Prevalence determination of the lost of visual acuity and severe amblyopia performed for students with limited resources

Carlos Carrión Ojeda. Ophthalmologist “OPELUCE” EYE CLINIC- Lima Perú
Flor Gálvez Quiroz. Ophthalmologist INSN
Raphael Jaramillo. Ophthalmologist INSN José Morales de La Cruz MD
Merí Gazani Meza. Nurse of Ophthalmology
Susana Guerrero Ocampo. “Aid in Action” Foundation

TRANSLATION: Eugene Fedeiko

ABSTRACT

INTRODUCTION: In Peru, where there are nearly 12 million children, reporting of studies of lost of visual acuity, associated ametropia and amblyopia in students has just started.

OBJECTIVE: To determine the prevalence and epidemiologic characteristics of lost of visual acuity and severe amblyopia in the students of the South of Lima, Peru.

METHODS: There are 120,000 students in 42 schools of five districts in this area of Lima. The study was performed on 12,364 students in their schools in three stages.

The first stage consisted of cross-sectional and observational evaluations of visual sharpness and refracting examinations.

The second stage consisted of ophthalmologic examinations for determine moderate and severe lost of visual acuity, and make respective cicloplegic refraction to these students.

The third stage consisted of detecting the amblyopic students if visual sharpness did not improve with corrective lenses, associating severe lost of visual acuity and amblyopia, and evaluating the existence of initial eyeglasses treatment for them. Excel 2003 was used to calculate sample and analyses results.

RESULTS: A high prevalence (46.3%) (p <0.01) of lost of visual acuity was discovered in the general student population and a high prevalence of amblyopia in students whit severe lost of visual acuity (39%). Four of each 10 students with severe lost of visual acuity had developed amblyopia (p< 0.029) and of these, 90.25% had not used lenses (p< 0.045).

CONCLUSIONS: It is urgent to take measures to help prevent visual amblyopia in children before and until age 5 since amblyopia diminishes student academic yields. It is, indeed, highly necessary to work to prevent these diseases to improve the future of our students.

KEY WORDS: Visual acuity, Ametropia, Amblyopia, Refraction.

INTRODUCTION

In Peru there are no investigations related to the frequency or incidence of lost of visual acuity or amblyopia in students. The American Academy of Ophthalmology defines lost visual acuity as visual sharpness below 20/20 in one of the eyes in children older than five, 20/30 or less in four-year-olds, and 20/40 or less in one eye in three-year-olds. In Peru’s population of approximately 29 million, almost 11,600,000 are children. In the world population, the mean incidence of ametropia, almost always inherited, is about 30% to 35%.

Lost of visual acuity and ametropia associated is fundamentally diagnosed by means of measuring visual sharpness with standard “ directional E” Snellen cards positioned 6 meters from and at the same height of the visual axis of the patient. Severe lost of visual acuity and consequent amblyopia (sluggish eye) are general public health problems and whose prevention are great priorities in the global initiative for the elimination of avoidable visual incapacity. The World Health Organization and The American Academy of Ophthalmology define amblyopia as the incapacity to improve eye visual sharpness even after the use of correct prescription lenses. Over the whole world amblyopia is apparent in 3% to 4.5% of the population. Amblyopia limits learning capacity and impairs normal activity development, so special preventative attention is necessary including monitoring and properly controlling of visual sharpness in different stages of growth. Closely observing children in their games and book and whiteboard reading helps reveal effects of visual deterioration.

Classification of ambliopía according to lost of visual acuity.

• Deep <0,1.
• Moderate 0,5-0,1.
• Slight >0,5.

MATERIALS AND METHODS

This is a cross-sectional investigation revealing the frequency of lost visual acuity, ametropia associated and severe amblyopia in the schools of some districts in the South of Lima.
We used a snellen chart of the “E” letter to evaluate the sharpness of visual acuity and a autorefractometer “Unicos” trade mark.

• Operational definitions: Because ofthis, we define for our study the variable lost of visual acuity and severe amblyopia like.

Slight lost ofvisual acuity: Slightly impaired visual sharpness of minus 20/20 unto minus of 20/50 in one or both eyes.

Moderate lost of visual acuity: Visual sharpness from 20/50 unto minus of 20/70 in one or both eyes.

Severe lost of visual acuity: Reduced or equal visual sharpness of 20/70 in one or both eyes.

