Amblyopia Flashcards

Question

What is Strabismic amblyopia?

Answer 1

Results from suppression of the deviating eye. Constant strabismus leads to more severe amblyopia than intermittent strabismus. It is important to note that the size of the deviation is not related to the development of amblyopia, nor is the size of the deviation related to the severity of amblyopia, and even a very small-angle, constant, unilateral strabismus can cause strabismic amblyopia.

Answer 2

Amblyopia can be caused by form deprivation. Least common type but is typically the most severe form of amblyopia and develops when the visual axis is obstructed such as from ptosis, cornea opacities, cataracts, vitreous haemorrhage among others. Deprivation amblyopia is caused by a physical obstruction along the line of sight, which prevents a well focused, high contrast image on the retina.

Answer 3

Also known as occlusion amblyopia Result of penalisation of the sound eye with patching or atropine during amblyopia treatment of the original amblyopic eye. Affects visual acuity but also binocularity, contrast sensitivity, grating acuity and central vs. eccentric fixation.

Answer 4

Reverse Amblyopia

Answer 5

When there’s no known cause for the amblyopia (idiopathic)

Answer 6

Untapped potential so under the umbrella of amblyopia even though it’s not a true amblyopia Most common in the teenage population of bilateral amblyopia. Called functional visual loss or Streff syndrome, visual conversion reaction and hysterical amblyopia. Often have multiple symptoms and reduced academic achievement. Linked to visual or emotional stress and the prognosis is usually good. Visual acuity measures are variable, kinetic visual fields may spiral and an accommodative/vergence disorder is often present. They may concentrate hard and read very slowly. It’s often emotional/ psychogenic.

Answer 7

In the strict sense of the definition of organic amblyopia, no lesion can be detectable and the amblyopia is irreversible. However, this term is used for conditions in which the reason for reduced visual acuity has been identified such as: Achromatopsia - congenital cone deficiency. Albinism - lack of pigment, translucent cornea, abnormal decussation of nerve fibres and associated with nystagmus Macular degeneration. Nystagmus. Also the term may be used where the reduction in vision is reversible. i.e: Tobacco amblyopia. Other toxins. Causes of truly organic amblyopia have been suggested but disputed: Transient retinal haemorrhages at birth - follow up of series showed no detriment to visual acuity. Malorientation of retinal receptors - unconfirmed.

Answer 8

A characteristic sign of amblyopia is that it responds to treatment but if it doesn't it requires further investigation. If not responding to treatment this will be organic amblyopia or a pathology that isn't amblyopia. However, Meridional can be slow to show improvements and need to ensure that their meridian is correct in their glasses. If there’s no improvement within 9 months this is where worry should occur. Find in anisometropia this can improve quickly with glasses alone and then can be pushed further with atropine/patching but no improvement we need to investigate the reason for this; need to ensure they’re following the correct treatment plan (that the kids and parents are saying the same thing also).

Answer 9

Toxic - VA loss due to absorption of toxic agents such as ethambutol, cyanide, ibuprofen. Usually reversible (arsenic poisoning not reversible) Tobacco amblyopia – Toxins of tobacco constrict retinal blood vessels. Optic nerve very sensitive to tobacco – can cause optic neuritis (swelling of optic nerve). Nutritional amblyopia - Caused by deficit of vitamin B12. Often seen in alcoholics & with extreme diets. Complete recovery is possible with improved diet – but if deprivation is too prolonged VA damage permanent. Alcohol amblyopia – Painless bilateral loss of vision. Toxic effects of alcohol cause optic neuropathy. Alcohol depletes the body of nutrients – often associated with B1 deficiency

Answer 10

- Case History - Fundus and media check - Refraction - Visual acuity Crowded if possible Interpret grating acuity with care May include pinhole - Contrast sensitivity Strabismic & anisometropic amblyopias may have mkd losses of CS especially at higher spatial frequencies - Cover test – fixation pattern - 10Δ prism test - Uniocular fixation - Neutral density filter test Eyes with strabismic amblyopia may VA with neutral density filters less than fellow eye/other amblyopias An initial examination should include VA, fixation, refractive error, sensory and motor fusion, stereoacuity, accommodation, ocular motility and a thorough ocular health evaluation. Amblyopic patients often perform poorly on crowded VA charts compared to their single-letter/line scores. On follow-up examination you must avoid obtaining an artificially high or low VA measurement. VA should be done before and after cycloplegia.

