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Does myopia tend to decrease the risk for later hyperopia?

Does myopia tend to decrease the risk for later hyperopia?


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It seems like being nearsighted for much of your life due to elongated eyes would make it easier in general to focus on near objects rather than far since the lens would not have to change much. Since in old age we lose the ability to focus close images due to a hardening of the lens over time, wouldn't having eyes shaped more for near images be helpful in maintaining the ability to see close up, and thus nearsighted, or myopic people, would be less likely to develop farsightedness, or hyperopia, with age? It seems then that nearsightedness is more of an adaptation that occurs at a young age, so that these people can work up close for longer periods of time both in the the short term(studying) and long term(age). I'd love to hear if any research has been done on this subject, and any other input you have.


It is generally understood that we tend to become hyperopic as we age (reference). As to whether this aids in decreasing myopia is stated as marginal in papers. One paper titled "Is there a hyperopic shift in myopic eyes during the presbyopic years?" states that

it was found that almost all hyperopic and emmetropic eyes showed an age-related hyperopic shift; but only a small proportion of myopic eyes shifted toward hyperopia, with others remaining relatively stable and still others increasing in myopia.

In a second study titled "Age-Related Decreases in the Prevalence of Myopia: Longitudinal Change or Cohort Effect?", it was found that there is a decline in the prevalence of myopia in older adults.

Some people in personal experiences have stated that their myopia has decreased (reference) while others found themselves wearing bifocals (reference). In closing, I would say that this is something that your Ophthalmologist may be able to predict better but it is not a given that your myopia would decrease. It may or may not be so with many factors like your eye shape coming into play.


Let me see whether I can explain this quickly. The eye size is tightly regulated genetically. Babies don't have big eyes, they have exactly the same sized eyes like adults, only their head is smaller. Myopic eyes are larger than normal and hyperopic eyes are smaller than normal, even though the difference is only 1 to a few millimeters. When you focus to the far point, the light focusses to the nearest point possible in the back of your eye. When you come closer to an object, the focus point inside the eye moves further out. Thus, the farsighted person with the small eye can only see when the object is away. Moving closer moves the focal point inside the eye to behind the retina. The opposite is true for myopic people with too large eyes. When a person gets old, the lens gets stiff and cannot adjust the focal point inside the eye to the distance of the retina. Thus, the lens remains stiff in the most relaxed state (extended), or - in other words - at the most distant focal point the person had when it was young. A normal-sighted person has his old-age focal point at the horizon and since his lens is stiff, can only see sharp from the horizon to a few meters in front of him (depending on the intensity and wavelength of the light - blue light better than red). A short-sighted person is of disadvantage when old, since his far point remains to be at short distance. He gains a little sharpness over the normal sighted person in the short distance, but loses it in the distance like he always did. You can calculate this nicely, actually. All physics.


Hyperopia

(ii) Acuity at near and distance is more often affected in older patients where presbyopic changes mean that accommodation is reduced and the hyperopic error is not as easily neutralised.

(iii) Near acuity is almost always more affected than distance acuity. -> the distance VA has a near equivalent which should be similar / the same as the distance VA in low hyperopic rx this might not be the case

(iv) Patients may be experiencing visual discomfort. This occurs particularly after prolonged use of extra accommodation for visual tasks at near but
sometimes also at distance.

(v) As patients with hyperopia habitually accommodate, they often have difficulty relaxing their accommodation when plus lenses are added (prescription of lenses for hyperopes may be more complicated than for
myopes).

(vi) High hyperopia that is not corrected at a young age can lead to unilateral or bilateral amblyopia.

(vii) Hyperopia is often associated with esophoria, esotropia, or strabismic amblyopia and these conditions can be minimised or eliminated with correction of the hyperopic refractive error + vision therapy

(viii) Hyperopia changes little throughout life.
(ix) Hyperopia is not associated with pathology as myopia can be (degenerative myopia).

(iv) At some point in time the patient notices that the lenses prescribed for near give clear vision at
distance and that they can reduce or delay the onset of asthenopic symptoms if the glasses are
worn more frequently. Eventually the patient will start to wear the lenses full time. (Remember these are in fact the distance refractive findings)

(v) There is little need for a cycloplegic refraction in patients 20 to 40 years of age, unless the dry
refractive findings are variable / do not alleviate symptoms.

(vi) Some patients with low hyperopia have no symptoms (acuity adequate at distance and near,
no asthenopic symptoms or functional problems). Hence no Rx required.
(vii) The amount of hyperopia alone does not determine whether spectacles are prescribed.
(viii) The amount of hyperopia uncovered is NOT the sole determinant of the lens power to be
prescribed for hyperopia. Partial corrections can be provided. The correction depends on
the severity of symptoms, the degree of hyperopia found, the patient's age and amplitude of
accommodation, the patient's binocular vision status (esophoria etc.), the agreement/lack of
agreement between retinoscopy and the subjective refraction.
(ix) Encourage subjective refractions to be performed under binocular conditions (a fused
image can help control accommodation.
(x) The "Pierce-Borish" technique (convergence controlled refraction) involves adding Base In
prism during a binocular refraction to assist in further relaxation of accommodation.

