A common type of color vision test that can help determine general and specific inherited color vision deficits. It consists of a series of color plates in which the test taker is asked to identify numbers or geometric shapes composed of specific colors that are hidden within a field of spots of very similar colors. People with normal color vision can see the numbers or geometric figures while people with abnormal color vision cannot. See Ishihara Test Ishihara
The abnormal readings among 36 color blind subjects, i.e. those who read plate number 14 and 15 easier than 10 and 9 were 21 (58.3%). In reference with plates 16 and 17, from the total cases, 9 (1.05%) were strong deuteranopes (8 males, 1 female) and 4 were strong protanopes (4 males and no females) (Table 3).
A significant main effect of sex was obtained on the slope. The intercept also showed a tendency toward statistical difference. The interactions between the sexes and the day were not significant for the indices. Statistical testing for coefficient of variations (CV) indicated no sex-based difference in the effect of the intercept throughout the experiment day. The CV of the slope, however, showed tendencies toward sex-based difference from days 7 to 12.
Sex-based differences in the data were analyzed using repeated measure two-way analysis of variance. ANOVAs were performed using SPSS (version 22.0; IBM). The coefficient of variations (CV) (%) and the coefficient of determination (CD) were computed on each data by Microsoft Excel (version 2019, Microsoft). Significant differences between CVs were tested using the R package cvequality . Differences where p < 0.05 were considered statistically significant.
Figure 4 presents the CV (S.D./mean) for each index. Statistical testing for CV indicated no sex-based differences in the effects of the composite and intercept throughout the experiment day. The CV of the slope, however, showed tendencies toward sex-based difference (p < 0.1) from days 7 to 12.
SITA Standard 30-2 Humphrey Visual Field (HVF) revealed central scotomas OD and OS; however, testing was somewhat unreliable due to fixation losses. The mean deviations were -6.07 dB OD and -4.90 dB OS. (Figure 1) Optical coherence tomography (OCT, Stratus) macular testing was normal, but the scans were off-center with poor signal strength. Retinal nerve fiber layer (RNFL) evaluation with OCT revealed a small wedge of temporal thinning OD and was unreliable OS. The OCT scans were less than optimal due to poor patient fixation and technique.
The patient reported his vision was stable. He continued to receive cyanocobalamin 1000 mcg/mL intramuscularly. The MRI of the brain and orbits was unremarkable. His best-corrected visual acuity remained 20/400 OD and 20/400 OS and he was only able to see the test plate of the Ishihara color vision test OD and OS. The patient refused repeat HVF testing at this visit. Repeat RNFL OCT testing revealed stable temporal thinning OD and was unreliable OS. The plan was to continue intramuscular supplementation with cyanocobalamin.
The patient reported his vision had improved slightly since his last exam. He continued to receive cyanocobalamin 1000 mcg/mL intramuscularly. His best-corrected visual acuity improved to 20/80 OD and 20/80-2 OS. His color vision had also improved to 2/8 OD and 4/8 OS with Ishihara plates. HVF SITA Fast 24-2 revealed improved central defects with mean deviation OD: -1.57 dB and OS: -2.65 dB. (Table 2) Visual field testing was modified to the shorter 24-2 to improve patient cooperation.
Diagnosing B12 deficiency can be difficult based on serum B12 levels alone. Deceitfully normal levels can be seen in hepatic disorders, and falsely low levels can be seen in folate deficiency and pregnancy.4,12 It is helpful to measure methylmalonate and homocysteine, which are precursors in the B12 pathway, as 85% of patients with B12 deficiency will have elevated levels of these compounds.4 This is particularly useful when the B12 level is in the low- to borderline-low range.4 Additionally, a complete blood count with an elevated mean corpuscular volume (MCV) over 110 fl is also suggestive of vitamin B12 deficiency and warrants further testing.13
Evaluation of a patient with progressive vision loss in the presence of bilateral optic atrophy with central or cecocentral scotomas should include a detailed history including family and dietary backgrounds. The evaluation should include a thorough ophthalmic examination including careful pupillary examination, automated visual field assessment, color vision testing and OCT analysis. MRI of the brain and orbits is required to rule out compressive, ischemic, inflammatory, demyelinating and/or infiltrative etiologies. Laboratory testing should also be performed to rule out B12 deficiency.
Optic neuropathy refers to any condition in which the optic nerve is damaged. A targeted history and thorough ophthalmic examination is necessary to narrow down a list of probable diagnoses. Progressive, painless, bilateral loss of vision and temporal optic atrophy with central or cecocentral scotomas are signs and symptoms seen in a handful of miscellaneous optic neuropathies. These optic neuropathies can be further isolated with appropriate laboratory testing, imaging studies and a detailed patient history. While this list is not exhaustive, the most common differential diagnoses (Table 4) are:
This paper presents a rare case of partial visual recovery following vitamin B12 deficiency optic neuropathy. Most reports in the literature describe expectations for visual recovery from vitamin B12 deficiency optic neuropathy as guarded, citing time to diagnosis and treatment as the primary limiting factors.7,9,10,16 Improvement of visual symptoms is greatest with early and aggressive therapy.3 Interestingly, this patient recovered vision despite the presence of optic nerve pallor. In most circumstances, visual recovery does not occur once axonal loss has ensued and optic nerve pallor has formed.
This case report is intended to educate eyecare providers on the presentation and management of vitamin B12 deficiency optic neuropathy. It highlights the clinical importance of careful history, ophthalmic examination and use of ancillary testing. Since the advent of bariatric surgery, the importance of ophthalmic surveillance in the presence of vitamin deficiencies has been more frequently discussed in the literature.16 Additionally, Turkyilmaz et. al found that temporal quadrant retinal nerve fiber layer thickness correlates with plasma vitamin B12 levels.17 Eyecare providers should look beyond the eye and order appropriate lab work in light of pertinent ocular findings and be cognizant that incompletely treated vitamin B12 deficiency with oral supplementation with folic acid can aggravate neurological symptoms. Prompt diagnosis and recognition of vitamin B12 deficiency optic neuropathy is paramount to visual recovery.
A child can be successfully tested for color vision deficiency around age 4. At that age, he or she is developed enough to answer questions about what he or she sees. Many schools will perform color vision tests at an early age to determine if color-coded learning devices will be an issue. If so, alternative learning materials can be chosen. 2b1af7f3a8