|Year : 2018 | Volume
| Issue : 3 | Page : 191-195
Assessment of quality and quantity of vision in astigmatic patients with tilted disc: a comparative study
Nehal M Samy El Gendy
Department of Ophthalmology, Kasr Alainy Medical School, Faculty of Medicine, Cairo University, Giza, Egypt
|Date of Submission||08-Dec-2017|
|Date of Acceptance||06-Jun-2018|
|Date of Web Publication||24-Sep-2018|
Nehal M Samy El Gendy
Kasr Alainy Medical School, Cairo University, 43 Gameat El Dewal El Arabia Street, El Mohandeseen District, Giza 12411
Source of Support: None, Conflict of Interest: None
Purpose The purpose of this article was to compare the quality and quantity of vision in cases with corneal astigmatism with and without tilted disc.
Patients and methods Cases with astigmatic error between 1 and 3 D with and without tilted disc were included in the present study. Quantity of vision, in the form of uncorrected and corrected distance visual acuities, was compared. Quality of vision questionnaire, designed by McAlinden et al. in 2010, was used, and the results compared between the two groups. Higher order aberrations were also compared.
Results Sixty eyes of 60 patients were included (30 eyes in each group). Uncorrected distance visual acuity was significantly lower in tilted disc group (Log MAR: 0.8±0.2) versus 0.5±0.2 in the group without tilted disc (P=0.04). Coma and trefoil values were also significantly higher in tilted disc group (0.4±0.1 vs. 0.2±0.1, P=0.03, respectively, and 0.3±0.1 vs. 0.1±0.1, P=0.04, respectively). Quality of vision test for uncorrected patients showed that patients with tilted disc suffered more from distortion, multiple image formation, and focus difficulty (frequency, severity, and bothersome were all affected) and starbursts (frequency only was affected). With spectacle correction, multiple images and focus difficulty (severity and bothersome) were improved. In addition, starbursts frequency was improved.
Conclusion A significant difference in certain aspects of quality and quantity of vision between astigmatic patients with and without tilted disc was shown in this study. This should be put into consideration in certain job applicants and in refractive surgery candidates.
Keywords: astigmatism, higher order aberration, quality of vision, quantity of vision, tilted disc
|How to cite this article:|
Samy El Gendy NM. Assessment of quality and quantity of vision in astigmatic patients with tilted disc: a comparative study. Delta J Ophthalmol 2018;19:191-5
|How to cite this URL:|
Samy El Gendy NM. Assessment of quality and quantity of vision in astigmatic patients with tilted disc: a comparative study. Delta J Ophthalmol [serial online] 2018 [cited 2018 Oct 17];19:191-5. Available from: http://www.djo.eg.net/text.asp?2018/19/3/191/242149
| Introduction|| |
Tilted disc is one of the causes of astigmatism detected at a relatively younger age . Little is known about the quality and quantity of vision in cases with tilted disc. As the quality and quantity of vision vary from one astigmatic patient to another, tilted disc may explain why some patients have better quality and quantity of vision and still have the same astigmatic value.
Several studies have pointed to the relationship between tilted disc and corneal astigmatism ,. Most cases with tilted disc have corneal astigmatism, yet not all cases with corneal astigmatism have tilted disc . Does this have any effect on the quality or quantity of vision? It is still not known. It has been noticed in our practice that some patients can tolerate undercorrected astigmatic spectacles, whereas others could not. This is not essentially related to the degree of astigmatism.
Tilted disc cases were shown by previous studies to have larger pupils and shifted visual axis ,. This could result into different quality and quantity of vision in cases with tilted disc. Moreover, tilted disc patients may have oblique posterior pole, and this may affect vision in a way or another . This may have implications on compromising refractive surgery results or the need of customized ablation in such cases. Better understanding of vision in cases with tilted disc may also be beneficial in ruling out tilted disc in cases where glaucoma or chiasmal diseases are confusing in differential diagnosis. Moreover, this may have implications in driving licensing, job applications, medico-legal claims, and other job-related issues. A special design of contact lenses may be recommended for cases of tilted disc based on such study.
Quantity of vision carries the advantage of being objective and can be measured by uncorrected and corrected distance visual acuities (UCDVA and CDVA). Quality of vision (QoV) can be measured either objectively using higher order aberrations (HOAs) by aberrometers or subjectively by subjective qualitative scoring using QoV questionnaire. This is a new tool developed by McAlinden et al. . This was proven to be suitable for the evaluation of eye diseases with qualitative visual problems .
