Journal of Ophthalmology & Clinical Research Category: Clinical Type: Research Article
Clinical Contrast Sensitivity Function in Patients with Infantile Nystagmus Syndrome Before and After Eye Muscle Surgery
- Richard W Hertle1*, Dongsheng Yang2, Megan Cochran3, Priya R. Edward4
- 1 Childrens Hospital Vision Center, Akron Children’s Hospital, The Northeastern Ohio Medical University, Rootstown, Ohio, United States
- 2 Department Of Ophthalmology, Houlang Eye Hospital Chengsha, Hunan Province, China
- 3 Robinson Memorial Hospital, Columbus, Ohio, United States
- 4 Rainbow Babies And Childrens Hospital, University Hospital, Case Western Reserve University, Cleveland, Ohio, United States
*Corresponding Author:Richard W Hertle
Childrens Hospital Vision Center, Akron Children’s Hospital, The Northeastern Ohio Medical University, Rootstown, Ohio, United States
Tel:+1 3305358000 ,
Received Date: Jul 09, 2017 Accepted Date: Aug 24, 2017 Published Date: Sep 07, 2017
Methods: This is a prospective, interventional case series analysis of clinical data before and after eye muscle surgery in 113 patients who had no previous surgical treatment. Outcome measures included: 1) Routine demography and clinical characteristics, 2) Binocular best-corrected visual acuity in the null position and 3) Contrast sensitivity function. All patients data was collected for this study immediately pre-surgery and 2 to 6 months after surgery. Parametric and non-parametric statistical analysis of outcome measure data collected for this study were performed using standard software on grouped data using computerized software.
Results: Age ranged from 4-43 years (average 14 years), in which 63% were male. Follow-up, After surgery Follow-up the patient with an average of 13.1 months, although the study data was collected as described above,, 61% had associated afferent visual system disease, 71% had significant refractive error, 71% had strabismus, 62% had an associated anomalous head posture and 21% had associated (a) periodicity. Cumulative data from 113 patients and separate data from patients with either best binocular visual acuity < 20/80 or > 20/100 showed significant improved CS across all spatial frequencies tested.
Conclusion: Infantile nystagmus patients have deficient constrast sensitivity which may proved a measure of visual system dysfunction.This report supports the hypothesis that contrast sensitivity improves after eye muscle surgery in patients with infantile nystagmus and may be a useful outcome measure for future interventional clinical trials.
In addition to the above characteristics from 17% to 33% of patients with INS will have an inherent, rhythmic, periodic or (a) periodically changing nystagmus intensity and/or direction over time [2,3]. Most clinicians are familiar with this oscillation as acquired Periodic Alternating Nystagmus (PAN). Acquired PAN has a specific pattern identified by the presence of spontaneous nystagmus in the primary position, which beats horizontally in one direction for 1 or 2 minutes, followed by a quiet period, and then reappearance of the nystagmus in the opposite direction for a similar length of time. Infantile Aperiodic Alternating Nystagmus (IAPAN) has all the characteristics of INS except that the nystagmus direction and/or intensity changes in an irregular pattern over time. IAPAN also has the clinical characteristics of a dynamic, anomalous head posture and dynamically changing visual functions both over time and as a function of gaze [2,4].
Two broad areas of visual system treatment in infants and children with nystagmus and include treating their ametropia and ocular motor dysfunctions [5,6]. Common standard visual system treatment includes correction of refractive errors with spectacles, treatment of amblyopia, eye muscle surgery for strabismus, low vision devices and sunglasses. Although treatment of refractive error is standard of care, the use of devices such as specialized contact lenses is often not included. Likewise, treatment of strabismus and amblyopia is common, but associated treatment of nystagmus and its consequences are rare.
Previous studies have shown that results for letter acuity, vernier acuity and contrast sensitivity in some, but not all, subjects with INS is poorer than in normal observers under conditions of comparable retinal image motion [7-10]. This implies that contrast sensitivity may not be limited by the motion of the retinal image in some subjects with infantile nystagmus syndrome. There is psychophysical evidence that retinal motion may contribute to vision loss via an amblyopic component in patients with INS separate from ammetropic and strabismic components . High spatial frequency vision, i.e., Snellen acuity, may not be the best subjective measure of visual function in patients with disorders of the ocular motor system such as INS. Other subjective measures such as Contrast Sensitivity (CS), motion detection, gaze dependent visual acuity, visual reaction time, stereopsis, eye-hand and visual-vestibular coordination may more accurately represent measures that was affected by ocular motor disease and thus can be used as outcome variables in interventional clinical trials. This report details the outcome on contrast sensitivity after eye muscle surgery in the treatment of patients with INS after baseline spectacle correction.