Answer 11

Anisometropic amblyopia, with or without strabismus, occurs more often in left eyes than right eyes 59% left amblyopes among 2635 participants. Strabismic amblyopia 50% left eye, 50% right eye

Answer 12

To achieve and maintain maximum visual acuity

Answer 13

1. Remove any cause for stimulus deprivaton and correct refractive error. Allow period of time (up to 18 weeks) for refractive adaptation 2. Choose and agree a regimen of occlusion / atropine penalisation therapy 3. Discontinue occlusion / penalisation therapy when maximum acuity is achieved and observe for stabilisation of acuity 4. Go back to (2) if VA is not maintained

Answer 14

Critical / sensitive periods – what is the patient’s age? Correction of refractive error The refractive adaptation period (to see if glasses improve it alone or if further treatment is needed) Further treatment

Answer 15

Reduction or prevention of visual stimulation by the embarrassment of vision. This may be full time or part time.

Answer 16

Total light occlusion: Form and light is prevented from entering the eye. e.g. Elastoplast, Opticlude, Coverlet, Extension patch Eze-patch Total form occlusion: Excludes form but not light. e.g. Blenderm, transpore on glasses. Partial form occlusion. e.g. Clear fablon, sellotape, soap, Bangerter or lens (optical penalisation). (Ensure visual acuity of the good eye is reduced to below that of the amblyopic eye). Optical penalisation Usually +3.00DS or larger lens in front of non-amblyopic eye

Answer 17

Atropine penalisation of non-amblyopic eye. Two drops of cyclopentolate 1% are used in children >1yo and 0.5% in children >12yo for cycloplegic retinoscopy and refraction. If there are concerns regarding the retina then mydriatic drops should be used which give both cycloplegia and mydriasis. Must consider both refractive error before and after cycloplegia, the amount of anisometropia after cycloplegia and should consider the patient’s ocular alignment.

Answer 18

Ointment is absorbed more slowly than drops and so has a lower risk of side effects. Common side effects are: - Allergy - Dry mouth - Flushing - Glare due to dilated pupil

Answer 19

Historically it was thought that atropine penalisation was only suitable for moderate and mild amblyopia (i.e. visual acuity (VA) of 6/30 Snellens (Sns) (0.7 LogMAR) or better as per PEDIG (Pediatric Eye Disease Investigator Group) definitions. This is because atropine was thought to give insufficient blur to the better eye (i.e. not worse than 6/30 Sns / 0.7 LogMAR) to cause the amblyopic eye to dominate the visual input to the visual cortices. Thanks to some thorough and long-term research by PEDIG we now know that this is not the case. In their 2010 study PEDIG showed that VA in the amblyopic eye in children aged 3-12 years with severe amblyopia (VA 6/37.5 – 6/120Sns / 0.8 – 1.3 LogMAR) could be significantly improved by atropine therapy and this was by instilling atropine on weekends only.

Answer 20

- Gently pull down the lower lid - Drop one drop into the area between eyeball and inner part of lower lid - Allow the child to close their eyes! - Apply gentle pressure to the upper and lower lids near on the nasal side to facilitate punctal occlusion and minimised any systemic effects - Wipe away any excess ointment which has oozed out from between the lids - Do not allow child to rub eye and put fingers in mouth or eat the ointment! - Wash hands - Keep the drops locked away from reach of the child - Ensure patient is familiar with correct disposal guidelines – medicines should not be placed in the bin but instead returned to clinic or the nearest pharmacy - Give written instructions if these are available in the clinic to underline the information you have given – a bottle of atropine eye drops if ingested is potentially fatal. Fatalities have been reported Loewen and Barry (2000) - Parents should be told that the pupil will dilate; the child may find bright lights troublesome (e.g bright sunlight) and the normally straight eye will be seen to turn and fellow eye will be used instead.

Answer 21

Yes! Optical Penalisation can be used in conjunction with atropine to reduce visual acuity in the better eye more, or to encourage use of one eye for near and one eye for distance.

