Original Article
Role
of Full Correction of Myopia in Regulation of Intra Ocular Pressure in Young
Persons
Munawar Ahmed, Murtaza Sameen, Mahtab Alam Khanzada, Arshad Ali
Lodhi, Azfar Ahmed Mirza
Pak J Ophthalmol 2017, Vol. 33 No. 1
. . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
|
See end of article for authors affiliations
..
.. Correspondence to: Munawar Ahmed Assistant professor, Department of Ophthalmology, Liaquat University of Medical & Health Sciences Jamshoro Email: munawar_404@yahoo.com |
Purpose: To evaluate effects of full myopic
correction on intra ocular pressure (IOP) in young persons. Study Design: Prospective observational clinical
study. Place and duration of
study: Department of Ophthalmology (LUMHS)
from May 2014 to May 2016 Material and Methods: Using
independent simple random sample selection technique 65 patients (15 - 35
years) of either sex having simple spherical myopia -1.0 to -4.0 D, and IOP
14 to 20 mm Hg, wearing glasses for the first time were enrolled for the study.
After verbal / written consent initial refraction was done with auto-refractometer
followed by subjective correction. IOP was measured with applanation
tonometer. Best corrected visual acuity and back vertex distance was noted.
Fully corrected prescription using duochrome test was given for full time
wear. After one week, the refraction was reconfirmed with glasses, and IOP
was measured immediately after removing the glasses. Follow up was done after
one month and three months. Each time IOP was measured immediately after removing
the glasses. Results: Out of 65 registered patients
52 completed three months follow up criteria of this study. Among these 52
patients reduction of IOP was observed in 45 (86.54%), and mean reduction of
IOP was 2.8790 mm Hg (16.7062%). In remaining 7 (13.46%) patients there was
no or little response. Only 10 (19.23%) patients complained of eye strain,
which was relieved after few days. After three months follow up data was
processed on SPSS version 14.0 and p-value was 0.003 (< 0.05), which is
quite significant. Conclusion: Myopia should not be under
corrected in young persons, as full correction is more effective in restoring
accommodation and reducing IOP than under correction. Key words: Myopia, refraction, IOP, full
correction, Young patients. |
Normal circulation of aqueous humor plays important role in
regulation of intra ocular pressure1. Intra ocular pressure is
increased when accommodation is abolished either by cycloplegics, or by myopia,
even when the anterior chamber angle is fully open. The longitudinal fibers of
cilliary muscle, which are attached to scleral spur are also relaxed and no
longer produce any affect on trabecular meshwork and result in increase in
intra ocular pressure. IOP is decreased when pilocarpine is used in open angle
glaucoma by inducing accommodation. When normal accommodation is reduced or
totally lost in myopia and restored by full refractive correction, it results
in reduction of intra ocular pressure especially in young persons2.
During normal accommodation the resistance to aqueous out flow is reduced, anterior
chamber becomes shallow and pushes the aqueous through the trabecular meshwork
and reverse happens in dis-accommodation; resistance to outflow is increased,
anterior chamber deepens and aqueous from posterior chamber is sucked into
anterior chamber3. Therefore repeated accommodation plays important
role in regulation of IOP. If myopic persons are left uncorrected for longer
time, it can result in cilliary muscle atrophy, exo-deviation, headache and
giddiness along with increased intra ocular pressure. Under correction of
myopia also produces greater degree of progression of myopia4,
actually under correction of myopia is myopigenic5. Similar
mechanism operate in primary open angle glaucoma which usually occurs after the
age of forty years when presbyopia starts due to decreased cilliary body
function, an aging process which cannot be reversed.
In emmetropic persons, Yellow green light
is focused on the retina, which is natural phenomenon of colour preference for
focusing the images on the retina, but myopics are under corrected (reading
better in red on duochrome test) which can lead to so many problems. Several clinical studies have also established relation between
intra ocular pressure and myopia6. Long standing uncorrected or under-corrected myopia will not tolerate
full correction immediately after wearing spectacles due to disuse weakness of
cilliary muscle. In time accurate refraction and constant wear of
glasses can manage all these problems.
