光度,周边屈光度减去中心屈光度即相对周边屈光度,在各个位置对三种状态的相对周边屈光度进行单因素方差分析．如有统计学意义再用Bonferroni检验两两比对。结果被试儿童在裸眼、框架眼镜全矫和RGPCL全矫三种状态下,相对周边屈光度均呈远视（鼻侧10°除外）,幅度随周边角度增加而增大,表现为鼻、颞侧不对称,以向颞侧注视时更偏远视。但RGPCL矫正后的相对周边屈光度在颞侧较前两种状态偏近视,差异随角度增加而增大。向颞侧30。注视时,裸眼、框架眼镜矫正和RGPCL矫正后的相对周边屈光度分别达到（1．69±1．03）D、（1．84±0．99）D和（0．81±1．28）D。方差分析发现三种方法之间差异有统计学意义（F=3．79,P=0．031）,用Bonferroni检验发现在框架眼镜矫正和RGPCL矫正法之间差异存在统计学意义（P=0．043）。结论配戴RGPCL能改变颞侧周边屈光度,配戴框架眼镜则不能。如果偏近视的相对周边屈光度有利于控制近视进展,RGPCL是一个选择。     

高度近视患者与中低度近视患者周边屈光度的比较研究

目的研究高度近视与中低度近视患者周边屈光度的差异。方法对45例2013年6~10月在本院眼视光学中心就诊的近视患者(-2.50~-11.50 D)进行周边屈光度测量。患者平均年龄为(28.67±7.37)岁(20~47岁)。将患者分为高度近视组(球镜>-6.00 D,26例)和中低度近视组(球镜≤-6.00 D,19例)。遮盖左眼,右眼裸眼状态下,从颞侧30°至鼻侧30°依次注视7个2.5 m远视标,用红外自动验光仪获取6个角度的周边屈光度和1个中心屈光度。周边屈光等效球镜值(Ma)减去中心屈光等效球镜值(M0)即得到相对周边屈光度(RPRE)。周边与中心散光均分解为180°轴位散光(J180)和45°轴位散光(J45)。结果高度近视组和中低度近视组的平均RPRE在颞侧视网膜差异有统计学意义(P<0.05),且随偏中心注视角度的增加而增大,高度近视组的RPRE比中低度近视组更倾向于远视性离焦,而在鼻侧视网膜差异无统计学意义(P值均>0.05)。高度近视组鼻、颞侧RPRE不对称,颞侧视网膜较鼻侧视网膜远视性离焦量大(P<0.05)。2组患者周边散光差异无统计学意义。结论高度近视颞侧远视性离焦较中低度近视更加显著,可能与高度近视患者近视持续加深相关。     

配戴中周部加光设计镜片后的周边屈光度及顺应性分析

目的探讨一组特殊设计镜片对周边屈光度、周边清晰视力范围和主观感受的影响。方法 3例(4眼)被试者,年龄22～31岁,屈光度-2.0D,按随机顺序分别在单眼配戴普通非球面镜片、成长乐镜片、视特保大、中、小光区镜片的情况下进行周边屈光度、周边清晰视力范围测量和主观评分,主观评分包括远距和近距戴镜舒适度、清晰度和接受度。结果配戴5种镜片时,被试眼相对周边屈光度均为远视状态,远视度数随周边角度增加而增加。配戴普通非球面镜片和视特保大光区镜片时周边远视度数最大,视特保中光区镜片其次,成长乐镜片和视特保小光区镜片最小;配戴普通非球面镜片和视特保大光区镜片时的周边清晰视力范围最大,其次是视特保中光区镜片,最小的是成长乐镜片和视特保小光区镜片;远距评分为普通非球面镜片最高,视特保大光区镜片其次,然后为视特保中光区镜片,成长乐镜片及视特保小光区镜片最差;近距评分视特保大光区镜片接近普通非球面镜片,视特保中光区镜片和成长乐镜片其次,视特保小光区镜片最差。结论不同设计的中周部加光镜片对改变周边屈光度的作用存在差异,其配戴后的顺应性与镜片改变周边屈光度的程度呈负相关。     