(xi) CYCLOPLEGIC Refractions should be performed whenever latent hyperopia is suspected.

(xii) The results of a cycloplegic refraction often have too much plus to be prescribed for distance but the cycloplegic refraction is sometimes
prescribed for near. As the patient gets used to the near correction, more hyperopia can become manifest at distance. Follow-up examinations at
regular intervals (3 to 6 months) should be used to monitor changes and the need to increase the lens power if symptoms remain. Your threshold for
using a cycloplegic should be low.

(xiii) If the patient's symptoms are severe, then as much plus as will be accepted
subjectively can be prescribed for distance and extra plus can be given for near
(as a bifocal or progressive power lens). Follow-up in 6 to 12 weeks will show
whether the patient may accept a stronger hyperopic prescription. (Follow-up is very important)


Myopia:

Components Ametropia:
1. Cornea: moderate contributer
2. Lens: small contributers
3.Anterior Chamber Depth: Small contributor
-Note the mean refractive power before the myopia epidemic.

-Based on amount of refractive component analysis (Based on dioptric source)
-Are any individual components out of the range or not?
-Other factors could change the expression of any underlying genetic predisposition
-It wasn't specific if these factors were random, environmental, use-abuse etc.

Active Progressive
-Usually no asthenopia
-Near induced transited myopia response is not associated with high visual discomfort in college students STUDY link
-usually Eso at near
-Indication for plus at near
-Difficult to reduce
-->Active progressive:
Esophoria at near, favorable response to plus lenses at near including symptoms reduction or elimination. Myopia is difficult to reduce here. Low PRA, due to decreased accommodative facility and near eso.
-->Response to plus at near, visual hygiene, VT to increase accommodative Facility

-Risk from parent RE tends to combine with other risk factors such as Diopter Hours
-->Diopter-hour risk X3 with one myopic parent
-->Diopter-hour risk X6with two

Lack of consistency in results of proposed mode of inheritance:
-->Autosomal recessive
-->Recessive, dominant, variation of of both
-->Sex-linked, variations with recessive and dominant
-->Current genomic research indicates at least 20 genetic loci may be involved
-->Bastien:Inherited genetic/temperamental predisposition

--> Myopic shift in dark focus after 25 min of monocular or binocular reading esoteric shift in dark vergence after binocular reading
-Early (EOM) vs Late onset myopes (LOM)
(Have a greater near point induced transit myopia) than LOMS, which have greater NITM than emmetropes following 5 min 4.5 diopter demand work
-Persistence of NITM correlated to EOMs

2. Bastien: Biologically appropriate, successful adaption to decrease near work stress

3. Forrest: Near work not inherently stressful
(approach and mental attitudes yield stress)

2.Psychological/Emotional Factors:
-NOt necessarily cause and effect correlation
-Consistent set of personality traits
-Prolonged central processing (decreased peripheral awareness) may be linked to
--Feeling of being walled in
--Not feeling connected to life's larger meaning
--Tendency to get mentally stuck
--Postulation: Central/Peripheral balance/utilization is critical
-Kraskin: Body posture changes moving center of gravity forward
-->Convage lenses increase tonicity in body posturing musculature

Deprivation of an image reaching the retina (occlude an eye) will cause myopia. This has been tested for example when non human species are in a dark room when they are very young they will develop myopia. These tests are done during critical neurological period of the animals lives and they can revert back to emmetropia if the inducing position is removed while still within the critical period. The induced myopic changes are generally and mostly due to axial growth. So the eye grow to resolve the blur induced by other optical components.
-The signal for this growth is regulated by the retina. These changes occur even when the foveal region is ablated with a laser

-For this theory finding definitely show that environmental factors influence myopia development

Downsides:
-Rebound effect when tx stopped
-Photophobia and blurred vision
-Cycloplegia required reading glasses
-Potential light damage to retina
-Potential elevation in IOP
-Atropine use does not elevate IOP in myopic children
-Potential system reactions
-Resurfence with 0.05% vs the typical 0.5% or 0.1%

-Effect at Retina: (Rather than the ciliary body)
-->Atropine has no effect on striated muscle
(Birds/Chicks ciliary muscle and pupil muscles are strained--not smooth--muscle nocycloplegia)
-->Atropine disrupted deprivation myopia in chicks and birds

-Atropine does not have any affect on striated muscle: Eg. Bird. Even if the affect isn't on the accommodation you still get the myopia control so it is not about the myopia control.
-Atropine disrupted deprivation myopia in chicks and birds.

-Pirenzipine: Very mild cycloplegia/meydriatic effect
-Selective muscarinic M1 Antagonist
-Considered negligible to children
-Similar effect in disrupting myopia progression
-History of Safe oral usage since 1960's and 70's: Stomach ulcers
-Formerly valleyforge pharmaceuticals
-->Sold rights for pirenzipine to Novartis
-->Trials stopped after 1 year on humans
(Low concentration effects not as impressive needed 2% which induced non-selective side effects, including partial cycloplegia and gastric problems)


Hyperopia (Farsightedness)

Hyperopia is a vision condition in which you have difficulty seeing things at near distance. Your eyes are better at focusing on things in the distance and worse at seeing things up close. Other names for hyperopia include hypermetropia and farsightedness.

