Preoperative Visual Acuity of Cataract Patients in a Tertiary Care Teaching Hospital in Eastern India
1Nikita Jaiswal, 1Ramesh Chandra Mohapatra*, 2Jatindra Nath Mohanty
1Department Ophthalmology, IMS and Sum Hospital, SOA Deemed to be University, Bhubaneswar, India.
2Medical Research Laboratory, IMS and Sum Hospital, SOA Deemed to be University, Bhubaneswar, India.
Corresponding author
Ramesh Chandra Mohapatra, Professor and Head, Department Ophthalmology, IMS and Sum Hospital, SOA Deemed to be University, Bhubaneswar, India.
Abstract
Cataract has been identified as the leading cause of blindness globally. Humans are blessed with the sense of sight by means of a pair of eyes which captures the image in the retina, which is carried to the brain by means of axons and neurons where it is processed. A retrospective study of patients with age-related cataracts who had cataract surgery performed between July 2015 to June 2017 at Department of ophthalmology , IMS and SUM hospital . Systematic random sampling and probability proportionate to size were used to recruit a representative sample. Information on sociodemographic characteristics, preoperative visual acuity, ocular and systemic comorbidities were retrieved and analysed. The axial length of the 100 patients , mean axial length is 22.71±0.83 mm. The percentage of visual acuity obtained post operatively along with PCVA. The mean preoperative visual acuity of patients in this facility did not change over the 10-year study period. Mean value of preoperative visual acuity remained within the range of blindness and did not improve over the decade.
This could either be a reflection of visual impairment at which our patients seek care or an indication of the range of visual acuities at which surgeons are willing to offer cataract surgery in our environment
Key words:Preoperative, visual acuity, cataract patients, PCVA Introduction
Sight being the most important sense of the human being. Vision helps the humans in protecting, defending and carrying day to day life activities. Humans are blessed with the sense of sight by means of a pair of eyes which captures the image in the retina, which is carried to the brain by means of axons and neurons where it is processed. The eyes are also accountable for the high human intellectuals.1
In order to that the images could be clearly formed in the retina ,the ocular media should be reasonably transparent. The two medias , the cornea and the lens besides being transparent , contribute to the dioptric power of 43D2 and 17D2 respectively. As the human body ages these structures undergo molecular and cellular changes which impairs transmission of light resulting in diminution of vision.Cornea being a six layered structure undergoes alteration in its endothelial cell counts resulting into polymegathism5 whereas lens which is a crystalline structure undergoes opacification which hampers the transmission of light. One such
condition of lens opacification due to age or any abuse to its tissue metabolism by and large is known as ―cataract‖ .Cataract : (from Latin cataracta ‗waterfall, floodgate‘)6
This condition is mostly age related and was understood by the physicians ages ago. In the era of 5th century7 in Indian history ―Susruta‖8 was the first physician who operated on the humans eyes to dislodge opacified lens. Ever since then various methods were practised in the various parts of the world to cure this condition .This method of couching9 was practised for a long period of time after which intra capsular cataract extraction was practised & visual rehabilitation was done by a highly hypermetropic spectacles.
The optical outcome was not so satisfactory to the patients as the image formed was magnified & irregular with glasses causing various optical abberations. In present era cataract is considered as a refractive surgery for better visual outcome.With evolving medical science the quest for better visual rehabilitation resulted into the evolution of artificial lens.
Sir Harold Ridley in 194910 was the first to implant IOL after removal of cataractous human lenses. In early days an arbitrary power of approximately 20-22 D nearing to the power of the human crystalline lens were used frequently .Various crude methods of prediction &
combination was adopted to reach to a near exact power of IOL to be implanted.
With the advent of biometry near exact evaluation of IOL power was made possible.
Calculation by biometry includes keratometry , axial length estimation & formula to set a proper IOL for implantation. With this concept of IOL implantation, progresses were made to achieve the exact power of the lens to be implanted. Various researchers proved the co- relation of axial length11, topography of cornea for the accuracy of power of IOL. With time, biometry of eye came into existence along with derivation of formulaes12 which helped physicians to achieve good vision postoperatively. Currently due to presence of advanced medical facilities physicians and surgeons are thriving to deliver the BCVA to their patients.
The present study is observational study done to record the precision which can be achieved by basic machines in India with the standard protocols used.
Material and methods
Study location: Institute of medical sciences and SUM hospital BhubaneshwarinOdisha.
Sampling frame: All the diagnosed case of cataract coming to OPD of Department of ophthalmology , IMS and SUM hospital .
Study period : This study was carried out between July 2015 to June 2017
Study group : The study group consisted of 100 consecutive patients suffering from cataract.
INCLUSION CRITERIA:
Patients who are operated for cataract surgery and have come for one month follow up.