Answer 22

The effect dilates the pupil (up to 10-14 days) and paralyses accommodation (up to 2-3 days), thus reducing visual acuity for near and a little for distance as some latent hypermetropia becomes manifest

Answer 23

1) Select patient for treatment. 2) Remove any cause for stimulus deprivation and correct refractive error. Allow time for refractive adaptation (VA may improve up to 18 weeks following refractive correction, Stewart et al, 2004) 3) Choose an appropriate form of occlusion therapy. 4) Discontinue occlusion when maximum acuity is achieved and observe for stabilisation of visual acuity. 5) Wean the occlusion down i.e. from 2 hours daily, to 1 hour daily, to half an hour daily, as this has been shown to produce more stability of the improved VA (Holmes et al, 2007). 5) Where visual acuity is not maintained go back to (2).

Answer 24

Latent Nystagmus: As this becomes manifest as light is prevented from entering one eye, atropine may be better for this group. An alternative is partial occlusion may be given. Latent or Intermittent Squints: Where decompensation may occur, atropine or reduced occlusion regimens may be preferable. In most patients, atropine and patching are equal first line treatments (see PEDIG literature below) and it should be patients and parent/carer choice which treatment is chosen The younger the child the more careful you need to be about both atropine and occlusion because reversal amblyopia becomes more of a risk

Answer 25

Dichoptic video game presents different stimuli to either eye, with greater stimulation to the amblyopic eye. Gao et al. (2018) - Found no differences in VA between the placebo and dichoptic video game Knox et al. (2012) - smaller improvements of 1 line LogMAR after playing such games for 1 week one hour daily in eight amblyopic children. Birch et al. (2015) - that a dichoptic ipad game in pre-schoolers played four times a week for four weeks, produced a one-line improvement in amblyopic eyes, whereas the sham ipad game did not

Answer 26

CAM visual stimulator - physiologically based treatment with stimulation of the amblyopic eye by grating rotating in the background whilst drawing. Limited advantage however.

Answer 27

Yes. When severe amblyopia that would pose risks at home or in instances of poor compliance. Where difficulty carrying out occlusion is this issue patient’s were previously, rarely admitted to a children’s ward and occlusion supervised by a paediatric nurse - rarer now, but possible after congenital cataract where VA drastically different between the eyes.

Answer 28

When FTTO (full time total occlusion) visits should be 1-2 weeks

Answer 29

Where the patient is a baby or older child, where decompensation of a deviation may occur or where atropine is being used.

Answer 30

Less frequently; 3 - 8 weeks

Answer 31

May be suggested where occlusion is part time or partial and there is no danger of intractable diplopia, decompensation of a latent deviation or occlusion amblyopia.

Answer 32

Wearing a patch reduces the field of vision as well as making the child cope with possibly markedly reduced visual acuity. Care should be advised on stairs, riding bikes, crossing roads, falling over toys etc. Some activities such as riding bikes, roller skating may be banned! for safety reasons if visual acuity is very poor.

Answer 33

If atropine occlusion is given, warning about side effects should be given. In cases where patients are allergic to the drug they will become hot, flushed, dry mouthed, and may vomit. If the drug is ingested hallucinations can occur and if enough ingested it can be fatal.

Answer 34

- When visual acuity is equal on a crowded test. - When free alternation occurs - When no further improvement can be gained. - If occlusion has been part time or partial, full time total may be tried. If atropine has been twice weekly, daily atropine may be tried before giving up (provided patient is suitable). - Discontinue patching if there is a reduction in density of suppression or patient reports having diplopia as there is danger of developing intractable diplopia.

Answer 35

Evidence has been presented (that where occlusion has been worn for long periods per day (6 or more hours) the risk of recurrence is reduced by reducing occlusion to 2hrs a day prior to stopping (PEDIG, 2004). The risk of recurrence is higher where there has been greater improvement (Holmes et al., 2007). One of the biggest challenges is the chance of recurrence after completion of treatment. A study of moderate and severe amblyopia treatment found approximately 25% of patients under age seven had a recurrence of amblyopia within the first year of stopping treatment, and children ages seven to 12 had a 7% chance of recurrence (worsening of two lines of visual acuity). This recurrence is more common in patients with severe amblyopia who went from six hours of patching per day to no patching

Answer 36

- Patch Allergy - Eye Infection - Pathological causes of reduced vision - Failure of previous treatment - Physically or mentally disabled child - Emotionally upset by occlusion! - Social problems e.g. learning to lip read - Latent nystagmus - Decompensating deviation - Terminal diagnosis - Emotionally upset by occlusion

Answer 37

- Patients over 8 with manifest deviations - Possibility of Decompensation. - Nystagmus – but why not try atropine?! - Very young patients – at higher risk of reverse amblyopia – half an hour daily in under one- year olds unless uniocular dense cataract removed