Hyperopia is one type of refractive error. A refractive error occurs when your eyes do not focus images properly onto the back of your eye (retina). A refractive error causes you to see blurry. Eye doctors diagnose refractive errors during routine eye exams.

There are three general types of refractive errors (vision problems):

  • Hyperopia (farsightedness) is when your eye focuses images behind your retina. As a result, you see blurry when objects are close up, such as reading materials.
  • Myopia (nearsightedness) is when your eye focuses images in front of your retina. Distant objects are blurry for people with myopia (near vision).
  • Astigmatism is when your eye focuses images at multiple points. Some points could be in front of your retina, some behind the retina. If you have astigmatism, you see blurry at distance and near.

You can have one type or a combination of refractive errors. For example, you can have hyperopia and astigmatism in the same eye. You can also have hyperopia in one eye and myopia in the other eye.

Hyperopia should not be confused with presbyopia. Presbyopia is an age-related change in which your eyes lose the ability to focus up close, but for different reasons. Hyperopia can occur at any age, while presbyopia usually occurs over age 40.

What Causes Hyperopia?

There are a few reasons why your eyes may focus images too far behind your retina. From an anatomy standpoint, hyperopia occurs because:

  • You have a shorter eyeball length than average.
  • Your cornea, which is the clear covering over your eye, is too flat.

There is a genetic component involved with farsightedness. Studies show that hyperopia, along with other refractive errors, has a multifactorial inheritance. This means refractive errors are primarily influenced by multiple genes. But they may also arise due to external factors such as lifestyle.

Hyperopia affects approximately 10 percent of people in the United States.

Research also shows that multifactorial conditions such as hyperopia tend to run in families. If a direct family member (such as a parent or sibling) is farsighted, you are more likely to be farsighted. You may have a lower risk if the family member is more distant, such as a cousin.

Hyperopia in Children

Many children are farsighted at birth because their eyes are smaller. As they get older, their eyeballs lengthen, and they may grow out of their hyperopia. Children can even go from being hyperopic to myopic as their eyes develop.

If a child is only mildly farsighted, they may not show any symptoms of blurry vision. Younger people generally have stronger focusing ability, a process called accommodation. Children can often accommodate well enough to compensate for moderate amounts of farsightedness.

Adults lose the ability to accommodate with age because their eye muscles and lenses can't squint as well. Hyperopic patients tend to complain about blurry vision up close as they get older.

Symptoms of Farsightedness

General symptoms of farsightedness include:

  • Blurry vision
  • Headaches
  • Eye strain and aches
  • Tired eyes
  • Squinting
  • Fatigue

These problems tend to be more pronounced after doing near work, such as reading, computer work, or sewing.

With hyperopia, symptoms can vary depending on the strength of your prescription. We can break down hyperopia into different categories based on your prescription. For reference, diopters (D) are the units your eye doctor uses when measuring your eyesight. These are the same numbers you see on your eyeglass prescription.

  • Low hyperopia is +2.00 D or less.
  • Moderate hyperopia ranges between +2.25 to +5.00 D.
  • Severe hyperopia is anything above +5.25 D.

In general, people with lower amounts of hyperopia do not notice problems seeing at a distance. They may only need to wear reading glasses on occasion. With moderate or severe amounts of hyperopia, you may notice your vision is blurry at near and at far. These patients tend to need their glasses full-time.

Hyperopia tends to worsen with age, so older patients will find that they need to wear glasses more often. This is especially true when presbyopia begins after age 40.

Additionally, farsighted patients who spend large amounts of time working up close may experience more symptoms than someone who does not. For example, someone who sits at a computer all day may complain of headaches and blurry vision more often than someone who drives for a living.

Hyperopia Diagnosis

Hyperopia or farsightedness can easily be detected during a basic eye exam. A basic vision test, where you read letters on a chart should show your doctor if you have hyperopia. If you do show signs of hyperopia, they will check to see how light refracts in your eye. They may use a machine, called a retinoscope, or shine a light into your eye to do this.

After this, your doctor will use a machine called a phoropter to determine the strength of your prescription. They will then talk to you about your treatment options.

Hyperopia Treatment Options

The most common treatment for hyperopia is either glasses or contact lenses. Your eye doctor can advise you whether you should wear your corrective lenses full-time or only for certain activities.

There are some other treatment options to consider if you do not wish to wear glasses or contact lenses:

Orthokeratology (ortho-k)

Ortho-k lenses are rigid, gas permeable contact lenses you wear overnight. While you sleep, the lenses temporarily reshape your corneas. When you wake up, you remove the contacts. You will be able to see reasonably well for the day, without any glasses or contacts. Since your cornea will start returning to its normal shape after a day or so, you will typically need to use the lenses every night. Orthokeratology can only correct lower amounts of hyperopia.

