Hypermetropia/Hyperopia

a detailed informative compilation on everything related to hypermetropia or hyperopia required in ophthalmic or optometric clinical practice and education

1. Hyperopia Suraj shil B. Optom 2 nd year Ridley college of optometry, Jorhat

2. Layout Introduction 8. Visual acuity Etiology 9. Correction of Hyperopia Hereditary role 10. Prescription Classification 11. Uncorrected hyperopia Progression Symptoms Signs

3. Introduction Hyperopia (hypermetropia) is the condition in which rays of light converge to a focus behind the retina with accommodation at rest Can occur in two scenarios; either the axial length is too small for the eye’s normal refractive power or the refractive power is too low for its normal axial length Note: Short axial length more common etiology

4. Etiology Etiologically hypermetropia may be Axial Curvatural Index Positional Absence of crystalline lens(Aphakia)

5. Axial hypermetropia In this condition the total refractive power of the eye is normal but there is an axial shortening of eyeball About 1mm shortening of the anteroposterior diameter of the eye results in 3.00 D of hypermetropia

6. Example: let a patient have axial length of 22mm and 21mm in right eye and left eye respectively. Calculate refractive error in both eyes.

7. Sol n : OD= (24-22)mm = 2mm Refractive error = 2x3 = +6.00 D OS= (24-21)mm = 3mm Refractive error = 3x3 = +9.00 D

8. Curvatural hypermetropia It is the condition in which the curvature of the cornea or the lens or both are flatter than the normal, resulting in a decreased refractive power of the eye About 1mm increase in radius of curvature results in 6.00 D of hypermetropia

9. Example: If a patient has +12.00 D of refractive error in his right eye, with no abnormal changes in his crystalline lens and the anteroposterior diameter then calculate the radius of curvature of his cornea

10. Sol n : 1mm increase in radius causes +6.00 D of error, then, +12.00 D will be caused due to increase of 2mm of radius Therefore, radius= (7.5+2)mm = 9.5mm

11. Index hypermetropia It occurs due to change in refractive index of the lens in old age It may also occur in diabetics under treatment Note: The Beaver Dam Study found that diabetes was associated with a hyperopic shift over a 10-year period. Long term refractive error has been studied among diabetic patients

12. Positional hypermetropia It results from posteriorly placed crystalline lens Note: In a study done by Omar A. AlShehri and his colleagues from King Saud Bin Abdulaziz University of Health Sciences, Saudi Arabia, the abstract read as: ectopia lentis is defined as a crystalline lens diaplacement either partially or completely, anteriorly or posteriorly due to zonular abnormalities. It can be a result of trauma, hereditary ocular disease, or part of systemic diseases like Marfan syndrome and homocystinuria

13. Connective tissue disorder associated with long narrow limbs, skeletal abnormalities, ocular abnormalities Genetics : Autosomal Dominant mutation in fibrillin-1 (FBN1) gene    located on chromosome 15 multiple mutations identified

14. Absence of crystalline lens It is either congenital or acquired (following surgical removal or dislocation) It is a condition of high hyperopia A case report done by G. Trabucchi, A. Piantanida and their collegues of Department of Ophthalmology and Visual Sciences, University of Milan, Italy reported that: Corneal defects and iridocorneal adhesion were found, but aphakia was the major pathologic ocular finding. The clinical picture and pathology study indicated this case as a Peter’s anomaly presenting congenital aphakia

15. Peters’ anomaly affects the iris, corneal endothelium and Descemet’s membrane leading to Peters’ type I. Peters’ type II in addition will have lens abnormalities and tend to be bilateral Genetics : Reported chromosomal abnormalities in chromosome 20, trisomy 13 and chromosome 11 have been reported to contribute to Peters’ anomaly

16. Hereditary role The assessment of the role of heredity in the determination of the refractive state of the eye is complicated, because the refractive state is the result of a number of interrelated refractive components Francois(1961) pointed out that it is likely that several genetic factors contribute to the refraction of the eye - each of the components being inherited independently of the others and possibly transmitted according to different patterns of heredity

17. Contd… Francois cited that low hyperopia can be considered as variations within the normal limits of the binomial distribution and refers to additional studies indicating that these conditions are inherited as dominant characteristics However, hyperopia of +6.00 D and over are inherited either as dominant or recessive characteristics

18. Classification On the basis of degree of Hyperopia On the basis of clinical appearance By accommodative stages

19. Degree of Hyperopia Low Hyperopia: +2.00 D or less Moderate Hyperopia: +2.25 D to +5.00 D High Hyperopia: +5.25 D or more