Along with visual impairment, refractive
errors are also a significant cause of morbidity besides having social and
economic impact. Ammetropia results from an imbalance between the refractive
power and the axial length of the eyeball.7
The multi-factorial nature of myopia and
glaucoma poses a major challenge in understanding their mechanisms of
pathology. Myopia is the most common human ocular disorder worldwide and is
caused by abnormal growth of the eye resulting in refractive error.8
Myopia also increases risk for other vision impairing diseases including
glaucoma9.
As prevalence of simple myopia is highest in Asia and
commonly affects young and working age group. To prevent complications and to
provide comfortable working ability, we have conducted this study which
involves simple procedure of accurate refraction and will prevent so many
persons from ill effects of myopia and loss of accommodation.
MATERIAL AND METHODS
By
independent simple random sample selection technique total 65 patients from 15
to 35 years old of either sex having spherical myopia -1.0 to -4.0 D, and
intraocular pressure 14 to 20 mm Hg, and wearing glasses for the first time
were enrolled for study. Inclusion criteria were no sign of presbyopia, clear
media, normal anterior chamber depth and Pakistani citizens by birth. After
taking consent, patients were informed about duration and procedure of
research. Initial refraction was done with auto-refractometer and then
confirmed with retinoscopy and refined manually with cross cylinder for
astigmatic correction and duochrome test for spherical correction to achieve
equally readable in red and green at 6 meter for full correction of myopia. Inter
pupillary distance, back vertex distance, and visual acuity were noted. Slit lamp examination of anterior and
posterior segment was done. Intra-ocular pressure was measured with applanation
tonometer. Full correction of myopia (equally readable in red and green on duochrome
test at 6 meter) was prescribed and constant wear was advised. After one week,
refractive correction was reconfirmed with glasses, and intra ocular pressure
was measured immediately after removing the glasses. Further follow up was done
after one month and three months, each time intra ocular pressure was measured
immediately after removing the glasses, complaint if any was noted and results
were compiled. Patients with incomplete follow up were not included in the data
analysis.
RESULTS
Out of sixty-five patients, fifty two
completed three months follow up. The demographic data of patients is given in
table no: 1. Majority of our patients were females 40 (76.93%) and remaining 12
(23.07%) were males. Among these 52 patients reduction of IOP was observed in
45 (86.54%) patients, in remaining 7 (13.46%) patients there was no or little
response. Initial
Table 1: Demographic data N 52.
Males 12
(23.07%)
Females 40
(76.93%)
Average
age in years 22.45
(SD 1.3327)
Range of
myopia -1.0
to -4.0 D
Mean myopia - 2.37 D
Standard deviation 1.07101
IOP of these patients was more
than 18 mm Hg and their ages were more than 30 years. Only 10 (10.23%) patients
complained of eye strain which was relieved after few days of wearing
spectacles.
Mean intra ocular pressure before myopic correction
was 17.2331 mm Hg with a standard deviation of 1.34931; mean intraocular pressure after full myopic correction was
14.3541 mm Hg with a standard deviation of 1.15210. Mean reduction of IOP was
2.8790 mm Hg (16.7062%) which is more or less equal to pilocarpine when used in
open angle glaucoma. The results were therefore significant and p-value was 0.003
(< 0.05) when processed on SPSS versions 14.0. The summary of results is
given in table 2.
Table 2: Summary of result after
full myopic correction at 3 months follow up N = 52.
Females 40 76.93%
Males 12 23.07%
Mean IOP 14.3541 83.2937%
Mean reduction of IOP 2.8790 16.7062%
Standard deviation 1.15210
P-value 0.003
DISCUSSION
Aqueous humor dynamics depends on cilliary
muscle and trabecular meshwork function which in turn are related with the
refractive state of eye and play important role in regulation of intra ocular
pressure. The prevalence of myopic refractive error is highest in the Asian
population. An association between open angle glaucoma and myopia is well
established, this relation is reported for children10,11, in young
adults12 and presbyopic adults13. The relation between
intra ocular pressure and myopia varies with age and ethnicity. We have done
this study on younger age group between 15 to 35 years who were born in
Pakistan and majority of these patients were females. Whether patient is
myopic, presbyopic or dilated with potent cycloplegic, the ultimate effect is
loss of cilliary muscle function and decrease in aqueous outflow due to
decreased pull of longitudinal fibers of cilliary muscle, which are attached to
scleral spur. Patients who do not show reduction in their intraocular pressure
after full correction of myopia, they may have trabecular
meshwork abnormality or ciliary muscle weakness.