Refractive Lens Exchange

Similar to cataract surgery, this procedure involves removing the natural lens in your eye. The surgeon then implants an artificial lens that corrects your hyperopia. This surgery is an excellent option for patients with high hyperopia and who may develop cataracts soon. If you have a refractive lens exchange, you will not need cataract surgery later in life.

Laser Refractive Surgery

Laser eye surgery is an excellent option for patients with hyperopia, including both PRK and LASIK. Generally, PRK and LASIK can treat up to about +5.00 D of hyperopia. If your prescription is higher, your surgeon may recommend a refractive lens exchange instead.


Materials and Methods

Ethics Statement

The use of the animals was approved by the Committee on the Ethics of Animal Experiments of the Sun Yat-sen University on June 30, 2010 (S1 File, Permit Number: 2010–019) and was in compliance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. All examinations were performed under a combination of ketamine hydrochloride/ acepromazine maleate anesthesia, and all efforts were made to minimize suffering. No monkey was sacrificed during the study.

Animals

Sixteen healthy rhesus monkeys (Macaca mulatta) (LanDao Bio, GuangDong, China. Guangdong Landau Biotechnology Co. Ltd, which is eligible to breed and sale rhesus monkeys for research purposes. S2 and S3 Files) were used in the study. All the monkeys were reared at the Ophthalmic Animal Laboratory for Zhongshan Ophthalmic Center of Sun Yet-sen University under a 12:12 light—dark cycle, with lights on at 8 AM and off at 8 PM. Each animal was housed individually in a fine steel cage, which allowed practically all of the incident light to reach the animal. The laboratory room is around 16 square meter and is equipped with temperature and humidity control system which keep the room temperatures 25°C±2°C and the relative humidity at 45%±5%. The animals were housed in cages individually with free access to food and water. The steel cages used indoors were 800mm×770mm×1140mm, while those outdoors were 400mm×400mm×500mm and were easy to move. Eight of them were obtained at age of 20–30 days and were reared until they grew into adolescence, approximately at 3 years of age. Another eight 3 year-old monkeys reared in the same laboratory were employed to provide control data on normal development in puberty.

The feeding regimens have been reported by elsewhere[13]. Specifically, the infant monkeys had been bottle-feeding infant formula five to six times per day until they were 4 months old. When the monkeys grew up and could eat solid foods independently, the diet which ensured good nutrition for all monkeys included primate feed, vegetable meal and fruit meal.

To alleviate suffering of the animals during the experimental period, monkeys were anesthesia for every examination. Anesthesia was accomplished by intramuscular injection a combination of ketamine hydrochloride + acepromazine maleate (10 mg/kg + 0.2 mg/kg) and topical application of one drop of 0.4% oxybuprocaine hydrochlorid. In addition, one to two drops of 0.3% tobramycin were used after each examination to avoid ocular infection.

Experimental Design

Experiment A.

All of the infant monkeys were fitted with lightweight helmets, provided by Dr. Earl L. Smith 3rd (College of Optometry, University of Houston, Houston, TX), at approximately 20–30 days of age, incorporating a -3.0D spectacle lens over the right eye and a zero-power lens over the left eye for hyperopic anisometropia. The lenses were worn continuously, except when removed for cleaning or eye examination, for about 190 days. The details of the maintenance of the lens have been described elsewhere[13].

After wearing the lens, the animals were randomly divided into two groups (n = 4 monkeys in each group): A) AL (artificial lighting) monkeys were kept under fluorescent lamps (YZ28RR16, 28W, color temperature = 6500K). Illuminance at the level of the monkeys’ eyes was 100-200lux, and the main output wavelengths were 453nm, 545nm and 611nm. B) NL (natural lighting) monkeys were exposed to natural outdoor light for 3 hours, from 11:00 to 14:00 each day, and were housed in the same indoor setting as the AL monkeys during the rest of the light phase. As the weather changed, the intensity of the sunlight was not stable. A photometer (1332A, TES, Taiwan, China) was used to determine the illuminance at the level of the animals’ eyes at 30-minutes intervals, every day of treatment. When it was cloudy, the light intensity varied from 6,000 to 10,000 lux but when it was sunny, the illuminance could reach 60,000 to 70,000 lux. Throughout the course of the experiment, the average highest light intensity ranged from 25,000 to 40,000lux. In addition, the spectrum of the sunlight is across most of the electromagnetic spectrum, spanning a range of 200nm to about 1mm.

Experiment B.

To examine whether the early life exposure to sunlight would associate with the onset of refractive errors, all of the helmets were removed after the last biometry measurements of experiment A, at approximately 215±3 days of age. Then, the monkeys regained unrestricted vision and were raised in the same laboratory room (without exposure to outdoor light) until they were about 3 years old (1185 ± 3 days of age). That age in monkeys can be considered to be equivalent to 12 years of age in humans, well into the age range when school myopia frequently develops in children. Comparison data were available from eight 3-years-old monkeys reared from birth with unrestricted vision, under the standard indoor lights and conditions described above.