This study was conducted to figure out whether cases with tilted disc have different quality and quantity of vision.
| Patients and methods|| |
The study and data collection conformed to all local laws and were compliant with the principles of the Declaration of Helsinki. The study was approved by the Local Ethical Committee. Patient informed consent was signed by all participants. Equal numbers of cases were enrolled in each group: group A included cases with tilted disc, whereas group B included cases with equivalent range of myopia and astigmatism, but without tilted disc. Tilted disc was diagnosed by fundus examination (slit lamp biomicroscopy using +90 D lens, and indirect ophthalmoscopy). Only one eye from each patient was included in the statistical analysis.
Inclusion criteria included cases with astigmatism between 1 and 3 D and myopic refraction between 1 and 6 D. The study included patients between 20 and 30 years of age.
Exclusion criteria included cases with any other ocular diseases such as glaucoma, cataract, retinal degeneration, or myopic maculopathy. Amblyopic eyes were also excluded (defined as differences of two or more lines of CDVA between the two eyes). In addition, patients who wear contact lenses and illiterate patients were excluded.
Baseline data and examination included age, sex, spherical refraction, astigmatic refraction, and spherical equivalent.
Quantity of vision assessment included CDVA, UCDVA and HOAs. CDVA and UCDVA were measured on the Test Chart 2000 (Thomson Software Solutions, Herts, UK) under photopic conditions. Visual acuity was converted from Snellen’s notation to Log MAR for statistical purposes . The HOAs were measured with an aberrometer (OPD-Scan II ARK-10000; Nidek, Japan) across a 5-mm pupil diameter.
QoV assessment was done using the QoV questionnaire, an instrument developed by McAlinden et al. . The instrument includes 30 questions that have been proven to be reliable in measuring QoV in cases with refractive problems and eye diseases. The instrument measures 10 parameters. Each parameter has along with it three subparameters (frequency, severity, and bothersome). Each subparameter was asked as a question, which was answered by the patient, and has a score ranging from 0 to 3. Zero score indicates never or not at all, whereas a score of 3 indicates very often or severe. Scores for each question were summed into a composite score; higher composite scores indicate poorer QoV. The parameters measured by the instrument are as follows: glare, haloes, starbursts, hazy vision, blurred vision, distortion, double or multiple images, fluctuation in vision, focusing difficulties, and difficulties judging distance or depth perception. The first seven of these parameters were paired with an image chosen by the authors of QoV instrument to improve response consistency and understanding.
Data management and analysis were performed using statistical package for the social sciences (version 16; SPSS Inc., Chicago, Illinois, USA). Numerical data were summarized using means and SDs or median and ranges. Categorical data were summarized as percentages. Comparison between the two groups with respect to numeric variables was done by the Student’s t test. The χ2 test was used to compare between the groups with respect to categorical data. Nonparametric values were calculated using Wilcoxon’s signed-ranks test. All P-values were two-sided. P-values less than 0.05 were considered significant.
| Results|| |
This study included 60 eyes of 60 patients, with 30 in each group. There were 16 males in group A and 14 males in group B. [Table 1] shows the quantitative vision results and [Table 2] and [Table 3] show the qualitative vision results.
Twenty-two (73.3%) cases with tilted disc had oval disc, of which 14 cases had oblique orientation of the longest axis. Five cases had the axis of disc obliquity not corresponding to the final astigmatic axis. Those cases had the worst scores in all 30 aspects of the QoV test. There was no statistically significant difference between the two groups regarding the age (24.9±2.5 vs. 25.7±2.7 years, P=0.2). Duration of wearing glasses (years) was also comparable (3.5±1.4 years in group A vs. 3.9±1.7 years in group B, P=0.3).
Spherical refraction was not statistically different between the two groups (−3.5±1.2 D in group A vs. −4±1.3 D in group B, P=0.1). Astigmatic refraction was −2.4±0.7 D in group A versus −2.1±0.7 D in group B (P=0.2). Spherical equivalent was −2.4±1.3 D in group A versus −3±1.4 D in group B (P=0.06).