Patients with no ocular pathology.
EXCLUSION CRITERIA:
Associated corneal pathology
Post operated eyes with posterior segment disease.
The selected patients of cataract with no ocular pathology are subjected to following procedures after obtaining consent from the patient and their relatives.
Signs and symptoms of the patient was recorded.
Thorough examination using torch light was done.
Visual acuity was recorded using Snellen's chart for distant and for near vision along with best corrected visual acuity.
Color vision was recorded using Ishihara test.
Contrast sensitivity was recorded using Pelli-Robson chart.
Lacrimal syringing in all suspected cases.
This was followed by examination under Slit Lamp microscopy for more detailed examination.
Dry eye evaluation using Schirmers strip was carried out.
Gonioscopy was performed wherever necessary.
IOP was recorded using Applanation Tonometer and non-contact tonometer.
Direct and Indirect Ophthalmoscopy was done to rule out any retinal or macular pathology.
Keratometry was performed using Bausch and Lomb Keratometer.
A scan was done using contact method.
IOL power was calculated using SRKII formula.
All cases were followed up post operatively.
They were reviewed at 1st week and after 1 month following operation.
All patients were subjected to distant and near vision recording along with anterior segment evaluation using slit lamp.
Results and observation
TABLE- AGE DISTRIBUTION OF PATIENTS.
AGE GROUP(in Years) NO PERCENTAGE (%)
40-50 13 13%
51-60 47 47%
61-70 25 25%
>70 15 15%
TOTAL 100 100%
Mean Age(in Years)
Mean ± S.D 60.51 ± 8.91
Table showing the age distribution of patients 47% in the age group of 51-60 years . SEX DISTRIBUTION OF PATIENTS.
SEX NO PERCENTAGE (%)
MALE 64 64%
FEMALE 36 36%
TOTAL 100 100%
Table showing the distribution of sex breakdown among the patients taken for cataract surgery. Maximum number belonged to male sex (64%)
Maximum number of eye operated are the right eye.
EYE DISTRIBUTION OF PATIENTS.
Graph showing the percentage of eye involved.
PRE OP VISION (BCVA) RANGE OF PATIENTS.
VISION/PH NO PERCENTAGE (%)
20/36 17 17%
20/40 49 49%
20/63 1 1%
20/80 3 3%
20/125 11 11%
20/200 19 19%
TOTAL 100 100%
Table showing the percentage of pre op visual acuity.
k-value.
0%
10%
20%
30%
40%
50%
60%
70%
LEFT EYE RIGHT EYE
37%
63%
percentage(%)
EYE OPERATED
Graph showing the k value . AXIAL LENGTH.
AXIAL LENGTH NO PERCENTAGE (%)
20.00-21.00 4 4%
21.01-22.00 16 16%
22.01-23.00 41 41%
23.01-24.00 35 35%
24.01-25.00 4 4%
TOTAL 100 100%
Mean Axial Length 22.71 ± 0.83
Table showing the axial length of the 100 patients , mean axial length is 22.71±0.83 mm.
IOL (D)
IOL(D) NO PERCENTAGE (%)
19.00-20.50 11 11%
21.00-22.50 53 53%
23.00-24.50 31 31%
25.00-25.50 5 5%
TOTAL 100 100%
0 5 10 15 20 25 30 35 40 45 50
39.0-41.0 41.1-43.0 43.1-45.0 45.1-47.0 19
48
29
4
k-value
Table showing the percentage of the range of IOL power implanted.
VISUAL ACUITY (POST OPERATIVE)
VISUAL ACUITY NO PERCENTAGE (%)
20/20 18 18%
20/32 65 65%
20/40 16 16%
20/63 1 1%
TOTAL 100 100%
Table showing the percentage of visual acuity obtained post operatively.
VISUAL ACUITY/ AXIAL LENGTH.
VISUAL ACUITY AXIAL LENGTH (<22.00 mm)
AXIAL LENGTH (22.00-24.00 mm)
AXIAL LENGTH (>24.00 mm)
20/20 3 13 2
20/32 9 55 2
20/40 4 11 --
20/63 -- 1 --
TOTAL 16 80 4
Table showing N.o of patients with BCVA different range axial length RESIDUAL POST OP SPHERICAL POWER
SPHERICAL POWER
NO PERCENTAGE (%)
0.00-0.50 96 96%
0.75-1.25 2 2%
1.50-2.00 1 1%
2.25-2.75 1 1%
TOTAL 100 100%
Table showing distribution of residual spherical equivalent in the sample size.
GRAPH- SPHERICAL POWER
Discussion
Cataract being the most common age related cause of diminution of vision which can be treated by visual rehabilitation by placing posterior chamber intraocular lens in exchange of the old cataractous lens which can result into emmetropic results if the pre-operative test are conducted in proper ways.