Ocular Biometry

The spherical equivalent refractive error, corneal curvatures, and axial dimensions of each eye of each monkey were measured before lens-wearing (at 23±3 days of age), monthly during the lens-wearing treatment period, and at the age of puberty (at 1185+3 days of age). To make these measurements, the monkeys were anesthetized with a combination of ketamine hydrochloride + acepromazine maleate (10 mg/kg + 0.2 mg/kg, respectively, intramuscular). Retinoscopy was performed by two experienced optometrists using a streak retinoscope and hand-held trial lens, after topical application of three drops of 0.5% tropicamide for cycloplegia. Mean spherical equivalent spectacle-plane refractive correction was recorded for a given eye’s refractive status. Corneal curvature was assessed using a handheld videotopographer (Vista EyeSys, Houston, TX). The axial dimensions were measured by A-scan ultrasonography (AXIS-II Quantel Medical Inc., Clermont-Ferrand, France) the 11-MHz transducer was placed in direct contact with the cornea, following topical anesthesia with one drop of 0.4% oxybuprocaine hydrochloride. The details of these determinations have been reported previously[12]. All the examiners in our experiment were blinded to the animal groups and each other’s findings.

Statistical Analysis

Mann-Whitney U test were used to compare the median of refraction and vitreous chamber depth between the two groups at the start of lens-rearing treatment. Since the lens-rearing regimen altered emmetropization process in both eyes of every animal in experiment A, each individual eye was recorded and treated as an independent sample. However, considering the emmetropization in the two eyes of the animals may not be totally independent, a linear mixed model, which is a useful approach allowing correlation in observations, was used to compare the longitudinal change of refractive errors and vitreous chamber depth in the two groups. To further assess the effect of different ambient light on defocus-induced myopia, all data are presented as mean intrerocular differences, i.e. differences between treated eye and fellow eye. Independent-samples t-tests were used to compare intraocular differences between NL group and AL group at the start and the end of lens-rearing period respectively. In experiment B, a paired-samples t Test was used to assess the interocular differences. One-way ANOVAs were employed to analyze interocular inference of measured ocular parameters among the three groups, and least-significant difference tests were further applied in post hoc multiple Comparisons. Pearson’s correlation analysis was used to examine the relationship between refractive status and vitreous chamber depth. All measurements were analyzed on computer (SPSS 11.0, IBM, NY, USA).


Understanding age-related vision changes

Just like your body, your eyes and vision change over time. While not everyone will experience the same symptoms, the following are common age-related vision changes:

  • Need for more light. As you age, you need more light to see as well as you used to. Brighter lights in your work area or next to your reading chair will help make reading and other close-up tasks easier.
  • Difficulty reading and doing close work. Printed materials can become less clear, in part because the lens in your eye becomes less flexible over time. This makes it harder for your eyes to focus on near objects than when you were younger.
  • Problems with a glare. When driving, you may notice additional glare from headlights at night or sun reflecting off windshields or pavement during the day. Changes in your lenses in your eyes cause light entering the eye to be scattered rather than focused precisely on the retina. This creates more glare.
  • Changes in color perception. The normally clear lens located inside your eye may start to discolor. This makes it harder to see and distinguish between certain color shades.
  • Reduced tear production. With age, the tear glands in your eyes will produce fewer tears. This is particularly true for women experiencing hormone changes. As a result, your eyes may feel dry and irritated. Having an adequate amount of tears is essential for keeping your eyes healthy and for maintaining clear sight.

Encountering problems with near vision after 40

If you have never needed eyeglasses or contact lenses to correct distance vision, then experiencing near vision problems after age 40 can be concerning and frustrating. You may feel like you've abruptly lost the ability to read the newspaper or see the cell phone numbers.

These changes in your focusing power have been occurring gradually since childhood. Now your eyes don't have enough focusing power to see clearly for reading and other close vision tasks.

Losing this focusing ability for near vision, called presbyopia, occurs because the lens inside the eye becomes less flexible. This flexibility allows the eye to change focus from objects that are far away to objects that are close. People with presbyopia have several options to regain clear near vision. They include:

  • Eyeglasses, including reading glasses, bifocals, and progressive lenses.
  • Contact lenses, including monovision and multifocal lenses.
  • Laser surgery and other refractive surgery procedures.

As you continue to age, presbyopia becomes more advanced. You may notice that you need to change your eyeglass or contact lens prescriptions more frequently than you used to. Around age 60, these changes in near vision should stop, and prescription changes should occur less frequently.

Presbyopia can't be prevented or cured, but most people should be able to regain clear, comfortable near vision for all of their lifestyle needs.


Biology: Homeostasis

2) The pituitary gland secretes follicle stimulating hormone which stimulates the ovary to mature an egg inside a follicle.

3) The developing follicle in the ovary begins to secrete oestrogen.

4) The oestrogen tells the lining of the uterus to repair itself and get thicker, also inhibits (stops) production of follicle stimulating hormone.

5) High levels of oestrogen signal the pituitary gland to release Lutenising hormone.

6) LH makes the ovary release an egg (ovulation). It also makes the remains of the follicle develop into the yellow body.

