| Abstract |
Purpose : The main purpose of the study was to evaluate the effects of anisometropic
amblyopia upon the macular light sensitivity threshold and macular integrity. The
technique of microperimetry was used to assess the macular light sensitivity threshold
along with the macular integrity index and fixation stability.
Method : This is a prospective study involving anisometropic amblyopic (either
hyperopic or myopic) patients and healthy subjects consisting the control group. The
amblyopes underwent cycloplegia (and mydriasis) using cyclopentolate (1%). Best
corrected visual acuity (BCVA) and refractive correction were measured in conditions
of cycloplegia. The recording of macular light sensitivity threshold was performed
using the technique of static microperimetry (Maia-expert test). All measurements
within the patients group were made by occluding the fellow eye during the
examination, while in the control group the same measurements were performed in
both stereo and non-stereo status. For the control group inclusion criteria were BCVA
equal to 0,0 logMAR or better for both eyes and absence of any ocular abnormality,
while for the patients group inclusion criteria were presence of any type of
anisometropic amblyopia combined with significant interocular difference in BCVA
between two eyes and absence of any other ocular abnormality or previous eye
operation.
Results : Eventually in the study participated 11 healthy subjects, average age of
control group was 27,64±4,27 years, average spherical equivalent of the dominant eye
was measured -0,55±1,95 dpt and of the non-dominant eye -0,64±2,15 dpt. Average
threshold values (±SD) of the dominant eye were 31,19±0,74 dB and 31,3±0,93 dB
for stereo and non-stereo vision respectively. Average threshold values (±SE) of the
non-dominant eye were 31,19±0,68 dB and 31,36±0,76 dB for stereo and non-stereo
vision, respectively. A paired samples t-test within the control group, revealed that the
factors of viewing condition (dominant/non-dominant) and stereo/non-stereo
observation had no significant effect upon the measured threshold values. The patient
group consisted of 24 anisometropic amblyopic patients (12 hyperopic amblyopes and
12 myopic amblyopes) of average age: 28,33±10,98 years. Amblyopic eye : average
[6]
spherical equivalent±(SE) was -1,48±6,14 dpt and average best corrected visual acuity
(BCVA) 0,35±0,21 logMAR. Non-amblyopic eye : average spherical equivalent (SE)
-0,15±2,88 dpt and average best corrected visual acuity (BCVA) 0,01±0,05 logMAR.
Average threshold values (±SE) were measured 27,54±2,32 dB and 29,46±1,93 dB
for the amblyopic and non-amblyopic eye, respectively. The threshold value of the
amblyopic eye was significantly lower for greater amounts of anisometropia ( r= -
0,722, p= 0,000). Greater differences in threshold values between amblyopic and nonamblyopic
eye weren’t correlated marginally with greater differences in BCVA
between the same eyes (p=0,077).
The threshold value of the amblyopic eye was found to be fairly lower compared
with the fellow eye (mean difference=1,93 dB, p=0,000 /paired sample t-test) and
compared with the dominant eye of the control group (mean difference=3,76 dB,
p=0,000 /independent sample t-test). Plus an analysis of covariance (ANCOVA)
revealed that age had no significant effect on these differences (p=0,46). Interestingly,
the threshold value of the non-amblyopic eye was found to be lower (mean
difference=1,84 ,p=0,004) compared to that of the dominant eye (control group) with
age-factor having significant effect upon this difference (p=0,021).
Conclusion: Anisometropic amblyopia can lead to the reduction of macular
sensitivity threshold but it is unlikely to result in serious deficits in the visual field.
Microperimetry can be used as a method (along with VA measures) to evaluate the
severity of various types of amblyopia.
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