Edwards and Brown reported that in children
who were not myopic at age of 7 years but became myopic at the age of 9 years
also showed increase in IOP and there was no change in IOP in non-myopic
children over the same age and time period14,15.
It is also observed that moderate myopes show
greater increase in intra ocular pressure and higher peak values (19.8 mm Hg)
as compared to emmetropes and low myopes (18.6 and 18.7 mmHg). This may be due
to abnormal auto-regulation of ocular blood pressure in myopes of moderate and
greater severity and can result in ocular hypertension or glaucoma16. Similar finding are observed in our study, patients who had
myopia more than -2.0 D their intra ocular pressure was also more as compared
to the patients having myopia less than -2.0 D.
Similar effects can be produced with
cycloplegics which produce complete loss of accommodation and result in
elevation of IOP in certain eyes in absence of angle closure. This type of
response occurs in 23% with open angle glaucoma and 2% in normal individuals. Any patient who has normal anterior chamber
angle and shows elevation of IOP after routine dilatation with potent
cycloplegics should considered an open angle glaucoma suspect.17.
It
means normal accommodation plays important role in regulation of intra ocular
pressure. This normal physiology is altered in myopia but can be returned to
normal by accurate refraction in young persons. Full correction of myopia will
keep the cilliary body muscle healthy and will delay the onset of presbyopia.
Further more constant wear of accurate glasses can
reduce IOP and in turn can limit the progression of myopia in young persons,
prevents exophoria / exotropia, relieves head ache, and can delay onset of open
angle glaucoma, because cillary muscle remains active. Under-correction of myopia not only ineffective in regulating the
intra ocular pressure but also ineffective in controlling the progression of
axial myopia18. Some studies have mentioned transient rise of IOP
during early phase of accommodation but this occurs usually in animal models19.
Two affects are produced with the myopia, defocusing of retina and decrease in
accommodation20, both these function are restored with full
correction of myopia especially in young persons. The procedure of refraction
is already being done since long time but no one has evaluated its effects on
the physiology of eye. This is first time that we have noted these facts and
prevented the young people from many complications of myopia by simple
procedure that is full correction of myopia.
CONCLUSION
Accurate and full myopic correction plays
important role in regulation of intra ocular pressure and aqueous humour
dynamics. It can limit the progression of myopia, delay the onset of presbyopia
and open angle glaucoma. It can prevent development of exophoria, exotropia, and
related eye strains and headache. Therefore myopia should
not be under corrected in young persons, as full correction is more effective
in reducing IOP than under correction.
Authors
Affiliation
Dr. Munawar Ahmed
Assistant professor, Department of Ophthalmology, Liaquat
University of Medical and Health Sciences Jamshoro.
Dr. Murtaza Sameen
Liaquat University of Medical and Health Sciences Jamshoro.
Dr. Mahtab Alam Khanzada
Liaquat University of Medical and Health Sciences Jamshoro.
Dr. Arshad Ali Lodhi
Liaquat University of Medical and Health Sciences Jamshoro.
Dr. Azfar Ahmed Mirza
Liaquat University of Medical and Health Sciences Jamshoro
Role of
Authors
Dr. Munawar Ahmed
Conducted the main research, examination of patients on each
follow up visit, collection of data, and discussion with co-authors, compiled
the results and written main script of the article.
Dr. Murtaza Sameen
Arranged spectacles for poor patients and helped in literature
research.
Dr. Mahtab Alam Khanzada
Data collection and helped in main script writing.
Dr. Arshad Ali Lodhi,
Referred the patients who fulfilled the selection criteria to main
author.
Dr. Azfar Ahmed Mirza
Counseling of the patients, and guided the patients about the
research procedure.
REFERENCES
1.
Manik Goel, Renata G Picciani, Richard K Lee,
Sanjoy K Bhattacharia. Aqueous humor dynamics: a review Open Ophthalmol J.
2010; 4: 52-59.
2.