7) The yellow body secretes Progesterone which tells the uterus lining to be maintained and thicken in readiness for a fertilised egg to implant. High progesterone levels stop the pituitary gland from releasing FSH and LH so that no more eggs are matured or released.

8) The ovum (egg) only survives for about 36 hours. If the egg is not fertilised the yellow body breaks down and production of progesterone stops.

9) Levels of both oestrogen and progesterone fall. The lining of the uterus breaks down and menstruation starts.


7 Effects of Alcohol Myopia

THE BASICS

Alcohol leads to myopia (short-sightedness). Alcohol consumption—getting drunk—narrows your focus of attention and thoughts to the most obvious information or cues in your immediate environment. As a consequence, behavior is overly influenced by the noticeable cues to the exclusion of more distant stimuli or consequences (Steele and Josephs, 1990). For example, a person already having negative thoughts is likely to feel sad after becoming intoxicated.

The following seven points illustrate the effect heavy drinking can have on your capacity to focus and make decisions.

Alcohol myopia limits the amount of information that intoxicated individuals can process. As a result, remaining attentional resources are allocated to only the most immediate environment. This diminished availability of resources has particularly strong effects in situations of conflict—when faced with two competing motivations, one is immediately obvious, and the other seems distant. This explains the attention-related mistakes that people make while intoxicated, such as impaired driving (MacDonald, Zanna, and Fong, 1995).

2. Impulsive behavior.

No is an extraordinarily complicated word when people are drunk. Alcohol, at least in high doses, may impair people’s capacity to inhibit impulsive behavior (Hofmann et al. 2008). Intoxicated individuals tend to attend to the stimuli that provide them with immediate pleasure (e.g., unsafe sex) at the expense of future risk (e.g., potentially contracting an STD or causing a pregnancy).

Alcohol by itself does not cause aggression. It only increases the level of aggression in response to provocation (Giancola, et al., 2010). In hostile situations, alcohol encourages aggressive behavior by narrowing our attention on provocative cues, rather than on non-provocative or self-restraint cues.

4. Overeating.

Heavy drinking triggers overeating, because alcohol impairs people’s ability to regulate or control their food intake. For this reason, chronic dieters who continuously monitor their calorie intake find themselves particularly at risk to experience alcohol’s negative consequences on their dietary goals. Reducing alcohol intake is a common recommendation for participants in weight-loss programs (Hofmann et al. 2008).

5. Self-awareness.

Intoxicated people tend to lose the ability to successfully monitor their behavior (Hull and Bond, 1986). As you've probably noticed, the beginning of a cocktail party is typically subdued, and guests are mostly self-conscious. But an hour or so later the volume usually increases. As the drinkers’ awareness declines, the attitude tends to change to “Who really cares?”

Alcohol is known to relieve stress and anxiety (Horwitz, 2013). This may be maintained by the popular belief that alcohol “takes the edge off.” Alcohol diverts attention away from anxiety-inducing stimuli. The pharmacological effects of ethanol (similar to benzodiazepines and opiates) can temporarily reduce anxiety. However, alcohol does not necessarily reduce anxiety and fear in the long term, and may in fact worsen it, which can motivate further drinking. Thus, anxiety and alcohol use are risk factors for each other.

THE BASICS

7. Empty promises.

The strength of people’s commitment to something depends on its value to them and the chance that the value will occur. Typically a goal’s desirability is more obvious to people than its feasibility. Alcohol ingestion breeds empty goal commitment by making people focus on the desirability rather than the feasibility of important goals. Once sober, they fail to follow through on their promises (Sevincer and Oettingen, 2009).

LinkedIn Image Credit: Syda Productions/Shutterstock

Hofmann, W., Förster, G., Stroebe, W., & Wiers, R. W. (2011). The great disinhibitor: alcohol, food cues, and eating behavior. In Handbook of Behavior, Food and Nutrition (pp. 2977-2991). Springer New York.

Giancola, P. R., Josephs, R. A., Parrott, D. J., & Duke, A. A. (2010). Alcohol myopia revisited: Clarifying aggression and other acts of disinhibition through a distorted lens. Perspectives on Psychological Science, 5, 265–278.

Horwitz, Allan (2013). Anxiety: A Short History. Baltimore: The Johns Hopkins University Press, 2013.

Hull, J.G., & Bond, C.F. (1986). Social and behavioral consequences of alcohol consumption and expectancy: A meta-analysis. Psychological Bulletin, 99, 347–360.

MacDonald, T., Zanna, M., & Fong, G. (1995). Decision making in altered states: Effects of alcohol on attitudes toward drinking and driving. Journal of Personality and Social Psychology, 68, 973–985.

Sevincer, A. T., & Oettingen, G. (2009). Alcohol breeds empty goal commitment. Journal of Abnormal Psychology, 118, 623-633.

Steele, C. M., and Josephs, R. A. (1990). Alcohol myopia: its prized and dangerous effects. American Psychology, 45, 921–933.


What is Orthokeratology?

The reason so many people think of orthokeratology as orthodontics for the eyes is that the central concept is roughly the same: both braces and ortho-k involve wearing devices to reshape parts of the body. However, while braces reshape your teeth and jaw structure, ortho-k uses special contact lenses to reshape your cornea (the surface of your eye).

