An Approach To Night Blindness

AN APPROACH TO NIGHT BLINDNESS : 

AN APPROACH TO NIGHT BLINDNESS Dr Gyanendra Lamichhane Lumbini Eye Institute Bhairahawa,Nepal

Causes of night blindness: : 

Causes of night blindness: Retinitis pigmentosa Choroideremia Gyrate atrophy of choroid and retina Stationary forms of night blindness Vitamin A deficiency Drugs( Hydroxychloroquine, Phenothiazine)

RETINITIS PIGMENTOSA : 

RETINITIS PIGMENTOSA Most frequently seen retinal dystrophy The term "retinitis" pigmentosa -Donders(1855) The term "pigmentary degeneration"-von Graefe(1858) "Pigmentary retinal dystrophy" -appropriate term Pathology Degeneration of retinal neuroepithelium particularly of rods Degeneration of entire retina, RPE, and also choriocapillaris

CLINICAL PRESENTATION: : 

CLINICAL PRESENTATION: Symptmatic onset between age of 5-30 yrs may occur in 4th or 5th decades Symptoms: Difficulty in seeing at night Daily-life handicap Sign Clinical triad- Retinal arteriolar narrowing Bony spicules Optic disc pallor

Clinical Findings : 

Clinical Findings Other Findings: Lens- Opacity , PSCC type Vitreous-Condensations, opacities, cells, PVD Macula- Early broadening or loss of the F. R. Epiretinal membrane changes Pigment epithelial alterations-mottling, bull's eye, atrophy, pigmentation Macular oedema Full thickness holes

CLASSIFICATION OF RP : 

CLASSIFICATION OF RP AD. type AR. type X-linked recessive type Type 1 RP-Diffused loss of rod sensitivity Absent rod ERG Nyctalopia since infancy/childhood Type 2RP-Regional loss of rood and cone function Some recordable rod ERG until late in life Adult onset night blindness

Atypical RP : 

Atypical RP Retinitis punctata albescens Sector RP Unilateral RP Pericentric RP Paravenous Form

Systemic Associations : 

Systemic Associations Bassen-Kornzweig syndrome Refsum's disease Usher's syndrome Laurance-Moon and Bardet Biedl syndrome Kearns-Sayre syndrome

INVESTIGATIONS: : 

INVESTIGATIONS: Dark Adaptometry Delayed cone-rod break Elevated final threshold ;final rod threshold>3 log units Abnormally prolonged recovery to final threshold

INVESTIGATIONS: : 

INVESTIGATIONS: Visual Fields Mid peripheral scotomas complete ring scotoma Peripheral visual field loss-preferentially superior Central tunnel vision remains

INVESTIGATIONS: : 

INVESTIGATIONS: ERG Marked reduction or loss of both rod and cone signals (rod predominates) Reduction of a and b waves b waves prolonged in time and diminished in amplitude

Genetic Considerations : 

Genetic Considerations Rhodopsin gene mutation-in 30% of A.D.type Mutation in peripherin/RDS-4-6% of A.D.type Mutation in gene for ROM1protein or for cGMPphosphodiesterase enzyme

CHOROIDEREMIA : 

CHOROIDEREMIA X-linked recessive disease Genetic defect in small segment of Xq Affected male develops night blindness in 1st or 2nd decade Young patients- normal visual acuity min. increase in dark adaptation threshold reduced ERG amplitudes withdelayed b-wave implicit time. full V.F. granularity and pigmentation in RPE in the periphery

CHOROIDEREMIA : 

CHOROIDEREMIA Adulthood Increases dark adaptation thresholds constricted V.F. ERG-undetectable extensive choroidal atrophy and clumped pigments in the periphery Carriers(females) normal visual acuity normal dark adapted rod threshold normal ERG patchy depigmentation of RPE and coarse granularity

GYRATE ATROPHY OF CHOROID AND RETINA : 

GYRATE ATROPHY OF CHOROID AND RETINA A.R. disease Defect in enzyme ornithine aminotransferase(OAT) Mutation of the gene (in chrom.10) for OAT Develop nightblindness during 1st decade Progressive loss of visual acuity(6/60 or < by 40Yrs) and V.F. later on

Contd…… : 

Contd…… Fundus finding: Paving stone like areas of atrophy of RPE and choriocapillaris Scalloped border at junction of normal and abnormal RPE in the periphery or sometimes near the disc Biochemical Abnormality: Elevation of plasma ornithine level(10 to20 folds) Hyperornithinuria Lack of OAT in extracts of cultured skin fibroblast and lymphocyte Reports of seizures despite normal neurological system

CSNB : 

CSNB Life long stable abnormality of scotpic vision having early onset Subtypes: CSNB with normal fundus CSNB with abnormal fundus CSNB with normal fundus X-linked AD AR

