比較外斜視兒童的慣用眼與非慣用眼的近視程度，非慣用眼的近視程度較高。
199位間歇性外斜視兒童，根據遠與近的斜視程度分為兩組，基本型(遠近斜視程度接近)與內聚不足型(近斜視明顯大於遠)。再進一步分類為屈光參差與非屈光參差。
結果
-內聚不足型之慣用眼等值球面度- 2.09 ± 1.45D，非慣用眼 - 2.53 ± 1.44D。
-基本型慣用眼等值球面度 - 2.46 ± 1.56D，非慣用眼 - 2.89 ± 1.37D 。
-兩組相同，慣用眼的近視程度顯著小於非慣用眼
其中屈光參差(雙眼屈光度差異大於等於1.00D)有43位，非屈光參差有156位。
-屈光參差組的近外斜量45.26 ± 24.41 PD，遠外斜量33.53 ± 23.31 PD
-非屈光參差組的近外斜量 43.42 ± 20.69 PD，遠外斜量 29.07 ± 16.84 PD
-兩組之間無顯著差異
62位8-12歲兒童分為四組，第一組結合使用0.01% atropine與OK鏡片，第二組使用安慰劑與OK鏡片，第三組使用0.01% atropine與鏡框眼鏡，第四組控制組使用安慰劑與鏡框眼鏡。
研究開始與三個月後，評估雙眼視覺功能，包括horizontal phoria, fusional vergence, the accommodative convergence/accommodation (AC/A) ratio, accommodative lag, and accommodative amplitude (AA)。
結果
1.調節遲緩僅OK鏡片組有顯著改進，其他三組未改變
Accommodative lag significantly decreased in the OK group (P = 0.002), but remained unchanged in the other three groups (all P > 0.05).
2.雙眼調節靈巧度與正相對調節在結合組與OK鏡片組有進步，其他兩組未改變
Binocular accommodative facilities and positive relative accommodations increased in the combination and OK groups (both P < 0.05) , but remained unchanged in the atropine and control groups (both P > 0.05).
3.僅OK鏡片組的內斜位有顯著降低。
Only the participants with esophoria in the OK group had a significant decrease in esophoria (P = 0.008).
4.融像性聚散與AC/A在四組間無顯著差異
Changes in fusional vergence and AC/A did not significantly differ between the four groups (all P > 0.05).
先說結論，"越遠越好"。教科書上的距離都是20英尺或6公尺，國內驗光人員法規定是最短5公尺，若用鏡子反射則最短2.5公尺。
太短會發生什麼問題呢? 這會牽涉到光聚散度、眼睛調節與屈光不正的原理，主要會有兩個問題產生。
一、所測視力有誤差
首先當物體離眼睛越近時，物體發出的光越呈現發散狀態，越遠越不會發散，無限遠則接近平行光。
再來說到屈光不正，例如近視眼是一種眼球屈光力過強的現象(因此須戴凹透鏡矯正)，當物體位於眼前近距離時，物體發散的光正好與近視眼球過強屈光力抵銷，因此近視眼的人在未戴眼鏡時，不須調節即能看清近距離物體。
所以輕微近視的人在較短驗光室內能輕鬆得到良好的視力。
但這是不正確的視力結果。
例如近視-0.50D眼睛在2公尺驗光距離，不戴眼鏡即有最佳視力；而若在5或6公尺以上距離的標準驗光室，光線不再發散，此時視力即會變差。
二、驗光距離太短還會造成另一個問題就是驗光的度數會有誤差
當物體較近時，光線會發散，此時眼睛為了看清楚會動用調節力提高眼睛屈光力。
這在驗光時就會造成問題。
驗光過程我們並不希望眼睛處於用力調節的狀態，所以在度數裡面就會加入一部分的正度數去取代眼睛所提高的屈光力，結果就是會驗出較低的近視度數或較高的遠視度數。
例如在標準距離的驗光室驗出-1.00D的近視眼，在2公尺的驗光距離若同樣戴-1.00D將使眼球必須用力0.50D，此時若換成-0.50D的眼鏡，眼睛反而不需用力，所以會被誤判為近視-0.50D。
當然驗光過程牽涉到非常複雜的設定與程序，檢查距離只是其中一個環節。
合法的驗光所都有標準的驗光距離及有執照的驗光人員，或者大家檢查眼睛時也可以自行判斷或詢問驗光室的距離(成年男子一步約60公分)，太近的話須用鏡子反射，否則將有一定的誤差會產生。
參考資料
PRIMARY CARE OPTOMETRY, 5th Theodore Grosvenor, O.D., Ph.D., F.A.A.O.
"Because rays of light diverging from a point 6m from the eye have a vergence of 0.17D on reaching the eye, "optometric infinity" differs from real infinity by an appreciable amount. When testing distances shorter than 6 m are used,what effect should we expect this to have on visual acuity?
As long as letter size is such that a 6/6 (20/20) letter subtends an angle of 5 minutes of arc at the spectacle plane,an emmetrope or an uncorrected hyperope with reasonable facility of accommodation would be expected to have no difficulty clearing up the letters at a distance less than 6 m.However, an uncorrected myope would be expected to have artificially high visual acuity under these circumstances.
For example, at a testing distance of 3 m (10 feet), a 0.33 D myope would be in perfect focus and would likely read at least one more line of letters than at the 6 m distance. In the experience of the author, visual acuity for uncorrected (and corrected) myopes becomes a problem for testing distances much closer than about 5 m (16 feet).
The effect of testing distance on visual acuity should not be confused with the effect of testing distance on refractive findings. For an acuity chart at 4 m, the vergence of light is 0.25 & for all patients, no matter what the refractive state, so myopes will tend to be underminused and hyperopes will tend to be overplussed. If the testing distance must be less than 20 feet, the use of a mirror system should be considered."
