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Accidents to the eyes are either perforations of the globe or blunt trauma tothe globe. The degree of visual impairment depends on which structures are injuredor dislocated. Sometimes infections complicate the picture and even more rarely sympatheticophthalmia.
Achromatopsia is either complete (=rod monochromasy) or incomplete achromatopsiain which cone functions are less severely affected, color perception of large colorareas is present although distorted and visual acuity and contrast sensitivity aremoderately decreased. Both the complete and the incomplete form of achromatopsiaare hereditary, non-progressive conditions, not diseases (progressive loss of colorvision due to retinal diseases are dyschromatopsias). Specific features to be evaluatedare: photophobia and CPF type filter lenses, also contact lenses with specific filtration.
Vision loss is usually caused by opportunistic retinal infections that cause irregularloss of visual function.
Albinism is a genetic condition, either autosomal recessive or X-linked. It maybe total or partial or present only as ocular albinism. Developmental anomalies ofoptic pathways are common and cause strabismus. Macular abnormalities cause decreasedvisual acuity and contrast sensitivity, and nystagmus. High refractive errors arecommon, photophobia is marked. The underlying cause is a deficiency of melanin synthesis.
In western world allergic reactions rarely cause visual problems except for temporaryphotophobia during the reactions because the symptoms can be alleviated with medications.In developing countries untreated allergic reactions may lead to corneal oedema andvascularization and thus decrease vision. Allergic reactions should be rememberedwhen ever visually impaired person develops signs of photophobia that have not beena part of the symptoms caused by the basic disorder.
Amblyopia or "lazy eye" is monocular condition of reduced function ofthe central visual field due to suppression. The reason for the image of an eye beingsuppressed may be reduced quality of the image due to opacities in the optic media,unequal refractive errors or strabismus. Amblyopia becomes important in cases whenthe dominant eye is affected by disease or trauma and the person is dependent onthe functions of the amblyopic eye. The central functions can sometimes be trainedstill in adult age if the dominant eye is lost.
Binocular amblyopia is caused by high hyperopia which leads to blurred imageson both retinas when the child cannot overcome hyperopia through accommodation. Thiscan be completely prevented by giving the infants with high hyperopia correctivelenses at the age of 4-6 months.
Aniridia means total or partial absence of the iris. It is either autosomal dominantor autosomal recessive genetic disorder. Some children develop glaucoma and in certainfamilies aniridia is complicated by Wilm's tumor. Because of loss of iris the normalregulation of the amount of light entering the eye, which is usually taken care ofby the pupil, has to be compensated by tinted lenses and by adjusting the lightingconditions. Some children and adults like contact lenses on which the iris structuresare painted for cosmetic purposes and a rather small center opening is left clear.
Anophthalmia means absence of one or both eyeballs.
Aphakia is usually artifactual, due to surgical removal of the lens, because ofcataract. Sometimes lens is absorbed or dislocated into the vitreous cavity (dueto trauma or cataract operation). Aphakia is corrected either by using intraocularlenses, contact lenses or cataract spectacles. Monocular aphakia can be correctedonly by using intraocular lenses or contact lenses except when the person uses theeyes alternatingly. See Cataract.
Arterial occlusions are either those of central retinal artery or one of the brancharteries. Central arterial occlusion, if not treated, leads to blindness, whereasbranch artery occlusion leads to sectorial loss of visual field.
In an astigmatic eye the refractive error is usually caused by the differencesin curvatures of the corneal surface in different meridians. The unequal radii ofthe curvatures cause differences in refractive power in these axis and thereforelines with different directions are in focus at different distances from the retina.E.g. when vertical lines are in focus of the retina, the horizontal lines are infocus either in front of the retina or would be in focus behind the retina, so atthe retinal level they are not in focus. Smaller degrees of astigmatism can be compensatedfor by using the focusing power of the lens: the image is quickly focused first inone and then in the other focal level and a proper image is composed of the two partialimages. With age this becomes more and more difficult and at the same time the requirementsof the image quality increase. This is why astigmatic corrections become more commonat the school age and in working life. Astigmatism quite often changes both in pubertyand after the age of 50-55 when the structure of the lens changes.
Correction of astigmatism is a complicated issue, especially in young children,who may not appreciate the improvement of the central image and are disturbed bythe distortions of image in the periphery of the lens. Persons who use extrafovealviewing may or may not need astigmatic correction related to their oblique viewingangle through the lens and cornea. In each case careful subjective refraction isnecessary and usually possible even in quite young children.