Answer 38

- Any heart condition (including Down Syndrome who have systemic heart disorders) - Anyone light sensitive - Any history of convulsions - Known atropine allergy - Bupthalmos - Microcornea - Low level of vision (>0.8DS) - Family not on board (ingestion can be fatal) - Using parafoveal fixation - there's evidence to support patching to return to the fovea but this hasn't been done with atropine - Age - if at the end of suppression zone we don't want them to develop irretractable diplopia - How much school work they have as patching with low vision can impede them - History of acute angle closure glaucoma (extremely rare in children without buphthalmos or microcornea) - Less than 12 months old – neonates are at greater risk of toxicity from atropine, even reduced dose and at much higher risk of reverse amblyopia - Under four year olds should be given atropine with care as increased risk of reversal amblyopia (Hainline te al, 2009)`

Answer 39

Residual amblyopia is another treatment challenge, considering vision does not improve sufficiently with one treatment for some patients. If the patient is currently patching for two hours, increasing patching to six hours per day may help improve visual acuity and treat residual amblyopia. Another option is to switch from patching to atropine or vice-versa to see if acuity improves.

Answer 40

Risk factors for failure to restore vision include age at which treatment for the condition started (later treatment tends to have a worse outcome), deprivation amblyopia, and poor initial visual acuity.

Answer 41

- Overly aggressive amblyopia therapy (especially in younger patients) can produce reverse amblyopia of the sound eye. - A new strabismus or a decompensation of an existing strabismus can also occur. - Patches can be irritating to the skin, and the skin underlying the patch can become hypopigmented relative to the rest of the facial skin. - There is also potential social stigma associated with wearing the patch to school in some cases.

Answer 42

- Atropine use can cause side effects related to the use of this medication: flushing, rapid heart rate, mood changes (uncommon) and photophobia (common) would be examples of side effects occurring with the use of this medication. - Reverse amblyopia can also occur with Atropine use as can cause decompensation of existing strabismus or development of a new strabismus. Cases of reverse amblyopia (when the good eye is 3 logMAR units worse than VA of the amblyopic eye after treatment) are infrequent and usually mild. Most cases resolve with discontinuation of treatment.

Answer 43

E.g babies sleep a lot so 6 hours might be their whole waking hours - Mild Ambly – patching 2hrs or atropine - Mod Ambly – patching 2 hrs or atropine - Severe Ambly – patching 6 hours or atropine - Very severe ambly. – Not atropine. Dependent on age for patching 6 hours, but if say 0-6mo then do fewer hours, start with 1 hour and see them more frequently due to few waking hours, 6 – 12mo = 2hrs, 1 – 2yo = 3hrs = younger they are the more cautious we want to be. Can see them more regularly and then increase if needed. Do VA tests only if need be.

Answer 44

- 6 hours daily occlusion produces same effect as full time occlusion (patients were 3-7 years with SEVERE amblyopia (visual acuity between 6/30 and 6/120), & same effect in all levels of amblyopia in older children (7-12 years) (2008) - 2 hours daily patching produced a VA improvement similar to that of 6 hours in moderate amblyopia (visual acuity better than 6/30) - 2 hours daily patching combined with one hour of near visual activities improves moderate to severe amblyopia in children 3 to 7 years old more than glasses alone Weekend atropine produced similar levels of improvement to daily atropine for moderate amblyopes (6/12 – 6-24) (2004) - Weekend atropine can improve VA in the amblyopic eye in children aged 3-12 years with severe amblyopia (VA 6/37.5 – 6/120) (2010) - Atropine 1% is as effective as occlusion for VA’s of 6/12 – 6/30 Sns (2006)

Answer 45

Rarely so but used most in stimulus deprivation amblyopia & dense amblyopia

Answer 46

Where difficulty carrying out occlusion is this issue patient’s were previously, rarely admitted to a children’s ward and occlusion supervised by a paediatric nurse - rarer now, but possible after congenital cataract where VA drastically different between the eyes

Answer 47

- Successful treatment outcome achieved in 63-83% of patients - Success affected by VA at first visit & type of amblyopia - Very cost effective treatment - 44 times more cost effective than cataract surgery - 85 times more cost effective than macular hole treatment in the elderly (cost of treatment / number of lines VA improvement)

Answer 48

- When VA is equal on a true linear test - When free alternation occurs - When no further improvement can be gained - Reduction in density of suppression with danger of intractable diplopia

Answer 49

- Direct Occlusion - Indirect (Inverse) Occlusion - Red Filter Treatment - Pleoptics e.g. Bangerter's Method, Cupper's Method & Haidinger's Brushes - Surgery

Answer 50

Where the child is young improvement with full time total to light occlusion is hoped for. Direct occlusion is usually tried as the initial treatment.