20. Clinical appearance Simple Hyperopia Pathological Hyperopia Functional Hyperopia

21. Simple hyperopia It is the commonest form and results from normal biological variations in the development of the eyeball It includes axial and curvatural hyperopia Simple hyperopia may be hereditary, where inheritance is usually dominant which may be irregular

22. Pathological hyperopia It results due to either congenital or acquired conditions of the eye which are outside the normal biological variations of the development It includes: Senile hypermetropia Positional hypermetropia Aphakia Consecutive hypermetropia

23. Contd… Senile hyperopia/Acquired hyperopia Curvatural hyperopia: due to decreased curvature of the outer lens fibres developing later in life Index hyperopia: due to acquired cortical sclerosis In youth the index of refraction of the cortex is considerably less than that of the nucleus, and this inequality results in the formation of combination of a central lens surrounded by two converging menisci This results in an increase in the refracting power of the lens as a whole In old age refractive index of the cortex increases. As a result the lens becomes more homogenous and acts as a single lens. Consequently the converging power of the lens as a whole decreases, resulting in index hyperopia

24. Contd… Positional hyperopia may occur due to posterior subluxation of the lens Aphakia is the congenital or acquired absence of the lens Consecutive hyperopia occurs due to surgically overcorrected myopia or pseudophakia with undercorrection

25. Functional hyperopia It results from paralysis of accommodation as seen in patients with third nerve paralysis and internal ophthalmoplegia Internal ophthalmoplegia is often associated with the Miller Fisher syndrome, which constitutes of weak eye muscles, with blurred vision and often drooping eyelids with facial weakness

26. The exact cause of Miller Fisher (Guillain-Barre) syndrome is unknown. However in about 70% cases, a recent infection or surgery serves as a trigger to an autoimmune response. This autoimmune response attacks the peripheral nerves, leading to weakness and a loss of sensation.

27. Accommodative stages Manifested Hyperopia Absolute Hyperopia Facultative Hyperopia Latent Hyperopia

28. Latent v/s Manifest Hyperopia The condition in which all or part of a patient’s hyperopia is compensated for by the tonicity of the ciliary muscle, is known as latent hyperopia The hyperopia which can be revealed in a subjective refraction represents the patient’s manifest hyperopia Total hyperopia = Latent + Manifest Latent Hyperopia can only be revealed in a cycloplegic refraction

29. Contd… As people age and their amplitude of accommodation decreases, latent hyperopia tends to become manifest For this reason some low hyperopes not requiring glasses (and not having enough latent hyperopia to cause symptoms of eyestrain) find that, as amplitude of accommodation decreases with age, glasses are eventually required for clear and comfortable vision

30. Absolute v/s Facultative Hyperopia Absolute Hyperopia is that hyperopia that cannot be compensated for by accommodation The additional dioptres of Hyperopia that can be overcome by accommodation is Facultative Hyperopia Absolute + Facultative = Manifest hyperopia

31. Note: Facultative Hyperopia and Latent Hyperopia must not be confused with. Both apply to a relatively young individual with a reasonable amount of accommodation, but whereas facultative hyperopia can (at will) be compensated for by accommodation, latent hyperopia is the hyperopia that the patient cannot help but compensate for by accommodation as a result of increased tonicity of the ciliary muscle

32. Example: Visual acuity of a patient is 6/18 (OU) unaided, dry retinoscopy values are +4.50 D (OD) and +4.50 D (OS), acceptance is +2.00 D (OD)-6/9 and +2.00 (OS)-6/9, wet retinoscopy using atropine is +6.00 D (OD) and +6.00 D (OS). Find manifest hyperopia, latent hyperopia, absolute hyperopia, facultative hyperopia and total hyperopia

33. Sol n : manifest= +4.50 D latent = +5.00 D – (+4.50 D) = +0.50 D absolute = +2.00 D facultative = +4.50 D –(+2.00 D) = +2.50 D Total = +4.50 D + (+0.50 D) = +5.00 D

34. Progression of Hyperopia Hyperopia does not progress with age (only the AOA reduces which manifests the hyperopia) A child who is born hyperopic shows reduction in hyperopia in early years of age In later stages of life, it is the latent hyperopia that progresses to manifest Later the hyperopic correction acceptance increases in adulthood due to accommodative effort As the age progresses the lens nuclear sclerosis or changes in the lens may further show shift from hyperopia to lesser hyperopia or lesser hyperopia to myopia

35. Figure: Percentages of individuals wearing plus lenses (Redrawn from Refractive status and Motility Defects of Persons 4-74 years, U.S. Department of Health, Education, and welfare, 1978)

36. Note: In their longitudinal study of 300 patients, Grosvenor and Skaetes found that, among patients with 20/20 vision, emmetropic and hyperopic eyes tended to have a hyperopic shift with age as compared with the myopic eyes in their study