CNBS : 

CNBS CSNB with normal fundus X-linked –commonest genetic defect- locus Xp11, mutation in rhodopsin gene Defect is lies in the failure of communication between proximal ends of photorecetors and bipolar cells some pts. Do not c/o nyctalopia( way of life) Nystagmus decrease Va or myopia Range of Va- Normal to 6/60

Investigations : 

Investigations Dark adaptometry curve: 2-3 log units above normal ERG: negative ERG( Schubert- Bornschein form) photopic ERG – decrease amplitude, but normal wave form

CSNB : 

CSNB CSNB with abnormal fundus Fundus Albipunctatus (AR) Oguchi’s Disease (AR) Mizuo’s phenomenon

Vitamin A – Night Blindness : 

Vitamin A – Night Blindness Primary cause of childhood blindness( 1981 Xerophthalmia in Nepal) One of the earliest signs of vit. A deficiency is NB( not always) One of the function of Vit. A is it takes part in the visual cycle – Rhodopsin- rods- Dark adaptation Causes- low intake, malabsorption due to intestinal diseases, liver diseases, diarrhea, malnourished mother Congenital & Acquired T/T- Vit. A supplementation: Cap. Vit. A 200000iu 1st and 2nd day then 2wks(>1yr) pregnant woman- 10000IU for 15 (after 1st trimester)

Approach to NB : 

Approach to NB Taking History ( complaints) Night blindness (How do they present to us?) Progressive (RP) Stationary (CSNB) Sudden( paraneoplastic process) Age of onset – imp. Younger (x-linked RP, CSNB)

Contd….. : 

Contd….. 2. Visual loss : Gradual , progressive Age of onset Visual field constriction: peripheral or central How can they present to us?

Medical History : 

Medical History Operations ( Intestinal surgeries, removal of polydactyly) Liver diseases Use of medicine- Hydroxychloroquine or phenothiazine Hearing status( RP, Usher’s Syndrome,choroideremia, Refsum’s) Mental retardation( BBS,LMS) Renal disease (BBS) Heart disease (KSS, Refsum’s)

Family History : 

Family History Any NB in past 3 consecutive generation (Dominant RP) Anyone in the family affected by retinal degeneration Consanguinity

Personal History : 

Personal History Children- premature, milestone development Socio-economic status Excessive alcohol intake ( liver damage)

General & Systemic Examination : 

General & Systemic Examination General Status : wt. loss- vit A deficiency truncal obesity –(Bardet-Biedl Syndrome) Systemic evaluation: CVS- Kearn-Sayre Syndrome( ECG- Heart block) P/A- Colostomy, surgical scars ENT- Hearing loss ( Usher’s, RP, Choroideremia) NS – Mental retardation( Bardet-Biedl Syndrome, Gyrate Atrophy Choroidermia, LMS) ,Spastic paraplegia (LMS) Urogenital- hypogenitalism( Bardet- Biedl syndrome) Musculo-Skeletal –Polydatyly (Bardet- Biedl syndrome, LMS), muscle weakness(Gyrate Atrophy), deformity (choroideremia) Skin – Melanoma ( paraneoplastic cause)

Ocular Evaluation : 

Ocular Evaluation Visual Acuity EOM ( external ophthalmoplegia- KSS, Bassen-Kornzweig, Refsum’s) Lid ( ptosis- KSS) Lens – PSCC- ( RP, Choroideremia, Gyrate Atrophy) Vitreous – fibrillar changes ( Choroideremia), PVD( Gyrate Atrophy) Fundus-Normal or Abnormal Normal fundus ( CSNB) Refractive Status Myopia- ( RP,choroideremia, Gyrate Atrophy) High Myopia ( CSNB) Astigmatism-( RP)

Fundus Changes in cases of NB : 

Fundus Changes in cases of NB RP Choroideremia Gyrate atrophy

Fundus Changes : 

Fundus Changes Oguchi

Investigations : 

Investigations Visual fields( All) Dark Adaptometry ERG( all) Color vision( later stages of RP) Biochemical: Ser. Vit A level Ser. Lipoprotien( Bassen – Kornzweig syndrome) Ser. Phytanic acid level ( Refsum’s) Ser. Ornithine level( Gyrate Atrophy)

Management : 

Management Staging ( current VA, VF, dark adaptation, color vision, rod-cone ERG) Give devices for maximizing remaining vision Monitoring Disease progression- 2yrs.-VF,ERG,Va Counseling – Genetic + Vocational Medical T/T: Vit. A, Acetazolimide, Docosahexanoic acid(DHA)-trial( RP) Vit A, K, E( Bassen- Kornzweig) Vit B6 ( Gyrate Atrophy)

Summary : 

Summary Main aim – establish Dx. Counseling Visual Aids Regular FU Evaluation of close relative