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British Journal of Healthcare and Medical Research - Vol. 10, No. 2
Publication Date: April 25, 2023
DOI:10.14738/jbemi.102.14226.
Vats, V., Gupta, P., Hasan, M. G., Kundu, A., & Raturi, S. (2023). Comparison of Optic Disc on Machine (OCT) Versus Manual
Assessment on Slit Lamp. British Journal of Healthcare and Medical Research, Vol - 10(2). 97-103.
Services for Science and Education – United Kingdom
Comparison of Optic Disc on Machine (OCT) Versus Manual
Assessment on Slit Lamp
Dr. Vatsala Vats
Associate Professor, Department of Ophthalmology,
Shri Guru Ram Rai Institute of Medical and Health Sciences Dehradun, Uttarakhand
Dr. Priyanka Gupta
Associate Professor, Department of Ophthalmology,
Shri Guru Ram Rai Institute of Medical and Health Sciences Dehradun, Uttarakhand
Dr. Mohd. Ghainual Hasan
Assistant Professor, Department of Ophthalmology,
Shri Guru Ram Rai Institute of Medical and Health Sciences Dehradun, Uttarakhand
Dr. Ashish Kundu
Junior Resident, Department of Ophthalmology,
Shri Guru Ram Rai Institute of Medical and Health Sciences Dehradun, Uttarakhand
Dr. Shivani Raturi
Junior Resident, Department of Ophthalmology,
Shri Guru Ram Rai Institute of Medical and Health Sciences Dehradun, Uttarakhand
Abstract
Background and Objectives: OCT is an evolving tool of diagnosing various
anatomical anomalies of eye specially for retinal parameters and also gaining a
strong role in other structures like cornea, angle, optic disc. But its cost and
incorporation of newer technology with time becomes a dilemma for its purchase.
The subjective assessment of optic nerve head (ONH) with the help of 90 dioptre, or
78 dioptre lens on slit lamp, or direct ophthalmoscope are methods in common
clinical practice in most ophthalmic settings. Such manual assessment forms the
core of the strategic approach to diagnose optic disc variations. This study aimed to
learn if objective tool like OCT could do away the subjective method. Material and
Method: All eyes underwent comprehensive ophthalmic evaluation including visual
acuity, slit lamp biomicroscopy, tonometry, and OCT. The optic disc was assessed on
slit lamp by 78 D as the morphology appeared close to natural dimensions. Disc size,
NRR, C:D ratio noted on OCT were compared with the readings of manual method.
Study Design: A cross sectional, hospital based, prospective study involving 200
eyes of 100 patients. Result: In our study, we found that the size was significantly
more on OCT than manual assessment on slit lamp with 78 dioptre lens. Glaucoma
Suspect eyes on slit lamp were found to have suspicious discs even on OCT in almost
90% eyes. Interpretation & Conclusion: Subjective assessment is mandatory for
diagnostic purposes as it is vivid, and is easily available on account of low cost. OCT
is additive of information of structures not visible to human eye directly. A proper
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British Journal of Healthcare and Medical Research (BJHMR) Vol 10, Issue 2, April- 2023
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combination of OCT and SLB brings specificity and clarity to both the patient and
clinician.
Keywords: Optic disc, Glaucoma, OCT, Glaucoma Suspect
INTRODUCTION
Optical Coherence Tomography (OCT) is a noninvasive technology that works by passing a
beam of laser-generated light, with a wavelength in the infrared range, through a tissue and
analyzing the reflected fraction. Already indispensable for retinal analysis, OCT is now
becoming essential for glaucoma and other optic neuropathies, to evaluate axonal integrity, to
assess disease progression in the afferent visual pathway and to predict visual recovery after
surgery in compressive optic neuropathies. Also, OCT testing is considered a powerful
biomarker of neurodegeneration and a promising outcome measure for neuroprotective
trials.
[1,2] Even when the progression of the glaucomatous damage has been known to be subtle,
nevertheless, the OCT scans have been shown to differentiate between healthy and glau- comatous eyes using Retinal Nerve Fibre Layer (RNFL) measurements.
[3,4] The use of the
clinically invisible Bruch’s Membrane Opening (BMO) to define the border of the optic disc
margin, accurately and repeatedly with OCT, has also made the measurements more
diagnostic.
[5]. The improvement in the resolution of the device has resulted in better
segmentation of the retinal layers and better test-retest repeatability.
[6] The drawbacks of the
device lie in over or under estimation of rim tissue, which depends on the orientation of the
machine.
[7,8] The manual assessment of the disc with the help of ophthalmoscope is
indispensable as it is vivid, economical, and feasible in most circumstances. Through this study,
we try to draw comparisons in the measurement of disc parameters taken manually versus
those noted on OCT.
OBJECTIVES
1. To document Cup Disc ratio (C:D) by Slit Lamp Biomicroscopy (SLB) and OCT
2. To record the Glaucoma Suspect discs by SLB and OCT and compare.
3. To note the width of Neuro Retinal Rim (NRR) on OCT
MATERIAL AND METHOD
It is a prospective, cross- sectional, hospital-based study. Ethics Committee approval was
obtained for the study that was conducted in a tertiary care hospital of northern India from
August 2021 to December 2021. All patients more than 18 years of age visiting the Out Patient
Department (OPD) and willing to participate were enrolled in the study. Eyes with history of
trauma, surgery, laser, or retinal pathology were excluded from the study.