37. Symptoms of Hyperopia In hyperopic patients, the symptoms vary depending upon the age of the patient and the degree of refractive error. These can be grouped as under: Asymptomatic: A small amount of refractive error in young patients is usually corrected by mild accommodative effort without producing any symptoms Asthenopic symptoms: These include: Tiredness of eyes Frontal or frontotemporal headache Watering Mild photophobia

38. Contd… Defective vision with asthenopic symptoms Defective vision only The effect of ageing on vision Intermittent sudden blurring of vision Crossed eye symptoms Squinting of eyes

39. Signs of hyperopia Size of the eyeball maybe normal or may appear small as a whole Anterior chamber is comparatively shallow and the angle is narrow Reduced amplitude of accommodation Visual acuity varies with the degree of hyperopia and power of accommodation. In patients with low degree of hyperopia, visual acuity maybe normal Fundus examination reveals a small optic disc which may look more vascular with ill defined margins and even simulate papillitis (pseudopapillitis) A-scan ultrasonography may reveal a short anteroposterior length of the eyeball

40. Note: In a study done by Jonas JB of Department of Ophthalmology, University of Heidelberg, Mannheim, Germany on the topic “optic disc size correlated with refractive error”, a conclusion was found that the optic disc size depends on the refractive error with an increase in highly myopic eyes beyond -8.00 D and a decrease in highly hyperopic eyes beyond +4.00 D

41. PAPILLITIS PSEUDOPAPILLITIS

42. Visual acuity in Hyperopia As compared to an uncorrected Myope-whose distance visual acuity cannot be improved by accommodation-distance visual acuity of an uncorrected Hyperope can be significantly improved by accommodation The extent to which a Hyperope’s distance visual acuity can be improved by accommodation is limited only by the Amplitude of Accommodation A young person having 3.00 D of hyperopia and 10.00 D of accommodation will have no difficulty accommodating enough to compensate for the hyperopia and achieve clear vision. However an old person with the same amount of Hyperopia and 2.00 D of accommodation would not be able to compensate fully for the hyperopia and would therefore not have clear distance vision

43. Visual acuity in Hyperopia Near visual acuity in Hyperopia depends on the amount of hyperopia, the amplitude of accommodation and the distance at which reading is attempted Suppose an uncorrected 2.00 D hyperope with 3.00 D of accommodation attempts to read at a distance of 40cm. Because 2.00 D of accommodation will be needed to see clearly at infinity, only 1.00 D is available to focus at a distance of 40cm However, 2.50 D of accommodation is necessary to focus at 40cm the patient lacks 1.50 D of accommodation to accomplish the task, and near vision will be blurred Amplitude of Accommodation = Reciprocal of Near Point of Accommodation

44. Absolute hyperopia (D) Snellen’s visual acuity +0.5 6/9 +0.75 6/12 +1.00 6/12 - 6/18 +1.50 6/24 +2.00 6/24(partial) +2.50 6/36 – 6/60 +3.50 4/60 +4.50 3/60 Table: Estimate of visual acuity in absolute hypermetropia

45. Correction of Hyperopia Correction of hyperopia includes: Optical correction using spectacles Contact lenses Vision therapy Surgical treatment

46. Spectacles Plus (convex) lenses are used to correct hyperopia Spectacles are most comfortable, safe and easy method of correcting hypermetropia Newer high index lenses and aspheric lens designs have reduced the thickness and weight of high plus powered lenses increasing their acceptance

47. Contact lenses Soft or rigid contact lenses are an excellent alternative for some patients who resist wearing spectacles Contact lenses reduce aniseikonia in persons with anisometropia, improving binocularity In patients with accommodative esotropia, contact lenses decrease the accommodative and convergence demands, reducing or eliminating esotropia at near to a greater extent than spectacles

48. Note: In case of Aphakia, a spectacle correction usually results in approximately a 25% image magnification, which can be reduced to about 7% using a contact lens correction. Thus a resultant decrease in field of view occurs with the wear of high plus spectacles. There is another 20% loss of the visual field due to the ring scotoma effect of the high-plus spectacle lens. Magnification also produces a pincushion distortion; patients may complain of difficulty with depth perception, navigating stairs becomes challenging, and vertical edges such as door frames may appear curved and actually appear to change curvature while walking through them

49. Vision therapy High hyperopia and especially accommodative esotropia reduces binocular functions which need to be improved by vision therapy along with optical correction. These may include advices on improving lighting or glare reduction, better postures and visual hygiene should be emphasized on computer terminals Children should be under the supervision of an orthoptist for improvement of binocular functions