The first step was to prescribe spectacle optical correction. Many patients presented either for the first time or for another treatment opinion who were not already in spectacles. The spectacles prescribed fully corrected myopia > 0.75 diopters, astigmatism > 1.50 diopters and anisometropia > 1.00 diopters and either fully corrected or symmetrically under-corrected (by up to 1.50 D) hyperopia of > +3.50 D (spherical equivalent). Spectacle-corrected distance visual acuity was measured at 3 meters in the patient’s habitual head position using the Amblyopia Treatment Study (ATS) HOTV protocol for patients < 7 years and the ATS ETDRS protocol for patients > 7 years of age at least every 4 ( +1 ) weeks after spectacle wear until acuity remained at within 1 line from the prior visit . This testing was accomplished in the patient’s eccentric null position if they did not have IAPAN and in primary position during the patient’s time of least intense nystagmus if they had IAPAN using the acuity testing protocols mentioned above [12-20]. The visit at which visual acuity remained stable became the baseline for all further measurements. All subsequent measures of visual acuity described below were obtained using the age-appropriate ATS protocol [11-20].
The goals of eye muscle surgery were to; simultaneously treat combinations of the patient’s strabismus, anomalous head posture and nystagmus with one operation. Standard methods of preoperative evaluation, anesthesia and fornix based eye muscle surgery were employed in the surgical treatment of all patients. The exact surgical procedure for each patient was based on the surgeon’s clinical experience and published reports detailing those used in the treatment of strabismus, anomalous head posture and nystagmus. The surgical procedures are outlined in table 1.
|Operation type (113 patients)||# (%)|
|Operation 1 - Horizontal head posture aloneHorizontal rectus recess and resect or recess and renotomy + Reattach||25 (22)|
|Operation 2 - Chin down head posture (+/- Strabismus)Superior rectus recess 5.0 mm + Inferior oblique myectomy||22 (20)|
|Operation 3 - Strabismus alonePrimary position deviation using at least two recti each eye||15 (13)|
|Operation 4 - Horizontal head posture + StrabismusFixing eye straightens head + Non-fixing eye straightens eyes||14 (12)|
|Operation 5 - Chin up head posture (+/- Strabismus)Inferior rectus recess 5.0 mm + Superior oblique tenectomy 5.0 mm||8 (7)|
|Operation 6 - No head posture, strabismus or vergence bampingHorizontal rectus tenotomy + Reattach||8 (7)|
|Operation 7 - Multiplanar head posture (+/- Strabismus)Transposition of recti + Combinations of oblique or recti recess||8 (7)|
|Operation 8 - Vergence damping alone (Artificial divergence)Medical rectus recess 3.0 mm + Lateral rectus tenotomy + Reattach||7 (6)|