Severe amblyopia: Incapacity to improve eye visual sharpness even after the use of correct prescription lenses in students that present severe lost of visual acuity.

• Type and design of investigation: 3-stage prevalence investigation.

Stage I: study Observational and cross-sectional, whit diagnoses of individual visual sharpness and individual refraction in the school environment.

Stage II: Visual sharpness control, qualification of type of ametropia, and cicloplegic refraction.

Stage III: Detection of severe amblyopia and individualized remedial action with corrective lenses.

Population of the study:

The subject population of the study included the 120,000 students who study in the schools of the five districts in the South of Lima. The sample frame of 28,452 students corresponds to the overall total student population of the 42 schools, called Healthy Schools, which participated in this study.

Sample population for the first stage:

For an undetermined number of the population and a proportion of 50% of those diagnosed with lost acuity vision and ametropia associated - 5,6,17, Z =1.96 (α =0.05), maximum error β=0.01. The calculated student sample size was 9,604. To maintain a good degree of accuracy in the study and to step up to the great demand, 12,364 students aged 3 to 15 were enlisted in the first stage. The 42 Healthy Schools are spread over the five districts and constitute a significant sample for this study.

Sample population for the second stage: This sample was calculated on an undetermined size of the population. A proportion of 5% of amblyopia has been reported in different world studies - 9,25. Z =1.96 (α =0.05), maximum error β=0.045. The calculated student sample size was 90; however, this study revealed 105 students with severe ametropia in the first stage of this cicloplegic examination in search of amblyopia.

Sample population for the third stage: This sample was calculated in the same manner as the second sample, in this stage eyeglasses were employed. The students came up with their own eyeglasses after which the study checked each student for ambliopia. In the cases of the students thereafter whose ambliopia did not diminish, they were referred to other healthcare professionals for further treatment.

Criteria of inclusion:

Stage I: Students up to age 15 who studied in the healthy schools were identified between March and June of 2007. Students with good vision (20/20) in both eyes were excluded.

Stage II: The patients evaluated in this stage and diagnosed with moderate or severe visual acuity lost, agreed with paternal consent to be clinically treated (informed consent).

Stage III: The patients who passed through Stage II and whose vision did not improve with eyeglasses were passed into this further stage of sending on for more ophthalmologic care.

RESULTS

Examined 12,364 children aged 3 to 15, diagnosing 5,650 with ametropia:

• Slight lost of visual acuity: 3,125 students.

• Moderate lost of visual acuity: 1,710 students.

• Severe lost of visual acuity: 815 students.

The prevalence of ametropia in the population - 46.3% - of the Healthy Schools was very high compared to the 30% to 35% frequencies reported in other countries. By the characteristics of the study there were no concentrations or population dispersions. Within the total discovered ametropia, the slight type accounted for 55.31% - corrective lenses required only if subjects had visual symptoms.

The moderate type - 30.27% - almost always required refractive correction. And the severe types - 14.42%, 815 students - a number greater than that in reported statistics, required urgent treatment since this type potentially causes amblyopia.

There is no significant difference with respect to the presence lost of acuity vision between the sexes; the greater tendency (53%) of the presence of lost of acuity vision is in females.


TABLE 1

A significant association exists between type of severe lost of acuity vision and amblyopia in the combined school population. Chi - square (7.07), significance (p =0.029).

DISCUSSION

Lostvisual acuity and ametropiaassociated was discovered in 46.3% of the population without any type of concentration or dispersion, a greater percentage compared to the 30% to 35% frequencies reported in the studies performed in other countries - 5,6,17,21,25.

A greater tendency (53%) of the presence of ametropia was apparent in the female group. The greater relative percentage of the population afflicted with ametropia was within the group aged 6 to 9. The percentage of ametropia in the students varies between 30% and 75% in the different schools. Students with severe ametropia or amblyopia were referred to the Child Health Institute for specialized treatment.

When amblyopia was diagnosed within the severe lost vision acuity population in the third stage of the study, the parents of the students were questioned as to their children’s use of glasses. Only 9.75% responded that their children had used glasses and some of those admitted that their children, for whatever reason, had not used their glasses continuously; 90,25% of the parents responded that their children had never used glasses, and the parents were moreover unaware of the health problem that their children had.