近视儿童配戴单光镜后的周边屈光研究

目的:研究近视儿童配戴单光镜后对周边视网膜屈光状态的影响。方法:采用自身对照研究。入选10～15岁近视儿童48例,睫状肌麻痹下使用Grand Seiko WAM5500型红外验光仪测量右眼视网膜中心凹0°以及鼻颞侧10°,20°,30°的屈光值,分别在裸眼和配戴单光眼镜时测量。结果:近视儿童的平均屈光度为-3.99±1.22D,相对周边屈光度在水平视野上为远视性离焦。随着注视角度的增大,相对远视性离焦量增大。戴镜后的相对周边远视性离焦量较裸眼时增大(P<0.01)。戴镜前后的J180及J45相比较无统计学差异。结论:近视儿童配戴单光镜后周边视网膜远视性离焦量增大。根据周边视网膜的聚焦状态改进镜片的设计可能会成为近视矫正的新思路。     

渐进多焦点镜矫正状态下青少年近视周边屈光的变化

背景视网膜周边屈光状态会影响近视的发生和发展,不同的矫正方式对周边屈光状态产生不同的影响。目的比较青少年近视配戴渐进性多焦点镜（PALs）和单光镜（SVLs）下周边屈光状态及其两种状态间的差异。方法采用自身对照横断面研究设计。共纳入受试者40例40眼;年龄10～15岁,平均（12．54＋1．45）岁;男女比例为23：17;等效球镜度为-1．50—-6．00D,平均（-3．74±1.09）D,散光度〈-1．50D;矫正视力均≥20／25。用质量分数1％托吡卡胺滴眼液点眼3次麻痹睫状肌后,使用Grand Seiko WAM5500型红外验光仪测量受试眼周边屈光状态,测量点为黄斑中心凹（0°）、鼻侧及颞侧视网膜各10°、20°、30°共7个点的周边屈光力,各点测量6次,取其平均值。受试者按随机序号原则分别在PALs和SVLs矫正状态下完成周边屈光状态的测量,分析参数包括M值、相对周边屈光不正（RPRE）、J45、J180值,对检测结果进行统计学分析。结果PALs和SVLs的矫正视力分别为4．98±0．65和4．97±0．53,差异无统计学意义（t=0．222,P=0．639）。两种矫正状态下,随着偏心角度的增加,周边M值、RPRE屈光力逐渐向“远视性离焦”偏移,而周边J180屈光力逐渐向“近视性离焦”偏移;以上3个参数周边6个点之间相互比较,差异均有统计学意义（P〈0．05）;J45值周边变化不显著,在颞侧偏负,鼻侧偏正;在M值、RPRE、J180、J45值的周边6个角度中,部分角度的上述屈光力与中心凹相比差异均有统计学意义（P〈0．05）。与单光镜比较,渐变镜的周边M值及周边RPRE值均偏近视性离焦,差异有统计学意义（P〈0．05）。结论相对于单光镜,渐变镜矫正了部分周边远视性离焦,核心表现在M值和RPRE参数。PALs延缓青少年近视进展可能与周边屈光有关。     

Influence of age on peripheral refraction

To investigate how age affects peripheral refraction we measured objective peripheral refraction for 55 young subjects (24+/-4 years) and 41 older subjects (59+/-3 years) out to 35 degrees eccentricity in temporal and nasal visual fields. Subjects were compared in 1D subgroups based on central spherical equivalent refractions (low hypermetropes +0.54 D to +1.51 D, emmetropes +0.50 D to -0.49 D, low myopes -0.50 D to -1.49 D, moderate myopes -1.50 D to -2.58 D). Overall, young and older subjects with similar refractive corrections had similar peripheral refraction components. Both age groups showed relative hypermetropic shifts in the peripheral fields as myopia increased and also decreases in peripheral astigmatism J180 as myopia increased. J45 varied little across the visual field with linear relationships occurring between J45 and visual field angle for all but one subgroup (older emmetropes). Peripheral refraction in emmetropes to moderate myopes is relatively unaffected by age for healthy eyes of similar refractive errors.     