|Operation 9 - Torsional head posture aloneHorizontal transposition of vertical recti 1 tendon width||6 (5)|
CLINICAL AND OCULAR MOTOR EVALUATION
|PT#||Age||STRAB||(A)PAN||EYE DX||Refractive Error|
|1||43.1||XT-HT||No||Amblyopia||(+3.00 +2.50 x 90 OU)|
|2||17||None||No||None||(+4.00+0.75 x 75OD, x 100 OS)|
|3||6||ET||Yes||Amblyopia||(+3.00 +4.50 x 90 OU)|
|4||8.1||ET||No||OCA||(+0.50 +3.75 x 90 OU)|
|5||6.7||None||No||None||(+2.00 +4.00 x 120 OD and x 60 OS)|
|6||8.5||ET||No||DVM||(+2.00 OD, +2.75 OS)|
|7||7.5||ET||No||OCA||(+2.25 +2.75 x 90 OU)|
|8||16.6||ET||No||RD||(+2.00 +2.00 x 45 OD, x 135 OS)|
|9||42.3||None||No||None||(+75 +1.75 x 90 OU)|
|10||25.1||ET||No||OCA||(-3.00 +1.50 x 90 OU)|
|11||41.2||None||No||None||(+3.00+3.50 x 90 OD, +2.00+2.75 x 90 OS)|
|13||17||ET||No||None||(+3.00 +4.50 x 90 OU)|
|14||12.1||None||No||None||(+1.50 +2.50 x 90 OU)|
|15||59.2||XT||No||RD||(-4.00 +2.50 x 150 OD, -4.00 +1.25 x 65 OS)|
|16||27.4||None||No||None||(-5.00 +.75 x 90 OD)|
|17||34.7||None||No||None||(-4.00 +0.75 x 180 OD, -4.75 +1.00 x 180 OS)|
|18||31.5||XT||Yes||None||(PL +4.50 x 90 OD, PL +5.00 x 90 OS)|
|19||38||ET||No||Amblyopia||(-1.00 +4.50 x 45, -0.75 +3.00 x 135 OS)|
|20||42.7||None||No||None||(-1.00 +2.00 x 90 OU)|
|21||31||ET||Yes||OCA||(+3.00 +6.50 x 45 OD, x 135 OS)|
|22||6.5||ET||No||None||(PL +5.50 x90 OU)|
|23||27.2||None||No||OCA||(-5.00 + 1.00 x 135 OD, x 45 OS)|
|24||3.1||ET||Yes||None||(+2.50 +4.50 x 125 OD, x 60 OS)|
|25||16.8||None||No||None||(-7.50 +2.25 x 90 OU)|
|26||38.6||ET||Yes||RD||(+1.00 +3.75 x 60 OD, x 120 OS)|
|27||7.2||None||No||None||(+4.50 +1.25 x 90 OD, x 135 OS)|
|28||18||ET||No||FOV HYP||(+3.00 +3.00 x 90 OD, +3.75 +4.00 x 135 OS)|
|30||10.2||None||Yes||RD||(-7.50 +1.00 x 90 OU)|
|31||4.1||None||No||None||(+5.75 OD, +5.00 OS)|
|32||13||XT||No||OCA||(-8.50 +2.50 x 90 OU)|
|33||5.7||XT||No||Amblyopia||(-3.50 +4.50 x 110 OD, x 70 OS)|
|34||33||None||No||None||(+1.25 +4.25 x 90 OU)|
|35||4.5||ET||No||None||(-2.00 +4.00 x 45 OD, -2.25 +3.25 x 110 OS)|
|37||15||ET||Yes||Aphakia||(+11.50 +4.00 x 90 OD, x 120 OS)|
|38||6||ET||No||OCA||(-5.00 +3.50 x120 OD, -4.00 +4.00 x 60 OS)|
|40||4||ET-HT||Yes||Amblyopia||(-0.50 +1.75 x 175 OD, x 10 OS)|
|41||5||None||No||None||(-0.75 +2.50 x 140 OD, -1.00 +3.00 x100 OS)|
|42||11||ET||Yes||FOVE HYO||(+5.50 +2.00 x 90 OD, +5.75 +2.00 x 10 OS)|
|43||8.5||None||No||OCA||(+2.00 +1.00 x 90 OU)|
|44||15||ET||No||OCA||(-5.00 +4.00 x 135 OD, x 85 OS)|
|45||10||None||No||CVI||(-3.00 +0.75 x 85 OD, -4.50 +1.00 x 100 OS)|
|46||6.5||ET||No||None||(+2.00+2.50 x 90 OU)|
|47||7||ET||Yes||Amblyopia||(+.75 +2.75 x 90 OU)|
|48||9.5||ET||No||None||(+4.00 +1.00 x 90 OD, +3.00 +0.50 x 90 OS)|
|49||5||ET-HT||No||OCA||(-4.00 +3.00 x 90 OU)|
|50||8.3||None||Yes||DVM,CVI||(-0.75 +.75 x 160 OD, x 20 OS)|
|51||12.5||None||No||None||(-0.50 +2.50 x 90 OU)|