Answer 51

Where no response is gained from direct occlusion and where the eccentric fixation is fixed, the amblyopic eye is occluded until the eccentric fixation is disrupted and fixation becomes wandering. Direct occlusion can then be used alone or in combination with another form of treatment e.g. red filter drawing. In order to avoid re-establishment of the eccentric point, if direct occlusion is only tolerated part time, indirect occlusion is continued for all other waking hours.

Answer 52

A red filter (Kodak Wratten 92) placed over the amblyopic eye encourages the foveal area to be used (because red is supposed to just stimulate cones). This will improve fixation and direct occlusion is then used to further the improvement in visual acuity. Treatments are recommended for 10 to 30 minutes daily and combined with inverse occlusion.

Answer 53

This method was previously frequently used but now is carried out in only a few centres for adults with loss of vision in their good eye, and seldom on children. Treatments have to be daily. The principle is to stimulate the foveal area. Bangerter's Method: Retina is dazzled with fovea protected thus eliminating eccentric point and fovea then stimulated. Cupper's method: An after image is produced around the fovea and the patient then asked to fixate an object so that it is covered by the after image. The fovea is thus re-educated. Haidinger’s brushes – ensures foveal fixation

Answer 54

Surgery: to place the eye in a more central position has been advocated or to overcorrect the deviation to disrupt the eccentric point.

Answer 55

Ganglion cells in the central area of the eye responding to well focused stable images and only pick up stimuli within a small area (small receptive fields). Parvocellular cells respond best to them.

Answer 56

In Amblyopia they have poorer spatial resolution and ability to detect contrast (like at high spatial frequencies)

Answer 57

Ganglion cells which respond to defocused and moving objects. They have a large receptive field. Magnocellular cells respond best to them.

Answer 58

Although some small changes have been reported in these cells in amblyopia, they are much less than the differences reported in the 'X' cells.

Answer 59

In amblyopia changes in the parvocellular layers (3, 5, 6) relating to the affected eye are found such that these cells have a lower resolving power and a loss of contrast sensitivity function at higher spatial frequencies. Histological changes accompany these neurophysiological effects, and the cells appear shrunken

Answer 60

About 80% of cells in the visual cortex normally respond to input from either eye at separate times, however, where monocular input has been reduced, this falls to only 7% in the amblyopic eye. If the reduced input is bilateral the percentage of cells responding to stimulus from either eye is 41%.

Answer 61

During this time, the visual system is susceptible to known amblyopiogenic factors: form deprivation, optical defocus, and misalignment of the eyes. If left untreated, the two amblyopiogenic mechanisms, form deprivation and abnormal binocular inhibition, cause a progressive reduction of visual acuity until approximately 6-8 years of age, at which time visual acuity stabilizes. - Light deprivation of the entire retina. - Form vision deprivation of the fovea. - Abnormal supraretinal interaction between dissimilar contours presented to corresponding retinal areas. (Abnormal binocular interaction).

Answer 62

Strabismic Strabismic deviations are initially treated with refractive correction but may require penalisation therapy such as occlusion or atropine in the better seeing eye (non-amblyopic/fixing eye). Patching for two hours per day is recommended for patients with moderate amblyopia (0.6 or better visual acuity), while patching for six hours is recommended for patients with severe amblyopia (0.7 or worse visual acuity). Our patient falls into the severe range.

Answer 63

* Do they have a skin condition or injury/open wounds around their face * Are they old enough to withstand atropine drops? * Do they have a dense strabismic amblyopia and under 4yo who are hypermetropic? This would place them at higher risk of reverse amblyopia when on atropine * Is their suppression dense enough to withstand the patching and not cause diplopia when the patch is removed? Want to check we’re not disrupting their suppression during treatment by testing at each visit. * Patching can affect BSV so test for BSV at each session and do not start occlusion if they have BSV * Length of time wearing the patch * Follow up – dense amblyopia = first visit 2-3wks and then 4wks-6wks after this * Test to see BSV if they suppression, have ARC or diplopia (most likely to have suppression because ARC unlikely due to size, diplopia should be reported in the CT so likely suppression). We would want to know the density and area of the suppression scotoma.