Yan Liu, Huibin Ly Xiaodan Jiang, Xiaodan Hu, Mingzhou Zhang,
Xuemin Li. Intraocular Pressure Changes during Accommodation in Progressing Myopes,
Stable Myopes and Emmetropes PLOS One, 2015; 10 (10): e0141839.
3.
Kaufman PL, Ba΄ra ΄ny EH. Loss of acute pilocarpine effect on outflow facility following surgical
disinsertion and retrodisplacement of the ciliary muscle from the scleral spur.
In the cynomolgus monkey. Invest Ophthalmol. 1976; 15: 793807.
4.
Christina A. Esposito; Cody Peterson; Cory Coronado; Balamurali
Vasudevan; Cenneth Ciuffreda. Under-correction
of myopia increases myopic progression A retrospective study. Investigative
Ophthalmology and visual science, 2012; 53: 4446. Doe:
5.
Balamurali Vasudevana, Christina Espositoa, Cody Petersona, Cory Coronadoa, Kenneth J. Ciuffredab.
Under-correction of human myopia Is it myopigenic?: A retrospective analysis
of clinical refraction data. J Optom. 2014; 7 (3): 147-52.
6.
A J Lee, S-M Saw, G Gazzard, A Cheng, and D T
H Tan. Intraocular pressure
associations with refractive error and axial length in children Br J
Ophthalmol. 2004; 88 (1): 57.
7.
Muhammad Zia-ul-Haque Ansari, Abrar Ali,
Adnan Afaq, Tabassum Ahmed, Khawaja Sharif-ul-Hassan. Relative distribution of refractive errors an
audit of retinoscopic findings Pak J Ophthalmol, 2007; 23 (3): 144-150.
8.
Bloom RI, Friedman IB, Chuck RS. Increasing rates of myopia: the long view.
Curr Opin Ophthalmol. 2010; 21: 247248.
9.
Loyo-Berrios NI, Blustein JN. Primary-open glaucoma and myopia: a narrative review. WMJ,
2007; 106 (95): 8589.
10. Quinn GE, Berlin JA, Young TL, Ziylan S, Stone RA. Association of intraocular pressure and myopia
in children. Ophthalmology, 1995; 102: 1805.
11. Abdalla MI, Hamdi M. Applanation ocular tension in myopia and
emmetropia.Br J Ophthalmol. 1970; 54: 1225.
12. Edwards MH, Brown B. Intraocular pressure in a selected sample of
myopic and non myopic Chinese children. Optom Vis Sci. 1993; 70: 157.
13. Nomura H, Ando F, Niino N, Shimokata H, Miyake Y. The relationship between intraocular
pressure and refractive error adjusting for age and central corneal thickness.
Ophthalmic Physiol Opt, 2004; 24: 41-5.
14. Edwards MH, Brown B. IOP in myopic children: the relationship
between increase in IOP and the development of myopia. Ophthalmic Physiol Opt.
1996; 16: 2436.
15.
Ruth E Manny, G Lynn
Mtchell, Susan A Cotter, Lisa A Jones-jordan, Robert
N Kleinstein, Donald O Mutti et al. Intraocular Pressure, Ethnicity,
and Refractive Error. Optom
Vis Sci. 2011; 88 (2): 1445-1453.
16.
Xin Xu, Li Li, Ruidan Cao, Ye Tao, Qun Guo, Jia Geng, Yongzhi Li,
Zuoming Zhang. Intraocular Pressure and Ocular Perfusion Pressure in
Myopes during 21 min Head-Down Rest ASEM, 2010; 81 (4): 418-422.
17.
Laurence S. Harris, MD. Cycloplegic-Induced
Intraocular Pressure Elevations: A Study of Normal and Open-Angle Glaucomatous
Eyes. Arch Ophthalmol. 1968; 79 (3): 242-246.
18.
Kahmeng Chung; Norhani Mohidin; Daniel J. O Leary Under-correction of myopia enhances rather than inhibits
myopia progression Vision research, 2002; 42 (22): 2555-2559.
19.
L Yan, L Hubbin, L Xuemin. Accommodation
induced Intra ocular pressure changes in progressing myopes and emmetropes Eye,
2014; 28: 1334-1340.
20.
Peter M. Allen, Daniel J. O Leary Accommodation functions: Co-dependency and relation to
refractive error Vision Research, 2006; 46 (4): 491-505.
|
|