|52||8.5||ET||Yes||RD||(+6.50 OD, +1.75 +1.75 x 140 OS)|
|53||8.5||XT-HT||No||FOV HYP||(+6.25 +1.25 x 90 OD, x 100 OS)|
|54||8.5||ET||No||OCA||(-2.00 +4.50 x 45 OD, x 135 OS)|
|55||3.5||None||Yes||None||(-2.50 +2.50 x 90 OD, PL +1.00 x 90 OS)|
|56||5.4||ET||No||None||(-1.25 +2.75 x 45 OD, -2.50 +1.00 x 135 OS)|
|57||30.4||ET||No||OCA||(+6.00 +1.75 x 105 OD, +5.75+1.75 x 90 OS)|
|58||7||None||No||None||(-5.50 +1.75 80 OD, -4.75 +1.00 x 180 OS)|
|59||4||XT||Yes||ONH||(-5.00 +2.00 x90 OU)|
|60||3.4||None||No||OCA||(+2.50 +4.50 x 90 OU)|
|61||57||None||No||None||(+1.00 +4.00 x 45 OD, x 135 OS)|
|62||4.5||None||No||ONH||(-5.00 +2.00 x 80 OD, -8.00 +3.00 x 75 OS)|
|63||47||ET||Yes||Aphakia||(+14.50 +2.75 x120 OD, +15.25 +3.25 x60 OD)|
|64||35||ET||No||RD||(-3.25 +2.50 x 115 OD, -4.50 +1.75 x 110 OS)|
|65||16||None||No||OCA||(+4.50, OD +3.25 OS)|
|66||8.5||ET||No||FOV HYP||(-4.00 +3.50 x 80 OD, -4.00 +4.00 x 90 OS)|
|67||14||ET||Yes||Amblyopia||(+6.75 +2.25 x 90 OU)|
|68||44||None||No||OCA||(-3.00 +1.00 x 185 OD, -3.50 +1.50 x 170 OS)|
|69||4||None||No||None||(-4.25 +3.25 x 60 OD, +2.75 +3.50 x 120 OS)|
|70||8||XT-HT||No||RD||(-2.50 +5.75 x 15 OD, -1.50 +6.00 x 125 OS)|
|71||42||XT||No||Amblyopia||(-3.00 +3.25 x 45 OD, -3.50 +2.75 x 135 OS)|
|72||6.6||XT||No||Amblyopia||(-1.00 +2.25 x 115 OD, -,25 +4.25 x 90 OS)|
|73||35||ET||Yes||OCA||(-4.00 +3.00 x 120 OD, -2.50 +3.25 x 60 OS)|
|74||23||None||No||None||(-3.75 +4.00 x 90 OD, -3.25 +4.00 x 90 OS)|
|75||7.1||ET||Yes||DVM,CVI||(+3.50 +4.75 x 70 OD, +3.75 +5.00 x 110 OS)|
|76||33.5||ET-HT||No||None||(-12.00 +3.00 x 60OD, -16.00 +4.25 x 120 OS)|
|77||11||ET||Yes||Amblyopia||(+6.50 +2.00 x 90 OD, +5.75 +1.75 x 90 OS)|
|78||8||ET||No||OCA||(-8.50 +4.25 x 115 OD, -7.75 +3.50 x 110 OS)|
|79||4.5||None||No||OCA||(-4.00 +0.75 x 180 OD, -4.75 +1.00 x 180 OS)|
|80||7||ET||No||Amblyopia||(+0.75 +2.75 x 90 OU)|
|81||9.5||ET||Yes||OCA||(+4.00 +1.00 x 90 OD, +3.00 +.50 x 90 OS)|
|82||5||ET||No||None||(-4.00 +3.00 x 90 OU)|
|83||8.3||None||No||CVI. DVM||(-0.75 +0.75 x 160 OD, x 20 OS)|
|84||12.5||None||No||OCA||(-0.50 +2.50 x 90 OU)|
|85||8.5||ET||Yes||FOV HYP||(+6.50 OD, +1.75 +1.75 x 140 OS)|
|86||8.5||XT-HT||No||OCA||(+6.25 +1.25 x 90 OD, x 100 OS)|
|87||3.6||XT||No||RD||(+3.50 +4.75 x 70OD,+3.75 +5.00 x110 OS)|
|88||5.8||XT||No||None||(-3.00 +2.00 x 90 OU)|
|89||26||ET||No||Amblyopia||(PL +3.50 x 90 OD, +1.75 +3.00 x 90 OS)|
|90||13||ET||No||None||(+5.25 +1.25 x 90 OU)|
|91||11||ET-HT||No||OCA||(-6.50 +1.00 x 45 OD, x 135 OS)|
|92||6.3||XT-HT||No||FOV HYP||(+2.00 +4.00 x 90 OU)|
|93||6.3||XT-HT||Yes||FOV HYP||(+2.00 +4.00 x 90 OU)|
|94||7||None||No||OCA||(+0.75 +2.75 x 90 OU)|
|95||9.5||ET||No||Amblyopia||(+4.00 +1.00 x 90 OD, +3.00 +.50 x 90 OS)|
|96||5||None||No||OCA||(-4.00 +3.00 x 90 OU)|
|97||8.3||ET||Yes||ONH||(-0.75 +.75 x 160 OD, x 20 OS)|