Answer 64

Monitoring density of suppression during treatment. Monitoring treatment being undertaken. Monitoring side effects of patching or atropine. Monitoring QoL or impact of treatment on child. * Regular meetings with the orthoptist on a 4-6 weekly basis ensure that reverse amblyopia isn’t occurring or decompensation of an existing strabismus by measuring at each appointment * To educate the patient and their parents/guardians to ensure they understand the risks associated with the treatment (i.e. keeping atropine away from children, when to stop treatment and the side effects) and the importance of adhering to the treatment * Ensuring that the correct treatment is chosen based on the child’s risks

Answer 65

It can be useful to know due to the amount of time that the eyes were dissociated before being tested and whether cooperation/concentration may be a factor in the results. May have started crowding due to the age being ready for it so important to understand the order of these or why they began

Answer 66

Anisometropic (caused by having a distinct refractive error in one eye, in this case the right eye). & Strabismic - However, it could also be strabismic. This patient has a small to moderate strabismus (ET) with right suppression during convergence testing and in Bagolini glasses there was right suppression even with glasses suggesting that there is a Constant ET with accommodative element as on PCT with glasses their angle of deviation reduces slightly

Answer 67

For anisometropia this would be anything of 1.0-1.5DS difference in hypertropia, 2D in anisoastigmatism and 3-4D in ansiomyopia

Answer 68

Studies have shown that some patients with anisometropic amblyopia may show improvement in visual acuity while wearing their glasses full-time, without concurrent patching. A retrospective study by Steele et al. showed that one third of the patients with pure anisometropic amblyopia resolved without the need of occlusion therapy. The length of recovery time was directly proportional to the severity of amblyopia. The mean time to resolution was 5.8 months[9]. In 2006 a prospective study by PEDIG reported that 27% of children with anisometropic amblyopia aged 3 to 6 resolved with spectacles alone. Visual acuity continued to improve in 48% of patients beyond 5 weeks[10].

Answer 69

Meridional Amblyopia

Answer 70

Astigmatism results from having a cornea that is not perfectly spherical. An empty box means there is no astigmatism and your eyes are perfectly spherical. A low number, like 0.25, means your eyes are not quite round and a higher number, like 3.00, means your eyes are quite oval Resolution of eye is reduced in selective meridians as a result of uncorrected astigmatism * Cylinder >1.5D is considered amblyogenic The x90 or x180 refers to against the rule (steepest meridian is horizontal) and with the rule (steepest meridian is vertical)

Answer 71

High degree of hypermetropia that is not fully corrected with glasses = Ametropia /Isoametropic/Bilateral Amblyopia

Answer 72

Glasses full-time Visual therapy/ocular exercises In symmetric bilateral cases, treatment consists of addressing the etiology of the diminished vision. Good potential for improvement compared to later correction of refractive error. Needs FT wear of correct glasses. Refraction will be monitored over time and glasses updated as necessary. Frequent visits to monitor VA. Could have fundus and media check repeated if concerned VA not improving. Could also discuss further investigation – EDT’s.

Answer 73

Treatment for anisometropia can involve corrective lenses or surgery. Corrective lenses are only good for those with a difference between their eyes of 4D or less. Children under 12 and those with severe anisometropia are generally advised to use contacts, while others can often use glasses for correction. Patching etc. The preferred method of treatment for patients with anisometropia is corrective surgery, which can sometimes permanently solve most or all of the problem. Typical surgical therapies include: Refractive corneal surgery. Used to improve the cornea’s refraction of light, this surgery can correct unilateral myopia, hypermetropia, and astigmatism. Removal of the crystalline lens. The crystalline lens is your eye’s natural lens. For some people, removing the lens can actually improve their overall vision. The sight in that eye can then be adjusted with special glasses or further surgeries. Intraocular lens implantation. Intraocular lens implantation (IOL) is a relatively common surgery for those with a cataract or astigmatism in their eye that is seriously impacting their life. While there are several variations of this surgery, the eye is generally cut precisely so a doctor can break up the natural lens. Then, a plastic lens is put in its place to correct vision. Phakic IOL. This intraocular lens implantation is similar to the above surgery, but it does not remove the crystalline lens. Instead, the intraocular lens is placed in the eye with the natural lens. The two will then work together to improve vision.