Cataracts are divided into four groups: congenital, juvenile, presenile and senile.Cataract means opacities of the lens in such an amount that they disturb visual functionseither by causing glare or decreasing visual acuity or contrast sensitivity. Sometimesthe most disturbing change is the change in refractive error toward myopia whichmay be more than 10 diopters. Small opacities in the periphery of the lens are commonin quite healthy individuals both as congenital or later acquired changes. Incipientcataract means that the opacities do not prevent visualization of the retina butare already causing some inconvenience. Surgical removal of the cataractous lensis nowadays recommended as soon as cataract starts to interfere with daily functioning.In most cases it is possible to implant an intraocular lens (IOL) to compensate forthe refractive power of the removed lens. If an intraocular lens cannot be used,contact lenses or spectacle corrections are needed for clear image. Aphakic childrenare at risk of developing increased intraocular pressure and are therefore followedup carefully. There is also some increased risk of retinal detachment. Dependingon the technique with which the cataract has been removed, there may or may not betendency of scar tissue to develop on the anterior vitreous surface. When the secondarycataract interferes with a person's functioning, small hole can be made in the scartissue to allow passage of light to the retina. Cataract is still the most commoncause of functional blindness despite major efforts to increase and improve cataractsurgery in developing nations. In western countries there is also quite a numberof unoperated cataracts but in most cases these are the second eye of a patient whoseother eye have been successfully operated.
Central choroidal sclerosis causes macular degeneration because the overlyingretina disappears when choroid degenerates. The whole macular area is devoid of retinaltissue and the sclera is visible through the coarse vascular network. Because ofthe large white area in the optical axis there is quite a lot of scatter of lightinside the eye.
Choroiditis means inflammation in the choroid which may be related to an infectionor to a local immunologic reaction. If choroiditis extends to the retina, it interfereswith that part of visual field. Sometimes peripheral chorioretinal lesions causemacular oedema which decreases central visual functions. One of the most common causesof chorioretinitis is toxoplasmosis. Other common causes are histoplasmosis in certaincountries and tuberculosis.
Choroideremia is an X-linked hereditary degeneration of choroid and retina thatleads to typical atrophic looking eye ground with very little pigment dispersion.Symptoms are very much like symptoms in retinitis pigmentosa with decrease in scotopicvision and constriction of visual fields in the affected males. In the carrier femalessymptoms are slight but usually the carrier state can be recognized from the appearanceof the retina.
Colobomas are caused by closure defects of the inferior sulcus of the eye duringearly foetal life. Coloboma can be at any site of the lower part of the eye, in iris,ciliary body, retina or optic nerve or in all these parts of the eye. Depending onwhich parts of the eye are involved the functional changes vary a lot. Small colobomaof the iris makes the pupil look like an old fashioned keyhole, which gives the nameto this condition, "key hole pupil". Retinal colobomas cause field lossin the upper field. If the retinal coloboma extends to the disc, the posterior wallof the globe is irregular in structure and refractive error becomes very difficultto measure. Quite often the visual function is much better than one could expectfrom the structure of the eye. Therefore careful repeated evaluation of visual functionduring the first years of life is mandatory. Since the refractive error may be veryhigh myopia, corrective lenses and stimulation at near distances are important. Colobomamay be a part of a more extensive disturbance in early development and thereforediagnostic work includes thorough examination for other possible birth defects.
Color deficiency is defined as an inherited condition in which there is a confusioneither in red-green or blue-yellow axis. The red-green defects in either deutan orprotan axis (see Color Vision Manual) are common, in about 8% of males and 0.5% offemales whereas blue-yellow deficiency is very rare. Inherited color deficiency canbe present as an additional feature of a disease related, acquired color vision change.
Conjunctivitis means inflammation of the conjunctiva. It may be an infection causedby bacteria, virus or fungi or an irritation related to chemical or physical factors(e.g. exposure to UV-light), or drying because of exposure (in thyroid disease) andin lagophthalmus (=paralyzed lower eye lid). Conjunctivitis can be also allergic(see Allergic Reactions). Conjunctivitis as such does not cause loss of vision butmay be disturbing and cause photophobia.