All eyes underwent comprehensive ophthalmic examination including visual acuity testing,
SLB, indirect ophthalmoscopy, intra ocular pressure on non-Contact tonometry (NIDEK NT- 530P) and OCT(RS-3000) examinations. The optic disc was seen on slit lamp by 78 D as the
morphology appeared close to natural dimensions. The disc was than assessed on OCT after
proper dilation. Disc size, NRR, C:D ratio was noted and compared with the readings of manual
method.
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Vats, V., Gupta, P., Hasan, M. G., Kundu, A., & Raturi, S. (2023). Comparison of Optic Disc on Machine (OCT) Versus Manual Assessment on Slit
Lamp. British Journal of Healthcare and Medical Research, Vol - 10(2). 97-103.
URL: http://dx.doi.org/10.14738/jbemi.102.14226
STATISTICAL ANALYSIS
The data was analyzed using Student t test and Chi square test. p-Value less than 0.5 was
considered significant.
RESULT
200 eyes of 100 patients ranging from 18 to more than 65 years were analyzed. There were 71
females, and 29 males. 29% of the patients belonged to the age group of 36 to 45 years. The
vision recorded was better than 6/18 in 70% right and 73% and only 3 right (3%) and 3 left
(3%) eyes had vision less than 6/60.
The minimum vertical C:D found on SLB was 0.20, equal to the minimum vertical C:D ratio
recorded on OCT. However, the maximum vertical C:D on SLB was noted to be 0.7 with respect
to 0.89 recorded on OCT. The mean Vertical C:D was 0.41 on SLB while the value was 0.52 on
OCT. The difference was statistically significant with a p-Value 0.000. Similarly, the mean
vertical C:D ratio in left eyes was found to be 0.43, compared to 0.53 on OCT and the difference
was significant with a p-Value of 0.000. (Table 1)
Variable Minimum Maximum Mean Std. Deviation t-test
(‘p’ value)
VC:D Right
eye SLB
0.20 0.70 0.4141 0.11293
-5.671
(0.000)
VC:D Right
eye OCT
0.20 0.89 0.5149 0.13726
VC:D Left eye
SLB
0.20 0.70 0.4266 0.12649
-5.301
(0.000)
VC:D Left eye
OCT
0.29 0.97 0.5336 0.15730
Table 1: Vertical Cup Disc ratio (C:D) with IDO and OCT
VC:D = vertical cup disc ratio; SLB= slit lamp biomicroscopy; OCT=optical coherence tomography,
IDO= Indirect ophthalmoscopy
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British Journal of Healthcare and Medical Research (BJHMR) Vol 10, Issue 2, April- 2023
Services for Science and Education – United Kingdom
The minimum and maximum C:D on SLB was found to be similar to vertical C:D as 0.20, and
0.70 respectively. However, the mean of horizontal C:D in right eyes was 0.42 as compared 0.57
to mean horizontal C:D on OCT and the difference was significant with a p-Value less than 0.000.
Even among left eyes, the mean C:D on SLB was 0.43, while 0.58 on OCT and the difference was
significant. (Table 2)
On SLB, 34 right and 38 left eyes were glaucoma suspect. On OCT, 63 right, and 58 left eyes had
a vertical C:D suspicious of glaucoma. (Table 3)
VC:D<0.5 VC:D≥0.5
VC:D RE SLB 66 34
HC:D RE SLB 63 37
VC:D RE OCT 37 63
HC:D RE OCT 33 67
VC:D LE SLB 62 38
HC:D LE SLB 61 39
VC:D LE OCT 42 58
HC:D LE OCT 34 66
Table 3: Glaucoma Suspect Eyes
HC:D = horizontal cup disc ratio; VC:D = vertical cup disc ratio; SLB= slit lamp biomicroscopy;
OCT=optical coherence tomography; RE=right eye; LE= left eye
Table 4: Comparison between SLB and OCT of Glaucoma Suspect Eyes
Among 34 glaucoma suspect right eyes SLB, 31(91.2%) showed similar findings on OCT (Table
4 and Table 5). Likewise, among 38 glaucoma suspect left eyes, 35(92.1%) showed similar
findings on OCT (Table 6 and Table 7). Conversely, among 63 glaucoma suspect eyes on OCT,
only 31(49.2%) had similar findings on SLB. Among 58 glaucoma suspect left eyes on OCT, just
35(60.3%) eyes had similar findings.
Variable Minimum Maximum Mean Std. Deviation t-test
(‘p’ value)
HC:D Right
eye SLB
0.20 0.70 0.4210 0.11393
-7.867
(0.000)
HC:D Right
eye OCT
0.30 0.97 0.5731 0.15622
HC:D Left eye
SLB
0.20 0.70 0.4326 0.12904
-7.044
HC:D Left eye (0.000)
OCT
0.30 0.96 0.5805 0.16562
Table 2: Horizontal Cup Disc ratio (C:D) with SLB and OCT
HC:D = horizontal cup disc ratio; SLB= slit lamp biomicroscopy; OCT=optical coherence tomography