The cornea is made of clear, flexible tissue that helps focus light onto the retina, allowing the eye to clearly distinguish objects at a distance. However, some people have abnormally-shaped corneas, which causes light to focus on the retina improperly. As a result, these people experience blurry vision when viewing objects at specific distances.

In the 1940s, eye doctors realized that the cornea’s flexibility allowed it to change shape temporarily. Glass lenses were originally used for this purpose, but in later years most eye doctors switched to RGP (rigid gas permeable lenses). Near the end of the 20th century, advancements in computer technology made it possible to map the surface of the eye and create custom lenses that corrected specific refractive errors in individual patients more accurately.

Modern ortho-k lenses are typically worn at night. They change the shape of your cornea as you sleep, allowing you to see clearly when you remove them the next morning. Since your cornea will gradually revert to its original shape over time, ortho-k lenses must generally be replaced each night before going to bed.

What Does Ortho-K Correct?

Ortho-k is normally used to correct 3 conditions: myopia, hyperopia, and astigmatism.

  • Myopia is commonly referred to as nearsightedness. Nearly 1.5 billion people suffer from myopia worldwide. It can occur when the cornea’s curve is too pronounced for the shape of the eyeball.
  • Hyperopia, also known as farsightedness, affects even more people around the world than myopia—approximately 30.6%. Hyperopia sometimes occurs when the curve of the cornea is too gentle for the eyeball’s shape.
  • Astigmatism is the most common of these three refractive errors, affecting an estimated 33.3% of females and 31.1% of males globally. Astigmatism often presents in people whose corneas are irregularly shaped. Most corneas have round curves, but in patients with astigmatism they may be egg-shaped instead.

The conditions listed above are not always caused by the shape of the cornea. They can also appear in people whose eyeballs (or lenses, in certain cases of astigmatism) are shaped abnormally.

Who Can Get Ortho-K?

Ortho-k is appropriate for patients of all ages. In fact, eye doctors often recommend ortho-k as an alternative for children or young adults who cannot get laser eye surgery (such as LASIK) because their eyes are still developing.

Ortho-k is often recommended as a method of slowing down childhood myopia, which can increase a child’s risk of developing more severe eye conditions later in life when left untreated.

What Does Ortho-K Cost?

Since ortho-k lenses are custom-made for the corneas of each person who wears them, they tend to be more expensive than most other contact lenses. Furthermore, ortho-k is considered an elective procedure, which means that most insurance policies won’t cover it. However, many people consider the benefits of seeing clearly all day without lenses to be worth the price.

So, what do ortho-k lenses actually cost? For most Americans, the fees generally end up being between $1000-$2000. That’s only about half of what LASIK costs—but remember, every case is different. Complex or severe refractive errors can make it harder to create effective ortho-k lenses and the price may go up as a result.


Discussion

Our results suggest that, in this age group of 6 to 10 years, sleeping late (after 9:30 p.m.) significantly increased the risk of myopia. Late bedtime was seen to be a consistent risk factor associated with higher prevalence of myopia at baseline, higher incidence of myopia over 2 years, and greater progression of refractive error over 2 years.

Although the current study sample is much larger, younger, and without high degrees of myopia, our findings do echo with a previous study published by Ayaki et al., where a group of 21 highly myopic teenagers (mean age 16.7 ± 2.4 years) were found to have a late bedtime compared to teenagers with either mild or no myopia 12 . The authors also found this group had the shortest sleep duration. In our study, sleep duration did not differ between myopes and non-myopes at baseline (9.49 vs. 9.47 h, p = 0.6) or at 24-month visit (9.16 vs. 9.18 h, p = 0.6). While our findings did not reveal any relationship between sleep duration and myopia, a number of previous studies have reported significant yet contradictory results. Some studies found sleeping less promotes myopia, whilst others found the opposite. For example, one study involving 3625 Korean teenagers (age range 12–19 years) identified an inverse relationship between sleep duration and the severity of myopia 11 . Subjects who had more than nine hours of sleep were 41% less likely to have myopia compared to those who slept less than 5 h per night, after adjusting for myopia related risk factors. Similarly, results from a study that enrolled 15,136 Chinese children (age range 6 to 18 years) indicated an increased risk for myopia (adjusted-OR = 3.37) amongst those who slept less than 7 h per night compared to those who slept more than 9 h per night 20 . In contrast, another study of 1902 Chinese children (mean age 9.80 ± 0.44 years) identified a higher risk for myopia amongst those who slept longer every night (OR = 1.02, 95% CI [1.01, 1.04]), after adjusting for age, gender, sleep disorder score, weekly near work and outdoor hours 21 . As previously iterated, our study demonstrated no evidence supporting a relationship between sleep duration and myopia, which is similar to the conclusion drawn by a Singaporean study on 376 infants, where they found no association between sleep duration at 12 months and myopia at 3 years 22 . A recent Chinese study also reported negative results for sleep duration and myopia progression, although the association became significant in girls after stratifying the sample by gender 23 . Moreover, unlike the Korean adolescent sample studied by Jee et al. or the Chinese children sample studied by Xu et al. 11,20 , children of the current sample had sufficient sleep for their age group (an average of 9.49 ± 0.54 h per night at baseline) according to consensus recommendations developed by the American Academy of Sleep Medicine, who recommends at least 9 h sleep every night for 6 to 9 years old 24 . This, perhaps, along with the relatively narrow age range of our sample (6 to 9 years compared to up to 19 years in other studies), are the reasons why sleep duration did not stand out as a significant factor here.