Corneal erosion means wound of the corneal surface, usually uninfected and healingrapidly if the surface is covered with ointment or oily medication to prevent theeye lid to adhere to the thin healing epithelium. Healing of the corneal epitheliumis very rapid but during the first few weeks attachment to the underlying tissueis loose so that the thin scar tissue can easily be torn off by rubbing the eye oreven just squeezing the eye lids because of irritation of the eyes by any externalirritating agent or even when laughing or crying.
Recurrent corneal erosion means that the same area of corneal epithelium tendsto break repeatedly, even after several weeks free of symptoms. If the recurrenterosion is in the optical area of cornea it interferes with vision. Even if the erosionis in the more peripheral parts of the cornea, photophobia and tearing are disturbing.
Ulcer means sore, so corneal ulcer means loss of epithelial continuity of thecorneal surface with an infection complicating the situation. The ulcer is oftencaused by a small trauma during which fungi, bacteria, vira or chlamydia can enterthe corneal tissue. Normally the corneal epithelium prevents the entrance. In areaswhere vitamin A deficiency is prevalent, corneal epithelium loses its barrier functionand keratomalacia can develop quickly.
Corneal ulcers may be also complications of the use of contact lenses.
Corneal ulcers require always prompt medical treatment, sometimes surgery to covera large ulcer with conjunctiva to prevent blinding conditions from developing. Anulcer heals with some cloudiness of cornea in that area. If the ulcer is in the opticalarea of the cornea it interferes with vision.
See specific chapter on CVI or Cerebral Visual Disability.
Diabetes causes changes in several parts of the eye in both the juvenile and thematurity onset diabetes. The type and extent of changes are individual and are relatedto both the type of the disease and the quality of the control. The most importantchanges are in the circulation of the retina and iris. There are changes in the capillarywalls of retinal capillaries, the number of mural cells decreases, there is lossalso of epithelial cells leading to acellular closed capillaries. When the cellularstructure of the capillary wall changes, diffusion through the wall changes, largemolecules, including lipids can enter the retinal tissue (exudates). The capillarywall can bulge to form small pouches called microaneurysms or allows microscopicamount of blood to enter the retinal tissue leading to small hemorrhages. Areas withpoor perfusion of the capillary bed become edematous and newly formed vessels maystart growing from the surrounding vasculature. Newformed vessels are fragile andmay cause bleeding both in the retina, on the retinal surface and into the vitreous.
Newformed vessels on the iris tend to interfere with the anterior chamber angleand intraocular pressure leading to neovascular glaucoma.
Cataractous changes of the lens appear at a younger age in diabetics than in non-diabetics.Treatment of cataract is the same as in non-diabetic cataracts, extraction of thecataract.
Severe loss of vision due to diabetes is usually related to macular oedema orretinal detachment; photocoagulation scars also cause loss of visual field and quiteoften interfere with night vision. In diabetes, loss of low contrast vision oftenoccurs earlier than loss of high contrast visual acuity and therefore measurementof contrast sensitivity and also color vision at regular intervals is important.
Diplopia means double vision, i.e. simultaneous perception of a single objectas two. Double vision is usually caused by disturbance in the function of one ofthe six extraocular muscles. When it cannot pull normally, the eye turns toward theopposite direction and eyes cannot be aligned properly. The defective function ofone muscle can be compensated by turning the head. The most common reason for diplopiais circulatory disturbance in the nerve that innervates the abducens muscle (=themuscle pulling the eye toward the side). In young children who have intermittentstrabismus and have not yet lost fusion of the two images, double vision is presentwhen the eye turns into strabismic position. Double vision is very disturbing alsoin an infant's life; the infant may look ataxic or apraxic because not knowing whichimage is related to the object he/she wants to grasp. The infants usually learn toavoid double vision by closing or suppressing one eye. If intermittent strabismusis not treated by glasses, binocularity may be lost and, especially in inward squint(= esotropia), amblyopia may develop in the less preferred eye.
Normally the lens is well centered at the optical axis. If the lens fibers havenot developed normally or there is traumatic loss of lens fibers, the lens may becomedislocated peripherally. Small dislocations cause refractive errors that can be compensatedwith glasses. Large dislocations mean that part of the pupil is aphakic and needsaphakic correction and part of the pupil area may be highly myopic. Diagnosis ofdislocated lenses requires thorough medical examination to rule out Marfan's syndrome,in which aortic complications, rupture of the aortic wall, may develop without anyprior symptoms. There are several other syndromes in which dislocation or subluxationof the lens may occur.