可调节度数眼镜验光与传统验光法在社区老年人眼保健中的应用比较

背景 中国老年人屈光不正矫正需求巨大,亟待寻求适宜的新型屈光不正矫正技术. 目的 探讨可调节度数眼镜作为验光和矫正视力的方法应用于社区老年人初级眼保健筛查的可行性. 方法 采取前瞻性横断面研究方法,在上海市普陀区白玉社区6个居委会55岁以上老年人初级眼保健筛查现场用ETDRS LogMAR视力表检查视力,纳入任一眼日常生活视力＜0.5的受检者作为调查对象,进行自主可调节度数眼镜（Eyejusters眼镜）验光和矫正视力检查,并由专业视光医师行传统电脑自动验光和主觉验光法矫正视力,与Eyejusters眼镜验光和矫正视力结果进行比较.对纳入的受检者进行眼科检查,确定影响视力的原因;对自主调节验光矫正视力低于主觉验光最佳矫正视力（BCVA）2行及以上的影响因素进行分析.结果 参加社区日常生活视力检查者727人,日常生活视力任一眼＜0.5者338人,其中自愿验光者294人,占87.0％,平均年龄（70.4±177;8.6）岁,女性占64.3％.日常生活视力较好眼≥0.5者145人,占49.3％,经自主调节验光和主觉验光矫正视力后,人数分别增至230人（占78.2％）和258人（占87.8％）.日常生活视力＜0.5的443眼中,自主调节验光矫正视力≥主觉验光矫正视力的眼数为233眼（占52.6％）,低于1行的眼数为82眼（占18.5％）,低于2行及以上的眼数为128眼（占28.9％）.Logistic回归分析发现,自主调节验光矫正视力低于主觉验光2行及以上的影响因素为相对高的球镜和柱镜度数的绝对值,OR值分别为1.11 （95％ CI：1.02 ～1.20）和1.34（95％ CI：1.02 ～ 1.77）.自主调节验光矫正视力作为视力损伤判定指标的受试者工作特征（ROC）曲线下面积为0.941 （95％ CI：0.907 ～0.965）,最佳阳性界值为＜0.5,灵敏度为94.4％ （95％ CI：81.3％ ～99.2％）,特异度为88.4％ （95％ CI：83.8％ ～92.0％）.在自主可调节眼镜屈光范围内（自动电脑验光SE为-5.50～＋4.50 D）自主调节验光与主觉验光所得SE的Spearman相关系数为0.68（95％CI：0.59～0.76）,Bland-Altman分析发现,两者95％一致性界限为-3.4～＋2.6 D,相差幅度±0.50 D以内者占18.1％,相差±1.00 D以内者占47.0％,相差在±1.50D以内者占68.5％. 结论 老年人采用可调节度数眼镜矫正视力的结果可作为定性判定未矫正屈光不正简便、易行的指标,但可调节度数眼镜尚不宜作为验光工具定量检测屈光度.     

Further evidence that chick eyes use the sign of blur in spectacle lens compensation

Young animals compensate for defocus imposed by positive or negative spectacle lenses by adjusting the elongation rate of their vitreous chambers, thus matching the length of the eye with the focal length of the eye's optics combined with the spectacle lenses. The ability to compensate for either negative or positive lenses could rely on the ability to distinguish between myopic and hyperopic blur, or it could rely on the fact that positive lenses would bring nearby objects into focus, thereby reducing the amount of blur, whereas negative lenses would not. This study asks whether eyes emmetropize using the magnitude of blur or the sign of blur as a directional cue. We fitted chick eyes with positive lenses while imposing a substantial amount of blur, either (a) by having them wear lenses only when restrained in the center of a cylinder, the walls of which were beyond their far-point or (b) by having them wear mild diffusers over positive lenses. We found good refractive compensation in both situations in a large number of birds. Furthermore, we found that mild diffusers worn on top of positive lenses differentially affected the two ocular components of refractive compensation: there was less choroidal thickening, but more inhibition of ocular elongation, compared to wearing positive lenses alone. These findings argue both that the eye can discern the sign of the blur and that choroidal and ocular-elongation components of the refractive compensation do not respond identically to visual inputs.     