Our study has been done taking all these into considerations which includes 100 eye of 100 different patients which was operated for cataract surgery in our hospital taking their age, sex, pre-op vision, axial length and biometry into considerations.
AGE: In this study we have undertaken patients of age group between 40-74 years of age, to find the most common age group effected are between 51yrs-60 yrs which is 47% and the mean age is 60.51±8.91years.A study conducted by CHO AND RESEARCHERS found the mean age was 41.7±5.45 years in patients between 30 to 49 years of age. According to BEAVER DAM STUDY the prevalence of cataract was found to be more in the age group of 65 to 74 years of age.In the Auckland cataract study the mean age group was 74.9 ± 9.8.7 Sex : In our study which is conducted in 100 patients found it to be prevalent more in male i.e 64.0% than females i.e 36.0%. A study conducted by Tsai et al in taiwan conducted in 806 patients found the prevalence more in females(64%) than males (56%). Cho and reseachers found the gender breakdown of the patient population included 79.0% male and 21.0%
female.13-16klein and fellows studied for nuclear sclerosis, more severe levels occurred more commonly in older age groups and in women. Cortical opacities increased with increasing age and were more common in women.
KERATOMETRY READING:
In our study conducted in 100 eyes 48% of patients came into the 41.0-43.0 D range. In a study conducted by RILEY ET AL found the mean keratometric reading to be 44.1 ± 1.7 D.
Asimilar study conducted on 7500 patients for biometrical evaluation by KENNETH AND HOFFER they found the mean k value reading to be mean average keratometric value of
96%
2% 1%
1%
SPHERICAL POWER
0.00-0.50 0.75-1.25 1.50-2.00 2.25-2.75
AXIAL LENGTH :
Okasala and varonen found the correlation between the axial length and the refractive status of the eye performed on the aphakic eyes, same findings were confirmed by Jansson . In our study we found that the mean axial length in the preoperative evaluation of patients were 22.71 ± 0.83 mm. In a study conducted by Riley et al pre operatively on the patients of cataract surgery found that the axial length was a mean of 23.14 ± 1.03 mm. In a biometric analysis of 7500 patients done by Kenneth and Hoffer the mean axial length of 23.65 mm .In a comparative study done by Kronbaueret al18the mean axial length was found to be 23.19 mm (SD 1.32) with the immersion technique and 22.93 mm (SD 1.32) with the contact technique. A study done by lim and researchers found mean axial length of 23.38 ± 0.51 mm.
IOL POWER:
In this study we found that the IOL power which is implanted in the eyes of 100 patients is in the range of 21-22.50 D which is 53 % of the total IOL used in a similar study of 100 patients conducted by Limdi and sheth they found that the average IOL power 20.91 D is close to the standard power of PC IOL ie. 21.0 D.
VISUAL ACUITY :
The post- operative visual acuity in our study sample is 65% in 20 /32. In a study conducted by Eleftheriadis which conducted study on 100 patients in which he found the that 93%
achieved unaided visual acuity of 20/32 or better.In a study conducted by Cho and researchers found that 92.7% of patients showed a best-corrected visual acuity of more than 20 / 40.
VISUAL ACUITY AND AXIAL LENGTH: In our study we find that 80% of the total patients taken in the sample size has the best corrected visual acuity comes under the axial length of 22.0-24.0 mm.
SPHERICAL POWER : This study we conducted using the SRK II formula showed that 96
% of the operated patients have the spherical power in the range of 0.00-0.50 D. Dang and colleagues conducted study in 400 eyes to find that 80% of the eyes had less than 1 dioptre error & only one eye (0.3%) had an error of more than 3 D.19 Lim and researchers did a study on 267 patients to find the predictability of SRK II formulae they found that the mean error was +0.25 ± 0.67 (range −1.58 to +1.80)D, with the standard error of mean 0.669. 45 %of the patients were within 0.5 D of the predicted refractive error and 83 %were within 1.0 D.A study conducted by Jeffrey .S. Hillman at St. James hospital the calculated group had postoperative refractions which were closer to emmetropia, and the difference was of statistical significance, with 92% within the 1 D range and 98% within the ±2 D range from emmetropia.
Conclusion
The pattern in MPVAs in this office has stayed at levels of visual deficiency with no huge change throughout the decade. This might be an impression of the edge of visual acuities at which patients look for care or at which specialists are happy to offer waterfall medical procedure in our current circumstance. This pattern has suggestion on waterfall visual
impedance because of waterfall just as a low waterfall medical procedure rate.Furthermore, subjective examinations ought to be directed to assess the limit of visual acuities at which specialists in our current circumstance are happy to offer waterfall medical procedure just as visual acuities at which individuals look for wellbeing mediations for waterfalls
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