Our findings highlight the impact of sleeping late on myopia onset and progression, although the underlying mechanisms remain unclear. On the one hand, sleeping late could hint at more late-night myopigenic activities and more exposure to artificial lighting conditions of the child. In the evening, while staying in an indoor environment, a child is highly likely to spend more time on near-based activities, such as reading or on digital screens. The impact of excessive near work on myopia development has already been broadly studied 25,26,27 , although the ‘timing’ factor has never been discussed in those studies. This probably also contributed to the inconsistency findings on the relationship of near work and myopia 26,28,29 . The effect of artificial lighting is another frequently investigated yet still equivocal topic amongst myopia studies 30,31,32,33,34,35 . Due to inconsistent results seen in animal models and the multi-dimensional complexity of artificial lighting 34 , much more research is needed before optimal artificial lighting conditions can be identified, if at all, for myopia prevention. Additionally, children who read more and spent more time on screen and less time outdoors were found more likely to sleep late (Table 7), which echoes with previous discussion by Morgan et al. that increased education pressure is a risk factor for myopia 36 .

On the other hand, sleep-related ‘timing’ or ‘time-of-day’ variable, is in fact a circadian rhythm marker and interests have already been mounting around the relationship between circadian rhythms and myopia 16,18,37,38 . Sleep–wake cycle is perhaps the most frequently perceived example of circadian rhythms by human beings. As a consequence of involuntarily shifting between two ‘time zones’: one determined by our internal clock, the circadian rhythm, and the other governed by study, work or other social duties in modern societies, misalignment of biological and social time is almost universal 39 . Disturbance to the circadian clock can not only affect the academic performance of children 40 , but also cause several health problems 41,42,43 . In terms of the visual system, a number of animal studies have demonstrated the importance of regular rhythmicity of lighting conditions on normal ocular growth and emmetropisation 13,14,44 . For example, retinal-specific knockouts of the clock gene can induce myopia in mice 16 . In humans, circadian dysregulation has been reported for myopic subjects. Compared to non-myopes, myopes were found to have higher serum concentration of melatonin in the morning, shorter sleep duration, and poorer sleep quality 11,12,45 . Seasonal changes reported in myopia progression could also suggest an impact of seasonal variations of circadian rhythms on the development of myopia 46 . Evidence supporting a role of circadian rhythm in myopia development is further strengthened by the results from a recent meta-analysis of genome-wide association studies, where genetic factors regulating circadian rhythm are identified to also participate in the development of myopia and refractive error 15 . Finally, yet importantly, several ocular biometry parameters, such as intraocular pressure (IOP), choroidal thickness, and axial length, were found to exhibit diurnal rhythms in humans 47,48 . Nickla et al. identified in chicks a positive correlation between the phase difference in axial length and choroid thickness and ocular growth rate and proposed that such phase difference could be seen as a predictor for eye growth rate 49 . The author further suggested that myopia treatment could incorporate ‘timing’ as a factor in implementation in order to achieve the best possible outcome 37 .

Evidence for a complex relationship between circadian rhythm and myopia development is mounting, despite the fact that the underlying mechanisms are yet to be illuminated. Nevertheless, our results can confirm that sleeping late is closely associated with myopia, but additional research is needed to determine whether sleeping late makes children more prone to myopigenic activities under poor lighting conditions when they are supposed to be sleeping or more susceptible to abnormal eye growth due to circadian disturbance. These are just two of the many more questions for future myopia studies.

The strengths of the current study include the large sample size and a school-based design of the trial. The extensive support received from the local governmental and school personnel made it a logistically successful trial with good data collection. The mobile phone app-based questionnaire provided a convenient way to address the questionnaire and enabled timely data entry by the parents/carers, thus minimising data entry errors associated with transfer of data from paper-based questionnaires to digital forms. Furthermore, refractive error was determined by cycloplegic auto-refraction and therefore increasing the confidence in the refractive error data. Yet, there were a number of limitations. To begin with, data collected via questionnaires are subject to recall bias. Although a wearable device was used in this trial, it was not worn after 7 p.m. and therefore sleep-related information was not captured. Secondly, although the sample size was large, the trial sample was localised and derived from the metropolitan Shanghai with children sharing same ethnic and cultural background. This might make the findings of current study less generalisable to other populations. Finally, the age range of the current cohort was relatively narrow (6 to 9 years old at baseline). Therefore, further studies focusing on samples from other regions, wider age range and more diversity are desirable to determine if these results hold valid for the wider population.



Comments:

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