Glaucoma is a group of diseases. The most common type is simplex glaucoma whichmeans open angle glaucoma. The angle of the anterior chamber is open but intraocularpressure is increased, optic nerve fibers are slowly destroyed leading to loss ofvisual field. Angle closure glaucoma means that the anterior chamber angle becomesoccluded. Then intraocular pressure rises rapidly and very high which causes disturbancein perfusion and rapid loss of vision if not treated.
Glaucoma medications cause some problems to vision: miotic drops, like pilocarpine,decrease the size of pupil. If the lens is clear, small pupil improves the imagequality and increases the depth of focus whereas if the lens is cloudy, small pupilmeans increased loss of light and poor quality of image. Glaucoma medications mayhave systemic side effects so they should be looked for in all clients who use medications.
Hemianopia means loss of half of visual field. It is due to disruption of thefunction of optic pathway posterior to chiasma, often between LGN (=lateral geniculatebody) and primary visual cortex. The most common cause is stroke in older clientsand periventricular leucomalacia in infants. The second most common cause is tumor.Depending on the extent of the lesion there may be some function in the subjectivelyblind part of visual field (blind sight). In each hemianoptic client the possibilityof macular sparing is investigated carefully. If macular function is spared, readingmay not be severely disturbed. If the field loss extends to the very center of thevisual field, one may use slightly eccentric viewing; in right sided half field lossone may hold the book upside-down.
Hydrocephalus, enlarged ventricles, develops because of increased intracranialpressure. The pressure can damage the visual pathways or other brain structures involvedwith the use of vision.
Hyperopia (or hypermetropia) means a refractive error in which the refractivepower of the eye is insufficient to bring the image in focus on the retina in restingstate of the eye. The focal point of light rays coming from infinity is behind theretina. Small and even intermediate amounts of hyperopia can be compensated for byaccommodation in young children. Hyperopia in the range of +6-+8 may lead to disturbancein visual functions so that the child does not learn to accommodate, near image isconstantly blurred and the child develops binocular amblyopia.
Keratitis means corneal inflammation which may be an infection as in herpetickeratitis, caused by herpes simplex virus, or allergic or due to exposure to UV-light(keratitis photoelectrica), which actually means numerous small vesicles of the cornealepithelium.
Keratoconus is a cone shaped profile of the cornea instead of the normal morespherical form. It develops in otherwise healthy young adults, who, however, quiteoften have allergic conjunctivitis and may rub their eyes and thus deform the cornealsurface. Secondary keratoconus is well known to develop in children who eye poke.
Keratomalacia means softening and disruption of the cornea due to vitamin A deficiency.The earliest sign of vitamin A deficiency in the eyes is the Bitot's spot which usuallymeans that the child simultaneously has also increased risk of infections so thedetection of this ocular sign may prevent serious general illness.
In infancy there are very few changes in the retinas to be seen in the clinicalexamination but an ERG may show decrease in amplitude and the scotopic ERG may beextinguished. The loss of vision varies from total blindness to moderate visual impairmentin day light. Depending on the type of loss of vision there is either pendular nystagmusor in case of more severe vision loss the eye movements are slowly roving. Amongthe children who seemingly have Leber's Congenital Amaurosis, there is a group ofchildren who have unusual form of complete achromatopsia. They see with their rodsand therefore are dazzled in daylight but can develop useful vision if given properfilter lenses and a possibility of using their vision at low luminance levels.
This is a rapidly progressive disease with recurrent inflammation of the opticnerve leading to optic atrophy in young men. Optic neuritis and optic atrophy causecentral scotoma which in these diseases may become very large. Sometimes there isa minute area of clear vision within the central scotoma. Since the changes oftenstart at the time when the person has an occupation or is getting schooling, repeatedevaluations are necessary whenever the visual situation changes. The care and lowvision services are those of client with progressive, sometimes very rapidly progressivedecrease of vision.
Macular degeneration is either juvenile starting in childhood like Stargard'sdystrophy or senile, of which there are two forms: 1. atrophic or "dry"type and 2. neovascular or "wet" type. The "senile" macular degenerationis usually called age related macular degeneration because it may occur and oftendoes occur without any signs of senility.
Macular function is lost first in small patches that then become confluent, centralvision becomes distorted, visual acuity and contrast sensitivity and color visiondecrease. The atrophic lesion is limited to the macular area and therefore peripheralvisual functions remain normal. In the juvenile forms of macular degenerations andin the neovascular form the changes may involve much larger areas and lead to extensiveloss of visual functions.