There was a difference in qualitative and quantitative vision of tilted disc patients compared with patients without tilted disc with comparable age, sex, and refraction. The uncorrected vision was significantly lower in tilted disc group (P=0.04). Coma and trefoil values were also significantly higher (P=0.03 and 0.04, respectively). Regarding QoV test results, uncorrected patients with tilted disc suffered more from distortion, multiple images, and focus difficulty (frequency, severity, and bothersome) and starbursts frequency only. With spectacle correction, multiple images and focus difficulty severity and bothersome improved. In addition, starbursts frequency improved ([Table 2] and [Table 3]). Both groups were comparable regarding lower order aberrations in the form of sphere correction and astigmatism ([Table 1]). This was associated with comparable best-corrected distance visual acuity (P=0.1); however, UCDVA was significantly lower in tilted disc group (P=0.04).
| Discussion|| |
Visual outcome and satisfaction after correction of refractive errors vary greatly in patients with astigmatism. Some patients can tolerate astigmatic noncorrection whereas others suffer a lot from any slight undercorrection. Tilted disc is rather a common condition that is assumed to be nonpathological ,,; however, little is known about the specific quality and quantity of vision in those patients with altered anatomy. We hypothesized a difference in vision quality and quantity in cases with corneal astigmatism and tilted disc compared with normal patients. This can affect the results of correction either optically or by refractive surgery.
The results of the present study showed a difference in qualitative and quantitative vision of tilted disc patients compared with patients without tilted disc with comparable age, sex, and refraction. The uncorrected vision was significantly lower in tilted disc group. Coma and trefoil values were also significantly higher. Regarding QoV test results, uncorrected patients with tilted disc suffered more from distortion, multiple images and focus difficulty (frequency, severity, and bothersome) and starbursts frequency only. With spectacle correction, multiple images and focus difficulty severity and bothersome improved. Moreover, starbursts frequency improved.
Both groups were comparable regarding lower order aberrations in the form of sphere correction and astigmatism. This was associated with comparable best-corrected distance visual acuity; however, UCDVA was significantly lower in tilted disc group. This would explain why some patients are so sensitive to slight maladjustment of their glasses, whereas others are so forgiving. This may be owing to the difference in HOAs, weaker ability of the eye to adapt by accommodation, difference in pupil size, or different orientation and incidence of visual axis. This may have an implementation on ability to work without glasses.
The pupil size was shown to be larger in tilted disc cases by Ozsoy et al. . This may explain the results of the current study. On the contrary, this may have an effect on photopic and scotopic vision of tilted disc patients. In this study, all cases were evaluated in photopic conditions.
Kosekahya et al.  showed a supero-temporal shift of the visual axis in cases of tilted disc. Their study showed a correlation between the shift on the Y axis on one side and vertical coma and vertical trefoil values on the other side. These results coincided with our results. They also showed correlation between the Y axis shift and the mean cylindrical refractive error and root mean square .
One of the limitations of the current study was the fact that QoV test was rather subjective and the examiner was not masked to patient data. However, HOA results coincided with QoV questionnaire results. This may rule out such bias. Coma is usually associated with double vision.
Color vision has been shown to be affected in some cases of tilted disc . Color vision evaluation was not included in the present study. We suggest evaluating quality and quantity of vision in color affected patients.
Gündüz et al.  showed that it is not only the corneal astigmatism that occurs in tilted disc patients but also lenticular astigmatism was significantly higher in tilted disc patients compared with the control group. This may have implementation on lens extraction surgeries and contact lens fitting. Another limiting factor in the present study is that we did not divide tilted disc cases according to either lenticular or corneal astigmatism. We recommend conduction of a study comparing quality and quantity of vision between tilted disc patients with corneal versus corneal/lenticular astigmatism.Fluctuation in vision could be related to hormonal changes that occur during ovulation cycle in female patients. In the present study, comparable percentages of females were included in each group.
Tilted disc could be congenital or noncongenital . Congenital type is characterized by stationary course during childhood, whereas the acquired type shows changes with puberty . Our patients’ age ranged between 20 and 30 years. We did not differentiate between the two types during our study, as we did not look in old medical records to rule out progression. A study comparing the quality and quantity of vision between the two subtypes is recommended. Another limiting point of our study is that we did not address near vision.
In conclusion, astigmatic eyes with tilted disc differ from those without tilted disc regarding UCDVA and QoV. During enrollment to different jobs, this should be put into consideration. In addition, it should be kept in mind when addressing patients’ complaints and when selecting candidates for refractive surgery. Further research is needed to elaborate whether children with tilted discs and astigmatism are more in need of glasses than others or not.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]