50. Refractive surgery In general, refractive surgery for hyperopia is not as effective or reliable as for myopia. However, following procedures are used: Cornea based procedures: Thermal laser keratoplasty (TLK) has been used for low degree of hyperopia. In this technique, 8 laser spots are applied in a ring at the periphery to produce central steepening with mid infrared energy from Thallium-Holmium-Chromium (THC): YAG laser. Regression effect and induced astigmatism are the main problems Hyperopic LASIK is effective in correcting hyperopia upto +4.00 D

51. Refractive surgery Hyperopic PRK using excimer laser has also been tried. Regression effect and prolonged epithelial healing are the main problems encountered Conductive Keratoplasty (CK) is nonablative and nonincisional procedure in which cornea is steepened by collagen shrinkage through the radiofrequency energy applied through a fine tip inserted into the peripheral corneal stroma in a ring pattern. This technique is effective for correcting hyperopia of upto 3.00 D

52. Refractive surgery Lens based procedures: Phakic refractive lens (PRL) or implantable contact lens (ICL) is being considered a surgical option for hyperopia of more than +4.00 D Refractive lens exchange (RLE) is a good option for high hyperopia especially in presbyopic age

53. PRESCRIPTION GUIDELINES Consideration Prescription Age 3-6 years Due to cycloplegic refraction or non cycloplegic (Mohindra) refraction, give a partial prescription, if the power is >/= +3.25 D of spherical equivalent then subtract 0.75 D from the gross retinoscopy >/= +3.50 D in one or more meridian at 1 year of age upwards Sphere: prescribe 1.00 D less than the least hyperopic meridian Cylinder: prescribe half of the astigmatism, if >+2.50 D >+2.50 D at 4 yrs upwards Still give a partial correction for hyperopia; undercorrecting by approx. 1.00 D to 1.50 D, which is the mean hyperopia at this age >/= +1.50 D in the school years without symptoms A full or near full correction maybe given at this age, as emmetropisation has essentially ended

54. PRESCRIPTION GUIDELINES INDICATION PRESCRIPTION Bilateral refractive amblyopia Cycloplegic refraction of +5.00 D or more, full amount or reduce 1.00 D to 2.00 D Accommodative esotropia Give full cycloplegic refraction Accommodative esotropia with amblyopia Cycloplegic refraction of +3.00 D or more, reduce 1.00 D to 2.00 D

55. PRESCRIPTION GUIDELINES Consideration Management Birth to 6 years No compensation, except for strabismus, suppressions, or poor school performance 6 to 20 years No compensations, except for strabismus, suppressions, poor school performance, near asthenopia or acuity loss, prescribe cautiously with liberal cut in plus power 20 to 40 years Compensate for complaints, with moderate cut in plus power for distance, yet full plus compensation for near activity 40 years and up Usually compensate with full plus power with near add for presbyopic compensation Esotropes Fully correct, with a possible near addition Exotropes Partially correct to minimize secondary exo problems;

56. UNCORRECTED HYPEROPIA AND ESOTROPIA When an excessive amount of accommodation is required in uncorrected hyperopia, the visual system has three choices: The visual system may let the letters go out of focus, making reading impossible One eye may turn inward, towards the nose, relieving the eyestrain but causing double vision Single vision may be maintained, but at the cost of a large amount of stress due to the continual unconscious effort to keep the eyes from overconverging and thus avoid diplopia

57. Contd... If the hyperopia has gone uncorrected for a long time, the convex lenses may fail to straighten the eyes: Because the brain receives conflicting information from the eye that is turning inward, resulting in the following: SUPPRESSION of the retinal image of the deviating eye AMBLYOPIA or “dull vision”. If the child’s esotropia is allowed to continue indefinitely, the visual acuity of the turning eye may fail to develop normally Once suppression and amblyopia has occurred, the mere correction of the hyperopia does not necessarily straighten the eyes. However, it is usually possible to improve their coordination by a series of vision therapy sessions

58. References Theodore Grosvenor, Primary Care Optometry, Fifth Edition, Page no. 16, 17, 35, 193 AK Khurana, Theory and practice of Optics and Refraction, Second Edition, Page no. 62-71 Monica Chaudhry, Refraction and Lens Prescription, page no. 42-45, 150-151 Borish’s Clinical Refraction, Page no. 1518, 1652 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC565977/#__ffn_sectitle https://www.ncbi.nlm.nih.gov/m/pubmed/9469564/ https://www.ncbi.nlm.nih.gov/m/pubmed/15734000/ https://www.orthobullets.com/pediatrics/4089/marfan-syndrome http://eyewiki.aao.org/Peters%27_Anomaly

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