|98||12.5||None||No||None||(-0.50 +2.50 x 90 OU)|
|99||8.5||None||Yes||None||(+6.50 OD, +1.75 +1.75 x 140 OS)|
|100||8.5||XT-HT||No||RD||(+6.25 +1.25 x 90 OD, x 100 OS)|
|101||31.5||XT||No||OCA||(PL +4.50 x 90 OD, PL +5.00 x 90 OS)|
|102||38||ET||No||Amlbyopia||(-1.00 +4.50 x 45, -0.75 +3.00 x 135 OS)|
|103||42.7||XT||No||OCA||(-1.00 +2.00 x 90 OU)|
|104||31||ET||Yes||ONH||(+3.00 +6.50 x 45 OD, x 135 OS)|
|105||6.5||ET||No||OCA||(PL +5.50 x 90 OU)|
|106||27.2||None||No||None||(-5.00 + 1.00 x 135 OD, x 45 OS)|
|107||3.1||ET||No||ONH||(+2.50 +4.50 x 125 OD, x 60 OS)|
|108||16.8||None||No||OCA||(-7.50 +2.25 x 90 OU)|
|109||8.6||ET||No||Aphakia||(+18.00 +3.75 x 60 OD, x 120 OS)|
|110||7.2||ET||No||OCA||(+4.50 +1.25 x 90 OD, x 135 OS)|
|111||18||ET||No||None||(+3.00 +3.00 x 90OD, +3.75 +4.00 x135OS)|
|112||18||None||No||OCA||(+3.00 +3.00 x 90OD,+3.75+4.00x 135 OS)|
Visual acuity testing at the null position
Eye movement recordings
Contrast Sensitivity testing (CS)
Contrast sensitivity (CS)
|Frequency/Exam||Mean +/- SD||Median||Minimum||Maximum||P value <|
|Postop||1.53 + 0.38||1.24||0.7||1.95|
|Preop||0.87 + 0.56||0.68||0.68||1.77|
|Postop||1.66 + 0.29||1.44||1.01||2.11|
|Preop||0.62 + .026||0.33||0.23||1.01|
|Postop||0.96 + 0.24||0.87||0.88||1.47|
|Preop||0.23 + 0.22||0.11||0.11||0.91|
|Postop||0.92 + 0.27||0.89||0.89||1.55|
This table summarized the group mean response to CS testing with the CSV 1000R chart at each of the four testing stimuli for the entire cohort. There were significant group mean improvements in all four spatial frequency targets after treatment. Frequency = Cycles/degree test pattern, Exam - Baseline or final, +/- SD - Standard deviation, cpd* - Cycles per degree. CS values were documented in Log Units (LU). Sensitivity levels at each frequency ranged from 0.70 to 2.08 LU for 3 cpd, 0.91 to 2.29 LU for 6 cpd, 0.61 to 1.99 LU for 12 cpd and 0.17 to 1.55 LU for 18 cpd.
|Frequency/Exam||Mean +/- SD||Minimum||Maximum||P Value <|
|Preop||0.82 + .50||0.4||1.55|
|Postop||1.66 + .65||0.98||1.95|
|Preop||0.99 + 0.47||0.68||1.84|
|Preop||0.70 + 0.39||0.3||1.31|
|Postop||1.16 + 0.24||0.91||1.71|
|Preop||0.19 + 0.22||0.13||0.21|
|Postop||0.68 + 0.27||0.61||1.31|
This table summarized the group mean response to CS testing with the CSV 1000R chart at each of the four testing stimuli of those 69 patients with acuity > 20/80 (LogMar 0.60). There were significant group mean improvements in all four spatial frequency targets after treatment. Frequency - cycles/degree test pattern, Exam - Baseline or final, +/- SD - Standard deviation, cpd* - Cycles per degree. CS values were documented in Log Units (LU). Sensitivity levels at each frequency ranged from 0.70 to 2.08 LU for 3 cpd, 0.91 to 2.29 LU for 6cpd, 0.61 to 1.99 LU for 12 cpd and 0.17 to 1.55 LU for 18 cpd.