Pathological and ethiological causes of ametropia associated: Is well-known that ametropia is hereditary, but some authors have revealed that other factors such as precocious underfeeding or low weight at birth may be prompters of the disease - 9,20,24. This would explain the different results obtained in our study with respect to other facts discovered in the U.S.A. and in other developed countries.

Behavior of lost of visual acuity and amblyopia: The prevalence of amblyopia within the severe cases of lost of vision acuity of the five districts pertaining in the South of Lima is 39%. Four of each ten who suffer severe lost of vision acuity are afflicted with amblyopia.

It is moreover necessary to consider ambliopes, which are caused by moderate lost of visual acuity. Moderate lost of visual acuity and associated ametropia also contributes, albeit in smaller relative proportion, to ambliopía - 7,8,10,11. Whatever increases the number of ambliopes found in this study could be similar all over Peru because the sample is significant and in general population. There is no significant difference of the presence of lost of visual acuity between the sexes.



A significant association exists between type of severe ametropia and ambliopía in the students population. Chi - square (7,07) and significance (p =0,029). Cylindrical ametropia is the greater cause of ambliopía for the purposes of this study. Some 55.55% of cylindrical amétropes translate into ambliopia compared to the 31.34% of spherical / cylindrical ametropes that translate into ambliopia. In our study spherical ametropes generally didn’t translate into amblyopia; there were only a few cases.

CONCLUSIONS

There was a high prevalence (46.30%) (p< 0,01). of lost of visual acuity in the students of the schools studied. Living in extreme poverty, these students have few resources and are undernourished. The greater relative frequency of ametropia was evident in the group aged 6 to 9 - (47.46% masculine and 53.95% feminine). That means that this group has greater probabilities of ametropia, the level of physiological visual development that is reached in this tactically important point that occurs by age 6, the time at which vision must be totally developed.

It is essential to control visual sharpness at this age, visual clarity quite simply accomplished with the Snellen “directional E” card because all healthy children have developed their spatial orientation completely at this age and are completely familiar with the alphabet. The high prevalence (39%) of amblyopia due to severe lost (14.42%) of visual acuity can be attributed mainly to the evidence that only 9.75% of those studied used lenses.

For this reason, the strategies to apply in Peru and in other poor countries with a similar population type must be different from those applied in first-world countries. It would also be advisable to pay closer attention to improving the nutrition of both the pregnant women and the suckling babies in these populations. Amblyopia is predictable and requires ever improving interinstitutional strategies between the Health and Education sectors.

Solid ocular health policies and affordable corrective products and services conscienciously steered by the State or by ONGs are required to help, with lenses and therapy, those stricken to recover. On the basis of the conclusions of our investigation, our group proposes the following recommendations:

To doctors and other healthcare personnel: Possible early detection of lost visual acuity in students and references to an ophthalmologist.

To ophthalmologists: Create public awareness (especially in the high probability populations) as to the causes of amblyopia and early diagnosing in students. Jointly work with pediatricians and other doctors and nurses.

To ocular healthcare service providers: Strive to arrive at such oriented strategies to diminish the frequency of amblyopia as the diffusion of causes of ametropia and amblyopia between doctors and ophthalmologists. Educate the general public about ametropia and amblyopia natural science courses and other educational programs. Create interinstitutional Health-Education committees to review the presence of ametropia and amblyopia in students before age 5. And, follow up with pertinent corrective measures in all cases of amblyopia or severe ametropia.

To international ocular healthcare service providers: Institute studies of prevalence and of risk factors of ametropia and amblyopia in populations with precocious underfeeding and also their correlation with student yield will improve the future quality of life of the children. The outlook of any country improves with its constant investment in child healthcare.

RECOGNITIONS

This study was awarded the National Institute of Child Health Prize for our Investigation of Child Health, Version 2008, winning first place.

ACKNOWLEDGEMENTS

To ONG “Land of Children” and “Aid in Action Foundation“ and to the INSN (Children’s Hospital of Peru) for their support.
To Promotional Schools of Health, Healthy Schools, for its support and participation.

To Nelly, Rosa, and Arie for their love, time, support, and understanding.

CONFLICT OF INTEREST

Authors have not commercial or financial interest in products described or reported in the manuscript that may give rise to the perception of a potential conflict of interest.

ETHICAL ASPECTS

The present study was carried out according to the postulated ethical contained in the Declaration of Helsinki and successive declarations that have upgraded referrals postulates.

PHOTOS