Optical models for human myopic eyes

Data from the author's investigations and other studies are used to construct refractive dependent models. These models include a gradient index lens and aspheric corneal, lens and retinal surfaces. Elements that alter with refraction are anterior corneal radius, vitreous length and retinal shape (vertex radius of curvature and asphericity) and decentration. Two versions of the models are produced, one with centred and symmetrical optical elements, and one with tilts of the lens and decentrations and tilts of the retina. The centred model predicts increase in spherical aberration in myopia. It predicts the relative change in mean sphere in the periphery between the horizontal and vertical meridians that has been observed in a recent experimental study. It overestimates peripheral astigmatism by about 50%. The decentred version has limited success in predicting changes in peripheral refraction of average eyes.     

框架眼镜矫正下周边屈光测量方法的研究

目的建立配戴框架眼镜时周边屈光的测量系统及方法,并检验其有效性,评估其可靠性。方法以Grand Seiko WAM－5500型自动验光仪为基础,将头托替换为自制的视角选择固定装置,增加弧形游动视标架,作为周边屈光的测量系统。并按照光路追迹原理搭建装置,测量框架眼镜周边部光线偏折引起的测量角度补偿量。使用上述改装的系统和角度校正方法测量35名近视者配戴框架眼镜时视网膜黄斑中心凹和鼻、颞侧偏离中央凹10°、20°、30°水平方向上7个点的屈光状态。并另招募35名近视者作为对照组,采用传统方法测量其裸眼状态时上述7个点的屈光度。比较两种方法测量值标准差的差异,评估其可靠性。结果①该系统和方法测量配戴框架眼镜时周边屈光的所得值标准差与传统测量方法所得值标准差的差异无统计学意义（P〉0．05）,说明其可靠性较好;②近视者框架眼镜矫正下视网膜周边部呈远视性离焦。结论本系统及方法用于屈光不正患者框架眼镜矫正下的周边屈光测量具有良好的可靠性和有效性。     

中学生近视周边部眼底退行性病变的流行病学特征

目的 了解中学生近视眼合并周边部眼底退行性病变的患病特点及其影响因素.方法 采取群体抽样的原则对豫东平原地区的五县市五所重点中学在校学生进行眼底流行病学调查,对其双眼屈光状况,视力及矫正视力,以及眼底病变等进行统计分析.结果 (1)共检出近视眼者3465人(72.6%),其中合并有各种周边部眼底退行性病变者488人,患病率为14.08%.(2)近视者中4.01%患有视网膜格子样变性,6.03%患霜样变性,3.2%患囊样变性,0.63%有裂孔.(3)低度近视者周边部眼底病变患病率为8.97%,中度近视者为20.09%,高度近视者为28.0%(x2=128,P<0.001).(4)自述有症状合并有周边部眼底退行性病变者的患病率为19.07%;无自觉症状者则为10.68%,(x2=47,P<0.001).(5)学生为城镇居民者合并患有周边部眼底退行性病变者的患病率为15.44%;为乡村居民者则为13.06%,(x2=2.3,P>0.05).结论 在校高中学生近视眼的发生率为72.6%.近视眼合并有周边部眼底退行性病变的患病率为14.08%,其患病率与近视程度和有无自觉症状相关.     

无屈光参差近视患者双眼周边屈光度分布

目的探讨双眼无屈光参差近视患者的周边屈光度分布状态。方法自身对照研究。选取2015年1-4月拟行准分子激光矫治的屈光状态稳定且无屈光参差的成年近视患者153例,睫状肌麻痹下使用Grand Seiko WAM5500型红外验光仪测量视网膜中心凹0°以及鼻颞侧15°、30°、45°的屈光度。采用配对t检验进行各项数据分析。结果无屈光参差近视患者右、左眼球镜度、柱镜度、等效球镜度（SE）在视网膜中心凹0°以及鼻颞侧15°、30°、45°各对应部位差异均无统计学意义（P>0.05）;右、左眼鼻侧15°的球镜度和SE与颞侧15°比较,差异有统计学意义（右眼：t=5.31、4.51,P<0.05;左眼：t=3.39、2.54,P<0.05）,并且颞侧45°的柱镜度明显大于鼻侧45°的柱镜度（t=4.95、3.74,P<0.05）,其他各对应部位差异均无统计学意义（P>0.05）;右、左眼鼻侧15°与视网膜中心凹0°球镜度、柱镜度、SE差异无统计学意义（P>0.05）,而其他部位屈光度与视网膜中心凹0°差异均有统计学意义（t=2.32~8.70,P<0.05）,越到周边,球镜度和SE出现远视性离焦,柱镜度逐渐增大。结论无屈光参差近视患者周边屈光度的分布在右、左眼相对应部位具有对称性;旁中心部,颞侧视网膜远视性离焦;越到周边部,远视性离焦程度越高;颞侧周边散光度明显大于鼻侧。     