|Frequency/Exam||Mean +/- SD||Minimum||Maximum||P Value >|
|Preop||0.53 + 0.21||0.4||1.01|
|Postop||1.46 + 0.43||0.68||1.95|
|Preop||0.71 + 0.27||0.6||1.22|
|Postop||1.59 + 0.33||1.11||1.88|
|Preop||0.78 + 0.39||0.3||0.91|
|Postop||1.01 + 0.24||0.87||1.61|
|Preop||0.13 + 0.08||0.09||0.2|
|Postop||0.98 + 0.29||0.41||1.33|
This table summarized the group mean response to CS testing with the CSV 1000R chart at each of the four testing stimuli of those 69 patients with acuity < 20/100 (Log Mar 0.70). There were significant group mean improvements in all four spatial frequency targets after treatment. Frequency - Cycles/degree test pattern, Exam - Baseline or final, +/- SD - Standard deviation, cpd* - Cycles per degree. CS values were documented in Log Units (LU). Sensitivity levels at each frequency ranged from 0.70 to 2.08 LU for 3 cpd, 0.91 to 2.29 LU for 6 cpd, 0.61 to 1.99 LU for 12 cpd and 0.17 to 1.55 LU for 18 cpd.
Traditional visual system treatment of patients with INS includes spectacles, routine amblyopia and strabismus management. In the classroom, preferential seating, lighting, computer assisted devices and handouts of board written content are helpful aids.
There is no cure for many of the visual sensory system deficits that are associated with INS. Treatment directed specifically at the nystagmus would have as its goal to increase the quality and quantity of foveation periods, thereby, increasing the potential for more time and gaze angles during which best visual function could take place [25,33]. There is a large body of data supporting the hypothesis that foveation periods occurring during each beat of nystagmus can be lengthened or increased by therapeutic interventions (i.e., medicines, surgery, contact lenses, etc.) [12-20]. Quantitating these foveation periods is accomplished with accurate, calibrated, eye movement recordings using various foveation programs. The improvement in INS applies both to patients with and without associated sensory-system defects. Ocular motor and visual system benefits have been shown to be consistently observed in patients who undergo eye muscle surgery for INS, even if the purpose was to decrease torticollis or improve strabismus [12-20].
Several reports suggest it is clinically reasonable to measure CS to assess visual system disability in patients with multisystem vision disease [21,34-37]. Anatomical and electrophysiological anomalies found in human albinos are reflected by reduced contrast sensitivity. Testing of CS in patients with INS has repeatedly shown it to be abnormal [21,34-37]. High astigmatic errors, nystagmus and other retinal/neural anomalies may result in abnormal meridional differences in sensitivity. Previous reports have also shown an increase in peak CS in INS patients while using telescopes and other low vision aids. The data from this report supports deficient CS in INS patients and the potential for subsequent improvement after visual system treatment.
The approach outlined in table 1 to eye muscle surgery in INS1 patients was developed as a result of a need to improve multiple pre-operative ocular motor and/or visual system abnormalities in the patient population with INS [14,17,18]. This 9-operation system allows the clinician to maximize surgical intervention by performing one procedure to address all possible indications, e.g., eye position, head/face position and nystagmus characteristics. This surgical algorithm is based on standard eye muscle surgical techniques and is easily applicable in most clinical situations. The data from this study add to others that have shown that INS patient’s strabismus and anomalous head posture can be improved after eye muscle surgery in the same way as other populations of patients with strabismus.
Although the patients reported here consist one of the largest prospective treatment cohorts of INS patients, this remains level 2-3 evidence at best. The data reported in this study showed significant improvements in BVA and CS from baseline to post surgery, suggesting that these measures of visual function can be improved in patients with INS after surgical treatment. Although group means showed improvement in visual acuity, individual patient acuity may have varied +/- 0.1 logMar based on chance alone. This is inherent in the testing methodology and age of the patients involved in this report and the reason we chose to perform group mean analysis. These surgical procedures are not novel, and also the treatment of the visual system of patients with INS. This study has shown that the use of standard surgical, treatments of patients with INS significantly improves their contrast sensitivity function.
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Citation: Hertle RW, Yang D, Cochran M, Edward PR (2017) Clinical Contrast Sensitivity Function in Patients with Infantile Nystagmus Syndrome Before and After Eye Muscle Surgery. J Ophthalmic Clin Res 4: 033.
Copyright: © 2017 Richard W Hertle, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.