Microphthalmia means small eye. The development of the eye has been disturbedby either genetic or environmental factors early during the foetal development. Exceptthe small size of the eye there may be additional developmental abnormalities.
In multiple sclerosis involvement of the visual pathways is common. Inflammationof the optic nerve, retrobulbar neuritis may be very mild and involve only the magnocellularpathway. Then only the low contrast vision and motion perception are affected. Duringan acute phase of the retrobulbar neuritis vision in the central part of the visualfield may be lost quite dramatically but in most cases will return to at least someextent within a few weeks and months. Oculomotor problems are common and may occurwithout involvement of the optic pathways.
Higher degrees of nearsightedness are often complicated with degenerative changesin the macula with loss of visual acuity and changes in the structure of centralvisual field. Often the posterior wall of the eye is irregular so that major partof the retina is less myopic than the foveal area. Therefore a comfortable correctionmay be several diopters less than the correction that gives best distance visualacuity. Many myopia magna individuals have an additional minus lens in their pocketfor checking details or use a telescope in which the additional minus correctionis included. Because of the minification effect of the minus lenses higher minuscorrections usually are a combination of the contact lens and spectacles. Contactlenses are usually fitted to give a comfortable near correction and the spectaclesused for the additional minus for distance correction.
Attentional defect that prevents a person of being aware of part of space aroundor a part of him-/herself is called neglect. It may mean loss of attention in onehalf of the visual field so that the person does not comb hair and does not noticewhether cloths are properly dressed on that side. In children this is often misdiagnosedas half field defect. There is, however, an obvious difference: even when the personturns the eyes so that the nonrecognized limbs are in the functioning visual fieldhalf the person is not aware of them.
Sometimes neglect is confined to visual memory, i.e. the person cannot memorizeand describe one side of a well known place. An example of this was a patient inFlorence who could not memorize the left side of the central square when told todescribe it while visualizing himself as standing at one end of the square, yet coulddescribe it if asked to describe it while visualizing himself standing at the oppositeend of the square. In the latter situation the previously well described right sideof the square (now on the left) became difficult or impossible to memorize.
Nystagmus means involuntary movements of eyes. It is usually bilateral (i.e. inboth eyes) and rather symmetric but may be in just one eye. It is either sensory,caused by impaired central vision or primary motor nystagmus in which sensory functionsare usually only mildly affected. Nystagmus often decreases in a certain eye positionor during convergence. Children learn to use head turn to bring the nystagmus toits minimum amplitude.
Onchocerciasis or river blindness, is a disease caused by onchocerca volvulusmicrofilariae in equatorial Africa and Latin America. The parasites are particularlynumerous in the eyes and the skin of the affected persons leading to inflammationof the anterior eye or retina or optic nerves. The disease is spread by Simuliumfly that lays her eggs in fast flowing rivers, therefore the risk of getting thedisease is greatest near rivers where the fly population is present.
Atrophy means loss of functioning cells. The reason for cell damage may be infection,trauma or increased intraocular pressure. The size of the optic cup is larger thannormal, the color of the optic disc is pale to white and there is corresponding fieldloss measurable in perimetry.
Hypoplasia means underdeveloped and in case of optic nerve results in an opticnerve head or optic disc smaller than normal. The hypoplastic disc is frequentlysurrounded by a dark ring of pigment (=double ring sign). ONH is so often part ofabnormal development of several midline structures, that the condition warrants carefulpediatric investigations.
Increased intracranial pressure causes swelling of the optic disc. The edges ofthe disc are edematous, in fluorescein angiography there is diffusion of the dyefrom the damaged capillaries into the tissue.
Changes and loss of the white matter surrounding the ventricles. Depending onin which area of the ventricle wall the tissue damage has occurred it results inloss of either visual, auditory or motor pathways or a combination of all these changes.
When the ciliary body has been damaged so that formation of intraocular fluidis decreased, the intraocular pressure cannot be kept on normal levels, the pressurebecomes barely measurable, the eye is soft. Depending on the cause of the damageto the ciliary body, loss of vision may vary.
Presbyopia means age related loss of accommodation. The decrease in accommodationcapability starts in the teens at which time the accommodative power may be 15 tonearly 20 diopters. When the accommodative power decreases to 4-3 diopters, the personnotices that he/she no more can bring things close to see them more clearly, thatthe details become blurred. Loss of accommodation power can be compensated with pluslenses.