Technical notes on peripheral refraction,peripheral eye length and retinal shape determination

Purpose

To give an overview of the misconceptions and potential artefacts associated with measuring peripheral refractive error and eye length, the use of these measures to determine the retinal shape and their links to myopia development. Several issues were identified: the relationship between peripheral refractive error and myopia development, inferring the retinal shape from peripheral refraction or eye length patterns, artefacts and accuracy when measuring peripheral eye length using an optical biometer.

Methods

A theory was developed to investigate the influence of artefacts in measuring peripheral eye length and on using peripheral eye length to make inferences about retinal shape.

Results

When determining peripheral axial length, disregarding the need to realign instruments with mounted targets can lead to incorrect field angles and positions of mounted targets by more than 10% for targets placed close to the eye. Peripheral eye length is not a good indicator of the effects of myopia or of treatment for myopia development because eyes of different lengths but with the same retinal shape would be interpreted as having different retinal shapes; the measurement leads to overestimates of changes in retinal curvature as myopia increases. Determining peripheral eye length as a function of estimated retinal height rather than field angle will halve the magnitude of the artefact. The artefact resulting from the peripheral use of biometers with an on-axis calibration is modest and can be ignored.

Conclusion

There are significant issues with peripheral measurements of the refractive error and eye length that must be considered when interpreting these data for myopia research. Some of these issues can be mitigated, while others require further investigation.     

Observation of peripheral refraction in myopic anisometropia in young adults

AIM: To investigate the differences in retinal refraction difference values (RDVs) of adult patients with myopic anisometropia compared with those without myopic anisometropia, and to investigate the relationship between ocular biometric measurements and relative peripheral refraction.METHODS: This clinical observation study included 130 patients with myopia (-0.25 to -10.00 D) between October 2022 and January 2023 aged between 18 and 40y. The patients were divided into anisometropia (n=63; difference in binocular anisometropia ≥1.00 D) and non-anisometropia (n=67; difference in binocular anisometropia <1.00 D) groups accordingly. Ocular biometric measurements were performed by optical biometrics and corneal topography to assess the steep keratometry (Ks), flap keratometry (Kf), axial length (AL), corneal astigmatism (CYL; Ks-Kf), surface regularity index (SRI), surface asymmetry index (SAI), and central corneal thickness (CCT). The RDV was measured at five retinal areas from the fovea to 53 degrees (RDV-0-10, RDV-10-20, RDV-20-30, RDV-30-40, and RDV-40-53), the total RDV (TRDV) of 53 degrees, and four regions, including RDV-superior, RDV-inferior, RDV-temporal, and RDV-nasal. An analysis of Spearman correlation was carried out to examine the correlation between RDV and the spherical equivalent (SE) and ocular biological parameters.RESULTS: Within RDV-20-53, both groups showed relative hyperopic defocus, and the increase in RDV corresponds to the increase in eccentricity. In the myopic anisometropia group, the TRDV, RDV-20-53, RDV-superior, and more myopic eyes had significantly higher RDV-temporal values than less myopic eyes. (P<0.05). In the non-anisometropia group, there was no significant difference in the RDV between the more and less myopic eyes at different eccentricities (P>0.05). There was a negative correlation between SE and TRDV (r=-0.205, P=0.001), RDV-20-53 (r=-0.281, -0.183, -0.176, P<0.05), RDV-superior (r=-0.251, P<0.001), and RDV-temporal (r=-0.230, P<0.001), a negative correlation between CYL and RDV-10-30 (r=-0.147, -0.180, P<0.05), and a negative correlation between SRI and RDV-0-20 (r=-0.190, -0.170, P<0.05). AL had a positive correlation with RDV-20-30 (r=0.164, P=0.008) and RDV-temporal (r=0.160, P=0.010).CONCLUSION: More myopic eyes in patients with myopic anisometropia show more peripheral hyperopic defocus. Diopter and corneal morphology may affect peripheral retinal defocus.