The upper eye lid has defective function of the levator muscle and the eye lidis therefore drooping. Compensatory head tilt backwards is used by children withbilateral ptosis. Unilateral ptosis may cause amblyopia.
Dysplasia means disturbance in the development of a tissue.
Loss of normal attachment to choroid. The most common cause is a hole in the peripheryof the retina called "tear" through which vitreous fluid gets entrancebehind the retina and retina becomes detached. Most retinal holes are results ofsymptomless degeneration of the peripheral retina, sometimes they are result of eyeor head trauma. As long as macular area is attached, results of detachment surgeryare usually good, after macular detachment often some visual function is lost.
The most important retinal infection causing loss of vision is toxoplasmosis duringfoetal development. Toxoplasma gondi has a peculiar tendency of causing the infectionin the macula resulting in large pigmented scars. Tuberculosis, cytomegalo infectionsand syphilis are more rare causes of vision loss.
Arterial occlusions are either those of central retinal artery or one of the brancharteries. Central arteria occlusion, if not treated immediately, leads to blindness,branch artery occlusion to sectorial loss of visual field.
Vein occlusion may be occlusion of the central retinal vein or one of its branches.Loss of vision is due to retinal oedema and bleeding from the damaged capillaries.Decreased contrast sensitivity may be much more pronounced than loss of visual acuity.
Retinitis pigmentosa is a large group of inherited retinal degenerations. In themost typical form the changes begin in the midperiphery of the retina leading todisturbance of first rods then both rods and cones and therefore changes in nightvision and later development of ring scotoma. In atypical forms the changes may bein just one eye or even in a quadrant of one retina, in other types there is concentricloss of visual field starting from the periphery. (For functional assessment, see"Eyes and Vision").
ROP, previously called retrolental fibroplasia (RFL) means disturbed developmentof retina in premature infants. Treatment with cryo- and laser therapy has decreasedthe severity of visual impairment. There may be simultaneous vision loss due to periventricularleucomalasia without motor involvement.
Malignant tumor of the retina. Vision loss is usually due to changes in the retinaduring radio therapy if the eye was not enucleated.
Retinoschisis means a separation of the different layers of the retina so thatin some cases parts of the inner retina are thin strands in the vitreous. In manycases the only change is a minute wrinkling of the retina in the form of spokes ofa wheel in the macula. In those cases visual acuity is mildly or moderately reducedand the other visual functions may be so normal that the person does not experiencehim/herself visually impaired. Progression may be very slow until 40's-50's.
Total loss of cone function, normal or slightly reduced rod function. Becauseof loss of cone function, rods are not inhibited in day light vision and thereforeare severely over exposed causing photophobia. With proper absorptive filter lensesand side shields visual functions can be greatly improved.
Scotoma means an area of reduced sensitivity in the visual field. Absolute scotomais an area where no responses can be elicited even with strong stimuli. Relativescotoma means that stronger than normal stimuli have to be used in order to elicita response. Scotoma may subjectively be nonvisible, as is the blind spot in a normalvisual field, or it may been seen as a grey or black area.
Strabismus means that the two eyes are not focused on the same object. Strabismusmay be either non-paralytic or paralytic. In paralytic strabismus one or severalof the eye muscles are paralyzed or paretic and therefore the motor functions havebecome abnormal. In non-paralytic strabismus the eyes move normally but the angleof the optic axis of the eyes is abnormal. Strabismus is either inward, esotropia,or outward, exotropia. If strabismus is latent then it is esophoria or exophoria.Vertical strabismus, hypotropia, -phoria is rare.
Perforation of the wall of the eye sometimes leads to development of autoimmunereaction and inflammation of the non-injured eye. With early effective treatmentof perforations sympathetic ophthalmitis has become rare.
Inflammation of the conjunctiva due to trachoma virus. Cicatrix changes in theconjunctiva cause entropium, damage to the corneal surface and vascularization ofthe cornea. Trachoma is still a common cause of childhood blindness in dry tropicalareas.
Inherited sensorineural hearing defect and retinitis pigmentosa. In Usher typeI the person also has balance problems, in Usher type II progression of hearing defectis very slow, in Usher type III progression of hearing impairment is more rapid inthe teens and adulthood.
Uveitis means inflammation of the uvea that consists the choroid, the ciliarybody and the iris. Anterior uveitis is inflammation of the iris and/or ciliary body,posterior uveitis is inflammation of choroid.